The importance of metrology – the science of measurement – in the manufacturing industry is often underestimated. Yet, inspection (in particular) is critical for ensuring products work and operate safely. Problems with a product can be found before they reach the end-user, and the measurement and understanding of processes can be used to make them more efficient.
However, inspection, even for conventionally manufactured products, is a complicated process. You must consider the accuracy, reliability, cost, speed and where in the process of manufacture the measurement should reside. This also varies across sectors. In automotive, inspection of parts is normally in a batch test cycle to ensure there is uniformity, while aerospace inspects each part individually and also insures they’re identical.
But with the dawn of Industry 4.0, comes the rise of additive manufacturing (AM) – a technology that is bringing even more complexities to the inspection process. Yet, it can’t be ignored since it’s integral to the future of smart factories, more efficient manufacturing and personalised products.
So, how can manufacturers prepare their inspection processes for AM?
Additive complicates traditional inspection processes
With AM components, there are more variables than a machined part. Metrology needs to measure both dimension and material quality – because these are essentially unknown before the part is manufactured. AM can also make intricate geometries and internal structures that may not be able to be inspected with a traditional coordinate measurement machines (CMM).
Because of this, additional inspection is required 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. It is also counterintuitive to manufacturers’ aim of reducing reduce cycle times for inspection, as well as eliminating scrap and costly rework.
Defining an AM inspection strategy for Industry 4.0
Achieving fast and reliable inspection of AM parts is much more difficult because the additive processes are not as accurate as cutting metal. Manufacturers must therefore think of new, clever techniques to inspect AM parts – whether an air-cabin partition or automotive component – especially if they can’t see them from outside the component.
There are currently no universal standards for how additively-made parts must be inspected, so defining a strategy can be difficult. However, we do expect the scale-up of AM to affect the standards industry, challenging international organisations such as ISO to set suitable standards for AM metrology in fast-paced, flexible factories.
Since there’s no current industry standard for AM, you may be thinking is it really necessary to define a tailored inspection process? Absolutely. If factories are to become faster and more flexible, inspection is a bottleneck to overcome, especially in industries where 100 per cent inspection is required, such as aerospace.
Measurement is therefore incredibly important for the advancement of smarter factories and truly working in an Industry 4.0 environment. And as manufacturing becomes more connected, customisable and flexible, advancing metrology techniques for additively manufactured (AM), as well as machined, moulded, cast parts, will become increasingly important too.
Looking to the future
The overall aim for manufacturers should be perfecting a flexible inspection process for AM that can deal accurately with parts, while allowing them to be different every single time and in higher volume production.
Until AM inspection becomes standardised, manufacturers can couple lab-based CMM with non-contact scanners, mobile and robot-mounted CMMs, as well as scanner arrays, for fast, post-process monitoring and measurement. Software, such as Netfabb, can also be used to programme different types of machines for additive processes; taking measurements of components and assessing their suitability for additive.
A further step into true ‘Industry 4.0’ territory will be the emergence of factory metrology based on GPS technology. Think ‘satellites’ that are fixed around the building, with seeing and recognition capability, meaning that that metrology is embedded within the building. The result? A truly contactless system.
AM is just one of the outcomes of Industry 4.0 that you should be taking seriously. We’ll see even more emerging technologies that will have the power to improve the whole effectiveness of the factory, so make sure to keep a look out for them.