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  • Many doctors are professional in hot runner system
  • Over than 20 engineers have more than 10 years experience in hot runner
  • Specializes in mold flow analysis
  • Expert in thermal analysis
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By the heating process to runner and gate, melted plastic could keep at a stable temperature and pressure. Melted plastic could fill cavity with less resistance. In simple words, hot runner system could be treated as an extension of nozzle for delivering plastic to each gate.

  • Hot runner features:

The main function is that it can provide the plastic flow from the machine nozzle to the mold cavity by a precision control system. Through the temperature and sequence control system to the runner and gating (manifold and nozzles), we can get better part quality of plastic products, efficiency production speed and lower production costs, also complicated products is available. Compare to the car: the hot runner system is like the oil system within the car. A good-design and good-control of oil system, it can provide fuel-efficient, fast, stable, and suitable for a variety of terrain and climate. Therefore hot runner system could simplify and improve molding process. To save energy and be more environmental are the main features of hot runner system.

  • Energry save and environmental protection:

There is no scrap generated in the molding process of hot runner system. It solve the problem of environmental and process efficiency.

Energry save and environmental protection


The work of scrap recycle is eliminated. Therefore the crush process for scrap is not necessary, simultaneously noise is avoid from crusher. Basically, hot runner system is helpful in resources saving, energy saving and noise prevention.

  • Provide mutiple gates for injection molding. Hot runner system helps extend injeciton from one nozzle to mutiple gates.
  • Before start, the plastic inside the runner and gates are solid, the manifold and the nozzles must be heated to the molten state. Therefore, we have to ensure the proper design of the power requirement of the system (normally there is 15~30 min. allowed heat-up time)
  • The temperature distribution is not even, because the temperature found is only a specific area. It is not easy to detect the uniform representative situation.
  • It is not easy to have proper pressure control to each gate.
  • There is always heat loss from hot tip, manifold, and spacer pads. To avoid heat loss and keep thermal isolation is an important issue.
  • During molding cycle, different temperature will induce thermal expansion and contraction to the nozzle and the manifold. The calculation of thermal expansion is the hot runner design is one of the important issues.
  • The problem of leakage is always a nightmare when the hot runner system is used, so to keep the all connections sealed in whole hot runner system is also one of the important issue.
  • Hot runner system is a closed system. Once there is impurity inside of the system, it will block gate. There is no other way but to disassemble whole system to remove it. The impurity could be metal filings or other things.
  • No drooling, no string, no blockage by gate freeze or clogged, and get smooth injection molding process is the most important issue.
  • No mater how much recycled material is used, material property will be worse than raw materail. It brings a disadvantage in quality control in cold runner system.
  • To color change is a difficult task for hot runner. Even though some plastic is able to overcome this task. But for most engineer plastics, there is still a tough issue.
  • Reduction in raw materials consumption, reduction of finishing work on molding (sprue removal and trimming), and reduction in number of regrinding machines, savings on labor, energy consumption (because of no waste recycling process).
  • Faster cycle time: faster the cooling time (because of no sprue and runner), simplify the molding process without to take out the runner, and easy for automation.
  • It can increase shot size capability. It is unusual for the volume of the runner to cause the mold to exceed the shot capacity of the molding machine. Also the hot runner will reduce the required clamp tonnage as there is less reactive force on the clamp.
  • Energy savings: only need more power during the start of nozzle and manifold in order to heat-up the plastic inside the runner, once the mold began to run, the power to be input is small and can be negligible.
  • Simplify the design of certain types of mold and enable automated production.
  • There is greater freedom to choose better location to gate the big products, which allow to have a more uniform filling with a smaller loss of temperature and pressure in mold cavities.
  • A less pressure loss that could help injection molding more efficiently.
  • It provides continuous packing effect and could help reduce the shrinkage.
  • By temperature control and valve gate sequence control, hot runner system could make flow balance more easily.
  • A sequence controled valve gate system could help produce a no weld line part.
  • More cost in mold built
  • Need more equipments such as temperature controller and sequence controller
  • Leakage problem to overcome
  • Operator need to be trained
  • Trouble shooting
  • Thermal degradation problem of plastic
  • Ununiform temperature distribution
  • Difficult to control pressure at gate
  • Heat loss problem
analysis of hot runner waste
Illustrations
  • A: No hot runner inside, the most scrap, the highest pressure loss and longer cycle time needed.
  • B: Build one nozzle, sprue can be eliminated but imbalanced flow.
  • C: Build a manifold and two nozzles, get balanced flow but a little scrap occur from cold runner.
  • D: With a manifold and 8 nozzles for each part, no resin waste, fasten cycle time and better part quality.