3D Printing Alternatives: Rapid Injection Molding and CNC Machining

| Updated on March 26, 2024

3D printing has dominated the discussion around speedy, affordable manufacturing methods for some time now. 

And yet, this dominance has come at the expense of competing processes, meaning that many businesses don’t explore all the options when developing products.

To clear things up, here is an overview of two other approaches you can take, in the form of rapid injection molding and CNC machining, covering what they are, where they make sense to use, and how to choose between them.

What is Rapid Injection Molding?

To explain in simple words, Injection Molding is a fast-paced, cost-effective process used in manufacturing to produce intricate plastic parts and components. 

It’s a technique that leverages automated machines and injection molding tools for the quick creation of prototype models or final products.

The crux of the process involves injecting molten material, typically thermoplastic polymers, into predefined molds under high pressure. This method unfolds swiftly, hence the term ‘rapid’, enabling manufacturers to produce high-quality components in relatively short time frames.

The versatility of rapid injection molding makes it an ideal solution across various industries like automotive, healthcare, and consumer electronics. 

For example, car manufacturers frequently use this method to create mundane components such as cupholders, as well as technical parts like electrical connectors.

Pros and Cons of Injection Molding

This process comes with a set of advantages that makes it favorable within the manufacturing sector, just as 3D printing has its perks

These include:

  • Rapid injection produces parts at lightning speed, finishing the work in a minute. It works at such an unbeatable speed and pumps out the components in large amounts.
Injection molding stats image

The above graph shows the growth report of the Injection molding market in the US in the future.

  • It reduces the spent on labor and increases production rates because of the use of automation. 
  • Moreover, it can produce difficult geometries and make sure the end product is precise.  

Yet like any other technique, this too has its disadvantages:

  • It can be quite costly to plant this because the tools of designing and creating are expensive and could take a toll on your finances. 
  • It becomes necessary to work at a large scale, or else there won’t be any chances of economical production. 

What is CNC Machining?

CNC (Computer Numerical Control) machining is another popular manufacturing method, highly revered for its precision and versatility. It involves the automated control of production tools using a programmable computer.

In essence, a digital template instructs the machine tool’s movements, enabling it to sculpt materials into desired shapes with exceptional accuracy. 

These machines can perform intricate cutting tasks along three different axes simultaneously, which allows complex parts to be made all in one go.

From metals like steel and aluminum to woods and plastics, CNC machining accommodates a wide range of materials, making it ideal for various industries such as automotive, aerospace, or electronics. For instance, it’s regularly used in medical device production where strict tolerances are vital.

Did You Know?
NASA successfully tested 3D printing in the zero gravity of space, printing a ratchet wrench on the ISS.

The Benefits and Drawbacks of CNC Machining

As you no doubt have suspected, computerized machines bring plenty to the table in terms of benefits, and just a few of these are:

  • Flexibility: It can create highly complex parts with ease because it is programmable, making it more flexible than other processes.
  • High Accuracy: CNC machine precision eliminates human error, capable of producing identical items with utmost consistency.
Injection molding stats image

The above statistics show the expected market size of the CNC machine market in the future.

  • Broad Material Use: As mentioned, it can handle a variety of materials from metals like steel or aluminum to softer ones, say wood or plastic.

    But unfortunately, it’s not without its downsides:

  • Cost-Prohibitive for Small Quantities: It requires significant setup time, which might not be cost-effective for small batches.
  • Limited Geometric Complexity: Although advanced, certain geometric shapes may challenge even sophisticated multi-axis machines.

Choosing the Best 3D Printing Alternative

When it comes to selecting a 3D printing alternative between rapid injection molding and CNC machining, there are several elements you need to consider that can affect your final decision:

  • Production Volume: For large quantities, rapid injection molding’s speed and efficiency shine, especially if you’re eager to automate manufacturing as much as possible. Meanwhile, if precision trumps volume, Computer Numerical Control might be more fitting.
  • Initial Investment: If budget isn’t an issue, the upfront costs of molds or the setup of automated gear won’t deter you from using either process.
  • Design Complexity: Whilst both methods create intricate designs, some complexities may favor one over the other. For instance, undercuts can be tricky for CNC but feasible in shaping.
  • Material Options: Again, both cover a wide range, but the versatility that exists with this method trumps injection molding.

Of course, these factors aren’t standalone, but rather they interact with one another, so each case demands bespoke evaluation. Neither method is inherently superior but dependent upon project parameters. 

So if you seek fast high-volume production or require complex small runs prioritizing precision, you have to pick a route based on your needs.

Final Thoughts

Injection molding and CNC machining image

Alt-tag: Injection molding and CNC machining image

It’s a good idea to evaluate and experiment with several forms of producing, from 3D printing to rapid injection molding and CNC machining, if you have the opportunity. 

Even the simple act of examining parts and products produced by other brands using them will give you more insight to drive your own choices.

Janvi Panthri

Senior Writer, Editor

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