Hot Runner Molding

American Technical Molding provides plastic injection molding using hot runner molds, a process that offers the lowest cost per part when a large number of plastic parts need to be manufactured quickly.

Primary advantages of hot runner molding include:

  • Materials cost savings – no runner to regrind or reprocess
  • Least expensive cost / piece
  • Reduction of energy costs
  • Shorter, faster cycle times – no runners to cool
  • Smaller machines – reduced shot volume into runners
  • Automated processing – runners do not need de-molding
  • Gates at the best position for economical design
  • Elimination of runners means
    • No runners to remove or regrind
    • Reduces the possibility of contamination
    • Lower injection pressures
    • Lower clamping pressure
    • Consistent heat within the cavity
    • Shorter cooling time
    • Shot size reduced
    • Cleaner molding process
    • Eliminates nozzle freeze

Hot Runner Molding: Precise Computer-Controlled Accuracy and Advanced Processes

Hot runner molds are usually connected to needle valve nozzles, which are activated with precise computer-controlled timing for accurate reproduction of parts.

This allows for a number of advanced processes, including:

  • Multi-Cavity Molds – cavities with different geometries and/or volumes
    • Parts that belong together produced in one mold
    • Injection valve opening and closing can be adjusted to the conditions of each individual cavity
    • Injection pressure and holding pressure may be adjusted  independently of each other
  • Controlled Volume Balancing – a weld line can be shifted into a non-critical area of the molded part
  • Stack Molding – multiple parting lines for additional cavities in a given area

Hot-Runner Systems: Weigh the Cons with the Pros

There are, however, a few disadvantages to hot runner systems that need to be considered:

  • Hot runner molds are more complex and expensive to build than cold runner molds
  • Higher initial start-up costs than cold runner systems
  • Complex initial setup prior to running the mold
  • Higher maintenance costs – more susceptible to:
    • Breakdowns
    • Leakage
    • Heating element failure
    • Wear caused by filled materials
  • Risk of thermal damage to sensitive materials
  • Elaborate temperature control required