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Dimensional Inspection For The Smart Factory

Metrology is of fundamental importance to future factories because so much factory efficiency relies on accurate data. A process or product cannot be improved unless it can be measured accurately. Metrology, the science and processes of measurement, captures data about both tooling and components to allow new manufacturing processes – such as additive manufacturing and robot-operated machining – to be tested and perfected. It can help process high volumes of data to make better decisions about “standard” but gradually improving manufacturing processes, like milling and turning.

The role of metrology in accelerating smart factories is underestimated, with much of the ‘Industry 4.0’ dialogue focused on robots and
automation. Measurement increases productivity while reducing waste and cost in manufacturing through improved control of production processes and more effective verification of components and final products.

Consider ‘Industry 4.0’ as a catchall to describe disruption in how things are being made, to improve speed, accuracy, flexibility and customization.

Design engineers used to design, make, measure, discover errors then remake something. New ‘generative engineering’ models allow a designer to describe what they want to make and the programme tells him/her the best way to revise the design, for manufacturability and cost. Simulation and better digital twins allows a manufacturing engineer to design and test the productivity of a new line or machine in the digital world before a dollar is spent on a prototype or new machine. This is making the physical prototype redundant.

In Metrology The Big Disruption is In-Process Measurement

Engineers want to measure and validate parts during manufacture – the cutting, welding, boring, moulding, and polishing – so they are fully validated at end-of-process with no final inspection stage required on a heavy, expensive coordinate measuring machine (CMM). Some industries and components still and will continue to require the batch testing of parts on a final CMM to be fully accredited for that application. But experts believe this will change as in-process, real-time metrology technology improves and validates more parts in production.

Another disruptive force is to move metrology out of manufacture altogether, and back into design engineering. Could robust measurement in CAD, combined with the best manufacturing technology, eventually bring an end to the need for in line or end-of-line inspection? Engineers and computer scientists are working on this today. “As long as everything is traceable, there could and should be another way to do it [metrology] than have a semiredundant check at the end just in order to be 100% positive that a part is correct, which can then result in scrap,” says Chuck Pfeffer, of FARO Technologies.

A white paper by Autodesk and FARO investigates the role of metrology in manufacturing and the Future of Manufacturing and Inspection,
covering scanning, data acquisition, sector applications and how different countries are developing metrology best practice.

For decades, inspection has occurred at the end of the manufacture of a part, and then again in final assembly. Smart factories, those moving towards the cyber-physical state of “Industry 4.0” production, aim to integrate measurement in the process itself and away from the lab.

The main drivers for this are speed and the avoidance of scrap – despite the best CAD data, machines and tooling, parts can fail validation and are rejected. In the aerospace, nuclear and tool and die industries, for example, this is unacceptably expensive.

“If you think of Industry 3.0 as the fixed CMM lab, and Industry 3.8 – what we have today – as getting an articulated scan arm onto the factory floor, to a level that bypasses lab CMM, then Industry 4.0 is fully integrated in-process metrology,” says FARO’s Chuck Pfeffer.

A major trend in future factory technology is the rise of non-contact, scanning measurement systems.Non-contact scanning technology is
divided into several types. These include:

Laser line scanning – uses a laser line at a fixed length from a camera, then uses triangulation to determine how far away the laser is from the source to measure a component.

Structured light – uses an LED projector, normally blue or white light, to project a pattern onto the surface of the component.
The deflection in the patterns is then recorded by one or more cameras, which defines the geometry of the component surface.

Optical/image technology – this covers products that use camera sensors to make non-contact measurements. The technology allows for improved accuracy and flexibility – one recent introduction was a camera based assembly verification system that uses an iPad camera to
align assemblies to CAD in real time, which enables inspectors to overlay CAD with real parts on the iPad screen to streamline their quality assurance processes.

X-ray and CT tomography – like a CT or MRI scan of a human, the tomography takes many images derived from the density of the material to build up a layer-by-layer picture of the part. Favoured for some AM components, it is suitable for difficult to access geometries but is slow.

Non-contact scanning offers speed and flexibility that a touch probe cannot match for specific tolerances above 30 microns. Laser line scanning and structured light have become more accurate and reliable for manufacturers. Today there are certain cases in certain applications where there is no longer a need to sentence (or pass quality for a customer) with a CMM contact system, especially with structured light scanning technology, where there is no need for a ‘first article inspection’. Aerospace companies, for example, are today sentencing parts for flight using structured light scanning only

Click here to download the full white paper

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