Table 14. Redesigned Flap Track Multiple Attribute Decision Matrix
6. Summary and Conclusions
This paper has presented an initial investigation into designing for WAAM. The literature review identified that most existing Design for Additive Manufacture methods are developed for powder bed additive manufacturing processes and cannot be applied to WAAM, due to the very different
manufacturing constraints and opportunities of these technologies. An initial set of design guidelines for WAAM have been developed based on experimental work undertaken at Cranfield University that can be used to help designers to take into account the capabilities and constraints of WAAM.
The paper also provides a build orientation assessment method for WAAM production that can help designers to consider a wide range of WAAM manufacturing strategies for a part and then tailor the design where possible for WAAM manufacture. This structured approach ensures that the design is adapted to WAAM production from an early in the design process. The assessment criteria for WAAM are defined as substrate waste, deposited material mass, number of build operations, build complexity and symmetry. These are different criteria to those used in other AM build orientation assessments, for example the method developed by Ponche et al. (2014) which minimises support volume, minimises cost and maximises quality.
31
The use of a multiple attribute decision matrix provides a quantitative method to compare different build options. This approach helps the designer to consider a wide range of options to minimise the volume of waste material and manufacturing complexity, however engineering
judgement is still required in order to ensure a practical solution. The method has been tested on two engineering case studies and the results reviewed by WAAM manufacturing experts at Cranfield University. The methodology has been shown to select appropriate build strategies for WAAM parts and helps the designer to consider potential design changes that could prove the manufacturability of WAAM parts.
One potential weakness of the multiple attribute decision matrix methodology is that poor performance in one criterion can be compensated by good performance in another, meaning that the best ranked solution could have a poor score in one attribute.
Future work will include testing the methodology on a wider range of industrial parts and assessing its suitability to assist non-specialist designer engineers when designing for this new manufacturing process.
Acknowledgements
The authors would like to thank all members of the Wire and Arc Additive Manufacturing research team at Cranfield University for their contributions to this research paper. In particular we would like to thank post-graduate students Nan Lin, Anthony Fernando, Wang Lei, Robert Emms and Panos Kazanas who have all contributed to the research through their post-graduate thesis projects.
References
Adam, Guido A O, and Detmar Zimmer. 2014. “Design for Additive Manufacturing-Element Transitions and Aggregated Structures.” CIRP Journal of Manufacturing Science and Technology 7 (1). CIRP: 20–28. doi:10.1016/j.cirpj.2013.10.001.
Allen, J. 2006. “An Investigation into the Comparative Costs of Additive Manufacturing vs. Machine from Solid for Aero Engine Parts.” In “Cost Effective Manufacturing via Net-Shape
32
Processing”, Proc. Meet. RTO-MP-AVT-139,. Neuilly-sur-Seine: NATO.
Atzeni, Eleonora, and Alessandro Salmi. 2012. “Economics of Additive Manufacturing for End-Usable Metal Parts.” The International Journal of Advanced Manufacturing Technology 62 (9–
12). Springer-Verlag: 1147–55. doi:10.1007/s00170-011-3878-1.
Beeley, Peter R. 2001. Foundry Technology. Butterworth Heinemann.
Boothroyd, G. (Geoffrey), Peter. Dewhurst, and W. A. (Winston Anthony) Knight. 2011. Product Design for Manufacture and Assembly. CRC Press.
Bralla, James G. 1999. Design for Manufacturability Handbook. McGraw-Hill.
Byun, Hong S., and Kwan H. Lee. 2006. “Determination of Optimal Build Direction in Rapid Prototyping with Variable Slicing.” The International Journal of Advanced Manufacturing Technology 28 (3–4). Springer-Verlag: 307–13. doi:10.1007/s00170-004-2355-5.
Campbell, John. 2004. Castings Practice : The 10 Rules of Castings. Elsevier/Butterworth-Heinemann.
Canellidis, V., J. Giannatsis, and V. Dedoussis. 2009. “Genetic-Algorithm-Based Multi-Objective Optimization of the Build Orientation in Stereolithography.” The International Journal of Advanced Manufacturing Technology 45 (7–8). Springer-Verlag: 714–30. doi:10.1007/s00170-009-2006-y.
