First, choose two types of steel according to the performance requirements of the injection mold

One type is structural parts, including gating systems, guides, fixed (moving) templates, ejector parts, supporting parts, etc. The selected materials are generally medium and low carbon carbon structural steels or alloys.

The other type is molded parts. Including cavities, cores, inserts, etc., are the key components for direct molding of plastic products. The plastic mold cavity is complex, and the dimensional accuracy and surface roughness requirements are high. Corresponding requirements are put forward for the mechanical processing performance, mirror polishing and grinding performance, heat treatment deformation and dimensional stability of the plastic mold steel.

Second, the main principles for the selection of mold opening steel for injection molds

(1) It has a certain comprehensive mechanical properties. The formed parts have to withstand temperature, pressure, erosion and wear during the working process, and therefore require certain strength, plasticity, and toughness.

(2) The surface of the injection mold cavity should have a sufficiently thick hardened layer with a certain degree of hardness and wear resistance.

(3) Good machinability. The shape of plastic molds is often more complicated, and the cost of cutting processing often accounts for the majority of injection molds (generally about 75%), so good machinability is required.

(4) The mold is selected according to the size and precision requirements of the plastic products. For large-scale high-precision injection molds, when the plastic parts are produced in large batches, pre-hardened steel is used to prevent heat treatment deformation.

Third, what is the impact of the selection of injection molds on the mold?

1) Impact on the service life of injection molds

Generally, the mold with high hardness is used to open the mold, and the corresponding mold service life will be relatively long. For example, when the heat treatment hardness of steel is about HRC50, the mold life can reach 500,000 to 1 million molds. Otherwise, it is easy to wear, and the injection molded product is easy to be out of tolerance. Therefore, the selected steel must not only have good heat treatment performance, but also have good cutting performance under high hardness.

2) The impact of plastic raw materials on steel

The raw materials for injection molding and the added fillers have a great impact on the steel, especially the glass fiber wears a lot of injection molds. In addition, some plastic materials are corrosive and need to be considered comprehensively before selecting mold opening materials.

Therefore, when selecting mold materials, the processing performance should be as high as possible while ensuring the performance requirements of the mold.