Bro present -3d engraving

LowRider CNC Troubleshooting
#1

Spent entirely too long trying to make this for my brother Andrew (after the depicted saint). It was probably my fourth try engraving a 3d sculpture like this but the first, mostly, successful run as well as the first try where I really double checked everything. I’m happy to give it to my brother as a present, I wouldn’t be willing to sell it the way it came out. It’ll probably be redone once I get finished with some other projects. Solid birch wood from a reclaim place. I could use some advice troubleshooting. But first, the story.

PXL_20211202_022309420
PXL_20211202_0223094203024×4032 3.3 MB

Final product
PXL_20211130_025118467.NIGHT
PXL_20211130_025118467.NIGHT1512×2016 1.16 MB

hot off the mill

I wanted to try staining the sides and then sand off the tops to highlight but that didn’t go so well. Didn’t try too hard getting the stain off since I knew I wanted to redo it anyways.

Right side Z motor also seems to lower less than 2 mms over 1000’s of Z changes. I checked the grub screws, filed down the lead screw so there’d be a flat spot for the grub screws to nest in, and made sure the Z was level to start but still happened. So that’s why the top right went all of the way through, not too worried about the z drop right now though. Decided to make some hand changes by carving out more with a dremel and adding a backsplash. A happy accident :slight_smile:

And the big reason for a wanted redo are the two horizontal cuts near the bottom of the picture. I ran a 1/4" bit for a rough pass, switched to a 1/8" ball mill for the finishing and after cutting most of the bottom frame, the cnc didn’t raise up and went straight though. I stopped it, ran it back to x0,y0 and reset Z and tried the finishing pass again immediately. About 1/2 way through the bottom frame, it dug in again. Went back to x0-,y0 reset Z and then made supper for an hour. Came back and ran the finish pass at 80% speed after that, same g-code and no issues. Only thing I can think of is the Z stepper drivers over-heating (garage was 50°F, no fan cooling on the board). Any other ideas?

Roughing pass 1/4" 10mm/s, 3 mm DOC, 2 mm/s z, 85% stepover (0.5 mm left for finish pass)
finish pass 1/8" ball nose 15 mm/s, 10 mm DOC, 3 mm/s z, 15% stepover

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#2

Standard Ramps board, all hardware and electronics purchased from Ryan. Running G-code using LCD screen and SD card, no computers attached. I printed the printable pieces and did the wood parts. Series wiring all the way around.
image

#3

With series wiring, the only think that comes to mind (assuming the Zs were level to begin with) is binding leading to skipped steps, since you already checked the grub screws.

As for trying to leave high spots brighter, try sealing it and then applying some cabinet glaze. After it dries, you can wipe off the high spots.

#4

That’s a good thought. The left side goes down on its own when disabling the steppers and the right side goes down once I give the lead screw a slight twist. Could be that it gets bound up more when its got a side load though. I’ll re-lube and see if I can get both sides to lower upon disabling steppers.

I’ll try the cabinet glaze trick on a test piece and see how it goes, probably what I needed for this one :slight_smile:

Two issues down, one to go. Any theories on why both z stepper motors would cut out in different lines of the g-code? That’s my biggest concern for when I try another 3d job. (this a question for anyone)

#5

Overheating seems like a good enough answer. Since they’re series, they both stop when the driver does.

I guess bum crimps could do it, too. Maybe the wires wiggle into just the right position…

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