Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

Dave,
I'm not sure that all of you guys on this list are aware of the fact 
that the US has introduced metric units since a long time.

In 1866 Congress voted for the metric system, and in 1894 again 
administration passed bills in that direction. Only in 1975, President 
Gerald Ford signed the Metric Conversion Act which, however, nobody 
seems to take notice of. People just didn't want or were too lazy. 
Nowadays, the US together with other important countries as Liberia and 
Birma are the only ones not using the metric system in the world (look 
at the world map at 
http://de.wikipedia.org/wiki/Metrisches_Einheitensystem).

Regards
Peter

dave schrieb:
> Some places decided that they could increase the effective price by 
> 10-20% by going metric because the customer wasn't smart enough to
> do the conversion. Ha! That crashed quickly. So much for greed.
> I do believe that if we (US) had used metric  on signs for the 
> interstate hwy system and provided incentives for selling gasoline and 
> diesel using liters
> we'd be metric today. Instead we have a mixed system where international 
> companies, eg. aerospace and automotive are metric and almost everything 
> else is english/imperial.
> I once had a GM manufactured car that was part metric and part english; 
> now that was a pain. Logic and politics are rarely in the same room.
>
> Dave
>
>   


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Re: [Emc-users] Brushless Servo Selection?

[dave]

On 06/16/2012 03:21 PM, andy pugh wrote:
> On 16 June 2012 21:25, Peter Blodow  wrote:
>
>>> Except that hecto and centi are _not_ prefixes in the SI system.
>> Yes they are. Hekto-, deka-, deci- and centi- (100, 10, 1/10, 1/100
>> rsp.) are the only ones with the decimal exponents not being multiples
>> of three,
> Wikipedia seems to agree. I was certainly taught that it was improper
> to use those prefixes though.
>
Usage really depends on the field. I routinely used Kg, g., mg, ug. for 
weight and L, mL, uL for volumes. However, take a look at your latest 
blood chemistry.
Units like mg/dL, U/L (units/liter), mmol/L., are routinely used: and 
then it gets worse K/uL (white blood cells), M/uL (red blood cells), fL 
(mean cell volume), pg ( no volume given),
% (hematocrit), Change those units and you will confuse every medical 
doctor out there...not something you want to do.

Dave
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Re: [Emc-users] Brushless Servo Selection?

[dave]

On 06/16/2012 12:52 PM, Kent A. Reed wrote:
> On 6/16/2012 2:54 PM, andy pugh wrote:
>> On 16 June 2012 18:48, Dave  wrote:
> I suspect real estate was also to be a holdout, hell, nobody around here
>>> has a clue what a hectar is, not even me.<<
>>>
>>> I think that Hectars are english also, as well as fathoms, etc.
>> No, the Hectare is metric.
>>
>> An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
>> is the area of a square 100m on a side.
>> (1 million square metres to the Are, 10,000m^2 to the hectare.)
>>
> Real estate is all about land records. Even in the relatively young US,
> land records now stretch back 300 years. No way anybody is going to be
> in a hurry to convert them to some newfangled system of units. GPS is no
> panacea. Almost no one's land deed, and certainly not mine, is described
> in terms that are easily confirmed by GPS survey, and even if I
> resurveyed my property I'd have to convince all my adjoining neighbors
> to go along as well as the county-record office before I could use the
> new measures in a sale of my property.  Taint a cheap proposition even
> if everyone is being reasonable about it, and how often are people
> reasonable about land? Things are changing in land management , more
> because of the spread of GIS than anything else, but they are changing
> very slowly considering the technologies involved were settled decades ago.
>
> Standards, including units of measure, are intimately tied to commerce;
> hence my former employer, NIST, nee NBS, is in the US Department of
> Commerce.
>
> There have been least three official attempts at metrification in the
> USA in my lifetime, several of which NBS played a role in. None really
> took root (I exclude engineers and scientists) although many items on
> the shelves of stores I frequent are now marked in both "English" and
> "metric" units. Simplistically, I think it's because export of goods and
> services accounts for little more than 10 percent of our gross domestic
> product. That's a little tail on a big dog.
>
> This is a people problem that is not unique to the US. Look at the UK.
> Even though export accounts for some 30 percent of its GDP I know from
> firsthand experience that there is still a sizable resistance to SI. In
> neither the US nor the UK has legislation and its implementing
> regulations been completely successful. Lots of trade will give those
> who have the ability to change a monetary incentive to do so and lots of
> time will allow those who can't change to die away.
>
> Standards are intimately tied to agreements as well.
> http://en.wikipedia.org/wiki/Kilogram gives a nice sampling of the work
> that has been going into reaching international agreement on the
> redefinition of the kilogram.
>
> Regards,
> Kent
I've had some discussions with county people about gps. Apparently in 
the Eastern states agreement is pretty good. A park district just 
acquired land adjacent to ours on Anderson Is.
(south puget sound). The property line moved 6 to 10 feet east and this 
was supposedly done with high accuracy gps. There is a well established 
reference point less than a mi (as the crow flies) from the survey area 
so they had  something decent to tie in to.

I had to laugh at a friend of mine (his business was Ag) who was 
visiting relatives in Austria. I ask how he did with the metric system 
and he replied," Not bad ... as soon as I figured out
that a Kg of cabbage was about this much (using hands to explain) I was OK.

Dave
>
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Re: [Emc-users] Brushless Servo Selection?

[dave]

On 06/16/2012 09:41 AM, gene heskett wrote:
> On Saturday, June 16, 2012 12:31:47 PM Peter Blodow did opine:
>
>> Dave,
>> funny thing is that European lathes in those days you were describing,
>> many still working today,  were equipped with inch lead screws, so that
>> in order to cut mm threads they have to use a 127 teeth gear in the gear
>> case to drive the lead screw. This way, our industry wanted to become
>> compatible with the British and American manufacturers for export
>> And although we are using metric units here in Germany since the late
>> 1880ies, we still buy heating and water pipes, fittings etc. in inch
>> measures. When I sometimes bring my timber to be cut to our local
>> sawmill, I specify 3/4 inch or one inch boards to be made out of it,
>> although they will be measured as 20 or 25 mm boards.
>> By the way, how come that in this mailing list everybody speaks in
>> inches - you were writing about the metric revolution?
>>
>> Peter
>>
> Peter, I was all on that hay ride for as long as it lasted.  But when the
> gas stations that first put in pumps that measured liters made note that
> their monthly usage pumped into the customers tanks dropped to 10% because
> folks would just drive on down the street where they could buy gas by the
> gallon, a unit they had used all their lives, that effect brought the
> metric conversion of the US to a screeching halt.  The rest of the system
> did go metric, but that today is entirely the effect of all the
> manufacturing having been exported.  Had they put dual displays in the gas
> pumps for a few years, so folks could see at a glance what they were
> paying, they might have been able to let the gallons displays gradually
> fail, but some numbed nuts bean counter apparently wouldn't consider that
> idea.  Instead, we took very careful aim and shot ourselves in both feet.
>
> I suspect real estate was also to be a holdout, hell, nobody around here
> has a clue what a hectar is, not even me.
>
>> Dave schrieb:
>>> I was in engineering college from 76 to 81 and remember some
>>> discussion about this.   Fortunately there was not too much to
>>> discuss
>>> as they had already decided that SI was the way to go and we had
>>> recently selected "new" books.   At the same time the "metric"
>>> revolution was in full swing and they were changing out all of their
>>> machine tools in the school shop so they
>>> would all be metric.   They were removing manual machines that were
>>> setup in inches and replacing them with machines setup in millimeters.
>>> Many of the machines were old so I was happy to see them go and be
>>> replaced with new machines.
>>> The school was very unique in that they encouraged students to use the
>>> machines and the facilities after hours.  They had a shop supervisor
>>> who was paid to stay late most weekday nights.  Even the garage was
>>> available, so we could put our cars on the lifts to do repairs and
>>> modifications.   When I wasn't chasing girls, I "lived" at school.
>>>   :-)
>>>
>>> Dave
Some places decided that they could increase the effective price by 
10-20% by going metric because the customer wasn't smart enough to
do the conversion. Ha! That crashed quickly. So much for greed.
I do believe that if we (US) had used metric  on signs for the 
interstate hwy system and provided incentives for selling gasoline and 
diesel using liters
we'd be metric today. Instead we have a mixed system where international 
companies, eg. aerospace and automotive are metric and almost everything 
else is english/imperial.
I once had a GM manufactured car that was part metric and part english; 
now that was a pain. Logic and politics are rarely in the same room.

Dave

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>
> Cheers, Gene

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Re: [Emc-users] Brushless Servo Selection?

[Jon Elson]

Todd Zuercher wrote:
> I think I have found the motors I would like to use. 
> http://www.ebay.com/itm/ElectroCraft-XBR-2910-Nema34-Brushless-AC-Servo-
> Motors-w-Encoders-CNC-/221048834843?pt=LH_DefaultDomain_0&hash=item33778
> 98b1b
>
> Now I need to figure out what drives I would like to use and the power
> supply.
>
> How much would a 4 axis setup from Pico Systems run?
>   
What is the voltage rating of these motors?  If they are high-voltage 
motors, then
running them on my drives will force you to reduced speeds (0which may 
turn out
OK).  If they are rated for up to 120 V AC, then you can get full speed 
out of them.

So, you'd need a universal PWM controller, $250.
The drives are $150 per axis.
That is most of it.  You can add a power switch and braking module for $50,
and a spindle DAC to control a spindle drive, also $50.

Are you going to the CNC Workshop in Ann Arbor later this week?

Jon

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 18 June 2012 22:51, Todd Zuercher  wrote:
> I think I have found the motors I would like to use.
> http://www.ebay.com/itm/ElectroCraft-XBR-2910-Nema34-Brushless-AC-Servo-
> Motors-w-Encoders-CNC-/221048834843?pt=LH_DefaultDomain_0&hash=item33778
> 98b1b

Do you have a spec? Torque / voltage / current?

-- 
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If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Brushless Servo Selection?

[Todd Zuercher]

I think I have found the motors I would like to use. 
http://www.ebay.com/itm/ElectroCraft-XBR-2910-Nema34-Brushless-AC-Servo-
Motors-w-Encoders-CNC-/221048834843?pt=LH_DefaultDomain_0&hash=item33778
98b1b

Now I need to figure out what drives I would like to use and the power
supply.

How much would a 4 axis setup from Pico Systems run?

Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street 
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031



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Phone:  330-828-2105
E-mail: to...@pgrahamdunn.com
630 Henry St.
Dalton, OH 44618
www.pgrahamdunn.com

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Re: [Emc-users] Brushless Servo Selection?

