A Hot Runner Mold is similar to a hot glue gun.  Material is heated to a molten state,  then it  is dispensed at the tip to the desired area.  Parts can be small single gated, or large and multi-gated.  Hot Runner Molds have many unique advantages over "Cold Runner" molds.

    While Hot Runner Molds are typically more expensive than  "Cold Runner" molds, the cost of the mold  can be offset in other ways.  Thermoplastic  Hot Runner Molds can reduce costs due to :

 No scraping of the the runner.  As the term implies, the runner in a Hot Runner mold  stays in a molten state at all times (no regrind). 
    
Reducing the cycle time.  In a Cold Runner mold the runner typically has the largest cross sectional area, therefore, the runner takes longer to  solidify.  Eliminating the runner reduces the overall cycle time.  Furthermore, injection time is reduced due to the shot size being  reduced by the elimination of the runner.

    Hot Runner Molds have the ability to improve both part and mold  design with flexibility of gating locations, which provides options for cavity orientation.   Pressure drops are greatly reduced due to the balanced melt flow as the temperature is consistent from the machine nozzle to the gate.