Plastometrex CTO discusses PIP testing, adoption, and reliability in metal 3D printing.
When you work in additive manufacturing (AM), your biggest competitor is often inertia.
As a technology, 3D printing found easy purchase in prototyping because its capacity for enabling rapid iteration fit perfectly with the trial-and-error nature of the process. Manufacturing, in contrast, tends to be much less experimental and much more conservative. As a result, even when AM can offer tangible benefits over more conventional manufacturing technologies—greater design freedom, reduced tooling costs, shorter supply chains—those benefits may not be enough in the mind of the average manufacturing engineer to justify switching from a technology that has been “good enough” for decades. But this isn’t a challenge that’s unique to AM: most novel technologies have to overcome industry inertia in order to succeed.
“You can have great confidence in the technology but you still need people to come on the journey with you,” says Jimmy Campbell, CTO and co-founder of Plastometrex, which makes equipment for the non-destructive mechanical testing of metals. The company is built out of work Campbell did as a PhD student at the University of Cambridge, where he developed an indentation method to measure the yield strength and tensile strength of metals dubbed the profilometry-based indentation plastometry (PIP) test.
Plastometrex and PIP testing
The PIP test begins like a standard hardness test, creating an indent in the metal under a specified load and then measuring the resulting surface profile. Where it differs is in the background, with a finite element model simulating the same test in virtual space. “Within that model, we can prescribe material properties,” Campbell explains. “Yield strength is a direct input along with the material’s work hardening behavior, and the combination of those gives you tensile strength.”
Running locally on Plastometrex hardware, the model iteratively adjusts the material properties in the simulation until its shape matches the experimental measurements. “Once that is sufficiently close—and, realistically, ‘sufficiently close’ means they’re almost indistinguishable—then you’ve reached the tolerance to accept the result, and therefore the properties that correspond to the model shape are the properties of the material,” says Campbell.
This underlying technology has been productized in the form of lab-based machines, as well as field units that Plastometrex initially developed for the oil and gas industry. The latter units are designed to enable users to confirm the grade of steel in their pipelines without the need to remove samples to send to a lab for testing. Campbell says both units have also been seeing more interest from manufacturing and defense, particularly for AM parts.
“I think around 50 percent of our customers are in additive and/or defense,” Campbell says. “They’re being used for many different types of applications, ranging from material development at the early stages all the way to quality control at the point of need in manufacturing, where you can’t print test coupons and send them to the lab.”
Adoption and inertia
Plastometrex claims PIP testing is faster and less costly than tensile testing while also providing more information—specifically, stress-strain curves—than hardness testing. But even if PIP testing offers the best of both worlds, how likely is it that engineers—a skeptical and conservative bunch when it comes to new tech—will buy into it? Campbell acknowledges this challenge with adoption, but part of Plastometrex’s solution is a common one among novel technology vendors: “Adoption, as always, tends to start with the innovators, people who are open to new technologies, so we’ve partnered with companies with that kind of mindset. Nikon is one of them and Renishaw is another where they effectively took the leap with us.”
The other, more concrete approach to overcoming skepticism about a new technology is standardization. This is where Plastometrex and Nikon worked particularly well together, with the latter contributing its own study on comparing tensile testing with PIP testing for 3D printed metals. In addition to Nikon and Plastometrex, Airbus, Renishaw, and the National Physical Laboratory (NPL) collaborated on validating PIP testing and formalizing ASTM E3499-25, establishing PIP testing as an internationally recognized and audit-ready alternative to standard tensile testing.
“Getting the buy-in from the committee is always a bit of a chicken-and-egg problem,” Campbell says. “You need some commercial uptake of the method for the standards bodies to agree that the work needs to be done, but a lot of customers are hesitant to buy a product until there’s a standard associated with it.” This is why Plastometrex started with the lab-based unit, focusing on customers in academia and R&D who are, by nature, less constrained by standardization.
Reliability in metal additive manufacturing
There’s a reason half of Plastometrex’s customers are in AM. Actually, there’s probably more than one. To start, there’s the inertia issue: if you’re seeking innovators as your early adopters, the AM industry is a good place to look. Beyond that, however, is the more practical issue that’s been plaguing metal 3D printing for years: variability. The nature of metal AM entails that machines have dozens if not hundreds of parameters to consider when 3D printing a part. Combine that with environmental variability and inconsistencies in feedstocks and you’ve got a recipe for a process beset with reliability issues.
“I would agree,” says Campbell, “but there are plenty of people in the world who are working on this and trying to reduce variability. Still, I was quite surprised at the variation you can see even when you’re following best practices. Whether it’s powder bed fusion or DED [directed energy deposition], we’ve seen some cases with 15 or almost 20 percent variability in properties.”
The need to confirm the material properties of metal AM parts and the ability to do PIP testing on multiple regions of a part make these two technologies a natural fit. “I believe we’re seeing variability that wouldn’t have been picked up previously,” Campbell adds.
The need to ensure the quality of metal AM parts is being made all the more pressing by the growth of AM in defense. When replacement parts are being produced to supplement brittle or broken supply chains or even at the point of need in defense applications, the stakes are simply too high to depend on an unreliable process. Unfortunately, by the same token, it’s not possible to depend on slower, conventional manufacturing processes either.
The solution, according to Campbell, is PIP testing. Plastometrex recently completed a case study with the British Army and Meltio involving a 3D printed replacement Land Rover brake pedal. “You could do a hardness test for something like that and do some conversion to get the approximate value of tensile strength,” he explains, “but what you couldn’t do is get the yield strength, and that’s one of the crucial parameters.”
In fact, Plastometrex testing showed that the new brake pedal exhibited a small increase in yield value as well as a large increase in tensile strength. “If you just did hardness,” Campbell says, “the best you could say is that the material looks a lot harder than the previous one, but it might have a lower yield strength and a much higher tensile strength.”
It isn’t easy to convince an engineer to consider trying a new technology when the competing process is so well established, but if you can uncover mistakes the old process was hiding or (even better) obviate laborious steps the old process requires—such as printing test coupons—you might just have enough on your side to overcome that inertia.
