Milling machine retrofit
- John252058
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19 Jan 2015 07:25 #55156
by John252058
Milling machine retrofit was created by John252058
My Maho MH 600 milling machine had a Heidenhain TNC 135 control that controlled the 3 axis through clutches driven from a common drive motor. The machine is a simple point to point with no contouring capabilities.
My questions, can Linux control a single drive motor for the axis feed and positioning while using the 5v ttl linear encoders for closed loop position feedback. How can I accomplish this and what hardware would be required.
My questions, can Linux control a single drive motor for the axis feed and positioning while using the 5v ttl linear encoders for closed loop position feedback. How can I accomplish this and what hardware would be required.
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20 Jan 2015 05:57 #55190
by cmorley
Replied by cmorley on topic Milling machine retrofit
So this is a machine that uses a single motor for all the axis, using a clutch to engage each axis?
I could imagine how to do this with an open loop stepper but a servo motor...
Somehow one would need to fool the PID to the axes that are not moving to ignore the change in feedback position.
or to be able to reset the encoder counter to the count the axis is expecting...
that almost works as the linear encoder would keep the proper count for each axis - it's the motor encoder that is still the probblem.
Hopefully Andy P will look at this and advise .. he is very good at these kinds of problems.
Chris M
I could imagine how to do this with an open loop stepper but a servo motor...
Somehow one would need to fool the PID to the axes that are not moving to ignore the change in feedback position.
or to be able to reset the encoder counter to the count the axis is expecting...
that almost works as the linear encoder would keep the proper count for each axis - it's the motor encoder that is still the probblem.
Hopefully Andy P will look at this and advise .. he is very good at these kinds of problems.
Chris M
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- joshua.stephens
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18 Mar 2015 04:16 #56964
by joshua.stephens
Replied by joshua.stephens on topic Milling machine retrofit
Is it possible to interface at the post-clutch level and install 3 separate motors? Motors are pretty cheap nowadays.
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18 Mar 2015 06:36 #56968
by emcPT
That seams the best solution in my opinion and you would have a full cnc center.
Replied by emcPT on topic Milling machine retrofit
Is it possible to interface at the post-clutch level and install 3 separate motors? Motors are pretty cheap nowadays.
That seams the best solution in my opinion and you would have a full cnc center.
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18 Mar 2015 21:14 #56983
by andypugh
It would be far, far, better to install three separate motors and increase the capability of the machine. But...
The problems to solve seem to be:
1) Working out which axis is moving to operate the clutch and to choose logic. There is an axis.N.unlock pin, which is intended for locked rotary axes. I don't know how this pin operates and whether it exists for XYZ too. I think an experiment would be required.
2) "Bumpless transfer" of control from one axis to the next. If each axis has separate position feedback then this is probably fairly easy. If the axes all share a single encoder on the motor then it is a lot less easy.
I think I would configure with a separate PID for each axis and only connect the output to the motor (with a multi-mux) when the clutch of that axis was engaged.
Making sure that the G-code never tried to move more than one axis at a time might be a good use for the LinuxCNC input filters. This could auto-check for valid G-code. You would also have to reject arc moves.
So, first step... Fire up a simulator and se what the axis.N.unlock pins do.
Replied by andypugh on topic Milling machine retrofit
My Maho MH 600 milling machine had a Heidenhain TNC 135 control that controlled the 3 axis through clutches driven from a common drive motor..
It would be far, far, better to install three separate motors and increase the capability of the machine. But...
The problems to solve seem to be:
1) Working out which axis is moving to operate the clutch and to choose logic. There is an axis.N.unlock pin, which is intended for locked rotary axes. I don't know how this pin operates and whether it exists for XYZ too. I think an experiment would be required.
2) "Bumpless transfer" of control from one axis to the next. If each axis has separate position feedback then this is probably fairly easy. If the axes all share a single encoder on the motor then it is a lot less easy.
I think I would configure with a separate PID for each axis and only connect the output to the motor (with a multi-mux) when the clutch of that axis was engaged.
Making sure that the G-code never tried to move more than one axis at a time might be a good use for the LinuxCNC input filters. This could auto-check for valid G-code. You would also have to reject arc moves.
So, first step... Fire up a simulator and se what the axis.N.unlock pins do.
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26 Mar 2015 09:28 - 26 Mar 2015 09:28 #57200
by jmelson
Jon
Replied by jmelson on topic Milling machine retrofit
The question you SHOULD be asking, is why would you WANT to do this? Get rid of the clutches, install 3 motors, and make it a full 3-axis machine. Doing it this old Heidenhain way is really awful, and 1960's tech.My Maho MH 600 milling machine had a Heidenhain TNC 135 control that controlled the 3 axis through clutches driven from a common drive motor. The machine is a simple point to point with no contouring capabilities.
My questions, can Linux control a single drive motor for the axis feed and positioning while using the 5v ttl linear encoders for closed loop position feedback. How can I accomplish this and what hardware would be required.
Jon
Last edit: 26 Mar 2015 09:28 by jmelson.
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