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Rotary Axis Compensation

IBS Precision Engineering’s Rotary Analyzer has a unique feature for compensation of your machine tool rotary axis. Measurement values can not only be used to judge machine quality, but can also be used to improve the actual machine tool. A video comparison of the conventional system and our system can be found at the bottom of this page.

With the Rotary Analyzer, you are able to measure and compensate:

  • Rotary axis location errors
  • Rotary axis squareness errors

 

Demonstration: C-axis compensation

Presented below are the results of a demonstration that IBS Precision Engineering performed at a UK machine tool company in the offshore industry. This demonstration was performed on a Mazak Variaxis 730-5X machine and shows a “before” and “after” picture of the machine accuracy.

After quick and easy set up the measuring system in the machine, the demonstration started with an initial measurement to determine the stand-still performance of the machine. This measurement was used to indicate any problems with the machine’s servo’s and/or vibrations due to the machine’s environment.


The next step was to perform a C-axis rotary table position measurement. The measured result can be seen in the graph below.

 

 

The measurement data show that the machine is offset in all three directions (X,Y & Z). The small offset in the Z-direction (green graph) is caused by a misalignment of the C-axis. As the C-axis rotates around Z, no variation in Z-direction should be measured for a perfectly aligned machine. This misalignment is the squareness error of the C-axis. The variation measured in X- and Y-direction is caused by an error in the rotation center point of the machine.

 

The image above shows the analysis of the static C-axis measurement data. The parameters of interest (XOC, YOC, AOC, BOC) are given on the left side in this graph. These give the offset in X, Y and the squareness error respectively.

This measurement highlighted an offset error of the machine’s C-axis of:

  • XOC = +139.1 µm (offset in X-direction)
  • YOC = +13.7 µm (offset in Y-direction)

and a squareness error of the machine’s C-axis of:

  • AOC’ = +2.0 µm
  • BOC’ = +3.6 µm

 

Compensation

The largest error in the above machine is the location of the C-axis. This can easily be compensated by changing the rotation center point of the C-axis. The squareness error is small for both planes, so the C-axis is well aligned in this regard and no further adjustment or compensation is made for this.

For demonstration, the center point of the C-axis was compensated with -0,1 mm in the X-direction and the measurement repeated, resulting in the following measurement data:

 

This measurement indicated a reduced offset error of the machine’s C-axis:

  • XOC = +42.2 µm (offset in X-direction)
  • YOC = +13.6 µm (offset in Y-direction)

 

To complete the compensation, the center point of the machine was shifted -42.2 µm in X-direction and -13.6 µm in Y-direction, followed by a final measurement:

 

This measurement indicated a residual offset error of the machine’s C-axis:

  • XOC = -1.7 µm (offset in X-direction)
  • YOC = -0.3 µm (offset in Y-direction)

 

The demonstration showed that compensation of the rotary table C-axis, reduced the error from 139 µm to 2 µm. A significant accuracy improvement which will result in better quality products and cost savings!

The Rotary Analyzer in Action

The video below shows the system completing a B-Axis machine tool measurement. For standard qualification methods this process would require:

  • Multiple single probing points
  • Each axis to be measured separately
  • Measurement in 600 seconds
  • Static only
 
 However with the Rotary Analyzer the qualification process becomes:
 
  • Simultaneous in X, Y & Z
  • Measurement completed in 75 seconds
  • Static or dynamic measurement choice available

 

 
Back to Rotary Analyzer