157 geometrical specification 23 geometrical

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Unformatted text preview: e of variations and the standard deviations are comparatively presented for all the tested machines in Figure 4 and 5, except A, D and J in Figure 4.a since the machine configurations did not allow the particular setup. 3.4. Discussion Considering bend angles, the factor with the highest sensitivity coefficient, being the springback angle, was determined for the material used in the experiments, and a noticeable uncertainty represented by a standard deviation of 0.09o was found. A procedure as described in 3.1.c, in which accurate springback values are obtained for every processed material, is recommended to minimise the systematic errors in bend angle predictions. The use of an updatable database or in process control of the angle can also be applied. While a database cannot help compensating for random errors occurring due to material anisotropy and thickness variations throughout the sheet, adaptive bending techniques in principle can be applied to minimise the range of variations. For most machines, the repeatability of punch vertical positioning was rather good, characterising by standard deviations ranging barely from 0.002mm to 0.008mm. However, the sheet thickness showed a standard deviation of 0.015mm, which caused a higher order impact to the accuracy of the resulting angle. Thereby, though having a Factors Influencing Dimensional Accuracy of Bent Parts 349 rather low sensitivity coefficient, the contribution of the uncertainty of the sheet thickness represented approximately half of the total uncertainty of the resulting bend angle. For machines J and K, equipped with adaptive control of bend a...
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This note was uploaded on 08/03/2010 for the course DD 1234 taught by Professor Zczxc during the Spring '10 term at Magnolia Bible.

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