Plastic molding method

3-1.Compressive molding

In this molding method, pressure and heat are applied after putting molding material in the mold. This is the most primitive method, and it is mainly for casting large or small products of thermosetting plastics.

3-2.Transfer molding

In compression molding, material is heated in the same mold, and it is pressurized once it has turned to fluid state, after which it is cooled and removed. However, in transfer molding, material is heated in a different pot that is a part of the mold. The melt is then pressurized into mold (cavity), and then it is pressurized and heated. This is more efficient than compression molding, and it is mainly used for thermosetting plastic, and it is suitable for molding high precision products and product inserts.

3-3.Laminate molding

In this method, resin is impregnated in the base material such as paper or cloth, and several sheets of specific thickness that are lightly dried and initially condensed, and then hat and pressure are applied by sandwiching them between heating platens. It is used in the production of thermosetting plastic sheets such as phenolic laminated sheets and melamine facing plates.

3-4.Injection molding

This molding method applies similar principles as syringe injection. Body of the syringe injection is injection molding machine, injection material is melted plastic, application of finger pressure is performed through hydraulic pressure. Though this injection pressure, the casting material flows through a narrow hole called narrow gate, forming a shape. Its main feature is that a large quantity of molded items of uniform quality can be produced in short time. From the injection of material to removal of molded item, the entire process can be fully automatic. Molded items with complex structures and high dimensional accuracy can be created. On the other hand, mold as well as equipments are very expensive. Therefore, considering the depreciation expense of mold, it is not suitable for low-volume production.

3-5.Extrusion molding

As the name suggests, in this method, material is extruded from the mold. It resembles extruding mayonnaise from a container. Mayonnaise corresponds to the melted raw material, outlet part corresponds to mold, which the pressure required for extrusion is applied by rotating a screw. Just like a cookie-cutter, products made by extrusion molding have same cross section irrespective where it is cut. Moreover, it is possible to create an endless succession. Water pipes and standard materials such as rods and plates are made by this molding method.

3-6.Blow molding

In this molding method, an extruded pipe (parison) is sandwiched from both sides with halved dies, so that air will be blown simultaneously, thereby gluing the melt resin to die. It was conceptualized from the molding of glass bottles. It is applied for molding containers like bottles.