Grid Encoder for Testing CNC Machines

Heidenhain’s KGM 281 grid encoder is now available with a diameter of 140 mm and an increased accuracy of ± 1 μm.

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Heidenhain Corp. has improved its family of KGM grid encoders to better serve CNC-controlled machine users who require accuracy testing. The KGM 281 grid encoder is now available with a diameter of 140 mm and an increased accuracy of ± 1 μm.

The 281 model has a grid plate with phase grating that has an optical measuring standard. It is embedded in a two-piece aluminum holder. The design of this holder prevents the mechanical stress that can happen at the level of the measuring standard even if the mounting surface is not plane. This makes it possible to guarantee the accuracy grade of ±1 μm for the system.

Users can mate the KGM 281 to the same dimensions as the previous KGM 181, but because of the revised mechanical design, it is 21.5 mm higher than the previous version.

These KGM grid encoders dynamically test the contouring accuracy of CNC-controlled machine tools. They can perform circular interpolation tests with radii ranging from 115 mm down to 0.1 mm at feed rates up to 80 m/min., for example, and that they can also perform free-form tests in two axes. Heidenhain says that one advantage of the KGM is its contact-free measurement, which eliminates the influence of ball bearings. Heidenhain also says that the error resulting from the machine's geometry has no influence on the results of circular interpolation tests with very small radii.