Milling a hole - and a hole creeps

Hi all,

I apologise if this has been covered elsewhere, but I don't even know if I'm using a proper terminology for the problem.
So here's the thing - I have new Wabeco mill, linear rails/ballscrews, 2kw motor, comes from factory with Nema 43 6 amp steppers, 1:2.5 ratio - German engineering and in house manufactured. I have my electronics package (Centroid Acorn, Gecko 201X drives), machine is precise, backlash is a few microns and everything is looking generally nice.
However, milling a hole makes a hole creep along x - conventional milling to the right, climb milling to the left. It happens only on X axis. Otherwise hole dimensions are good and no matter what I do (speeds/feeds/acceleration).
Everything is chatter free, end mill is new Widia 3 flute, steppers are working fine (no stalls or anything), my milling numbers are very conservative and material is Aluminum. Setup is beefy vice secured to the table at 4 points, nothing is loose.

https://www.cnczone.com/forums/attac...d=434930&stc=1

This creeping is pretty consistent - not something erratic or occasional - as if it were programmed - except that it wasn't. Hole was produced by Centroid conversational and simulation produces a hole, not this skewed thing. Produced G code looks ok.
Other operations I tried were fine - facing, plunging and cutting slot directly with g code, etc. I don't know what else to try.

Many thanks,
Bruno

can you attach the G Code or upload as a Zip file so we can view the program?

Try generating the same hole in a CAM program and see the result. That almost looks like a math error in the motion control calculations.

Is that a once around single pass hole? Also at what pole position are you starting at? N-S-E-W?

Ok, after consulting on several sides and doing some experimenting - it seems that this is a purely mechanical issue. I wouldn't expect Centroid to have these kind of issues with basic conversational features like a hole. Anyway, what I thought were a strong enough steppers proved to be wrong - it's a deceleration issue. In this photo each layer is 0.1mm deep and after about 2mm of depth, my X would slip about 6 millimetres. In the end, cutting down feed rate brought me spot on. Now I'm on the path of getting bigger power supply and stronger steppers.

Thanks all,
Bruno

Really helpful. Kudos to these answers and thanks for posting it here.








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