Abstract: In die CAD system, using circular polygon method, non-circular shape of the punch and die processing, a top view automatically generated according to the method of the main view.
Keywords: Die; CAD; arc; polygon
I. Introduction
In the design of stamping dies, if the mold punch and die edge shape is round or rectangular and other simple shapes, punch and die are relatively easy to design and calculate the cutting edge dimension is also very simple. However, not all the punch and die stamping die edge shape is regular, there are many pressing mold punch and die edge shape is irregular, which is composed of multi-segment line, or by multi line and multi-paragraph composition of arc, or arc composed entirely of multi-segment, such punch and die edge calculation and design are very troublesome.
As the non-circular punch and die of non-circular shape of complex, in order to facilitate the process, both in the design of non-circular punch and die of non-circular cavity into a straight cylindrical design, which for the use of computer automated design provides convenience. If you use the computer to achieve such a punch and die were automatically generated, and the combination of CAM, not only would the designers of the labor intensity, and can greatly improve the mold design and processing efficiency and quality.
Second, non-circular punch automatically generated
Various non-circular punch can be divided into two situations: first, non-circular punch completely overlooking the map contour line segments; second, non-circular punch of the top view contour line and the arc from the arc or entirely composition. For the second case, the main view in the generation before the punch to be on the top view of the arc for proper disposal, which is under the arc of the situation, consider arc in the main view of the projection, or a few paragraphs with a line segment replace the top view of the arc, this method is called "arc polygon."
Analysis of various types of arc, according to the projection principle, alternative arc can be divided into three situations: (1) if arc segment AB, as long as the level of arc and circle diameter no intersection line segment AB can be replaced with a round arc AB, as shown in Figure 1a. (2) if arc segment AB, as long as the arc and the diameter of the circle there are two levels of the intersection of C and D, three line segments can be AC, CD, DB alternative arc AB, as shown in Figure 1b. (3) if arc segment AB, as long as the level of arc and the diameter of the circle there is a point of intersection C, the two segments can be AC, CB to replace the arc AB, as shown in Figure 1c.
Figure 1 arc multilateral
2. Polygon point set of processing
If the two arcs or arc and line connection points as the cutoff point, in the main view may not correspond with the cut point of the ridge, in order to correctly generate the main view, overlooking the graph in the "polygon" of treatment, must be cut point for all to judge, to determine which cutoff point cut to remove and which should be retained. Specific judge as follows: (1) If the two arc tangent, located center of the circle were O1, O2, radii R1, R2, cut point of P, O1x, O2x, Px were two points of the X center of a circle and cut coordinate values, when | O1x-O2x | = | R1-R2 | when the cutoff point needs to be maintained all point to delete. (2) If the vertical line and arc tangent, the tangent point to keep the rest of the line and arc tangent, the tangent point to delete. Contains a non-circular arc segment top view during the punch, "polygon" of treatment, then transformed into a non-circular punch line segments composed entirely of top view of the situation, which after processing the first case and second case, the method is the same of.
Figure 2 is a diagram of a stamping parts, to automatically generate this part of the blanking punch, the first part of the requirements and according to the thickness of sheet metal parts diagram on the appropriate offset, and then after the Tuxing on migration a "polygon" of treatment, and calculated the center of the circle each arc, calculate the diameter of each arc and the level of the intersection. According to the above three cases, each section of the diagram arc segments with the appropriate replacement, substitution, the polygon shown in Figure 3b.
Figure 2 Figure stamping parts
Figure 3 Schematic diagram of the punch generated
Figure 3b is a multi-segment line segments of the polygon outline, its vertex set V: (A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P) , V the number of vertices belonging to the original cut point set U: (B, C, D, E, F, G, J, K, M, N). Generated when the main view, U of cut points to produce some of the ridge, such as: E, F, K, etc., and some do not produce ridges, such as: B, C, D, etc., which are removed from U The cutoff point of the ridge produced after processing the set of points for the U1: (B, C, D, G, J, M, N), then V and U1 poor demand (ie, V1 = V-U1) by a new point Set V1: (A, E, F, H, I, K, L, O, P). Figure 3b is generated corresponding to the main view, the polygon vertex set V1 of each vertex in the main view corresponds to a ridge (visible or hidden), the location of ridge vertices by the corresponding X coordinate determined edge the visible and hidden lines from the corresponding Y coordinates of the vertices and the relationship between this vertex and Planes in the decision.
3. The formation of punch
To generate non-circular punch of the main view, just on the vertex set V1 processing. Any of the V1 to take that under this point of the X coordinate of this point and had identified a Y-axis parallel to the line, find this line in Figure 3b the intersection of all the segments and, based on the number of intersection and the intersection point with the spots corresponding relations, to determine the visible ridge and invisibility. For example, for point set of P points V1, over P points and the Y axis parallel to the line L1 and Figure 3b the intersection of each segment is only P points in Figure 3a by projection, no projection plane will stop this ridge, which This ridge in Figure 3a is a solid line; for V1 set of points in the L point, over L points and the Y axis parallel to the line L2 and Figure 3b the intersection of each segment are J1, K, L, J2 point, In this case, to determine the ridge is visible or hidden, must be more J2, K, J2 three intersection points with L relationship, that is, comparing the four points of the Y coordinates of the size, if the L point of the Y coordinates not less than the other three intersection of Y coordinates (ie, YL 鈮?YJ1) and (YL 鈮?YK) and (YL 鈮?YJ2), then this ridge in Figure 3a should be as solid lines (visible); as long as the other three intersection points of Y has a value of not less than the L point coordinates of Y coordinates, Figure 3: YL 鈮?YJ1, YL 鈮?YK, YJ2 鈮?YL, then this ridge should be in the dotted line in Figure 3a (not visible). By the same method, in turn on the set of points in the points V1 is calculated and compared, and the height of a given size of the punch, you can get parts in Figure 2 blanking punch, as shown in Figure 3a. In the generation after the punch, the punch will be used to generate Figure 3b delete a polygon, the offset map of the part after the graphics transferred, and then dimensioning command can be the exact size of each pixel. This process is handled automatically by computer flow chart shown in Figure 4.
Figure 4 flow chart generated punch
Third, the automatic generation of die
For non-circular die, die first need to determine the external dimensions, in determining the die size, its cavity generation method with the same non-circular punch, just before the formation of a split line be selected, find the a split line and the intersection of the entities, re-generated closed line, and then use the generated non-circular punch with the same method to generate non-circular die.
IV, Conclusion
For the design of non-circular punch and die of non-circular complex nature of using the "arc polygon" method, on the arc for discrete and find a use of computer-generated non-circular punch and die method of non-circular, achieve non-circular punch and die of non-circular automatic design, improving design efficiency and design quality.
Author: Yi-Guo Luan Shandong University (250061)
He Lianfang Lee Fai Ping Lu was shell lamp company
References
1 Sun Sheng. Computer applications in metal forming technology. Guangzhou: Guangdong Science and Technology Press.
2 Li Zhigang. Die CAD / CAM. Beijing: Mechanical Industry Press, 1994.
3 in the Shanghai level. Blanking die die CAD in the automatic generation of shape. Metal Forming Process, 1997, (2).
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