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Thermoplastic Injection Molding Services

The Thermoplastic family of materials is what most people relate to when they think about Plastic Injection Molding because of the many domestic products that are produced, including items such as telephones, computers, auto parts, and appliances to name a few. Highly critical parts with specialized requirements are also made from thermoplastic materials engineered to meet specific these requirements. Components for aircraft, medical devices, engines, machinery, electrical and other industrial items are produced from engineered thermoplastics.

Plastic resins with specific properties are compounded with additives such as reinforcements (ie: glass or carbon fibers), ultra violet inhibitors, flame retardants, conductive elements, lubricants or toughening agents, to attain desired properties. Optimal properties of components molded from engineered plastics can be attained only through the proper and precise control of the molding process. Our 45 years of molding experience and investment in state of the art process control equipment ensures the best outcome for our customers' critical parts. Whether it’s high volume production for automotive use or irrigation industries or low volume for aerospace applications, Southwest Plastics is a valuable partner for your next injection molding project.

Thermoplastic Injection Molding

Injection molding is a high production method for producing a vast variety of thermoplastic parts into shapes ranging from fairly simple to quite complex. Injection mold cavities are fed with the melted plastic material which is forced under high pressure through a sprue which feeds a runner system through a gate into the cavity. The material is then cooled to the point that it is solid and then ejected from the mold as a finished part.

The injection molding machine consists of two basic components: the clamp unit and the injection unit. The clamp unit holds and clamps the tool into position while the injection unit plasticizes and injects the material into the mold which has been positioned by the clamp unit. The clamping force must be sufficient to hold the mold closed against the hydraulic pressure of the material being injected under high pressure by the injection unit. The rule of thumb is that there must be three tons of clamp force for every square inch of cavity projected area in the mold. Both units are coordinated by a computer controller on the machine which is programmed to efficiently to produce high quantities of consistent quality parts on an automated cycle.

Thermoplastic Resins

 (Delrin, Celcon
Acrylonitrile Butadiene Styrene (ABS)
Butyrate (Lucite, Plexiglas
Polyester (PBT, PET) (Lexan)
Polyether ether Keystone (PEEK)
Polyetherimide (Ultem)
Polyphenylene Oxide (Noryl)
Polyphenylene Sulfide 
Polypropylene (PP)
Polystyrene (PS)
Polyurethane (PU)
Styrene Acrylonitrile (SAN)
Thermoplastic Elastomers (Santoprene, Krayton)

Engineered Compounds

Any of the above resins can be tailored to a specific requirement by compounding in additives to enhance properties

Enhancements (Typical Additive)

Tensile strength (Glass, Carbon fibers)
Toughness (Elastomer)
U.V. resistance (Color Stabilizers)
Flame Retardance (Extinguishing additive)
Conductivity (Carbon, metal flakes)
Lubrication (Teflon, Moly)
Cost-reducing fillers (Mineral)


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