For Production AM, Is Metal a Better Candidate Than Polymer?

Is additive manufacturing a more ready and successful solution for metal part production than it is for plastic part production?

The answer is subject to change as AM technologies and their applications continue to advance.

But the answer today is likely yes, and that answer is counterintuitive. 3D printing of plastics has been with us longer and ought to have a head start. But 3D printing might be better suited to answering production needs and winning production applications when metal is the material.

To be sure, there is no way to know this for certain. There is no practical way to conduct a census of AM production applications. However, I have been involved for years in what could be seen as a meaningful survey of AM end-use part applications. We recently celebrated the 5-year birthday of The Cool Parts Show, the video series I co-host with Stephanie Hendrixson about parts and products made via AM. Nearly all the 78 (and counting) regular episodes of this show have been about some distinct and separate end-use application of AM. And as part of a YouTube livestream honoring the show’s anniversary, I took stock of all we had done, including noting the breakdown of “cool parts” by material. I might have expected polymer to dominate this list.

But no. Just over 50% of the applications we have found, applications fully realized enough that we could show the part and develop an episode around it, were in metal. All other materials — polymer, ceramic and composite (including one metal matrix composite) — together account for under 50%.

I might have expected more polymer successes because polymer is the easy entry point for AM. Desktop 3D printers can make production components. Meanwhile, larger and faster industrial polymer AM machines offer production solutions competing against molding at increasingly larger quantities.

But in preparation for that same livestream, I had a conversation that highlighted some of the special challenges of plastic part production. Spencer Loveless has appeared on the show — his company Merit3D provides production services in plastic via digital light processing AM; I called to get an update. One notable job has been a million-piece order for 3D printed parts. Yet Loveless freely admits the success rate at providing an effective solution to plastic part production opportunities is low. In part this is because the denominator is high — he hears from a lot of companies interested in AM. But it’s also due to the state of AM’s limitations. When a polymer job is not right for additive, he says, the reason is generally cost per part or material properties. And as I consider these reasons, I think it becomes easier to see why metal might offer the more natural way forward for AM into production.

Taking them in turn:

1. Cost. True, mold tooling for plastics is costly. AM often succeeds where a manufacturer is not ready for this investment or cannot wait for the mold. Still, the cheapest plastics production process is one in which the mold tool is on-hand and already paid for, and AM has little chance if this is the case. By contrast, metal is inherently more costly to work with even in an established process. Machining, forging, casting — all are high-wear or high-energy processes. AM is nearer to success in metal because the competing cost per part is already higher.

2. Material properties. Manufacturers relying on plastic have grown accustomed to getting (a bit of an exaggeration, but not much) exactly the mix of properties they want. Polymer engineers are chemists realizing a greater range of material freedom than the metallurgists who innovate alloys. In both material types, the range of possibility is greater in established manufacturing processes. But in metal, additive can deliver a larger percentage of the performance combinations manufacturers expect.

There is even more to say about why metal might offer the better AM production case. For example, assembly consolidation is a bigger win when metal parts are involved.

But more importantly, there is more to be written. Any AM cost or material limitation today is a fleeting barrier, because the processes are improving and their material envelopes are growing. We might be in a moment or season for success with metal in production AM. The moment or season for greater successes with polymer might be what comes next.

In fact, maybe we will discover as much whenever we next celebrate a milestone for our show and tabulate AM’s successes at that time. If that is to be the case, you can contribute to the tally. Tell us about your AM success in polymer, metal, composite or any material at coolparts@additivemanufacturing.media.