Hollow molding The tubular or sheet material obtained b […]
The tubular or sheet material obtained by extrusion or injection and still in a plasticized state is fixed in the molding die, and the compressed air is immediately introduced to force the material to expand and stick to the wall surface of the mold cavity. After cooling and setting, the mold is released, which is a processing method of the desired hollow product. Suitable plastics for hollow molding are high pressure polyethylene, low pressure polyethylene, hard polyvinyl chloride, soft polyvinyl chloride, polystyrene, polypropylene, polycarbonate, and the like. According to the different molding methods of the parison, the hollow molding is mainly divided into two types: extrusion blow molding hollow molding and injection blow molding hollow molding. The advantage of the extrusion blow molding hollow molding is that the structure of the extruder and the extrusion blow mold is simple, and the disadvantage is that the wall thickness of the parison is inconsistent, and the wall thickness of the plastic product is likely to be uneven. The figure on the right is a schematic diagram of the principle of extrusion blow molding. The advantage of injection blow molding is that the parison has a uniform wall thickness and no flash. Since the injection parison has a bottom surface, the bottom of the hollow product does not have a seam and a seam, which is not only beautiful but also high in strength. The disadvantage is that the molding equipment and the mold used are expensive, so this molding method is mostly used for mass production of small hollow products, and there is no extensive extrusion blow molding method in use.
(6) Die casting mold
Die-casting molds are also called transfer molding molds. The plastic raw material is added to the preheating feeding chamber, and then the pressure is applied to the pressing column. The plastic is melted under high temperature and high pressure, and enters the cavity through the casting system of the mold, and is gradually hardened. This molding method is called die casting molding, and the mold used is used. Called die casting mold. This type of mold is mostly used for the molding of thermosetting plastics.
In addition, there are foam molding dies,pet mold, glass fiber reinforced plastic low pressure molding dies and so on.