3D Printing vs Injection Molding; When to Use What?


3D printing had a huge buzz around it a decade ago. The general feeling was that 3D printing would democratize and decentralize manufacturing. The initial hype has since calmed down as people become more educated about what you can and cannot do with 3D printing. 

While 3D printing continues to grow at a steady pace, it still has a few shortcomings. In this guide, we explore some of those shortcomings by comparing 3D printing against traditional manufacturing methods like injection molding.

What are the benefits of 3D printing versus injection molding and will we see 3D printers replace injection molding?

What Are The Benefits Of 3D Printing VS Injection Molding ?

The main benefits of 3D printing over injection molding are the easy adaptability of designs, production flexibility, shorter turnaround times, and a lower barrier to entry. These key characteristics make 3D printing a better alternative for injection molding, particularly for prototyping and short production runs.

What Is 3D Printing?

3D printing or additive manufacturing produces items or parts by bonding layers of plastic together. There are several types of 3D printing technologies of which fused deposition modeling (FDM), stereolithography (SLA), and selective laser sintering (SLS) are the most used. Source

Top 3 Benefits Of 3D Printing

Adaptability

3D printers produce parts in an additive process. This allows you to make changes to and during the process. With a 3D printer, you can pause and make any necessary changes to your item and then resume printing. 

With injection molding, you first follow through on the design and make changes only after the part has been produced.

3D printing is better equipped to handle complex designs and shapes. Complicated designs are more expensive and harder to produce through injection molding.

Production Flexibility

There is faster iteration and more room for error with 3D printing as you can fix mistakes as they arise. Injection-molded parts require a separate mold for each part. This makes iteration slower. Also, an injection mold costs $12,000 on average which gives you less room for mistakes. 

You also don’t need to hold large inventory with 3D printing. You can print as and when you need to due to the faster setup time and ease of printing. 

Lower Barrier To Entry

It is far much easier to start 3D printing than it is injection molding. Not only are 3D printers and materials cheaper, but there is also less technical expertise required. Injection molding has a slower setup and steeper learning curve compared to 3D printing.

When Should You Use 3D Printing?

To sum up, 3D printing is more suited for:

  1. Small production volumes.
  2. Prototyping.
  3. Print-on-demand services.
  4. Low-resolution items.

Is 3D Printing Cheaper Than Molding?

Evaluating the cost of 3D printing versus injection molding depends primarily on the production volume. As a rule, the smaller the number of items printed, the cheaper it is to produce them through 3D printing. It is much cheaper to use injection molding for larger production volumes of 100 or more.

Injection molding has an initial cost and a cost per unit. The initial cost typically includes the cost of materials and the cost of producing the mold. Once the initial cost is out of the way the cost-per-unit diminishes due to economies of scale. The more you produce, the cheaper it gets.

There are no economies of scale with 3D printing. The cost-per-unit remains the same regardless of how many items you print. This means, the more you print, the more expensive it gets. This is why it’s cheaper to produce larger volumes with injection molding. 

Will 3D Printing Replace Injection Molding?

3D printing has several inherent flaws that make it unsuitable as a replacement for injection molding. The major flaws of 3D printing are it cannot produce large volumes of items, its weaker part strength, and of course cost. 

What Is Injection Molding?

Injection molding is a subtractive manufacturing process. A solid block of material is machined to produce a mold. The mold is used to produce multiple copies of an item. 

Top 3 Benefits Of Injection Molding

Large Production Volumes

Injection molding is better suited for large production volumes. 3D printing is faster at producing and iterating prototypes or small production volumes. When it comes to larger production volumes of more than ten items, injection molding is more efficient.

With subtractive manufacturing, you can produce thousands of items in an hour. 3D printing cannot achieve anywhere near that same type of speed as a single item can take up to 8 hours to build! Injection molding is faster at scale than 3D printing. 

Production Value

3D printing produces items via layer bonding. Injection molding produces items via a cast from a solid block of material. Layer bonding has its advantages but it cannot produce parts as strong as injection molding does.

Layer bonding also leaves visible layer lines on the finished item that needs to be processed. Injection molding produces parts with a much better surface finish without the added labor and effort of post-processing.

There are fewer variable results with injection molding. Once the mold is made, all the units made from that mold should be exactly alike. 3D printing is slightly more complex so you are likely to see larger variations between items.

Cost

3D printers and the materials they use are cheaper. However, material costs only apply to printing in small batches. The cost of 3D printing quickly becomes unsustainable as you print more. In contrast, producing larger volumes gets cheaper with every unit via injection molding.

When Should You Use Injection Molding?

In summary, injection molding is more suited when:

  1. A better finish is required. 
  2. Producing items in large volumes.
  3. Maintaining an inventory of items is necessary.

Can You Injection Mold With A 3D Printer?

3D printers can be used to print molds that can be used in injection molding. The advantage of this is that it reduces the biggest cost of injection molding, which is fabricating the mold.

Combining 3D printing and injection molding achieves higher cost and production efficiencies compared to using either of the technologies alone.

3D printing and injection molding complement each other. Casting molds with 3D printers is much cheaper and provides quicker iteration. Injection molding produces better parts at scale. By using both technologies you maximize the strengths and minimize the weaknesses of each.

sherifjallad

I am a very well experienced techie civil engineer who's extensively interested in 3D printing technology and even more captivated by the potential of 3D printing livable structures

Recent Posts