Hi Everyone,
Been a hot minute since I’ve been on the forum and I have a bit of an interesting (I think) case to present for troubleshooting.
TLDR: I am making my second multi-carve epoxy sign (1st effort was Okocim sign below), but I’m on my 3rd of 4 CNC rounds and have experienced around a 0.3 in (~7.72-7.78mm) shift in the Y axis of the toolpath.
Background:
- A few months ago I did an unconventional thing with my spoilboard - I cut a strip between 8-10mm off the back, and then used my table saw to square the front edge. Then I glued the strip I cut off the back to the front edge - this effectively shifted what would have been lost useable space due to the quick swap + bracing kit into the carveable area.
- The result has been additional space and repeatable positioning - I can move the platform all the way back on the Y axis and if I have stock flush with the front of the spoilboard I only have to move the platform up 1mm for perfect front alignment in the Y direction. This is a tremendous help to know that even bits of different sizes will still be centered on the same Y position.
- With the Okocim sign, I learned I can remove the entire spoilboard with stock attached to do sanding or other things non-SM related without risk of damaging the machine or working around the rails. The quick swap makes this perfectly repeatable and alignable.
Problem:
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I modeled my second sign in Fusion (below) and planned each stage like I did with the Okocim sign - keep in mind that the stages are carve → epoxy fill → repeat. I even removed the spoilboard and replaced it a few times in the process, same repeatability as before (actually I may not have removed it until after the 2nd stage, I cannot recall).
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This time I switched modules to the laser, made a memorial item, then switched back to the CNC. I set my origin coordinates back to the exact position I used for the 1st two stages (machine coords 166, -3, 96.3 for the endmill I was using) and when doing a test run (10mm above the piece), it looked like it had shifted. Thinking I must have done something wrong in Fusion, I verified that the models are indeed aligned appropriately in related to one another and my setups for each body are identical.
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After running the test several times, and even restarting the snapmaker to ensure it rehomed before starting the job, I eventually decided to go for it and “trust” what Fusion was showing me would end up correct on my SM.
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Alas it did not:
In this image the top of large pocket should have been within 1.7mm of the gold area (this is what would have been vcarved by my 60 degree vbit after the pocket was done). You can also see the gap at the bottom of bare wood that went beyond the bottom of the bottle - ignore the larger black epoxy puddle in this area, overfilled it.
Similarly you can see the gaps in the pockets for these top carves that should not have intruded on the gold outline. The vbit follow-up was supposed to jsut touch the gold outline but the pockets have shifted downward.
I will confess I am utterly stumped as to why this occurred, and have no idea if the issue is from the Fusion gcode, or the SM.
My origin point on the SM was 100% the same as the other carves, and the models look perfect in Fusion. I have no idea why everything would shift down a little more than quarter inch, almost a 3rd of an inch.
But I elected not switch bits and do the vcarve because that would make the sign unsalvageable. If I had tried carving the outlines of the letters on the label and it was as far off as the pockets are, I’d have to scrap the entire thing.
Any thoughts? Thanks everyone in advance!