Z-Depth Trouble

[jTr]

Questions and points not yet addressed:

Did the previous owner have these issues ? Sounds like they are actively helping you, assuming they're decent enough to help = they'd let you know, right(?)
If you're confident it wasn't a previous issue, you should completely review your assembly steps at current location.
Is this the same plenum, or did you make a new one? If it's bending in your shop, it must have in previous owner's. If no = look somewhere else.

You've verified steppers are responding correctly, post-processor is correct, yet we're still having issues. Indeed, spoil board with vacuum is not the same as loaded table, but we all do this without experiencing these alarming amounts of variation.

Not yet discussed; V-rollers and gantry mechanical contacts with rails. If the V-rollers are not tight consistently all along the rack, some twist may be happening. Both your images suggest table is thin and flexing, or V-rollers may have a few areas of loose contact, as in gantry may have a slight twist. This can look good in a cursory check in one place, so you need to pull covers and examine travel full distance - disengage steppers for this so it may freewheel and reveal any variations in contact. Look for light and carefully try spinning v-rollers by hand to see if one is popping a wheelie somewhere along the line. Gantry end carriages typically need to be re-squared to cure this, and a recent move certainly could have an effect on this.

Footnote: while re-surfacing is being trusted to generate 100% flat surface, it cannot be trusted as so if the V-rollers are loose. Two different sized bits with different geometry and a loose wheel = chaos.

Good luck - we're racking our brains and hoping for victory with you!

Jeff

[BoilermakerAndy]

Hey Red. That very well may be the case. My vacuum numbers are very similar covered vs. uncovered. Also, I just noticed that the v-shaped support under that area is missing all the bolts on one side.

I have not done that, Bill, but will try it. Either way, I'm planning on completely re-doing the table. Until then I'll just cut everything deeper than is necessary.