The hot runner is heated to ensure that the plastics of the runners and gates remain in molten condition. Why do we recommend it? If the plastic injection product is large without using hot runner system, it is prone to occur the defect of shortage shot. Since there is heating rod and heating ring near or in the center of the runner, the entire flow path from the nozzle exit of the injection molding machine to the gate is kept in a high temperature state, so that the plastic through the whole path remains in a molten condition. Therefore there is no need to take out the condensed resin after shutdown and just heat the runner to required temperature after restart. In general, hot runner processes are sometimes referred to as hot manifold systems.
Advantages and disadvantages of hot runner technology
1. Save raw materials and reduce costs.
2, shorten the molding cycle and improve machine efficiency
3. Improve the surface quality and mechanical properties of the product.
4. It is not necessary to use a three-plate mold to use a point gate.
5. It is economical to form a single product with a edge gate.
6. Improve the degree of automation.
7. The gate can be controlled by a valve gate.
8. The quality of the injection molded parts of the multi-cavity mold is the same.
9. Improve the surface appearance of injection molded products.
10, Use low injection pressure, and effectively reduce the warp of thin-walled products.
However, each technology has its own shortcomings, and this is the same with hot runner technology:
- The mold structure is complex, building and maintenance costis high
- It takes a while for theinjection processto be stable, resulting in more waste of defect products at start.
3. When there is molten resin leakage and heating element failure, product quality and production schedule might be greatly effected. This disvantages could be solved by by using quality heating elements, hot runner plates and nozzles . Meanwhile, carefully maintain these components during use.