Additive Manufacturing of Photopolymers using the Texas Instruments DLP Lightcrafter

摘要

The use of the Texas Instruments DLP~® LightCrafter~(TM) 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 50um, 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 three-dimensional 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.