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Precision stretch stamping parts are common accessories in hardware tools, so what are the processing requirements for them?
1. The shape of precision stretching and stamping parts should be as simple and symmetrical as possible: in the circumferential direction, axisymmetric stretching parts will undergo uniform deformation, and the mold used at this time is also relatively easy to process, and the processability is also the best. For stretched parts of other shapes, try to avoid sharp contour changes as much as possible. For example, the rear cover of a car muffler, while ensuring usage requirements, will simplify its shape and transform the production process from multiple processes to one to two processes, reducing material consumption by half.
2. The size ratio of each part of precision stretching and stamping parts should be appropriate: it should be avoided to design flanges and deep stretching parts as much as possible, as such parts require more stretching times. For example, the difference between the upper and lower dimensions of the workpiece is too large, which does not meet the requirements of the stretching process. To make it composite, it can be divided into two parts, processed and manufactured separately, and then connected. If the workpiece cavity is not deep, but the flange diameter is large, the manufacturing difficulty is also great, and annealing treatment is needed in the middle. If the flange diameter is reduced, intermediate annealing can be avoided. The contour of the workpiece flange should preferably be similar to the contour shape of the deep drawn part. If the width of the flange is not consistent, it will not only be difficult to stretch, but also require additional processes. It is also necessary to relax the edge cutting allowance and increase metal consumption.
3. The fillet radius of precision stretching and stamping parts should be appropriate: in order to facilitate forming and reduce the number of drawing times, the fillet radius of the stretching part should be increased as much as possible. The fillet radius between the bottom and wall of the stretched part, the flange and wall, and the four walls of the rectangular part must meet the requirements.
4. The uneven thickness phenomenon of precision stretching stamping parts should be considered: the inner and outer walls of the workpiece that has been stretched multiple times or the flange surface of the stretched parts with flanges should allow for imprints generated during the stretching process. Unless there are special requirements for the workpiece, shaping or shaping methods can be used to eliminate these marks.
5. The hole positions on precision stretching and stamping parts should be reasonably arranged: set the hole positions on the main structural surface of the stretching part to maintain it in a plane, or make the hole wall perpendicular to the plane, so that punching and trimming can be completed simultaneously in one process.
6. Selection of stretching oil: In addition to considering the lubricity and cooling properties of stretching oil, the rust resistance, cost, and ease of maintenance of stretching oil should also be considered in the selection of stretching oil. Stretch oil is easy to use base oil with relatively low viscosity and add wear reducing additives, which can achieve lubrication and friction reduction, as well as good cooling and easy filtration. However, the problem with stretching oil is its low flash point, high temperature during stamping forming, easy deformation, high risk factor, and fast volatilization, resulting in higher user usage costs. Therefore, it is recommended to choose stretching oil with high compressive and wear resistance when conditions permit.
7. The dimensional accuracy of precision stretching and stamping parts should not be too high: the manufacturing accuracy of stretching parts includes the accuracy in the diameter direction and the accuracy in the height direction. In general, the accuracy of precision stretching and stamping parts should not exceed the specified values. The dimensions on the product drawing need to be indicated to ensure external or internal dimensions, and cannot be marked with both internal and external dimensions.