Gaining Z height when cutting many of the same parts

I’m running a production of say 100 of the same exact part. 1/8 plywood with 1/32 depth of cut if that maters. Start up the machine, set the Z with the probe, run a few parts, everything is fine. After 5-10 parts, it seems to lose some Z depth to the point where it does lighter passes, then doesn’t even cut at all for the first pass (doing 0.022 depth per pass).

It’s gotta be a hardware issue, I’ve checked everything. Bit collet is tight. Belt and set screws on the Z is tight. It’s baffling and usually this issue is in the opposite direction, bit getting closer to zero.

How accurate are the stepper motors? Like if I ran a program that had the Z go up then down 1,000 times, how close would it be at the point of origin when finished?

I’ve been having to redo the Z probe every few parts and it’s really slowing me down.


I’m not positive this is a ln issue, but worth mentioning for you to check… is it possible that the z is mounted too high and is loosing steps when it hits the lower limit of travel? You can test this by seeing it that bit will reach your wasteboard with manual jog commands …

With the new version z axis, its quite common for it to be installed too high…

Also, if $1 is not set to 255, then the steppers can do weird things when they relax, usually gravity makes it lower, but its possible to relax towards the other direction as well and raise up…
If yoh haven’t done it yet, i suggest this process to lock the steppers.

Z is mounted maybe 3/16" below the carriage. No problems reaching the wasteboard.

$1 is set to 255, only have sagging issues when the machine is off overnight.

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so, you’re carving on .125 plywood. I’m assuming that you’re checking the thickness of each piece.

I’m assuming that you cut all your parts to size and made a few stacks/piles of parts. if that’s the case the parts at the top of stack/pile are thicker than inner part of stack/pile. moisture in the air would cause this to happen, not a problem with your machine. bag your wood parts.

I’ve been checking every so often. Always within a couple thou of 0.125 inches. The panels are pretty dimensionally stable. Hydroscopic expansion of plywood is in the order of like thousands of a mm per mm of thickness. There’s probably more slop in my Harbor Freight micrometer than these things are moving. Heck, a bit of dust under the part would cause more movement.

If wood movement was the case, then it wouldn’t be repeating itself every 5 or so parts out of the stack. It would happen first thing in the day, then the rest of the supposed dryer parts would run fine once recalibrated. This isn’t happening.

Sorry, I have to ask this as I did not see explicitly written down: your surface is perfectly perpendicular to the Z axis, right? So if you go to the 4 corners of your work piece, and do manual jogging, same Z value when you touch the wood, right?
How much offset are we talking about? Your part to carve is 800 um deep (1/32"). How many steps you have? If you have 8, then each run is as thick as a piece of regular mail paper (100 um). Check with a piece of paper all 4 corners if you leveled your material with that precision.