In the early stages of manufacturing, blow moulding suppliers need to determine the manufacturing materials for the molds. The manufacturing of blow molding molds should comprehensively consider the physical and chemical properties of the materials, such as thermal conductivity, corrosion resistance, strength, stiffness, etc. The main materials available for blow moulding suppliers to choose from are:

1. Steel

Blow molding molds made from polyvinyl chloride (PVC) and engineering plastics are usually made of steel because steel has excellent hardness, wear resistance, and toughness. By etching the mold cavity, the surface pattern of the product can be clearer and more beautiful. However, blow moulding suppliers also need to consider the limitation of poor thermal conductivity of steel. At this time, blow mold manufacturers need to compensate for this defect by designing cooling systems or adjusting the temperature and flow state of the cooling fluid. This type of blow mold solution is often more complex. As corrosive plastic, PVC molds should be made of stainless steel. There are various manufacturing methods for steel molds, including mechanical processing, cold extrusion, casting, or welding (for large molds). For general blow mold companies, the service life of steel molds can even reach 10 million times. When producing large-scale blow molding products, blow moulding suppliers prefer steel as the mold material. Steel is also used to manufacture blow molding parts that need to withstand wear and tear, such as blank inserts, pull rods, guide pillars, guide sleeves, and templates. When manufacturing these components, it is required to harden the steel.

2. Aluminum

In extrusion blow moulding, suppliers use aluminum materials more widely. Aluminum has outstanding advantages in its metallic properties, including good thermal conductivity, machinability, and ductility. Although it has lower density and mass, its hardness is low and it is prone to wear. However, aluminum alloys have good wear resistance. However, the toughness and plasticity of cast aluminum are relatively low, so some blow moulding suppliers choose to use steel or copper beryllium alloy to manufacture clamping blocks in molds. The service life of aluminum blow molding molds is approximately 100000 to 200000 times, which is much lower than that of steel molds. Aluminum materials have porosity and weak airtightness, sometimes infiltrating a small amount of plastic melt. Over time, this can affect the appearance and performance of blow molded products to a certain extent. The solution proposed by blow moulding suppliers is to apply sealant on the mold cavity, but the drawback of this solution is that it will reduce the thermal conductivity between the product and the mold wall.

3. Copper based Alloys

Among copper-based alloys, the most commonly used by blow moulding suppliers is copper-beryllium alloy, which has good thermal conductivity, hardness, wear resistance, corrosion resistance, and mechanical toughness. However, it has a high cost, poor mechanical processing performance, and a large weight (its density is about three times that of aluminum alloy). Blow moulding suppliers typically manufacture copper-beryllium alloy molds through methods such as mechanical processing, casting, and hot extrusion. Copper beryllium alloys with higher beryllium content have higher hardness, mainly using mechanical processing methods; Copper beryllium alloys with lower beryllium content are suitable for the manufacturing of irregularly shaped moulds. Blow moulding suppliers typically use copper-beryllium alloy to manufacture blank inserts, which are used in conjunction with aluminum molds. For molds that process corrosive plastic materials, the entire set of blow molding molds is made of copper-beryllium alloy. For example, copper beryllium alloy is not corroded by hydrogen chloride produced during PVC processing, and can also prevent scaling of water in the cooling channel, avoiding a decrease in thermal conductivity and cooling efficiency. Copper beryllium alloy molds are easy to repair through welding or inlay methods. However, after long-term use by blow moulding suppliers, beryllium is harmful to human health. Inhaling excessive beryllium dust can damage the lungs, and it is also suspected to be a carcinogen. Therefore, attention should be paid to mechanical processing and casting, and protective measures should be taken.

4. Zinc Alloy

Zinc alloy has good thermal conductivity and low cost. Blow moulding suppliers can use it to cast larger or irregularly shaped molds. The hardness of zinc alloy is lower than that of aluminum alloy, so the clamping blocks of zinc molds are usually made of steel or copper-beryllium alloy. Zinc can also be made into alloys with aluminum or copper, although its stability is improved, its corrosion resistance will correspondingly weaken.