On-Machine Part Certification Using Fringe Projection Techniques.
Shawn P. Moylan
Manufacturing Metrology Division, MEL
On-machine part inspection and certification is an important goal that, when realized, will offer significant improvements in the field of discrete part manufacturing. In addition to obvious benefits of certifying parts immediately after machining, with no time lost between machining and inspection, such a process will reduce the need for repeated fixturing and establishing of new datum surfaces, thus improving the correlations between measured part errors and machine errors, allowing errors to be quickly recognized and corrected. Micro/meso-scale manufacturing stands to benefit even more than large part manufacturing from development of this technology because on-machine measurement helps avoid many of the unique problems presented by the small sizes of the parts and features. The goal of this research project is to evaluate the feasibility of fringe projection as a technology to enable on-machine part certification.
While a wide variety of techniques are available to characterize machined parts, fringe projection is much better suited to on-machine measurement than others. Fringe projection, a variant of shadow moiré, is a versatile and robust process capable of relatively precise measurements over a range of sizes, allowing certification of large parts and micro-machined parts alike. It is a non-contact process, thus decoupling the measurement from the machine tool coordinate frame and isolating the measurement components from the harsh machining environment. This technique provides, at very high speed, a large amount of information, including 3-D data, in the form of a point cloud. Recent developments in LCD displays and digital projection devices allow projection of more revealing fringe patterns, and digital cameras with more and more megapixels allow more accurate measurement.
Although stand-alone fringe projection systems are commercially available, current limitations make their application to on-machine inspection problematic. This project strives not only to design, assemble, and test a fringe projection system that will mount on a machine tool, but also to study the fundamentals of the measurement process to provide strategies that address key challenges and limitations.
Author: Shawn Patrick Moylan
Mentor: M. Alkan Donmez
Division: Manufacturing Metrology Division
Laboratory: Manufacturing Engineering Laboratory
Building: Sound Building (233)
Mail Stop: 8220
Telephone: (301) 975-4352
Fax: (301) 975-8058
Sigma Xi membership: no