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Posted by Techman2930 
July 29, 2021 12:34AM
Hi All, I'm a 40+yr vet of developing hardware and software for automated equipment, CNC, Pick&Place, Etc. Lately I have been purchasing Duet PCAs with RepRap Firmware loaded for motion control applications.

The Only thing I can't find that I need on every application is an equivalent to "FEED HOLD". What I mean by feed hold is, during any movement pressing feed hold decelerates all motion in a coordinated fashion. leaving the spindle going. when a continue button (sometimes the same feed hold button) is the machine Accelerates in a coordinated fashion from where it left off.

I do realize all of this was originally designed for printing but these controllers are proliferating into many other applications.

As far as I have observed this function is a hardware feature of CNC equipment. I do not know of a G or M code for this function

How can I accomplish this? I can't be the only one needing to pause motion.
Perhaps using an I/O bit and an addition to the firmware.
July 29, 2021 08:59PM
I think M0 does what you want. At least it does on GRBL, which I use all the time on my mini-mill. Marlin is derived from GRBL, so it probably works the same way there, although I haven't actually tried it. I have no experience with RepRapFirmware, but from the documentation it sounds like it's the same.

I don't know if it has support for physical buttons though. On GRBL you can use the A1 and A2 pins on the Arduino to pause and resume (they are pulled high, so drive low to activate). But I don't know if Duet/RRF has any similar functionality built in.

Edited 2 time(s). Last edit at 07/29/2021 09:55PM by dekutree64.
July 30, 2021 03:03PM
M0 stops at the completion of a move. This works well on a print where the moves are all short. Some times with CNC and robotic equipment you need or want to decelerate during a long move, do something and accelerate and continue the motion.
November 25, 2022 03:13AM
You can get a reasonable approximation of feed hold by enabling segmentation in RepRapFirmware using the M669 command. True feed hold on planned for version 3.5 of RRF.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
November 28, 2022 01:49PM
dc42, Thank You ! Thank You ! Thank You !
I will give segmentation a try until FEED HOLD is implemented.

Edited 1 time(s). Last edit at 11/28/2022 01:50PM by Techman2930.
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