Manufacturing parts has traditionally been accomplished with injection molding. This process involves injecting molten material into a metal mold; once cooled, the now solid object is ejected as a solid part. However, with advances in 3D printing and additive manufacturing technologies, this newer manufacturing method can offer some advantages over injection molding.
Injection molding is more typically used as a method for producing high volumes of the same object. Once a mold is created, injecting the molten plastic can be done over and over again to produce the same, exact result. When attempting to produce a low volume of parts, costs go up and the overall practicality of using injection molding is reduced.
3D printing has suffered in its capacity to produce high-volume runs in the past, being used more for prototypes and one-offs, but as new technologies like the Multi Jet Fusion (MJF) printer have emerged, this is changing. MJF technology allows high-volume production because of volumetric optimization (the ability to print along the x, y, and z axes). 3D printing is also excellent for smaller volumes of production because costs don’t change with the volume of parts as they do with injection molding; each part can generally be produced for the same price.
The cost of injection molding can fluctuate depending on how many units are produced. A large upfront investment is required when making the mold. Molds can be reused for thousands of parts, but the initial cost of producing a mold can be anywhere from few thousand to tens of thousands of dollars. Factors that alter the cost of the mold include the size of the mold and quality of the metal used to create it, which can also affect the life of the mold and amount of producible parts. Once the mold is created, though, the overall price of injection molding is spread out over the number of parts produced, as the actual production labor and plastics are inexpensive.
3D printing, on the other hand, has no initial cost for a mold, because there is no mold. The process uses a digital file, which can easily be altered in an appropriate computer program. If a design changes or needs to be altered, this is a simple process, whereas in injection molding, costly modifications or an entirely new mold would need to be produced.
However, the tradeoff comes in the form of more expensive production and post-processing for 3D printing. Once again, though, this is being changed by MJF technology, as it allows for high volume production at a reduced price point (up to half the price of other additive manufacturing methods).
Timing and speed of production can vary for injection molding. Producing a prototype, developing a mold, and other pre-production processes can take a lot of time, whereas once the actual injection molding occurs, the process can move fairly quickly. Allowing time for post-processing also comes into play, as large parts may need to be broken into components for production and assembled later, and tooling might be required.
With 3D printing, once a design is created, the timing required for production is only however long it takes to print the object, plus additional time if post-processing is necessary. The more complex the parts are and the higher the volume of parts per print, the longer the print will take. MJF is helping to reduce printing time, as it produces parts as much as ten times faster than other print processes. Post-processing time will also increase with the complexity of the needed finish and also the complexity of the design itself, as it can be difficult to alter highly detailed parts without ruining the part. As post-processing becomes more optimized, the timing for this process, too, will be reduced.
The complexity of the end product must also be considered when choosing between these two manufacturing methods. In injection molding, the complexity of the final product can affect that initial mold price, causing an increase to your overall costs. Additionally, some shapes and designs might be extremely costly to create using injection molding, or even impossible.
3D printing is capable of producing these otherwise impossible designs because of its unique quality as an additive manufacturing process. MJF technology in particular is able to create intricate detail, lattice structures, and parts within parts because of its use of plastic powder in its manufacturing process.
Regardless of what type of production your design requires, our experts here at ProtoCAM are prepared to help you determine the best methods to produce your unique part!