RPM Industries LLC
plastic injection molding

Different Injection Molding Types Used for Making Injection Molded Plastic

For injected molded plastic, manufacturing companies use various injection molding types. The decision as to which one is appropriate depends on several factors including the finished part or component and the material used. Overall, an expert who creates injection molding products will consult with you about what you need along with your ultimate goals and objectives. Based on that, the expert makes the correct decision.


When you consider that multiple industries use plastics, you can understand just how critical injection molding is for manufacturing a massive selection of part and components.


Plastic Bottle Molding

Injection molding is broken down into two types: a single stage and two-stage. The single stage is a hot perform method, whereas the two-stage is a cold preform method. Of all molding techniques, plastic injection molding is the most versatile. Whether using a single-stage or two-stage process, the steps are quite similar.


Typically, injections molds are steel, although aluminum and stainless steel work for some applications. Molds also have either a screw-type plunger or ram forces molten plastic into the mold cavity where it solidifies into the shape and size of the required finished product. Once the plastic hardens and cools, the mold opens to eject the part or component. Although manufacturers can use different types of plastic, thermoplastic and thermosetting polymers are the best.


Depending on the part or component getting manufactured, injection molding machines consist of one or multiple cavities. What makes using more than one cavity unique is that the machine can produce different geometries while using just one cycle.

  • Single Stage – The injection molding process steps consist of preforms getting sent directly to the blow molding station before thoroughly cooling. The station for this is an integrated part of the same machine used for the two-stage method. For this process, there is little to no conditioning or reheating required.
  • Two-Stage – In this case, preforms get molded in a dedicated system that produces completely cooled preforms. From there, manufacturers can store, ship, and even sell them before they get blow molded by another piece of machinery. That machine reheats the preform using infrared radiation and conditions them before going through the blow molding process.


At RPM Industries, Inc., we offer the different types of injection molding, as well as other molding processes. Feel free to visit our website to learn more or call to speak with a company representative about your needs.