Official estimates from the National Physical Laboratory in the UK say that up to one fifth of the total value of UK manufacturing activity is in product verification. Measurement ensures products work and operate safely. Product inspection, one of the main applications of measurement in manufacturing, benefits manufacturers in several ways. "If there are problems in a part you find them before the end-user, and if you measure and understand your processes you can make them more efficient," says Philip Hewitt, Manufacturing Product Manager at Autodesk.

The challenge is global and institutions such as The Physikalisch-Technische Bundesanstalt, the National Metrology Institute of Germany, are also working on better, real-time metrology methods for manufacturing to raise productivity. This investigative and validation role of measurement applies doubly to additive manufacturing because these processes are not fully understood yet. As manufacturing becomes more responsive, connected, quick and customizable, new and more flexible metrology techniques for machined, moulded, cast and additively manufactured (AM) parts will become more important.

The inspection of products for verification presents challenges for any conventionally manufactured part. Accuracy, reliability and cost of measurement, speed and where in the process of manufacture the measurement should reside, are the main challenges.

Machine tool probes and coordinate measurement machines, or CMMs, are still the cornerstone equipment for industrial measurement. CMMs are commonplace in industry for taking 3D measurements of parts and in recent years the lab- based CMM has been joined by mobile and robot- mounted CMMs and non-contact scanners for fast, post process monitoring and measurement.

For an additively manufactured component, there are more variables than for a machined part. Here metrology needs to measure dimension and material quality – because these are unknown. Additionally, additive manufacturing (AM) can make intricate geometries and internal structures which you may not be able to inspect with a traditional CMM.

"Therefore you have to think of new, clever techniques to inspect these parts, if you can’t see them from outside the component," says Robert Bowerman, Consultant Engineer at Autodesk. However, this is merely to assess the geometrical properties in the component, its shape and tolerances.

"An AM process simultaneously creates the geometry and the material; you are creating it from nothing and no data exists on the quality of the material before it is manufactured. Because of this, additional inspection is required in order to identify whether there is residual stress, fatigue or any other physical defect in the properties of the AM component." This differs from subtractive manufacturing, in which much is already known about the properties of the e.g. steel or titanium billet, or composite lay-up, before it is machined.

Download the white paper at Autodesk.com.