Plastic Injection Moulding

Our plastic injection moulding process produces custom - rapid prototypes and end-use production parts in 15 days or less. We use aluminium moulds that offer cost-efficient tooling and accelerated manufacturing cycles, and stock more than 100 different thermoplastic resins.

Plastic Injection Moulding Design Guidelines will help you understand capabilities and limitations.

​We have two injection moulding service optionsprototyping and on-demand manufacturing—with each offering their own benefits depending on your project needs. If part quantities are higher, an affordable piece-part price is important and quick-turn production throughout the product life cycle is critical. For this our on-demand manufacturing option is ideal.

Why Choose Plastic Injection Moulding For Your Project?

Protolabs utilise a rapid injection moulding a technology-driven process that leverages manufacturing automation. CAD models are sent directly to the production floor where mould milling begins, but in most cases, moulds are fabricated from aluminium, not steel. This allows for faster and most cost-effective tooling when compared to traditional steel moulds. We offer a number of additional secondary services to support your project.


What is Injection Moulding?

Plastic injection moulding is the process of melting plastic pellets (thermosetting/ thermoplastic polymers) that once malleable enough, are injected at pressure into a mould cavity, which fills and solidifies to produce the final product.


How Does Plastic Injection Moulding Work?

The thermoplastic injection moulding process at Protolabs is a standard process involving an aluminium mould. Aluminium transfers heat much more efficiently than steel, so does not require cooling channels - which means the time we save on cooling can be applied to monitoring fill pressure, cosmetic concerns and producing a quality part. 

Resin pellets are loaded into a barrel where they will eventually be melted, compressed, and injected into the mould’s runner system. Hot resin is shot into the mould cavity through the gates and the part is moulded. Ejector pins facilitate removal of the part from the mould where it falls into a loading bin. When the run is complete, parts (or the initial sample run) are boxed and shipped shortly thereafter. Request your Free Design Cube which shows surface finishes and thick and thin finishes.

Protolabs Supplied Inserts 

We can supply threaded brass part inserts when specified for IM production. For our customers, it means that there is no need for additional purchasing, liaising with suppliers and arranging for the requisite number of inserts to be delivered. It eliminates the risk of delay from other suppliers. Moreover, if additional inserts are required in the event of quality failure or scrappage, that too will be taken care of by us.

Ultimately, our aim is to offer a simple and efficient supplied insert service to complete your IM order. Supplying from our own comprehensive, in-house stock means that you can focus on your project.

IM icon Logo
  • 25 to 10,000+
  • Shipped in 15 working days or less
Common Applications
  • low-volume production
  • bridge tooling
  • pilot runs
  • functional prototyping

Plastic Injection Moulding

Read our latest blog: IM advantages and disadvantages

Injection moulding has a number of advantages. But like any manufacturing process it does have some disadvantages and if these prove important then you may be better exploring alternative technologies such as 3D printing or CNC machining.

Here we will take you through the main advantages and explore when it may be better for you to consider another option.



Watch: Injection Moulding

Rapid injection moulding works best for on-demand production, bridge tooling, pilot runs, and functional prototyping. Our affordable aluminium moulds and quick turnaround times help reduce design risks and limit overall production costs.


Three Types of Moulding 

Manufacturing has experienced radical change over the years, but one of the few constants has been the prevalence of injection moulding as the most common process within the sector. But what makes injection moulding so compelling to design engineers around the world?

Design Guidelines: Plastic Injection Moulding   



Size 480mm x 980mm
Volume 966,837 mm³

101mm from parting line with 3° of draft

Up to 280mm of the part

Projected Mould Area 112903 mm2

Protolabs can maintain a machining tolerance of +/- 0.05mm. Depending on the material selected the resin tolerance can be as accurate as 0.002mm/mm. The resin tolerances of all thermoplastic materials are now visible on your quotes.

If your part is outside of these listed tolerances, please contact us direct to discuss how we can help  [email protected]

  • ABS
  • ABS/PC
  • Acetal
  • Acetal Copolymer
  • Acetal Homopolymer
  • HDPE
  • LDPE
  • Nylon 6
  • Nylon 66
  • PBT
  • PC
  • PEEK
  • PEI
  • PMMA
  • Polypropylene
  • PS
  • PPS
  • TPC-ET
  • TPE
  • TPU
  • TPV


PM-F0 non-cosmetic, default


low-cosmetic, most toolmarks removed
SPI-C1 600 grit stone,
PM-T1 SPI-C1 + light bead blast
PM-T2 SPI-C1 + medium bead blast
SPI-B1 600 grit paper
SPI-A2 grade #2 diamond buff

For more information read our design tip on surface finishes  or contact your dedicated Account Manager. 


Read our design tip on Draft

Maximum Side Core Dimensions



450mm < 150mm < 200mm

Read our design tip on Undercuts




1.143mm - 3.556mm


0.762mm - 3.048mm

Acrylic 0.635mm - 12.7mm
Liquid Crystal Polymer 0.762mm - 3.048mm
Long-Fiber Reinforced Plastics 1.905m - 25.4mm
Nylon 0.762mm - 2.921mm
Polycarbonate 1.016mm - 3.81mm
Polyester 0.635mm - 3.175mm
Polyethylene 0.762mm - 5.08mm
Polyphenylene Sulfide 0.508mm - 4.572mm
Polypropylene 0.635mm - 3.81mm
Polystynene 0.889mm - 3.81mm
Polyurethane 2.032mm - 19.05mm

 * The table is adapted from

Some edges of parts have a radius instead of a sharp edge because we use an automated CNC milling process to create the mold for your parts. This usually does not require any changes to your design, but the resulting radii are identified before the shape is milled.

How can I reduce mould costs?

1. Eliminate undercuts
2. Get rid of unnecessary features
3. Use a core cavity approach
4. Reduce cosmetic finishes and appearances
5. Design self-mating parts
6. Modify and reuse moulds
7. Pay attention to DFM analysis
8. Use a multi-cavity or family mould
9. Consider part size


Learn More about Reducing Mould Costs

What can Injection Moulding be used for?

Injection Moulding is used to make a variety of widely used products. If you look around your desk/ home you will find a multitude of injection moulded products, from bottle tops, remote control casing, console covers, syringes and most plastic made products.

To see an example of an injection moulded part worked on by Protolabs, please view our Hager case study here.

To show off some of the features our injection moulding service can offer, please click to register for your free design cube



Injection Moulding Quote: ProtoQuote with Design Analysis 

Product designers and engineers can upload a 3D CAD model online at any time to receive an interactive ProtoQuote® with free design for manufacturability (DFM) analysis and real-time pricing information within hours. The DFM analysis helps eliminate potential problems like sink, challenging undercuts or walls that are too thin or thick. Once a part design is ready and a quote approved, production begins almost immediately. Upload a part today for a ProtoQuote with design analysis.

Plastic Injection Moulding through hole
Left shows a through hole. Right, is a pass-through core.

Moulding Tips 

Needing to solve difficult tooling and design issues? Shut-offs are a design element that help engineers solve this. Read more about incorporating shut-offs into your mould design.

Further Information

For more information on injection moulding, please check out our White Papers and comprehensive library of design tips

Need support in choosing materials for your project? See our whitepaper on thermoplastics Materials Matter

For tips and advice on designing for injection moulding. See our whitepapers Designing for Mouldability: Fundamental Elements and Design for Mouldability: Complex Features

and for further support with cosmetic appearance of moulded parts. See our whitepaper on Cosmetics

We also have design compilations for injection moulding and the initial design process.

Press operator examines liquid silicone rubber part

Free mouldability analysis within hours