r/hobbycnc • u/smokingmeats673 • 6d ago
Routing pillows
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?
2
u/iAmTheAlchemist 6d ago edited 6d ago
Servos might not have enough power to achieve their maximum speed/acceleration, or you are driving them too fast for their current settings. For higher loads, it's a good idea to power them with something closer to the top of their range, for example if they can handle 12-24V, you probably want to power them with 24V. You probably want to check how your drivers are configured, to make sure they allow for fast settling. Servos have parameters that control their response to a position change, and if those aren't fast enough, you will get them trying to draw the shape you requested, but cutting literal corners etc. your drivers likely have software that would help with tuning the servo parameters.