3D Printing (more correctly known as additive manufacturing) covers a range of different technologies, which all share one common feature – they add material, layer by layer, to create parts. This very different to normal manufacturing processes such as machining, which removes unwanted material from a big block of material. What differentiates the different 3D Printing techniques is how the material is added. Some use a laser to cure a liquid polymer; others extrude plastic, while some melt metal powder using high powder lasers. One of the key advantages of 3D Printing is the ability to produce parts that are too expensive to be able to be produced using traditional manufacturing methods. This may be due to the fact that only a few parts are needed or due to the highly complex nature of the geometry. This latter point is one of the main advantages of 3D Printing – the ability to produce shapes that are “impossible”. This ability of 3D Printing to produce “any” shape has allowed designers to create parts based purely on their functional requirements, rather than being constrained by the limitations of traditional manufacturing. An excellent example of this is comes from RMIT’s Centre for Additive Manufacturing, who used topological optimisation to design a titanium airframe bracket (shown in Figure 1) which resulted in a 40-60% mass reduction over the existing part.
One of the historical obstacles of 3D Printing, the cost of the equipment, has largely been overcome in recent years as result of the expiry of the first patents that were protecting the technology. Now, entry level 3D Printers can be bought for less than $500, which has allowed Schools, Universities and even individuals access to the technology. That said, these cost of high end, professional printers are still quite high and usually in excess of $100,000 and even above $1M.
These technologies are being touted as the future of manufacturing and may well replace traditional manufacturing in the future. However, before this can occur, a number of the limitations of 3D Printing need to be overcome. The first of these is speed. Although originally called Rapid Prototyping, these techniques are not what most people consider to be rapid. Certainly the production rate compared to traditional mass-production is very low. Coupled with the inability to build large parts or a large number of smaller parts simultaneously (typical build area is <500mm in each direction) means the cost per part is quite high. While for small numbers (less than a few hundred) the cost of 3D Printed parts can be cheaper than tradition manufacturing, high volume production is currently too expensive. Secondly, the surface finish of 3D Printed parts is generally inferior to that of other manufacturing technologies and therefore time consuming and costly surface finishing is often needed (see Figure 2). Another is that although the direct printing metal parts is possible, there are a limited number of materials that are available. In addition, the parts tend to have high levels of residual stress, which can affect the part’s accuracy and properties. Finally (and this is not meant to be an exhaustive list), although 3D Printing can produce parts with much greater complexity than conventional manufacturing technologies, it does have limitations. Many of these revolve around the need to support overhangs and attach parts to a substrate. A significant amount of research and development is being undertaken around the world aimed specifically at addressing these problems, and I have no doubt they will be solved.
In the right applications, 3D Printing will continue to grow in importance. Every week a new story appears about how 3D Printing has been used to make something faster, cheaper, better that was possible before. For now, it is largely limited to applications with low production numbers and to where a high degree of flexibility is desirable.