Quote Originally Posted by Doddy View Post
Presumably you can swap the drive/positional feedback between the X/Y servos?, have you tried this?, what's the result? Then repeat with swapping the X/Y servo drivers. You should be able to isolate to either servo or driver in error... if not, then it's likely mechanical.
Doddy it's not that simple with Servo's Esp if running analog (And if Husky is who I think(Mat) then sure he is running analog) because each drive is tuned to the motor and it's load, so it's a lot of work not just a simple switch over like steppers.

Quote Originally Posted by Doddy View Post
You don't mention: Is your part a progressive multi-depth cut?, If you were losing steps then you would expect any error to accumulate and might expect to witness this as you cut through the material. I'm inferring from your post that this (accumulated error) is not the case, and the error is repeatable.
He's using AC brushless Servos so there are no steps involved. The encoders deal with position and feed it back to the drive so corrections can be made. You get what's called following error so if drives not tuned correctly to the motor and it's load then the error becomes larger, up to a point then drive will fault.
A correctly tuned setup will keep this following error to a minimum which doesn't affect part quality. But if anything changes like start putting much heavier than usual loads on table or binding or mechanical issues then the following error becomes greater and will show in the part. If the following error is on the edge of acceptable or binding etc is isolated just to one spot then because of how servos work the servo loop always allows the motor and position to catch back up so don't get a fault. The allowable following error can be adjusted in the drive so it could be set to a lower value which will help catch any trouble before the part is ruined, but it's a fine line between right and wrong.! I've also given a very simplified explanation of servo tuning , in practice, there's more to it.