May 13, 2014 | Category: Materials and Processes
There is an abundance of media outlets that speak to additive manufacturing (AM)/3D printing (3DP) as an inherent enabler to the manufacturing industry. However, there are also enablers for AM to be fully realized and more pervasively accepted. If one could draw a path from today's capabilities to what AM is being touted as providing tomorrow, you could identify both obstacles and enablers. That discussion space could be divided into three areas: materials, processing and economics.
Photo: Scanning electron microscopy of pits and particles due to process variances.5
As AM emerged, the industry generally borrowed its raw materials from pre-existing supply chains, primarily injection molding and powder metallurgy, and subsequently conditioned such material for AM processing. Therefore, an obstacle today is to prepare and optimize a given material system to a given technology. Instead a more advantageous approach would be to optimize the incoming material—and its supply chain—for AM processing. Creating an AM-specific supply chain would provide more consistency for incoming raw material, as well as creating a more affordable material offering. The enablers seem to be synergistic between increases in demand (via awareness) and serious consideration from the material industry. There continues to be further development in standardized material screening and preparation methodologies1 that promotes consistency and also may reduce the time to use new materials, including means to process varying levels of recycled materials2.
Materials may have a significant role in advancing the level of pervasive acceptance of AM products, but a certain showstopper is insufficient quality or an unreliable manufacturing process. There are some AM processes, such as vat photopolymerization, that incorporate well-understood processing knowledge with sufficiently high levels of reliability; however, this is not the case for all methods. The obstacles regarding processing seem to involve thermal management whether within the preexisting consolidated materials or at point of consolidation. Basic research3 has shown high correlations, and in many cases causation, between maintaining certain processing conditions (e.g. energy density for melt pool geometries) and the quality of part attributes (e.g. surface finish and density). Potential enablers could be advanced algorithms that map processing conditions/parameters to intended part properties where these maps maybe applied to any material system and AM process technology4.
There have been preliminary, albeit confidential, business case studies that evaluate part quantities produced against part complexity. Such graphs effectively show an economic sweet spot for AM parts in the quadrant of low-to-medium quantities with medium-to-high complexities. This has become a bit pedestrian in most commentators' list of “top benefits.” However, there are still economic obstacles for end-use readiness due to cost and time for post-processing AM parts. Whether it may be finishing, heat treatment or other post-processing efforts, the additional costs for post-processing may erode the original business case for AM. Enablers for AM economics are multi-faceted. Areas of new developments are in automating fixtures and reference points into the original part model design to provide a seamless transition between AM and traditional post-processing capabilities. Others are meeting final requirements by modeling features based on as-built conditions (e.g. surface finish, density, etc.) to eliminate the need for any further post-processing efforts. Institutes, such as America Makes, are making headway in some of these areas, as are university and national labs. The private sector continues to make new breakthroughs with clear transition paths. The AM industry continues to evolve and mature as such resources, motivations and applications abound.
For more information on EOS-Electro Optical Systems, visit eos.info/en. For more information about additive technologies in general, contact Tim Shinbara, Technical Director, AMT - The Association For Manufacturing Technology, at tshinbara@AMTonline.org or 703-827-5243.
1 Cooke, April, et al. “Properties of Metal Powders for Additive Manufacturing: A Review of the State of the Art of Metal Powder Property Testing.” NISTIR 78773 (2013).
2 Carroll, P.A., et al. “University of Manchester, et al “The Effects of Powder Recycling in Direct Metal Laser Deposition on Powder and Manufactured Part Characteristics.” RTO ATV-139. 18-1. Web. March 27, 2014.
3 The University of Texas – Austin's Solid Freeform Fabrication (SFF) Symposium for further investigation:
4 Beuth, Jack, et al. “Process Mapping for Qualification Across Multiple Direct Metal Additive Manufacturing Processes.” Solid Freeform Fabrication Symposium (2013). Web. March 27, 2014.
5 Gong, Haijun, et al. “The Effects of Processing Parameters on Defect Regularity in Ti-6Al-4V Parts Fabricated By Selective Laser Melting and Electron Beam Melting.” Solid Freeform Fabrication Symposium (2013). Web. March 27, 2014. The University of Louisville found that particles are formed by the molten materials which are ejected from melt pool due to recoil force of the evolving vapor; phenomenon which may be better managed with process controls.