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Problems with guide curves in models when exporting to comsol for a boolean union operation

Question asked by Rami Saba on Nov 10, 2010
Latest reply on Dec 1, 2010 by Jerry Steiger

Dear all, i am having a serious problem exporting my model to Comsol 4.0. The model is all constructed in a part file (not an assembly, i have tested to see whether an assembly would fix the problem or not and it did not). The model is made up of several solids. Each solid is created using the loft function which uses several cross-sections and several guide curves at all edges of the cross-sections. The solids are sketch-wise all properly connected with no gaps in between. The problem is that when exporting the model to comsol, i cannot using a Union boolean operation to join all the solids into one object (but still having separate domains. Comsol tells me the geometry is not accurate.


Therefore, i have built up a simple test model that uses the Loft function and guide curves in the same way as my main model, and have found that the problem is to do with the guide curves, or rather, the order in which i select them. i cant seem to find any specific order that solidworks would like me to build my model in. Also, finding a solution for one solids curve selection order does not help to solve other solids problem with the guide curves.


Note, if you use a loft function through cross-sections guided by guide curves that move in a flat circular direction as opposed to an elevating spiral direction, the model exports just fine. If you slowly start to lift one end of the model, after a certain height increase the boolean operation in comsol fails. To fix it, it seems you need to change the order of the curves randomly!. So the problem really occurs as soon as the curve starts to increase in height into a 3d space. Finind one order that works for solid does not work for others, or others are not having a problem even if they are built in exactly the same way.. what is going on!?



The general model is basically of the inner ear constructed by use of a loft through several cross-section in a spiral manner following guide curves that spiral around an axis together.


The attached simple version is attached as elecated at 120. If you go into sketch 1 of loft 1, you can change the height (currently set at 120) to 5 to make it flat or any other lower height if you wish to see how it works fine at lower heights. The attached version will fail because its set to a high height at 120, To see what i mean by changing the order of the curves to get it to work, the current order selected is 8,5,6,7 so edit the feature and change the order by swapping the 8 and the 5 to get 5,8,6,7 and if you have comsol 4.0 (or 3.5) it will work in comsol when performing the boolean union operation.


Attached is a couple of pictures of the actual model i am working on showing how the guide curves in light blue are defining the path for the solid with the face coloured in red as an example, the same is done for all other solids. Also attached is the file of the simpler version that depicts the general concept of my model.


Thank you for your help!, and if anyone out there thinks they can help me but need more information please let me konw. My email address is