[bfsteel]

Problem: when milling a 4 inch square, the cut is short by .010 to .012 in in both x and y.

Items done: leveled machine
fixed loose bearings in x ball screw
had bad ball screw in y had it reworked
tried original parameters that we from Milltronics


DOes anyone have any suggestions or list of items to check in order to T/S this problem. We do not use cutter comp and it shows off on the control.

This problem occurred after turning it on after a weekend.


Thanks

Bob

[Farmers Machine]

It is very simple to use cutter comp in converstional programming. are you using precision collet tool holder or end mill holder with set screw?
put an indicator on the table and turn the shank of the end mill and check run out, any run out will make the end mill cut larger than it is. when was the last time you put spindle mate in the spindle and cleaned the taper of chips and coolant residue? Check run out on the tool holder and see if it wobbles. If the spindle and tool holders are perfect and end mill is exactly on size then you will have to call Milltronics to make a service call to re laser calibrate and set up new ball screw parameters. With the cut being off on both X and Y it looks a lot more like run out issues than problem with the big white iron.
Good Luck and look for simple, it usually is.
The Farmer

[moldcore]

Have you checked the backlash? There is backlash compensation in the parameters that needs to be set for each machine. If you’re using the original parameters that came with the machine and you’ve reworked the ball screw without resetting the backlash then you’re asking for trouble. However with that said, .010 to .012 undersize could be a combination of a number issues. I’ve never seen that much error attributed to the backlash alone.