The design specification
The design of die casting must take into account seven aspects: wall thickness of die casting, casting fillet and demould slope of die casting, reinforcement, the minimum distance of casting holes and holes to the edge of die casting, rectangular holes and slots on die casting, embeddings in die casting, and processing allowance of die casting.
Code for design of fillet for casting
Usually the intersection of each part of the die casting should be rounded (except the parting surface), which can make the flow of metal filling smooth, gas is easier to discharge, and can avoid cracking due to acute Angle. For die castings requiring electroplating and finishing, the rounded corners can be uniformly coated to prevent paint accumulation at sharp corners. The fillet radius R of die casting should not be less than 1mm in general, and the minimum fillet radius is 0.5mm.
Specification for design of inserts within die castings
First of all, the number of inserts on the die casting should not be too much; Secondly, the connection between the insert and the die casting must be firm, and the grooving, convex, knurling and so on are required in the insert; Thirdly, the insert must avoid sharp corners to facilitate placement and prevent stress concentration in the casting. If there is serious electrochemical corrosion between the casting and the insert, the surface of the insert needs coating protection. Finally, heat treatment of castings with inserts should be avoided, so as not to cause volume changes due to phase transition of the two metals and loosen the inserts.
Design specification for wall thickness of die castings
Since thin-walled die castings have higher strength and better compACTness than thick-walled die castings, the principle should be followed in die casting design: THE wall thickness should be reduced as much as possible while ensuring sufficient strength and rigidity of the casting, and the wall thickness should be kept uniform. Practice has proved that the wall thickness design of die-casting parts is generally 2.5-4mm, and the parts with wall thickness over 6mm are not suitable for die-casting production. Die-casting wall is too thick, wall is too thin on the performance of casting quality: if the casting wall is too thin in the design, it will make the metal welding is not good, directly affect the strength of the casting, and will cause difficulties to the molding; When the wall is too thick or seriously uneven, it is easy to produce shrinkage and cracks. On the other hand, with the increase of the wall thickness, the internal pores and shrinkage defects of the casting also increase, which will also reduce the strength of the casting and affect the quality of the casting.
Design specification for machining allowance for die castings
Usually, due to the limitation of the die casting technology, some of the die casting dimension precision, surface roughness, or shape tolerance can not meet the drawing requirements, enterprises should first consider to adopt such as light, and extrusion, plastic and other finishing processing method to repair, when finishing processing can’t completely solve these problems, It should be mechanical processing of some parts of the die casting, it should be noted here that in the process of mechanical processing should be considered to choose a smaller processing allowance, and try to avoid the surface affected by the parting surface and the activity of molding for the blank datum, so as not to affect the processing accuracy.
Specification for design of demoulding inclinations of die castings
When designing die casting, there should be a structural slope on the structure. When there is no structural slope, there must be a demoulding process slope where necessary. The direction of the slope must be consistent with the direction of the casting release.
Die cast metal material
The main die casting alloy materials are tin, lead, zinc, aluminum, magnesium, copper and so on. Zinc and aluminum alloy are the most widely used, followed by magnesium and copper alloy. Currently in the electronic industry with zinc, aluminum, magnesium alloy mainly.
Die cast zinc alloy
Zinc alloy molten fluidity is very good, melting point is only 365 degrees. Can be used for all kinds of post-processing, such as electroplating. So widely used, before the mobile phone industry is also used a lot, but because the ratio is large, the corrosion resistance is gradually eliminated by aluminum alloy. Use most when belong TO wei YU industry. Alloys 2, 3, 4, 5, and 7 are commonly used, and the most widely used is alloy 3.
Die cast aluminum alloy
Aluminum alloy has low density, but high strength, close to or more than high-quality steel, good plasticity, can be processed into a variety of profiles, with excellent electrical conductivity, thermal conductivity and corrosion resistance, widely used in industry, the amount of only steel. The specific weight of aluminum alloy is only about 1/3 of iron, so it is very important in all walks of life, especially in the lightweight process of aircraft, ships, cars, electronic instruments and so on.
Commonly used are Al-Si-Cu system, common are ADC12 (A383), ADC10 (A380) and so on. There are also Al-Si system, Al-Si-MG system, Al-Mg system. Aluminum-titanium alloy is modified by adding titanium metal to the above material, adding titanium metal can significantly improve the mechanical properties of the product.
Die cast magnesium alloy
Magnesium alloys are alloys based on magnesium and other elements. Its characteristics are: low density, high specific strength, large elastic modulus, good heat dissipation, good shock elimination, impact load capacity than aluminum alloy, organic and alkali corrosion resistance. Magnesium has about 2/3 the proportion of aluminum and 1/4 the proportion of iron. So it is widely used in mobile phones, communication equipment and other electronic equipment, auto parts, medical equipment.
The most widely used is magnesium aluminum alloy, followed by magnesium manganese alloy and magnesium zinc zirconium alloy. Common brands used are AZ91D, AM60B, AM50A, AS41B and so on.
Die casting mould
Die casting mold must be made of hot die steel, commonly used steel are: H13, 2344,8407,8418, SKD61, DAC, FDAC, etc.
Mold structure: (back die, front die) mold frame, mold kernel, guide post, guide sleeve thimble, cylinder, diverter, gate sleeve, slider, oblique guide post, hydraulic core pulling.
Tooling processing equipment: milling machine, CNC machining center, wire cutting (slow wire), (mirror) spark machine, grinding machine, lathe, welding repair equipment.