March 2019

| STRATEGIES | It is advisable to start with the finished part and its intended purpose, and to determine the process, software, material and printer on that basis. What properties should the part have? Where and how will it be used? Will it be used as a ‘lost mould’ as a step in a production chain, will it be refined and finished or installed as it is, or is the plan to scale up to series production? Future-proofing is another consideration: will the printer be able to deal with changing requirements? Successful 3D printing depends on detailed planning. SLA process In the stereolithography (SLA) process, liquid plastic materials (photopolymers) are cured by UV radiation on a build platform. Each part is built up with layers of resin in a process also known as photopolymerisation (PP). The parts are produced directly from 3D CAD data without tools. During the process, the build platform is submerged in the photopolymer, and the UV source is usually a laser. When a part is finished, it is cleaned in a solvent to remove any resin. The part is then cured in a UV oven. SLA technology can be used where shape, fit and assembly are crucial. Using SLA for high-precision parts saves time, particularly when a number of prototypes are required or a single model needs to be produced quickly. SLA covers more applications than any other additive manufacturing process, including rapid manufacturing applications for high-precision and long-lifecycle prototypes. The tolerances of an SLA component are typically less than 0.05mm, and it offers the smoothest surface of all additive manufacturing processes. SLS technology The selective laser sintering (SLS) process builds up a thermoplastic workpiece layer by layer. The application of laser radiation then produces complex three-dimensional forms. It is possible to produce workpieces that could not be made by conventional methods. Complete assemblies can be printed as one part, which cuts costs and improves functionality and operational safety. The thermoplastic powder is applied to a build platform and the layers are sintered into the powder bed. The build platform is then lowered slightly and a new layer applied. A key benefit is that there is no need for support structures. Users can also choose from various thermoplastics which differ in rigidity, robustness and heat- resistance. MJP The MultiJet printing (MJP) process produces precision plastic parts for prototypes, form and fit models or rapidly produced alternatives to tools. MJP printers from 3D systems can print rigid or flexible parts with ABS- like plastics and real elastomers. It is even possible to produce compound materials with custom-made mechanical properties, and to print complex parts with several materials. One of the key features of MJP is exceptional resolution, with a layer www.smartmachinesandfactories.com March 2019 | 21 |