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Theoretical analysis of plastic film application
1. The material is stainless steel sUs304, the material thickness accounts for 1.5, and all parts of the parts are required to have no oil, debris, scars and cracks. According to the analysis, we design the processing process as follows: cutting, forming, trimming, punching, etc., where forming is a key process, both to ensure the part forming structure, size requirements, and to ensure the surface quality of the parts. It can be seen that the shape of the part is complicated, and the forming deformation of the whole part is very complicated. The deformed material is unevenly distributed on the periphery, and the part A with a large amount of deformation engraves the part of the figure, causing additional deformation stress. Increase the deformation resistance; areas with small deformation will cause protrusions and wrinkles on the working wall and flange due to material deformation. In order to solve such problems, it is usually applied to apply a proper blanking force. Moreover, since the material of the part is a stainless steel plate, the cold work hardening effect is serious, and the required forming force is large, in order to prevent the flange portion from generating wrinkles during the drawing process, the blanking force must be increased during the drawing process, thereby causing parts and molds. The surface contact pressure is very high, the high pressure changes the rheological properties of the commonly used lubricant, it is difficult to form an effective lubricating film between the workpiece and the mold, the workpiece is isolated from the mold surface, and the relative sliding between the part and the mold is generated. Huge friction causes serious wear of the die and the binder ring, increases the drawing force and tensile stress on the sidewall of the workpiece, and presents a stress concentration zone, resulting in thinning cracking. At the same time, due to the compatibility of stainless steel and die steel, it is high. Under the combined influence of surface pressure, large contact area and high contact temperature, the formed bonding layer gradually forms a bonding tumor on the surface of the mold, causing severe scratches and wrinkles on the surface of the part. In order to solve the above problems, it is necessary to adopt corresponding technological measures to effectively isolate the workpiece from the surface of the mold under the working condition with large blanking force to reduce friction and wear.
2. Application of plastic film Based on the above analysis, we have adopted a process of replacing the lubricant with a polyethylene plastic film. Polyethylene is a thermoplastic, soft in texture, has a certain tensile strength, low heat distortion temperature, and good fluidity. The workpiece is isolated from the surface of the mold by a certain thickness of polyethylene plastic film. Due to the small sliding friction coefficient of polyethylene, the plasticity is strong and the thermal deformation is large, which can effectively isolate the workpiece and the mold surface under the action of large blanking force and reduce friction. Force and wear phenomena. At the same time, in the deep drawing process, due to the low deformation temperature of the polyethylene, the deformation of the polyethylene increases as the drawing temperature increases, and the film is deepened with the part within a certain range of deformation. The shape of the surface changes during operation, and the part is always covered on the surface of the workpiece to protect the part, ensuring that the part is in the process of deep drawing. There is a layer of isolation between the surface of the mold, which effectively ensures the surface quality of the workpiece, improves the lubrication conditions in the stress concentration area, and reduces the material thinning in the area. At the same time, due to the low compressive strength of polyethylene, under the action of large working pressure, a certain thickness of polyethylene film can decompose the deformation resistance of the material around the workpiece, and different requirements for the blanking force, so that the blanking force can be adjusted. The range is increased to effectively overcome the wrinkling of the edges and the wall of the cylinder.