I believe I’m having the same problem. I’ve been working remotely with @stradibarrius, helping him learn Fusion 360. He’s had numerous problems with cuts not coming out as expected, almost always with the Z coordinates being off.
So today we had a Zoom call at the machine for the first time. He homed, zeroed X, Y & Z all exactly as modeled. The Z-zero is at the spoil board, bottom of the workpiece (which is ~17mm thick). He showed me the bit position and the tablet screen showing Z=0. He then moved the bit ~100mm above the workpiece, put on the vacuum brush, loaded and ran the program (roughing w/ 1/4" flat end mill). Here are the first few lines:
N10 G90 G94 G17 G91.1
N15 G21
N20 G53 G0 Z0
N25 S10000 M3
N30 G54
N35 G0 X-106.409 Y71.02
N40 G43 Z34.43 H2
N45 G1 Z24.43 F2421.5
N50 Z17.714
N55 Z17.079 F2421.7
N60 X-106.407 Y71.028 Z16.979
N65 X-106.401 Y71.051 Z16.882
N70 X-106.392 Y71.088 Z16.79
N75 X-106.379 Y71.138 Z16.705 …
The tool entered at the correct X,Y coordinates, but plunged through the workpiece nearly to the spoil board, maybe 0.1mm shy. That’s ~17mm lower than it should be. After plowing along for a few inches, cutting through 17mm of maple, the whole machine racked and the path went badly askew just as he hit the e-stop. Sadly, we did not see what Z coordinates were showing on the tablet.
He restarted the controller, zero X, Y again, and Z to the top of the workpiece as a test. The path then ran perfectly, ~16mm above the workpiece in the air.
He re-zeroed the Z to 5mm below the workpiece, and it ran in air again as expected, ~11mm above the workpiece. Zeroed 10mm below workpiece, again fine. Then Z-zeroed to the spoil board again and it’s now running fine.
Could the restart of the controller have mattered?
The last time he ran this same G-code to completion, the result cut 3mm into the spoil board, which translates to the Z being 7mm lower than it should be. The week prior, it ran a similar toolpath perfectly, then, with a different toolpath, it plunged so far into the table that it broke a 1.5mm bit and ruined the collet for it.
The inconsistency is what’s got me stumped. Sometimes it runs fine, while other times it goes completely off the rails, but only in the Z-direction.
Could this conceivably be related to wire connections? Z Axis Changes During Cut - #6 by Dunlow
We have the latest firmware and post processor as well.
Any other theories? @akfrozen have you gotten any response from @OnefinityCNC ?
Many thanks!