gmane.linux.distributions.emc.user

Re: Tool Offsets

John Thornton — 2012-05-23T11:45:22

Good point, are there any two controls from different manufacturers that 
are completely portable between each other?

I know from reading my CNC g code manuals from other machines that I 
have that even generation to generation of the same controller the g 
code is not portable.

You would think that the simple G0 would be the same between controllers 
but that is not the case, some of my machines Z up before doing the XY 
move and if Z is down do the XY move before the Z move and some do a 
straight linear move...

So the question is do you cobble up your software just to be portable 
when no one else seems to do this...

Just open up the list of post processors on most cam software and you 
see hundreds of choices usually...

John

On 5/23/2012 2:48 AM, Steve Blackmore wrote:

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Re: Encoder Redundancy?

John Kasunich — 2012-05-23T11:38:06

I really like this approach, but I think one second is far
too long of a delay.

If your PID loop is saturated during normal operation, that
means you are no longer accurately controlling tool position,
and are probably making scrap parts.  So you should adjust
your accel down until it never saturates during either cutting
or rapids.  Just use halscope to look at the pid.saturated
pin while you are tuning and make sure it never trips.

Once it is adjusted so you never get saturation under normal
operation, then any saturation must indicate a problem - either
the gantry is jammed into something, or the encoder failed.
In that situation, I would have just a tiny bit of debounce
to avoid false trips - maybe 10 milliseconds.  That will stop
it before it gets going too fast.


On Wed, May 23, 2012, at 10:25 AM, andy pugh wrote:

Re: G04 dwell in seconds not milliseconds?

John Thornton — 2012-05-23T11:36:02

You might  reference the g code manual for LinuxCNC rather than guess or 
assume LinuxCNC G code is the same as some other control.

John

On 5/23/2012 12:35 AM, Claude Zervas wrote:

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Re: G04 dwell in seconds not milliseconds?

charles green — 2012-05-23T11:25:13

isn't T one of the modern coordinate axes as well?

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Compiling APT [Was: Need Help from U.S. Users & Companies - APT (Automatically] Programmed Tools)

Erik Christiansen — 2012-05-23T11:04:05

The minimum-effort "port" to linux might just be to shove it through
gfortran, the fortran version of gcc, avoiding entirely the task of
translating the source code to another language. As can be seen here:

http://gcc.gnu.org/fortran/

Legacy code support right back to fortran77 might be a stretch,
requiring some dusting of cobwebs off the APT code base.

Although I haven't built gfortran, I see a lot of fortran testcases, and
"info" documentation for fortran in the gcc sourcecode, which is
encouraging.


Ahhh, I remember doing that as a student, while trying to expand my
limited understanding of the documentation on common blocks. The uni
lecturers were a fat lot of help once you went beyond the syllabus, to
do anything unusual with the language. Mind you, that was back in 1973,
so we didn't even have fortran77 then.


Then gfortran might really be worth a close look, since it has moved
forward since last century:

»Compiler capability is quite extensive and includes nearly all g77
features. We highly en

Re: G04 dwell in seconds not milliseconds?

andy pugh — 2012-05-23T09:53:14


The glib answer is "because that is how the programmer coded it". I
suspect that the G04 code has been unchanged for a long time.
A quick Google shows that some controllers use seconds and some use
milliseconds, and some let you choose. (And a mention appears on the
LinuxCNC Wiki of an Okuma controller that uses hundredths of seconds).


U and X can't be used as these are axis position commands.
LinuxCNC could be changed to accept an INI file setting to set the
time unists in much the same way as it is possible to set the linear
units, but I don't expect there is anyone queuing up to make that
change. If you fancy doint it yourself, though, perhaps you could get
a patch accepted.


I think that you will need to have different options for different CNC
controllers. (As all the other CAm packages do). Unfortunately the
G-code standard is not very standard.

