STL triangular patch top-point isometric offset based incrementally formed support body generation method

Abstract

The invention discloses an STL triangular patch top-point isometric offset based incrementally formed support body generation method which is a method for generating a curved surface of a support body model by adopting an STL model for the external surface of a part. A top point of each triangular patch in an STL file is isometrically offset by the thickness of an original plate in a negative direction of a Z axis, thereby providing basis for incrementally forming and processing and quickly and automatically generating a reasonable curved surface of a support body. The method has the beneficial effects that the reasonable curved surface model of the support body is obtained according to the thickness change of the part, thereby effectively ensuring the processing quality of the part; a reasonable gap between a tool head and the support body in different forming angle positions is ensured; it is only required that the generated STL file is read and all Z coordinates are isometrically offset, so that the operation is simple and convenient, and the use is convenient; and the design of the reasonable curved surface of the support body can improve the processing quality of the incrementally formed part and contribute to popularization and application of an incremental forming technology.

Description

technical field [0001] The invention relates to a method for automatically generating a support body model required for progressive forming of a sheet metal part, in particular to a method for generating a support body for progressive forming based on equidistant offset of vertices of STL triangular pieces. Background technique [0002] Sheet metal incremental forming is a moldless flexible forming technology proposed by Leszak of the United States in the 1960s. In the 1990s, Matsubara Shigeo of Japan conducted further research on this technology, which gradually attracted the attention of scholars from all over the world. Incremental forming technology is an advanced manufacturing technology based on computer technology, numerical control technology and plastic forming technology. It uses the idea of ​​"layered manufacturing" of rapid prototyping technology to discretize the three-dimensional model into a series of two-dimensional contour shapes. A flexible moldless forming...

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Problems solved by technology

[0004] Regarding the determination of the contour size of the surface of the support in incremental forming, Zhu Hu and other scholars proposed an algorithm for offsetting the STL model of the part by unequal distances. and offset distances are grouped according to their differences; then in each group, the weighted calculation method is used to calculate the offset vector and offset distance of the vertices, and the vertices are biased towards the offset direction of each group; finally, the triangle network is used to The grid fills the gaps generated by the multi-directional offset of vertices. Although this algorithm has some innovations, there is a lot of uncertainty in the grouping of triangle slices. In addition, a weighted algorithm is used in each group to obtain the vertex offset vector. The weighted value The size is not easy to determine; finally, because the vertices are offset in multiple directions, the topological relationship of the vertices of the triangular mesh will be changed when the gap generated by the offset is filled with the triangular mesh in the later stage, and there is a big difference in surface fitting. Deterministic, the author's own experiments have also proved that there is a large error between the actual value and the theoretical value of the support gap obtained according to this algorithm; at the same time, the algorithm is relatively complicated, and it is very difficult to operate in practical applications

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