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Unformatted text preview: ility the holes pattern falls inside the location tolerance, centred around each hole nominal position, is estimated as the product of the probabilities due to each hole. The probability each hole falls inside the location tolerance is estimated by means of an analytical expression. The optimal positioning of the locators is designed by minimising the deviation in holes pattern positioning during drilling due to locators inaccuracy. The proposed method may be applied to a holes pattern with any material conditions by considering an appropriate location tolerance zone. 2D parts have been considered as application examples. The present work considers error free starting workpiece and machine tool. In the following the optimal locators positioning method is deeply described (§2), some application examples are discussed and a very simple suboptimal configuration rule is introduced (§3). Position Deviation of a Holes Pattern
2. OPTIMAL LOCATORS CONFIGURATION 203 The case study is represented by a plate with a holes pattern to be drilled, as shown in Figure 1. A RFS location tolerance specify the position of holes pattern. The position of the workpiece is determined by two locators on the primary datum and one on the secondary datum. Each locator has coordinates related to the part nominal reference frame, represented by t...
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