Re: Encoder Redundancy?

andy pugh — 2012-05-23T09:25:45


It should be possible to check if your PID is saturated for more than
a second or so.

loadrt debounce cfg=3
addf debounce.0 servo-thread

setp debounce.0.delay 1000 #1 second delay in a 1uS servo-thread

net x-check debounce.0.0.in <= pid.0.saturated
net y-check debounce.0.1.in <= pid.1.saturated
net z-check debounce.0.2.in <= pid.2.saturated

net x-fault debounce.0.0.out => axis.0.amp-fault-in
net y-fault debounce.0.1.out => axis.1.amp-fault-in
net z-fault debounce.0.2.out => axis.2.amp-fault-in

Note that I am not sure what amp-fault-in actually does, but it was
conveniently available and sounds about right.

Re: Intel DN2800MT - possible new LinuxCNC star?

Claude Zervas — 2012-05-23T08:56:54

cool, thanks Yishin.  I don't yet have a BeagleBone but I would like
to shrink my whole setup, so I will eventually try this out.
- Claude

On Wed, May 23, 2012 at 12:41 AM, Yishin Li <ysli-FmnknHxwANugSpxsJD1C4w< at >public.gmane.org> wrote:

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Re: Power and data cables for CNC

Viesturs Lācis — 2012-05-23T08:09:03

2012/5/22 gene heskett <gheskett-ouEgS7marmk< at >public.gmane.org>:

I used them in my last machine - shielded multistrand CAT5 cable. The
price was much higher than "normal" CAT5 cable...
I have a leftover at home. If I remember, I could try to find that
little printing on the outer insulation for exact code by the end of
the week.

Re: Encoder Redundancy?

Jeshua Lacock — 2012-05-23T08:05:44

On May 23, 2012, at 2:01 AM, Claude Froidevaux wrote:


Hi Claude,

Sounds great, thanks!

Is there anyway you can show me a hal sample or point me in the right direction?  I don't have much hal experience at all.


Thanks again,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated
<http://3DTOPO.com>
Phone: 208.462.4171


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Re: Encoder Redundancy?

Claude Froidevaux — 2012-05-23T08:01:30

1)  make a hal check, that disable drive if more than 5-10 consecutive 
sample period with maximum drive output without any encoder change

2) if you use a hal encoder (brushless motor), use it as second encoder, 
and cut motor power if more than about 20° of error between both

theses are not perfect solution, but are quite simple.



Le 23.05.2012 08:08, Jeshua Lacock a écrit :


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Re: Encoder Redundancy?

Jeshua Lacock — 2012-05-23T07:56:12

On May 23, 2012, at 1:11 AM, Roland Jollivet wrote:


Hi Roland,

Interesting idea. The only downside of something like this is that I would lose 6 inches of machine space, so it would be better if the motor never even ran away in the first place.

Jon, can your power switch and braking module (and/or the brake on the Gecko Interface) be used like for something like this?

http://pico-systems.com/osc2.5/catalog/product_info.php?cPath=3&products_id=24


Thanks,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated
<http://3DTOPO.com>
Phone: 208.462.4171


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Re: Intel DN2800MT - possible new LinuxCNC star?

Yishin Li — 2012-05-23T07:41:01


Our repositories are at github. Please refer to this wiki page to access it:
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?ArtekBranch

The BeagleBone related modifications are at "beagle" branch.
I will prepare documentation about installing Ubuntu on BeagleBone.

Yishin

Re: Tool Offsets

Steve Blackmore — 2012-05-23T07:48:55


Portability of Gcode between different controls. 

Steve Blackmore
--

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Re: Encoder Redundancy?

Jeshua Lacock — 2012-05-23T07:42:53

On May 23, 2012, at 1:36 AM, Lester Caine wrote:


Hi Lester,

I am not *sure* what wire was loose, but I *suspect* that the encoder lost power….


Best,

Jeshua Lacock
Founder/Engineer
3DTOPO Incorporated
<http://3DTOPO.com>
Phone: 208.462.4171


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Re: Encoder Redundancy?