Clegg, A. J. (Allen J.). 1991. Precision Casting Processes. Pergamon Press.
Ding, J., P. Colegrove, F. Martina, S. Williams, R. Wiktorowicz, and M.R. Palt. 2015. “Development of a Laminar Flow Local Shielding Device for Wire+arc Additive Manufacture.” Journal of Materials Processing Technology 226: 99–105. doi:10.1016/j.jmatprotec.2015.07.005.
Gibson, I., D. W. Rosen, and B. Stucker. 2010. Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing. Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing. doi:10.1007/978-1-4419-1120-9.
33
Hague, R, S Mansour, and N Saleh. 2004. “Material and Design Considerations for Rapid Manufacturing.” International Journal of Production Research 42 (22): 4691–4708.
Herrmann, Jeffrey W., Joyce S. Cooper, Satyandra K. Gupta, Caroline C. Hayes, Kosuke Ishii, David Kazmer, Peter A. Sandborn, and William H. Wood. 2004. “New Directions in Design for Manufacturing.” In 2004 ASME Design Engineering Technical Conferences and Computers and Information in Engineering Conference.
Hu, Zhu, Kunwoo Lee, and Junghoon Hur. 2002. “Determination of Optimal Build Orientation for Hybrid Rapid-Prototyping.” Journal of Materials Processing Technology 130–131: 378–83.
doi:10.1016/S0924-0136(02)00727-6.
John, Michael. 2013. “Inner Wing (Metallic) Design for SL-12 Reusable Orbiter.” Cranfield University.
Kalpakjian, Serope, and Steven R. Schmid. 2008. Manufacturing Processes for Engineering Materials. Pearson Education.
Kazanas, P., P. Deherkar, P. Almeida, H. Lockett, and S. Williams. 2012. “Fabrication of Geometrical Features Using Wire and Arc Additive Manufacture.” Proceedings of the Institution of
Mechanical Engineers, Part B: Journal of Engineering Manufacture.
doi:10.1177/0954405412437126.
Kerbrat, Olivier, Pascal Mognol, and Jean Yves Hascoët. 2011. “A New DFM Approach to Combine Machining and Additive Manufacturing.” Computers in Industry 62 (7): 684–92.
doi:10.1016/j.compind.2011.04.003.
Kranz, J., D. Herzog, and C. Emmelmann. 2015. “Design Guidelines for Laser Additive
Manufacturing of Lightweight Structures in TiAl6V4.” Journal of Laser Applications 27 (S1).
Laser Institute of America: S14001. doi:10.2351/1.4885235.
Kulkarni, Prashant, Anne Marsan, and Debasish Dutta. 2000. “A Review of Process Planning
34
Techniques in Layered Manufacturing.” Rapid Prototyping Journal 6 (1): 18–35.
doi:10.1108/13552540010309859.
Laverne, Floriane, Frédéric Segonds, Nabil Anwer, and Marc Le Coq. 2015. “Assembly Based Methods to Support Product Innovation in Design for Additive Manufacturing: An Exploratory Case Study.” Journal of Mechanical Design 137 (12): 121701. doi:10.1115/1.4031589.
Lijuan Sun. 2015. “Manufacturing Internal Features in Metallic Structures Using WAAM Process.”
Cranfield University.
Lin, Nan. 2015. “Design for Wire and Arc Additive Manufacturing: Development of Design Guidelines and an Automation Design Tool.” Cranfield University.
Martina, Filomeno, and Stewart Williams. 2015. “Wire+arc Additive Manufacturing vs. Traditional Machining from Solid: A Cost Comparison.”
Mehnen, J., J. Ding, H. Lockett, and P. Kazanas. 2011. “Design Forwire and Arc Additive
Layermanufacture.” In Global Product Development - Proceedings of the 20th CIRP Design Conference. doi:10.1007/978-3-642-15973-2-73.
Mehnen, Jörn, Jialuo Ding, Helen Lockett, and Panos Kazanas. 2014. “Design Study for Wire and Arc Additive Manufacture.” International Journal of Product Development.
doi:10.1504/IJPD.2014.060028.
Osa-Uwagboe, N. 2010. “A-9 Dragon Fly Medium Range Airliner Metallic Flap Design.” Cranfield University.
