Re: [Emc-users] possibly good news for LinuxCNC

[Przemek Klosowski]

On Wed, Apr 24, 2019 at 4:39 PM andy pugh  wrote:

> On Wed, 24 Apr 2019 at 14:47, andy pugh  wrote:
>
> > When I get back the machine tonight I will report back with the last
> > thing seen on the screen.
>
> I tried the suggested new config, and this is what I get:
> https://www.youtube.com/watch?v=gZw-nLf_XBg
>
> Immediately after "started apache http server" it goes to a screen
> that is blank but for a (not flashing) cursor.
>

It is pretty far along if it got to starting the apache server: the kernel
booted, the init process must have run a bunch of setup, etc.
I'd disable apache and try booting again; maybe change the linux kernel
commandline by adding something like 'single' or 'init=/bin/sh', to get a
basic system with just shell running.
If that's stable, then I'd start running various services by hand, one by
one.
Of course it is possible that the the kernel runs for few seconds and
latches up, and it just coincides with apache startup---but you should see
that while in the single shell as well.

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Re: [Emc-users] [Off topic] Might interest Gene, radio pirates.

[TJoseph Powderly]

and the movie was great
https://en.wikipedia.org/wiki/The_Boat_That_Rocked

On 04/25/2019 12:28 AM, andy pugh wrote:

https://hackaday.com/2019/04/24/radio-piracy-on-the-high-seas/

tomp


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Re: [Emc-users] possibly good news for LinuxCNC

[Chris Albertson]

On Wed, Apr 24, 2019 at 2:07 AM Gene Heskett  wrote:

> On Wednesday 24 April 2019 03:42:00 andy pugh wrote:
>
> > On Wed, 24 Apr 2019 at 01:30, Gene Heskett 
> wrote:
> > > Several, your personal config probably makes a far bigger difference
> > > than the actual version number of the kernel since you have to be
> > > pretty well up on YOUR hardware to re-configure the kernel you are
> > > about to build.
>
> > And there is the problem. I have never yet managed to get that step
> > right and make a version that works on my PC.
> > (I tried and failed with the NTULinux repo last night)
>
> URL?
>
> > And the problem to be solved here is building a kernel that can ship
> > with LinuxCNC and work with _any_ kernel.
> >
> > Is it, in fact, currently impossible to provide an RTAI LinuxCNC ISO
> > with any kernel newer that the one we ship with Wheezy?
>
> IDK Andy. Has the current rtai kernel been tried on stretch? Nah, its 32
> bit, claims PAE but is not. Stretch is 64 bit.
>
> > If that is the case then perhaps it is time to abandon RTAI
> > altogether?
>
> Might be, I have only 1 preempt-rt versions running here, not on software
> stepping though, both on mesa cards, a 7i90HD+3 ea 7i42TA's running the
> Sheldon, and the 5i25/7i76D running the G0704. But I've not changed the
> kernel on the 6040, that machine WAS formerly softstepping the old HF
> micro so its still running the live iso's kernel. But I've no clue if
> software stepping would run on it. If I software step it, it would be
> buckets slower, 10 ipm or so rapids, where its doing 200 now.  And I'd
> have to share all my home switches for lack of i/o.
>
> I hope at the end of the day, that we don't have to abandon software
> stepping as thats the lowest cost entry point.


SOftware stepping on PC hardware with Linux is "hard" but software stepping
otherwise is cheap and easy.

I have right here on my desk a little machine that uses a Raspberry Pi with
"stock" Unbuntu 18.04 and it runs two servo DC motors or steppers with
nearly
perfect accuracy using a $3 "Real time processor".

As I type, I'd using Fusion 360 to design an enclosure for the parts and
connectors.
I'm looking at a 180x120x40 mm box that house the Pi3 and a driver for up
to 15 amps
per motor and do A/B encoder interrups at about 100KHz.  $60 total.

Size but not cost will be reduced what I can make a custom PCB

My point is that "cost of entry" need not be a PC with a  Mesa card.
It could be a Pi3 with one (or more) $3 STM32 board.Both the STM and
Mesa
can do steps and read encoders way-faster than is required. USB work
well. It is 10X faster then needed for this purpose.


Thge BBB is very atractive because it in effect has the above Pi3 and
STM32 eqivalent (the PRUs+) all on one board.

The Beagal Bard Blue would be PERFECT as it has low power H-brindges and
conecters for A/B encodrs on-board.A small mill or router
would not even need motor drivers.  high-power cables could plug into the
BBB. (BB Blue)
But this is a $100 board.  Double the cost

So the entry cost should be under $100 including the PC and smaller size
motor drivers.

