Plastic Molding & Forming Processes

Composite Molding Processes

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Composite Molding Processes
Autoclave Molding	Filament Winding	Pultrusion	Structural Reaction Injection Molding (SRIM)
Centrifugal Casting	Hand Lay-Up	Reaction Injection Molding (RIM)	Tape / Fiber Placement
Compression Molding	Pressure Bag Molding	Resin transfer molding (RTM)	Vacuum Bag Molding
Continuous Lamination	Pulshaping	Spray-up	Vacuum Infusion

Resin Transfer Molding

Resin transfer molding (RTM) is a low pressure closed molding process for moderate volume production quantities, filling the gap between the slow, contact molding processes and the faster, compression molding process, which requires higher tooling costs. Continuous strand mats and woven reinforcement is laid up dry in the bottom mold half. Preformed glass reinforcements are often used for complex mold shapes. The mold is closed and clamped, and a low viscosity, catalyzed resin is pumped in, displacing the air through strategically located vents. Metered mixing equipment is used to control resin/catalyst ratios that are mixed through a motionless/static mixer and injected into the mold port. Common matrix resins include polyester, vinyl ester, epoxy, and phenolics. Advantages over contact molding methods are a uniform thickness, two finished sides and low emissions. For optimum surface finish, a gel coat would be applied to the mold surface prior to molding. High quality parts produced by this method include automotive body parts, bathtubs, and containers.