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Progress update

Posted: Sun Aug 31, 2014 4:56 pm
by daedelus
It seems like it's been a while since I last had any updates so I thought I'd write this post to assure you that I am still here and still working on AutoLeveller. I also thought I would document my current tasks here.

First of all, I have been over-ambitious trying to make too many changes to Autoleveller at once for the next update and the size of the tasks slowed me down a bit. I have cut these tasks to a manageable level now and been concentrating on the arc issue recently, so what is the arc issue?

Well until the last update arc moves (G2 and G3) were not really supported. Arc moves usually worked but they weren't segmented like linear moves. By 'segmented' I mean divided into smaller bits so that the AutoLeveller can level gcode files for each segment and not just the beginning and end of a longer section.

The new updated code worked well usually, but, as was mentioned on these forums, occasionally the AutoLeveller would get stuck in a loop when performing these arc calculations. The offending gcode file always used inches as the units, and if the same file was converted to millimeters, everything worked fine. Still, users should not need to stick to millimeters if they run into a problem like this, so I have been concentrating on resolving this issue lately.

I have recently been trying a different technique where arcs are broken down into small straight line moves across the circumference of the arc and hoped that this would fixed the problem.

This is a test gcode file (millimeter units) opened in CamBam:
Original image of the vectorphone toolpaths opened in CamBam

CamBam is great for showing me what I want because toolpath types are colourised. Blue lines are straight (G0 and G1) moves, whereas green lines are arcs (G2 and G3) moves. The new code converts arcs into straight line segments, so if I take this gcode and pass it through AutoLeveller then load the AL file back into CamBam:
Converted image of the vectorphone toolpaths opened in CamBam

All the green lines are now replaced with blue ones and the image looks pretty much exactly as it did before.
Obviously, the more segmented the converted arcs are, the smoother the appearance of the converted arc (but at the expense of extra lines of gcode). This is shown graphically in the next 2 images.

This image is a zoomed in capture of the bottom left of the above image. Arc segments are set to use a 1/2 millimeter size for conversion:
Zoomed vectorphone image with arc segmentation set to 1/2mm

1/2 a millimeter looks very smooth for conversion based on this image alone.
The same area is shown here but with the segments set to 1mm:
Zoomed vectorphone image with arc segmentation set to 1mm

The converted arcs are less smooth here but probably not noticeable when milled. It might be more pronounced if the arcs to convert were much tighter and I can see other issues arising here too.

So, are the problematic inch files fixed now? and did all this fix the arc issue? No, but I did learn a lot from doing it and it has given me further clues as to the cause of the problem. If all else fails I could convert a line to millimeters, perform the necessary calculations and convert the result back to inches.

Anyway, I hope this reassures you that I have not combusted yet :) I am still working.