Wierd Z stuff

i have noticed a discrepancy in my z cut depth…

before i go on, i have a freshly skimmed wasteboard, run my calibration routines, adjusted stepper values, checked pulley set screws etc… literally all the SOP’s.

what’s odd is how the machine is responding to Stepper calibration.

for reference, i cut an assortment of small shapes, lines, etc at a .740 DOC.
first try landed them at .754…

using the online calculator that’s been posted here, adjusted the stepper values accordingly and ran it again.

second time it went .711"… so i went back and forth thru this routine for about an hour.

i finally just started spitballing values and was able to get .738" which is close enough for 99% of what i do.

then, on an actually cut project i noticed that one or two of the pockets had inconsistent cut depths within one pocket. like, the middle 30% of the pocket cut thru cleanly, whereas the outer 70% was up to .010 left.

no ragged, feathered edges, just cleanly cut in some places and remaining material in other places.

would a damaged delrin nut be a possible cause? i’ve checked and verified everything else i can look at without breaking down the machine. I’ve been pushing the machine pretty hard in the last couple months, and it has had its share of major operator errors over the last couple years.

I’ve looked on the Inventables store, and it looks like the nut is available in a set with the leadscrew, but not seperately…

just curious as to what the experts think?

Given the SOP steps you’ve taken, it sounds like it could be a material thickness descrepency. Obviously some materials vary a great deal, while others are more consistent.

i thought about that, but these were cut in 10x10 squares cut from the same sheet of MDF, just before i tried my test parts. and the Z zero is the same no matter the thickness. so, in one pocket, it should either cut all the way thru the whole thing, to the wasteboard, or maybe leave a thin layer uncut.

another cut had places where the cutout (outer profile) was shallow in places, and gouged the wasteboard in others… like, i literally resurfaced the wasteboard 10 minutes before i started running these checks

I’m sure you’ve checked this but I had an issue with the nut on the very top of the lead screw wasn’t tightened all the way down and this gave some slop in the z axis. Can you physically move the router up and down in Z at all?

yeah. mine’s tight as a drum. i guess i am going to have to break it down and see what’s going on.

I’m thinking the last marathon session of 7075 aluminum may have boogered something up.

For what it’s worth, I had an unpleasant experience after flattening my wasteboard. I assumed it to be flat, but it wasn’t.

What about the spindle itself? Can you move the shaft up and down?

Yes. all motion assemblies move freely, but there’s just something odd where the bit is twitching up and down occasionally on a flat cut.

SPINDLE END PLAY is what I was questioning.

sorry. I thought you were talking the. from wha ti can tell, the bit moves vertically only as much as the gantry deflection. not in the armature of the router itself

Take out the router. Loosen the screws holding the nut. Twist nut slightly - hold, and snug screws back down. Apply some dry lube to screw. Run Z up and down a few times. Replace router and test carve. Results same or better?