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Comparing 3D Printing And Injection Molding

Written by RevPart

CNC shop floor with injection molding machine

If you only read general interest manufacturing articles aimed at the layperson, it would be easy to consider 3D printing as the “trendy,” new(er) manufacturing process ready to take over the field, while injection molding might be seen as the stodgy old process that’s been surpassed by new technology. In reality, the benefits, qualities and interactions of these two processes are much more complex.

First and foremost, 3D printing and injection molding don’t, in general, compete against each other in a traditional sense. One will often have an advantage over the other, depending on specific scenarios and project requirements — but you won’t often see a case where the primary benefits of the two overlap. In other words, when you understand the advantages and disadvantages of each process, it’s usually fairly easy to know which one to use, and when.

There are a number of ways — some not so obvious — where the two can complement each other. We’ll look at those below, and will also examine some of the finer details of when to choose one process over the other.

Advantages and Disadvantages of 3D Printing and Injection Molding

Before getting into more detailed information about 3D printing and injection molding, we’ll take a look at some areas in which one will usually offer a clear advantage over the other. While this list provides a good rule of thumb, remember that every manufacturing project is unique, and you should investigate how a particular process will work for your needs.

When to Choose 3D Printing

  • • For prototyping: 3D printing offers clear speed and cost benefits for low-quantity applications such as prototyping. With very little machine setup time and no need for costly mold tool construction, 3D printing has, throughout its several-decade lifespan, revolutionized the ability to create quality one-off prototypes.
  • • When turnaround time is a concern: For most lower-quantity applications, injection molding is time-prohibitive due to the need for a mold to be designed and manufactured. When turnaround time is critical, 3D printing can get parts to you in a matter of days (or even hours), and can remain cost-effective in quantities up to several hundred pieces.
  • • For highly complex parts: The nature of the 3D printing process means that more complex geometries and unique contours can be created without regard for the best practices necessary to follow in injection molding. Of course, for higher production runs, injection molding will likely need to be incorporated at some point, but 3D printing is the more facilitative process for testing the limits of design.

When to Choose Injection Molding

  • • For large quantities: At scale, injection molding is the much more cost- and time-effective choice for production. As more parts are produced, the cost of the mold is spread more evenly. Plus, in extremely high production runs, the speed at which a part can be produced becomes faster than with 3D printing.
  • • For simple geometries: When quantities begin to increase, it’s worth taking a closer look at the value of using 3D printing for parts with simple shapes, few to no irregular features, or any other types of simple geometries that could easily be produced with injection molding.
  • • When material selection is critical: 3D printing is making gains, but the range of plastics and formulations that can be used in injection molding is unparalleled. If a certain type of material or material property is required, it may not be achievable using 3D printing.

How Do 3D Printing and Injection Molding Work in Tandem?

As you’ve seen above, 3D printing and injection molding each have distinctive advantages and disadvantages. Since these most often differ between the two, there are lots of ways in which the two can complement each other by working in tandem. Let’s look at a few:

  • • As part of the overall design and production process: In designing a new part or product from the ground up, both 3D printing and injection molding have an important role in the process. 3D printing is the easiest way to prototype and iterate designs, while injection molding should come into the process for the production run itself (depending on quantity).
  • • For “bridge manufacturing:” For products where you aren’t yet ready to make the full commitment to a high-volume production, 3D printing can be effective as a “bridge” process to test the waters of the market without having to worry about potential inventory and cost issues. Bridge manufacturing is also useful in scenarios where injection resources are unavailable for any reason. In these instances, 3D printing can step in to fill any potential supply gaps.
  • • For 3D printed molds: An interesting synergy can be achieved between 3D printing and injection molding when 3D printing is enlisted to create the mold that will be used in the injection molding process. A 3D printed mold will not be as durable as, for example, a tool steel mold, but can serve as an effective solution for mid-volume production runs that might not, for any number of reasons, clearly call for either 3D printing or injection molding with a tool steel mold.

How Do 3D Printing and Injection Molding Compare From a Cost Perspective?

The short answer? It depends — on a broad number of factors: production quantity, material required, part geometry, turnaround time and more. It also depends on what you’re considering as your cost:

For overall costs, injection molding will almost always be the costlier choice. For cost per part, however, at a certain volume of pieces, the answer changes.

For lower quantities, 3D printing will offer a lower cost per part, since the cost of the mold is factored in and isn’t spread among a higher quantity of parts. As volumes increase, injection molding becomes the more cost-effective solution, as more parts are produced against the one-time cost of the mold.

In general, that point of change occurs at a volume of several hundred parts, usually anywhere between 300 and 500. As always, be sure to factor in the specifics of your project when making your calculations: if turnaround time is at a premium, for example, the math may change. RevPart is ready to answer any further questions you might have about the comparison between 3D printing and injection molding.

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