[Emc-users] Realtime feedrate variation based on analog sensor?

Discussion:

Jason Burton

2012-12-14 20:06:36 UTC

Hello,

Is it possible to continuously adjust feedrate along a path?

The application I am exploring is similar to wire EDM. A circuit monitors
the spark gap characteristics and provides an analog output.

Vectored feedrate would be adjusted multiple times per second based on the
value.

Hoping someone has already done an EDM in LCNC and I just haven't found
it...?

Jason

andy pugh

2012-12-14 20:11:59 UTC

Permalink

Post by Jason Burton
Is it possible to continuously adjust feedrate along a path?

Yes, there is a feed-override pin in HAL.

Post by Jason Burton
Hoping someone has already done an EDM in LCNC and I just haven't found
it...?

There is a problem with the current interpreter, it can't run
backwards, so your EDM can't back all the way out (as might be
required)

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

andy pugh

2012-12-14 20:30:00 UTC

Permalink

Post by andy pugh
Yes, there is a feed-override pin in HAL.

As others have said, I meant motion.adaptive-feed. Not halui.feed-overrde.

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

Jason Burton

2012-12-14 20:45:25 UTC

Permalink

Thank you.

It looks like a 4axis hot wire wax cutter could employ this without too
much trouble. Then feedrate would be adaptive rather than needing to prove
out each path in advance. >> faster one-offs.

Much more digging ahead.

Best,
Jason

Post by andy pugh

Post by andy pugh
Yes, there is a feed-override pin in HAL.

As others have said, I meant motion.adaptive-feed. Not halui.feed-overrde.
--
atp
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http://www.ifixit.com/Manifesto
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John Kasunich

2012-12-14 20:13:30 UTC

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There is something called "adaptive feed". A HAL pin on the
motion module, that can be varied from 0.0 to 1.0, and will
change the feedrate proportionally. It is read at the servo rate
(normally 1mS). It was added with EDM in mind.

You will need an analog input to get your signal into HAL.

Post by Jason Burton
Hello,
Is it possible to continuously adjust feedrate along a path?
The application I am exploring is similar to wire EDM. A circuit monitors
the spark gap characteristics and provides an analog output.
Vectored feedrate would be adjusted multiple times per second based on the
value.
Hoping someone has already done an EDM in LCNC and I just haven't found
it...?
Jason
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sam sokolik

2012-12-14 20:13:59 UTC

Permalink

If you can get the analog signal into linuxcnc - look at
'motion.adaptive-feed ' from here.
http://www.linuxcnc.org/docs/2.5/html/man/man9/motion.9.html

would allow you to adjust the feed on the fly - atleast 1000 times a
second :)

sam (I know of atleast one person that has used this for edm.. -
remember though - linuxcnc doesn't have a mechanism yet for backing up
along the path.. just speeding up / slowing down.)

Jason Burton

2012-12-14 20:24:05 UTC

Permalink

Fantastic!

Thanks for the starting point tips. I now have some homework to do to ask
intelligent followup questions.

Thanks again.

Jason

Post by sam sokolik
If you can get the analog signal into linuxcnc - look at
'motion.adaptive-feed ' from here.
http://www.linuxcnc.org/docs/2.5/html/man/man9/motion.9.html
would allow you to adjust the feed on the fly - atleast 1000 times a
second :)
sam (I know of atleast one person that has used this for edm.. -
remember though - linuxcnc doesn't have a mechanism yet for backing up
along the path.. just speeding up / slowing down.)

the

Post by Jason Burton
value.
Hoping someone has already done an EDM in LCNC and I just haven't found
it...?
Jason

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Post by Jason Burton
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Viesturs Lācis

2012-12-14 20:15:40 UTC

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You can use motion.adaptive-feed pin to adjust the feedrate, while
running a file.

http://linuxcnc.org/docs/html/gcode/m-code.html#_m52_adaptive_feed_control_a_id_sec_m52_adaptive_feed_control_a

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