If a person already owned a small notebook PC the entry level price should
be
closer to $20.

I've been using these parts to drive motors of all kinds and they are "bomb
proof"
you can't kill them.  they have reverse plolarity, short and temperaure
protection
It is a simple H-bridge with PWM control.
https://www.ebay.com/itm/30A-Mini-VNH2SP30

 I combine two of the above with one these
https://www.ebay.com/itm/STM32F103

and have abuot a $10 total for a universal driver/controller and the PID
loop and
encoder inputs are on the $2 STM32..   The STM32 connects to the Pi3 or
notebook PC with USB.

I'm slightly frustrated because I'd prefer to see MK run on the above stack
but it
doesn't so I have DIY solution.  and Mk?LinuxCNC is confined to the garage.





> But for my uses, today
> I'd have to figure on at least a 5i25 as a driver card, and that
> unavoidably raises the entry bar for new users by what, 80 bucks?  A sad
> state of affairs.  Your call.
> 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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-- 

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] [Off topic] Might interest Gene, radio pirates.

[Gene Heskett]

On Wednesday 24 April 2019 13:28:19 andy pugh wrote:

> https://hackaday.com/2019/04/24/radio-piracy-on-the-high-seas/

Chuckle, yes, those were the days. Brought on by the bbc's stiff upper 
lip about music, which of course just had to be paid for by the 
listeners.

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] possibly good news for LinuxCNC

[andy pugh]

On Wed, 24 Apr 2019 at 14:47, andy pugh  wrote:

> When I get back the machine tonight I will report back with the last
> thing seen on the screen.

I tried the suggested new config, and this is what I get:
https://www.youtube.com/watch?v=gZw-nLf_XBg

Immediately after "started apache http server" it goes to a screen
that is blank but for a (not flashing) cursor.
And that seems to be it.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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[Emc-users] [Off topic] Might interest Gene, radio pirates.

[andy pugh]

https://hackaday.com/2019/04/24/radio-piracy-on-the-high-seas/

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] possibly good news for LinuxCNC

[TJoseph Powderly]

Thanks Bari
Thanks Alec

On 04/24/2019 10:07 PM, bari wrote:


The dev that spent years cleaning up and fixing the rtai.org to make 
it work with LCNC and hosting it at https://github.com/NTULINUX/RTAI 
just got tired of things. rtai.org would not give him credit and 
treated him like a pest even though they heavily borrowed his fixes 
(even at xenomai). Fortune 100's would take months to come up with a 
pittance to pay for the work. So he's done with any new RTAI work. The 
newer posted work at rtai.org is all beta and the really new for 
current kernels hasn't been made public. 3.16.52 kernel is the latest 
stable kernel to work with RTAI and LCNC. Anything newer will takes 
weeks of work by someone that really knows what they are doing. -Bari

cat /proc/cpuinfo
will produce a line like this:

flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm 
constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl 
vmx est tm2 ssse3 cx16 xtpr pdcm xsave lahf_lm dtherm tpr_shadow vnmi 
flexpriority


the sse and sse2 are needed for the build

the above is from an i686 E6300, runs rt-preempt fine
I think I'll try the rtai build

hth
tomp


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Re: [Emc-users] Looking fro some input from the community

[Jon Elson]

On 04/24/2019 08:45 AM, dave engvall wrote:

Jon,

You are making me feel old; just a fact of life. :-) IIRC 
I had the first PPMC board set out the door. Once one got 
the connector tied down that beastie was rock solid. The 
communication diagnostic was a life saver. Easy way to 
confirm that the communication was working and it 
would/could run for days without an error. Get the 
communication working and you were off and running. Where 
else does  one get a nominal 16 bit controller?



What's a "nominal 16 bit controller"?

Jon


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Re: [Emc-users] Looking fro some input from the community

[Jon Elson]

On 04/24/2019 02:53 AM, Gregg Eshelman via Emc-users wrote:

What about ECP mode, which requires DMA?

ECP mode is great for long, continuous transfers, like a 
printer or scanner.  For CNC motion control in the LinuxCNC 
scheme, there will be pretty short transfers in each 
direction, so the DMA really doesn't help much.  Modern CPUs 
with PCI or PCIe can transfer somewhere around 1.6 
MByte/second in the burst, and a whole servo thread can 
complete in around 100 us, including read hardware state, do 
PID computation and write new velocity, etc.


