Guide to Stereolithography (SLA) 3D Printing
Stereolithography (SLA) is an additive manufacturing - commonly referred to as 3D printing - technology that converts liquid materials into solid parts, layer by layer, by selectively curing them using a light source in a process called photopolymerization. SLA is widely used to create models, prototypes, patterns, and production parts for a range of industries from engineering and product design to manufacturing, dentistry, jewellery, model making, and education.
How it works
The UV laser points at two mirror galvanometers, which direct the light to the correct coordinates on a series of mirrors, focusing the light upward through the bottom of the vat and curing a layer of photopolymer resin against the bottom of the tank. A combination of vertical build platform and horizontal tank movement then separates the cured layer from the bottom of the tank, and the build platform moves up to let fresh resin flow beneath. The process repeats until the print is complete. The tank is heated to provide a controlled environment, and a wiper passes across the tank in between layers to circulate resin and remove clusters of semi-cured resin. Our software tool automatically create supports during the preparation of the 3D models, but they can also be adjusted manually. Once the printing process is completed, these supports must be removed from the finished product manually. SLA creates parts with a smooth surface finish directly out the machine. This is ideal for applications that require a flawless finish, and also helps reduce finishing time, since parts can easily be sanded, polished and painted.
Z-axis layer height is commonly used to define the resolution of a 3D printer. This can be adjusted in between 25 and 100 microns on our Form 2, with a trade-off between speed and quality. In comparison, FDM and SLS printers typically print Z-axis layers at 100 to 300 microns. However, a part printed at 100 microns on an FDM or SLS printer looks different from a part printed at 100 microns on an SLA printer. SLA prints have a smoother surface finish right out of the printer, because the outermost perimeter walls are straight, and the newly printed layer interacts with the previous layer, smoothing out the staircase effect. FDM prints tend to have clearly visible layers, whereas SLS has a grainy surface from the sintered powder.
Our SLA printers can create accurate parts with repeatable dimensions. This is essential for functional applications. The combination of the heated resin tank and the closed build environment provides almost identical conditions for each print. Better accuracy is also a function of lower printing temperature compared to thermoplastic-based technologies that melt the raw material. Because SLA uses light instead of heat, the printing process takes place at close to room temperature, and printed parts don't suffer from thermal expansion and contraction.
General accuracy of SLA prints is 50 to 200 microns depending on size, resin, model geometry and support generation.
What material do I order in?
Engineering resins simulate a range of injection-moulded plastics, helping engineers and product designers conceptualize, prototype, test, and manufacture final products.
Grey resin is the tool of choice for general purpose prototyping with the Form 2. This resin is specially engineered for fine detail and it has an extremely high tensile strength, similar to that of cured ABS plastic. As a result, it’s a great choice of resin for functional prototypes and it lends itself well to any model with moving parts.
These printed parts take on a stylish, neutral colour with a matte finish. The final colour is ideal for painting over (the grey acting as a primer) and because of this, many people use grey resin to print end product parts, in addition to prototypes.
Black resin from Formlabs is specially formulated for intricate parts with fine features, with support for print resolutions of just 25 microns. This resin is a popular choice for production quality parts, especially those that won’t be seen, such as gear mechanisms.
We can also print in many other resins in 'open mode' with our Form 2 which allows us to customize a part depending on the customer requirements. If you unsure as to which resin to use we can identify the right resin choice for your product.
We can offer a large range of resins such as Customisable Colour Pigmented Resin, Clear Resin, Durable Resin, Tough Resin, Flexible Resin, Rigid Resin, Castable Resin, High Temp Resin and even Dental Resin which is safe for the human body. We can provide full material spec sheets for any of our resins for your design process.
What do I need to send when ordering
Use any computer-aided design (CAD) software to design your model, and export it in a 3D printable file format. We accept .stl mainly but if you're unsure we can create an .stl from step files or even file straight from Solidworks. If you're not CAD minded you can use our in-house design facility which can create your models for you from even the most basic dimensions.
I've placed my order, what happens next?
As with all 3D printing processes, SLA starts with a three-dimensional model, the mathematical representation of any three-dimensional surface. This can be created using computer-aided design (CAD) software or developed from 3D scan data. The design is then exported as an .STL or .OBJ file that’s readable by our software that prepares the file for our 3D printer.
Our SLA printer includes software to specify printing settings and slice the digital model into layers for printing. Adjustable printing settings include orientation, support structures, layer height, and material. Once setup is complete, the software sends the instructions to the printer via a wireless connection.
After a quick confirmation of the correct setup, the printing process begins and the machine can run unattended until the print is complete. Our printers have a cartridge based system so that the material is automatically refilled by the machine when it needs to add more material for larger prints.
Once the print process is completed, the build platform can be removed from the printer. The printed parts are then placed in our automated cleaning machine which rinses the parts in isopropyl alcohol (IPA) to remove any uncured resin from their surface.
Once this has been completed we Post-cure your parts for the best material properties. Parts printed using functional resins require post-curing to finalize the polymerization process and stabilize mechanical properties.
After drying and curing, supports can be easily removed from the parts with flush cutters, and the remaining support marks sanded away for a clean finish. SLA parts can easily be post-processed for specific applications or the required finish, including machining, priming, painting, and assembling printed parts.
Clear: Transparency, polishes to near optical clarity, great for internal channels and working with light.
White: Neutral and matte tone, slight translucency when thin. Works well for sanding, and provides a great base colour for painting prints.
Grey: Neutral and matte tone, great for showing off surface finish and for printing small, accurate features, photographs easily, High tensile strength, similar to ABS, Can be painted as grey acting as a primer
Black: Highly pigmented, our most opaque, high detail resin. Matte surfaces, great for printing small, intricate features.
Colour Base: White with an opaque matt finish. To be coloured with pigments to custom colour your parts
Flexible: Simulates an 80A durometer rubber. Choose for impact resistance and compression, great for ergonomic soft-touch grips, silicone-like Smartphone cases, 'O' rings and gaskets
Tough: Simulates ABS plastic. Choose for applications that will undergo high stress and strain. Great for functional prototyping of assemblies, machining, snap-fits and living hinges.
High Temp: Has an HDT of 289 °C @ 0.45 MPa. Choose for static applications that will experience high temperatures, including moldmaking processes such as thermoforming, vulcanization, and electronics encapsulation.
Rigid; Reinforced with glass to create a durable material with outstanding stiffness. 3D printing thin walls and features. manufacturing turbines and fan blades, jigs, fixtures, manifolds, electrical casings, and automotive housings. A polished finish. Off-white colour. Highly resistant to deformation over time.
Durable: Use to prototype models that will eventually be made from polypropylene (PP) or high density polyethylene (HDPE). Consider using where high elongation, deformation, and/or impact resistance are required.
Castable: Developed for clean burn out and high detail. Choose for direct investment casting, resin is blue in colour, and slightly softer than standard resins before post-curing.
Dental SG: Designed to directly print surgical and pilot drill guides. Class 1 biocompatible resin (EN-ISO 10993-1:2009/AC:2010, USP Class VI)
Dental LT: high-performance and high-accuracy Class IIa biocompatible resin for dental professionals. 3D print splints, retainers, and other custom-fit orthodontic appliances for patient wear.
Dental Model: Highly accurate and specifically formulated for printing crown and bridge models with removable dies.Request a quote