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Stereolithography enables the creation of 3D plastic prototypes. Photo by Maciej Frolow / Getty Images.Stereolithography, also referred to as 3D layering or 3D printing, allows for the rapid creation of solid, three-dimensional (3D) plastic objects directly from computer-aided design (CAD) files.
Whether you're a mechanical engineer checking the fit of a component or an inventor wanting to create a tangible prototype, stereolithography offers a quick and simple solution to transform CAD designs into actual objects.
3D printing stands as a prime example of the technological era we live in. In the past, creating a prototype could take months; now, rapid prototyping can be completed within hours, offering remarkable mechanical functionality.
Join us as we explore the stereolithography service center at PT CAM (Piedmont Triad Center for Advanced Manufacturing) to gain a deeper understanding of the process and see some real 3D models that this technology can create.
The Stereolithography Machine
Stereolithography machines operate using liquid plastic.
Mytour.comPT CAM utilizes a stereolithography machine from 3D Systems. This device consists of four key components:
- A tank filled with several gallons of liquid photopolymer, which is a transparent, liquid plastic.
- A perforated platform submerged in the tank, capable of moving up and down during the printing process.
- A UV laser, with some SLA printers using digital light processing technology as a UV light source.
- A computer that controls both the laser and the platform.
The photopolymer reacts to ultraviolet light; when the laser strikes the photopolymer, it solidifies. If you stand near the stereolithograph machine (SLA), you can actually observe the laser as it forms each layer.
SLA Materials
Primary materials include photosensitive polymers and support structures, which support overhanging features but are not part of post-processing. Specialized materials like high-heat deflection and high-temperature resins are designed to endure extreme heat, while flexible and durable resins are ideal for bending and flexing.
The Stereolithography Process
The platform sits in the photopolymer tank at the start of the printing process.The essence of SLA printing is a laser beam, meticulously controlled by a light-emitting device, which cures the polymer resin in the tank. Here's how the SLA printing process generally unfolds:
- Create a 3D model of your object using a CAD program.
- A software program slices your CAD model into thin layers — typically five to ten layers per millimeter.
- The 3D printer's laser "paints" one of these layers, solidifying the liquid plastic in the tank.
- The platform lowers by a fraction of a millimeter, and the ultraviolet laser hardens the next layer of resin over the previous one.
- This process continues, layer by layer, until your model is fully formed.
This isn't a particularly fast process. Depending on the size and number of objects, each layer may take one or two minutes to complete. A typical print might take anywhere from 6 to 12 hours. For larger objects, it could take several days (the maximum size for the relatively old machine shown is an object up to 10 inches, or 25 centimeters, in all dimensions).
The process begins by designing a 3D model of your object in a CAD program. This model is adjusted with supports to lift it slightly off the tray, along with any necessary internal bracing. The SLA printer then automatically renders the object, with no need for supervision during the build.
Once the process is finished, the SLA lifts the platform, and your 3D object is ready. For smaller objects, you can produce multiple copies at once, all sitting side by side on the tray.
The image below displays a tray after printing is completed, showcasing several identical objects produced in unison.
The platform at the end of a print cycle, pictured here with multiple identical objects.After the print run concludes, you rinse the objects in a solvent and then "bake" them in an ultraviolet oven to fully cure the plastic.
The ultraviolet "oven" used to complete the curing process for the finished objects.Benefits of Using SLA Technology
SLA technology presents numerous advantages over traditional manufacturing techniques like injection molding and fused deposition modeling. It can create parts with smooth finishes, intricate details, and complex geometries, all without needing multiple tools or molds.
What You Can Create with Stereolithography
A manifold for an engine, created at PT CAM.
Mytour.comStereolithography enables the creation of virtually any 3D shape imaginable. If you can design it in a CAD program, it's likely feasible to build. The only limitation is ensuring structural integrity during the printing process. Sometimes, internal supports must be added to prevent the design from collapsing during printing or curing.
The image on this page displays a typical object created at PT CAM. The piece is lightweight yet has the durability of polystyrene plastic. Since it can be mounted and drilled, it’s ready for real-world testing.
For instance, a chair manufacturer might create various armrest designs using stereolithography and then test them on actual chairs to assess comfort and fit.
Costs of Stereolithography
Stereolithography can be costly. The machines were once priced over $250,000, and while some are now available for tens of thousands of dollars, desktop SLA printers can be found at a significantly lower price. Additionally, the machines require proper ventilation due to the fumes produced by the polymer and solvents.
The photopolymer used in the process is also quite expensive. For example, CibaTool SL5170 resin, a commonly used photopolymer in stereolithography, cost about $800 per gallon when we visited PT CAM. Due to these costs, professional stereolithography machines are typically only found in large companies.
Service bureaus make it possible for smaller businesses and individuals to take advantage of stereolithography. While it's still not inexpensive, it’s far more cost-effective than investing in your own SLA system, resin, or paying for machining.
A heartfelt thanks to Joel Leonard, Jerry Watkins, and Steve Oneyear for their invaluable assistance in the creation of this article!
