Research Of Reverse Engineering About Free-form Surface Based On Three Coordinate Measuring Machine

Reverse Engineering (RE) refers to an object’s CAD model re-construction process according to the data analysis obtained from the fabricated product. Compared with conventional design mode,reverse engineering is applied to the following environmentonly product or object model is available,while the drawing of prudct is unavailable.Nowadays,RE has been in widely used and aroused more and more attention in many years such as machinery,aviation,aerospace and medical treatment. There are lots of parts which have free-surfaces in RE, so it is very significant to research the key questions in free-form surfaces.This article investigate the process of free-form surface measuring and re-construction of three-dementional model by obtaining data from the three coordinate measuring machine(CMM) in our lab.Analysis the error of CMM,work out the routine of free-form surface measuring which is optimized,the technich of cloud point dispose and free-form surface re-construction.The main work in the article is arranged as follows:The author checks the individual error of the CMM system including the transmission error of X axis,Y axis and Z axis.1、Error check and compensation of the CMM:The author checks the individual error of the CMM system and se up mathematics module to compensate the CMM system error.Use software compensation method to compensate the CMM system error.2、Free-form surface measuring path design:Basing the PCI-1243U motion control card,the author designed the VB programme of measuring path by way of coordinate three axises’ motion in order to scan the free-form surface. The data obtained will be disposed in the programme module as well as the measuring path is optimizing by three methods which is method of adapting scanning interval,method of adapting scanning frequency,method of adjust of overheight automatically. 3、The cloud point analyzing:By using the module of wiping off useless point,the cloud point will be disposed.Resolved the the phenomenon of bed of cloud point during the scanning process and ascertain the least scanning interval.The author also ascertain the relationship of the position of part and the scanning chief direction by analyzing the break of the boundary cloud point.4、Free-form surface re-construction:Put the cloud point into the format of IMW which will be dispoed by the software called imageware.Re-construct the surface and analysize the error between the cloud point and surface.Finally, main results and conclusions of this dissertation have been summarized; the prospects and study emphases of the future research work have been discussed and forecast.