Stereolithography (SLA) 3D printing is an additive manufacturing process. SLA falls under the category of VAT polymerization in this process, a special laser light is used which solidifies the photosensitive resin after coming in contact with it.
Objects printed by Stereolithography (SLA) are of exceptional quality, they have a smooth finish and all the printed features are clearly visible with extreme details.
Components of SLA 3D printer
- Laser Source – It transmits the UV laser.
- UV Curable photopolymer liquid or resin or Liquid plastic.
- The perforated Table or Build Platform moves vertically up and down into the tank.
- VAT or the resin chamber is the container-like structure where the resin is stored.
- Recoater blade – It evenly redistributed the resin whenever the layer gets printed.
- Reflecting mirror which manages the laser beam through Galven motor system.
- Outer covering – Dark-colored outer covering gives the printing object isolation from the outer environment and its dark color prevents excessive light from entering the print area.
- UV Oven – It is set at a predetermined temperature by using this the printed object gets even harder.
Working of Stereolithography (SLA) 3D printer
CAD file is converted to STL file type which can be interpreted by the 3D printer. STL file has got all layer by layer instructions from layer height to what is to be printed on that particular layer. Through this STL file, the SLA printer gets all the instructions.
Now Laser source emits the UV laser which strikes the reflecting mirror, Reflecting mirror is controlled by the Galven motor system which decides the path of the UV laser beam as instructed by the STL file.
This laser beam which is bounced from the reflecting mirror strikes the resin which solidifies as soon as it comes into its contact, now this beam systematically moves on the entire layer, the first layer solidifies directly on the build platform which is usually the support structure.
As soon as the layer is imaged on the resin surface through the laser beam an elevator system shifts the build platform down to one layer height and the recoater blade redistributes the resins for the next layer. The process is repeated layer by layer until the Object is finally complete.
After the print is complete the printed object is carefully removed from the build platform, it can easily be done with the help of the scraper blade and all the excess resin removed from it along with the supporting structures. After that the printed object is baked inside the UV oven it makes the object more stable.
Precautions to take while using SLA printer.
Human skin is sensitive to some resins it is advised always to use clovers and cover your workstation with some plastic wrap, direct contact with the resins can also lead to allergies in some cases.
Since the Resins are sensitive to the UV light it is instructed to not print in the direct sunlight, doing so can result in poor print quality and definition so it is best to print in some dark place or a place where there is no sunlight
Ensure the room or the workstation in which the machine is printing is well ventilated as fumes from the resins while printing can also irritate some individuals.
Part orientation cross-section of all the layers with the support structure should be minimum there are different tools available that ensure that no support structures are present on the selected surface which reduces the contact of the product with the support structure and also ensures supports are in contact only with the layers where minimum post-processing is required.
Advantages of Stereolithography (SLA) IN printing
SLA 3D printing is used in various industries from healthcare, manufacturing, and dental due to its fine build capabilities and ability to function with different materials, lots of customizable hearing aids are also made with the help of SLA 3D printers.
SLA 3D printing is ideal for injection mold prototyping because printed objects have a very smooth surface, which makes them the best choice, and products made from these are of superior quality and finish.
Printed objects have high dimensional accuracy, and fine details This is possible because of the small laser spot size and small layer height which gives higher precision to each layer being printed.
SLA prints create a chemical bond that needs much more force to break. In FDM printing printed parts break easily along the print lines which makes SLA prints strong when compared to the FDM prints
Disadvantages of SLA printing
Parts produced with SLA are brittle and can not be used at places of load-bearing or functional parts hence the technology is typically used for prototyping only. Excessive load can break the prints and printing functional parts can lead to wear and tear.
Direct sunlight also degrades the quality of the parts because the material used is UV sensitive and with the time detailing of the printed features becomes less distinct and the edges start to erode.
SLA printing mostly requires support while printing, finalising the product requires the supports to be removed and give the finishing touch at those places, all this adds to the cost and time of printing which makes it costlier than FDM printing.
Slow when compared to DLP (Digital Light Processing) in which we use a bulb or a light source that covers the entire layer area at once and in SLA laser is used which slows the process.
Fun Facts about SLA printing
The average layer of SLA printing of 100 microns which can go as low as 25 microns which is much smaller than the FDA. Due to this SLA prints detailed objects with much accuracy.
If you don’t have a UV oven printed objects can be kept in sunlight for some time. This will make the print stable but don’t keep the objects in sun for too long it can damage the print also.
SLA printing technology was the first through which 3D objects were printed and was first introduced in Japan by Mr. Charles Hull in 1986 by 3DSystems INC.
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