Three coordinate measuring machines (3 CMMs) are used throughout industry to determine if complex parts are within the required tolerances. In general the machines operate on an automatic or semi-automatic basis in accordance with a predetermined routine. The results are then analysed by a computer using algorithms derived for specific geometrical shapes such as the straight line, plane, circle, ellipse, cylinder, cone and sphere. Since the user has no access to the evaluation programme or the algorithms employed he is forced to rely upon that the algorithms are able to cope with the problems met in practice and provide an accurate analysis. It is therefore to both the user's and the manufacturers'advantage to have available an independent means of verifying data evaluation programmes.
In the first phase of the project completed in 1987, data sets containing a range of deviations from ideal geometries, were produced for a range of geometrical forms. When these data sets were tested using programmes from 15 laboratories in Europe it was found that some analysis programmes were unable to interpret the information accurately.
The second phase of the project was established in association with 3 CMM manufacturers. It terminated 1990. Data sets have been produced for the same basic geometries but having higher demands on the evaluation programmes. It was shown that only about 50 % of the algorithms tested obtained acceptable results.
The data sets will be made available to industry. In order to maintain confidence in the result, it is necessary to keep the basis of the data sets secret. Potential users must therefore apply to PTB in Germany, via their own national metrology laboratories.
Funding SchemeCSC - Cost-sharing contracts
TW11 0LW Teddington