| dc.description.abstract | Life cycle assessment (LCA) is the future of calculating the environmental impact of industrial processes such as additive and subtractive manufacturing. By using designated software to accomplish an easily readable scoring system and do on-demand design alterations or change manufacturing methods to get direct environmental data.
The principle of the circular economy is also discussed at the micro level, considering material handling, and some macro considerations like material waste management outside of the company structure. Discussing recyclability and how increasing sustainability by greener production can contribute to circularity.
The valve wedge part was manufactured at Stamas Solutions AS with the subtractive manufacturing method using CNC Mill, and at AM North AS using powder bed fusion laser beam method. The valve wedge was manufactured in 316L material for both processes.
The additive manufacturing categorization (AMC) was done using a chart and conducting a risk assessment of the different considerations mentioned in the DNV-ST-B203 Additive manufacturing of metallic parts standard. The findings gave a result that indicated the need for AMC 2 level testing and qualification. A BPQ was printed, and tests were conducted at Quality Lab Stavanger and at University of Stavanger laboratory facilities at Department of mechanical and structural engineering and material science. Destructive testing such as tensile, impact, hardness, micro and macrostructural, and non-destructive tests such as visual, volumetric, and surface were performed to complete the BPQ and part testing. The BPQ is to give a basis for the mechanical properties of the printed parts.
The Dassault systems: 3DExperience software was used to simulate and analyze the environmental impacts of additive manufacturing and subtractive manufacturing using the EF 3.0 impact assessment method and ecoinvent library for the LCA category processes. The LCA yielded a total environmental footprint score of 3.8e-3 points for AM, 1.30e-4 points for SM and a total difference of 3.7e-3 points. Although the AM process is ‘less’ environmentally friendly than the SM process trade-offs should be considered in the selection process of manufacturing methods.
The BPQ and part testing requirements according to DNV-ST-B203 was to print the testing specimens according to the SQB specifications and perform testing according to the selected AMC 2 level for the part testing requirements. The BPQ tests were as follows: Tensile, impact, hardness, microstructural analysis and macrostructural analysis. Where the results were: 464,6 MPa yield strength, 598,0 MPa UTS, 43% elongation, 60.5% reduction of area, 114,0J average, 221 HV10 average, macrostructural gave visible fusion lines and weld pools as described in the standard, and the microstructural analysis at 150x gave no indication of poor material properties. Whilst for the 1kx magnification on microstructural analysis gave some indication on oxides in the structure. EBSD was also performed and gave indication on 99.3% austenitic properties in the structure and 0.7% of other phases in the material (likely to be ferrite) or badly indexed phases. Lastly, the EBSD indicates that the average grain size is around 13,8µm.
Keywords: Additive manufacturing, Subtractive manufacturing, Life cycle assessment, Circular economy, AMC, qualification, BPQ, SQB, manufacturing technology, material technology, EBSD, SEM. | |
