SoloPoint Insights

Should You Go With Injection Molding or 3D Printing?

Injection Molding and 3D Printing are the two most popular processes for prototyping. But how to know which one is better for the product you’re designing? — This is a common question for Mechanical Engineers and Designers.

This article from Creative Mechanism, a Pennsylvania-based engineering firm specializing in prototyping for the consumer market, details out the difference between each processes and how to select one that would be a good fit for any project:

3D printing and injection molding aren’t really competing technologies so much as they are complimentary. Both can theoretically be used for manufacturing and both can technically be used for rapid prototype generation. Although the trend for additive manufacturing processes (different types of 3D printing) is growing, most serious manufacturing is done with injection molding equipment while in most cases the 3D printer is a much more effective tool for rapid prototype development.

So what’s the difference between injection molding and 3D printing?
The two processes are entirely different. In injection molding you are melting a molten material and injecting it into a large pre-designed cavity inside a steel tool (think of a steel box with an internal shape that matches the skeleton of your part). Injection molding machines are designed to keep the plastic melted while en route to the tool cavity and then to rapidly cool it once injected so that another round (cycle) can be accomplished.

There are different types of 3D printing, however, the most common type, Fused Deposition Modeling (FDM) also works by melting plastic. The difference between FDM and injection molding is that the molten plastic in an FDM machine is added one drop at a time in succession. The FDM machine follows inputs from a computer design file and essentially “prints” the part layer upon layer.

What about time?
As you might imagine, the printing process for a single part takes significantly longer than a single injection molding cycle. A complex 3D printed part might take several hours to print where an injection molding cycle can be reduced to several seconds depending on the complexity of the part.

What about cost?
The tradeoff with injection molding is that an entry level injection molded part is going to be significantly more expensive to produce than it would be in a 3D printer. When developing a product you first need to design the prototype part itself. This is the first and last step in 3D printing. After you have the prototype design you essentially just press “print” and out comes your part a several minutes to hours later depending on complexity. In injection molding that is just the first step. The next step is designing an injection mold tool (typically out of aluminum or steel). This is much more expensive. After that you need to order the actual injection molding cycle.

Here’s a chart to better determine the right process for your prototyping needs:

 Low Cost

(1-10 Parts)

 3D PRINTING

If you need 1-10 parts and/or rapid design iterations on your prototype part then 3D printing is the place to be. Injection molding requires expensive mold tools with high cost internal cavity designs that don’t make sense unless you need to do consumer research or quality control testing prior to major production.

Low Cost

(100+ Parts)

INJECTION MOLDING

Once you start manufacturing in volume then it makes sense both in terms of time and money to use injection molding. Oftentimes you can utilize Maser Unit Dye (MUD) inserts to reduce costs during prototype development.

High Quality

INJECTION MOLDING

3D printed prototypes are not typically finished parts. Most FDM machines utilize either ABS or PLA plastic which is more often than not a different product than the final manufactured part will be made from. In addition, Injection molded parts are less likely to delaminate in general because they are a homogeneous material that cures as a single part vice being constructed through additive manufacturing one drop at a time.

Low Time

(1-10 Parts)

3D PRINTING

3D printing is fast and extremely convenient. There is really no comparison when you’re trying to design a part from scratch. With an integrated software/hardware package you can go from CAD design to the FDM machine in seconds.

Low Time

(100+ Parts)

INJECTION MOLDING

Although 3D printing is much more rapid when considering low production volumes, it is likely more convenient to use injection molding when producing en masse. Large volume prototype production would be more easily accomplished through injection molding once you have developed a single well-designed prototype via 3D printer that you can use to design an injection mold tool.

Are you looking for an engineering talent that can design your company’s next big product? Contact the experts at SoloPoint Solutions. We have a broad range of mechanical engineers with diverse backgrounds and expertise that could fulfill your product’s vision to completion.

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