Research On CMM/CAD Of Injection Molded Parts Of Automotive Lamp Housing

With the rapid upgrade of our country’s manufacturing industry,the quality requirements of products are becoming stricter.CMM has became an indispensable quality testing equipment for manufacturing enterprises.Therefore,how to give full play to the performance of the coordinate measuring machine to achieve the highest measurement accuracy and the fastest measurement speed when it work is the key topic of product quality measurement technology research.To solve this problem,this article will take the real car lamp housing as an example,which use the Hexagon bridge coordinate measuring machine to study CMM/CAD technique and design a set of methods to improving measurement accuracy and speed,and study rapid CAD modeling.The specific research work is as follows:1.The CMM measurement path optimization method of the lamp housing was designed.Introducing Polychromatic sets theory,the lamp housing was divided into 54 features with plane,circle,cylinder,and plane.The probe type,measurement direction,and safety plane were used as the individual colors of the lamp housing characteristics.The boolean matrix of the feature constraint model to be tested.Then,the minimum spanning tree kruskal algorithm was used to calculate the shortest path theory on the surface characteristics of the lamp shell.During the planning of the measurement path,the safety plane,the moving point and the retracting distance of the probe were designed to achieve the purpose of collision and avoidance of the measurement path.2.The out-of-tolerance result of the calibration of the start-up probe of the CMM was used as the test index of the orthogonal experiment,according to the ambient temperature,the length of the elongated rod,the diameter of the measuring ball,and the measurement speed,a 4-factor 4-level orthogonal experiment was designed,The evaluation method of the extreme difference was used to analysis optimizes the control error factors and calculate the order of the factors that affect the error: ambient temperature>diameter of measuring ball>length of lengthened rod>touch speed.Therefore,it is necessary to control the ambient temperature of the laboratory in the following test to ensure a constant temperature of 20℃.3.The multi-color set theory was used to dividing the color results of the lamp housings and studing the manual sampling of the lamp housings.The content includes:clamping of the lamp housings,3-2-1 method to build the coordinate system,lamp housings Sampling of feature data.The first sampled data was used to carry out the first CAD reverse modeling of the lamp housing.4.The first CAD reverse modeling digital model was used to implementing the second sampling of the lamp housing,establishing the best fitting coordinate system and optimizing the sampling strategy.The second CMM sampling data was used to studied the methods of improve the modeling accuracy,and optimized the reverse modeling of the lamp housing.The coordinate measuring machine was used to verify and evaluate the CAD-optimized modeling results by shortest path planned.The average error is within±0.05mm,which proving the reliability of the method in this paper.In this paper,based on the current status of CMM research at home and abroad,combined with actual measurement experiments,the CMM error factors and planning measurement paths are studied.The final CAD modeling error is within 0.05 mm,which proves the reliability of the method in this paper.