Injection Molding

Plastic injection molding mass produces repeatable parts in quick succession. The parts are made by injecting a thermoplastic into a mold cavity and ejecting a final part.

Why use injection molding

Use injection molding for its low labor costs, minimal post processing and ability to accommodate high tolerances. The process is popular for high production runs not only because of the consistent part quality, but because the price-per-part decreases with higher quantities. In particular, injection molding works well if you need:

• Repeatable parts
• Parts with good mechanical properties
• High production speeds and volumes
• Low scrap rates

How injection molding works

• Thermoplastics in the form of flakes, shavings or pellets moves from the hopper to the injection molding screw
• The injection molding screw rotates and melts the thermoplastic, which is then injected into the mold
• Once the molten thermoplastic has filled the mold, it cools and hardens
• Finally, ejector pins eject the completed part from the mold

Popular applications

High volume production

Injection molding is ideal for production runs anywhere north of the thousands. Manufacturing a million parts is also possible if your tooling is compatible with the tolerances and material.

Consumer-facing products

Injection molded materials have been refined to be consumer-facing. As such, the process is ideal for manufacturing consumer-facing products or parts in high volumes. Example parts include bottle caps, combs and toys.

Considerations for injection molding

Tooling

Designing and manufacturing an injection mold is its own project. Although the cost of injection molding generally decreases with higher production runs, tooling costs still need to be budgeted. The costs will include designing, manufacturing, testing, validating and maintaining the mold.

CNC machining is popular for manufacturing a mold thanks to its efficiency and reliability. Just make sure you select a tool steel that can withstand the demands of your application, such as corrosive materials (e.g., PVC) that’ll run through it.

When to consider additive instead

Although injection molding is highly reliable for producing thousands to millions of parts in succession, additive is a great alternative for manufacturing complex parts at low volumes, like when you’re considering mass customization or transitioning from prototyping. Two additive processes that can produce quality customer-facing parts in these low volumes are Carbon digital light synthesis (DLS) and stereolithography (SLA).

Discuss your manufacturing needs with our team by requesting a quote to see if injection molding works for your application.