Re: [Emc-users] Micro-switch repeatability

[Gregg Eshelman]

On 2/16/2016 9:40 PM, John Dammeyer wrote:
> I believe they only use the home switch to figure out where the end of the
> printer is.  Once established for page of printing it's not used to
> reference until perhaps the next page and probably not even then.  From then
> on the positioning is based on the motor steps.  Just think if they had to
> do a slow homing operation on every line.

They use a linear or rotary encoder. HP's mostly use a spring tensioned 
plastic strip behind the carriage, with optical sensors straddling it.

Others use a thin plastic disk on one of the shafts in the drivetrain.

A common cause of problems with the linear type is ink fog on the strip. 
Cleaning gently with a bit of damp paper towel folded over the strip can 
often fix problems where the printer wants to slam the carriage against 
the ends. You have to start the printer up then pull the power cord 
after it takes the carriage out of its parked position. That's so you 
can slide it to be able to clean the whole strip.

Cleaning the disk encoders involves taking the printer apart. Some 
printers seem to be designed to be serviced, the higher end HP inkjets 
used to have a panel on one end for easy removal of the 'dock' so the 
nozzle wipers, priming system and waste ink sump and absorber could be 
pulled out and cleaned.

Other printers, well, they *can* be taken apart but the case may not 
look so pretty after reassembly.


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Re: [Emc-users] Micro-switch repeatability

[John Dammeyer]

I believe they only use the home switch to figure out where the end of the
printer is.  Once established for page of printing it's not used to
reference until perhaps the next page and probably not even then.  From then
on the positioning is based on the motor steps.  Just think if they had to
do a slow homing operation on every line.

John Dammeyer


> -Original Message-
> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> Sent: February-16-16 6:34 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Micro-switch repeatability
> 
> 
> Look at how inkjet printers work.  They need to trip a home switch so that
> each line of sprayed ink lines on to better then 1/1000th of an inch.
They
> use a low cost optical device.  There is a slot cut in a plastic block.
> One one side is a LED on the other a light detector.  The look at each
> other through a pin hole.  They are very reputable and you can get then
for
> free from salvaged printers.   One trick is to modulate he LED's light at
> about 30KHz and use an RC filter on the detector so as to be insensitive
to
> absent light.   The plastic block the interrupts the beam is just a simple
> square, no slot or hole.  If you have to buy a new one the cost is about
$1.
> 
> On Tue, Feb 16, 2016 at 6:46 AM, Roland Jollivet

> wrote:
> 
> > On 16 February 2016 at 14:46, Bertho Stultiens 
> > wrote:
> >
> > > On 02/16/2016 01:38 PM, Nicklas Karlsson wrote:
> > >  It seems that the micro-switches are well suited for the purpose,
> > but
> > > I
> > >  guess some hard (unbiased) data has yet to be gathered (outside
of
> a
> > > mill).
> > > >>> The alternatives seem to have the same problems of repeatability.
> > Using
> > > >>> a hall sensor or optical one will give the same problems.
> > > Micro-switches
> > > >>> are at least inherently mechanically constrained.
> > > >> Indeed, unless you can crush them. There must be a
run-into-the-wall
> > > >> protection, as mentioned earlier, to prevent killing your switch.
> > > >
> > > > Pass over the switch might be possible?
> > >
> > > No. The datasheets I've read all say the same that you must activate
the
> > > plunger straigt on. Any angle will give you bad performance. Any
> > > sideways stress on the plunger can kill the plunger assembly.
> > >
> > > The only alternative is to use a level-based micro-switch. That,
> > > however, will probably make it less accurate. Especially when you move
> > > over it side-ways. The angle of attack is too small with respect to
the
> > > travel distance.
> > >
> > > --
> > > Greetings Bertho
> > >
> > >
> > >
> > That's not true. Use a switch like this
> > <
> > http://uk.rs-online.com/web/p/microswitches/1031645/?searchTerm=103-
> 1645
> data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C
> 753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F2
> 55C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F5354
> 4F434B5F4E554D4245522677633D4E4F4E45267573743D3130332D3136343526
> > >,
> > where the roller is almost directly over the plunger.
> > Then, use a wiper with an edge set at about 70deg. When this approaches
> the
> > switch, the angled edge will cause full travel over less than 1mm. After
> > that, overtravel will have no effect.
> >
> > I've never seen a travel limit switch used head-on in a machine. It's a
> > ticket to disaster.
> >
> > Regards
> > Roland
> >
> >

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> >
> 
> 
> 
> --
> 
> Chris Albertson
> Redondo Beach, California
>

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[Emc-users] Anilam and Westamp Amplifier

[Marshland Engineering]

I have a working Anilam Lathe with Servo Dynamics boards. The do run around
120v DC. In my circuit diagrams and in my machine there is a very large output
choke in line with the motors.  Possibly you need these. 

Cheers Wallace


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Re: [Emc-users] Micro-switch repeatability

[Gregg Eshelman]

On 2/16/2016 6:47 AM, Bertho Stultiens wrote:

> The micro-switches look like they can manage at almost no cost. But then
> my curiosity got in my way on how far you actually can go with the
> cheapo method. I'm now considering to take an old CD player and move the
> laser-assembly onto several micro-switches at different speeds. The
> laser-assembly is sub-micrometer accurate (CD track-separation runs at
> 1.5...1.6 um) and generally uses a simple stepper.

They don't get that accuracy with the stepper. The lens is suspended on 
springs and uses magnetic coils for fine positioning radially for 
tracking and vertically to focus.


