Fluid Assisted Injection Molding

Injection molding processes can often be improved by pressurizing the melt in the mold cavity with either gas or water at an appropriate point in the molding process.  Both of these processes can be used with Ticona’s engineering resins.  Ticona can provide processing assistance at molding trials.

Gas-Assisted Injection Molding
Large stress-free components can be produced in this process.  In operation, the mold is partially filled and then gas is introduced into the melt stream (near the point of injection) at a very high pressure.  The gas pressure pushes the plastic into the tool to pack it out, and a hollow cross-section is created in the part.  Gas assisted injection molding offers several advantages including weight savings, fast cycles, improved flow length and dimensional stability, as well as reduced warpage and sink marks.  Gas injected parts also have a higher strength/weight ratio.

In general, the minimum amount of resin, gas injection time and gas pressure necessary to produce a good part should be used.  Gating should be designed to facilitate melt flow and gas entry points should allow the gas to flow in the same direction as the resin.  The gas injection point leaves a hole in the part and so may need to be located in an inconspicuous location.  Gas channels should be cut steel safe until the tool has been sampled and the process is optimized.  

Water-Assisted Injection Molding
This process is somewhat similar to the gas assist process, however water is used as the medium.  Since water is incompressible, it can produce better-shaped hollow parts with good control and smoother surfaces.  It can also reduce the cycle time due to the additional cooling from the water.