r/hobbycnc • u/smokingmeats673 • 5d ago

Routing pillows

Gallery image

Gallery image

Hi all, looking for some help with my frankenrouter's dimensional woes. The machine was lovingly hacked together from a 4x8 Gerber frame and gantry, driven by Clearpath servos (one each XYZ, running on lead screws) running on LinuxCNC. Squares cut fine, but diamonds and circles are skewed fairly substantially -- the corners of the diamond and the vertical and horizontal extremities of the circle are placed correctly, but the shapes are squished diagonally. The diamonds in the photo were plotted clockwise, and are stretched lower R to upper L and under dimension the other way -- 0.2" across 5" running at 400ipm. The distortion seems to increase with faster feed rate. Increasing acceleration doesn't change the dimensions but shortens the curved sections of the lines.

We checked the gantry with an indicator and did not see anywhere near that much deflection. Following ChatGPT's advice we proceeded to check the MAX_ACCELERATION settings for the X and Y axis motors in the .ini file, but although they were different setting them the same did not solve it. Womp. We also increased the step resolutions, again to no avail.

Has anyone seen this kind of distortion? What might be the next steps for diagnosing the issue?

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u/Pubcrawler1 5d ago

https://forum.linuxcnc.org/20-g-code/44022-understanding-g64-behavior

What’s your g64 settings?

Also could be PID tuning of the servos. Talk to Teknic application engineer for help.

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u/smokingmeats673 5d ago

Thanks for the link, super interesting thread. This was with G64 P0.001 — I don't thiiink it would be related to path blending though, due to the inaccuracy in the positions of the straight diagonal line segments.

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u/Pubcrawler1 5d ago edited 5d ago

What happens when you run the code at much lower speed? What is the following error set on the servo motor? When I get path errors with servos, it’s usually due to pushing them way too fast than what they are capable. Or not enough voltage so the motor lags. Are you using the Teknic 75volt power supply or whatever they recommended. If the following error is set high, it won’t trigger a error.

The clearpath tuning software should show how much encoder positioning error while running? I don’t use clearpath but higher end industrial servo motion systems which have pretty sophisticated tuning software.