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Re: [Emc-users] Micro-switch repeatability

[Chris Albertson]

Look at how inkjet printers work.  They need to trip a home switch so that
each line of sprayed ink lines on to better then 1/1000th of an inch.  They
use a low cost optical device.  There is a slot cut in a plastic block.
One one side is a LED on the other a light detector.  The look at each
other through a pin hole.  They are very reputable and you can get then for
free from salvaged printers.   One trick is to modulate he LED's light at
about 30KHz and use an RC filter on the detector so as to be insensitive to
absent light.   The plastic block the interrupts the beam is just a simple
square, no slot or hole.  If you have to buy a new one the cost is about $1.

On Tue, Feb 16, 2016 at 6:46 AM, Roland Jollivet 
wrote:

> On 16 February 2016 at 14:46, Bertho Stultiens 
> wrote:
>
> > On 02/16/2016 01:38 PM, Nicklas Karlsson wrote:
> >  It seems that the micro-switches are well suited for the purpose,
> but
> > I
> >  guess some hard (unbiased) data has yet to be gathered (outside of a
> > mill).
> > >>> The alternatives seem to have the same problems of repeatability.
> Using
> > >>> a hall sensor or optical one will give the same problems.
> > Micro-switches
> > >>> are at least inherently mechanically constrained.
> > >> Indeed, unless you can crush them. There must be a run-into-the-wall
> > >> protection, as mentioned earlier, to prevent killing your switch.
> > >
> > > Pass over the switch might be possible?
> >
> > No. The datasheets I've read all say the same that you must activate the
> > plunger straigt on. Any angle will give you bad performance. Any
> > sideways stress on the plunger can kill the plunger assembly.
> >
> > The only alternative is to use a level-based micro-switch. That,
> > however, will probably make it less accurate. Especially when you move
> > over it side-ways. The angle of attack is too small with respect to the
> > travel distance.
> >
> > --
> > Greetings Bertho
> >
> >
> >
> That's not true. Use a switch like this
> <
> http://uk.rs-online.com/web/p/microswitches/1031645/?searchTerm=103-1645=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3130332D3136343526
> >,
> where the roller is almost directly over the plunger.
> Then, use a wiper with an edge set at about 70deg. When this approaches the
> switch, the angled edge will cause full travel over less than 1mm. After
> that, overtravel will have no effect.
>
> I've never seen a travel limit switch used head-on in a machine. It's a
> ticket to disaster.
>
> Regards
> Roland
>
> --
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>



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Re: [Emc-users] Anilam and Westamp Amplifier

[Gene Heskett]

On Tuesday 16 February 2016 12:55:38 Mark Johnsen wrote:

> I have a converted Anilam Crusader M to linuxcnc and I was looking at
> the Westamp Servo amplifier and I'm not sure which model Anilam put in
> the machine.  I think it's a 10amp cont/22amp peak, but not sure.
>
> I have been able to find a manual for the amplifiers, but the manual
> uses a different part numbering scheme and I cannot discern which
> model is in the machine.
>
> AMPLIFIER PART NUMBER(s)
> ASSY 30059-75  (Part number on the blue circuit board with '75'
> hand-written in)
> MODULE 30060-75 (Part number on the sheet metal sticker - entirely
> hand written)
>
> MANUAL PART NUMBERS -  The manual lists THREE MODELS:
> A651x-10C:   10amps cont/15amps peak.  Switching freq 16Khz
> A651x-10E:   10amps cont/22amps peak  Switching freq 5Khz
> A651x-10F:   10amps cont/30amps peak  Switching freq 5Khz
> INPUT POWER (all models):  10VAC to 70VAC Bus power, 120Vac at 2amps
> Bias Power.
>
> SEM MT30M4-59 MOTOR specs:
> Cont Stall Torque:  3Nm
> Cont Stall Current:  5.6amps
> Torque Const:  .54Nm/A
> Peak Stall Torque:  14Nm
> Peak Current:  30 AMPS
> Motor volt gradient:  59V/1000rpm
> Max armature Voltage:  140V
> Max RPM:  2400rpm
> Tacho Gradient:  9.5V/1000rpm
>
> Since I have the motor specs, knowing exactly which amplifier I have
> isn't that important, but as I started looking into this, I'd like to
> understand what the designers did...
>
> Here's a picture on ebay of the amplifier:
> http://www.ebay.com/itm/131240516302
> I specifically showed that one because they reference the Servo
> Dynamics SD1525-10  (15amps cont/25amps peak).  My understanding is
> that when Westamp closed, the engineers moved to Servo Dynamics and
> their SD1525-10 is a replacement for the aforementioned Westamp board.
>
> LINK to MANUAL for A6511:
> https://sites.google.com/site/bmklawt/home/westamp-documentation/westa
>mp-manual This manual is from an Anilam conversion by "Bmklawt" with
> the help of Jon Elson.  On the website, there's also links to a
> circuit diagram of the system.
>
> On page 18 of the A6511 manual, there is a picture of a board layout
> with the part number:  30059-___.  This is the right manual...
>
> Since my amplifier 'squeals' something awful (assuming switching freq
> 5Khz) and the motor has a 30amp peak current rating, I'm making an
> assumption that the amplifier is an A6511-10E (22amps peak) or -10F
> (30amps peak).
>
> *  MEASURED INPUT POWER TO AMPLIFIERS*
> The measured spec confuses me - I measured 80Vac at the transformer
> output and the amplifier manual says that input power should be 10VAC
> to 70VAC, there might be a 15% 'overage' allowed?  Or I have something
> wrong here?
>
> ACTUAL MEASUREMENTS
> 120Vac before the transformer
> 80Vac after the transformer
> 113Vdc at the Capacitor and input to amplifiers.
>
> One thing to note is that the amplifier board has a rectifier wired in
> and attached to the sheet metal.
>
> *  WHAT REPLACEMENT DRIVE??  ***
> Also, for someone wanting to replace one of these older amplifiers,
> what is a good replacement?  John Elson had recommended a Copley 422
> on a previous mailing list.
>
His own servo amp, intended for an ultrasonic PWM input, has a 160 volt, 
20 amp rating.  I am amazed at what that amp can do with a 126 volt DC 
power supply, to a 1HP rated PMDC motor that came on this Grizzly G0704.

