Sensitivity approach for automatically eliminating clash from CAD model assemblies

Clashes occur when some components in a CAD model assembly violate others. If clashes are not eliminated before manufacture, the physical parts will not assembletogetherwithout rework, which is expensive. In modernCAD systems, features in a component modelare controlled by parameters. A complex component model may be defined by thousands of parameters; therefore it can be extremely difficult and time consuming to identify the parameters which need to be modifiedin ordertochange the shape of the model to eliminate the clashes. In current industrial practiceclash checks are carried out, but these are time-consuming and prone to error. The result is that too many design errors are discovered late in the product-development process when they are costly to fix. This paper introducesan automated approach for eliminating clashes in a CAD assembly, by identifying which CAD parameters need to change, and by how much, to eliminate theclashes. Sensitivities are calculated for each parameter in the assembly as the change in clash volume due to a change in each component parameter value. These sensitivities areused to calculate the optimum combination of changes in each parameter to eliminate the clash. The approach has been tested for a number of example models, and was able to successfully eliminate the clashes. Consideration is given to the fact that it is preferable to modify some components in an assembly than others, and that some components cannot be modifiedas thedesigner does not have control over their shape.