Brief introduction of four processes of cold heading processing
1, restraint stamping
When the distance between the shape and the edge of the inner hole is less than the thickness of the plate, the inner diameter is greater than half the outer diameter, and the height is more than 1.5 times the inner diameter, the binding punching effect is better. Due to the close distance between the shape and the edge of the inner hole, the force of the punching needle will affect the shape, and the size of the shape will also change. In order to prevent changes in the shape size, this part of the shape must be constrained. Due to the effect of binding force, the stamping part is in a state of compressive stress, in this state of punching pressure stress, take the appropriate gap can get all bright belt stamping effect.
2, cut extrusion forming
Generally, the forming of the bolt head is made by cold heading plastic processing, and the cutting and extrusion forming process has more advantages than the swelling process. Before cutting and extrusion forming, the blank must be shaped, and the blank that meets the process requirements can be obtained by shaping. The size of the blank must be paid attention to, the shape of the blank before extrusion should be determined according to the situation of the part, and the shape of the blank that is conducive to the flow of the material should be used.
If the blank size is too large, that is, the cutting and extrusion margin is too large, the required cutting and extrusion force is larger, which is easy to reduce the life of the cutting and extrusion die, increase the possibility of accidental damage to the die, and consume raw materials; The cutting and extrusion allowance is too small, the corners of the parts are easy to fall off after cutting and extrusion, the shape is incomplete, and the appearance quality is not satisfactory.
The mold structure focuses on the design and processing of the cutting and extrusion film, the working size of the cutting edge is best controlled in the lower limit, the Angle of the cutting and extrusion die should be suitable, the cutting edge must be ground and polished, the roughness Ra0.025 to Ra0.050μm, with the highest life.
3, drawing and forging forming
The protruding thick wall parts formed by cold extrusion and the cup-shaped shaped parts formed by deep drawing are combined into one. The fasteners formed by the composite forming method of deep drawing and compression are characterized by the head protruding forming and the wall thickness increasing.
4, local forming
There are two concepts of upsetting forming, one is the whole upsetting, that is, the force on the end face of the whole product; The second is local upsetting pressure, that is, only the necessary part has an acting pressure. Overall forming, due to the large processing area, high forming load, the need for large tonnage punching machine, for local forming, can be used lower load to get the necessary plate thickness changes, in the hole, groove forming is widely used.
① Step parts
Take the joint as an example to explain the main points and applications of forming, engineering design: according to the design drawing machining – annealing – phosphorus saponification – extrusion (semi-closed extrusion and forming step).
② Fine local forming
For the need of locking and chip removal, there are 1 to 3 scraping grooves for some setting screws, which can be processed by extrusion process, and the representative is the forming of the scraping grooves for automotive bolt assemblies.