Stereolithography (SLA)

What‘s SLA?

SLA is short for Stereolithography or Stereo lithography appearance. 

SLA is the earliest practical technology in rapid prototyping, which raw material is liquid photopolymer resin. At first, design the 3D model according to the CAD drawing, using discrete program to slice the model, design the scanning path, and the generated data will precisely control the movement of the laser scanner and the lifting table. With the help of scanner which controlled by the numerical system, the laser beam will be irradiated on the surface of liquid photopolymer resin through the design scanner path, and make one layer of resin solidified in the specified area. When the processing  of one layer is completed, a cross section of the parts is generated.  Then the lifting platform will be lowered for a certain distance, and the cured layer will be covered with another layer of liquid resin. And the scanning of second layer will be processed. The second solidified layer will be firmly bonded to the previous solidified layer. The 3D workpiece will be made out with the layer by layer superimposition. To obtain the required products, it still need some post-process after taken out from the resin. Such as curing, polishing, plating and painting etc. These post-process are very popular in 3D Printing.

What’s the advantage of SLA?

Reviewing all technologies in 3D printing, SLA technology should be the one with the longest developing time, the most mature technology, and the most widely used. The stereolithography system account for 60% to 70% of rapid prototyping equipment which was installed all of the world. The prototyping speed of SLA is very fast, and the working system is also stable. Compared with SLS, the precision of SLA is higher, which basically can reach micrometer level. For example, the highest accuracy can be 0.05mm. Of course, the precision might get effected if the model getting bigger. The finish quality of SLA is good, which is smooth and suit for some precise and fine parts. The SLA technology can also be used to print large size prototypes. At present, the largest SLA equipment on the market are capable to make prototypes near 2 meters. If your prototype is within 2 meters, then it can be printed by SLA directly.

SLA Product

What’s the advantage of SLA on technology level?

1.Repeat Creation of High Precision Components

When SLA printing different parts with same model, the accuracy of SLA is extremely high. Many industries choose SLA printing, as it can repeat creating high precision components. Compared with traditional machining, the precision of SLA is stand between standard machining and fine machining. Why SLA can repeat high precision parts? There are two reasons. First, when SLA printing, the heating resin tank and sealed construct environment can provide almost the same condition for each printing. Second, compared with the thermosetting technology of FDM which melting raw materials, SLA is using light, not heat. So the printing process is performed at the room temperature, and the printing parts will not get effected by the heat expansion and cold contraction.

2.Smooth Surface Finish

SAL printing is considered as the fine standard of smooth surface finish, which appearance can rival with the traditional machining, like CNC machining, plastic injection and extrusion. This surface quality of SLA is very suitable for the perfect manufacturing industry, which can help to reduce the time for the post-process. Because the parts can be performed with post-process easily, like polishing and coloring.  Instead, FDM products have clear and visible layers or lines, and SLS products have granular surface which comes from powder sintering.

SLA surface

SLS surface

FDM surface

3.Water-tightness

The printing of SLA is continuous, no matter producing geometric shape with rigid property or producing parts with inner passage. So SLA printing boast high watertightness, which is vital to project or manufacturing industry which have to control and predict air or liquid flow. Engineers and designer can use the watertightness of SLA to solve the challenge of air and liquid flow in the research of automotive and biology

The Limitation of SLA

1.Expensive Cost. The cost of SLA system is very expensive, and the cost of using and maintain is very high.

2.Strict Requirement. The system of SLA has strict requirement to the precise equipment which need to deal with the liquid, and it also has strict requirement to the working environment.

3.Difficulty for preservation. The SLA prototype is not good for long time preserving, as most of these parts are resin, which have many limitation on strength, rigidity and heat resistance. When the parts are exposed under sunshine, the mechanical properties and visual appearance will be decreased as the time goes on.

4.Limited available material. The available photopolymer resin of SLA prototype is limited. Besides, the ductility and strength of SLA prototype is not as good as CNC prototype, as the buckling position of SLA prototype might be broken easily. 

Regarding to above two limitation, which can be solved by choosing special material according to the character of the products. Our professional engineer will provide the satisfied solution according to the required parameters.

5.Support Structure needed. The SLA prototype will always need support structure, which need be removed after SLA process. This limitation can’t be avoided, as it’s caused by the process principle of SLA 3D printing. But we can reduce the support effect to the maximum. As our professional stuff can provide the best printing solution and the best design for the support structure.

Support Structure

Application area

SLA Printing is widely used in the product development, such as the automotive, medical, casting model, construction model, as well as the exhibition prototypes of concept, geometry or vision.