Plastic injection mold steel

What is plastic injection mold steel?

Plastic injection mold steel is the plastic mould steel used for plastic mold core and cavity and plastic injection mold base.

How to choose plastic injection mold steel for plastic mold base?

Plastic injection mold base

Plastic injection mold base

In China the default steel used for injection mold base is S5OC, it is similar steel as 1050 and 1055 steel in US and 1.1730 steel in Europe.  Normally for the small quantities plastic injection mold is okay to use this steel. But for the long term production and the mold life more than 1,000,000 shots, we suggest to use P20 steel for the plastic injection mold base. For the long term production mold, you can also choose the 420SS for the mold base as well. We will have more details article to talk more about plastic injection mold base steel in future on our this blog.

How to choose plastic injection mold steel for plastic injection mold core and cavity?

To understand this, we have to understand what will affect the steel selection for plastic mold, this is as following:

  • Plastic resin used for plastic injection molding  

For the corrosive plastic resin, we should choose the 420SS stainless steel for core and cavity. For the plastic resin with fiber glass, we should choose the through hardness steel for injection mold core and cavity to improve the injection mold life and rub attrition, normally we can also choose the rub attrition through hardness steel for the long term production mold and plastic resin with fiber glass mold.  We should understand different plastic resin performance and plastic mould steel performance to define the plastic injection mold steel for core and cavity.

  • Plastic injection mold life

For the injection mold life less than 300,000 shots and plastic resin is not special, we can choose the preharden plastic mold steel for core and cavity. For the mold life more than  300,000 shots and less than 1,000,000 shots, we have to choose the through hardness steel for core and cavity.  For more information for this topic, you can review our post injection mold base and plastic injection mold life. We will also have the SPI injection mold standard to talk more about this in future on our this blog.

  • Plastic injection molding parts surface finishing

Regarding the high polishing or mirror polishing plastic molding parts,we should choose the 420SS etc. stainless plastic mould steel for core and cavity. For the texture surface, there is not so much limiting factor on plastic mold core and cavity steel. You can also understand this more to read plastic mold steel specification as below.

LKM plastic injection mould steel    SCHMOLZ+BICKENBACH injection mould making steel

  • Plastic injection mold size

For the large size plastic injection mold to produce large transport plastic frame, automotive large parts, large plastic basket, large plastic barre and  large plastic garbage can etc. , normally it is to use preharden injection mold steel such as P20, P20+Ni and P20HH.

  • Plastic injection mold concept or structure

Normally the core and cavity use the different hardness or use different steel to reduce the friction force, this also apply to the sliders and angle lifters. We may talk this more once we are talking about plastic injection mold design.

  • Plastic injection molding parts tolerance

For the precise plastic injection mold, normally we suggest to use the through hardness steel for the core and cavity, also for the mold base A, B plate as well as ejection plate, we suggest to use P20 or harder steel than S50C. Also we talk about that we prefer to choose single cavity or less than or just it is 4 cavity mold for the accurate plastic molding parts mold.

About Hedy Yeh

Major in machinery and tooling in university from 2001 to 2004; Worked for plastic mold design, mold manufacturing and mold and production project management from 2003 to 2008; Working for mold marketing and mold project management from 2008 till now My facebook page