[Jon Elson]

Todd Zuercher wrote:
> Trying to get this thread back on topic since it was hijacked by the metric 
> system.
>
> To run one of these Keling motors how big would the motor cabling need to be? 
>  Will it have to be rated for 30 amps?  That’s pretty big wire.  Or would it 
> only need to be rated for the continual current?
>
>   
Yes, just the continuous current should be fine.  Where are you going to
get a 30A motor drive?
> Are there any other inexpensive brushless motor options, preferably higher 
> voltage/lower current?
>   
IMTT USA has some nice 85mm motors made by Wantai.
They have a rear shaft, but it is taken up by their Hall sensor.  If you
removed that and used a 6-channel encoder, or put the encoder somewhere
else on the machine, these work fine.  They sell them for use on pumps,
but I have verified they work well in positioning applications, too.

Jon

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Re: [Emc-users] Brushless Servo Selection?

[Todd Zuercher]

Trying to get this thread back on topic since it was hijacked by the metric 
system.

To run one of these Keling motors how big would the motor cabling need to be?  
Will it have to be rated for 30 amps?  That’s pretty big wire.  Or would it 
only need to be rated for the continual current?

Are there any other inexpensive brushless motor options, preferably higher 
voltage/lower current?



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E-mail: to...@pgrahamdunn.com
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www.pgrahamdunn.com
-Original Message-
From: Kirk Wallace [mailto:kwall...@wallacecompany.com] 
Sent: Friday, June 15, 2012 1:41 PM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Brushless Servo Selection?

On Fri, 2012-06-15 at 10:53 +0100, andy pugh wrote:
> On 15 June 2012 06:58, Viesturs Lācis  wrote:
> 
> > Unfortunately it requires relatively larger power supply with higher
> > current output.
> 
> This is a problem with motors like the Keling ones, with a 48V rated voltage.
> It is far simpler to make a 300V PSU than a 48V one. Simply rectifying
> mains voltage into a big capacitor makes a PSU that the 8i20 is happy
> with.
> 
> Those Keling motors have a 500V / 1 min rating. I don't know if that
> meas that they can run indefinitley on a 300V PWM (with a 48V
> "average" or not). In the US I suppose a rectified-mains PSU would be
> around 150V which sounds more reasonable. (only 3x rated voltage, and
> it is conventional to run steppers at that sort of overvoltage)
> 

48 Volts or rather -48 Volts DC is common for telephone equipment, so
there may be cheap supplies available, if one knows where to look.

Building an Antek supply shouldn't be too expensive, but I haven't
checked prices recently.
http://www.antekinc.com/index.php 
http://www.antekinc.com/gview.php 

One could make a transformer for the needed voltage, like these guys
did.
http://mackys.livejournal.com/838591.html 

Brushed motors (and drives) might be cheaper and universal motors are
usually wound for mains voltage. If they can be modified for permanent
magnets, universal motors could be handy.
http://www.supermagnetman.net/index.php?cPath=37&page=3 

For most of us, brushes wear well enough to not be a maintenance
problem. Scrap yards should have a large supply of vacuum cleaner motors
from people that don't know how to replace a rubber belt.

Another thing I haven't had time to look into is using a Delon doubler
when one needs higher voltage than what is at hand.
http://en.wikipedia.org/wiki/File:Bridge_voltage_doubler.svg 
http://en.wikipedia.org/wiki/Voltage_doubler 


-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA





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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Sunday, June 17, 2012 02:01:11 PM Dave did opine:

> On 6/16/2012 2:54 PM, andy pugh wrote:
> > On 16 June 2012 18:48, Dave  wrote:
>  I suspect real estate was also to be a holdout, hell, nobody around
>  here
> >> 
> >> has a clue what a hectar is, not even me.<<
> >> 
> >> I think that Hectars are english also, as well as fathoms, etc.
> > 
> > No, the Hectare is metric.
> > 
> > An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
> > is the area of a square 100m on a side.
> > (1 million square metres to the Are, 10,000m^2 to the hectare.)
> > 
>  >>A metric unit of square measure, equal to 100 ares (2.471 acres or
> 
> 10,000 square meters).
> Well obviously I didn't know what a Hectare was.
> Ironically my house lot is very close to a Hectare at 2.4 acres (in
> "flyover country"), so now I know I can relate to a Hectare.  :-)

You've got lots of room for more roofing then.  I'm about out. :(
> 
> Dave
> 
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Cheers, Gene
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Re: [Emc-users] Brushless Servo Selection?

[Dave]

On 6/16/2012 2:54 PM, andy pugh wrote:
> On 16 June 2012 18:48, Dave  wrote:
>
 I suspect real estate was also to be a holdout, hell, nobody around here
  
>> has a clue what a hectar is, not even me.<<
>>
>> I think that Hectars are english also, as well as fathoms, etc.
>>  
> No, the Hectare is metric.
>
> An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
> is the area of a square 100m on a side.
> (1 million square metres to the Are, 10,000m^2 to the hectare.)
>
>

 >>A metric unit of square measure, equal to 100 ares (2.471 acres or 
10,000 square meters).
Well obviously I didn't know what a Hectare was.
Ironically my house lot is very close to a Hectare at 2.4 acres (in 
"flyover country"), so now I know I can relate to a Hectare.  :-)

Dave

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 17 June 2012 09:09, Steve Blackmore  wrote:

> Pipe threads are Imperial Units - BSP (British Standard Pipe) and have a
> Whitworth thread form.

Whitworth thread has a 55 degree thread angle. This is better than a
60 degree angle, but harder to draw.
(Whitworth calculated that 55 degrees gave the best combination of
clamping force and self-locking)
Most of the world's thread standards compromise to make things easier
for the draughtsman and tool grinder.
BA threads are 47.5 degrees. I don't know why. However BA is
interesting as the sizes are mathematically derived on a series of
equations.
http://en.wikipedia.org/wiki/British_Association_screw_threads


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Re: [Emc-users] Brushless Servo Selection?

[Steve Blackmore]

On Sat, 16 Jun 2012 23:03:44 +0300, you wrote:

>2012/6/16 andy pugh :
>>
>> You are quite right, I don't know how I got that wrong.
>> Except that hecto and centi are _not_ prefixes in the SI system.
>>
>
>Could be, I do not know for sure...
>
>BTW the metric vs imperial systems and UK being somewhere inbetween
>(litres from metric system and miles from imperial), I just remembered
>one interesting moment from a metrology class:
>In whole mainland Europe screw threads are metric, pipe threads are in
>imperial units. Which does not make much of a sense to me, why would
>they be separated, but then professor mentioned that pipe threads in
>UK are not imperial (I _think_ that screw threads are imperial in
>UK)...
>So I think that pipe thread in UK has to be metric, which makes me
>think that English people are doing this on purpose :))

Pipe threads are Imperial Units - BSP (British Standard Pipe) and have a
Whitworth thread form.

Have a read up on Joseph Whitworth  - He displayed a machine in 1855
that could measure to an accuracy of one millionth of an inch. He was
also the guy who defined a standard thread 1841 to aid the speed of
manufacture. 

Steve Blackmore
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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Saturday, June 16, 2012 06:46:59 PM andy pugh did opine:

> On 16 June 2012 18:48, Dave  wrote:
> >>>I suspect real estate was also to be a holdout, hell, nobody around
> >>>here
> > 
> > has a clue what a hectar is, not even me.<<
> > 
> > I think that Hectars are english also, as well as fathoms, etc.
> 
> No, the Hectare is metric.
> 
> An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
> is the area of a square 100m on a side.
> (1 million square metres to the Are, 10,000m^2 to the hectare.)

I hope you aren't having a snap quiz on this tomorrow.  Cause I likely 
won't remember it even that long. :(

Cheers, Gene
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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Saturday, June 16, 2012 06:44:09 PM Dave did opine:

> >>I suspect real estate was also to be a holdout, hell, nobody around
> >>here
> 
> has a clue what a hectar is, not even me.<<
> 
> I think that Hectars are english also, as well as fathoms, etc.
> 
> You need to get your head wrapped around square meters.   (Good luck
> with that!)  I don't have a meter stick, but I have several yard
> sticks. So how can you estimate realestate in square meters if you
> don't even have a meter stick??
> 
> But I have two feet and my shoes are right at 13 inches.. so if I walk
> toe to toe .  ;-)  (I do that more than I care to admit.)
> 
And in my prime, my pace even for my short legs, often put me at 91 or 92 
paces from end zone to end zone of a football field.  But not recently, the 
hip joints out voted me.

> Dave
> 
> On 6/16/2012 12:41 PM, gene heskett wrote:
> > On Saturday, June 16, 2012 12:31:47 PM Peter Blodow did opine:
> >> Dave,
> >> funny thing is that European lathes in those days you were
> >> describing, many still working today,  were equipped with inch lead
> >> screws, so that in order to cut mm threads they have to use a 127
> >> teeth gear in the gear case to drive the lead screw. This way, our
> >> industry wanted to become compatible with the British and American
> >> manufacturers for export And although we are using metric units
> >> here in Germany since the late 1880ies, we still buy heating and
> >> water pipes, fittings etc. in inch measures. When I sometimes
> >> bring my timber to be cut to our local sawmill, I specify 3/4 inch
> >> or one inch boards to be made out of it, although they will be
> >> measured as 20 or 25 mm boards.
> >> By the way, how come that in this mailing list everybody speaks in
> >> inches - you were writing about the metric revolution?
> >> 
> >> Peter
> > 
> > Peter, I was all on that hay ride for as long as it lasted.  But when
> > the gas stations that first put in pumps that measured liters made
> > note that their monthly usage pumped into the customers tanks dropped
> > to 10% because folks would just drive on down the street where they
> > could buy gas by the gallon, a unit they had used all their lives,
> > that effect brought the metric conversion of the US to a screeching
> > halt.  The rest of the system did go metric, but that today is
> > entirely the effect of all the manufacturing having been exported. 
> > Had they put dual displays in the gas pumps for a few years, so folks
> > could see at a glance what they were paying, they might have been
> > able to let the gallons displays gradually fail, but some numbed nuts
> > bean counter apparently wouldn't consider that idea.  Instead, we
> > took very careful aim and shot ourselves in both feet.
> > 
> > I suspect real estate was also to be a holdout, hell, nobody around
> > here has a clue what a hectar is, not even me.
> > 
> >> Dave schrieb:
> >>> I was in engineering college from 76 to 81 and remember some
> >>> discussion about this.   Fortunately there was not too much to
> >>> discuss
> >>> as they had already decided that SI was the way to go and we had
> >>> recently selected "new" books.   At the same time the "metric"
> >>> revolution was in full swing and they were changing out all of their
> >>> machine tools in the school shop so they
> >>> would all be metric.   They were removing manual machines that were
> >>> setup in inches and replacing them with machines setup in
> >>> millimeters. Many of the machines were old so I was happy to see
> >>> them go and be replaced with new machines.
> >>> The school was very unique in that they encouraged students to use
> >>> the machines and the facilities after hours.  They had a shop
> >>> supervisor who was paid to stay late most weekday nights.  Even the
> >>> garage was available, so we could put our cars on the lifts to do
> >>> repairs and modifications.   When I wasn't chasing girls, I "lived"
> >>> at school.
> >>> 
> >>>   :-)
> >>> 
> >>> Dave
> >> 
> >> -
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> > 
> > Cheers, Gene
> 
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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Saturday, June 16, 2012 06:40:41 PM Mike Bennett did opine:

> Gene
> 
> They solved the litres issue in the UK but making it illegal to sell
> most things in anything but metric units.  However we still measure
> distance in miles, so what units should we be working out our fuel
> economy?  Miles per litre?
> 
> At least we can still buy beer in pints ( 20oz ones of course :-) )
> 
> Mike
Chuckle.  So that explains Fosters, which comes in a huge can.  I used to 
like it, but that was before carrying a glucose meter in my hip pocket.
 