Jon


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Re: [Emc-users] Looking fro some input from the community

[Joe Hildreth]

Andy,

As I understand it the PCI Address configuration space is handled mostly by the 
BIOS and the CPU.  The bus is enumerated by the BIOS and then configuration 
takes place.  A good lecture on this topic can be found at this video:

https://www.youtube.com/watch?v=ihgMcP2353I

HTH,

Joe

> 
> What sets the base address of a card? Is it the card or the PC / BIOS?
> 


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Re: [Emc-users] possibly good news for LinuxCNC

[bari]

The dev that spent years cleaning up and fixing the rtai.org to make it
work with LCNC and hosting it at https://github.com/NTULINUX/RTAI just
got tired of things. rtai.org would not give him credit and treated him
like a pest even though they heavily borrowed his fixes (even at
xenomai). Fortune 100's would take months to come up with a pittance to
pay for the work. So he's done with any new RTAI work.

The newer posted work at rtai.org is all beta and the really new for
current kernels hasn't been made public.

3.16.52 kernel is the latest stable kernel to work with RTAI and LCNC.
Anything newer will takes weeks of work by someone that really knows
what they are doing.

-Bari

On 4/24/19 2:42 AM, andy pugh wrote:
> On Wed, 24 Apr 2019 at 01:30, Gene Heskett  wrote:
>
>> Several, your personal config probably makes a far bigger difference than
>> the actual version number of the kernel since you have to be pretty well
>> up on YOUR hardware to re-configure the kernel you are about to build.
> And there is the problem. I have never yet managed to get that step
> right and make a version that works on my PC.
> (I tried and failed with the NTULinux repo last night)
>
> And the problem to be solved here is building a kernel that can ship
> with LinuxCNC and work with _any_ kernel.
>
> Is it, in fact, currently impossible to provide an RTAI LinuxCNC ISO
> with any kernel newer that the one we ship with Wheezy?
>
> If that is the case then perhaps it is time to abandon RTAI altogether?
>



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Re: [Emc-users] Servo reduction for gantry machine

[Les Newell]

10m, 35mm width T5 for $60
https://www.aliexpress.com/item/10Meters-T5-open-ended-timing-belt-T5-30-W-30mm-T5-timing-belt-polyurethane-with-steel/2051875939.html



That's a good price. Two of those would do both sides of a 4M machine. 
That is steel cored which is stiffer than Kevlar. Pity one reel isn't 
quite enough to do a 2.4m machine. Of course it would be enough for a 
'tank track' style mechanism. Must...resist...temptation...


Les



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Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry machine

[Les Newell]

But much easier damaged than the 6mm mdf.


'Foamex' type foam board should be tough enough. You would generally use 
a sacrificial spoil board over it anyway.


Les




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Re: [Emc-users] Servo reduction for gantry machine

[Gene Heskett]

On Wednesday 24 April 2019 07:59:37 andy pugh wrote:

> On Wed, 24 Apr 2019 at 12:02, Les Newell  
wrote:
> > One issue I see with off the shelf belts is that none of them have a
> > symmetrical profile. T section looks symmetrical but if you check
> > the drawings it isn't.
>
> T section is what Bell-Everman use.
>
> The Specification document for T section is here:
> https://www.sis.se/api/document/preview/916941/
>
> You are right that there is clearance, I modelled it here:
> https://a360.co/2vgE7me
>
> (Yes, Gene, it will crash your Firefox, don't bother looking)
I did anyway, it crashed on the 2nd site but restarted ok.
>
> But I think that is allowed for in the design, when you tension the
> traveller loop you pull the belt on one side in contact with one set
> of fixed belt faces, and the other side of the pulley to the other set
> of faces.


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] Vacuum bed for router Re: Servo reduction for gantry machine

[andy pugh]

On Wed, 24 Apr 2019 at 14:56, Gene Heskett  wrote:

> The best sealer is shellac. 2 coats of "2 lb cut" sprayed on should do
> it.

The product I linked to is basically shellac in a can.

I used it for sealing MDF foundry patterns with very satisfactory results.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry machine

[Gene Heskett]

On Wednesday 24 April 2019 05:18:49 Les Newell wrote:

> I really like that idea. Getting the slope and pocket dimensions just
> right would take some experimentation but if it works it would save a
> lot of hassle. I dunno if MDF would work as a top plate though. That
> stuff leaks like a sieve, especially if you cut through the outer
> skin. I use 6mm MDF over the whole table as a spoil board and it
> offers little resistance to air flow. I guess you could seal it
> afterwards with paint.

The best sealer is shellac. 2 coats of "2 lb cut" sprayed on should do 
it.
 
> PVC foam board would probably work well though 
> it is quite a lot more expensive than MDF.

