DLP 3D printers use a vat or tank of liquid resin that cures as it is hit by UV light from a DLP projector. This light activates the photosensitive particles of the resin, causing them to bond and harden and resulting in a solid 3D-printed structure.
The vat usually uses a flat platform facing upside down, which moves slowly up as each layer of the object is being created. Once a layer has been formed and moved up, it makes way for a new liquid layer to take form. These layers of hardened resin complete a larger structure that takes shape as the light from the UV light engine flashes each layer.
Unlike a laser method of hardening, which happens as several tiny points of light are bounced off the liquid layers, DLP 3D-printing can flash an entire layer at once, curing faster.
The platform for the DLP 3D printer may also be right-side up, depending on the printer.
The curing of the object in the vat is just the first step in finishing a 3D build, however. Since the object is often created with support structures in place in the platform, this extra material must be cut away or sanded off to create a smooth surface. Additional curing and eventually rinsing of the resin residue must happen before the fully cured product can be put into use.
DLP creates a trade-off between resolution and print area, since the build area is the same as the size of the projected image: When resolution increases, the image becomes smaller.
This can be overcome by stacking several projectors together and stitching the images, or by moving the resin tank or the projector to achieve a larger area with high resolution.
The overall quality of a 3D-printer depends on the light source: the DLP projector. A high-quality projector will ensure:
- A uniform print across the whole build area thanks to a high uniformity of the image
- A high throughput enabled by a high output power
- A high resolution thanks to quality optics and high contrast values
- Repeatability from print to print because of the overall reliability of the projector and a stable output power.