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Laser Calibration / Ball Bar Analysis
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Questions and Answers

What is laser calibration?

    Laser calibration is a means of compensating for wear or inaccuracies in your machine tools.  The laser is used to measure the positioning error in the machines axes.  If the CNC control has a feature commonly called Lead Screw Error Compensation, then this data can be used to compensate for the measured error.

Why do I need laser calibration?

    If your machine must be used to perform accurate work, then you should consider laser calibration.  The laser not only shows you how accurate your machine is, but can be used to compensate for inaccuracies.

When do I need laser calibration?

    Laser calibration should be performed after any major mechanical work is done to a machine's axis.  This includes new ballscrews, gearing or feedback changes.

Can I use laser calibration?

    The laser can be used to measure any machine.  Laser compensation can only be used if you have a CNC control with this feature.

 Using standards of which the calibration is traceable to the National Institute of Standards and Technology, Optodyne calibrated our LDDM Laser System. The Laser System was calibrated by comparison with a Precision LDDM System which was calibrated by NIST to be accurate to within 0.5 ppm with automatic atmospheric pressure and air temperature compensation. The two systems were aligned along a common axis with retroreflectors placed back to back on a travel carriage. The ambiant conditions were at 68 +/- 2 degrees F and 40% humidity.

The calibration system is in compliance with MIL-STD-45662A. The calibration system uncertainty was estimated to be +/- 0.5 ppm.

Based on the measured data, the accuracy of the laser system is less than 0.000017 inch over 20 inches or +/- 0.66 ppm.
NIST Test Number 821-257670-97

What is ball bar analysis?

Ball bar analysis is one of the best tools to determine your machine tool's mechanical and servos performance and allows comparisons with your other machines in the building.

How does it work?

Eagle Machine sets up the Renishaw Ball Bar on your machine, writes a parts program, and takes a circular data sample of the machine's motion of the X and Y axis, the X and Z axis, and the Y and Z axis.  The computer software generates a graph of each of these motions that shows the machine's circular accuracy on each of these planes.  From this graph we can determine the severity of problems that exist with mechanical alignment, mismatch of the servos on each axis, backlash and/or chucking.

What does this mean to you?

At completion of a recent control upgrade on a machine, the ball bar test showed the X axis ball screw had play in it.  Instead of sending three screws in for repair, we had the problem screw fixed.  As a result, the circularity of the X and Y axis improved from .028 to .0008. 

What does it cost?

The cost to complete the initial ball bar check on your machine is typically $125.00 to $250.00 per machine plus travel and mileage.  Machine adjustments are additional.

 

Eagle Machine Tool Corporation
6060 Grand Haven Road
Norton Shores, Michigan 49441
231-798-8473  or toll free 1-877-771-0775