What is SLA 3D Printing?Stereolithography (SLA) is an additive manufacturing process that belongs to the vat photopolymerization family. Also known as resin 3D printing , there are three main 3D printing technologies associated with vat polymerization: SLA, DLP, and LCD. The three technologies all use a light source to cure a photopolymer reason but with the following differences: Stereolithography (SLA) uses UV lasers as a light source to selectively cure a polymer resin.
SLA is one of the most widely used vat photopolymerization technologies. It is used to create objects by selectively curing a polymer resin, layer by layer, using an ultraviolet (UV) laser beam. The materials used in SLA are photosensitive thermoset polymers that come in a liquid form. Patented in 1986, SLA was the first 3D printing technology. And even today, SLA is still the most cost-effective 3D printing technology available when parts of very high accuracy or smooth surface finish are needed. Best results are achieved when the designer takes advantage of the benefits and limitations of the manufacturing process. |
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What are the characteristics of SLA 3D printing?
The main characteristics of SLA 3D printing are the necessary support structure, curling and layer adhesion.
Support structure
A support structure is always required in SLA. Support structures are printed in the same material as the part and must be manually removed after printing. The orientation of the part determines the location and amount of support. It is recommended that the part is oriented so that so visually critical surfaces do not come in contact with the support structures.
Bottom-up and top-down SLA printers use support differently:
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Top-down SLA printers: S upport requirements are similar to those for FDM . They are needed to accurately print overhangs and bridges (the critical overhang angle is usually 30o). The part can be oriented in any position, and they are usually printed flat, to minimize the amount of support and the total number of layers.
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Bottom-up SLA printers: Support requirements can be more complex. Overhangs and bridges must still be supported, but minimizing the cross-sectional area of each layer is the most crucial criterion: the forces applied to the part during the peeling step may cause it to detach from the build platform. These forces are proportional to the cross-sectional area of each layer. For this reason, parts are oriented at an angle and the reduction of support is not a primary concern.
What materials are used for SLA printing?
SLA materials come in the form of liquid resins, which can be chosen based on the end use of the part—for example, thermal resistance properties, a smooth surface finish or abrasion resistant. As such, the price of the resin varies greatly, from about $50 per liter for the standard material, upwards to $400 per liter for specialty materials, such as the castable or dental resin. Industrial systems offer a wider range of materials than desktop SLA printers, that give the designer a closer control over the mechanical properties of the printed part.
SLA materials (thermosets) are more brittle than the materials produced with FDM or SLS (thermoplastics) and for this reason SLA parts are not usually used for functional prototypes that will undertake significant loading. Advances in materials may change this in the near future.
The following table summarizes the advantages and disadvantages of the most commonly used resins.
What are the advantages of SLA 3D printing?
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SLA can produce parts with very high dimensional accuracy and with intricate details.
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SLA parts have a very smooth surface finish, making them ideal for visual prototypes.
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Speciality SLA materials are available, such as clear, flexible and castable resins.
What are the disadvantages of SLA 3D printing?
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SLA parts are generally brittle and not suitable for functional prototypes.
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The mechanical properties and visual appearance of SLA parts will degrade over time when the parts are exposed to sunlight.
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Support structures are always required and post-processing is necessary to remove the visual marks left on the SLA part.
SLA best practices
Is SLA 3D printing right for your part or project? These are the rules of thumb:
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SLA 3D printing is best suited for producing visual prototypes with very smooth surfaces and very fine details from a range of thermoset materials.
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Desktop SLA is ideal for manufacturing small injection-molded-like parts at an affordable price. Think "smaller-than-a-fist".
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Industrial SLA machines can produce very large parts, as big as 1500 x 750 x 500mm). Want to find out more? Read our complete guide to 3D printing.
SLA best practices
Is SLA 3D printing right for your part or project? These are the rules of thumb:
-
SLA 3D printing is best suited for producing visual prototypes with very smooth surfaces and very fine details from a range of thermoset materials.
-
Desktop SLA is ideal for manufacturing small injection-molded-like parts at an affordable price. Think "smaller-than-a-fist".
-
Industrial SLA machines can produce very large parts, as big as 1500 x 750 x 500mm). Want to find out more? Read our complete guide to 3D printing.
JTC Case Study
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