But much easier damaged than the 6mm mdf.
>
> Les
>
> On 23/04/2019 22:04, Gregg Eshelman via Emc-users wrote:
> > Les
> > Somewhere I saw a very clever design for a vacuum bed for a router.
> > The top was in two layers instead of simply having a bunch of holes
> > drilled through to the plenum each hole had a pocket off to one
> > side. The bottoms of the pockets sloped slightly downward so that a
> > 6mm Airsoft pellet would fit and roll away from the hole when the
> > vacuum was off. Lay something flat on the bed and vacuum would pull
> > on it through every hole it covered but the uncovered holes would
> > suck the Airsoft pellets out of their pockets to seal them. Shut the
> > vacuum off and all the pellets roll off the holes. Would be easy to
> > retrofit atop any vacuum bed. Remove the original top plate and
> > replace with 1/2" MDF. Use a 5mm drill in the router to make the
> > hole pattern then a slightly larger than 6mm ball end mill to carve
> > the side pockets. Drop in the Airsoft pellets then apply a sheet of
> > 1/8" MDF and redo the 5mm drill pattern. Then the router can do any
> > size work without needing to have pieces of MDF, plywood, sheet
> > metal etc. to cover the unused area. ers
>
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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] possibly good news for LinuxCNC

[andy pugh]

On Wed, 24 Apr 2019 at 14:30, bari  wrote:
>
> What was the problem or error that occurred when building the RTAI
> kernel using that repo?
>
> We were just discussing how he made that as bullet proof as possible. We
> are really interested in what problems occurred.

The build seems to have worked OK, but the kernel does not boot.

I imagine that I have one or more of the config options wrong, but
there are so many it is hard to know where to start looking.

When I get back the machine tonight I will report back with the last
thing seen on the screen.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] Looking fro some input from the community

[dave engvall]

Jon,

You are making me feel old; just a fact of life. :-) IIRC I had the 
first PPMC board set out the door. Once one got the connector tied down 
that beastie was rock solid. The communication diagnostic was a life 
saver. Easy way to confirm that the communication was working and it 
would/could run for days without an error. Get the communication working 
and you were off and running. Where else does  one get a nominal 16 bit 
controller?


Dave

On 4/23/19 8:10 PM, Jon Elson wrote:

On 04/23/2019 09:05 PM, Joe Hildreth wrote:

Jon,

I guess you just have to 'love' standards huh?  heh.  Not to give 
away my age, but the last 'standard' I tried to decipher was NAPLPS.

Well, that was a well-defined standard that never seemed to go anywhere.
Now, overlook my ignorance here, please. What boards do you make?  
Mesa boards?



No, I'm a competitor to Mesa, I make the Pico Systems boards.  The 
original one was PPMC (Parallel Port Motion Control) that had a 
motherboard attached to the parport and then you could plug in DAC, 
encoder counter and digital I/O boards in any combination. Then, I 
added a stepper controller, and a variant of that, a PWM controller.  
And, then a bunch of other stuff that is not directly interfaced to 
LinuxCNC, such as brush and brushless motor drives, an interface 
between my stepper controller and Gecko 320-series step-servos, a 
resolver to quadrature converter, a couple of boards to convert Fanuc 
and Panasonic encoders to standard quadrature, and a board that plugs 
onto the Beagle Bone and holds 6 stepper drives, mostly for 3D printers.


I started making the PPMC in 2002, so this goes back quite a ways.

Jon


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Re: [Emc-users] possibly good news for LinuxCNC

[Todd Zuercher]

Is there someplace where there is a good set of instructions or a tutorial 
about building an RTAI kernel for Linuxcnc?
I have been contemplating taking a crack at trying to build one for a 
particular Machine I have, because it uses an ISA card and I have not been able 
to get any of the Linuxcnc ISOs to work with it since the last Ubuntu 10 one.  
Similar computers with the same CPU and amount of memory but sans ISA slots 
work with the newer ISOs so the problem isn't just that it is an old and slow 
computer.  This leads me to suspect that there is something disabled or not 
included in the kernel configuration is preventing the newer ISOs from working 
on that computer with ISA card.

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

-Original Message-
From: bari  
Sent: Wednesday, April 24, 2019 9:29 AM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] possibly good news for LinuxCNC

What was the problem or error that occurred when building the RTAI kernel using 
that repo?

We were just discussing how he made that as bullet proof as possible. We are 
really interested in what problems occurred.

