Injection Molding

What is Injection Molding?

First developed in 1872 by two brothers seeking an alternative to ivory in the production of billiard balls, injection molding has grown more sophisticated over the last 100 years, taking advantage of technical and material advances to become one of the most versatile techniques for mass production. At its heart, it remains an elegant and simple process. 

Thermoplastic pellets are heated to a liquid state, injected into a mold, allowed to cool in place, and then ejected. While it sounds quite basic, very complex and intricate shapes and products can be manufactured quickly and precisely with very little material waste.

Injection molding is the process of choice for companies looking to produce repeatable parts with strict mechanical requirements. It’s a popular option for high-production runs, not only because of the consistent part quality, but because price-per-part decreases with higher quantities. 

With Fast Radius, companies can expect low labor costs, minimal post-processing, high production speeds and volumes, and low scrap rates.

Producing parts with injection molding

 At Fast Radius, we’re always striving to do our jobs more efficiently. That means working closely with each of our customers — from design and prototyping through to post-production and fulfillment — to ensure that they receive high-quality parts that are made affordably and delivered on short timelines.

6 steps in the injection molding Process

  1. Clamping: Injection molds are typically made in two, clamshell-style pieces. In the clamping phase, the two metal plates of the mold are pushed up against each other in a machine press.
  2. Injection: When the two plates of the mold are clamped together, injection can begin. The plastic, which is typically in the form of granules or pellets, is first melted down into a complete liquid. Then, that liquid is injected into the mold.
  3. Dwelling: In the dwelling phase, the melted plastic fills the entirety of the mold. Pressure is applied directly to the mold to ensure the liquid fills every cavity and the product comes out identical to the mold.
  4. Cooling: In the cooling stage, the mold should be left alone so the hot plastic inside can cool and solidify into a usable product that can be safely removed from the mold.
  5. Mold opening: In this step, a clamping motor will slowly open the two parts of the mold to make for a safe and simple removal of the final product.
  6. Ejection: With the mold open, an ejector bar will slowly push the solidified product out of the open mold cavity. The fabricator should then use cutters to eliminate any waste material and perfect the final product for customer use.

Max. part size

• 2000 x 1500 x 800 mm
• 78.7 x 59.0 x 31.5 in

min. feature size

• 5 x 5 x 5 mm
• 0.2 x 0.2 x 0.2 in

best achievable tolerance

• +/- 0.05 mm
• +/- 0.002 in


• As low as 2 weeks for T1 samples
• After T1 sample approval, lead time for < 10,000 parts is as low as 1 week

Tool validation

• Standard process is to produce a small set of T1 samples for approval before initiating full production

Max. press size

• 1400T

Min. order size

• 100 parts and $5000

Setup fee

• $500 per mold per order (applies to sample runs after initial T1 samples or engineering changes)


• Molds with aluminum cavity and core with a shot life of 5,000-10,000 shots
• Typically machined in 2 weeks


• P20 steel tool with shot life up to 1M shots
• Ability to integrate side-pulls or cam-actions
• Typically machined in 3 weeks

Multi-cavity or family molds

• Multiple identical cavities or family of parts machined into a single tool
• Allows for more parts to be produced per shot, minimizing unit costs

INSERT molding

• Inserts are placed into the mold and molding occurs around them to extend tool life for critical features
• Allows for inserts such as helicoils to be molded in your design


• Premade parts are placed into the mold and molded over
• Allows for multi-material injection molding

Most common materials

Other supported materials

Additives and fiber

Acrylonitrile Butadiene Styrene (ABS)Nylon (PA 6)UV absorbers
Polyethylene (PE)Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS)Flame retardants
Polypropylene (PP)Polyurethane (PU)Plasticizers
Polycarbonate (PC)Polymethyl Methacrylate (PMMA/Acrylic)Colorants
High Density Polyethylene (HDPE)Carbon fibers
Low Density Polyethylene (LDPE)Glass fibers
Polystyrene (PS)
Polyvinyl chloride (PVC)
POM (Acetal/Delrin)
Polyethylene Terephthalate (PET)
Thermoplastic Elastomer (TPE)
Inquire for additional options

Additional information

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Finishing/Post-Processing Options

Pantone color matchingWe can produce to any SPI standard (glossy, matte, rough, very rough)
RAL color matchingPad printing
Physical sample color matchingInserts (e.g. heat stake inserts)
Mold-tech textures also available
Ultrasonic welding
Silk screening
Light assembly
Protective packaging / film

Let’s make your injection-molded parts. Right now.

FR 228x68 1

Achieved a 55% decrease in production cost.

Made possible with Fast radius

Every day we’re working with the world’s leading product manufacturers to make the parts that matter most to their businesses.

Common injection molding Applications

Highly reliable and efficient, plastic injection molding is one of the most cost-effective methods for producing large numbers of precise, consistent components. 

From the cover of remote controls to surgical instruments used in hospitals, from water bottle lids to interior elements of airplanes, plastic injection molding is used to manufacture billions of products every year.

Injection molding creates nearly identical parts with detailed features in rapid succession. This process is typically a good option for:

High-volume production runs

Produce nearly identical parts quickly with low tooling costs.

FR Capabilities Icon Libary HighVolumeProductionRuns

Consumer-facing products

Materials available with high-quality finishes.

FR Capabilities Icon Libary Consumer facingPproducts

Injection molding advantages and challenges

Injection molding is an incredibly useful manufacturing method often leveraged to create large numbers of identical parts. The high cost of tooling the hardened metal molds means that the parts must be produced at high volumes in order for the project to prove cost-effective. 

However, developments in manufacturing processes and technology now enable product teams to economically create rapid injection-molded parts in smaller quantities and to provide efficient bridge tooling solutions.

One reason injection molding is so prevalent is that a wide range of materials is available for the manufacturing process, making it possible to fabricate products to strict specifications. 

For example, a design might call for rigidity or flexibility; UV stability; heat, chemical, impact, or fracture resistance; flame retardancy, or bio-compatibility. Hardness and weight are also considered, along with material cost. Designers and engineers take advantage of combinations and customizations to create unique parts to meet highly complex or unusual application needs.

AdvatnagesChallenges 01


  • Excellent production speed
  • Low cost per part
  • High precision
  • Excellent surface finishes
  • Exceptional strength
  • Multi-material manufacturing
AdvatnagesChallenges 02 1


  • High startup costs
  • Design limitations

Injection molding resources

Learn more about the injection molding services we offer at the Fast Radius resource center.

Plastic injection molding: From material options to when to use it
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Choosing the right material for your injection-molded part
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Urethane casting vs. injection molding
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