SLA 3D Printing: Fast, durable, accurate, cost effective and beautifully tactile.

SLA 3D Printing.

We get it. Your biggest challenges in product design and development are not necessarily the technical ones. You’re up against customer needs and expectations, user needs and expectation, manufacturability, costs, competition and, of course, that increasingly pressing issue of sustainability.

Everyone now knows that 3D printing is cost-efficient; it’s quick; materials are relatively robust and often watertight; and above all, it allows for design freedoms like never before. This 5 minute read offers insights into why SLA (stereolithography) might not just be a technical solution, but could help overcome some of the other challenges facing industrial and product designers

Stereolithography or SLA 3D printing

SLA is the grandfather of industrial 3D printing. This is largely for its ability to produce fast, highly accurate, infinitely detailed, highly polished, water-resistant parts. One of the greatest benefits of SLA is its versatility. The 3D print materials innovators have come up with a range of resins with mechanical, thermal and optical properties that match standard-, industrial- and engineering-grade plastics.

With a print bed of 800 x 800 x 600mm, the NEO 800 is one of the largest, fastest industrial SLA printers available in the UK. This outstanding machine has a scanning resolution of 1 micron, ensuring side wall quality (with a <0.5mm potential) is superb; intricate detailing is easy; and the smoothest of finishes is possible. With three of these award-winning, industrial sized printers in our 3D printing stable, we have significant capacity and can work to tight turnaround times.

Designing for Large Bed SLA 3D Printing

Our downloadable infographic for designing for SLA 3D Printing can be found here. It’s worth noting, though, that if you want your printed parts to live up to their reputation for being some of the smoothest, most detailed around, special attention should be given to the following.

• SLA printing requires support structures. The larger the part, without clever positioning on the print bed, the more support structures there will be. You can minimise A-surface support structures easily enough; but should your part contain overhangs, you’ll need to factor these in. As a rule of thumb, overhangs greater than 1mm or at an angle greater than 19º require support. We suggest that for large parts, particularly cylindrical ones, you should consider hollowing the part out. This will save on both material costs and finishing time. Don’t forget to leave drainage holes.
• Minimise corners. Sharp corners increase stress areas and can lead to print failures or cracks.
• Wall thickness impacts build quality. With its super resolution, the NEO 800 provides fantastic side wall quality. However, walls of less than 0.5mm thickness will require supports, especially for larger prints.
• SLA lets you incorporate holes in your design. However, regardless of machine resolution, holes are notoriously hard to incorporate because they may close off during the printing process. Ask your provider for a minimum hole size, and design with the belief that anything smaller may have to be drilled by hand – or laser beam.
• Threads inside apertures on SLA prints will not necessarily have the same hold power that prints using more industrial processes such as FDM or DLP will have. You simply can’t have that super smooth, layer-free finish and maintain material super strength. We suggest that you opt for threaded inserts.
• Embossing and debossing. Infinitesimal detailing is easily achieved with an SLA print, whether large or small. However, you don’t want your impressions to clog with excess resin, so a minimal depth of 0.1mm is recommended. For debossed detail, 0.4mm is recommended.

Materials matter

We run two exceptional resins on our three NEO 800 SLA machines.

Somos® EvoLVe 128 is a shiny off-white, durable resin that produces highly accurate, highly detailed parts. Designed for easy finishing (it boasts an exceptional A-side surface finish), EvoLVe has a look and feel that is almost indistinguishable from traditional thermoplastics. It can be bonded to other plastics and metal and can be painted when a plastic-friendly primer is applied. For parts that might be handled a lot, this slightly flexible material is probably a good bet.

Somos® WaterShed XC 11122 is a crystal clear, highly water resistant, very hard engineering resin with ABS-type properties. Again, it has been designed to deliver on intricate detailing, thinner walls of less than 5mm, and an exceptionally smooth finish. Beloved by model makers for creating pattern masters and mould cores, it can be primed easily. WaterShed parts are rigid but not shatterproof. They’re great for lenses (with a glass-like finish achieved through post-processing) and fluid flow analysis.

For much smaller parts (less than 500 x 500 x 580mm), we run a grey resin, Somos® Taurus. This robust and durable resin does have a trade-off – more finishing is required to produce a smooth surface and fine detailing may be lost as a result. As this material is not run on our NEO 800s, it may also take longer to print. You can find out more about our other SLA technologies here.

Painting and finishing

There are cons to every printing type. Whilst the NEO 800 printer, and the two resins mentioned above, promise to reduce printing time, and deliver an exceptional, highly polished A-surface quality, B-surface quality is not so great.

Fortunately, SLA resins are some of the easiest to clean up and you’ll find the cost for this is generally built into your price per cubic centimetre.  As well as support removal, post processing can also include sanding the ‘pips’ (or support nibs), priming, and spray painting if you require.

If you’re looking to finish your own parts, painting and texturing tips are detailed in our story of #aurorarises. Two Paragon senior model makers explain in detail the steps they took to achieve the super-smooth complexion whilst retaining shadows, using primers, lacquers and water- and cellulose-based paints.

Optimising your build

Most designers have a good understanding of the mechanics of designing for 3D. However, build optimisation and orientation can positively impact stability, finishing and printability, in turn contributing to keeping costs to a minimum and ensuring that speedy turnaround, helping you deliver your client’s product to its marketplace sooner.  Please do tell us when time and costs are of the essence, and we will assist where we can to ensure builds are optimised to the maximum.

Points to consider include:

• Preserving integrity at intersections. This means any model with merging features should be printed face down to ensure that instead of coming together in a joint, the merging features will come together down specific pathways, thereby reducing weakness at intersections
• Reduce likely minima. These are the points at which the part touches the surface at its lowest point. You’ll need to consider the inclusion of support structures at this point which may increase both materials and volume.

In conclusion and towards sustainability

The good news is that SLA 3D printing in general is a pretty sustainable process. Apart from the support structures, there’s very little waste. You build the part, and that’s what you get. Parts are produced quickly, and on demand, so there’s little need to factor in lengthy waiting times for tooling. Indeed, if you need to change design, you don’t have to go through the whole rigmarole of retooling. It’s a simple tweak and a new design is rolling off the machine, complexity dependent, within two to three days. SLA parts can be large, and complex, but they’re still light and that means the efficiencies in production are enhanced. Using SLA printing may not be the net zero you’re striving for, but it’s a huge step in the right direction.

Paragon’s SLA capability is one of the largest in the UK. We’ve been operating the NEO 800 technology since its inception in 2017 and believe we understand how we can make your prototyping and model making as quick and cost-effective as is feasibly possible. If you’d like a quote, click below.