3D Printing: Behind the hype
James Woodcock, Group Editor across TCT, the magazine for the additive manufacturing and professional 3D printing industry and www.prsnlz.me, the hub for the 3D printing and personal manufacturing community, writes exclusively for BP&R on the benefits and advantages of the technology for the plastics industry.
In my role I am lucky enough to get to see some pretty impressive facilities across the UK, Europe, USA and beyond. People making everything from hearing aids and dental aligners to Nascar engines and parts for planes. The most impressive thing about these places is often the decidedly low-key nature of the buildings that house the processes, and the companies that run them. From 20th floor design micro-studios in the heart of a big city to sheds in towns to small industrial estates in the middle of nowhere — they’re all hiding a ‘secret’.
That secret is that away from the hype of mainstream coverage exists an ecosystem of established 3D printing technologies that are adding value across the design, prototyping and manufacturing supply chain worldwide. Far from being an overnight sensation or ‘the next big thing’ 3D printing (or additive manufacturing) is now 30 years old. From the outside it may appear that not much has changed since the commercialisation of the first 3D printer, a stereolithography machine, in 1986.
Nothing could be further from the truth. Quite apart from the fact that multiple technologies now exist for processing multiple materials (and sometimes more than one material at a time), it is the depth to which 3D printing is embedded in almost every major industry that really surprises. Plastics processing systems have historically led the way in terms of uptake and use and metals systems are still in relative infancy. Four main classes of 3D printing polymer processing technologies exist, all of which have the same fundamental modus operandii — to create parts layer-by-layer from ‘sliced’ digital models:
Stereolithography (SL)
The first ‘3D printer’ to make it to market was developed by Chuck Hull, founder of 3D Systems Corporation. In the SL process liquid photo-polymer resin is hardened by application of a laser that traces the image of each layer onto the surface of a vat of resin. Once the layer is complete, the vat drops, covering the hardened layer with fresh liquid resin, after which the process starts again. A range of materials are available, including bio-compatible materials and materials for wind tunnel testing.
Fused Deposition Modeling (FDM)
Here solid plastic is melted and extruded layer-by-layer into the final shape. FDM can process ABS meaning strong parts that better emulate an injection moulded piece. The layer-by-layer approach can cause weakness in certain planes (something that affects all 3D printing systems), depending on the orientation of the build. Other materials include ULTEM and polycarbonates in a range of colours. The FDM process is the inspiration for a vast majority of the low-cost consumer 3D printers now available.
Polymer Jetting
Jetting technologies deposit a UV-curable resin in the form of tiny droplets, much like a 2D inkjet printer does with ink onto paper. A UV lamp behind the print head immediately cures the resin. This technology allows ABS-like materials, bio-compatible materials and printing with materials of differing properties within the same build. Different polymers can also be mixed on the fly to create differing properties across a build.
Selective Laser Sintering (SLS)
Powdered polymer is sintered by a laser, which traces the geometry of each ‘slice’ onto the surface. Once sintered the bed drops and fresh powder is deposited on top allowing the process to continue. A variation of the theme, Selective Heat Sintering, uses rapidly heating resistors that scan close to the surface of the powder as the energy source instead of a laser. SLS machines predominantly process Nylon materials but the scope is rapidly expanding to include PEEK and PEKK for medical applications.
The greatest value for most users of 3D printing technology still lies in the prototyping phase where 3D printing can drastically reduce development times when used in-house or through one of the numerous service bureaux. Indeed the question tends to be not ‘should I use 3D printing’ but ‘how should I use 3D printing’. While FDM-style machines are available for around £1000 or less, the truth is that these systems will not be sufficient for professional use. The lowest-cost professional FDM systems start at around £6000 but with significant limitations on materials and build size. SLA, SLS and polymer jetting technologies are considerably more expensive in terms of purchase price and materials, meaning that accessing this technology through a bureau service is generally most appealing to SMEs.
When it comes to designing for the process it appears that the hype machine has worked its ‘magic’ here too. While even the major machine vendors may still persist with the ‘make anything you can design’ mantra, it tends not to be quite so simple. Each 3D printing process has limitations. In fact each process has dozens of limitations, some specific to that process but some that apply to all 3D printing processes. While it is true to say that there are fewer design limitations for 3D printed parts than for say injection moulding, machining or casting, it is also true to say that 3D printing-specific limitations really do exist. What these are and how to overcome them is beyond the scope of this piece, but it is something to bear in mind when assessing the technologies (and the salesperson’s spiel).
Another seldom mentioned factor that is worth asking about is part finishing. Almost every promotional video shows an operator removing a clean, ready-to-use part from the machine. Again, real-life is a disappointment here with every process requiring at least some part finishing when the build has finished. For SLA and polymer jetting this includes support removal, cleaning and further curing; for SLS excess powder must be removed and the part cleaned; for FDM supports need removing (either by breaking them off or by dissolving soluble support material) and a degree of polishing may be required.
So, who’s actually using this technology today? The medical industry is one area that 3D printing is growing in acceptance both for modeling and for direct interventions. The automotive and motorsport industries are also a hotbed of 3D printing innovation, with Formula 1 particularly invested in the technologies. From wind tunnel testing to aerodynamic parts on the real-life cars, plastics 3D printing is everywhere in F1.
If you’re after more insight about how the hype surrounding 3D printing is both skewing perspectives and opening up exciting new opportunities you can check out and excellent blog piece from industry insider, Joris Peels, on the TCT website: http://mytct.co/joris1