Plastic Injection Molding

50 to 100,000+ Parts

Molds and Moldings

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Plastic Injection Molding Service

At Star Rapid we specialize in producing high-quality plastic injection molded parts and mold tools. We offer machining and finishing services to make tools from a variety of materials, and can produce 50 to 100,000+ finished parts in a wide variety of plastics.

With advanced material verification and quality processes we can ensure your tools and parts exceed your expectations. If you’re ready to start your next project, upload your product design information for a competitive injection molding quote today.

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How Plastic Injection Molding Works

Plastic injection molding is by far the most common way to produce large volumes of finished plastic parts for every kind of commercial and industrial use. Molten resin is injected under high pressure into the cavity of a metal die and then rapidly cooled, forming a solid shape. A single cycle to make a finished part may take anywhere from a few seconds to minutes depending on part complexity and size.

Advantages Of Plastic Injection Molding

Plastic injection molding provides several different advantages. These include the ability to rapidly create large volumes of parts, a variety of plastic materials, high surface quality and the creation of long-lasting tools.

Thousands of plastic materials
to choose from

Make large
volumes fast

Stable and reliable
process

Excellent
surface quality

Overmolding for more
design options

Tools can last up to
millions of cycles

The Plastic Injection Molding Process

Once your plastic injection mold tools are ready, the molding process consists of the following basic steps:

Step 1. The plastic resin comes in raw pellets. These are dried to the right moisture content, and then if necessary they can be blended with pigments or master batch colorants.

Step 2. The dried pellets are poured into the hopper of the molding machine. A reciprocating screw inside the barrel of the machine will transport these pellets towards the mold.

Step 3. Within the barrel, the pellets are mixed and heated until fully molten, forming the liquid resin.

Step 4. The heated mold closes automatically and resin, under great pressure, is injected through a gate and into the mold cavity.

Step 5. The mold is cooled to solidify the part inside.

Step 6. The mold opens and the part is ejected to begin a new cycle.

Cutaway diagram of plastic injection molding machine

” Star took the utmost care to create our tooling and
consulted with us every step of the way. “

Lee, Glass on the Grass

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Plastic Injection Molding Resources

Design For Manufacturing

It’s important that your product idea is design suitably for manufacturing. Learn more about designing for manufacturing.

Plastic Injection Molding Materials

We offer a range of materials for your mold tools and injected parts. Learn more.

Color Consistency

Challenges can arise when trying to achieve color consistency in your parts. Read our color consistency white paper to learn more.

Visual Quality Standards

Learn more about the visual quality standards we apply to plastic injected molded parts to ensure high quality.

Cause And Avoidance Of Sink Marks

Learn about what causes sink marks in plastic injection molding and how to avoid them in this white paper .

One Man One Mold Service

OMOM provides injection tooling in half the time by streamlining the process using one machinist who owns the project from start to finish.

Rapid Tooling Service

We make hard tooling (cores and cavities) from a variety of materials to suit your budget, order volume and time to production. Specialty metals can also be ordered on request. Learn more about our rapid tooling service.

Plastic Injection Molding Tolerances

All plastic material will expand and contract under the influence of heat and moisture. Our tolerance guide will give more general information on the characteristics of most common resin types for typical part features.

We will work closely with you to optimize your designs for manufacturing. We will indicate any areas where poor design may produce thermal stress, shrinkage, warping, etc. Consult our design guide for more information on common defects and how to avoid them.

Unless otherwise specified, we comply with the DIN 16742 standard tolerances for plastic injection moldings. Read about the visual quality standards that we apply to injection molded parts.

Plastic injection mold tool at Star Rapid

Plastic Injection Mold Tool

Injection Molded Pen prototypes from Star Rapid

Production Of Injection Molded Parts

Plastic Injection Molding Quickfacts

What plastic is used in injection molding?
Virtually any type of plastic can be used in the injection molding process. There are thousands of thermoforming and thermosetting plastics to choose from for your project. Check out our list of frequently used materials.

What is the plastic molding process?
Resin in the form of plastic pellets is mixed and heated until it’s melted. Under high pressure this liquid plastic is injected into the hollow cavity of a mold tool and allowed to cool, forming a solid part that is then ejected from the cavity to begin the next cycle.

What are the advantages of plastic injection molding?
Once a tool is made, plastic injection molding is the fastest and most cost-effective way to make up to hundreds of thousands of finished parts.

How long does it take to make an injection mold tool?
Depending on the complexity of the design and possible heat treatment, a plastic injection mold tool can be made in five days to two weeks.

Plastic Injection Molding Articles

4 Design Tips to Improve Plastic Injection Molding

We love to help our customers improve their product designs by offering insights gleaned from actual case studies. Recently, we worked with one customer to help them build two multi-cavity molds for a product that will be used in a high temperature...

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How Pressure Affects Your Plastic Injection Molded Parts

There are many types of pressure involved when making a plastic injection molded part. We’ve explained the importance of clamping pressure, so now let’s look at injection, holding and back pressure. It’s important for a product developer to understand how...

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