An assembly is where the sub-assemblies and parts which comprise a product come together. The intellectual arrangement of parts in an assembly is a difficult task. Modern CAD environments ontain tools which allow CAD part models to be brought together and problems such as clashes to be discovered. If these problems are not solved before manufacture the physical parts will not assemble ogether without expensive rework.A well-captured design intent for assembly models will enable the designer to design out manufacturing and assembly difficulties at an early design stage.
Aim and Objectives
The aim is to introduce an automated CAD based process defining and capturing design intent in assemblies, and to eliminate clashes which present in a CAD model assembly.
Step 1: Calcukate initial clash in the CAD model assembly (if any).
Step 2: Perturb the parameters in the assmebly model by a small amount (ΔP) and recalculate the clash in the assembly.
Step 3: Calculate the sensitivity of each parameter as the change in clash with respect to the change in parametric value (ΔP).
Step 4: Generate a list of parameters with a sensitivity value along with the features which the parameter represent.
Step 5: Establish any relationships which may exist in the assembly by using the algorithm developed.
Step 6: Constrain the assembly using the identified relationships.
Fig. 1: Process work flow
The fig. 1 shows the method in which 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 are used to calculate the optimum combination of changes in each parameter to eliminate the clashes.
Relationship identified: Shaft diameter = Hole diameter in the housing component
Fig. 2: Bracket Assembly
|Clash Volume (mm3)|
|Initial Clash 1||6200|
|Initial Clash 2||852.16|
Table 1: Clash elimination
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