Collaborative Research: Quantitative Roundness Design and Quality Assurance for Ultra-Precision Assemblies with Significant Error-Scaling Problems

Purdue University, West Lafayette IN

Investigators

Abstract

The objective of the project is to reveal new and fundamental insights into the error-scaling problem for ultra-precision applications in design and manufacturing and answer long-standing questions about quantitative design of geometric tolerances in roundness. This error-scaling problem arises when the uncertainty of precision becomes unacceptably large as the size of the critical features approaches in magnitude the size of the repeatability achieved during manufacturing. A collaboration is formed to develop a quantitative technology for designing and achieving quality assurance for manufacturing precision round components and assemblies, such as fuel injectors and spindles. Although engineers are now better trained in assigning proper size tolerance, at present there does not exist a quantitative methodology for assigning geometric tolerances such as roundness. Furthermore, the error-scaling problem that is critical to the manufacture of small scale (meso, micro, and nano) devices. As a result, fundamental definitions of quality assurance indices will be revisited via a new probability analysis considering truncated and skewed distributions in the region of significant error-scaling problems. These improved indices can then be incorporated into successful quality assurance approaches such as TQM and Six-Sigma. Roundness issues have great economic and social impacts. The development of low-emission diesel engines requires clean diesel fuel, electronically controlled fuel injection, and high injection pressure. Achieving a high injection pressure (over 30 ksi) requires a very precise control of fit conditions between the nozzle and the injector plunger, which in turn depends critically on the roundness of the plunger and nozzle bore. The proposed roundness technology is also critical for miniaturization techniques in imaging, in telecommunication, in lithography, and in many other fields.