Plastic Injection Molding

Proto Labs provides quick-turn thermoplastic injection molding often used for prototyping, bridge tooling and short-run manufacturing up to 10,000+ parts. We use advanced aluminum alloy molds that allow us to eliminate the costly and time-consuming custom engineering that normally goes into the development of tooling. Proto Labs offer hundreds of engineering-grade resins that produce molded parts that are strong and can have excellent finishes.

Quick-turn injection molding uses the industry standard production process for parts, so it’s an excellent predictor of manufacturability when you move to large-scale production. At Proto Labs, we support an ever-increasing maximum part size and degree of complexity, and continue to introduce new materials that help designers and engineers make better products.
25 to 10,000+ Parts Shipped in 1 to 15 days. Molds start at $1,495

Plastic Injection Molding Process

Quoting

Once a 3D CAD model is uploaded to ProtoQuote, you can specify material, quantity, finish, overall expectation of the part in a notes section, and essentially, communicate as much information about that part as possible at the time of upload. The part will be analyzed based on Proto Labs' quick-turn manufacturing process to generate an automated quote. From there, you can call a customer service engineer with questions about our process and how it relates to your part geometry and make any modifications that are needed.

When you’re satisfied with your design and decide to order your part, it moves to the mold designers at Proto Labs, where they develop your 3D CAD in its negative image to digitally design two halves of the mold, or the A-Side and B-Side. The mold designers create the shutoffs and the parting line — which are custom to your geometry — as well as layout of the gate(s) and ejector pins. The mold design is sent back to you for final approval, and when ready, the necessary toolpathing begins to mill your mold.

Mold production

Our designers toolpath the digital mold design to our CNC machines instructing the end mills where to travel on the X, Y and Z planes, so the machine can rapidly mill both sides of the mold out of an aluminum block. Any pickouts, cams or additional mold features that need to be fitted are also created at this time. Your mold is now in a Proto Labs surface finish stage of F0, or as-milled. The mold moves into our build department where a mold operator is assigned to polish your mold at your desired level of finish. Mold polishing is one of the most detailed and manually intensive processes within Proto Labs — one that is almost artistic in nature. All of the ejector pins are cut to length, the A-Side and B-Side are assembled to the press and final fittings are done to ensure the mold will seal properly once resin is injected.
Mold production
plastic injection mold. Protomold milling
Milling
plastic injection molding process. Protomold mold finishing
Mold finishing
plastic injection mold. Protomold milling
Milling
plastic injection molding process. Protomold mold finishing
Mold finishing

Part production

Resin pellets — from either Protomold’s stocked supply, which may also include a 3-percent salt-and-pepper mix of colorant, or supplied by a customer — are loaded into a barrel where they will eventually be melted, compressed and injected into the mold’s runner system. Hot resin is shot into the mold cavity through the gates, the part is molded, and ejector pins facilitate removal of the part from the mold and into a loading bin. The thermoplastic injection-molding processes is a standard process involving an aluminum mold with no heating or cooling lines running through it, which means cycle times are a bit longer. It allows our molders to monitor fill pressure, cosmetic concerns and the basic quality of the parts, so they are ready to ship upon finishing. When the run is complete, parts (or the initial sample run) are boxed and shipped shortly thereafter.
Part production
Protomold resin hopper. Molding Plastic.
Resin hopper
Protomold molding process
Molding process
Protomold resin hopper. Molding Plastic.
Resin hopper
Protomold molding process
Molding process
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