On 4/24/19 2:42 AM, andy pugh wrote:
> And there is the problem. I have never yet managed to get that step 
> right and make a version that works on my PC.
> (I tried and failed with the NTULinux repo last night)



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Re: [Emc-users] Servo reduction for gantry machine

[andy pugh]

On Wed, 24 Apr 2019 at 14:36, Les Newell  wrote:

> Huh, I didn't think of that. Yes, that would work. Availability of
> longer lengths at sane prices seems to be a bit of an issue though.

10m, 35mm width T5 for $60
https://www.aliexpress.com/item/10Meters-T5-open-ended-timing-belt-T5-30-W-30mm-T5-timing-belt-polyurethane-with-steel/2051875939.html

(yes, Gene, we know it won't work for you and you refuse to use them anyway :-)

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] possibly good news for LinuxCNC

[Mark Wendt]

On Wed, Apr 24, 2019 at 9:40 AM Peter C. Wallace  wrote:
>
> > Okay, so latency is the biggest concern with preempt-rt then.
> >
> >
> > Mark
> >
>
>
> Yes, in my experience RTAI has better latency numbers especially on slower
> hardware. On fast hardware Preempt-RT and RTAI can have similar latency.
> So for example most of the low power fanless PCs have rather dreadful latency
> on Preempt-RT though I3s.. I7s may be fine. It also difficult to compare
> newer CPUs since the RTAI kernsls are old enough that they dont support
> a lot of newer hardware.

Thanks for the explanation Peter.

Mark


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Re: [Emc-users] possibly good news for LinuxCNC

[Peter C. Wallace]

On Wed, 24 Apr 2019, Mark wrote:


Date: Wed, 24 Apr 2019 06:31:00 -0400
From: Mark 
Reply-To: "Enhanced Machine Controller (EMC)"

To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] possibly good news for LinuxCNC

On 4/24/19 06:26, andy pugh wrote:

On Wed, 24 Apr 2019 at 11:09, Mark  wrote:


Does preempt-rt not play well with parport configurations?  Not having
used a preempt-rt installation before, just curious.

It can work fine. In fact my current dev PC shows better preempt-rt
latency than I have eve seen with RTAI.
But that is an outlier and typically RTAI latency is better than 
preempt-rt.



Okay, so latency is the biggest concern with preempt-rt then.


Mark




Yes, in my experience RTAI has better latency numbers especially on slower 
hardware. On fast hardware Preempt-RT and RTAI can have similar latency.

So for example most of the low power fanless PCs have rather dreadful latency
on Preempt-RT though I3s.. I7s may be fine. It also difficult to compare
newer CPUs since the RTAI kernsls are old enough that they dont support
a lot of newer hardware.




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Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.



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Re: [Emc-users] Servo reduction for gantry machine

[Les Newell]

But I think that is allowed for in the design, when you tension the
traveller loop you pull the belt on one side in contact with one set
of fixed belt faces, and the other side of the pulley to the other set
of faces.



Huh, I didn't think of that. Yes, that would work. Availability of 
longer lengths at sane prices seems to be a bit of an issue though. 
Using that technique L, H etc inch belt sizes should also work. I did 
find a supplier of 30mm H section open belt on eBay. Enough for a 4M 
gantry driven on both sides would be around £180. Not too bad. It is 
polyurethane rather than rubber so sticking it could be a problem. 
Unknown Chinese manufacturer so quality is unknown.


Les



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Re: [Emc-users] possibly good news for LinuxCNC

[bari]

What was the problem or error that occurred when building the RTAI
kernel using that repo?

We were just discussing how he made that as bullet proof as possible. We
are really interested in what problems occurred.

On 4/24/19 2:42 AM, andy pugh wrote:
> And there is the problem. I have never yet managed to get that step
> right and make a version that works on my PC.
> (I tried and failed with the NTULinux repo last night)



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Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry machine

[Todd Zuercher]

I work with MDF a lot, and it's dimensional stability leaves much to be 
desired.  I would not want to use it for a table surface if I didn't have to.  
It WILL warp, and sag with time, and changes in relative humidity can cause a 
4x8 sheet to shrink or grow by as much as 1/8 inch.  It is great for use as a 
fall board though and it's porosity will let the vacuum come right through.

Usually for building a vacuum table I have either used a series of rectangular 
aluminum extrusions, or milled a grid in an aluminum plate with some holes for 
plumbing.

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

-Original Message-
From: Marcus Bowman  
Sent: Wednesday, April 24, 2019 5:36 AM
To: Enhanced Machine Controller (EMC) 
Subject: Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry 
machine


On 24 Apr 2019, at 10:18, Les Newell wrote:

> I guess you could seal it afterwards with paint. 

Yes, but having painted MDF before, it requires a particular sealer, then 
several coats of paint, which is a bit of a pain. So its a method which is 
lower in material cost than, say aluminium, but much higher in labour 'cost'.