> 
> On 16 Jun 2012, at 17:41, gene heskett  wrote:
> > Peter, I was all on that hay ride for as long as it lasted.  But when
> > the gas stations that first put in pumps that measured liters made
> > note that their monthly usage pumped into the customers tanks dropped
> > to 10% because folks would just drive on down the street where they
> > could buy gas by the gallon, a unit they had used all their lives,
> > that effect brought the metric conversion of the US to a screeching
> > halt.  The rest of the system did go metric, but that today is
> > entirely the effect of all the manufacturing having been exported. 
> > Had they put dual displays in the gas pumps for a few years, so folks
> > could see at a glance what they were paying, they might have been
> > able to let the gallons displays gradually fail, but some numbed nuts
> > bean counter apparently wouldn't consider that idea.  Instead, we
> > took very careful aim and shot ourselves in both feet.
> > 
> > I suspect real estate was also to be a holdout, hell, nobody around
> > here has a clue what a hectar is, not even me.
> 
> 
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Cheers, Gene
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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

Viesturs,
don't confuse US and British units although they are both called 
imperial units (since when do Americans care about emperors?) - they are 
not necessarily the same as you come to details. Screws can be a lot 
different, for example. I have an old English combined circular wood saw 
and table router with thread holes in the table where US screws don't 
fit. British imperial gallons are different from US gallons. 
Furthermore, there are American metric screws that won't fit into 
European nuts of the same specifications because the radii of the 
thread's edges are different - it's all a whole mess as long as there 
are no efforts of unification. In this respect, we are living in an era 
not much different from the middle ages because every country wants to 
protect their products from other manufacturers instead of making joint 
efforts to compete only in quality and price of the optimal products.

British pipe threads are based on inch standard and compatible with all 
other countries' pipes and fittings, imperial or not.

Peter

Viesturs La-cis schrieb:
> 2012/6/16 andy pugh :
>   
>> You are quite right, I don't know how I got that wrong.
>> Except that hecto and centi are _not_ prefixes in the SI system.
>>
>> 
>
> Could be, I do not know for sure...
>
> BTW the metric vs imperial systems and UK being somewhere inbetween
> (litres from metric system and miles from imperial), I just remembered
> one interesting moment from a metrology class:
> In whole mainland Europe screw threads are metric, pipe threads are in
> imperial units. Which does not make much of a sense to me, why would
> they be separated, but then professor mentioned that pipe threads in
> UK are not imperial (I _think_ that screw threads are imperial in
> UK)...
> So I think that pipe thread in UK has to be metric, which makes me
> think that English people are doing this on purpose :))
>
>   


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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 21:25, Peter Blodow  wrote:

>> Except that hecto and centi are _not_ prefixes in the SI system.

> Yes they are. Hekto-, deka-, deci- and centi- (100, 10, 1/10, 1/100
> rsp.) are the only ones with the decimal exponents not being multiples
> of three,

Wikipedia seems to agree. I was certainly taught that it was improper
to use those prefixes though.

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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

andy pugh schrieb:
>
> You are quite right, I don't know how I got that wrong.
> Except that hecto and centi are _not_ prefixes in the SI system.
>
>   
Yes they are. Hekto-, deka-, deci- and centi- (100, 10, 1/10, 1/100 
rsp.) are the only ones with the decimal exponents not being multiples 
of three, but just the same widely used whenever SI-units are used at 
all, probably the most frequently used ones of all of them.

Example: women's clothes are measured in cm, beer barrels and all beer 
production are measured in hectoliters. Want more?

Peter.

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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/16 andy pugh :
>
> You are quite right, I don't know how I got that wrong.
> Except that hecto and centi are _not_ prefixes in the SI system.
>

Could be, I do not know for sure...

BTW the metric vs imperial systems and UK being somewhere inbetween
(litres from metric system and miles from imperial), I just remembered
one interesting moment from a metrology class:
In whole mainland Europe screw threads are metric, pipe threads are in
imperial units. Which does not make much of a sense to me, why would
they be separated, but then professor mentioned that pipe threads in
UK are not imperial (I _think_ that screw threads are imperial in
UK)...
So I think that pipe thread in UK has to be metric, which makes me
think that English people are doing this on purpose :))

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Re: [Emc-users] Brushless Servo Selection?

[Kent A. Reed]

On 6/16/2012 2:54 PM, andy pugh wrote:
> On 16 June 2012 18:48, Dave  wrote:
 I suspect real estate was also to be a holdout, hell, nobody around here
>> has a clue what a hectar is, not even me.<<
>>
>> I think that Hectars are english also, as well as fathoms, etc.
> No, the Hectare is metric.
>
> An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
> is the area of a square 100m on a side.
> (1 million square metres to the Are, 10,000m^2 to the hectare.)
>

Real estate is all about land records. Even in the relatively young US, 
land records now stretch back 300 years. No way anybody is going to be 
in a hurry to convert them to some newfangled system of units. GPS is no 
panacea. Almost no one's land deed, and certainly not mine, is described 
in terms that are easily confirmed by GPS survey, and even if I 
resurveyed my property I'd have to convince all my adjoining neighbors 
to go along as well as the county-record office before I could use the 
new measures in a sale of my property.  Taint a cheap proposition even 
if everyone is being reasonable about it, and how often are people 
reasonable about land? Things are changing in land management , more 
because of the spread of GIS than anything else, but they are changing 
very slowly considering the technologies involved were settled decades ago.

Standards, including units of measure, are intimately tied to commerce; 
hence my former employer, NIST, nee NBS, is in the US Department of 
Commerce.

There have been least three official attempts at metrification in the 
USA in my lifetime, several of which NBS played a role in. None really 
took root (I exclude engineers and scientists) although many items on 
the shelves of stores I frequent are now marked in both "English" and 
"metric" units. Simplistically, I think it's because export of goods and 
services accounts for little more than 10 percent of our gross domestic 
product. That's a little tail on a big dog.

This is a people problem that is not unique to the US. Look at the UK. 
Even though export accounts for some 30 percent of its GDP I know from 
firsthand experience that there is still a sizable resistance to SI. In 
neither the US nor the UK has legislation and its implementing 
regulations been completely successful. Lots of trade will give those 
who have the ability to change a monetary incentive to do so and lots of 
time will allow those who can't change to die away.

Standards are intimately tied to agreements as well. 
http://en.wikipedia.org/wiki/Kilogram gives a nice sampling of the work 
that has been going into reaching international agreement on the 
redefinition of the kilogram.

Regards,
Kent


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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

> I know this stuff, I have a physics degree.
>   
Sorry, didn't mean to insult you.
> In fact many years ago the NPL invited me along to a colloquium
> discussing how best to re-define the kilogram.
> (Because it is currently based on a lump of platinum-iridium, not on
> any "portable" physical constants. In fact the master kilogram and the
> sub-standards are all drifting in different directions, and that is
> causing some concern. I think the current plan is to use a perfect
> sphere of silicon, 
>   
...which my collegues at the PTB (German Federal Physical-Technologiocal 
Institute) at Braunschweig have been doing for the last, say, 15 years. 
Filing single atoms from a sphere, puuuh...

Peter


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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 20:02, Viesturs Lācis  wrote:

> 1/100 is centi - centimeter is 1/100 of meter.
> Hectolitre is 100 litres, so I guess hectare is 100 ares, which means
> that 1 is area of 10x10 m.

You are quite right, I don't know how I got that wrong.
Except that hecto and centi are _not_ prefixes in the SI system.

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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/16 John Prentice :
>
>>
>> Fruit machines??   What is a fruit machine?
>>
>> Do you know what we call them in the US?
>>
>> Dave
>
>
> Slot Machine or One arm bandit I think.

The same that look like Mach3 :))

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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/16 andy pugh :
> On 16 June 2012 18:48, Dave  wrote:
I suspect real estate was also to be a holdout, hell, nobody around here
>> has a clue what a hectar is, not even me.<<
>>
>> I think that Hectars are english also, as well as fathoms, etc.
>
> No, the Hectare is metric.
>
> An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
> is the area of a square 100m on a side.
> (1 million square metres to the Are, 10,000m^2 to the hectare.)

1/100 is centi - centimeter is 1/100 of meter.
Hectolitre is 100 litres, so I guess hectare is 100 ares, which means
that 1 is area of 10x10 m.

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 18:48, Dave  wrote:
>>>I suspect real estate was also to be a holdout, hell, nobody around here
> has a clue what a hectar is, not even me.<<
>
> I think that Hectars are english also, as well as fathoms, etc.

No, the Hectare is metric.

An Are is an area 1km x 1km. A Hectare is 1/100 of that. So, a hectare
is the area of a square 100m on a side.
(1 million square metres to the Are, 10,000m^2 to the hectare.)

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Re: [Emc-users] Brushless Servo Selection?

[Dave]

On 6/16/2012 1:45 PM, andy pugh wrote:
> On 16 June 2012 18:05, Jon Elson  wrote:
>
>
>> Well, in the US, the metric revolution came and went.  Certain
>> industries (aircraft
>> manufacturing and auto manufacturing) have gone totally metric
>>  
> Not entirely.
> Part of our ECU code is being written by Ford in the USA, to plug into
> the code written in France, the UK and Germany by the supplier and the
> designer.
> Imagine my annoyance to find that the very first thing that the US
> code did was convert the incoming temperature signal to Fahrenheit,
> then convert it back again at the output port.
>
> Considering that the numbers are all scaled representations of the
> real values as 16-bit ints this makes absolutely no sense whatsoever.
>
>

That is really funny.

The problem is that us Americans can't think in anything but 
Fahrenheit!   ;-)

Dave

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Re: [Emc-users] Brushless Servo Selection?

[Dave]

I remember Italy was km/hr years ago.  I thought the UK was in km/hr also.

