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Author Topic: Circles Not Round  (Read 628 times)

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Circles Not Round
« on: December 24, 2018, 06:33:14 PM »
My circles are OK vertically and horizontally but diagonally across they are off . Re-did my steps per inch.Its  OK, if I tell the machine to move one inch it moves one inch x and y . Very confused . Really wish the search function worked. Please Santa for Christmas fix the search function.
Re: Circles Not Round
« Reply #1 on: December 24, 2018, 08:08:39 PM »
Try cutting the hole thru the work piece then just profile the hole and make 2 or 3 passes and see if the hole gets more round. If so your machine is flexing and a few spring cuts "fix" the problem.

How far out is the profile? .0005? or more like .003 inches off?

Offline Sam

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Re: Circles Not Round
« Reply #2 on: December 25, 2018, 12:03:43 AM »
Usually when you have errors that are 180 degrees apart, it's an indicator of backlash. The machine gets under a load and 'pulls' the lash out, then when it gets around to the opposite side it 'pushes' the lash out. My older machine does the same thing at 10 and 4 'o clock positions. I do what Steve suggest and do a couple spring passes, and it never gets under enough load to push or pull the lash. When this no longer works, or I get so sick of fighting it, it's time to do proper maintenance and fix it.
"CONFIDENCE: it's the feeling you experience before you fully understand the situation."
Re: Circles Not Round
« Reply #3 on: December 26, 2018, 10:27:00 AM »
If you use servo's you should cut a circle clockwise and another one counterclockwise. If the elliptical error changes the direction from one circle to the second then you should check the proportionally factor's of your PID controller for x and y axis and equalize them.
If the elliptical direction doesn't change you maybe have a squarenesserror between x and y axis.