The ballbar contains a precision linear transducer. It is used to measure variations in radius as the ballbar is rotated around a fixed point. This data is used to calculate overall measures of contouring performance (circularity, circular deviation) of CNC machine tools, in accordance with international standards such as ISO 230-4, ASME B5.54/57 and GB17421.4. System software also provides a detailed diagnosis of contributing individual error sources when analysed using commercial company’s unique diagnostic report format. Data is displayed graphically as well as in numeric format to support diagnosis.
The 2D GRID ENCODER dynamically tests the contouring accuracy of CNC-controlled machine tools. It can perform, for example, circular interpolation tests with radii ranging from 115 mm down to 1 μm at feed rates up to 80 m/min. The 2D grid encoder can also perform free-form tests in two axes. The advantages of the 2D GRID ENCODER include its contact-free measurement, which eliminates the influence of ball bearings such as with the DBB. Also, the error resulting from the machine's geometry has no influence on the results of circular interpolation tests with very small radii.
The 2D GRID ENCODER consists of a grid plate with a waffle-type graduation, which is embedded in a mounting base, and a scanning head. During measurement, the scanning head moves over the grid plate without making mechanical contact. For setup, the mounting base is fixed onto the work piece-holding element and aligned. The scanning head is mounted in the locked tool holding element and is also approximately aligned.