Circles inconsistent

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#1

Sometimes they close, sometimes they’re perfect!.. I don’t get it!
Belts are nice and tight, there seems to be no play in the head, I adjusted backlash on Y to .25 which seems to generate perfect circles with no perceptible start / end point, but if I run the same file 20 times, several will be absolutely wonky… I lubricated the rails, and even checked square… everything is dead on.

Here’s a photo… you’ll see that most are dimensionally perfect, whereas I can put the cutout back in the hole and rotate it freely with no binding… but then there’s a couple that don’t close, and even one in the middle which is oddly misshapen.

This is a brand new problem, and I’ve been playing for about 8 straight hours now, and just can’t seem to make heads or tails of it.

What could cause inconsistent cuts like this?

Thanks!

eXtRpAFA
eXtRpAFA.jpeg4032×3024 964 KB

#2

the very top row was testing various backlash settings… the bottom 3 rows are all with .25 backlash comp on the Y axis.

Thanks Guys!

#3

Well son of a B! I had one set screw on the pully down inside the gantry where I couldn’t reach it which was completely stripped, but Loc-Tite was used to hoild it in place, so it wouldn’t turn… So no matter how much I tried, it would not budge… The other? well, they drilled a hole in the shaft of the motor, and put a long set screw right into the shaft… that sheared in 2… But! It wedged tight enough so that on not one , but three visual inspections, and “tightness checks”, it eluded me. I finally just tore the whole gantry down. That’s when I found it!

Now I’m back to perfect dimensional accuracy, and perfect circles…

yay!!!

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#4

Wow. Glad you found it and got all sorted.

#5