Emerald Group Publishing Limited
Article Type: Editorial From: Rapid Prototyping Journal, Volume 21, Issue 3
Looking at the papers in this issue, many of them address additive manufacturing of polymer materials. Research in this area dates back to the launch of Stereolithography in the late 1980s. However, the use of polymer systems to produce end-use production parts is still rather uncommon. The main barrier (cost issues aside) is a lack of confidence in the material properties of the parts produced. Several commonly used polymer additive manufacturing (AM) systems are still producing parts with anisotropic material properties, particularly in the Z-axis direction. Much research is being done in the area of material properties, as evidenced by some the papers in this issue. I am sure that we will overcome this problem and, until then, some designers are learning how to cope with anisotropy, either through intelligent part orientation, or by designing for the “worst” property value exhibited.
Two papers in this issue are focused specifically on metal-based AM. Using AM for metals is a more recent development than polymer AM and yet metal-based systems such as direct metal laser sintering (DMLS), selective laser melting (SLM) and electron beam melting (EBM) are already making significant inroads into end-use part production. This is seen particularly in the aerospace and medical sectors but increasingly in other applications areas as well. It appears that many of the material properties issues associated with metal-based AM have been solved relatively quickly. Parts with equivalent or better material properties to those made through casting are readily available. Interesting research developments such as functionally graded parts and grain-structure control are opening up new possibilities by offering capabilities beyond conventional processes. With all this in mind, it is not surprising that some of the metal AM system manufacturers are seeing huge increases in their sales volumes.
Obviously, there are problems that still need to be solved. Thermally induced warping is a notable issue. Much still needs to be done in respect to setting standards and obtaining process certification, particularly for the aerospace and medical industries. Confidence amongst the design community needs to grow. Nevertheless, there are enough examples of extremely clever design for metal AM (e.g. topologically optimized parts, light-weighting, internal lattices and improved fluid dynamics) to convince most forward-looking engineers that they cannot afford to ignore this technology.
So what of the future? Several Japanese machine tool vendors have now introduced “hybrid” manufacturing systems, i.e. machines that combine additive deposition of material with subtractive metal cutting, which in many ways, offer the “perfect” solution to manufacturing metal parts. The geometric freedom of AM is matched with the precision and repeatability of machining. Many researchers, including fellow Rapid Prototyping Journal editor, Ian Gibson, have been promoting the benefits of integrated additive/subtractive systems for decades. They are long overdue, but perhaps it required a serious interest in metal AM from high-value manufacturers to justify the substantial investment required to produce these machines. I have yet to see any parts that have come from these systems, but I am looking forward to seeing the impact they will have on future design innovation.
R. Ian Campbell