Structual Foam Injection Molded Plastic Parts with Solid Surface and Cellular Core Plastic Injection Molding

Structural Foam is a term commonly used to describe thermoplastic injection moulding components made by the injection moulding process which have a cellular core. A cellular plastic is one in which the outer surface is denser than the inner layers. The core of the moulding is of a honeycomb nature and less dense than the outer surface. The combination results in a moulding of a high stiffness ratio compared with non-structural foam (compact) mouldings.

Typical Materials Used
* Acrylonitrile-Butadiene-Styrene ABS
* Polystyrene PS
* Polycarbonate PC
* Polypropylene PP
* Polyvinyl chloride PVC

Typical Products Produced
* Business Machine Housings
* Point of Sale Display Components
* Business Machine Chassis Components
* Point of Sale Display
* Material Handling
* Containers Pallets

Methods of Producing Structural Foam
The Low Pressure Process
To achieve consistent quality mouldings, it is recommended to use dedicated special purpose injection moulding machines. The machines introduce a gas into the melted plastic which when injected into the closed mould tool subsequently foams the plastic material of the component being produced.
Conventional Moulding Machines
Another widely used method is the use of standard injection moulding machines with added "blowing agents" incorporated into the material. Using dry chemical blowing agents mixed in with the granules of plastic, the plastic is melted in the barrel of the machine. A measured charge is injected into the mould tool. The heat of the melted plastic causes the blowing agent to react, which forms a gas and in turn foams the plastic.

The nature of the process leaves a rough streaky surface finish on the surface of mouldings. If this is not acceptable, then a subsequent filling and painting operation is applied. Often this painted surface is of a textured type thus minimizing any irregularities in the moulded surface.

Structural Foam Benefits
There are numerous benefits to selecting structural foam or gas assist molding. Structural foam molding is an excellent conversion alternative for wood, metal, concrete, and fiberglass. It can also offer a significant ROI in comparison to other processes such as rotational molding, RIM, thermoforming, die-cast, injection, and SMC. The result is a significant reduction in cost and a vast increase in productivity. The following are the key benefits of structural foam molding:
* 20% less weight than high-pressure parts
* 3-4 times more rigid than solid parts
* Substantial cost reductions
* Low mold cavity pressure allows lower-cost tooling
* High stiffness-to-weight ratio
* High dimensional stability
* Capable of molding parts as thin as .156″ thick or greater
* Low warp and part stress
* Multiple molds can run simultaneously
* Functions as an excellent substrate for high quality painted finish applications
* Virtually any thermoplastic can be foamed.