Stereolithography (SLA) 3D Printing
When you need a part printed yesterday and delivered right now, Stereolithography is what you want to be looking at. It’s a technology that produces great-looking models with impeccable surface quality in no time.
SLA 3D Printing
Ideas too large for a print bed?
Stereolithography, more commonly referred to as SLA 3D printing, is one of the most popular and widespread techniques in the world of additive manufacturing. It works by using a high-powered laser to harden liquid resin that is contained in a reservoir to create the desired 3D shape. In a nutshell, this process converts photosensitive liquid into 3D solid plastics in a layer-by-layer fashion using a low-power laser and photo polymerization.
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Low Volume Production
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Mock-up of actual product
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Visual prototypes
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Master pattern for Vacuum Casting
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Sculpture master patterns
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Crown & bridge model
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Clear aligners models
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Technical Specification
Standard lead time
- Minimum of 3 working days, depending on part size, number of components and finishing degrees
Maximum build dimensions
- 600 x 600 x 400 mm dimensions are unlimited as components may be composed of several sub-parts
Dimensional Accuracy
- ±0.15% (with a lower limit of ± 0.2 mm)
Minimum Wall Thickness
- Minimum allowable thickness would be 1 - 3 mm (depending on part dimensions)
Surface Structure
- Unfinished parts typically have visible building layers on the surface but post-production finishes can achieve different effects, from high glosses to coarse textures.
- Stereolithography parts can be sandblasted, painted, varnished, covered, and coated.
Material
White ABS
– PP like ABS Resin – Stiff and Strong Resin
– Photo-cured polymer has good dimensional accuracy and a smooth surface finish.
– PC like Clear Resin
– Translucent (60-70% transparency) material, which after post-processing can be made transparent (up to 95% transparency).
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Applications of Stereolithography (SLA) 3D Printing
Concept Models
The speed, accuracy, and great surface finish of SLA parts lets product developers create physical snapshots of their designs through the iterative process.
Rapid Prototyping
SLA can be used to create fully-functional prototypes, with materials that can simulate polypropylene, polycarbonate, ABS, and rigid composites.
Direct Digital Manufacturing
The high accuracy and consistency of SLA makes it an ideal way to build large quantities of discrete or customized parts.
Benefits of SLA 3D Printing
Print parts in high resolution and a smooth surface finish directly out the machine
Printed parts can be easily cleaned, sanded, polished and painted
Create accurate parts with repeatable dimensions. Material properties include heat resistance, biocompatibility- matching properties of engineering plastics
Ideal for functional applications such as engineering assemblies and jewelry casting
SLA Design Guidelines
Wall Tickness
In 3D Printing, wall thickness refers to the distance between one surface of your part and the opposite sheer surface. A part made using Stereolithography has a minimum wall thickness that is dependent on its overall size. As a guide, we suggest that you increase your wall thickness whenever you scale up your design to a larger size. Small objects, where the sum of dimensions is below 200 mm, need a minimum wall thickness of 1 mm. For medium-sized parts where the sum of the x, y, and z dimensions is between 200 mm and 400 mm, the minimum wall thickness is 2 mm. For larger parts, a wall thickness of 3 mm is a must.
Surface Quality and Orientation
Many of the characteristics of your 3D print will depend on the Stereolithography process. Because your part will be printed layer-by-layer, the orientation on the build platform will influence the surface quality and strength. Above, you can see two examples of the same part built in two different orientations.
The horizontally-printed part clearly shows evidence of the “staircase” effect of the printing process. Its surface will be similar to that of a topographic map. If the part is printed vertically, the surface quality will be better.
Think about which surface needs to have the best finish and choose the orientation accordingly when printing.
Hollowing
If possible, try to hollow out your part. In doing so you can avoid extra charges and shrinkage issues in the thicker sections. You can read about the appropriate wall strength recommendations in the section on wall thickness above.
When you hollow out your part, our production team will need to integrate one or more drainage or escape holes. Usually, these are placed at the lowest point(s) of your part once it has been oriented and positioned on the build platform.
These holes ensure that the pressure of the liquid resin inside and outside your part remains at the same level. This prevents the deformation of your design. Uneven pressure can be compared to a glass of water filled to the brim: the liquid bulges at the edges and as a result, the laser scans too much material, causing your part to deform.
Secondly, the holes will be used to remove the excess resin inside the part once the printing process has been finished and your part has been removed from the 3D printer. Your part can then be emptied, cleaned and cured in a UV oven to achieve optimal strength. If the drainage holes weren’t present, the liquid resin would stay trapped.
As the position of the drainage holes depends on the orientation, our specialized production team need to decide where to place the holes. Wherever possible they will place the holes on the surface which is the least visible or that is easier to fill afterward.
You can, of course, include holes in your design yourself if you want them to be in a specific location. However, it’s possible that our team may need to add extra holes depending on the print orientation.
Some hollow parts require support material on the inside to reinforce the structure. This support structure might not be removed if we cannot access it. For more information take a look at the Internal Support section further down below.
Support
The process of Stereolithography takes place in a tank with liquid resin. Therefore, parts need to be attached to the supporting platform to prevent them from floating away. This attachment is referred to as “support” and is required for all parts built using Stereolithography. In addition to keeping the part in place, supports also make it possible to construct overhanging elements.
External Support
To keep your part in place and prevent it from collapsing while being printed, it needs to be supported if it has sections narrower than 30°. For example, in the illustration, the bottom of the part needs to be supported because it is narrower than 30°. The rest of the design does not need extra support because it is wider than 30°.
Internal Support
The 30° rule also applies to the inside of the part. Any part with an interior section narrower than 30° needs to be supported. For example, in the illustration, the top part of the interior needs to be supported to prevent it from collapsing during the printing process. As you might suspect, the removal of internal supports is far more difficult than that of external supports because they are usually less accessible by hand. There are usually two methods for the removal of internal support. The easiest option is to split your hollow design into two parts. This option will result in a design with an obvious seam or so-called split line. The other option is to include a large hole so that the inside can be accessed. This option is not possible with very complex forms, so in that case, multiple holes need to be implemented. The diameter of the hole should be 10 mm or higher. The larger the hole(s), the better the chances that the internal support can be successfully removed.
Embossed and Engraved Details
For engraved text or surface details, we recommend letters with a minimum line thickness of 0.5 mm and a depth of 0.5 mm. For an embossed text and surface details, we recommend letters that have a line thickness of at least 0.5 mm and a depth of at least 0.5 mm.
File requirements
We accept file formats such as STL, 3DS, 3DM, OBJ, STP, SKP, SLDPRT, STEP, IGES, Parasolid.
Mail your design file to sales@voxelwerks.com with the above-mentioned format.
Have any Questions or Suggestions? We would love to help you!
How Does Stereolithography (SLA) Work?
Stereolithography is a laser-based technology that uses a UV-sensitive liquid resin. A UV laser beam scans the surface of the resin and selectively hardens the material corresponding to a cross-section of the product, building the 3D part from the bottom to the top. The required supports for overhangs and cavities are automatically generated, and later manually removed.
