In the previous issue, I introduced the first three types classified by molding, and today I will continue to introduce the last three types classified by molding.

(1) Pressure injection molding

Also known as die casting. It is to add plastic raw materials into the preheated feeding chamber, and then put the pressure column into the feeding chamber to lock the mold. Pressure is applied to the plastic through the pressure column, and the plastic melts into a fluid state under high temperature and high pressure, and enters the cavity through the gating system to gradually solidify into a plastic part. This molding method is also called transfer molding. Injection molding is suitable for all plastics that are lower than solid. In principle, plastics that can be compressed and molded can also be molded by injection molding. However, it is required that the molding material has good fluidity in the molten state when it is lower than the solidification temperature, and has a greater solidification rate when it is higher than the solidification temperature.

(2) Hollow molding

It is to fix the tubular or sheet-shaped billet that is still in the plasticized state by extrusion or injection in the forming mold, and immediately inject compressed air to force the billet to expand and stick to the wall of the mold cavity. After being cooled and shaped, it is demoulded to obtain the desired hollow product. Plastics suitable for hollow molding are high-pressure polyethylene, low-pressure polyethylene, hard polyvinyl chloride, soft polyvinyl chloride, polystyrene, polypropylene, polycarbonate, etc. According to the different molding methods of the parison, hollow molding is mainly divided into two types: extrusion blow molding hollow molding and injection blow molding hollow molding. The advantage of extrusion blow molding is that the structure of the extruder and the extrusion blow mold is simple. The disadvantage is that the wall thickness of the parison is inconsistent, which may easily cause uneven wall thickness of the plastic product. The advantage of injection blow molding hollow molding is that the wall thickness of the parison is uniform and there is no flash. Since the injection parison has a bottom surface, the bottom of the hollow product will not be stitched and seamed, which is not only beautiful but also high in strength. The disadvantage is that the molding equipment and molds used are expensive, so this molding method is mostly used in the mass production of small hollow products, and it is not as widely used as the extrusion blow molding hollow molding method.

(3) Die-casting mold

Die casting mold is also called transfer molding mold. Add plastic material to the preheated feed chamber and apply pressure to the press column. The plastic melts under high temperature and high pressure, and enters the cavity through the gating system of the mold, and gradually hardens and forms. This molding method is called die-casting molding, and the mold used is called a die-casting molding mold. This kind of mold is mostly used for the molding of thermosetting plastics.

In addition, there are foam molding molds, glass fiber reinforced plastic low pressure molding molds and so on.

The classification of plastic molds has been explained for everyone. If you have any questions, you can leave me a message or pay attention to us. We are a professional manufacturer integrating production and sales.