The design of the die casting must take into account the wall thickness of the die casting, the casting fillet and the draft angle of the die casting, the reinforcement ribs, the minimum distance between the casting hole and the hole to the edge on the die casting, the rectangular hole and groove on the die casting, the die casting There are seven aspects of the machining allowance of inserts and die castings in the parts.
1. Design specification for casting fillet
Usually, the intersection of each part of the die casting should have rounded corners (except the parting surface), which can make the metal flow smoothly when filling, and the gas can be easily discharged, and can avoid cracks caused by sharp angles. For die castings that require electroplating and finishing, rounded corners can be uniformly coated to prevent paint build-up at sharp corners. The fillet radius R of the die casting should generally not be less than 1mm, and the minimum fillet radius is 0.5mm.
2. Design specifications for inserts in die castings
First, the number of inserts on the die-casting part should not be too much; secondly, the connection between the insert and the die-casting part must be firm, and at the same time, grooves, protrusions, knurling, etc. are required on the insert; thirdly, the insert must avoid sharp corners , in order to place and prevent the stress concentration of the casting. If there is serious galvanic corrosion between the casting and the insert, the surface of the insert needs to be protected by coating; finally, the casting with the insert should avoid heat treatment, so as to avoid the phase difference between the two metals. Changes cause volume changes and loosen the inserts.
3. Design specifications for wall thickness of die castings
Thin-walled die castings have higher strength and better compactness than thick-walled die castings. In view of this, the design of die castings should follow the following principles: on the premise of ensuring sufficient strength and rigidity of the castings, the wall thickness should be reduced as much as possible. And keep the wall thickness uniform. Practice has proved that the wall thickness design of die castings is generally 2.5-4mm, and the parts with wall thickness exceeding 6mm should not be produced by die casting process. The performance of the influence of too thick and too thin walls of die castings on the quality of the castings: If the walls of the castings are too thin in the design, the metal welding will not be good, which will directly affect the strength of the castings, and at the same time will cause difficulties in forming; the walls are too thick or severely uneven On the other hand, with the increase of wall thickness, defects such as pores and shrinkage in the casting also increase, which will also reduce the strength of the casting and affect the quality of the casting.
4. Design specification for machining allowance of die castings
Under normal circumstances, due to the limitations of the die-casting process, when some dimensional accuracy, surface roughness or geometric tolerance of the die-casting parts cannot meet the requirements of the product drawings, the enterprise should first consider adopting methods such as calibration, polishing, extrusion, etc. It should be repaired by finishing methods such as shaping. When finishing cannot completely solve these problems, some parts of the die casting should be machined. It should be noted here that when machining Small machining allowance, and at the same time try to use the surface that is not affected by the parting surface and active forming as the blank reference surface, so as not to affect the machining accuracy.
5. Design specifications for the drafting slope of die castings
When designing die castings, there should be a structural slope on the structure. When there is no structural slope, there must be a process slope for demolding where necessary. The direction of the inclination must be consistent with the direction of demolding of the casting.