Ten Common Plastic Molding Processes

Plastic Molding: Injection Molding

Injection molding, also known as injection forming, is a plastic molding process in which granular or powdered materials are fed into the hopper of an injection machine. The materials are heated and melted into a flowable state and pushed by a screw or piston through the nozzle and gating system into the mold cavity, where they harden and form. Key factors affecting the quality of injection molding include injection pressure, injection time, and injection temperature.

PLA Molding: Blow Molding

Blow molding is a PLA molding method where molten thermoplastic material is extruded from an extruder and clamped into a mold. Air is then blown into the material, expanding it under air pressure until it fits the mold cavity's surface. It is then cooled and solidified into the desired shape. Blow molding includes film blowing and hollow blow molding.

Plastic Molding for Profiles: Extrusion Molding

Extrusion molding, also called extruding, is a plastic molding process primarily used for thermoplastics, though certain thermosets and reinforced plastics with good flowability can also be used. The molten plastic is pushed by a rotating screw through a die with the desired cross-section, shaped by a calibrator, and cooled to form rigid profiles.

PLA Molding for Sheets and Films: Calendering

Calendering is a PLA molding process in which plastic materials are passed through a series of heated rollers. Under compression and stretching, they are flattened and extended into thin films or sheets.

Plastic Molding: Compression Molding

Compression molding is mainly used for thermosetting plastics. Based on material conditions and processing equipment, it is divided into two types: compression molding and laminating molding.

Plastic Molding: Transfer Molding

Transfer molding, also known as transfer compression molding, is a plastic molding process developed from compression molding and resembles injection molding. In transfer molding, the material is plasticized in a feed chamber before entering the mold cavity through the runner system, unlike injection molding, where plasticization occurs in the barrel of the injection machine. The key difference: compression molding involves loading before closing the mold, while transfer molding generally closes the mold before loading.

Plastic Molding: Rotational Molding

Rotational molding is a plastic molding technique where plastic material is added into a mold, which is then heated and rotated along two perpendicular axes. The material melts and adheres evenly to the inner walls of the mold cavity under the combined effect of gravity and heat. Once cooled and set, the hollow product is demolded.

Plastic Molding: Drip Molding

Drip molding is a plastic molding process that takes advantage of thermoplastic polymers' ability to transition between viscous and solid states. With special tools and controlled conditions, the viscous material is shaped into the desired form, then cured at room temperature. The process involves three main stages: gel preparation, dripping, and cooling/curing.

Plastic Molding: Vacuum Forming

Vacuum forming, also called thermoforming, is a plastic molding process involving heating a sheet or plate of thermoplastic, clamping it in a frame, and then using a vacuum to pull it over a mold. After cooling for a short time, the shaped plastic product is obtained.

Plastic Molding: Slush Molding

Slush molding is a plastic molding technique where plastisol (plastic sol) is poured into a preheated mold. The material near the inner surface gels due to heat, and the remaining ungelled plastisol is poured out. The adhered layer is then heat-treated, cooled, and demolded to form a hollow product.