The proper die steel should be selected according to the application requirements. If it is a prototype, it is not necessary to use hardened die steel. In most cases, pre hardened steel or aluminum is usually used to reduce costs and facilitate mold adjustment during prototyping. These soft metals can also mold enough test pieces and prefabricated parts. Pre hardened die steels (such as P-20 or nakr-55) are often used to make large-scale dies, because it is impractical to harden die steels in large-scale applications.
In the case of high production, it is necessary to use hardened die steel for core and cavity. S-7, H-13 and stainless steel 420 are the most commonly used steels. S-7 is an excellent die steel, which can be used in production and operation for a long time. If high melt and mold temperatures are required, H-13 steel should be used. The H-13 can also be used to make hot runner manifolds. The tempering temperature of H-13 is very high, and it can withstand high mold processing temperature without affecting the hardness.
Stainless steel is the best choice for die steel if the application field requires high wear resistance or there will be a lot of condensation in the environment. It can be made of A2, asp23 or D-2 steel with high wear resistance.
All die steels can rely on certain types of plating protection to prevent wear and corrosion. Only stainless steel can be repaired by welding and machining. For the existing coated steel, only after removing the coating can it be repaired. The coating shall be repainted after repair.
Surface finish
Depending on the aesthetic requirements, customer requirements and functions of the parts, the surfaces of the formed parts may vary. From SPI ා 1 mirror like high gloss surface to texture surface obtained by etching technology, LNP composite can have almost any type of surface finish of formed parts. It is important to understand that some materials have improved performance with a certain mold surface finish. For example, the demoulding performance of polypropylene in the mold with matte surface is significantly better than that of the mold with high gloss surface. It is difficult to achieve high gloss in the resin with a large amount of filling.
exhaust
In order to improve the mold performance to the greatest extent, exhaust is an important part of the molding cycle. When the thermoplastic material enters the mold cavity, the air in the mold cavity needs to be discharged. Vent holes are usually located in the last filled area, close to the suture and on the runner system. The additional exhaust holes along the periphery of the parting line can greatly improve the overall exhaust performance. The residual gas in the mold is shown as scorch marks on the formed parts. The basic experience is that the gas in the mold must be able to be discharged at the same rate as the plastic entering the mold cavity.
The pore depth varies depending on the material used - usually amorphous thermoplastic materials require a larger pore depth due to their high viscosity.