The OEM driver, a triac driven unit, ran it at around 2300 rpms wide 
open, but only 600 in reverse. Running on wall plug 126 volts AC.

I ripped it off, box and all, and put one of Johns amps in in its place, 
driving it at about 30 kilohertz, pwm. I have the keap current limit set 
for around 16 amps if it should get stalled.

Jon's amp runs it a bit over 2800 revs, either direction.  At 2500 revs, 
I can enter an M3 to start it, or an M4 to reverse it.  I put a rate 
limiter in the hal to slow the reversal down, bujt even with the rate 
limiter, it can switch from running 2500 FWD, to 2500 reversed in 
nominally 1 second flat.  Doing rigid tapping at 200 rpms, the turn 
around at the bottom of the stroke is just a click.

If I had the sheckles to convert everything to servo's, Jons amplifier 
would be my obvious choice. I am using 2 of them as the spindle motor in 
that toy lathe is now a 1HP treadmill motor.  I had to slow the reversal 
way down on that machine else it slipped the teeth right off the drive 
belt AND the smaller pulley. 3 times so far. $pen$ive.

> I would agree that if the Westamp amplifier is the -10E
> (10cont/22peak), then the Copley 422 is perfect at 10amp cont/20amps
> peak, but if Anilam used the -10F (10cont/30peak), then the 423
> (15cont/30peak) is a better choice.  I suppose a question is, how much
> of that 14Nm do you really need??
>
> On ebay there are some inexpensive AMC 30A8V amps, but they're only
> rated to 80Vdc input, too low:-(
>
> ***   WHICH ONE IS IT?  

Re: [Emc-users] Needed, pyvcp expert

[Gene Heskett]

On Tuesday 16 February 2016 10:03:27 John Thornton wrote:

> A multi-label will handle the label changes, not sure what your asking
> for the hal pins to do that you can't do in hal with logic components.
>
> JT

That is not the problem, at least so far.

I take it that you have not seen what camview-emc could once do?  All of 
that is working right now except for calibration of the camera's offset 
from the spindle centerline.  The scripts all get run when I click on 
the gui's added buttons.  They don't do much without valid data, but 
they do run.

In the meantime, I have found an editor (xmlcopyeditor) written 
specifically to edit xml files, so I have made a teeny bit of headway in 
that at least I can see where I have a tag miss-match now.

But I've been getting the camera mounted today, and I am about bushed.

The mount is solid, but when I put a bolt & washer on the base to serve 
as an always assembles correctly stopper, I put in dead center in the 
edge of the base, forgetting there was a trench for camera cable exit 
there in the camera carrier so it slides right on by the washer.  Not a 
biggie as I can do the same on the camera carrier tomorrow except use 2 
3mmx5 bolts so they catch the ears of the dovetail, locating it a fixed 
distance from the spindle centerline.  But the 3mm x 5mm long bolts are 
a trip to HomeDepot in Bridgeport.  I'm fresh out + I need some x10's & 
x12's to shrink the envelope of the carrier anyway. The x18's I had to 
use stick out like a sore thumb.  :(

So I spent the last hour jacking on camera holding screws, more 3mm cap 
screws, getting the parallax out of the up/down motion while keeping the 
image something resembling vertical.

Thanks John.

> On 2/15/2016 8:59 PM, Gene Heskett wrote:
> > Howdy all;
> >
> > Looking at the gui additions for the camera stuff, is it possible to
> > have a bidirectional button by associating the button click with a
> > halpin that is an output, but use a 2nd halpin as an input to
> > control both the text in the button and its color with this 2nd
> > halpin?
> >
> > I am assuming that under all this it is Tkinter doing the actual gfx
> > bit twidling.  Is that where I should be looking for helpful hints? 
> > What is discussed in the manual starting on page 386 does not seem
> > to indicate the possiblity of using two hal "wires" to control one
> > button.  If a second halpin could be defined, and an on_text string
> > and an off_text string defined just as in on_color and off_color,
> > that would be the bee's knees.
> >
> > Thanks.
> >
> > Cheers, Gene Heskett
>
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Cheers, Gene Heskett
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[Emc-users] Anilam and Westamp Amplifier

[Mark Johnsen]

I have a converted Anilam Crusader M to linuxcnc and I was looking at the
Westamp Servo amplifier and I'm not sure which model Anilam put in the
machine.  I think it's a 10amp cont/22amp peak, but not sure.

I have been able to find a manual for the amplifiers, but the manual uses a
different part numbering scheme and I cannot discern which model is in the
machine.

