In the age of rapid technological advancement, the manufacturing process that seems to have garnered the most media attention in recent years is 3D printing. From its ability to recreate both ordinary and unique objects, to its potential to produce complex parts and pieces – and even a few controversies – 3D printing has dominated numerous headlines, as well as the public’s imagination.

With such success, it may seem that 3D printing and its state-of-the-art technology are set to replace more traditional manufacturing methods, such as injection molding. But in reality, these two processes are rarely considered competitors and in some cases even complement one another, as each is suited to specific and unique applications.

This post will examine 3D printing and injection molding – the unique advantages of each method, as well as some key ways in which they differ. Let’s start by taking a look at both the benefits and limitations of 3D printing and injection molding.

Injection Molding

Advantages

When manufacturing large quantities, injection molding has the advantage as a more cost-effective process. The economics of injection molding dictate that the greater the number of parts produced, the more the cost is spread out over production. For high production runs, parts can also be manufactured much more quickly through injection molding than 3D printing.

While 3D printing is gradually expanding the range of materials it supports, its compatibility is still significantly limited in comparison to injection molding. Injection molding currently has an edge regarding the wide variety of plastics and resins that are compatible with the process.

Cost is another potential benefit of injection molding over 3D printing. The creation of a mold requires a significant initial investment. But once the mold is built, it can be reused for thousands of parts.

Limitations

Design is a key limitation of injection molding. While many complex forms can be created through injection molding, 3D printing has the ability to create some very unique geometry that is difficult or impossible to create through more traditional manufacturing methods.

Complexity is also a key consideration for manufacturers choosing between injection molding and 3D printing — the more detailed and complex the final part, the costlier the mold. As a process utilizing digital design and files, 3D printing does not share these same limitations.

3D Printing

Advantages

Where injection molding is limited, 3D printing offers a viable alternative for some applications. Some of the previously mentioned difficulties for injection molding can easily be achieved via 3D printing. The ability to design in CAD and produce parts and pieces with complex geometries through additive manufacturing and plastic powder is a significant benefit for manufacturers.

With 3D printing, there is also no mold cost as the process does not utilize a mold. Thanks to the use of digital files, revising or editing a design also carries little to no cost beyond that of the engineer’s time. By contrast, an error or modification in the injection molding process might require investment in engineering changes, an additional sunk cost.

Limitations

Production time can be considered a disadvantage of 3D printing, as the amount of time required per part is significantly more than that of injection molding, making it more practical for smaller production runs such as rapid prototyping.

The sheer number of materials available for injection molding also make it a more suitable manufacturing method for many applications.

While manufacturers may save on the long-term costs of molds and design modifications, the barrier to entry in terms of cost for 3D printing is currently significant. As 3D printing technology improves and evolves, the cost of 3D printers is coming down and more options are available in the market. But manufacturers should still be prepared to make a significant investment when purchasing a 3D printer capable of commercial production.

Quick Reference Guide: Practical Applications

Typically, manufacturers should choose 3D printing when:

  • Creating prototypes, especially in rapid prototyping
  • Time is of the essence and parts are needed in days or even hours

Opt for injection molding when:

  • There is significant volume – injection molding is more cost-effective and efficient for large quantitiesP
  • The material is key – injection molding offers manufacturers a range of options when it comes to plastics and resins

The Road Ahead

Few would argue the impact 3D printing has had within the manufacturing world. As 3D printing technology continues to evolve, the process is sure to become even more accessible and practical for a variety of industries and applications.

Meanwhile, plastic injection molding remains – as it has for more than a century – a reliable and trusted process for producing large quantities of parts and pieces.

Considering economies of scale, the relative newness and some key limitations of 3D printing, in most commercial and high production scenarios, 3D printing serves as a valuable complement to plastic injection molding, rather than a peer or competitor. But today’s manufacturers are fortunate to have access to the benefits of both of these manufacturing processes in order to choose the solution best suited for their specific needs