SLA 3D Printing: Difference in Laser and DLP Light Pattern Generation
What makes the Titan 1 different from other SLA 3D printers?
But first, what is SLA 3D printing? SLA stands for stereolithography. In this method of additive manufacturing, a 3D printed object is built layer-by-layer using a liquid resin (photopolymer) that is cured using UV or visible light. What differentiates the Titan 1 from other SLA 3D printers, is that the Titan 1 uses Digital Light Processing (DLP) to shine light patterns via a projector. Many SLA 3D printers use a laser galvanometer to generate patterns.
Here’s a quick guide to everything you need to know about DLP and laser 3D printing.
DLP 3D Printing
A high resolution projector, light pattern powered by DLP technology, sits beneath the resin container and projects image slices to cure each layer. The projected image is just black and white as seen below. Since the resin is UV sensitive, the white areas of the projected image will direct UV and purple light to the areas require curing.
This method is quite simple when compared to the stunning resolution and details that it produces. The projector remains completely stationary during printing (and it is important that it doesn’t move or else the layers won’t align properly), which means there are few moving parts and little machine maintenance required. For Kudo3D’s Titan 1 and Titan 2, the only moving part is the stepper motor that lifts the build platform as the model grows after each layer is cured.
(Image Source: http://m.iopscience.iop.org/1758-5090/6/1/015003/article)
A sliced layer that will be projected onto the resin container. From Pranav Pancha’s model of the Eiffel Tower (https://grabcad.com/library/eiffel-tower).
Laser 3D Printing
Laser based SLA 3D printing uses a laser to trace out the cross-sections of the model. Similar to fused deposition modeling (FDM) 3D printing, where each layer is deposited in a continuous stream of filament, the laser essentially “draws” the layer to be cured. The laser is focused using a set of lenses and then reflected off of two motorized scanning mirrors (galvanometer). The scanning mirror directs the precise laser beam at the reservoir of UV sensitive resin to cure the layer. Alternatively, some laser based SLA 3D printers move the laser directly using a XY stepper motor arrangement similar to those used in filament based printer.
(Image Source: http://biega.com/3d-printing.shtml )
Now that we know how each method works, let’s do a comparison.
SPEED AND ACCURACY
DLP 3D printing is very fast because it projects the profile of an entire layer at one time, turning 2-dimensional images into a 3D object. In comparison, lasers have to trace out the entire sliced profile line by line which takes a lot more time. Small inaccuracies are also likely to occur and can affect the structural strength and surface smoothness of the print.
RESOLUTION AND BUILD SIZE
The projector makes DLP 3D printing versatile. Depending on the resolution and size of the 3D model desired, DLP can be easily moved up or down to adjust for your customized settings. DLP 3D printers can produce details with much higher resolution than laser based SLA 3D printers. However, resolution depends on the projected pixel size. This means that higher resolutions are limited to smaller XY build area.
Laser 3D printing generally has a fixed laser spot size of about 300 um, while the DLP projector in the Titan 1 can be customized to print from 37 to 100 um. Tuning the laser spot size smaller will make the printing speed extremely slow. On the other hand, since lasers sweep a continuous path, they’re less likely to show surface “pixelization” artifacts the way a DLP 3D printer printed model will. The pixelization is usually more noticeable for large prints. Pixelization can be removed with anti-aliasing or pixel shifting.
Laser based SLA 3D printers require a number of moving parts in their design. XY motion is achieved via the use of two stepper motors to move the laser itself, or a galvanometer which rotates a mirror assembly to reflect a stationary laser’s light to the desired location. DLP 3D printers do not require any mechanical XY motion for photopolymer curing since projector illuminates the entire XY plane at once.
The Titan 1 and Titan2, with patented passive self-peeling technology, only require one stepping motor for Z-axis linear stage, eliminating the need for sliding or rotating tray mechanisms. This minimizes assembly complexity, maintenance, and wear on the machine.