AMPLIFIER PART NUMBER(s)
ASSY 30059-75  (Part number on the blue circuit board with '75'
hand-written in)
MODULE 30060-75 (Part number on the sheet metal sticker - entirely hand
written)

MANUAL PART NUMBERS -  The manual lists THREE MODELS:
A651x-10C:   10amps cont/15amps peak.  Switching freq 16Khz
A651x-10E:   10amps cont/22amps peak  Switching freq 5Khz
A651x-10F:   10amps cont/30amps peak  Switching freq 5Khz
INPUT POWER (all models):  10VAC to 70VAC Bus power, 120Vac at 2amps Bias
Power.

SEM MT30M4-59 MOTOR specs:
Cont Stall Torque:  3Nm
Cont Stall Current:  5.6amps
Torque Const:  .54Nm/A
Peak Stall Torque:  14Nm
Peak Current:  30 AMPS
Motor volt gradient:  59V/1000rpm
Max armature Voltage:  140V
Max RPM:  2400rpm
Tacho Gradient:  9.5V/1000rpm

Since I have the motor specs, knowing exactly which amplifier I have isn't
that important, but as I started looking into this, I'd like to understand
what the designers did...

Here's a picture on ebay of the amplifier:
http://www.ebay.com/itm/131240516302
I specifically showed that one because they reference the Servo Dynamics
SD1525-10  (15amps cont/25amps peak).  My understanding is that when
Westamp closed, the engineers moved to Servo Dynamics and their SD1525-10
is a replacement for the aforementioned Westamp board.

LINK to MANUAL for A6511:
https://sites.google.com/site/bmklawt/home/westamp-documentation/westamp-manual
This manual is from an Anilam conversion by "Bmklawt" with the help of Jon
Elson.  On the website, there's also links to a circuit diagram of the
system.

On page 18 of the A6511 manual, there is a picture of a board layout with
the part number:  30059-___.  This is the right manual...

Since my amplifier 'squeals' something awful (assuming switching freq 5Khz)
and the motor has a 30amp peak current rating, I'm making an assumption
that the amplifier is an A6511-10E (22amps peak) or -10F (30amps peak).

*  MEASURED INPUT POWER TO AMPLIFIERS*
The measured spec confuses me - I measured 80Vac at the transformer output
and the amplifier manual says that input power should be 10VAC to 70VAC,
there might be a 15% 'overage' allowed?  Or I have something wrong here?

ACTUAL MEASUREMENTS
120Vac before the transformer
80Vac after the transformer
113Vdc at the Capacitor and input to amplifiers.

One thing to note is that the amplifier board has a rectifier wired in and
attached to the sheet metal.

*  WHAT REPLACEMENT DRIVE??  ***
Also, for someone wanting to replace one of these older amplifiers, what is
a good replacement?  John Elson had recommended a Copley 422 on a previous
mailing list.

I would agree that if the Westamp amplifier is the -10E (10cont/22peak),
then the Copley 422 is perfect at 10amp cont/20amps peak, but if Anilam
used the -10F (10cont/30peak), then the 423 (15cont/30peak) is a better
choice.  I suppose a question is, how much of that 14Nm do you really
need??

On ebay there are some inexpensive AMC 30A8V amps, but they're only rated
to 80Vdc input, too low:-(

***   WHICH ONE IS IT?  *
If anyone has some info on which westamp drive is actually in the system,
I'd love to know.

On a side note, I saw that the 29794 transistors are on ebay for between
$25 and $45 each...  The parts might actually be worth more than the
board...

Regards,
Mark

PS - it turns out I have some Copley 800-992, which are factory configured
422's...  Might be nice to make a switch.
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Re: [Emc-users] Mattel 3D Printer

[Dave Cole]

Lawn Darts ...   yep those were fun but quickly got boring - no element 
of danger. The next thought was Lawn Dart wars..  since those steel 
tips weren't that sharp, they probably wouldn't "stick" !   We got a 
little crazy with those!   I had a neighbor who would pay me a 
dollar or two to go and buy him a carton of cigarettes at the local 
grocery store.A carton was I think 4-5 dollars at the time.   So 
that was pretty good money!   I'd ride my bike a half mile to the 
grocery store and make some quick cash.The grocery store clerk 
didn't even wink..  give her the money, get the carton of cigarettes.
The good old days when toys were fun and they still had an element of 
danger!
Dave

On 2/16/2016 2:46 AM, Bruce Layne wrote:
> I had a Thingmaker when I was a kid.  It was a set of aluminum creepy
> crawler molds with some bottles of toxic and probably carcinogenic
> rubber goo.  The molds were placed on a hotplate to vulcanize the
> synthetic rubber and the hotplate was probably 400F. I think there were
> also some sharp exposed edges of stamped sheet metal, and it plugged
> into a 120VAC outlet and it was not double insulated.  Kids should know
> not to play with it in the bathtub, or outside when it's raining.
>
> That was back when lawn darts were legal and I'd build homemade model
> rockets with payloads of gasoline or  black powder that the sporting
> goods department would sell to ten year old kids.
>
> It's amazing that companies never learn not to sell hackable hardware
> below cost in the hope to entice customers into buying the high priced
> add-ons.  Everything can be hacked, and it's usually more fun to hack it
> than to use it as intended by the manufacturer.
>
> It seems that everyone is selling a 3D printer now, and the technology
> is quickly moving mainstream.  Meanwhile, I'm hacking my LinuxCNC router
> to 3D print RTV silicone rubber.  If I wanted to, I could print my own
> creepy crawly rubber toys, a lot safer than a 1970 Thingmaker.
>
>
>
> On 02/16/2016 02:20 AM, Gregg Eshelman wrote:
>
>> BTW, Mattel is soon to release a 3D printer called Thingmaker, operated
>> with a smartphone app to print out toys designed using snap together
>> parts downloaded from Mattel. It has an auto-locking cover and the hot
>> end retracts to a shielded area so kids can't get their fingers on
>> anything hot.
>>
>> Price supposed to be around $300. If it's any good I'll bet there will
>> be hacks to use other software with it within days of first sale.
>
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Re: [Emc-users] Micro-switch repeatability

