Correcting horizontal banding (on other printer) in gcode
Posted: Thu Oct 05, 2017 3:53 pm
Hello,
I've been commissioning a homebrew large format printer for a couple months now, pulling my hair out with redesigns to fix various mechanical issues as I go. This has nothing to do with the M2, but I thought people might be interested.
The machine in question is large (24" square build surface) and I went with a 4 linear shaft + 4 leadscrew arrangement belted to 2 motors. Learning an alignment/setup process has been painful and hindsight is 20/20, but long story short I have a periodic error in the Z movement which is likely due to eccentricity of the pulleys. Using a digital drop indicator revealed a periodic deviation of -.013mm to .042mm from the nominal Z movements with a period exactly equal to the leadscrew pitch.
This causes a fairly extreme degree of horizontal banding in my test prints and needed to be corrected.
I had already redesigned the Z motion system once, and considering the error is predictable, I wrote a simple Python script to post-process any gcode I run to imprint a negating deviation, being sure not to exceed the Z step resolution (5um in my case). This also required that I clock the leadscrew pulleys to be synchronized.
Anyway, here's a print without correction:
And with:
See here for a couple more photos: http://lightsmithscientific.com/justine … dingFixer/
For me this is a temporary solution, but if anyone has a need I went ahead and put the code on GitHub: https://github.com/jhaupt/ZBandingFixer
~Justine
I've been commissioning a homebrew large format printer for a couple months now, pulling my hair out with redesigns to fix various mechanical issues as I go. This has nothing to do with the M2, but I thought people might be interested.
The machine in question is large (24" square build surface) and I went with a 4 linear shaft + 4 leadscrew arrangement belted to 2 motors. Learning an alignment/setup process has been painful and hindsight is 20/20, but long story short I have a periodic error in the Z movement which is likely due to eccentricity of the pulleys. Using a digital drop indicator revealed a periodic deviation of -.013mm to .042mm from the nominal Z movements with a period exactly equal to the leadscrew pitch.
This causes a fairly extreme degree of horizontal banding in my test prints and needed to be corrected.
I had already redesigned the Z motion system once, and considering the error is predictable, I wrote a simple Python script to post-process any gcode I run to imprint a negating deviation, being sure not to exceed the Z step resolution (5um in my case). This also required that I clock the leadscrew pulleys to be synchronized.
Anyway, here's a print without correction:
And with:
See here for a couple more photos: http://lightsmithscientific.com/justine … dingFixer/
For me this is a temporary solution, but if anyone has a need I went ahead and put the code on GitHub: https://github.com/jhaupt/ZBandingFixer
~Justine