DLP UV Exposure
DLP UV Exposure / DLP 3D Printing solutions use ultra-violet light, spatially modulated by the DLP chip, to expose and cure successive layers of material to produce either a 3-D physical objects or precise curing of epoxies or other UV-sensitive materials. For example, in 3D Printing, an object is specified by a 3D Computer Aided Design (CAD) model. Rendering software transforms the virtual 3D model into a series of layers, or exposures, suitable for printing the object.
With this technology, printing parts of a material can be done in a single process flow. 3D printers are becoming more affordable for medium and small scale businesses in which rapid prototyping is brought all the way into the office, no longer requiring manufacturing floor space.
Two common methods for DLP 3D printing are digital exposure and laser sintering. The high level principles for incorporating DLP technology into a 3D printing solution can be applied to both methods, but digital exposure is represented in the system block diagram.
In DLP 3D printing systems each layer of the object, the UV light image from the DLP® Digital Micromirror Device (DMD) creates a pattern which hardens the polymer resin where it is exposed to the light. The 3D object is constructed by laying down successive thin layers (or cross sections) of an ultraviolet (UV) curable liquid photopolymer resin.The cross-section pattern is produced by the individual mirrors that correspond to each pixel on the current layer. Either binary or grey-scale patterns can be used. Each pattern projects through an imaging lens onto the surface of the UV curable liquid photopolymer resin, curing or hardening it where the pixels are on. As depicted in the diagram, one resin is the build material and the second is material to support overhanging features and thin vertical walls during construction. The support material is later removed by heat or dissolved with a solvent or water.
Layers fuse together automatically through the polymer bonds. The process repeats one layer at a time until the model is built. Cure rates are possible under 0.2 seconds per layer. Layer thickness typically ranges from 1um to 250um based upon the resin and wavelength of the UV light used. More detailed images require more discrete cross-sections to assume the continuous smooth surface effect of the resulting object.
Alternative methods use a light-source with a scanning mirror to individually cure a specific area. The linear scanning method is slower and tends to result in less precise printing results.
The diagram shows a DLP chipset, which includes the DMD, and a DMD Controller chip, plus a DMD Analog Control chip (depending on the specific DLP chipset). DLP chipsets are available with different DMD sizes, pixel pitches, resolutions, and other specifications. DLP also offers devices targeted for use with UV light. The best choice for a DLP chipset may depend on the desired object feature size, patterning speed and necessary wavelengths to cure the resin.
- Expose an entire layer in one shot with pattern rates up to 32 kHz
- Improved throughput and eliminate need for masks or print plates
- Micromirror size (7, 10, 13 μm)
- Achieve micron-level features for high accuracy
- Optically efficient from 365 nm to 2500 nm
- Cure a wide range of photo-polymers and resins