[TJoseph Powderly]

agreed
a near home switch
and
a home switch

fanuc called the near hone a 'decel switch'
tomp

On 02/16/2016 10:42 PM, Kurt M. Sanger wrote:
> When we were building high resolution printers we would use an optical
> switch looking at a rotary flag in series with a linear switch to define
> home.  We repeated well within ten thousandths of an inch.
>
> Kurt Sanger
>


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Re: [Emc-users] Needed, pyvcp expert

[John Thornton]

A multi-label will handle the label changes, not sure what your asking 
for the hal pins to do that you can't do in hal with logic components.

JT

On 2/15/2016 8:59 PM, Gene Heskett wrote:
> Howdy all;
>
> Looking at the gui additions for the camera stuff, is it possible to have
> a bidirectional button by associating the button click with a halpin
> that is an output, but use a 2nd halpin as an input to control both the
> text in the button and its color with this 2nd halpin?
>
> I am assuming that under all this it is Tkinter doing the actual gfx bit
> twidling.  Is that where I should be looking for helpful hints?  What is
> discussed in the manual starting on page 386 does not seem to indicate
> the possiblity of using two hal "wires" to control one button.  If a
> second halpin could be defined, and an on_text string and an off_text
> string defined just as in on_color and off_color, that would be the
> bee's knees.
>
> Thanks.
>
> Cheers, Gene Heskett


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Re: [Emc-users] Micro-switch repeatability

[Ed]

On 02/16/2016 06:46 AM, Bertho Stultiens wrote:
> The only alternative is to use a level-based micro-switch. That, 
> however, will probably make it less accurate. Especially when you move 
> over it side-ways. The angle of attack is too small with respect to 
> the travel distance. 


I use roller lever switches bought from DigiKey on my CHNC lathe on a 
pass by setup. That lets me have the limit switches past the home and 
not have to worry about crashing the switch. Repeatability was about 
.0003 inches before the Index pulse was implemented, now within a tenth. 
Use a fairly steep ramp and you get better results.

Ed.


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[Emc-users] Micro-switch repeatability

[Roland Jollivet]

On 16 February 2016 at 14:46, Bertho Stultiens  wrote:

> On 02/16/2016 01:38 PM, Nicklas Karlsson wrote:
>  It seems that the micro-switches are well suited for the purpose, but
> I
>  guess some hard (unbiased) data has yet to be gathered (outside of a
> mill).
> >>> The alternatives seem to have the same problems of repeatability. Using
> >>> a hall sensor or optical one will give the same problems.
> Micro-switches
> >>> are at least inherently mechanically constrained.
> >> Indeed, unless you can crush them. There must be a run-into-the-wall
> >> protection, as mentioned earlier, to prevent killing your switch.
> >
> > Pass over the switch might be possible?
>
> No. The datasheets I've read all say the same that you must activate the
> plunger straigt on. Any angle will give you bad performance. Any
> sideways stress on the plunger can kill the plunger assembly.
>
> The only alternative is to use a level-based micro-switch. That,
> however, will probably make it less accurate. Especially when you move
> over it side-ways. The angle of attack is too small with respect to the
> travel distance.
>
> --
> Greetings Bertho
>
>
>
That's not true. Use a switch like this
,
where the roller is almost directly over the plunger.
Then, use a wiper with an edge set at about 70deg. When this approaches the
switch, the angled edge will cause full travel over less than 1mm. After
that, overtravel will have no effect.

I've never seen a travel limit switch used head-on in a machine. It's a
ticket to disaster.

Regards
Roland
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Re: [Emc-users] Emc-users Digest, Vol 118, Issue 61

[Gene Heskett]

On Tuesday 16 February 2016 08:15:43 Robert von Knobloch wrote:

> On 16/02/16 14:02, emc-users-requ...@lists.sourceforge.net wrote:
> >> Pass over the switch might be possible?
> >
> > No. The datasheets I've read all say the same that you must activate
> > the plunger straigt on. Any angle will give you bad performance. Any
> > sideways stress on the plunger can kill the plunger assembly.
> >
> > The only alternative is to use a level-based micro-switch. That,
> > however, will probably make it less accurate. Especially when you
> > move over it side-ways. The angle of attack is too small with
> > respect to the travel distance.
> >
> > -- Greetings Bertho
>
> Bertho,
>
> FWIW I made mine by using small, round bar magnets (ca. 6 x 15 mm) and
> reed switch capsules. I milled out small (25mm) pieces of 10 x 10mm
> aluminium and epoxied the switches and magnets each in one. These, I
> glued to the machine with cyanoacrylate such they slide past each
> another horizontally, with a small gap (no contact at all) . I haven't
> measured the repeatability but it seems pretty good and they are cheap
> and sealed against junk getting in.
>
> Cheers,
> Bob
I used the round buttons Grizzly put on the tables for hard stops but 
took the stops off and the button just rolls the wheel in the end of the 
lever as they go by for X, and put a pointer on the head sled to hit 
the roller on a post mounted switch. All 3 can go on by without damaging 
the switch.

