This paper outlines the use of VSA Audit procedures to identify sources of build variation in an assembly operation. VSA Audit isolates the effects of component variation from variation incurred during the the assembly process. (wear of fixtures, fixture breakage, etc.) This approach provides significant advantages when troubleshooting dimensional variation issues in an assembly plant environment.
VSA Audit uses measured component dimensions in a computer simulation of the assembly process. Initially the VSA model is correlated to the assembly operation such that output from the model matches output from the operation. As new shipments of components are received, measurements from each batch are used by the VSA model to predict the impact of the new batch of parts on dimensional variation in the final assembly. This activity identifies potential problems due to part quality prior to building the product. Identifying trends and correcting or replacing parts at this time can generate significant savings for the organization.
Trouble shooting dimensional variation issues can benefit from the use of VSA Audit. Causes of build variation are usually determined by trial and error, guided by experience. VSA Audit is a tool which highlights differences between the assembly operation and an ideal benchmark using objective information. Significant changes between the values of VSA Audit predictions and measured data indicate a change in the assembly process. The nature of this change may be investigated using the VSA model to simulate tool wear, breakage or other potential sources of variation in the process.
An example of both applications using a simple assembly will form the basis for a discussion of the VSA Audit approach, its strengths, weaknesses and potential.benefits for an organization.