Selection of Mold Materials for Transparent Plastic Products

In the selection of mold materials for transparent plastic products, the choices can be divided into two major types based on the requirements for transparency and surface finish. According to the SPI-A1 standard, the following material selection strategies can be defined:

For products that allow for a less stringent surface finish, there is a broader range of material options available. In such instances, the mold cavity (female mold) and core (male mold) should be crafted from steels that can attain a mirror-like polishing finish. Steels like NAK80 pre-hardened or similar grades are preferred, offering the benefit of being production-ready without the need for additional heat treatment.
When it comes to products that demand the highest level of transparency, the selection of materials becomes more critical. The use of S136 high-mirror polishing steel or its equivalent is advisable. These materials necessitate a process of vacuum hardening and tempering following the rough machining phase to enhance their physical attributes, typically achieving a hardness level between 45 to 52 HRC.

These two material selection approaches reflect the differentiated material performance requirements in the manufacturing process of transparent plastic products. The appropriate selection of steel not only ensures the transparency standards of the product but also guarantees the mold’s longevity and production efficiency.