Injection Moulding vs 3D Printing

Injection moulding and 3D printing are both methods used to produce plastic components. 3D printing has become more widely used over recent years and it can be difficult to know which manufacturing method best suits your needs. Here we will explore each process, their advantages and disadvantages, and how they can complement each other.

Injection Moulding

In the injection moulding process, molten plastic is injected into a pre-made mould in an injection moulding machine, using high temperatures, force and pressure. Once the mould has been filled and the part is formed, it is released from the mould, cooled, and then trimmed/finished as required.

Injection moulding allows for high volumes of parts to be produced. Automation and multi cavity tooling are manufacturing options that can support mass production.

Advantages

• High volume production.
• Lower price per part on medium to high volume production runs.
• Consistent quality across the full production run.
• A huge range of material options.

Disadvantages

• Higher initial tooling and set up costs.
• Longer lead times for tooling manufacture.
• Fixed designs – once tooling is complete it can be costly to change, in both price and time.
• Higher price per part on low volume production runs

3D Printing

3D printing, also known as additive manufacturing, is a process where 3 dimensional objects are created from a digital file. Successive layers of material are built up on top of each other until the object is complete.

A number of materials are available for 3D printing, including but not exclusively, TPU, TPE, Nylon, Polypropylene, and Polycarbonate. For more complex prints, materials such as PVA or HIPS are used as a dissolvable support structure that is removed once the print is complete.

 Although a slower overall process, 3D printing has a faster initial set up time and can be a more suitable option for more complex parts, allowing for frequent changes to design.  Ideally suited to low volume production, 3D printing enables samples and prototypes to be made before committing to full tooling and production.

Advantages

• As parts are made by building individual layers, 3D printing is ideal for complex and intricate designs.
• 3D printing software enables parts to be printed from digital files, meaning changes to design can be done quickly and conveniently.
• Low set up costs in comparison to injection moulding, with no requirement for upfront tooling. The printers themselves, the materials and the accompanying software programs are lower in cost and more accessible than injection moulding equipment.
• Ideal for prototyping and sampling before approval. You can see your part come to life in a quicker lead time and before the commitment of tooling and complete production runs.

Disadvantages

• Limitations on size. Part dimensions are dictated by the print area of the 3D printing machine. Whilst injection moulding can have limits on size depending on specific machines, in general larger components can be produced through injection moulding.
• Although the initial set-up is faster than that of injection moulding, the 3D printing process itself can be a slow one, with many 3D printers only able to build one or two parts at any one time, making it more suited to low volume production requirements..
• Due to the nature of layer building, the surface finish of 3D printed parts is rougher than that of injection moulded parts.

Summary

3D printing and injection moulding are often seen as alternatives to each other, but they both have their place within the manufacturing industry, offering different benefits.

Due to its excellent versatility and huge material choice, the vast majority of plastic parts are still produced by injection moulding.

However, 3D printing has become an increasingly popular choice for prototyping, especially as injection moulding can involve significant upfront tooling costs, and a commitment to components that may need testing and/or modifying prior to approval.

Whilst it is highly unlikely that either process will take over from the other, alongside each other, injection moulding and 3D printing, can offer the ideal balance of manufacturing versatility and cost/time optimisation.

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