Weird y-axis business

Machine: Chinese K40

Board: C3D

Firmware: Smoothie

Problem/ Question: I am having some difficulties when doing a “Fill+Line” as well as a “Line”. The machine gets all excited and starts lasering all over the place on the y-axis. It appears to be some slipping when the head tries to accelerate to the next line spot. I dropped the cut speed WAAAAY down, but it is in the acceleration between cuts that the issues arise.

I realize that this may be a general laser issue and not a C3D issue, but I have been reducing some of the speeds on the C3D firmware and it seems to be helping somewhat. I am getting close, but I cannot get a fill+line to work together…

The fill works perfectly and repeatedly with no skipping on the y-belt, but as soon as “line” is on, we are a mess.

Is there an acceleration that I can adjust in the firmware settings?
Has anyone seen this before?

Thanks all.

Yes, there are per-axis acceleration settings you can tweak to try and get better performance out of your machine. I suggest setting it to 500mm/sec^2 to start, then increasing in 500mm/sec^2 intervals until it begins to skip again, then go back and cut your intervals in half. I’ve found that five-pointed stars are good at making machines skip, especially at high rates.

Look for the section in the config file labeled:

# Stepper module pins ( ports, and pin numbers, appending "!" to the number will invert a pin )

If not already present, alpha_acceleration, beta_acceleration, and gamma_acceleration are your X, Y and Z acceleration values. Also of note a few lines above that section is the global acceleration value; when you find values that work for your particular axes, set this value to the maximum of the three to ensure acceleration never goes above your set maximum.

Also ensure your motor currents are set properly - it’s usually a combination of motor current and acceleration that causes these sorts of problems.

Good luck!

Brilliant. Thank you. I needed to put then acceleration down to 300 for it to work properly. It is still right on the edge. It seems to be the circular line cuts for me that cause the grief. Small letters like “G” and “O” seem to create a centrifugal force as they are whipping around the letters.

Thanks for the help @loather.

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I’ve found ‘e’ and ‘o’ to be problematic, though it’s somewhat direction dependent (i.e. in my testing with Lightburn left-to-right paths derived from text worked better than right-to-left paths).

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