On the toy mill when I put some teeny ball screws in it, I put a switch 
with a plain lever to sense when the screw was about to come out of the 
nut by letting the lever come out as the end of the screw passed the 
root of the lever.  That made a quite decent homing switch, so I then 
set the software limit to stop it a few thou before it hit the hard 
stops at the other end of the travel.  But on that mill I have never 
tried to put a switch on the Z.  It has the whole post to play on, so 
there aren't any sw limits and I just touch it off where ever I need it 
to be.

On the lathe, Z switch is about an inch from the empty chuck to the empty 
toolpost, and X switch trip is about 5 thou from the X maximum backout, 
so I remove the tool holder from the QC post, and the ctl+home sequence 
finds X first, then since that will clear the tool post with anything 
under 2.5" in the chuck, goes & finds that Z home & then parks it at 2" 
away from the chuck.  All 3 machines seem to have pretty good.  On the 
lathe of course both measurements are completely arbitrary since there 
is not a way to put a tool point so it blocks a beam of light thats 
exactly on the centerline.  Repeatability is more important, and that 
seems to be adequate. More important when turning is taper, and the best 
way to control that is to map X against Z but LCNC cannot to that so I 
have to put it in the gcode. And that works about 75% of the time, 
depending on the direction and backlash, but .002" accuracy is do-able 
for about 3 or 4" of Z travel.  Then bed wear sets in and I've not tried 
to compensate for that, yet...

However, hint hint, if X could be mapped according to Z, that would be 
the cats meow. Use one map when running in the chuck, and another when 
using a tailstock too.

Any axis to any other axis would be the ice cream on the pie. Those are 
my major sources of error on all 3 machines.

Accuracy of the screw thread itself hasn't appeared to be a problem, with 
acme or ball screws within my ability to measure it, but that would be a 
bit crude to do with my limited range indicator tools.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Micro-switch repeatability

[Kurt M. Sanger]

When we were building high resolution printers we would use an optical 
switch looking at a rotary flag in series with a linear switch to define 
home.  We repeated well within ten thousandths of an inch.

Kurt Sanger

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Re: [Emc-users] Micro-switch repeatability

[Bertho Stultiens]

On 02/16/2016 03:15 PM, TJoseph Powderly wrote:
>> I heard rumors here a while ago about micro meter accuracy switch
>> but I guess it might be a little bit expensive.
> my-com switches, 1um guaranteed. every good german wedm uses them
> and high end japanese
> my-com
> yes expensive   paeng maak!  but damn accurate

Yes, 10um ... 5um version starts at about $200, the 1um version is
between $800 and $1500 (depending where you look and what manufacturer).
Actually, the high-side of the price knows no limit.

The whole machine cost $1500 (used) and is about $3500 new. I /could/
install switches more expensive than the machine, but I guess that it
would be slight overkill, not much, but just a teensy bit of overkill.

Hence the humble inquiry into cheapo micro-switches ;-)


-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Micro-switch repeatability

[TJoseph Powderly]

my-com switches, 1um guaranteed. every good german wedm uses them
and high end japanese
my-com

yes expensive   paeng maak!  but damn accurate
tomp

On 02/16/2016 02:53 PM, Nicklas Karlsson wrote:
> I heard rumors here a while ago about micro meter accuracy switch but I guess 
> it might be a little bit expensive.
>


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Re: [Emc-users] Micro-switch repeatability

[Bertho Stultiens]

On 02/16/2016 02:01 PM, Lester Caine wrote:
>> Indeed, unless you can crush them. There must be a run-into-the-wall
>> protection, as mentioned earlier, to prevent killing your switch.
> 
> The problem on the Taig is while one hits the end stop one end, you come
> out of the nut the other ;) But while stalling the motors looses
> position, it's not a particular problem from the safety point of view.
> Unless you put a finger in the way ...

The router here is constrained at both ends, so that would be fine.
Stalling will be an issue.

Regarding fingers, well, I'm not sure about some of the would-be
operators ;-)

We do have a sign stating "KillBot Machine" and other large graphic and
descriptive words of how you will die when mismanaging the machine.


> I've been looking to fit slotted sensors as limit switches to prevent
> problems at both ends of the table, with a flag on the bed which goes
> through the sensor (so no crush problem), and this is fine for limiting
> things, but it's repeatability is somewhat suspect for use as a home
> position. I was seeing 0.1mm drift depending on various factors, but not
> being desperate for it I did not investigate further.

Optical sensors are problematic for repeatability unless you have very
good ones (like encoders).

That said, general accuracy of 0.1mm would be sufficient for most of the
things done on the machine (simple woodwork).

The machine itself is rated at 0.02mm repositioning, so a 0.01mm homing
repeatability is more than enough.

The micro-switches look like they can manage at almost no cost. But then
my curiosity got in my way on how far you actually can go with the
cheapo method. I'm now considering to take an old CD player and move the
laser-assembly onto several micro-switches at different speeds. The
laser-assembly is sub-micrometer accurate (CD track-separation runs at
1.5...1.6 um) and generally uses a simple stepper.


