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Thoughts on 3D Printing

We are motivated to develop solutions that are personalised to meet the needs of the individuals using them. This is why we use technologies such as 3d printing. We are, however, acutely aware of its advantages and limitations, an awareness based on over 20 combined years of experience. Here’re some thoughts on the history and why we use 3d printing.

Although the popularity of 3d printing has only spiked in the last 5 or so years, it’s actually been around since the 1980s. It was 3d Systems who first developed Stereolithography Apparatus (SLA), which is a process still widely used today (image 1). SLA uses a process of photopolymerisation to cross link short chain liquid monomers into a solid, cross-linked polymer layer-by-layer. Geometry from a 3d computer aided design is sliced (a process that took many hours back then!) into thin layers (in the order of 0.1-0.2mm), which are traced by a laser on to the resin surface. Once one layer completed, the part moves into the bath of liquid monomer, the layer is recoated, then the next layer drawn. Specially developed laser scanning strategies have been developed to avoid layers from warping (which would cause the recoating blade to crash into the layer). A support structure made from the same material attaches overhangs and the part to a build platform. Once complete, the part is raised from the resin tank for draining. Excess resin is cleaned and the part post-cured in a UV oven to ensure complete polymerisation. The result is a solid part in a rigid resin. In the early years, the SLA process was the preserve of large companies, particularly in the aerospace and automotive sectors. The medical sector were also early adopters (SLA was used to fabricate replicas of human anatomy, which were then used to rehearse complex procedures (image 2). Many hospitals now have SLA-derived machines in-house). Industrial SLA machines are now much faster and becoming more automated than they were 25 years ago. They are still widely used in bureau service providers and companies wanting highly accurate and finely detailed parts. The major shift in recent years (as patents have expired) is cost reduction. 3d Systems have been challenged by companies such as Formlabs, who sell SLA-derived machines for prices that are more affordable to hobbyists, hospitals and small design consultancies. However, the running costs and part clean up processes remain a little expensive and dirty (UV curable resin can be a nightmare to clean up if you’re anywhere near sunlight!). It’s also still pretty environmentally nasty – the monomers aren’t nice, the cross-linked polymers can’t be recycled and there is a lot of waste along the way.

Image 1: Long exposure picture of a single SLA layer being drawn by the UV laser

Other major 3d printing technologies developed over 25 years ago include Selective Laser Sintering (SLS). Developed by both 3D Systems and EOS, both are still widely used, but still more so in larger organisations. SLS works from a powdered, typically nylon, material, which is heated in a build chamber to just below its melt point. A laser is used to tip each layer of the part over into being sintered to the previous layer. The powder surrounding the parts also supports them, which means no support structures are needed, which is great for volume production. Powdered materials do, however, need an inert atmosphere to avoid an explosion! EOS are arguably still the market leaders, but large companies, such as HP, have introduced new technologies such as multijet fusion, which are challenging this. Formlabs are also launching a more affordable SLS technology imminently. Exciting!

Image 2: model of a human lower jaw (mandible) with seletcively coloured teeth roots. Produced using SLA

Fused Deposition Modelling (FDM) is the last technology to discuss here. Developed originally by Stratasys (who merged with Objet in the last 5 years), it is FDM that has taken the hobbyist market by storm. This is for very good reason. Materials and running costs have become extremely affordable and much more functional. However, FDM technology isn’t just the preserve of hobbyists. Higher specification machines, an increasing range of performance materials and improving quality means FDM is fantastic for tough, functional parts, if used correctly (it can go wrong). We can also do clever things, like embed components within the polymer build using our Mark Forged machine (video 1).

So, how does this relate to you? At Trinity, we have over 20 combined years of experience in computer aided design and 3d printing technology. We know how to get the most out of 3d printing materials and overcome some of the design and processing challenges. It allows us to personalise products to your needs and make them more widely available. With a range of FDM, SLA, SLS technologies and even metal laser melting technologies available, we can create the right product. However, 3d printing is just one of our tools. We combine it with moulding techniques and traditional craft skills. We also test our products in collaboration with the end users – you. We believe that the product user, not technology push, is the essential ingredient to delivering our mission.

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