RepRap: Blog

Time to move on to placing dots of resin configured in useful shapes. I've written some python code to take a GCODE file of a model from PrusaSlicer and break all moves below safe Z height into segments. The maximum and minimum segment lengths are controlled so that they can be set to roughly the size of a resin dot. The code then lowers the probe onto each of the points on that segment.

I put a hypodermic probe on to test it, and used this to poke at a glass slide covered in Sharpie marker:

The marker is half a millimetre - 500μm - long and made up of individual points approximately 15μm apart. Previous etched logos shown on the blog were 400μm tall.

Previously, there have been great big splats every time the probe touches the slide. These were eliminated by changing the probe movement so that it dramatically reduces its feed rate 10μm above the surface of the slide. X & Y acceleration rates were also reduced to 50μm/s/s to reduce vibration, as previously the acceleration was taxing the stepper motors giving a bumpy ride.

I think this is simply reducing vibration in the system as a whole. The probe comes to a stop on XY, then gently touches the surface, giving plenty of time for vibrations to be dampened.

The python code allows the probe to be directed into the resin reservoir after a certain number of points are touched. This is going to make for slow work, as the image above took about 25 minutes to produce. As you can see, the motion is not linear enough for my liking, but it is reasonably consistent as the individual points are adjacent to each other and not randomly scattered about. Things seem to be within 20μm of where I would expect them to be.

I hope to try this out with resin and a fine probe soon, and generate some simple solid artefacts. Positioning without surface contact has so far been more accurate.

I've added the rudimentary python code to github https://github.com/VikOlliver/RepRapMicron/tree/main/gcode_segmentation

# posted by vik-olliver @ 1:35 AM