So at this point, I guess it is a safe bet that the UK will not be going 
to the Euro anytime soon?   ;-)

Dave

On 6/16/2012 1:08 PM, Mike Bennett wrote:
> Gene
>
> They solved the litres issue in the UK but making it illegal to sell most 
> things in anything but metric units.  However we still measure distance in 
> miles, so what units should we be working out our fuel economy?  Miles per 
> litre?
>
> At least we can still buy beer in pints ( 20oz ones of course :-) )
>
> Mike
>
>
>
> On 16 Jun 2012, at 17:41, gene heskett  wrote:
>
>
>>>
>> Peter, I was all on that hay ride for as long as it lasted.  But when the
>> gas stations that first put in pumps that measured liters made note that
>> their monthly usage pumped into the customers tanks dropped to 10% because
>> folks would just drive on down the street where they could buy gas by the
>> gallon, a unit they had used all their lives, that effect brought the
>> metric conversion of the US to a screeching halt.  The rest of the system
>> did go metric, but that today is entirely the effect of all the
>> manufacturing having been exported.  Had they put dual displays in the gas
>> pumps for a few years, so folks could see at a glance what they were
>> paying, they might have been able to let the gallons displays gradually
>> fail, but some numbed nuts bean counter apparently wouldn't consider that
>> idea.  Instead, we took very careful aim and shot ourselves in both feet.
>>
>> I suspect real estate was also to be a holdout, hell, nobody around here
>> has a clue what a hectar is, not even me.
>>
>>  
>>>
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Re: [Emc-users] Brushless Servo Selection?

[Dave]

>>I suspect real estate was also to be a holdout, hell, nobody around here
has a clue what a hectar is, not even me.<<

I think that Hectars are english also, as well as fathoms, etc.

You need to get your head wrapped around square meters.   (Good luck with 
that!)  I don't have a meter stick, but I have several yard sticks.
So how can you estimate realestate in square meters if you don't even have a 
meter stick??

But I have two feet and my shoes are right at 13 inches.. so if I walk toe to 
toe .  ;-)  (I do that more than I care to admit.)

Dave



On 6/16/2012 12:41 PM, gene heskett wrote:
> On Saturday, June 16, 2012 12:31:47 PM Peter Blodow did opine:
>
>
>> Dave,
>> funny thing is that European lathes in those days you were describing,
>> many still working today,  were equipped with inch lead screws, so that
>> in order to cut mm threads they have to use a 127 teeth gear in the gear
>> case to drive the lead screw. This way, our industry wanted to become
>> compatible with the British and American manufacturers for export
>> And although we are using metric units here in Germany since the late
>> 1880ies, we still buy heating and water pipes, fittings etc. in inch
>> measures. When I sometimes bring my timber to be cut to our local
>> sawmill, I specify 3/4 inch or one inch boards to be made out of it,
>> although they will be measured as 20 or 25 mm boards.
>> By the way, how come that in this mailing list everybody speaks in
>> inches - you were writing about the metric revolution?
>>
>> Peter
>>
>>  
> Peter, I was all on that hay ride for as long as it lasted.  But when the
> gas stations that first put in pumps that measured liters made note that
> their monthly usage pumped into the customers tanks dropped to 10% because
> folks would just drive on down the street where they could buy gas by the
> gallon, a unit they had used all their lives, that effect brought the
> metric conversion of the US to a screeching halt.  The rest of the system
> did go metric, but that today is entirely the effect of all the
> manufacturing having been exported.  Had they put dual displays in the gas
> pumps for a few years, so folks could see at a glance what they were
> paying, they might have been able to let the gallons displays gradually
> fail, but some numbed nuts bean counter apparently wouldn't consider that
> idea.  Instead, we took very careful aim and shot ourselves in both feet.
>
> I suspect real estate was also to be a holdout, hell, nobody around here
> has a clue what a hectar is, not even me.
>
>
>> Dave schrieb:
>>  
>>> I was in engineering college from 76 to 81 and remember some
>>> discussion about this.   Fortunately there was not too much to
>>> discuss
>>> as they had already decided that SI was the way to go and we had
>>> recently selected "new" books.   At the same time the "metric"
>>> revolution was in full swing and they were changing out all of their
>>> machine tools in the school shop so they
>>> would all be metric.   They were removing manual machines that were
>>> setup in inches and replacing them with machines setup in millimeters.
>>> Many of the machines were old so I was happy to see them go and be
>>> replaced with new machines.
>>> The school was very unique in that they encouraged students to use the
>>> machines and the facilities after hours.  They had a shop supervisor
>>> who was paid to stay late most weekday nights.  Even the garage was
>>> available, so we could put our cars on the lifts to do repairs and
>>> modifications.   When I wasn't chasing girls, I "lived" at school.
>>>   :-)
>>>
>>> Dave
>>>
>> 
>> -- Live Security Virtual Conference
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>> latest in malware threats.
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>>  
>
> Cheers, Gene
>


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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 18:05, Jon Elson  wrote:

> Well, in the US, the metric revolution came and went.  Certain
> industries (aircraft
> manufacturing and auto manufacturing) have gone totally metric

Not entirely.
Part of our ECU code is being written by Ford in the USA, to plug into
the code written in France, the UK and Germany by the supplier and the
designer.
Imagine my annoyance to find that the very first thing that the US
code did was convert the incoming temperature signal to Fahrenheit,
then convert it back again at the output port.

Considering that the numbers are all scaled representations of the
real values as 16-bit ints this makes absolutely no sense whatsoever.

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Re: [Emc-users] Brushless Servo Selection?

[Mike Bennett]

Gene

They solved the litres issue in the UK but making it illegal to sell most 
things in anything but metric units.  However we still measure distance in 
miles, so what units should we be working out our fuel economy?  Miles per 
litre?

At least we can still buy beer in pints ( 20oz ones of course :-) )

Mike



On 16 Jun 2012, at 17:41, gene heskett  wrote:

>> 
> Peter, I was all on that hay ride for as long as it lasted.  But when the 
> gas stations that first put in pumps that measured liters made note that 
> their monthly usage pumped into the customers tanks dropped to 10% because 
> folks would just drive on down the street where they could buy gas by the 
> gallon, a unit they had used all their lives, that effect brought the 
> metric conversion of the US to a screeching halt.  The rest of the system 
> did go metric, but that today is entirely the effect of all the 
> manufacturing having been exported.  Had they put dual displays in the gas 
> pumps for a few years, so folks could see at a glance what they were 
> paying, they might have been able to let the gallons displays gradually 
> fail, but some numbed nuts bean counter apparently wouldn't consider that 
> idea.  Instead, we took very careful aim and shot ourselves in both feet.
> 
> I suspect real estate was also to be a holdout, hell, nobody around here 
> has a clue what a hectar is, not even me.
> 
>> 

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Re: [Emc-users] Brushless Servo Selection?

[Jon Elson]

Peter Blodow wrote:
> By the way, how come that in this mailing list everybody speaks in 
> inches - you were writing about the metric revolution?
>   
Well, in the US, the metric revolution came and went.  Certain 
industries (aircraft
manufacturing and auto manufacturing) have gone totally metric, but must 
other
stuff has not.  We had traffic signs in km and km/h for a while, but 
then they all
got pulled out and we went back to miles and MPH.  They are only somewhat
teaching our kids the metric system, at least until high school 
chemistry and
physics classes.

Even our Chinese-liaison PCB manufacturer wants the design files in inch 
units,
they then convert to mm before sending the designs to China for 
manufacturing.

When my boss designs some scientific apparatus in mm and hands the 
drawing to
our shop, they dutifully convert the whole drawing to inches before 
making the
parts.

Thanks goodness the local hardware store has a rack of boxes of metric 
fasteners,
so when I need something I can get them.

Jon

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Re: [Emc-users] Brushless Servo Selection?

[Dave]

On 6/16/2012 12:16 PM, gene heskett wrote:
> On Saturday, June 16, 2012 12:14:55 PM Eric Keller did opine:
>
>
>> On Sat, Jun 16, 2012 at 9:31 AM, Dave  wrote:
>>  
>>> The school was very unique in that they encouraged students to use the
>>> machines and the facilities after hours.  They had a shop supervisor
>>> who was paid to stay late most weekday nights.  Even the garage was
>>> available, so we could put our cars on the lifts to do repairs and
>>> modifications.   When I wasn't chasing girls, I "lived" at school.
>>>   :-)
>>>
>>> Dave
>>>
>> I expect those days are over everywhere now due to a tragic accident
>> where a Yale student had a fatal incident involving long hair and a
>> lathe. Around here, students have full access to a very nice shop, but
>> they have to have a funding source to use it.  Deep pockets aren't a
>> funding source, they have to be spending money from a school budget.
>> After the Yale incident, they required us to tell the safety office
>> about any rotating machinery we had in our labs.  I'm pretty
>> disappointed about this whole situation, a mechanical engineering
>> school of any merit should have student shops.
>> Eric
>>  
> When will the friggin lawyers understand that you can't save stupid from
> himself?
>
>

They already understand that.   But since they can still make loads of $ 
from idiots doing stupid things, why stop?

Remember the lady that sued McDonalds for having the coffee too hot!

Now all of our McDonalds coffee is just above cool.   :-(  And the women 
and the lawyers made some serious cash.

Dave


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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Saturday, June 16, 2012 12:31:47 PM Peter Blodow did opine:

> Dave,
> funny thing is that European lathes in those days you were describing,
> many still working today,  were equipped with inch lead screws, so that
> in order to cut mm threads they have to use a 127 teeth gear in the gear
> case to drive the lead screw. This way, our industry wanted to become
> compatible with the British and American manufacturers for export
> And although we are using metric units here in Germany since the late
> 1880ies, we still buy heating and water pipes, fittings etc. in inch
> measures. When I sometimes bring my timber to be cut to our local
> sawmill, I specify 3/4 inch or one inch boards to be made out of it,
> although they will be measured as 20 or 25 mm boards.
> By the way, how come that in this mailing list everybody speaks in
> inches - you were writing about the metric revolution?
> 
> Peter
> 
Peter, I was all on that hay ride for as long as it lasted.  But when the 
gas stations that first put in pumps that measured liters made note that 
their monthly usage pumped into the customers tanks dropped to 10% because 
folks would just drive on down the street where they could buy gas by the 
gallon, a unit they had used all their lives, that effect brought the 
metric conversion of the US to a screeching halt.  The rest of the system 
did go metric, but that today is entirely the effect of all the 
manufacturing having been exported.  Had they put dual displays in the gas 
pumps for a few years, so folks could see at a glance what they were 
paying, they might have been able to let the gallons displays gradually 
fail, but some numbed nuts bean counter apparently wouldn't consider that 
idea.  Instead, we took very careful aim and shot ourselves in both feet.

I suspect real estate was also to be a holdout, hell, nobody around here 
has a clue what a hectar is, not even me.
 
> Dave schrieb:
> > I was in engineering college from 76 to 81 and remember some
> > discussion about this.   Fortunately there was not too much to
> > discuss
> > as they had already decided that SI was the way to go and we had
> > recently selected "new" books.   At the same time the "metric"
> > revolution was in full swing and they were changing out all of their
> > machine tools in the school shop so they
> > would all be metric.   They were removing manual machines that were
> > setup in inches and replacing them with machines setup in millimeters.
> > Many of the machines were old so I was happy to see them go and be
> > replaced with new machines.
> > The school was very unique in that they encouraged students to use the
> > machines and the facilities after hours.  They had a shop supervisor
> > who was paid to stay late most weekday nights.  Even the garage was
> > available, so we could put our cars on the lifts to do repairs and
> > modifications.   When I wasn't chasing girls, I "lived" at school.   
> >  :-)
> > 
> > Dave
> 
> 
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Cheers, Gene
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
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Re: [Emc-users] Brushless Servo Selection?

