Additive manufacturing of photopolymers using the Texas Instruments DLP lightcrafter

The use of the Texas Instruments DLP® LightCrafterTM as a compact module in lithography-based additive manufacturing technologies (AMT) is discussed in this paper. For this purpose the light engine is placed underneath a transparent vat which is coated with a PTFE-film and filled with photosensitive resin. By loading an appropriate bitmap into the light engine, the resin can be exposed selectively to obtain a photopolymerized layer. To integrate the device into the building process, a configurable I/O trigger is required since the loaded bitmap should be exposed only in a certain period (exposure time). By stacking up the individual layers with a typical layer thickness between 25 and 50μm, a three-dimensional part is built up. The current setup of the used digital LEDs in combination with a customized optical projection system ensures a spatial and temporal homogeneity of the intensity at the build platform, which is significantly better than with traditionally used engines. It could be shown that this system can fabricate threedimensional parts with a resolution < 40μm in x-y plane and 15μm in z-axis. Additionally, mechanical properties (e.g. bending strength) were measured and potential anisotropies, which might be caused by the layered manufacturing process, were assessed. Ceramic-filled polymers were also used and the necessary post-processing steps like the removal of the polymer phase after structuring and the final sintering step to obtain fully dense ceramic parts are discussed.