Hot nozzle forming moulds are made through hot runner system. During the process, the most important thing is to maintain the molten state of runners and sprues by heating. Hot nozzles hold the sol goes from splitter plates and injection sol to forming moulds. Hot nozzles used in this kind of manufacture can be one or more, while both open type and needle-valve type are available. High speed injection of hot nozzle not only increases the molding efficiency, but also leads to the different thickness of products.
A. Open type hot runners are applicable to producing most thermoplastics. It is commonly used to make connectors, cups, lens, transparent plastic shell, automobile accessories, etc.
B. Needle-valve type hot runners are suitable for making products of any size. They are usually applied to products that require high quality surface. Products with fiberglass or engineering plastics will get higher quality when making with this kind of technology. These products are mobile phones, shells, televisions, displays, CD cases, big size automobile accessories, etc.
Strong points of hot runner:
No obvious vestige on sprues.
No need to cut sprues.
Shorter molding cycle.
Filling the mould cavities to the biggest extent.
Controlling flow of colloid easily.
Weak points of hot runner:
Difficult to change color of materials.
Be liable to go out of order, especially for the heating control system.
Not applicable for heat sensitive materials.
When making large numbers of high quality products, it is wise to use hot runner system. In some cases, the best way might be combining hot runner with cold runner.
We will continue to focus on this series. The next classical mould manufacturing type is blow molding.