[Dave]

>>By the way, how come that in this mailing list everybody speaks in
inches - you were writing about the metric revolution?<<

That is the really goofy thing.. the end result was that we are now about half 
and half, english and metric.

After the big metric push back in the late 70's, the car companies went fully 
metric by about the mid to late 80's, but many US made goods are still english.

In my tool chest I have a full set of english and metric sockets which gets 
quite bulky.

The said, if I want to buy english nuts and bolts, I can buy them by them in 
bulk pound (weight measure) in grades 2-8 at a local tractor/farm equipment 
supply store.

If I want to buy metric bolts and nuts locally I have to either buy them from 
an industrial supply store (limited hours) or buy them one at a time at a price 
which can be 3-4 times the bulk price of similar english fasteners.

So the use of english fasteners in the US is reinforced by the availability of 
cheap and available english fasteners.   Ironically most of those fasteners are 
made in Asia or China.

The metric system has some issues..   Buying a 2x4 which is 10 feet long and 
specifying that in millimeters seems crazy.  Pipe fittings would be ok for 
diameter but if I want to but a piece of 2" pipe which is 21 feet long, 
specifying 51 mm in diameter and 6.x meters long seems totally counter 
intuitive.  I guess the advantage is that fractions become non-existent which 
would be a big improvement.

Dave



On 6/16/2012 12:13 PM, Peter Blodow wrote:
> Dave,
> funny thing is that European lathes in those days you were describing,
> many still working today,  were equipped with inch lead screws, so that
> in order to cut mm threads they have to use a 127 teeth gear in the gear
> case to drive the lead screw. This way, our industry wanted to become
> compatible with the British and American manufacturers for export
> And although we are using metric units here in Germany since the late
> 1880ies, we still buy heating and water pipes, fittings etc. in inch
> measures. When I sometimes bring my timber to be cut to our local
> sawmill, I specify 3/4 inch or one inch boards to be made out of it,
> although they will be measured as 20 or 25 mm boards.
> By the way, how come that in this mailing list everybody speaks in
> inches - you were writing about the metric revolution?
>
> Peter
>
>
> Dave schrieb:
>
>> I was in engineering college from 76 to 81 and remember some discussion
>> about this.   Fortunately there was not too much to discuss
>> as they had already decided that SI was the way to go and we had
>> recently selected "new" books.   At the same time the "metric"
>> revolution was in full swing and they were changing out all of their
>> machine tools in the school shop so they
>> would all be metric.   They were removing manual machines that were
>> setup in inches and replacing them with machines setup in millimeters.
>> Many of the machines were old so I was happy to see them go and be
>> replaced with new machines.
>> The school was very unique in that they encouraged students to use the
>> machines and the facilities after hours.  They had a shop supervisor who
>> was paid to stay late most weekday nights.  Even the garage was
>> available, so we could put our cars on the lifts to do repairs and
>> modifications.   When I wasn't chasing girls, I "lived" at school. :-)
>>
>> Dave
>>
>>  
>
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>


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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 17:01, Peter Blodow  wrote:
> Andy,
> 1 Pa = 1 N/sq. meter, a very impractical unit.

I know this stuff, I have a physics degree.
In fact many years ago the NPL invited me along to a colloquium
discussing how best to re-define the kilogram.
(Because it is currently based on a lump of platinum-iridium, not on
any "portable" physical constants. In fact the master kilogram and the
sub-standards are all drifting in different directions, and that is
causing some concern. I think the current plan is to use a perfect
sphere of silicon, and then relate the kg back to the meter (which can
be re-built from the wavelength of a particular light source). The NPL
were looking at using a rotating Watt Balance at the time)

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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Saturday, June 16, 2012 12:27:40 PM andy pugh did opine:

> On 15 June 2012 18:40, Kirk Wallace  wrote:
> > 48 Volts or rather -48 Volts DC is common for telephone equipment, so
> > there may be cheap supplies available, if one knows where to look.
> 
> Very cheap indeed are these "fruit machine" power supplies:
> http://www.ebay.co.uk/itm/261031048815
> With 10A at 50V they look like a potentially very useful CNC supply.

20 UKP + 12 ukp postage?  Needs 230 vac?  I think I'll pass.

Cheers, Gene
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My web page: 
audophile, n:
Someone who listens to the equipment instead of the music.

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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

You can't save anybody from himself, but I understand that nobody will 
be made responsible for the stupid killing themselves. This is the 
consequence of today's "holy law" that nowadays nothing can happen 
without someone being responsible (even if nobody really is). Makes a 
lot of money for the lawyers.

Peter

gene heskett schrieb:
> On Saturday, June 16, 2012 12:14:55 PM Eric Keller did opine:
>   
> When will the friggin lawyers understand that you can't save stupid from 
> himself?
>   


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Re: [Emc-users] Brushless Servo Selection?

[gene heskett]

On Saturday, June 16, 2012 12:14:55 PM Eric Keller did opine:

> On Sat, Jun 16, 2012 at 9:31 AM, Dave  wrote:
> > The school was very unique in that they encouraged students to use the
> > machines and the facilities after hours.  They had a shop supervisor
> > who was paid to stay late most weekday nights.  Even the garage was
> > available, so we could put our cars on the lifts to do repairs and
> > modifications.   When I wasn't chasing girls, I "lived" at school.   
> >  :-)
> > 
> > Dave
> 
> I expect those days are over everywhere now due to a tragic accident
> where a Yale student had a fatal incident involving long hair and a
> lathe. Around here, students have full access to a very nice shop, but
> they have to have a funding source to use it.  Deep pockets aren't a
> funding source, they have to be spending money from a school budget. 
> After the Yale incident, they required us to tell the safety office
> about any rotating machinery we had in our labs.  I'm pretty
> disappointed about this whole situation, a mechanical engineering
> school of any merit should have student shops.
> Eric

When will the friggin lawyers understand that you can't save stupid from 
himself?

> 
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> threat landscape has changed and how IT managers can respond.
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Cheers, Gene
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
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A nonsexual friendship with a member of the opposite sex.
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Accelerated
   Culture"

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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

Dave,
funny thing is that European lathes in those days you were describing, 
many still working today,  were equipped with inch lead screws, so that 
in order to cut mm threads they have to use a 127 teeth gear in the gear 
case to drive the lead screw. This way, our industry wanted to become 
compatible with the British and American manufacturers for export
And although we are using metric units here in Germany since the late 
1880ies, we still buy heating and water pipes, fittings etc. in inch 
measures. When I sometimes bring my timber to be cut to our local 
sawmill, I specify 3/4 inch or one inch boards to be made out of it, 
although they will be measured as 20 or 25 mm boards.
By the way, how come that in this mailing list everybody speaks in 
inches - you were writing about the metric revolution?

Peter


Dave schrieb:
> I was in engineering college from 76 to 81 and remember some discussion 
> about this.   Fortunately there was not too much to discuss
> as they had already decided that SI was the way to go and we had 
> recently selected "new" books.   At the same time the "metric" 
> revolution was in full swing and they were changing out all of their 
> machine tools in the school shop so they
> would all be metric.   They were removing manual machines that were 
> setup in inches and replacing them with machines setup in millimeters.  
> Many of the machines were old so I was happy to see them go and be 
> replaced with new machines.
> The school was very unique in that they encouraged students to use the 
> machines and the facilities after hours.  They had a shop supervisor who 
> was paid to stay late most weekday nights.  Even the garage was 
> available, so we could put our cars on the lifts to do repairs and 
> modifications.   When I wasn't chasing girls, I "lived" at school. :-)
>
> Dave
>   


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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

Andy,
1 Pa = 1 N/sq. meter, a very impractical unit. Therefore, the "bar" as 
the most commonly used pressure unit of today, not a SI unit, is only 
accepted as an exception to be near the previously used "atmosphere" = 1 
kp/sq.cm.
1 hPa (hectoPascal) = 100 Pa (greek: hekaton = hundred). The heck with it.
1 bar = 100 000 Pa = 1.02 kp/sq.cm, so 1 mbar = 1.02 hPa.
The lenght of a "1 meter pendulum" giving exactly one second is about 
0.994  m, a bare coincidence. The meter was first defined as 1/40 000 of 
the earth's circumference and later on by the length of the 
platimum-iridium specimen in Paris. The factor of 9.81 is owed to the 
earth's a acceleration of a falling piece of mass measured to be g = 
9.81 m/s squared, purely accidental.

Greetings
Peter

andy pugh schrieb:
> There is a similar situation with the engine controllers I work on,
> where there is a tendency to use heck Pascals (hPa) which are
> coincidentally almost exactly the same as millibars.
> I do think that this is purely a happy coincidence, as the Pascal
> depends purely on the definitions of the kilogram and meter, with no
> reference to atmospheric constants.
> I think that the kg to Newton correspondence (9.81) might be less
> accidental, being vaguely linked to the original definition of the
> meter as the length of a "seconds pendulum"
>
>   


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Re: [Emc-users] Brushless Servo Selection?

[John Prentice]

>
> Fruit machines??   What is a fruit machine?
>
> Do you know what we call them in the US?
>
> Dave


Slot Machine or One arm bandit I think.

Fruit machine is from graphics commonly used on the rotating drums.

I note the supplies are multi-output switchers. The cross-regulation between 
different outputs might be a problem

John Prentice 


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Re: [Emc-users] Brushless Servo Selection?

[Dave]

On 6/16/2012 9:46 AM, Eric Keller wrote:
> On Sat, Jun 16, 2012 at 9:31 AM, Dave  wrote:
>
>
>> The school was very unique in that they encouraged students to use the
>> machines and the facilities after hours.  They had a shop supervisor who
>> was paid to stay late most weekday nights.  Even the garage was
>> available, so we could put our cars on the lifts to do repairs and
>> modifications.   When I wasn't chasing girls, I "lived" at school. :-)
>>
>> Dave
>>
>>  
> I expect those days are over everywhere now due to a tragic accident where
> a Yale student had a fatal incident involving long hair and a lathe.
> Around here, students have full access to a very nice shop, but they have
> to have a funding source to use it.  Deep pockets aren't a funding source,
> they have to be spending money from a school budget.  After the Yale
> incident, they required us to tell the safety office about any rotating
> machinery we had in our labs.  I'm pretty disappointed about this whole
> situation, a mechanical engineering school of any merit should have student
> shops.
> Eric
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When I was in school they were pushing really hard to get women into the 
program plus back in those days some of the guys had fairly long hair 
also (even I had a lot more hair then than I do now!)