Lester Caine — 2012-05-23T07:36:46

I would have thought that if the motor turned more than 1/2 a turn or so but the 
encoder feed produced no pulses then this would be an easily detected error 
condition? If you are getting pulses from one channel only, then that is very 
easily detected ...
Surely a 'runaway' like this SHOULD be handled by the servo driver?

Is there a market for a module to monitor the two encoder feeds and us it in 
conjunction with either the index pulse or an extra source that indicates that 
the encoder should be giving output?

Encoder Redundancy?

Roland Jollivet — 2012-05-23T07:11:19

I'm no expert on this, but I think there should be a secondary limit switch
connected to a relay and a power resistor. If this is activated, it will
connect the motor directly across the resistor. The resistor should be
matched so that the motor will halt in two or three inches from full speed.
This would be a safegaurd outside any electronic control.

Of course, this would only apply to DC motors, but for AC motors you could
have a similar set-up with a DC power supply.

Regards
Roland
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Servo system and glass encoder scales for positionfeedback

Roland Jollivet — 2012-05-23T06:59:12



Thanks. And a curved ball;
Does the rotary encoder really have to be in sync with the linear scale?
I'm thinking of a small encoder that is geared up, off the motor shaft
(tenshioned/no backlash)

So now you have the rotary resolution, but the software would need to keep
zero-ing this counter, as it will have a poor tracking relation to the
linear sclae, but always yield maybe 5x the linear scale in resolution.

Regards
Roland
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Re: Increase Damping

Jeshua Lacock — 2012-05-23T06:46:24

On May 21, 2012, at 10:36 AM, Jon Elson wrote:


Thanks Jon! 

I am actually going to wait until I get the new 5:1 gear box installed before I tune things further, but there is one last thing I don't really have a grasp on.

It felt like I wanted to get P set as high as I could. Is that correct? Or as long as P is high enough to command the machine to move is that adequate?


Got it, thanks!


Thanks! So I use the ground from either the USC or Gecko?


Good to know! I guess I will set it for 1024 (instead of 2048) to start.


Also good to know!


Thanks for the most understandable explanation of I that I have read yet!


I see. Currently, since I am only using pulleys with timing belts (no gears or lead screws per se), I was under the impression that backlash is nearly non-exisistent. Is that true?

My z-axis is pulleys with a ballscrew.

Of course as soon as I install the 5:1 gearbox on my X (hopefully here tomorrow) then it will have some backlash (see below).


Got it.


Good points.


Actually the gearb

Encoder Redundancy?

Jeshua Lacock — 2012-05-23T06:08:12

Greetings,

I turned on the power to my system today and my 180 pound gantry shot full speed crashing hard into the end of my table.

It hit with so much force it actually lifted the front two legs of the 500+ pound table 6+ inches off the floor! Yikes!

Luckily the machine only suffered minor damage, but needless to say I really would like to avoid this from ever happening again.

I was a stumped at first as the last time I used it everything was stable. It turns out that I had a loose connection to the encoder. I am going to soldier the wires on the pins of the encoder to prevent that from happening again, but I was wondering if there is anything I can do to disable motor power in the event a connection to a encoder is lost.

I understand why it happened - without the encoder live the motor was just attempting to position itself at 0.

I am guessing there is not an easy way to detect this condition, but I wanted to see if anyone else has any thoughts on the subject.


Thanks,

Jeshua Lacock
Founder/Engine

Re: Power and data cables for CNC

Rafael Skodlar — 2012-05-23T06:00:40

There are different kinds of stranded CAT-5 from my experience. However, 
stranded cat-5/6 were not designed for bending over and over thousands 
of times IMO. Connecting laptops is one thing, wiring sensors and 
electronics on moving mechanisms on CNC machines is another.

I've come across multi-wire cables with "magic white powder" inside 
which made bending much smoother. Insulated wires inside main cable 
jacket were sliding along each other easily. I did not pay attention to 
that at that time but now I suspect I know what that was all about.