Plastometrex pushes indentation testing as a coupon-free check for metal AM parts

Plastometrex says half its customers work in additive manufacturing and defence, using its indentation test to measure yield and tensile strength without printing test coupons. The method is now covered by ASTM E3499-25, which should ease the hesitation of conservative manufacturing engineers. Its CTO also reports property variation of 15 to almost 20 percent in metal AM parts, even when best practice is followed.

Context Yield strength is the stress at which a metal starts to deform permanently, while tensile strength is the maximum stress it withstands before breaking. A hardness test alone cannot give the yield value.

How does profilometry-based indentation plastometry work?

The PIP test starts like a hardness test: an indent is made in the metal under a defined load and the resulting surface profile is measured. A finite element model then simulates the same test and adjusts the material properties, including yield strength and work hardening, until the simulated shape is almost indistinguishable from the measured one. The properties that match the shape are taken as the material's properties. The model runs locally on Plastometrex hardware.

The company, which grew out of CTO Jimmy Campbell's PhD work at the University of Cambridge, sells lab machines and field units. The field units were first developed for the oil and gas industry to confirm steel grades in pipelines without sending samples to a lab.

Why is metal AM a natural fit?

Campbell says around 50 percent of customers are in additive manufacturing and/or defence, from early material development to quality control at the point of need, where test coupons cannot be printed and sent away. Metal AM machines have dozens or hundreds of parameters, plus environmental and feedstock variation. Campbell reports 15 or almost 20 percent variability in properties in both powder bed fusion and directed energy deposition, even with best practice, and says testing several regions of one part reveals variation that was not picked up before.

In a case study with the British Army and Meltio, a printed replacement Land Rover brake pedal showed a small rise in yield value and a large rise in tensile strength. A hardness test alone could not have shown the yield strength.

How is the inertia around a new test method being addressed?

Plastometrex started with lab units for academia and R&D, where standardisation matters less, and partnered with early adopters such as Nikon and Renishaw. Nikon contributed a study comparing tensile and PIP testing on printed metals. Together with Airbus, Renishaw and the National Physical Laboratory, the company helped validate the method and formalise ASTM E3499-25, positioning it as an audit-ready alternative to standard tensile testing. Campbell describes the standards process as a chicken-and-egg problem: committees want commercial uptake, and buyers want a standard.

What it means

For manufacturers adopting metal AM, qualification is often the larger cost than printing itself, and test coupons add time and material, especially for spare parts made on site. A standardised method that reads yield and tensile strength on the actual part could shorten release steps. The reported 15 to 20 percent property spread is a reminder that one coupon may not represent a whole part. Small and mid sized firms should check whether their customers and auditors accept ASTM E3499-25 for their application.

Frequently asked questions

What does PIP testing measure that a hardness test does not?

It provides yield strength and stress-strain behaviour, from which tensile strength follows. A hardness test only allows an approximate tensile value through conversion.

Is PIP testing standardised?

Yes. Plastometrex, Nikon, Airbus, Renishaw and the National Physical Laboratory helped formalise ASTM E3499-25, which recognises PIP as an alternative to standard tensile testing.

Why is it relevant for printed spare parts?

At the point of need, test coupons cannot always be printed and sent to a lab. Testing the part itself, as in the British Army and Meltio brake pedal case, avoids that step.