hi guys, on a router,we have a y axis which is losing about 2mm on 400mm dia circle when splines are machined, in this case little curved pockets for fan blades which are in a patterned aray around the perimeter of a circle. this problem only occurs when splines are machined and not arcs. we are running latest mach3 and am stumped and pulling my hair out over this one, can any body shed any light on this boggle? any help much appreciated...thanks marc.

Hi Marc - as no one else has taken a shot...

Mach (as far as I'm aware) has no concept of splines, only lines (g1) and arcs (g2 & 3). So I'm guessing that though the splines may well exist in your CAD, by the time they get to Mach they will have been converted by your CAM/Mach POST to arcs. - so... is the problem in your CAM?

Apologies if I'm way off.

hey thanks for the help, you arnt way off at all, in fact i have had a few chaps tell me the same thing you said, but in the end it looks more and more like a mechanical error, perhaps a loose grubscrew on the y axis steppercoupling. they are still checking it out to confirm
thanks for the help, all the best marc

Hi Marc

If it's not a mechanical error, Try reducing your F speed and reducing the Acceleration value for your Y axis, Under Motor Tuning.

Mach will cut the spline G-code, It just slows it down allot and may miss steps due at fast direction changes.

Is it vibrate the axis's allot ?

May be an inertia/mass issue, Is the Y axis carrying/moving your X Z axis's also ?

Just some Thought's, Chip