[fadalmatt]

When cutting any time there is a transition on the y-axis I get a step in my part. For instance when cutting a cylinder my part is dead on across (+- 0.0005in) but front to back it measures out a few thousandths off. A significant amount.

When I put a dial indicator in the spindle, touch a fixture and try to push-pull the table I can get it to move 0.0005 but nothing more. This is when approaching from both positive and negative.

When I do a backlash test, running the table out .05 and back .05 I'm getting back to within 0.0005

The only oddity I can find in testing is when I jog one direction and then reverse jog the other, the dial will move 4 clicks without moving and on the 5th it will start jogging again.

Does anyone know off hand what this would be? Any other tests that I should do?

[motionman]

The only oddity I can find in testing is when I jog one direction and then reverse jog the other, the dial will move 4 clicks without moving and on the 5th it will start jogging again.

Does anyone know off hand what this would be? Any other tests that I should do?

I am having a little bit of trouble understanding your post, but lets go through it one step at a time.

You have a step in part the appears in Y while interpolating a circle.

You have .0005 in lateral movement in Y + and -

In a repetability test while moving .050 you are holding within .0005

When using the pulse handle set at .0001 you get four "clicks" before movement of the table

OK that said, is your step/witness mark at a quadrant? 0d 90b 180d 270d ????? If so start with servo tuning, X and Y ball screws have to turn almost exact to cut a round part.

.0005 is ok insofar as table movement (I like a tighter machine, but if you are using cheap indicators this is normal)

Backlash compensation seems to be set ok

I would start with servo tuning, and retest repeteability by moving the table a few inches and not a few thousandths.

email me if you like for more advice [email protected]

[Larken]

If you can see the ball screw shaft, see if it is moving when you jog the small increment. If it is moving,It could be backlash in the thrust bearing or the ball nut . If it isn't moving, its servo tuning.

[RevetsP]

+1 on verify if the servo is turning when commanded. How does backlash look at the ends and middle? Being a fadal, I am still skeptical on bad thrust bearing or possibly screw.

Ways look ok? cover binding/bent? plenty of oil flow?