-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Emc-users Digest, Vol 118, Issue 61

[Robert von Knobloch]

On 16/02/16 14:02, emc-users-requ...@lists.sourceforge.net wrote:
>> Pass over the switch might be possible?
> No. The datasheets I've read all say the same that you must activate the
> plunger straigt on. Any angle will give you bad performance. Any
> sideways stress on the plunger can kill the plunger assembly.
>
> The only alternative is to use a level-based micro-switch. That,
> however, will probably make it less accurate. Especially when you move
> over it side-ways. The angle of attack is too small with respect to the
> travel distance.
>
> -- Greetings Bertho
Bertho,

FWIW I made mine by using small, round bar magnets (ca. 6 x 15 mm) and 
reed switch capsules. I milled out small (25mm) pieces of 10 x 10mm 
aluminium and epoxied the switches and magnets each in one. These, I 
glued to the machine with cyanoacrylate such they slide past each 
another horizontally, with a small gap (no contact at all) . I haven't 
measured the repeatability but it seems pretty good and they are cheap 
and sealed against junk getting in.

Cheers,
Bob

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Re: [Emc-users] Micro-switch repeatability

[Lester Caine]

On 16/02/16 12:26, Bertho Stultiens wrote:
>> The alternatives seem to have the same problems of repeatability. Using
>> > a hall sensor or optical one will give the same problems. Micro-switches
>> > are at least inherently mechanically constrained.
> Indeed, unless you can crush them. There must be a run-into-the-wall
> protection, as mentioned earlier, to prevent killing your switch.

The problem on the Taig is while one hits the end stop one end, you come
out of the nut the other ;) But while stalling the motors looses
position, it's not a particular problem from the safety point of view.
Unless you put a finger in the way ...

I've been looking to fit slotted sensors as limit switches to prevent
problems at both ends of the table, with a flag on the bed which goes
through the sensor (so no crush problem), and this is fine for limiting
things, but it's repeatability is somewhat suspect for use as a home
position. I was seeing 0.1mm drift depending on various factors, but not
being desperate for it I did not investigate further.

-- 
Lester Caine - G8HFL
-
Contact - http://lsces.co.uk/wiki/?page=contact
L.S.Caine Electronic Services - http://lsces.co.uk
EnquirySolve - http://enquirysolve.com/
Model Engineers Digital Workshop - http://medw.co.uk
Rainbow Digital Media - http://rainbowdigitalmedia.co.uk

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Re: [Emc-users] Micro-switch repeatability

[Bertho Stultiens]

On 02/16/2016 01:38 PM, Nicklas Karlsson wrote:
 It seems that the micro-switches are well suited for the purpose, but I
 guess some hard (unbiased) data has yet to be gathered (outside of a mill).
>>> The alternatives seem to have the same problems of repeatability. Using
>>> a hall sensor or optical one will give the same problems. Micro-switches
>>> are at least inherently mechanically constrained.
>> Indeed, unless you can crush them. There must be a run-into-the-wall
>> protection, as mentioned earlier, to prevent killing your switch.
> 
> Pass over the switch might be possible?

No. The datasheets I've read all say the same that you must activate the
plunger straigt on. Any angle will give you bad performance. Any
sideways stress on the plunger can kill the plunger assembly.

The only alternative is to use a level-based micro-switch. That,
however, will probably make it less accurate. Especially when you move
over it side-ways. The angle of attack is too small with respect to the
travel distance.

-- 
Greetings Bertho

(disclaimers are disclaimed)

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Re: [Emc-users] Micro-switch repeatability

[Nicklas Karlsson]

> On 02/16/2016 12:42 PM, Lester Caine wrote:
> > On 16/02/16 10:21, Bertho Stultiens wrote:
> >> It seems that the micro-switches are well suited for the purpose, but I
> >> guess some hard (unbiased) data has yet to be gathered (outside of a mill).
> > 
> > The alternatives seem to have the same problems of repeatability. Using
> > a hall sensor or optical one will give the same problems. Micro-switches
> > are at least inherently mechanically constrained.
> 
> Indeed, unless you can crush them. There must be a run-into-the-wall
> protection, as mentioned earlier, to prevent killing your switch.

Pass over the switch might be possible?

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Re: [Emc-users] Micro-switch repeatability

[Bertho Stultiens]

On 02/16/2016 12:42 PM, Lester Caine wrote:
> On 16/02/16 10:21, Bertho Stultiens wrote:
>> It seems that the micro-switches are well suited for the purpose, but I
>> guess some hard (unbiased) data has yet to be gathered (outside of a mill).
> 
> The alternatives seem to have the same problems of repeatability. Using
> a hall sensor or optical one will give the same problems. Micro-switches
> are at least inherently mechanically constrained.

Indeed, unless you can crush them. There must be a run-into-the-wall
protection, as mentioned earlier, to prevent killing your switch.


> I do look at the kit available and wonder if simply adding scale bars
> locked to the table aren’t a sensible compromise here? You have an
> absolute on on the machine which can be used not only to define a home
> position, but also to add limits based on the actual job? Which could be
> used where the natural home position IS in the middle of the work piece.
> I'm not talking about a set of inputs that are used as part of any
> closed loop control, but simply as has been done in the past, a check
> that particular points are in the right place. It could be used to
> measure the current backlash between the motion elements and the base
> machine, with a 'calibrate' cycle as part of the home process?

The point of the switches is not to be correct in perfection. The
background here is that the router is located at the local hackerspace,
where many will have access to the machine. Not all have the same
experience and a run-into-the-wall can be expected from a novice. Well,
an experienced person might just hit the wrong button too ;-)

The router has currently end-stop switches, but none on the other end of
the axes. I'd like to have the controller limit the movement such that
it will stop the machine when running into the wall. This will not
prevent hitting anything with the spindle.

