When parts drift out of tolerance or circles aren’t round, a repair tech will usually suggest a ballbar test or laser calibration. Here’s what they are.
Ballbar test
A ballbar is a precise telescoping bar with a ball at each end. One end mounts to the table and one to the spindle, and the machine runs a circle. The bar measures tiny changes in radius as it goes around.
In a few minutes, it shows problems like backlash, squareness between axes, servo mismatch and stick-slip. It’s quick, affordable, and great for tracking a machine’s health over time.
Laser calibration
A laser interferometer measures how far an axis actually moves compared to what the control commands, along the full length of travel. The results can be used to set pitch error compensation in the control.
It takes longer than a ballbar test but gives a complete picture of linear accuracy.
When to do them
- A ballbar check once or twice a year on critical machines
- After a crash
- After moving or re-leveling a machine
- When parts start drifting and you can’t find a cause
- Before buying a used machine
Find techs who offer this on our alignment and calibration page.