Plastic injection mold mold design needs to shrink water according to the shrinkage rate of different materials, and the Casting die basically has no shrinkage, the size of the mold cavity is large, and the product size is large; the biggest difference between the two molds is the glue. The gate of the die-casting mold is different from the injection mold, and the high pressure of the split-flow decomposition flow is required. The material path and feed port of the die-casting mold are generally much larger than the plastic, so it is difficult to modify, especially the aluminum alloy die-casting mold, which uses a piston-type injection to fill the mold cavity, the handle is large, and the plastic mold is injection-molded. The machine is screwed and is a small hole.
Die casting molds have a high injection speed, usually a section of injection pressure, and the injection pressure of the die-casting mold is large, so the template requirements are relatively thicker to prevent deformation.
Plastic molds are usually injected in several stages to keep pressure. The die-casting mold is a two-plate mold (I have not seen a 3-plate die-casting mold for a while). The product structure of the plastic mold is different. The three-plate mold is common. The number of times and the order of the mold are matched with the mold structure.
Our die-casting molds usually do not use square thimbles, cylinders, oblique pins (high temperature and good fluidity of the solution), which are easy to be stuck, resulting in unstable mold production. The first runner is not the same as the die-casting mold flow path, and the GATE area of the feed is required. According to the weight and weight of the product, the general GATE should not be as thick as possible. The thickness of the product should not exceed 75%. The die-casting method is only one kind of plastic mold. It can be used as a plastic mold. ), the horn tip feed, the direct feed of the big nozzle.
Casting die do not require quenching because the temperature in the cavity during die-casting exceeds 700 degrees.
Therefore, each molding is equivalent to quenching once, and the cavity becomes harder and harder. The general injection mold should be quenched to above HRC52. The die-casting mold should be nitrided in the general cavity to prevent the alloy sticking cavity. Because the die-casting mold is relatively corroded, some customers require the outer surface of the mold to be blue.
At the same time, the parting surface of the die-casting mold has higher requirements, because the fluidity of the alloy is much better than that of the plastic.
The high-temperature and high-pressure flow will be very dangerous to fly out from the parting surface; compared with the injection mold, the active matching part of the die-casting mold (such as the core puller) with a larger clearance, the high temperature of the die casting process will cause thermal expansion, if the gap is too small, the mold will be stuck. No matter the kind of mold, the gas in the sealed cavity can not be discharged when it is injected, which will lead to dissatisfaction of the material or the burning of the product. The injection mold can be exhausted by the thimble, the parting surface, etc. The mold must be opened with a venting sump and a slag collection bag (collecting the chilled material head).
The strength of die-casting products is better than that of plastic parts, but the same as the plastic parts, such as wall thickness should be even, BOSS column meat thickness of 1.2MM or more does not need to add ribs but the bottom must be added R angle, corners should also add R angle.
The other is that the die-casting mold should be repaired frequently, and the mold must be tempered after the mold is fixed. The overflow value is a value of how much the plastic product will overflow under the gap (that is, the running edge).
The overflow value of ABS is 0.04mm; the overflow value of PC is 0.06mm; the overflow value of PA is 0.015mm; the overflow value of POM is 0.04mm, and the overflow value of PBT+15%GR is 0.03mm; PBT +30%GR has an overflow value of 0.02mm; PMMO has an overflow value of 0.065mm; PVC has an overflow value of 0.07mm; AS has an overflow value of 0mm, and the die-casting mold has a burr of 0.05~0.06 or so. The parting surface of the mold has higher requirements because the fluidity of the alloy is much better than that of the plastic. It is very dangerous to fly the high temperature and high pressure from the parting surface.
In addition, plastic injection molds and die-casting molds are different in the steel used;
Plastic mold manufacturing generally uses 45# steel, 718H, S136 and other steel, while the die-casting temperature is high (about 670 degrees), the mold material and cooling requirements Higher, generally mainly used 3Cr2W8V, 8407, DAC55, SKD61 heat-resistant steel.