Stereolithography (SLA) 3D printing technology
Stereolithography is a 3d printing method that can be used to implement your projects that involve 3D printing of objects. Although this method is the oldest one in history of 3D printing it’s still being used nowadays. The idea and application of this method are amazing. Whether you are a mechanical engineer, who needs to verify if the part can fit to your design, or creative person who wants to make a plastic prototype of new coming project, Stereolithography can help you to turn your models into a real 3D printed object.
This method was patented by Charles Hull, co-founder of 3D system in 1986. The process of printing involves a uniquely designed 3D printing machine called a stereolithograph apparatus (SLA), which converts liquid plastic into solid 3D objects.
Most printing techniques require computer aid design (CAD) file to process the object. This file contains information about dimensional representation of an object. CAD file must be converted into a format that a printing machine can understand. There is Standard Tessellation Language (STL) format that is commonly used for stereolithography, as well as for other additive manufacturing processes. The whole process consists of consequent printing of layer by layer hence STL file that printing machine uses should have the information for each layer.
SLA printing machines don’t work as usual desktop printers which extrude some amount of ink to the surface. SLA 3D printers work with excess of liquid plastic that after some time hardens and forms into solid object. Parts built with 3D printers type like this usually have smooth surfaces but its quality very depends on the quality of SLA machine used.
The process of printing includes several steps. It starts from creation of 3D model in CAD program, special piece of software processes the CAD model and generates STL file that contains information for each layer. There could be up to ten layers per each millimeter. Then SLA machine exposes the liquid plastic and laser starts to form the layer of the item.
After plastic hardens a platform of the printer drops down in the tank a fraction of a millimeter and laser forms the next layer until printing is completed. Once all layers are printed the object needs to be rinsed with a solvent and then placed in an ultraviolet oven to finish processing.
The time required to print an object depends on size of SLA 3d printers used. Small items can be printed within 6-8 hours with small printing machine, big items can be several meters in three dimensions and printing time can be up to several days long.
Stereolithography is widely used in prototyping as it doesn’t require too much time to produce an object and cost is relatively cheap comparing to other means of prototyping. Although this 3d printing method is rarely used for printing of the final product.
Although Stereolithography is considered to be the oldest 3D printing technology many companies still use it to create prototypes of their projects. 3D Systems Inc., the company that started to use this method for prototyping, sells SLA machines to businesses and manufactures.
Home 3D printers usually use additive manufacturing(AM) processes and not stereolithography to produce 3D objects. But anyone interested in this technology can purchase SLA machine for home use and try this process on their own.
For those who are interested in DIY experience, it can be useful to look at the following tutorial on Instructables.