Marcus




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Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry machine

[andy pugh]

On Wed, 24 Apr 2019 at 10:37, Marcus Bowman
 wrote:

> Yes, but having painted MDF before, it requires a particular sealer,

https://www.screwfix.com/p/zinsser-b-i-n-shellac-based-primer-sealer-1ltr/29661

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] Servo reduction for gantry machine

[andy pugh]

On Wed, 24 Apr 2019 at 12:02, Les Newell  wrote:

> One issue I see with off the shelf belts is that none of them have a
> symmetrical profile. T section looks symmetrical but if you check the
> drawings it isn't.

T section is what Bell-Everman use.

The Specification document for T section is here:
https://www.sis.se/api/document/preview/916941/

You are right that there is clearance, I modelled it here:
https://a360.co/2vgE7me

(Yes, Gene, it will crash your Firefox, don't bother looking)

But I think that is allowed for in the design, when you tension the
traveller loop you pull the belt on one side in contact with one set
of fixed belt faces, and the other side of the pulley to the other set
of faces.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] Servo reduction for gantry machine

[Les Newell]

Cutting your own racks, while doable is a heck of lot of work for the 
lengths you are talking about, even if you make it in short sections. If 
your time is worth even a fraction of minimum wage you would be better 
off using off the shelf rack and pinions.


Here is how I think I would go about gluing a stationary belt in place: 
Fit the belt with clamps at each end that can pull it tight. Now fit a 
temporary solidly mounted pulley on the gantry that engages with the 
belt. Run the gantry back and forth to make sure there are no tight 
spots and adjust the pulley as needed for the best engagement.
Remove the belt, apply a high viscosity urethane rubber adhesive such as 
'tiger seal' or 'sikaflex' and refit. You probably want a helper when 
doing this. The adhesive will push the belt away from the mounting 
surface a bit but don't worry about that. Now run the gantry back and 
forth a few times. The pulley will push the belt into place, squeezing 
out any excess adhesive. Be warned this stuff can be messy so have 
plenty of disposable gloves and paper towel to hand to deal with the 
excess. Petroleum based solvents will remove it when it is wet. It's a 
nightmare to remove once cured.
You'll probably have to move the gantry back and forth a few times as 
the adhesive sets (say once an hour for a day). This should leave you 
with pretty accurate belt alignment, even if the mounting surface isn't 
perfectly aligned. Note I see that open ended belts tend to be 
polyurethane which is difficult stuff to glue reliably. Even 
polyurethane adhesives don't stick that well.


Thinking of alignment, a system like this could be made pretty tolerant 
of alignment issues. The whole roller+pulley assembly could be spring 
loaded to keep the two belts tightly clamped together. Spring loading 
doesn't work well on racks because a spring that is strong enough to 
prevent the pinion from pushing itself out of engagement will cause 
excessive wear and noise. However due to the way the belts engage, this 
belt system should be able to handle considerable pressure without undue 
wear.


One issue I see with off the shelf belts is that none of them have a 
symmetrical profile. T section looks symmetrical but if you check the 
drawings it isn't. This is a big problem with trapezoidal sections as 
they will either have a lot of backlash or not mesh at all, depending on 
the profile. However I have some HTD here and I think it could be made 
to work. In this case the round parts of the teeth would mesh, giving 
you a 45 degree pressure angle. As long as enough preload is applied to 
prevent the belts slipping out of mesh this would result in a very low 
backlash setup. The only backlash would be the teeth distorting under 
load. When they mesh there is a gap between the tips of the teeth and 
the root of opposing belt. This could be a good thing in a dusty 
environment. Dust and dirt should be squeezed into these gaps and 
hopefully would then fall out, much as it does with racks. HTD8M30 belts 
are easily available up to 2.8m long. After that they seem to only be 
available in open ended which is not that easy to obtain.


Dammit, you now have me thinking about building another plasma cutter. I 
already have too many projects on the go...


Les


On 23/04/2019 16:24, Leonardo Marsaglia wrote:

My idea for the "racks" is to make a fly cutter in the CNC lathe and then
use the same lathe to fly cut the teeths, mounting the aluminum rack on a
simple jig on the turret.





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Re: [Emc-users] possibly good news for LinuxCNC

[Mark]

On 4/24/19 06:26, andy pugh wrote:

On Wed, 24 Apr 2019 at 11:09, Mark  wrote:


Does preempt-rt not play well with parport configurations?  Not having
used a preempt-rt installation before, just curious.

