VMC - Setting Pitch Error Compensation in ball/lead screw

[Newbeeee™]

Hi all,
We had both the X and Y ball screws re-built a week ago. They were only re-balled with no grinding.
Our tech re-fitted with new thrust bearings as well.
All sounds nice with no slop/backlash, but the renishaw ballbar was showing out of round and scaling error between the axis.

We put a 2micron dti in the spindle and got the gauge/slip blocks out, and yes there is pitch error, winding onto the slip and keep winding in the same way.
We looked at the machine (fanuc) parameters and the pitch comp table looks to be set to have values at every 30mm.

Anyone have experience in calibrating a screw, and how did you do it?
Our thoughts are to buy a few 25mm and 5 mm slips, and to stack them, so we can set the 0 point in the machine at its home position, and then move every 30mm and enter the error accordingly into the control.
Does this look sensible or should we be programming and moving under feed control?
If we always wind the axis the same way to eliminate backlash, winding by handwheel shouldn't be a problem yes/no?

Thanks

[Machineguy]

Newbeee,

 

Because you used  reground ball screws. I would do the following:

Laser comp the ballscrews both directions. That will give you the error to put into the tables.

Second, you need to check the drives to make sure they are working together at the 45 deg movements at slow,  med, and fast feedrates. They may need to be adjusted

so they sync together.

Do it in the above order and you machine will run really nice.

 

You will need to call a outside service to do this.

 

Machineguy

[Newbeeee™]

Thanks for the reply.

Just to be clear, re-balled only, not re-ground.

I never thought of both directions for checking though!

Ref the drives, are you talking parameter 2048 (fanuc oi control) to tweak - I have done that already to get the best roundness using the ballbar.

[chris m]

You really need a laser, IMO, to get the pitch error comp correct. Your machine tool distributor will, perhaps, have a service tech that is trained in this; if not, most industrial areas have 3rd party companies that specialize in laser calibration.

 

C

[Guest]

We use these guys ( http://www.lasers-inc.com/ )

[?Mark]

We use these guys ( http://www.lasers-inc.com/ )

Awesome....we having them realign our okuma

[?Mark]

Comment on lasers-inc...

Mark came in and setup our okuma m800vh. For the first time ever we were able to do a 5 axis job with no offset adjustments.

He's done a superb job and I highly recommend them.

Something hartwig should learn to do...;-)

[Art@API]

Glad you got your machine calibrated, I've heard good things about Laser Inc., for future reference you can also contact API Services. We can calibrate machines, rent lasers and provide training. Please visit our website at http://www.apitechnical.com/

 

Cheers.