What are the advantages and disadvantages of hot runner system applications?

Advantages of the runner system

(1) No sprues, no post-processing required, making the whole forming process fully automated, saving working time and increasing efficiency.

(2) Low pressure loss. The hot runner temperature is equal to the injection moulding machine nozzle temperature, avoiding surface condensation of the raw material in the runner and resulting in low injection pressure loss.

(3) Repeated use of sprues will degrade the plastic properties, while using a hot runner system without sprues reduces the loss of raw materials, thus reducing the cost of the product. Uniform temperature and pressure in the cavity, low stress in the plastic part, uniform density, and better products than normal injection molding system can be injected in a shorter molding time under a smaller injection pressure. For transparent parts, thin parts, large plastic parts or highly demanding plastic parts can show its advantages, and can produce larger products with smaller models.

The nozzles are standardised and series designed, with a wide range of nozzle heads available for interchangeability. The unique design and processing of the electric heating ring can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plates, temperature controllers, etc. The design is exquisite, diverse, easy to use, stable and reliable in quality.

Shortcomings of the hot runner system application

(1) The overall mould closure height is increased, the overall height of the mould is increased due to the addition of hot runner plates etc.

(2) Heat radiation is difficult to control, the biggest fault of hot runners is the heat loss of the sprue, a major issue that needs to be addressed.

(3) There is thermal expansion, thermal expansion and contraction is a problem we have to consider when designing.

(4) The cost of mould manufacturing has increased, the higher price of standard fittings for hot sprue systems has affected the popularity of hot sprue moulds.