Using a "proper" home (0,0,0 position) will not only make it a lot
easier to recover from an error, but, it allows the machine to be shut
down. Especially the "shut down" is important because it is not expected
that this machine runs 24/7, but mere hours at a time, losing its
position in space every power-cycle.

The natural home, as you say, is the work piece. But that is just an offset.


> Cheap Chinese readout bars can be used as one can easily compensate for
> the latency between readings, and I know in essence you are discussing
> the provision of a 'hardware' zero point on the axis, but as a cross
> check that the machine has not missed steps, or a flexible means of
> moving the machine to a fixed position to recover after a collision or
> stall it has merit?

You are right. It is a hardware zero point. Losing steps is my least
worry at this moment, but it surely has crossed my mind. It is, as you
say, the collisions I am (slightly) worried about. And then, the
power-cycling of the machine.

It is mostly a balance of how much it'll cost and how much I can prevent
problems when many different operators with different experience and
volatile g-code handle the machine. The machine was cheap, so investing
perfection is a bit off.


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Re: [Emc-users] Micro-switch repeatability

[Bertho Stultiens]

On 02/16/2016 12:39 PM, Dave Caroline wrote:
> I originally searched for a switch with data and a local distributor
> had some movement specs of the plunger, I got some but unfortunately
> that distributor no longer lists the item. but it is a Patterson V4
> type microswitch, the .tw website of theirs is not easy to read
> though. One day I might fit them

Most micro-switches avalable from electronics pushers have datasheets.
Most of those datasheets do have "activation distance" (plunger depth
for activation) and hysteresis values.

However, they are specified with only one decimal (in mm). That leaves a
lot of wiggle-room.

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Re: [Emc-users] Micro-switch repeatability

[Lester Caine]

On 16/02/16 10:21, Bertho Stultiens wrote:
> It seems that the micro-switches are well suited for the purpose, but I
> guess some hard (unbiased) data has yet to be gathered (outside of a mill).

The alternatives seem to have the same problems of repeatability. Using
a hall sensor or optical one will give the same problems. Micro-switches
are at least inherently mechanically constrained.

I do look at the kit available and wonder if simply adding scale bars
locked to the table aren’t a sensible compromise here? You have an
absolute on on the machine which can be used not only to define a home
position, but also to add limits based on the actual job? Which could be
used where the natural home position IS in the middle of the work piece.
I'm not talking about a set of inputs that are used as part of any
closed loop control, but simply as has been done in the past, a check
that particular points are in the right place. It could be used to
measure the current backlash between the motion elements and the base
machine, with a 'calibrate' cycle as part of the home process?

Cheap Chinese readout bars can be used as one can easily compensate for
the latency between readings, and I know in essence you are discussing
the provision of a 'hardware' zero point on the axis, but as a cross
check that the machine has not missed steps, or a flexible means of
moving the machine to a fixed position to recover after a collision or
stall it has merit?

-- 
Lester Caine - G8HFL
-
Contact - http://lsces.co.uk/wiki/?page=contact
L.S.Caine Electronic Services - http://lsces.co.uk
EnquirySolve - http://enquirysolve.com/
Model Engineers Digital Workshop - http://medw.co.uk
Rainbow Digital Media - http://rainbowdigitalmedia.co.uk

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Re: [Emc-users] Micro-switch repeatability

[Dave Caroline]

I originally searched for a switch with data and a local distributor
had some movement specs of the plunger, I got some but unfortunately
that distributor no longer lists the item. but it is a Patterson V4
type microswitch, the .tw website of theirs is not easy to read
though. One day I might fit them

Dave Caroline

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Re: [Emc-users] Micro-switch repeatability

[Bertho Stultiens]

On 02/16/2016 07:53 AM, Nicklas Karlsson wrote:
> I heard rumors here a while ago about micro meter accuracy switch but
> I guess it might be a little bit expensive.

Well, yes. The "real" switches which are /specified/ with repeatability
values of about 0.005mm are in the order of $200...$300 per unit from
what I found. The ones specified at 0.001mm are about an order of
magnitude more expensive. Even specified 0.010mm repeatability switches
are in the $100 class range.

This is a cheapo - not-too-good, not-too-bad - used router (bought for
$1500). Using expensive homing switches is like upgrading your bicycle
to run a formula 1 race ;-)


It looks like micro-switches will do just fine if the speed is
controlled. Maybe it would be a good idea to have a two-stage trip, as
mentioned. Proximity to home and then a home switch. Then you can
control the mechanics a bit better.


On 02/16/2016 03:00 AM, John Alexander Stewart wrote:
> I did some tests, plotted the results, etc, at:
> http://cnc-for-model-engineers.blogspot.ca/2015/06/home-switch-repeatability.html

Those numbers are not /that/ good if you think about it. At least not in
comparison to /significantly better than 0.001"/, what others report.

I had seen you graph while searching the net, but asked the question
here anyway because you already said that there might be some problems
with the measurement.


> I think my major issue was the mounting for my dial indicator, and
> if you do read the article, I did some tests with my new mill, and 
> results are the same or better. I was *totally* surprised at how well
> they worked.

Your graph does seem to indicate some kind of bias. However, it is hard
to tell whether it is a mechanical feature or your measurement setup (as
you mention).

However, when we get into these kinds of distances, simple temperature
and moisture changes are a factor too. Especially with (mechanical)
electronics involved.


It seems that the micro-switches are well suited for the purpose, but I
guess some hard (unbiased) data has yet to be gathered (outside of a mill).


-- 
Greetings Bertho

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