Measurement and characterisation of additively manufactured surface texture

Having a number of advantages over conventional (subtractive) manufacturing techniques, AM technologies possess the potential to change the paradigm for manufacturing. To facilitate the successful uptake of AM technologies into a wider range of applications, AM needs metrological methods to measure, evaluate and validate both AM processes and AM parts, in order to improve the accuracy and reliability of AM products.
The compound complexities of surface geometry and surface topography of AM parts have caused many problems for existing surface measurement techniques, including tactile, optical and XCT methods. Furthermore, due to the nature of AM processes, the AM-produced surface topography differs from conventionally machined surfaces. Following conventional surface characterisation methods, without considering the unique characteristics of AM surface topography, cannot lead to reliable and meaningful results. This dilemma is further aggravated by the complex surface geometry of the functional AM components, which result in serious distortions to surface characterisation techniques.
Facing these challenges, this research programme will investigate the applicability of various methods for the measurement of AM surface texture, including tactile, optical and XCT techniques. It will also develop bespoke surface characterisation methods for AM layer surfaces, aiming to reflect the characteristics of AM processes, and advanced surface characterisation methods needed for complex AM surfaces, with the aim of predicting the functionality of AM products.
The project aligns with the EPSRC's 'Manufacturing Technologies' topic within 'Manufacturing the Future' theme, and meets the UK's national strategy on AM technology. The outcome of this project will contribute to the control of AM process, and verification of AM product quality. It has great potential to positively impact on the UK's economy through the exploitation of AM technology in the key sectors concerned with high value manufacturing, including the aerospace, healthcare, high-end automotive and creative industries.

The proposed research programme, along with its outputs, will produce impacts across a range of groups.
1) Impact on the metrology industry
The metrology industry will be a direct beneficiary of a new generation of surface characterisation methods. It will open the door for XCT to become a valid tool for surface texture measurement, and thereby promote the adoption of XCT into surface metrology. It will also provide the metrology industry with a feasible solution for the inspection of complex AM products, which can be very difficult if using traditional measurement techniques.
2) Impact on AM stakeholders in key industrial sectors
The proposed project will benefit three key industrial sectors that extensively exploit AM technologies, i.e., aerospace, automotive and healthcare. In the aerospace sector, it will provide a metrological solution to verify that the surface quality of complex functional AM components lives up to the necessary stringent requirements; in the automotive industry, it will facilitate the quality control of AM parts, the geometrical non-conformance and manufacturing defects of which are of significant concern; in healthcare, it will help in the investigation of the bio-compatibility of surface texture in medical AM components, in terms of cell attachment and tissue growth.
3) Impact on wider industrial beneficiaries through the project partners
The proposed project, in collaboration with the National Physical Laboratory (NPL), will have an impact on NPL's relevant Good Practice Guides, and thus will inform the wide scope of industrial metrologists on how to effectively measure and characterise AM surface texture. Cooperation with the Manufacturing Technology Centre (MTC) will enable broadcasting the research outputs to a wider range of end-users in the high value manufacturing sector, helping them with AM product quality control. The impact on further AM exploiters, which require their AM components to have greater accuracy, surface finish or mechanical performance will, be through the MAPP EPSRC Future Manufacturing Hub of the University of Sheffield (MAPP: Manufacture using Advanced Powder Process).
4) Impact on the host institute
The proposed research programme aligns with the 'Metrology for Additive Manufacturing' platform topic of the recently-launched Future Advanced Metrology Hub (an EPSRC Future Manufacturing Hub), based at the Centre for Precision Technology (CPT) of the University of Huddersfield (UoH). It will strengthen CPT's research capability concerning surface metrology, and promote its participation in the development and enhancement of the relevant metrology standards.
5) Impact on staff development
Two PGR students and a PDRA involved in this project will be trained in a multi-disciplinary skill set, covering precision metrology, AM, applied mathematics and computer programming. Moreover, the research will enhance the learning experience of postgraduate students through the Advanced Metrology MSc course and other training activities delivered by the CPT.
6) Impact on society and economics
The proposed research programme will impact the UK's economy through the exploitation of AM technology in key sectors, concerned with high value manufacturing. It will also contribute to environmental and social sustainability through reducing scrap, saving raw materials, lowering CO2 emissions and being better personalised to suit consumers.