Ponche, Remi, Olivier Kerbrat, Pascal Mognol, and Jean Yves Hascoet. 2014. “A Novel Methodology of Design for Additive Manufacturing Applied to Additive Laser Manufacturing Process.”
Robotics and Computer-Integrated Manufacturing 30 (4). Elsevier: 389–98.
doi:10.1016/j.rcim.2013.12.001.
Rosen, David W. 2014. “Research Supporting Principles for Design for Additive Manufacturing.”
35
Virtual and Physical Prototyping 9 (4): 225–32. doi:10.1080/17452759.2014.951530.
Sequeira Almeida, P. M. 2012. “Process Control and Development in Wire and Arc Additive Manufacturing.” Cranfield University.
Thompson, Mary Kathryn, Giovanni Moroni, Tom Vaneker, Georges Fadel, R. Ian Campbell, Ian Gibson, Alain Bernard, et al. 2016. “Design for Additive Manufacturing: Trends, Opportunities, Considerations, and Constraints.” CIRP Annals - Manufacturing Technology 65 (2): 737–60.
doi:10.1016/j.cirp.2016.05.004.
Wang, Fude, Stewart Williams, Paul Colegrove, and Alphons A. Antonysamy. 2013. “Microstructure and Mechanical Properties of Wire and Arc Additive Manufactured Ti-6Al-4V.” Metallurgical and Materials Transactions A 44 (2). Springer US: 968–77. doi:10.1007/s11661-012-1444-6.
Williams, S W, Filomeno Martina, A C Addison, J Ding, G Pardal, and P Colegrove. 2015. “Wire + Arc Additive Manufacturing.” Materials Science and Technology 836 (March):
1743284715Y.000. doi:10.1179/1743284715Y.0000000073.
Zhang, Jun, and Frank Liou. 2013. “Multi-Axis Planinng of a Hybrid Material Deposition and Removal Combined Process.” Journal of Machinery Manufacturing and Automation 2 (3).
World Academic Publishing: 46–57.
36 Appendix A. DfWAAM Guidelines
Wire + Arc Additive Manufacture – Design Guidelines
Feature Example Description
Manufacturing Process – Wire and Arc Additive Manufacture General geometry/ part form General part size Part dimensions There is no theoretical limit on maximum part length and wall
thickness for WAAM manufacture. The minimum practical part length is typically 50mm, and the minimum deposited wall thickness is 2mm. Thinner walls can be achieved by post-machining and are limited only by the post-machining capabilities.
Symmetry
Parts should be designed where possible so that the part can be built symmetrically on both sides of the substrate in order to avoid buckling distortion and for ease of tooling. Alternatively parts may designed to allow them to be built back-to-back on the same substrate to achieve a symmetrical build and then separated after deposition
Enclosed Features Enclosed features can be produced using WAAM but may be
difficult to inspect or post-machine
Unfinished Faces
Further cost savings can be achieved by leaving faces unfinished in unstressed regions. Care must be taken not to introduce stress concentrations on unfinished faces. Fatigue and damage tolerance should also be considered.
37
Manufacturing Process – Wire and Arc Additive Manufacture General geometry/ part form Part Machining Considerations Ensure that all design features can be accessed for post
machining
Avoid very thin walls that may distort during manufacture
Avoid high aspect ratio features and undercuts
Apply fillet radii on all internal corners (Bralla, 1998)
For parts that must be post-machined standard design for machining guidelines should be followed WAAM parts. Alternatively, using an integrated system, parts may be machined in-process after each layer is deposited. Consider whether some faces can be left unfinished to further save cost. The manufacturing process should be carefully planned to achieve the ease of tooling and work holding during machining.
Undesirable Features Complex 3D Lattice Structures are not appropriate for WAAM
deposition and are costly/ inaccessible for post- machining. Avoid these design features for WAAM.
Unsupported thin members may be difficult to deposit and costly to machine.
Wall Internal corners
Unfavourable
Better
Internal corners should be designed with a generous radius to allow for post machining and avoid stress raisers.
External corners
Unfavourable
Best
External corners are recommended be designed with a generous radius where possible for ease of manufacture. This will reduce the number of stop/ starts during deposition and reduces material waste.
Parts with sharp external corners can be produced but are more difficult to manufacture due to residual stresses in the corners.
38 List of Figures