Hot runner (runnerless) systems are seeing more demand in today's high-speed, high-volume molding operations due to higher material prices, a need to reduce cycle time, reduce scrap rates, and increase overall productivity and costs to manufacture, as compared to a "cold runner" system. Particularly in applications in which regrind cannot be introduced (virgin resin only applications) back into the material to produce the parts, hot runner systems have an advantage in reducing the amount of material used as well as the amount of scrap created by the runner system.

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1. What is the hot runner mold?

ACE Lu,owner of Mould Precision Co., Ltd, says that a "hot runner system is used to eliminate or lessen the use of runners which must be removed from an injection mold with the molded parts. If runners are eliminated, the point of entry to the mold cavity (gate) will have a hot drop (nozzle) suspended in the gate area. This is necessary to retain controlled heat sufficient to promote continuous moldability in the drop area directly adjacent to the mold cavity."

2. What is the hot runner system?

Tom Li, enginner of Mould Precision Co., Ltd, says that the system has "a manifold suspended behind the drops" that is electrically heated, "as are the drops, in order to contain heat in the hot manifold assembly. The system is also suspended so as not to transfer unwanted heat into the rest of the mold. The mold itself is designed to dissipate heat in order to solidify the molded parts as quickly as possible to lower cycle times."

3. What is the mold that use for hot runner system?.

Hot runner technology is becoming a "fully-accepted" and indeed the preferred method of gating many multi-cavity molds. They are replacing more and more of the older runner methods especially the 3-plate systems. In fact, older, existing 3-plate molds can often be quite easily rebuilt into hot runner molds."

While hot runner systems are typically used on large, multi-cavity molds (32-cavity and up), many companies are choosing to put hot runner systems on smaller multi-cavity molds (8- or 16-cavity) because of the increased productivity and reduced scrap. Catoen writes that "In some molds, often for smaller products with a large number of cavities, but also with larger ones, a combination of cold and hot runner systems can be of great advantage.

4. Some of the advantages of a hot runner system vs. a cold runner system:

  • No runners to separate from the molded parts.
  • No runners to either dispose of or regrind and reprocess with the possibility of introducing contamination into the virgin material if being mixed with virgin.
  • Not drops carry consistent heat at processing temperature directly into the cavity.
  • Cooling time for thin sectioned parts is shorter due to the absence of thicker, longer cycle-dependent runners.
  • No need to provide robotics for runner removal.
  • Plasticized material (shot size) is reduced by the runner weight.
  • Lower injection pressures may be realized during packing stages due to heated gate areas in hot runner systems.
  • Less clamping pressure required versus two plate cold runner molds.
  • Sprue sticking and nozzle freeze-off associated with cold runners is eliminated.
  • A cleaner molding room can be realized without dealing with regrind, an advantage particularly in clean-room molding environments.
  • 5. What is the hot runner mold MP used?

    MP specialized in hot runner mold building with any of MOLD MASTER, HUSKY, HASCO, DME, YUDO, INCOE, THERMOPLAY, SYNVENTIVE etc.

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