Development of a three dimensional copier system using shadow Moire and rapid prototyping technology

Abstract

The replication of an object, from a prototype in the design office to the actual manufactured product, may appropriately be perceived as reverse engineering. This process primarily includes two steps: first, three-dimensional measurement of object shapes; and second, model reproduction based on the measured three-dimensional data. Currently, three-dimensional shape measurement relies mainly on the use of traditional coordinate measurement machines (CMM), which require point-by-point measurement of surface coordinates. A more advanced laser measurement device employing a line-scanner is also commercially available. Measurement using both techniques, however, is a slow process. A rapid, yet precise, three-dimensional shape measurement tool for the reverse engineering process is therefore important in meeting the requirement for fast-track production in the industries. In this research, a full- field three-dimensional measurement technique based on the shadow Moiré phenomenon is developed. Combining this technique with a rapid prototyping (RP) machine, an efficient system is developed for reverse engineering applications. In essence, this system functions as a three-dimensional copier Obviously, the three-dimensional profile that is rapidly acquired can be transmitted to any distant location through telephone lines or internet. Therefore, the system may also be used as a three-dimensional fax machine. Apart from theoretical background, this research is also involved in the design and fabrication of the shadow Moiré instrument as well as the supporting software using LabVIEW. The system is user friendly and demonstrated to be particularly useful in copying three-dimensional objects. In all measurement set-ups, system calibration is compulsory before quantitative measurements can be achieved. In this research, a simple yet novel calibration procedure, in which the test object whose profile is to be measured also serves as the calibrator, is described.