It can work fine. In fact my current dev PC shows better preempt-rt
latency than I have eve seen with RTAI.
But that is an outlier and typically RTAI latency is better than preempt-rt.


Okay, so latency is the biggest concern with preempt-rt then.


Mark



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Re: [Emc-users] possibly good news for LinuxCNC

[andy pugh]

On Wed, 24 Apr 2019 at 11:09, Mark  wrote:

> Does preempt-rt not play well with parport configurations?  Not having
> used a preempt-rt installation before, just curious.

It can work fine. In fact my current dev PC shows better preempt-rt
latency than I have eve seen with RTAI.
But that is an outlier and typically RTAI latency is better than preempt-rt.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] possibly good news for LinuxCNC

[Mark]

On 4/24/19 05:36, andy pugh wrote:


One thing wrong with Stretch is that it is not LTS whereas Jessie is.

Also, I have so far failed to make a working RTAI kernel for Stretch.
I think that we need at the very least an optional RTAI ISO for the
parallel port users even if we recommend the preeempt-rt version.



Does preempt-rt not play well with parport configurations?  Not having 
used a preempt-rt installation before, just curious.



Mark



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Re: [Emc-users] possibly good news for LinuxCNC

[andy pugh]

On Tue, 23 Apr 2019 at 11:54, Rene Hopf via Emc-users
 wrote:

> I dont understand whats wrong with stretch. I run all my machines with 64 bit 
> stretch.

One thing wrong with Stretch is that it is not LTS whereas Jessie is.

Also, I have so far failed to make a working RTAI kernel for Stretch.
I think that we need at the very least an optional RTAI ISO for the
parallel port users even if we recommend the preeempt-rt version.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry machine

[Marcus Bowman]

On 24 Apr 2019, at 10:18, Les Newell wrote:

> I guess you could seal it afterwards with paint. 

Yes, but having painted MDF before, it requires a particular sealer, then 
several coats of paint, which is a bit of a pain. So its a method which is 
lower in material cost than, say aluminium, but much higher in labour 'cost'.

Marcus




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Re: [Emc-users] Vacuum bed for router Re: Servo reduction for gantry machine

[Les Newell]

I really like that idea. Getting the slope and pocket dimensions just 
right would take some experimentation but if it works it would save a 
lot of hassle. I dunno if MDF would work as a top plate though. That 
stuff leaks like a sieve, especially if you cut through the outer skin. 
I use 6mm MDF over the whole table as a spoil board and it offers little 
resistance to air flow. I guess you could seal it afterwards with paint. 
PVC foam board would probably work well though it is quite a lot more 
expensive than MDF.


Les

On 23/04/2019 22:04, Gregg Eshelman via Emc-users wrote:

Les
Somewhere I saw a very clever design for a vacuum bed for a router. The top was 
in two layers instead of simply having a bunch of holes drilled through to the 
plenum each hole had a pocket off to one side. The bottoms of the pockets 
sloped slightly downward so that a 6mm Airsoft pellet would fit and roll away 
from the hole when the vacuum was off. Lay something flat on the bed and vacuum 
would pull on it through every hole it covered but the uncovered holes would 
suck the Airsoft pellets out of their pockets to seal them. Shut the vacuum off 
and all the pellets roll off the holes.
Would be easy to retrofit atop any vacuum bed. Remove the original top plate and replace 
with 1/2" MDF. Use a 5mm drill in the router to make the hole pattern then a 
slightly larger than 6mm ball end mill to carve the side pockets. Drop in the Airsoft 
pellets then apply a sheet of 1/8" MDF and redo the 5mm drill pattern.
Then the router can do any size work without needing to have pieces of MDF, 
plywood, sheet metal etc. to cover the unused area.
   ers





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Re: [Emc-users] possibly good news for LinuxCNC

[Gene Heskett]

On Wednesday 24 April 2019 03:42:00 andy pugh wrote:

> On Wed, 24 Apr 2019 at 01:30, Gene Heskett  
wrote:
> > Several, your personal config probably makes a far bigger difference
> > than the actual version number of the kernel since you have to be
> > pretty well up on YOUR hardware to re-configure the kernel you are
> > about to build.

> And there is the problem. I have never yet managed to get that step
> right and make a version that works on my PC.
> (I tried and failed with the NTULinux repo last night)

URL?

> And the problem to be solved here is building a kernel that can ship
> with LinuxCNC and work with _any_ kernel.
>
> Is it, in fact, currently impossible to provide an RTAI LinuxCNC ISO
> with any kernel newer that the one we ship with Wheezy?

IDK Andy. Has the current rtai kernel been tried on stretch? Nah, its 32 
bit, claims PAE but is not. Stretch is 64 bit.

