- Constrained stamping
Punching holes with a distance between the appearance and the edge of the inner hole that is less than the thickness of the plate, an inner diameter greater than half the outer diameter, and a height greater than 1.5 times the inner diameter, have better results with constrained stamping. 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, resulting in changes in the size of the shape. In order to prevent changes in overall dimensions, it is necessary to keep this part of the appearance in a restrained state. Due to the constraint force, the stamping part is in a state of compressive stress. In this state of punching compressive stress, taking appropriate gaps can achieve a stamping effect that is entirely bright.
- Cutting extrusion forming
Usually, the forming of bolt heads adopts cold heading plastic processing, and the cutting extrusion forming process has more advantages than the expansion forming process. Before cutting and extrusion forming, the blank must be reshaped to obtain a blank that meets the process requirements. The size of the blank must be taken seriously, and the shape of the blank before extrusion should be determined based on the condition of the parts, using a blank shape that is conducive to material flow.
If the size of the blank is too large, that is, if the cutting and extrusion allowance is too large, the required cutting and extrusion force will be greater, which can easily reduce the service life of the cutting and extrusion mold, increase the possibility of accidental damage to the mold, and consume raw materials; If the cutting and extrusion allowance is too small, the parts may easily fall off corners after cutting and extrusion, resulting in incomplete shape and unsatisfactory appearance quality.
The focus of the mold structure is on the design and processing of the cutting and extrusion film. It is best to control the working size of the blade at the middle and lower limits, and the angle of the cutting and extrusion mold should be appropriate. The blade must be ground and polished, with a roughness of Ra0.025 to Ra0.050 μ m. Has the highest lifespan.
- Drawing and forging forming
A fastener formed by combining a raised thick wall part formed by cold extrusion with a cup shaped shaped part formed by deep drawing, using sheet metal as the material and using a composite forming method of deep drawing and compression. Its forming characteristics are the formation of a raised head and an increase in wall thickness.
- Local forming
There are two concepts of upsetting forming, one is full upsetting, which means that there is a force acting on the end faces of all products; The second is local upsetting, which only applies pressure in the necessary parts. Full forming, due to its large processing area and high forming load, requires a large tonnage stamping machine. For local forming, lower loads can be used to obtain necessary plate thickness changes, which is widely used in the formation of holes and grooves.
① Step parts
Taking the joint as an example to illustrate the key points and applications of forming, engineering design: machining according to the design drawing – annealing – phosphorus saponification – extrusion (forming steps through semi closed extrusion).
② Micro local forming
For the needs of locking and chip removal, there are 1-3 chip scraping grooves for some set screws, which can be processed using extrusion technology. A representative example is the formation of chip scraping grooves for automotive combination bolts.