Below, the editor of Zhejiang Baifu Electromechanical introduces a type of mold to you. This type of mold is called a "drawing die," which is also one type of mold. Generally, it refers to various metal wire dies, including wire drawing dies that can draw optical fibers. As we all know, all molds have a fixed hole in the center, which can be round, square, octagonal, or other special shapes. So, in the design of drawing parts processing molds, which factors affect the drawing coefficient? Below, the editor will take you through it.
I. Processing characteristics of wire drawing dies
1. The clearance between the punch and die should be uniform. For drawing dies without a guide device, the same part should be placed to adjust the punch and die positions correctly; for drawing dies with guides, it is also necessary to ensure uniform clearance between the punches.
2. The material has good compactness, and there is elastic deformation during the drawing process. Before the punch and die are hardened, trial stamping and trimming should be carried out. The material is easy to process and has good wear resistance. After the drawing die passes the trial, the blanking die is manufactured according to the trial condition.
3. For drawing dies without guide equipment, it is required to place the same part to adjust the punch and die positions correctly; for drawing dies with guides, uniform clearance between punches should also be ensured during assembly.
4. When processing a drawing die, the drawing die is usually made first. After the drawing test passes, the blanking die is made according to the trial condition. The machinability of mold parts and the convenience of mold maintenance should be fully considered in the design.
5. The processing quality of drawing dies is receiving increasing attention, so processing the drawing die into parts is also an important factor in improving mold quality.
II. Characteristics of tensile molds
1. The concept of drawing.
(1) Drawing: pressing a sheet metal into a hollow part (with almost no change in thickness).
(2) Drawing process: The material is transferred from a flat surface (flange) to the side wall of a cylinder (box shape), causing significant changes in the planar dimensions.
(3) Drawing ratio: The ratio of the drawn diameter to the blank diameter (indicating the degree of deformation from blank to workpiece).
2. Main factors affecting the drawing coefficient:
(1) Mechanical properties of the material (reduced strength - elastic deformation; tensile strength - plastic deformation; elongation coefficient; reduction of area).
(2) Relative material thickness.
(3) Number of drawing operations.
(4) Drawing method.
(5) Radius of punch and die fillets.
(6) Cleanliness of the drawing surface, lubrication conditions, clearance, etc.
(7) Stretchability.
III. Arrangement of Drawing Operations
1. For parts where the drawing depth is less than the diameter: the height can be increased by reducing the cylindrical diameter, thereby gradually decreasing the corner radius.
2. For material parts with equal thickness and diameter: the height can be kept constant to reduce the corner radius, if the small cylinder diameter is gradually reduced.
3. For parts with large flanges and extremely small corner radii: these should be obtained through multiple forming operations.
4. For oversized flanges: if necessary, use the expansion forming method.
To embody the principle of "constant flange," the flange formed during the first drawing should not participate in all subsequent drawing deformations. In wide-flange drawing, the amount of material initially entering the die (i.e., the material forming the wall and bottom) is 3–10% more than the material drawn in the final operation.
Note: When the value is higher, use the upper limit within the range; when it is lower, use the lower limit. The excess material will return to the flange during subsequent multiple drawing steps, causing the flange to thicken without cracking, which can be corrected through restriking/sizing. Therefore, strict control of each drawing height is essential during the drawing process.