Mandrel Meshing for fibre path generation
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In order to avoid potential problems during fibre path generation, it is advisable that the user attempt to maintain the aspect ratio of all elements to be as near to a ratio of 1:1 as possible. In practice this is difficult, and a wide variation in the aspect ratio of elements is to be expected. However, we do recommend that elements do not exceed a ratio of 10:1, in any direction, and that a minimum of 16 elements per revolution be used. Larger aspect ratios may lead to inaccuracies in path generation though this is not necessarily the case. A warning is given for elements that exceed the advised 10:1 ratio, the elements concerned are listed to the errors logging file CADFIL.LOG.
The main reason for such an error to occur, is where cylinders have been defined using a few points, giving rise to large X co-ordinate steps. This can be rectified by inserting additional points where necessary in the mandrel data file in the mandrel section of the software. A warning is also given for meshing the mandrel with fewer than 16 elements per revolution. This is for user information purposes, and does not stop the user from continuing with the fibre path development section of the program. This minimum is recommended to enable the system to gain an adequate surface representation of the mandrel. A trade off is required between the accuracy of the mandrel definition, and the computational time required. A high number of elements per revolution will increase the time for path calculation, not only in this section of the program, but since the file generated is required in later parts of the system, then it will also affect the speed of path generation in these sections also. This very high definition of fibre paths is, unnecessary to generate accurate NC programs. A 'number of elements' value of 30 is suitable for most purposes, the current default is 60 reflecting the increased speed of modern PCs.