Smart Residual Stresses Monitoring for Metal Additive Manufacturing – EM-ReSt

"Metal Additive Manufacturing (AM) is an emerging technology for rapid prototype manufacturing, benefitting aerospace and medical devices, as the immediate manufacturing of high-value, complex structured components is usually necessary in these industries. Hence, the structural integrity of printed structures is extremely important and should meet the specifications and high standards of the above industries. In several metal AM techniques, e.g. selective laser melting (SLM), electron beam additive manufacturing (EBAM) and wire arc additive manufacturing (WAAM), residual stresses and micro-cracks that occur during the manufacturing procedure can result in irreversible damage and structural failure of the object after its manufacturing. Repetitive faults which occur during manufacturing due to incorrect estimation of appropriate operating conditions of the printer should be eliminated, as any waste is undesirable and costly for a company.

The nature of some AM methods means that not all Non-Destructive Testing (NDT) techniques are effective in detecting residual stresses. Thermography, X-ray computed tomography (CT scan), or digital radiography are limited by the resolution of images (thermography), they are bulky and costly (up to £100k), are not suited to residual stress detection. Our solution, EM-ReSt, functions as an add-on to existing AM processes, comprising two sets of NDT techniques: Electromagnetic Acoustic Transducers (EMAT) and Eddy Current Testing. A crucial (and novel) extension of the proposed system is the incorporation of big data collection from the sensors and analysis through machine learning (ML) for estimating the likelihood of the AM techniques to introduce anomalies into the printed structures before the beginning of the manufacturing. A digital system that will estimate the potential and deficiencies of any AM technique for given structures will be developed and utilised for the establishment of a preliminary set of AM standards. Hence, more robust and reliable components will be printed and used.

EM-ReSt is fast (msecs/measurement and overall scanning time does not exceed a minute), reliable (90% PoD), non-destructive online monitoring of AM techniques, can achieve 15% reduction of faulty outputs with the use of 4 times more cost-effective monitoring system, has low profile sensing hardware with potential for EMAT and EC miniaturization. Our initial target markets are the global aerospace and automotive component manufacturing market. This project represents a clear technological innovation for the UK AM industry, and major growth opportunity for the SME supply chain consortium, which is forecast to generate revenues of £72.5M and 362 new jobs 5 years post-commercialisation."