Shop safety was very important.  If you didn't have safety classes and 
your hair tied back they wouldn't let you close to the machines.  We had 
to check in with the guy running the shop at the time to get cutters, 
bits, etc.
Ties (we actually wore them sometimes) were not allowed around 
machines.   The unfortunate fact is that stuff happens, and people 
sometimes die.  They will get over that,  but it might take a while 
unfortunately.
Administrators seem to think that they can eliminate any chance of 
people getting hurt - but it is not possible.

Machinery can be dangerous.I've been around a few industrial 
accidents where people have been killed.  In hindsight they are always 
preventable.  But people sometimes do the wrong things.

 >>a mechanical engineering school of any merit should have student

shops.

I agree.  If they eliminate it and another school does not, then they will be 
at a disadvantage.

Dave

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Re: [Emc-users] Brushless Servo Selection?

[Dave]

On 6/16/2012 11:02 AM, andy pugh wrote:
> On 15 June 2012 18:40, Kirk Wallace  wrote:
>
>
>> 48 Volts or rather -48 Volts DC is common for telephone equipment, so
>> there may be cheap supplies available, if one knows where to look.
>>  
> Very cheap indeed are these "fruit machine" power supplies:
> http://www.ebay.co.uk/itm/261031048815
> With 10A at 50V they look like a potentially very useful CNC supply.
>
>

Fruit machines??   What is a fruit machine?

Do you know what we call them in the US?

Dave

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 15 June 2012 18:40, Kirk Wallace  wrote:

> 48 Volts or rather -48 Volts DC is common for telephone equipment, so
> there may be cheap supplies available, if one knows where to look.

Very cheap indeed are these "fruit machine" power supplies:
http://www.ebay.co.uk/itm/261031048815
With 10A at 50V they look like a potentially very useful CNC supply.

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 08:22, Peter Blodow  wrote:

> To express angular momentum, we have to multiply force by the length of
> the lever, i.e. one meter. So we arrive at the unit DNm = 10 Nm ^= 1
> kpm, and the world is in almost perfect order again.

There is a similar situation with the engine controllers I work on,
where there is a tendency to use heck Pascals (hPa) which are
coincidentally almost exactly the same as millibars.
I do think that this is purely a happy coincidence, as the Pascal
depends purely on the definitions of the kilogram and meter, with no
reference to atmospheric constants.
I think that the kg to Newton correspondence (9.81) might be less
accidental, being vaguely linked to the original definition of the
meter as the length of a "seconds pendulum"

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 14:46, Eric Keller  wrote:

>  a mechanical engineering school of any merit should have student
> shops.

We had a machine shop course as part of my Physics degree. The theory
was that we were likely to be having experimental rigs built, and
having some concept of machinability would be handy.

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Re: [Emc-users] Brushless Servo Selection?

[Eric Keller]

On Sat, Jun 16, 2012 at 9:31 AM, Dave  wrote:

>
> The school was very unique in that they encouraged students to use the
> machines and the facilities after hours.  They had a shop supervisor who
> was paid to stay late most weekday nights.  Even the garage was
> available, so we could put our cars on the lifts to do repairs and
> modifications.   When I wasn't chasing girls, I "lived" at school. :-)
>
> Dave
>
I expect those days are over everywhere now due to a tragic accident where
a Yale student had a fatal incident involving long hair and a lathe.
Around here, students have full access to a very nice shop, but they have
to have a funding source to use it.  Deep pockets aren't a funding source,
they have to be spending money from a school budget.  After the Yale
incident, they required us to tell the safety office about any rotating
machinery we had in our labs.  I'm pretty disappointed about this whole
situation, a mechanical engineering school of any merit should have student
shops.
Eric
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Re: [Emc-users] Brushless Servo Selection?

[Dave]

I was in engineering college from 76 to 81 and remember some discussion 
about this.   Fortunately there was not too much to discuss
as they had already decided that SI was the way to go and we had 
recently selected "new" books.   At the same time the "metric" 
revolution was in full swing and they were changing out all of their 
machine tools in the school shop so they
would all be metric.   They were removing manual machines that were 
setup in inches and replacing them with machines setup in millimeters.  
Many of the machines were old so I was happy to see them go and be 
replaced with new machines.
The school was very unique in that they encouraged students to use the 
machines and the facilities after hours.  They had a shop supervisor who 
was paid to stay late most weekday nights.  Even the garage was 
available, so we could put our cars on the lifts to do repairs and 
modifications.   When I wasn't chasing girls, I "lived" at school. :-)

Dave




On 6/16/2012 3:22 AM, Peter Blodow wrote:
> Andy,
> way back in my school time, curriculum makers detected that mass and
> force are different things. Before, forces were expressed in mass units,
> i.e., kilogramms (greek: chilioi = thousand, gramma = weight), and
> sometimes called kilogrammforce, which gives roughly identical figures
> for computations as long as we are on earth. To signify the difference,
> though, these force units were then called kiloponds (abbreviated kp,
> latin: pondus = weight).
>
> To comply with international SI units, they abandoned this unit soon
> (right after I had to learn it in school) and introduced the Newton as
> the official unit of force. Using Newton's law, it is defined by the
> force that is needed to accelerate one kilogram of mass from zero to the
> speed of one meter per second during one second (1 m / s / s) and as
> such independent of local gravity. Using the average gravity constant of
> our planet, it turns out that one Newton is approx. 1/10 of a kilopond
> or kilogrammforce (exactly 1 N = 1 / 9.81 kp = 0.102 kp). Newton himself
> never explained the difference between heavy mass and inertia of mass.
>
> For engineering purposes, and to maintain the same figures and values
> they were used to, the old mechanical engineers used metric prefixes and
> made up the DekaNewton = ten Newtons, abreviated DN (greek: deka = ten,
> abbrev. D ). One DekaNewton = 1.02 kp, so, for the time being, they
> could keep using those old handbooks and their figures of material
> properties. It was, though, easy to confuse with the abbreviation for
> "nominal diameter", DN, so this was not successful on the long run.
>
> To express angular momentum, we have to multiply force by the length of
> the lever, i.e. one meter. So we arrive at the unit DNm = 10 Nm ^= 1
> kpm, and the world is in almost perfect order again.
>
> So far, this was all based on the kilogramm-meter-second system (KMS).
> In physics, they used another widely used system which gave handier
> figures for small scale considerations, the gramm - centimeter - second
> system (CGS). In this system, the unit of force is one dyn = 1 gramm
> divided by 1 cm / s / s. 1 N = 100 000 dyn, 1 Nm = 100 000 dyn m, 1 dyn
> = 1/100 000 N. The world was a hundred thousand times smaller.
>
> So, to make a long story short, I think your unit of kdm could mean a
> thousand dyn times meter, extremely unusual in technology and
> engineering science:
> 1 kdm = 1000 x 1/100 000 Nm = 1/100 Nm. Easy to confuse this dyn unit
> with dezi- = 1/10!
>
> Now, your dad must have a pretty old car since this cgs system was
> abandoned in 1978. Are you sure that the above explanation is right, or
> is it rather the kiloDekaNewtonMeter? What is the value on that rating
> plate?
>
> Best regards from
>
> Peter Blodow
>
>
>
> andy pugh schrieb:
>
>> On 16 June 2012 00:37, N. Christopher Perry  
>> wrote:
>>
>>  
>>> There are about 1.3 Nm to a ft-lb.
>>>
>>>
>> Which would reduce confusion no end, except motor manufacturers want
>> bigger numbers, so like to use oz-inch in the US.
>>
>> There was a similar tendency in the metric world, but it seems to have
>> passed. You do occasionally see motors with peculiar units, my dad has
>> one with (I think) kilo-dyne-metres on the rating plate.
>> (that's about 100 x Nm, ie 1 kdm = 0.01Nm)
>>
>>
>>  
>
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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 08:22, Peter Blodow  wrote:

> Now, your dad must have a pretty old car since this cgs system was
> abandoned in 1978. Are you sure that the above explanation is right, or
> is it rather the kiloDekaNewtonMeter?

Thinking back, it was actuality the rating of the variable-speed
gearbox that was attached to the motor.
And we didn't get much further than realising that the whole
motor/gearbox assembly was too feeble for our requirements.


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Re: [Emc-users] Brushless Servo Selection?

[Peter Blodow]

Andy,
way back in my school time, curriculum makers detected that mass and 
force are different things. Before, forces were expressed in mass units, 
i.e., kilogramms (greek: chilioi = thousand, gramma = weight), and 
sometimes called kilogrammforce, which gives roughly identical figures 
for computations as long as we are on earth. To signify the difference, 
though, these force units were then called kiloponds (abbreviated kp, 
latin: pondus = weight).

To comply with international SI units, they abandoned this unit soon 
(right after I had to learn it in school) and introduced the Newton as 
the official unit of force. Using Newton's law, it is defined by the 
force that is needed to accelerate one kilogram of mass from zero to the 
speed of one meter per second during one second (1 m / s / s) and as 
such independent of local gravity. Using the average gravity constant of 
our planet, it turns out that one Newton is approx. 1/10 of a kilopond 
or kilogrammforce (exactly 1 N = 1 / 9.81 kp = 0.102 kp). Newton himself 
never explained the difference between heavy mass and inertia of mass.

For engineering purposes, and to maintain the same figures and values 
they were used to, the old mechanical engineers used metric prefixes and 
made up the DekaNewton = ten Newtons, abreviated DN (greek: deka = ten, 
abbrev. D ). One DekaNewton = 1.02 kp, so, for the time being, they 
could keep using those old handbooks and their figures of material 
properties. It was, though, easy to confuse with the abbreviation for 
"nominal diameter", DN, so this was not successful on the long run.

To express angular momentum, we have to multiply force by the length of 
the lever, i.e. one meter. So we arrive at the unit DNm = 10 Nm ^= 1 
kpm, and the world is in almost perfect order again.

So far, this was all based on the kilogramm-meter-second system (KMS). 
In physics, they used another widely used system which gave handier 
figures for small scale considerations, the gramm - centimeter - second 
system (CGS). In this system, the unit of force is one dyn = 1 gramm 
divided by 1 cm / s / s. 1 N = 100 000 dyn, 1 Nm = 100 000 dyn m, 1 dyn 
= 1/100 000 N. The world was a hundred thousand times smaller.

So, to make a long story short, I think your unit of kdm could mean a 
thousand dyn times meter, extremely unusual in technology and 
engineering science:
1 kdm = 1000 x 1/100 000 Nm = 1/100 Nm. Easy to confuse this dyn unit 
with dezi- = 1/10!

Now, your dad must have a pretty old car since this cgs system was 
abandoned in 1978. Are you sure that the above explanation is right, or 
is it rather the kiloDekaNewtonMeter? What is the value on that rating 
plate?

