How Stereolithography 3D Printing Works
Stereolithography (SLA) is one of the most popular and widespread techniques in additive manufacturing and 3D printing. But how exactly does this technology work to turn 3D digital designs into physical objects? In this comprehensive guide, we break down the components, processes, and applications of stereolithography 3D printing.
Table of contents
· An Overview of Stereolithography
· How Does an SLA 3D Printer Work?
∘ Liquid Photopolymer Resin
∘ Moveable Build Platform
∘ High-Powered UV Laser
∘ Computer Interface
· Step-By-Step SLA 3D Printing Process
∘ Working Upside Down
· Benefits of Stereolithography 3D Printing
· Closing Thoughts
An Overview of Stereolithography
Stereolithography printing, commonly abbreviated as SLA printing, belongs to the vat photopolymerisation family of 3D printing technologies. It is considered one of the oldest additive manufacturing techniques, with a history tracing back to the 1980s.
In a nutshell, SLA printing converts liquid photopolymer resin into 3D solid plastic objects in a layer-by-layer fashion using an ultraviolet (UV) laser and photopolymerization. The laser precisely traces out the object cross-section on the resin surface, causing the resin to solidify.
Along with fused deposition modeling (FDM) and selective laser sintering (SLS), SLA is one of the three primary technologies used in most 3D printing today. It is valued for its excellent surface finish, fine details, smooth textures, and mechanical properties. Common applications include prototypes, end-use parts, patterns, tooling components, and more.
How Does an SLA 3D Printer Work?
Now that we know what SLA 3D printing broadly entails, let’s look at the key components of an SLA printer and how they operate:
Liquid Photopolymer Resin
This clear and liquid plastic material starts off in liquid resin form. It is contained within the resin tank and sensitively reacts to UV light. Popular resins used include epoxy, acrylic, and vinyl-based formulations. The resin must match the printer specifications.
Moveable Build Platform
This platform is first lowered into the tank where it remains submerged in the liquid resin. The 3D printed object is built layer-by-layer on the platform. It can smoothly move up and down allowing fresh layers of liquid resin to flow beneath.
High-Powered UV Laser
The laser beam traces out each layer’s cross section onto the resin surface based on coordinates provided by the software commands. As soon as the laser makes contact, the liquid resin solidifies through a process called photopolymerization.
Computer Interface
Specialized software slices the 3D model into layers and generates the necessary laser paths to trace out each layer. The interface manages the laser controls and the build platform movement in a synchronized manner.
Step-By-Step SLA 3D Printing Process
From CAD to Reality: The step-by-step journey of transforming 3D CAD data into a physical object using the precision of stereolithography.
Now let’s go through what actually happens, step-by-step, in an SLA 3D print:
- 3D Model Creation: The object is designed on CAD software as a digital 3D model file (STL format).
- Slicing and Hatching: Software slices the model into layers and hatches the laser tracing patterns for each layer.
- Build Platform Lowers: The platform slowly immerses into the liquid resin tank.
- First Layer: The UV laser beam traces the pattern for the first layer based on software instructions. The photosensitive resin solidifies.
- Platform Rises: The platform lifts up slightly, allowing fresh liquid resin to flow beneath the solidified layer.
- Repeat Layers: Steps 4 and 5 repeat until full object is built layer-by-layer from bottom up.
- Part Removal: Constructed part is removed, rinsed, and cured further in UV light.
- Post Processing: Support structures are removed and model can be sanded, painted, or otherwise post-processed if needed.
And voila, your 3D printed part is complete! SLA makes it possible to create highly accurate and smooth parts with immense detail suitable for endless applications.
Working Upside Down
An interesting point about SLA printers is that most work in an upside down configuration. This means the laser draws upwards onto the build platform starting from below. This inverted orientation prevents the liquid resin from dripping through layers as they form and avoids trapped heat from the photopolymerization process. After every laser tracing, the platform lifts allowing resin to flow underneath.
Video Source; Formlabs
Benefits of Stereolithography 3D Printing
Diagrams depicting the components and laser scanning process involved in stereolithography 3D printing technology.
Now that the fundamentals are clear, what makes SLA such a valued 3D printing technology? What advantages does it offer over other methods?
Here are some of the top benefits provided by stereolithography printing:
- Excellent Surface Finish — The layer resolution can reach as high as 25 microns providing mirror-like shiny and smooth finishes. The laser precisely cures each voxel (3D pixel) of the photosensitive resin.
- Captures Intricate Details — Due to the laser accuracy, find details like edges, logos, and small text can be captured clearly in the print.
- Variety of Resin Properties — Based on factors like flexibility, toughness, heat resistance, bio-compatibility, clarity, etc. different resin formulations can be picked.
- Quick Printing Speeds — SLA printers can work rapidly since an entire layer is cured in one laser pass rather than tracing contiguous toolpaths.
- Supports Complex Geometries — The bottom-up additive approach allows even convoluted shapes with overhangs and undercuts to be successfully printed.
As you can see, stereolithography brings together precision, surface quality, application versatility and production speeds — making it a staple in professional 3D printing.
Closing Thoughts
SLA technology provides an efficient method to convert digital 3D models into high-fidelity plastic parts using photosensitive liquid resin and laser-based additive manufacturing. Its layered photopolymerization technique facilitated by laser beam tracing enables intricate shapes to be created with smooth finish and exceptional accuracy.
Understanding the full workings of stereolithography 3D printing — from its components to processes and benefits — helps unlock its potential for your applications. As the technology continues advancing, the capabilities and material choices will only continue expanding.
So next time you have a complex high-precision part to manufacture, consider taking advantage of all that industrial-grade SLA 3D printing has to offer!
This post is originally published at 3dprintjunction.com
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