Preforming is an intermediate molding process whereby the reinforcement is assembled in the shape of the part to be molded. This helps to ensure uniform properties in a composite product and speed the molding cycle.

Most common are directed fiber preforms made by chopping multi-end roving with a binder resin and applying it on top of a molded screen. Held in place with vacuum pressure, the screen is placed into an oven to dry and activate the binder.

Another method uses continuous filament mat with a thermoformable binder.

Complex preform assemblies can be made using combinations of materials and fabrics in bladder presses or under vacuum. Resin binder, adhesive or mechanical (plastic staples) can be used.