Research On The Key Technology For Complex Die-face Compensation Of C-class Automobile Panels Based On Reverse Engineering

At present, Some large and precision complex mold of the domestic C class car mainly rely on imports which greatly improving the production costs. Studies have shown that sheet thinning and elastic deformation of die in stamping process can lead to product quality instability. The fitting rate of the die convex and concave die cannot be reached more than 90%, and the contact clearance error of each part is not easy to control in about 0.03 mm. Those factors can cause the low mold closing rate. Current solutions to this problem are:(1) Fitter painted parts with blue oil or Hongdan powder on both sides evenly by coloring method. Mold closing rate is confirmed through contact spots which left by parts after mold closing. The concave die is repaired on the punch as a benchmark if not qualified. This method needs to be carried out several times according to the experience. It is time-consuming and laborious which seriously affects the production cycle of the mold.(2) The elastic deformation of die is simulated in stamping forming using CAE(Computer Aided Analysis) technology, and then repair the mold according to the analysis results. But because the analysis result is not accurate enough, and can only play the role of qualitative guidance. In view of the above problems, this paper puts forward the compensation method of automobile panel die surface based on reverse engineering which provides theoretical guidance for the rapid implementation of die surface compensation. The specific research contents are as follows:(1) Research on the method of automobile panel die compensated surface reconstruction based on reverse engineering. On the basis of detailed various types of typical surface reconstruction theory analysis about automobile panels, combination of Bezier and NURBS surface reconstruction method is used. According to the surface types, mold surface is fitted to the high precision and smooth panel mold surface.(2) The method of acquisition compensation deviation and the compensation amount of die surface based on data model comparison is researched. Combined with a variety of digital mode alignment method to complete the registration, the 3D surface comparison and 2D profile comparison are used. By intercepting the 2D profile, the offset point coordinates of each compensation were collected, and the compensation amount of each deviation was determined.(3) The law of die surface compensation for automobile panel die based on curve fitting method is determined. The compensation amount after fitter spotting is analyzed. The compensation of die surface is obtained by using the curve fitting method, and the mathematical equations are established. Through classifying various types of automobile panel die surface, basic framework of the resource library is established.(4) A method for the determination of new die surface compensation based on the similarity theory is determined. Research on the similar mapping relationship between of the new and old product mold. According to the law of the obtained product die surface compensation and the corresponding location of the point set acquisition, the amount of die surface compensation for new products is calculated based on the equation. Experimental results show that the theory of compensation and fitter research results are basically consistent which prove the feasibility of the proposed method.