Best regards from

Peter Blodow



andy pugh schrieb:
> On 16 June 2012 00:37, N. Christopher Perry  
> wrote:
>   
>> There are about 1.3 Nm to a ft-lb.
>> 
>
> Which would reduce confusion no end, except motor manufacturers want
> bigger numbers, so like to use oz-inch in the US.
>
> There was a similar tendency in the metric world, but it seems to have
> passed. You do occasionally see motors with peculiar units, my dad has
> one with (I think) kilo-dyne-metres on the rating plate.
> (that's about 100 x Nm, ie 1 kdm = 0.01Nm)
>
>   


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Re: [Emc-users] Brushless Servo Selection?

[Erik Christiansen]

On 15.06.12 10:40, Kirk Wallace wrote:
> On Fri, 2012-06-15 at 10:53 +0100, andy pugh wrote:
> > This is a problem with motors like the Keling ones, with a 48V rated 
> > voltage.
> > It is far simpler to make a 300V PSU than a 48V one. Simply rectifying
> > mains voltage into a big capacitor makes a PSU that the 8i20 is happy
> > with.
...
> 48 Volts or rather -48 Volts DC is common for telephone equipment, so
> there may be cheap supplies available, if one knows where to look.

Have to concur, and yes, being in the right place at the right time is
what secured one for me. There is a bonus though, voltage-wise. The "-48
Volts DC" in telephone exchanges comes from big battery banks, so the
"power supplies" are usually hefty battery chargers, and will put out at
least 60v to boost charge the batteries. The small one (2x2x1 ft) I
collared does 65v (Boost), 54v (Float2), and 52.8v (Float1) at 20A.
The only thing is there won't be filter caps in there, I expect. 

The SMPS designs produced by the hardware-only team, during my several
decades in telecoms transmission systems design, had to cope with the
65v for a limited time, and the float voltage indefinitely. I don't know
how hot the charger would get after an extended time on Boost at 20A,
e.g. if it were used for a 1.3 kW spindle supply.

Erik

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 16 June 2012 00:37, N. Christopher Perry  wrote:
> There are about 1.3 Nm to a ft-lb.

Which would reduce confusion no end, except motor manufacturers want
bigger numbers, so like to use oz-inch in the US.

There was a similar tendency in the metric world, but it seems to have
passed. You do occasionally see motors with peculiar units, my dad has
one with (I think) kilo-dyne-metres on the rating plate.
(that's about 100 x Nm, ie 1 kdm = 0.01Nm)

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Re: [Emc-users] Brushless Servo Selection?

[N. Christopher Perry]

There are about 1.3 Nm to a ft-lb.

N. Christopher Perry

On Jun 15, 2012, at 18:40, cogoman  wrote:

> On 06/14/2012 10:33 PM, Jon Elson wrote:
>> Thats inch-POUNDS!  16 times inch-Ounces.
>> 56 In-Lb is 896 Oz-In, so you have made a mistake.  Also, steppers,
>> ESPECIALLY
> Thanks.  I don't have an intuitive feeling for N-m measures, so for 
> quite a while I have been making this mistake in my head.  I had 
> wondered why the motors Keling sells were so popular, but so weak.  Now 
> I know better.  8-)
> 
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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 15 June 2012 23:40, cogoman  wrote:

> Thanks.  I don't have an intuitive feeling for N-m measures,

As a comparison, the triple stack NEMA 23 steppers are up to 3Nm.

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Re: [Emc-users] Brushless Servo Selection?

[cogoman]

On 06/14/2012 10:33 PM, Jon Elson wrote:
> Thats inch-POUNDS!  16 times inch-Ounces.
> 56 In-Lb is 896 Oz-In, so you have made a mistake.  Also, steppers,
> ESPECIALLY
Thanks.  I don't have an intuitive feeling for N-m measures, so for 
quite a while I have been making this mistake in my head.  I had 
wondered why the motors Keling sells were so popular, but so weak.  Now 
I know better.  8-)

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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 15 June 2012 18:40, Kirk Wallace  wrote:

> Another thing I haven't had time to look into is using a Delon doubler
> when one needs higher voltage than what is at hand.
> http://en.wikipedia.org/wiki/File:Bridge_voltage_doubler.svg
> http://en.wikipedia.org/wiki/Voltage_doubler

Yes, I built a doubler (the aim was to connect it to an Arduino and
IRAMS module to make a step-up 3-phase fixed-frequency drive to run
the motor in my milling machine.

I looked at the dot-board in front of me, with 730V DC on it and got
scared, and didn't pursue the idea any further.

-- 
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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/15 Fox Mulder :
>
> The datasheet shows that it has two 32V and one 18V and one 12V output
> (Makes in total 4).
> On each of the 32V lines you can have up to 23.4A and both other 2A.

Thank You! I somehow missed the presence of datasheet.

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Re: [Emc-users] Brushless Servo Selection?

[Fox Mulder]

Am 15.06.2012 19:58, schrieb Viesturs Lācis:
> 2012/6/15 Kirk Wallace :
>>
>> Building an Antek supply shouldn't be too expensive, but I haven't
>> checked prices recently.
>> http://www.antekinc.com/index.php
>> http://www.antekinc.com/gview.php
>>
> 
> Thanks for the links! 155$ is little more that I would like,
> especially if it is a shipment from US - add 22% VAT and also shipping
> cost...
> 
> But I still got interested to find out, so I looked at this one:
> http://www.antekinc.com/details.php?p=146
> 
> It is rated for 23,4 A and has 4 outputs. A noob question:
> Is it meant to be able to handle 23,4 A on each of the 4 outputs at
> the same time?
> 

The datasheet shows that it has two 32V and one 18V and one 12V output
(Makes in total 4).
On each of the 32V lines you can have up to 23.4A and both other 2A.

Ciao,
 Rainer

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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/15 Kirk Wallace :
>
> Building an Antek supply shouldn't be too expensive, but I haven't
> checked prices recently.
> http://www.antekinc.com/index.php
> http://www.antekinc.com/gview.php
>

Thanks for the links! 155$ is little more that I would like,
especially if it is a shipment from US - add 22% VAT and also shipping
cost...

But I still got interested to find out, so I looked at this one:
http://www.antekinc.com/details.php?p=146

It is rated for 23,4 A and has 4 outputs. A noob question:
Is it meant to be able to handle 23,4 A on each of the 4 outputs at
the same time?

-- 
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If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/15 andy pugh :
> On 15 June 2012 06:58, Viesturs Lācis  wrote:
>
>> Unfortunately it requires relatively larger power supply with higher
>> current output.
>
> This is a problem with motors like the Keling ones, with a 48V rated voltage.
> It is far simpler to make a 300V PSU than a 48V one. Simply rectifying
> mains voltage into a big capacitor makes a PSU that the 8i20 is happy
> with.

Yes, I even have servos with 330V rated voltage, but they are too
small current-wise for 8i20.

> Those Keling motors have a 500V / 1 min rating. I don't know if that
> meas that they can run indefinitley on a 300V PWM (with a 48V
> "average" or not). In the US I suppose a rectified-mains PSU would be
> around 150V which sounds more reasonable.

Hmm, this sounds tempting, I can get 1 kW transformer not very
expensive with something like 42 VAC output, rectifying that will give
something close to 60 VDC...

What are the risks, when brushless servos are ran on overvoltage supply?
Will they just be warming, which I think is tolerable or is it a nice
way to damage them?

> 3x rated voltage, and it is conventional
> to run steppers at that sort of overvoltage

Those Nema 23 steppers that I have used are rated at 5,46 VDC for with
windings connected in series for bipolar drive, I am running them with
28 VDC in one machine and 48 VDC in welding robot, so that is getting
close to 10x overvoltage.

But what about brushless servos?
Has anyone tried that and gained some experience to share?

-- 
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Re: [Emc-users] Brushless Servo Selection?

[Kirk Wallace]

On Fri, 2012-06-15 at 10:53 +0100, andy pugh wrote:
> On 15 June 2012 06:58, Viesturs Lācis  wrote:
> 
> > Unfortunately it requires relatively larger power supply with higher
> > current output.
> 
> This is a problem with motors like the Keling ones, with a 48V rated voltage.
> It is far simpler to make a 300V PSU than a 48V one. Simply rectifying
> mains voltage into a big capacitor makes a PSU that the 8i20 is happy
> with.
> 
> Those Keling motors have a 500V / 1 min rating. I don't know if that
> meas that they can run indefinitley on a 300V PWM (with a 48V
> "average" or not). In the US I suppose a rectified-mains PSU would be
> around 150V which sounds more reasonable. (only 3x rated voltage, and
> it is conventional to run steppers at that sort of overvoltage)
> 

48 Volts or rather -48 Volts DC is common for telephone equipment, so
there may be cheap supplies available, if one knows where to look.

Building an Antek supply shouldn't be too expensive, but I haven't
checked prices recently.
http://www.antekinc.com/index.php 
http://www.antekinc.com/gview.php 

One could make a transformer for the needed voltage, like these guys
did.
http://mackys.livejournal.com/838591.html 

Brushed motors (and drives) might be cheaper and universal motors are
usually wound for mains voltage. If they can be modified for permanent
magnets, universal motors could be handy.
http://www.supermagnetman.net/index.php?cPath=37&page=3 

For most of us, brushes wear well enough to not be a maintenance
problem. Scrap yards should have a large supply of vacuum cleaner motors
from people that don't know how to replace a rubber belt.

Another thing I haven't had time to look into is using a Delon doubler
when one needs higher voltage than what is at hand.
http://en.wikipedia.org/wiki/File:Bridge_voltage_doubler.svg 
http://en.wikipedia.org/wiki/Voltage_doubler 


-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] Brushless Servo Selection?

[Todd Zuercher]

That is what I was thinking, the existing motors are quite old and are
probably not as strong as they should be either, so if I am buying new
drives and motors anyway, I thought switching to servos would be a good
idea, especially since I would need to get some sort of hardware step
generation to make use of a microstepping drive.

Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street 
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031
 


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E-mail: to...@pgrahamdunn.com
630 Henry St.
Dalton, OH 44618
www.pgrahamdunn.com
-Original Message-
From: Jon Elson [mailto:el...@pico-systems.com] 
Sent: Thursday, June 14, 2012 10:33 PM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Brushless Servo Selection?

cogoman wrote:
>450 Oz-in. steppers are pretty hefty devices.
>I followed the link to the Keling website, and the heftiest motor 
> they listed was a maximum of 6.3N.m, which I assume (correct me if I'm

> wrong) means Newton-Meters.  The conversion calculator I used gave me
56 
> inch pounds, a little more than a tenth of the torque your steppers 
> should be able to put out.  If you get outright stalls with 450 inch 
> pounds, you will more often get outright stalls with 56 inch pounds.
If 
> you are missing steps, it's probably not the motors' faults.
Something 
> else is probably at work here.
>
>   
Thats inch-POUNDS!  16 times inch-Ounces.
56 In-Lb is 896 Oz-In, so you have made a mistake.  Also, steppers, 
ESPECIALLY
with non-microstepping drives, are susceptible to timing variations and 
resonance
issues.  If you used a hardware step pulse generator and microstepping 
drives such
as the Gecko 201 or 203 drive, you probably would get rid of the errors.

