Plastic Injection Molding

50 to 100,000+ parts

Molds and Moldings

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Plastic Injection Molding

At Star Prototype, we specialize in high quality custom plastic injection molding and mold tool making. Plastic injection molding is by far the industry’s most common way to manufacture parts, especially when making larger quantities. We provide custom molding for 50 to 100,000+ parts as well as a wide range of other manufacturing and finishing services to complete your project. Read more about plastic injection molding or contact our team for a quote and to talk about your next project.

Plastic Injection Molding Parts

What is Plastic Injection Molding?

Plastic injection molding involves melting granular plastic pellets into a liquid form and then compressing this liquid into the empty cavity of a mold tool. The plastic will retain the shape of the mold as well as the surface texture of the walls of the cavity. After an optimized injection and cooling phase, the now solidified plastic part is ejected and the molding cycle is repeated. This molding cycle can take from as little as a few seconds to several minutes depending upon part size, molding resin and part design.

Prototype Camera with Injection Molded Parts

Advantages of Plastic Injection Molding

  • We have thousands of different types of plastic are available for you to choose from, for a wide range of mechanical and cosmetic properties.
  • Plastic injection molding makes more economic sense for larger volumes. For smaller volumes we might recommend other services like CNC machining, vacuum casting or 3D printing depending on the needs of your project.
  • Hundreds of thousands of moldings can be produced from a single mold.
  • Your part can have excellent surface quality finishes in a wide range of polishes and textures.
  • Overmolding is available to combine different types of plastic in one piece. It is ideal for lightweight parts that are immune to corrosion.

Plastic Injection Molding Machine

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Mold Tool Production

Materials such as aluminum 7075, pre-hardened tool steel such as P20 and fully hardened tool steels like H13 are most commonly used when making your mold tool. The material used will depend on the number of parts you wish to produce.

Aluminum Tooling

Aluminum tools are quickest to produce and most cost effective. Aluminum is softer and therefore suited to smaller volumes. For larger volume production, and for aggressive resins or part geometries requiring thin blades or ribs it’s best to use harder materials that are more durable.

Steel Tooling

Steel tools are tougher and more durable but can take longer to produce. These are suited for larger volumes or when injecting abrasive or corrosive plastics that would damage aluminum molds.

  • Pre-hardened tool steel is used for quantities of 100K pcs and more, depending on plastic material and part geometry. We use P20 and NAK80 stress-relieved steel.
  • Fully-hardened tool steel is the most durable and can be used for millions of injected parts. H13 hardened steel is ideal for full production volumes or when injecting abrasive engineering-grade plastics.

One Man One Mold

In a hurry for quick-turnaround plastic injection mold tools?  Our One Man One Mold (OMOM®) service was created to provide injection tooling in as little as half the time of conventional tools.  There are some restrictions, so check here to see if OMOM® is right for your next project.

Injection Molding Tools

Part Production

When producing parts, a variety of polymers are available including thermoforming plastics, thermosets and some elastomers. Mold tools and the injection process are both carefully engineered to match the unique requirements of each material in order to produce the highest quality finished parts. Thermoforming plastics are relatively softer, more flexible, less durable, and easily recycled whereas thermosetting plastics are more rigid, durable and expensive and cannot be repaired or recycled once formed. Find out more about materials you can choose from by looking out our materials sheet and tolerance guide.

Plastic Injection Molded Parts

Tolerance Guide Sheet

Unless otherwise specified, we comply with the DIN 16742 standard tolerances for plastic injection moldings. We need to know your requirements in advance so that we can manage key features in the tooling and molding process. As a general rule, high-precision features can only be achieved on select areas of the tool depending on the application. Downloaded our Plastic Injection Molding Tolerance Guide.

Design for Manufacturing

When developing a new product it is important to make sure you design for manufacturing. If you don’t you could run into costs and delays when it comes time to produce your parts. To help our veteran plastic injection molding engineer, Ken Adams, is putting together a range of white papers addressing the most common design for manufacturing issues. Here is the first one on the cause and avoidance of sink marks.


At Star Prototype we can use virtually any resin that you require for plastic injection molding. We can purchase special materials from the local market, or we can import them. Please check out our list of thermoforming resins to get an overview of the standard materials that we use.

Color Consistency

Color consistency for injection molded parts poses a challenge. This becomes apparent when mating parts in any assembly where colors need to match perfectly. For more information read our white paper about the challenge of color consistency.

Are you ready to start your next project?

Once you send us your CAD file, our experts will review it to ensure manufacturability. When our engineers look at your design they will double check draft angles, wall thickness, corner angles, material type etc. Our engineers will also make sure the right materials are combined with the correct design considerations to ensure your next project meets and exceeds your expectations. Contact us to get your free quote.


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