> If that is the case then perhaps it is time to abandon RTAI
> altogether?

Might be, I have only 1 preempt-rt versions running here, not on software 
stepping though, both on mesa cards, a 7i90HD+3 ea 7i42TA's running the 
Sheldon, and the 5i25/7i76D running the G0704. But I've not changed the 
kernel on the 6040, that machine WAS formerly softstepping the old HF 
micro so its still running the live iso's kernel. But I've no clue if 
software stepping would run on it. If I software step it, it would be  
buckets slower, 10 ipm or so rapids, where its doing 200 now.  And I'd 
have to share all my home switches for lack of i/o.

I hope at the end of the day, that we don't have to abandon software 
stepping as thats the lowest cost entry point. But for my uses, today 
I'd have to figure on at least a 5i25 as a driver card, and that 
unavoidably raises the entry bar for new users by what, 80 bucks?  A sad 
state of affairs.  Your call.
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] Looking fro some input from the community

[Gregg Eshelman via Emc-users]

What about ECP mode, which requires DMA? 
Originally the LPT port was output only, no ifs, and, buts, or inputs. Built to 
the original specs there should be no way at all to push data into the port. 
But naturally some manufacturers didn't stick 100% to the specs. Then various 
hackers figured out ways to have a peripheral twiddle four status lines on and 
off, and how to write software to intercept and interpret that status info as 
data instead of "WTH is wrong with the printer?".

Tada! An 8 bit output, 4 bit input port. Horribly slow but a way to put data 
into a PC without having to install any special hardware. IBM went on to make 
that method official, which is commonly called "bi-directional" or "PS/2" mode.
Then we got tape backups, image scanners and many other devices connecting to 
the printer port, and sections in the instruction manuals about needing to 
install a second LPT card, or replace the current one, if one's PC happened to 
have a 100% original spec LPT completely incapable of hacky data input.

Then along came EPP and ECP with their ways of shoving 8 bits at a time into 
the LPT port along with output, and doing both at higher speeds. IIRC one or 
both makes the 8 normally output pins bi-directional. Interesting that your 
research has shown that standards compliance with EPP is so bad that it's a 
wonder some manufacturer's devices work at all.

On Tuesday, April 23, 2019, 7:43:52 PM MDT, Jon Elson 
 wrote:  
 On 04/23/2019 11:21 AM, Joe Hildreth wrote:
> Jon,
>
>> I make boards that use the parallel port as a communications
>> channel for motion control.
>> These use the IEEE-1284 (EPP) mode for faster communication.
> How do you test if a card works properly in EPP mode?  This would be good 
> information to add to the list for those using your hardware.
>
>
All I am concerned with is if it works with my boards.  But, 
in the process, I learned more than I ever WANTED to know 
about EPP.  EPP is a horrible "standard", because it really 
doesn't seem to be a standard.  There is the IEEE-1284 
designation, but I've never seen the standards document, 
probably because I can't afford it.  The best thing I ever 
found was the datasheet from an old ISA-bus multi-IO chip.  
Also, there is a Microsoft document that generally lays out 
how it is supposed to work.  But, chip makers don't follow 
any of that.  The Microsoft doc shows timing diagrams with 
no numbered specs on timing.  But, at least, the data bus is 
shown as stable before the strobes are asserted.  Well, some 
chips assert the strobes FIRST, then the data FOLLOWS.  Not 
even at the same time, but the strobes come 50 ns FIRST!  Crazy!
  
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Re: [Emc-users] possibly good news for LinuxCNC

[andy pugh]

On Wed, 24 Apr 2019 at 01:30, Gene Heskett  wrote:

> Several, your personal config probably makes a far bigger difference than
> the actual version number of the kernel since you have to be pretty well
> up on YOUR hardware to re-configure the kernel you are about to build.

And there is the problem. I have never yet managed to get that step
right and make a version that works on my PC.
(I tried and failed with the NTULinux repo last night)

And the problem to be solved here is building a kernel that can ship
with LinuxCNC and work with _any_ kernel.

Is it, in fact, currently impossible to provide an RTAI LinuxCNC ISO
with any kernel newer that the one we ship with Wheezy?

If that is the case then perhaps it is time to abandon RTAI altogether?

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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Re: [Emc-users] Looking fro some input from the community

[andy pugh]

On Wed, 24 Apr 2019 at 03:01, Joe Hildreth  wrote:

> Thank you for follow up.  I have them added to the list.  One last question, 
> are these all PCI cards?

Yes, all original PCI, not PCI-e or ISA.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916


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