Stereolithography is also known as 3D Layering and 3D Printing. Stereolithography is the process of turning CAD designs into real 3D objects in a matter of hours.
In the past, it could take days, weeks, or even months to prototype a part using conventional methods. The design would have to be done, then the tooling on the molds would need to be finished. Stereolithography goes straight from design to the prototype.
Stereolithography is a manufacturing process that uses a UV laser to create successive cross-sections of a 3D object within a vat of liquid photopolymer. A platform is placed on top of the vat filled with the polymer (an epoxy resin). Before the build begins, the platform is moved to a point just below the surface of the resin. As the solid state UV laser traces the layer in the polymer, the resin begins to cure; solidifying the part to be manufactured.
There are 4 main parts of the Stereolithography Machine:
- Liquid Photopolymer Tank: holds serveral gallons fo the clear, liquid plastic.
- Perforated Platform: the platform is immersed in the tank and can be moved up and down as the process is performed.
- Ultraviolet Laser: transorms the liquid polymer into the 3D object.
- Computer: controls the laser and movement of the platform during the printing process.
The photopolymer is sensitive to ultraviolet light, so when the laser passes through the polymer it hardens into each layer of the 3D object.
The Stereolithography process is basically performed in the following way:
- Create a 3D model with CAD software.
- Stereolithography software slices up CAD model into many layers; about 5-10 per millimeter.
- 3D printer (Stereolithography machine) “
- The platform drops down into the tank layer by layer until the model is completed.
Stereolithography is not a quick process. It can take few minutes per layer depending on the size and number of objects being created. Typically it can take anywhere from 6-12 hours to complete one run.
After designing your 3D object in the CAD software, it need to be modified to add supports to raise it off of the platform slightly. The SLA machine will render your object unattended. Once it is done, the platform is raised out of the polymer and your 3D models are rinsed in a solvent and baked in an ulta-violet oven to completely cure the plastic.
What can you make with stereolithography?
If you can design it with CAD, you can most likely produce it with stereolithography. You may need to add internal bracing to the 3D object so it will not collapse during the printing or curing processes. Once your object is made, you can actually test it out in an application, such as parts that fit on a motor or other machine. Of course, these parts won’t be used on a real machine, but they can accurately display if the parts will fit or not.
|Stereolithography is not cheap. The photopolymer plastic can cost hundreds of dollars per gallon. The SLA machines themselves cost hundreds of thousands of dollars. The machines have to be vented because of the fumes the polymers and solvents create. For these reasons you will usually only find stereolithography machines in large companies. |
Some companies do offer SLA services at hourly rates though. This allows smaller companies to take advantage of the great benefits of steolithography without having to purchase such expensive equipment.
These high costs are greatly offset by the turn-around time of making prototypes. Stereolithography is considerably faster than machining the test parts, and in today’s world, time is money.