Types of compression molding processes

Release time:2025-06-09 16:58:14

The molding process can be divided into the following types based on the physical state of the reinforcing material and the variety of molding materials:

(1) Fiber material molding method: Pre mixed or pre impregnated fiber shaped molding material is put into a metal mold and molded into composite material products at a certain temperature and pressure.

(2) Crushed fabric molding method: Cut the scraps of glass fiber cloth or other fabrics, such as burlap, organic fiber cloth, asbestos cloth, or cotton cloth, soaked in resin adhesive solution into small pieces, and then heat and press them in a mold to form composite material products. This method is suitable for forming products with simple shapes and general performance requirements.

(3) Fabric molding method: Two or three-dimensional fabrics pre woven into the desired shape are impregnated with resin glue and then placed in a metal mold to be heated and pressed to form composite material products.

(4) Laminated molding method: Cut glass fiber cloth or other fabrics pre impregnated with resin adhesive into the desired shape, and then heat or press them in a metal mold to form composite material products.

(5) Wrap molding method: Continuous fibers or cloth (tape) pre impregnated with resin adhesive solution are wrapped around a core mold using a dedicated winding machine to provide a certain tension and temperature, and then placed in the mold for heating and pressure to form composite material products.

(6) Sheet plastic (SMC) molding method: Cut and cut SMC sheets according to the requirements of product size, shape, thickness, etc., then stack multiple layers of sheets and place them in a metal mold to heat and press to form the product.

(7) Pre formed billet molding method: First, a pre formed billet with similar shape and size of short cut fiber finished products is placed into a metal mold, and then a prepared adhesive (resin mixture) is injected into the mold to form at a certain temperature and pressure.

(8) Directional auxiliary molding: The main stress direction of the unidirectional prepreg product is oriented and laid, and then molded. The fiber content in the product can reach 70%, which is suitable for molding products with high unidirectional strength requirements.

(9) Mold powder molding method: Mold powder is mainly composed of resin, filler, curing agent, coloring agent, and release agent. The resin used is mainly thermosetting resin (such as phenolic resin, epoxy resin, amino resin, etc.), and thermoplastic resin with high molecular weight, poor flowability, and high melting temperature that is difficult to inject and extrude can also be made into molding powder. The molding process of molding powder and other molding materials is basically the same, and the main difference between the two is that the former does not contain reinforcing materials, so its product strength is lower and it is mainly used for secondary load-bearing parts.

(10) Adsorption preform molding method: The glass fiber is pre molded into a preform with a structure similar to the molded product using adsorption method (air adsorption or wet slurry adsorption), then placed in a mold and poured with resin paste, and molded at a certain temperature and pressure. The material cost used in this method is relatively low, and longer short cut fibers can be used, which is suitable for forming complex shaped products and can achieve automation, but the equipment cost is relatively high.

(11) Batch molding method: Batch molding material (BMC) is a fiber-reinforced thermosetting plastic, typically a fully mixed batch prepreg composed of unsaturated polyester resin, short cut fibers, fillers, and various additives. The addition of low shrinkage additives to BMC greatly improves the appearance and performance of the product.

(12) Felt pressing method: This method uses resin (mostly phenolic resin) to impregnate glass fiber felt, then dries it into pre impregnated felt, cuts it into the desired shape, and places it in a mold. It is heated and pressed to form the product. This method is suitable for forming thin-walled large products with simple shapes and little variation in single thickness.