At 1000 RPM, all reasonable steppers have lost significant torque from
their
holding torque rating.  But, for peace of mind, and since you would need

to replace
the drives anyway to go with microstepping ones, you might as well go 
the servo
route.  It isn't that much more expensive.

Jon




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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 15 June 2012 06:58, Viesturs Lācis  wrote:

> Unfortunately it requires relatively larger power supply with higher
> current output.

This is a problem with motors like the Keling ones, with a 48V rated voltage.
It is far simpler to make a 300V PSU than a 48V one. Simply rectifying
mains voltage into a big capacitor makes a PSU that the 8i20 is happy
with.

Those Keling motors have a 500V / 1 min rating. I don't know if that
meas that they can run indefinitley on a 300V PWM (with a 48V
"average" or not). In the US I suppose a rectified-mains PSU would be
around 150V which sounds more reasonable. (only 3x rated voltage, and
it is conventional to run steppers at that sort of overvoltage)

-- 
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If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Brushless Servo Selection?

[Viesturs Lācis]

2012/6/13 Todd Zuercher :
>
> I was thinking of picking up some AMC servo drives off ebay (BE12A6
> drives seem to be cheep and plentiful there).

Mesa 8i20 is cheaper, do not know about Pico drives.

And paired with KL34BLS-98 ($134/pcs) servo motor it should be a good
match: motor has peak current of 33A (and more than 4Nm torque there):
http://kelinginc.net/34BLMotor.pdf
The drive will handle up to 30A.

What do others think of this combination? I was thinking about using
them this way.

Unfortunately it requires relatively larger power supply with higher
current output.
OTOH I suspect that commanded acceleration limits will have impact on
how much torque is drawn from motor and thus how much current will it
need. But that is just my own speculation...


> What would be a good motor for this and where to buy them?  (Max RPM
> will be less than 1500 without changing gearing, with 1000 being more
> realistic.)

I think that with servos You can easily expect much higher RPM. That
Keling, for example, is rated for 3000 RPM.

> How high of a resolution encoder will I need?

I think that generally it would be - the more resolution, the easier
tuning and better positional accuracy. The card that counts those
pulses is the limiting factor.
If the motor can do 3000 RPM = 50 rps, then 1024 cpr encoder will give
4096 ppr = 204800 pps. That is not even close to those few MHz
counting rates I have seen for FPGA cards.

> Short of cobbling together all this stuff for a closed loop system, I am
> also considering buying a 4 axis servo system from DMM-Tech (costs about
> $1700) and running Linuxcnc open loop. (probably still use the 5i25 for
> hardware step generation).

And for LinuxCNC You still would have the same open-loop step-dir system...
IMHO doing it that way loses at least 75% of the reason, why would one
better use servos instead of steppers.

1700$? 4 Keling motors would be 536 $, 4 8i20s would be 960 $ = 1496 $
total... Add the cost of wiring and it would be somewhere there. The
whole difference is in the degree of control You have.

-- 
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http://www.ifixit.com/Manifesto

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Re: [Emc-users] Brushless Servo Selection?

[Jon Elson]

cogoman wrote:
>450 Oz-in. steppers are pretty hefty devices.
>I followed the link to the Keling website, and the heftiest motor 
> they listed was a maximum of 6.3N.m, which I assume (correct me if I'm 
> wrong) means Newton-Meters.  The conversion calculator I used gave me 56 
> inch pounds, a little more than a tenth of the torque your steppers 
> should be able to put out.  If you get outright stalls with 450 inch 
> pounds, you will more often get outright stalls with 56 inch pounds.  If 
> you are missing steps, it's probably not the motors' faults.  Something 
> else is probably at work here.
>
>   
Thats inch-POUNDS!  16 times inch-Ounces.
56 In-Lb is 896 Oz-In, so you have made a mistake.  Also, steppers, 
ESPECIALLY
with non-microstepping drives, are susceptible to timing variations and 
resonance
issues.  If you used a hardware step pulse generator and microstepping 
drives such
as the Gecko 201 or 203 drive, you probably would get rid of the errors.

At 1000 RPM, all reasonable steppers have lost significant torque from their
holding torque rating.  But, for peace of mind, and since you would need 
to replace
the drives anyway to go with microstepping ones, you might as well go 
the servo
route.  It isn't that much more expensive.

Jon

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Re: [Emc-users] Brushless Servo Selection?

[cogoman]

I'm concerned that you are about to make a mistake, and waste a lot of 
money.

   450 Oz-in. steppers are pretty hefty devices.  The mill we use at 
work has servo motors rated for approximately 500 oz-in. maximum, and 
they are expensive to replace.  These have all the grunt we need for a 
lot of heavy milling.  The steppers you have should be able to keep up.  
Steppers lose torque at high speed, but most heavy cutting takes place 
at feed rates that have a stepper motor putting out full torque.
   I followed the link to the Keling website, and the heftiest motor 
they listed was a maximum of 6.3N.m, which I assume (correct me if I'm 
wrong) means Newton-Meters.  The conversion calculator I used gave me 56 
inch pounds, a little more than a tenth of the torque your steppers 
should be able to put out.  If you get outright stalls with 450 inch 
pounds, you will more often get outright stalls with 56 inch pounds.  If 
you are missing steps, it's probably not the motors' faults.  Something 
else is probably at work here.

   The only valid reason I could see for upgrading would be to get 
faster rapids.  If you are trying to drive the steppers faster than they 
can go, you may lose steps, but otherwise you should look at another cause.

   First find the drive voltage, and the coil inductance of the motors. 
With a switching stepper motor controller, 70 volts can get a 1mH coil 
up to 7 amps in about 100uS.if you give it another 100uS to stay at 7 
amps, you can have almost full torque for 200uS per step.  For a full 
stepped standard 200 steps per rev motor that would be 1500 RPM.

   Your motors probably don't have that low inductance. Divide by 2 for 
2mH = 750RPM.  Divide by 3 for 3mH = 500RPM.  That should be plenty to 
keep up with milling at even 50 IPM.  I wouldn't want to go far above 
3mH for something that has to be fast.

   These guys have a NEMA 34 motor with 7A (parallel) coil current at 
1.2mH per coil with nearly 600 oz-in.

http://www.homeshopcnc.com/index.php?page=shop.product_details&flypage=gk_flypage.tpl&product_id=29&category_id=5&option=com_virtuemart&Itemid=1
 


   That would be a pretty fast stepper, with good torque.

   I suspect your problem is either electrical/wiring getting old, or if 
you have a rubber resonance damper in the system, and it has become 
petrified.  Rubber gets old.  you may just need to replace a resonance 
damper, as resonance can drop the torque to 0.0 well before the top RPM 
should occur. If the resonance damper is not too far gone, it could be 
causing seemingly random errors.

   Also 7A is a lot of current.  Dirty connectors can limit that 
current, or at least the speed that current ramps up at.  You could 
connect some wires to a coil on the stepper that's giving you the most 
trouble, and connect it to a DMM,  See if the voltage is what it's 
supposed to be when the motor just comes to a stop.  If the wires are 
hooked up to screw terminals, and that has gotten corroded, a little 
cleaning with Scotch Brite or fine sand paper, and re-tightening may 
solve your problem. Plug in connectors could be tougher to fix.  I hope 
you don't have old wire that needs replacing.

   Of course, if your problem is A: bad wiring or B: a hardened 
resonance damper, or C: too much resistance in the high current wiring 
to the motor;   AND... if you replaced the whole system with an 
expensive servo system with new wiring and no resonance dampers; your 
problem should go away.

   I suspect that if it's a simple problem with the stepper system, a 
simple solution would be just as satisfying.

On 06/13/2012 11:48 AM, Todd Zuercher wrote:
> I am thinking about trying to upgrade some old routers from steppers to
> servos.  I am seeking advice on a good and inexpensive BLDC motor to
> use.
>
> The steppers on them now are NEMA 34 with a 3/8" shaft, rated at 7amp
> and 450 oz-in. and are half stepping from an old Anaheim Automation
> unipolar bi-level drive.
>
> We are tired of lost and missed steps not to mention outright stalls
> ruining pieces.


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Re: [Emc-users] Brushless Servo Selection?

[andy pugh]

On 13 June 2012 16:48, Todd Zuercher  wrote:

> I was thinking of picking up some AMC servo drives off ebay (BE12A6
> drives seem to be cheep and plentiful there).  And run about a 400W
> motor of some sort.  I think I would like to use a Mesa 5i25 for
> controlling it all (is that a good choice?).

Both Pico and Mesa do brushless motor drives that integrate well with
their controller cards.
That probably makes more sense than buying a smart drive and ignoring
the smartness.
Mesa have a bit of a gap between the 250W 7i39 (which connects to the
50-way header on the 5i20, 5i23, 5i22 or 7i43 boards) and the 8i20
(2.2kW) which connects via Smart-serial.
You can connect 2x 7i39 to each connector on a 5i23, for example, for
a total of 6 motors. A 5i25 with the correct firmware could control 16
8i20 drives.

The Pico brushless servo amp is also a bit oversized for the motors
you are suggesting (120V, 20A), but is somewhat cheaper than the Mesa
8i20.

Keling seem to have a fair range of motors in a directly compatible
size to your existing steppers:
http://www.kelinginc.net/DCBrushlessMotor.html

There is a HAL component that can handle any combination of motor
output and amplifier input.

-- 
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[Emc-users] Brushless Servo Selection?

[Todd Zuercher]

I am thinking about trying to upgrade some old routers from steppers to
servos.  I am seeking advice on a good and inexpensive BLDC motor to
use.

 

The steppers on them now are NEMA 34 with a 3/8" shaft, rated at 7amp
and 450 oz-in. and are half stepping from an old Anaheim Automation
unipolar bi-level drive. 

We are tired of lost and missed steps not to mention outright stalls
ruining pieces. 

 

I was thinking of picking up some AMC servo drives off ebay (BE12A6
drives seem to be cheep and plentiful there).  And run about a 400W
motor of some sort.  I think I would like to use a Mesa 5i25 for
controlling it all (is that a good choice?). 

 

What daughter card(s) for the 5i25 would be best? (I will need 4 axes
XYZW)

 

What would be a good motor for this and where to buy them?  (Max RPM
will be less than 1500 without changing gearing, with 1000 being more
realistic.)

How high of a resolution encoder will I need?

 

Short of cobbling together all this stuff for a closed loop system, I am
also considering buying a 4 axis servo system from DMM-Tech (costs about
$1700) and running Linuxcnc open loop. (probably still use the 5i25 for
hardware step generation).

 

 

Todd Zuercher

P. Graham Dunn Inc.  

630 Henry Street 

Dalton, Ohio 44618

Phone:  (330)828-2105ext. 2031

 



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