Speed modifier for single axis (extruder)

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01 Dec 2021 16:08 #228131 by Ameone
Hi everyone,
Hope you are all doing well and safe! A quick question: at the moment I'm working on a LinuxCNC powered 3D printer. I was wondering if it is possible to modify the speed of a single axis (the extruder) while printing (so while a gcode file is being read) without touching the other axes. Has anyone tried something similar before?
Thanks,

Amedeo
The following user(s) said Thank You: Todd Zuercher

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01 Dec 2021 17:38 #228134 by tommylight
Yes it is if it is set as a spindle, but that is not the best solution.
There is some discussion going on here, we now have "additive manufacturing" section on this forum, so i also moved the topic here.
forum.linuxcnc.org/additive-manufacturing

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02 Dec 2021 11:39 - 02 Dec 2021 11:44 #228180 by AlessandroT
Hello Amedeo,

Yes, we are currently using the A axis in this way. the secret is to use the speed mode for the A axis and delete the following errors events.
A possible solution here:

setp hm2_[HOSTMOT2](BOARD).0.stepgen.04.control-type 1 ##set the control type to velocity mode
setp pid.6.enable 1
setp pid.6.Pgain 0
setp pid.6.FF0 0


net motor.04.loopback <= joint.4.motor-pos-cmd ## note command is looped back to feedback
net motor.04.loopback => joint.4.motor-pos-fb ## so no following errors are possible
setp pid.6.enable 1

the PID FF1 pin could be linked to your variable extruder scale source
Last edit: 02 Dec 2021 11:44 by AlessandroT.

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07 Dec 2021 13:57 #228531 by Ameone
Hi Alessandro, all,
Thanks for the quick reply. I'm attaching the ini and hal files for the machine. As you can see, the extruder axis is set up with a closed loop control using an optical encoder mounted directly on the stepper shaft. The control is implemented through a PID loop, so the PID parameters are already set.
Maybe the spindle solution is better for this case?

 
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