3D Printing Aerospace Parts: Why It’s No Threat to CNC Machining

The dawn of 3D printing came with predictions it would bring about the next Industrial Revolution. This process, otherwise known as additive manufacturing, has indeed brought about massive changes, particularly in aerospace.

Nonetheless, few trending stories cover the limits of 3D printing, which are extensive given the technology is still relatively new.

In this blog, find out why 3D printing has worked so well for the aerospace industry—but why these precise qualities make it difficult to adapt to other industries.

What is Additive Manufacturing?

To start, there’s no real difference between 3D printing and additive manufacturing. Used interchangeably, these terms refer to processes that create objects by adding materials layer by layer.

(Additive manufacturing could be considered the opposite of processes like precision plastic machining, which create objects by removing materials layer by layer.)

In 3D printing, a digital file dictates to the “printer” the precise design in which to shape the material (usually a durable thermoplastic). The result: stunningly complex designs printed in one piece.

Why Does 3D Printing Work So Well in Aerospace?

The key is customization.

3D printing is useful for numerous applications in aerospace because this industry leans on highly custom, costly parts that don’t benefit from economies of scale. Unlike toothbrushes or cups, airplanes are made in much smaller batches using designs that may be unique to each individual unit.

The same is true for the medical industry, which has seen amazing advances thanks to 3D printing. Anyone following the news has seen stories about 3D-printed prosthetics, medical models and even organs. These advances have been made possible by a process that can create parts customized to specific anatomic circumstances.

Why Doesn’t 3D Printing Work So Well in Other Industries?

There are a few reasons other industries have been slower to implement 3D printing in their production processes, and why processes such as CNC machining and plastic injection molding have nothing to fear:

• Economies of scale. As mentioned, the reason additive manufacturing excels in aerospace is it’s well suited for incredible customization—but badly suited for large batches of identical parts. This is because with 3D printing, the thousandth part costs just as much as the first; cost correlates with quantity directly. In contrast, at large scales processes like plastic injection molding see drastic cost savings per unit. In industries that rely upon economies of scale, 3D printing isn’t often viable. 

• Issues with tensile strength. Because 3D-printed parts have been fused together layer by layer, the parts may be surprisingly weak under certain tensions. While this weakness can be countered through smart designs that account for it, certain industries rely upon parts with uniform strength. These industries will continue to lean on precision plastic machining and other manufacturing processes to create the strongest possible custom plastic parts. 

• Parts aren’t smooth. Without costly post-processing, most 3D-printed parts finish with rough layer lines and surface inconsistencies. Post-processing for surface smoothness not only requires labor and harsh chemicals; it can result in lost tolerance. All of this makes 3D printing unviable for certain industries. 

• Advanced specialty plastics may not be an option. When it comes to strength, chemical resistance, lubricity, etc., specialty plastics are unique in their ability to incorporate many superior properties at once. Additive manufacturing can make use of dozens of materials, but it cannot be used (at least, not cost effectively) for some of the most advanced specialty plastics.

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