Additive Manufacturing Metrology
If engineering companies could measure additively manufactured parts more accurately and reliably, the use of AM in industry would accelerate, bene ting rms in areas like lightweighting and reducing waste. Renishaw has developed a neat solution for in-process measurement.
Then came additive manufacturing. Additively manufactured (AM) parts have several features that throw conventional metrology techniques off-course. Due to the 3D printing process, parts can have surface finish that is rougher than a machined part. With metal AM the particle size is typically 15 to 60 microns, bigger than the tolerances that components in some industries demand. A big particle can stick to the side of the layer, and if the measurement is recorded at the point where this sticks, the part will seem inaccurate.
Then there is the issue with shape complexity. “With AM you have almost infinite design freedom, you can make what you want,” said Professor Richard Leach, head of the Manufacturing Metrology Team at the University of Nottingham, a world-leading group devoted to additive manufacturing and engineering. “But in making such complex objects
you have to be able to measure them, which brings an extra level of complexity.”
New measurement techniques for AM are required and engineers have to think differently about sampling and measuring between several points on AM parts. Furthermore, as factory technology improves, metrology must be improved within the process of manufacture as well as the inspection stage at the end.
Measuring an AM build layer-by-layer for in-process measurement requires robust software to connect the AM machine to process monitoring hardware and then display the results in real-time, potentially from multiple systems.
Renishaw’s InfiniAM Spectral software, launched in 2017, operates with its LaserVIEW and MeltVIEW hardware, embedded in the company’s RenAM metal additive machines manufactured in Miskin, Wales. The software helps MeltVIEW to monitor emissions from the AM process across a wide spectral range. Sensors and photo detectors capture visible and infrared emissions from the build process which can spot build anomalies and measures the input intensity of the laser using an infrared photo diode. Tracking the temporal behaviour of each laser pulse provides insight about the evolution of the melt process. The Spectral software allows this data to be visualised on PCs, and for up to 8- AM systems for large scale manufacturing. The operator can in effect “see” the layers are accurate as they build.
How complete is this system for accurate in-process AM inspection?
“As far as the capability to solve problems such as surface finish and porosity, it is early days but the resolution and speed of the sensor signals has the potential to detect these issues as the build runs,” said Renishaw’s Robin Weston. “Any corrections required are presently dependent on the judgement of the engineers preparing the machine data, however we do anticipate being able to enable some autonomous feedback in the future.”
In another in-process measurement method, a team at the MAPP – Manufacture Using Advanced Powder Processes – Hub at the University of She eld is using thermal imaging to monitor the laser or electron beam spots (paths) as this passes across the bed. It provides in-process feedback and the operator can validate the build layer-by-layer. Renishaw is supporting metrology research with this EPSRC group, at the new Future Metrology Hub, headquartered at the University of Huddersfield, which launched in 2017, and other UK research institutions.
With so much research and development in AM metrology techniques in the UK currently, and Renishaw involved as research partner, sponsor and end-user, the UK is well placed to deliver reliable, industry-accredited methods of AM measurement in the very near future.
THE ANATOMY OF AN INFINIAM SPECTRAL EQUIPPED AM SYSTEM
1 500 W ytterbium fibre laser
2 In niAM MeltVIEW system
3 Focussing lens
4 MeltVIEW visible light photodiode
5 MeltVIEW infrared light photodiode
6 Focussing lens
9 Collimation lens
10 LaserVIEW system
11 Fixed mirror
12 Dynamic focussing lens 13 Sparks
15 Droplets of molten metal 16 Optical window
18 Melt pool
19 Galvanometer mirror
20 Fusion optical module
THE ANATOMY OF INFINIAM SPECTRAL DATA COLLECTION AND VISUALISATION
1. Up to 8 AM systems outputting data via a 1 Gigabit Ethernet OR up to 80 AM systems outputting data via
a 10 Gigabit Ethernet
2. 1 OR 10 Gigabit Ethernet connection supporting up to 8 OR 80 AM systems
3. Server with DataHUB software for 2D and 3D data collection and volume generation
4. Windows-based backup and storage server
5 1 Gigabit Ethernet connection
6 View 2D and 3D data volumes using In niAM Spectral software from multiple builds on individual PCs
A FOCUS ON INTEGRATED MEASUREMENT
Intelligent machining processes are critical to companies that want to exploit the full benefits of Industry 4.0 and at EMO 2017 Hannover Renishaw demonstrated the power of integrating its latest measurement technologies within a manufacturing process.
• SPRINT system with SupaScan – on-machine scanning designed for simple integration into machine tool applications requiring exceptionally fast workpiece set-up and the ability to monitor component surface condition
• IPC (intelligent process control) software for the company’s Equator flexible gauge which allows users to fully integrate the system with CNC machine tools to fully automate tool offset updates
• On-machine apps that allow machine tool probe routines to be swiftly and simply created, executed and reviewed and also allow real-time process monitoring
• Smartphone apps, which together with associated training materials and reference tools are designed to simplify the use of machine tool probes for wider adoption
• A new surface nish measurement probe which allows users of the multi-sensor REVO® system to fully integrate surface finish measurement and dimensional inspection on a single CMM
• Software for Renishaw’s XM-60 multi-axis calibrator with a new ‘free-run mode’ that allows users to capture data immediately, without having to define the positions, or even the number of targets.