This part of the ISO13041 describes a method of checking the contouring performance of turning centres (or numerically controlled turning) by conducting circular tests and by evaluating the radial deviation F and circular deviation G, in accordance with ISO230-4.
NOTE Measurements of circular movements can be carried out by different methods as described in Clause6.6 of ISO230-1:1996. These methods consist of using a rotating one-dimensional probe and a test mandrel, a circular masterpiece and a two-dimensional probe, or a telescoping ball bar. Other test methods may be applied if the accuracy of the equipment is the same as (or better than) the accuracy of the methods described. Influences of typical machine deviations on circular paths are shown in AnnexB of ISO230-4:1996.
The concept of checks by circular tests described in this part of ISO13041 is to verify the circular movement
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only in one position per coordinate plane of the machine,
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at only one feed rate, and
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to repeat the test once in the opposite contouring direction.
The purpose of this part of ISO13041 is not to provide a means of analysing the causes for the measured circular deviations, but to offer the user a method for periodic checking of the machine tool. It is recommended to carry out the tests of this part of ISO13041 after the machine tool has passed the acceptance tests and to use these results as a basis for comparison during periodic checks. Therefore acceptable deviations from the initial results have to be decided by the user.
If the tests are used for machine acceptance purposes, the supplier/manufacturer and the user have to agree on specific diameters, feed rates and tolerances for the tests.
NOTE ISO13041-5, which deals with the accuracy of feeds, speeds and interpolations, also includes as test K4a circular test. There the aim is to check the mutual behaviour of two linear axes (generally X and Y) at two defined feed rates for one defined diameter. This is more or less a diagnostic test with respect to the circular interpolation, whereas the circular tests of this part of ISO13041 give information on the overall contouring performance of the machine.