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 Structural Foam Injection Molding

Structural Foam Injection Molding

Structural Foam Injection Molding is a process used to produce large plastic covers, handles, bezels and plastic structural components.

Structural foam is a process well suited for large plastic parts because the foaming gas bubbles in the resin matrix pack out the resin and reduce the incidence of sink on the show side of the plastic part. Structural foam molding parts are usually very thick, nearly 0.250” wall thickness, and are ideal for plastic structural elements that will not be in view. Parts which are in view require extensive sanding, painting, and finishing.

Structural Foam Injection Molding
Structural Foam Injection Molding Process

Structural Foam Injection Molding Process

Structural Foam is produced by mixing raw resin with a chemical blowing agent which “foams” after the mixture is introduced in an injection mold. This foaming produces very small gas bubbles which are evenly distributed throughout the resin matrix (see structural foam cross section below-left). These gas bubbles impart a marbled or swirled surface finish on the part. For this reason structural foam is best used on non-customer facing parts because the finishing required to achieve acceptable cosmetics can be prohibitively expensive.

Structural Foam Molding with Gas Counter Pressure

One way to combat the marbled appearance and swirls in the surface finish, shown above, is by employing gas counter pressure with structural foam. In this process the mold is pressurized with gas at a pressure higher than that of the foaming gas prior to the resin’s introduction in the mold (see structural foam w/gas counter pressure diagram below). When performed correctly, a smoother, glossier, and more consistent surface finish is produced.

Structural Foam Molding

Structural Foam Molding Capabilities

Mold Process Type Structural Foam
Materials ABS
ABS/Polycarbonate Blends
HIPS
PBT
Polyamide (Nylon)
Polycarbonate
Polyethylene
Polypropylene
PPA (Zytel)
PPE
Clamping Force 85 to 1500 Tons
Shot Size 5 to 291 oz.
Part Length 10" to 80"
Part Width 10" to 70"
Intended Application Plastic Enclosures
Plastic Covers
Plasic Doors
Plasic Handles
Bezels
Plasic Equipment Cabinets
Additional Molding Capabilities Overmolding
In-Mold Assembly
Traditional Injection Molding
Structural Foam Molding
Additional Services Finish Machining
Painting
Pad Printing
Heat Staking
Sonic Welding
Assembly
Packaging
Design
Engineering
Testing & Inspection CMM Dimensional Inspection
Color Spectrophotometer
Gloss Meter
Lead Time Quoted on job by job basis
Production Volume 200 - 5,000 Parts Typical
Small to Medium Size Production Runs
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