How should I choose the material for my plastic mould?

Tue Feb 28 13:20:38 CST 2023

The working conditions of plastic moulds are different from those of cold stamping moulds, which generally have to work at 150°C - 200°C. In addition to being subjected to certain pressures, they are also subjected to temperature effects. There are many forms of failure in the same mould, and even in the same mould there can be many types of damage. It is clear from the failure forms of plastic moulds that a reasonable choice of plastic mould materials and heat treatment is very important, as they are directly related to the service life of the mould. Therefore, the steel used for plastic moulds should meet the following requirements.

1)Heat resistance performance

With the emergence of high-speed molding machinery, plastic products run faster. As the molding temperature is between 200 - 350 ℃, if the plastic liquidity is not good, and the molding speed is fast, it will make the mold part of the molding surface temperature in a very short period of time more than 400 ℃. In order to ensure the accuracy of the mould in use and the deformation is small, the mould steel should have high heat resistance performance.

2) Sufficient wear resistance

With the expansion of the use of plastic products, in plastic often need to add glass fiber and other inorganic materials to enhance plasticity, due to the addition of additives, so that the fluidity of plastic greatly reduced, resulting in wear and tear of the mold, it is required to have good wear resistance.

3) Excellent cutting processability

Most of the plastic moulds, in addition to EDM processing also need to carry out a certain amount of cutting processing and clamping repair. In order to extend the service life of the cutting tool, processing hardening in the cutting process is small. In order to avoid the mold deformation and affect the accuracy, hope that the processing residual stress can be controlled to a minimum.

4) Good thermal stability

Plastic injection mould parts are often complex in shape and difficult to process after quenching, so should try to use materials with good thermal stability.

5)Mirror surface processing performance

The surface of the cavity is smooth, the molding surface requires polishing into a mirror surface, the surface roughness is less than Ra0.4μm, in order to ensure the appearance of plastic pressed parts and easy to take off the mold.

6)Heat treatment performance

In the mold failure accident, due to heat treatment caused by the accident is generally 52.3%, so heat treatment in the entire mold manufacturing process occupies an important position, the heat treatment process has a greater impact on the quality of the mold. General requirements of heat treatment deformation is small, quenching temperature range, overheating sensitivity is small, especially to have a large hardening and hardenability, etc.

7) Corrosion resistance

In the forming process may release corrosive gas heat decomposition with corrosive gas, such as HC1, HF and other corrosive mold, sometimes in the air runner mouth to make mold rust and damage, so the requirements of mold steel has good corrosion resistance.