Engineering - Hardware results
The principal setup of the 3D printer is shown in Figure 1. Its hardware components are explained in the following section.
For details on how the 3D printer was built, please see the printer documentation attached to the end of the Engineering Site. Besides using only commercially available parts for building the printer, several parts for special purposes were self-manufactured by generating 3D models and using commercially available 3D printers to manufacture these parts. This includes brackets between the aluminum profiles for increasing stability as well as the holders for the linear guiding and the stepper motor. Pictures of these parts can be seen in Figure 2.
|Figure 2 - Additional parts that were designed and printed for the manufacturing of the 3D printer|
At first, the wavelength spectrum of the Beamer lamp was investigated. The light spectrum can be seen in Figure 3. It shows a local maximum at approximately 410 nm. Due to the fact that nearly no intensity is measured at wavelengths below this value and absolutely no intensity below 380 nm, a wavelength from the visible spectrum is used to provide any radiation for hardening the resin. The local maximum at 410 nm was chosen as it is the most near-UV local maximum in the whole spectrum providing a high radiation intensity. As a consequence of this choice, a light-shielding or light-reducing case around the printer is necessary to prevent polymerization of the resin apart from 3D printing.
Furthermore, several materials being suitable for being used as the bottom plate of the resin basin were investigated. Their transmission curves are shown in Figure 4. As it can be seen, all three candidate materials for the basin bottom provide high transmission values at wavelenghts at about 390 nm. Only Acrylic glass has a high reflectivity and thus a low transmission at wavelengths below 380 nm. As there was no UV-lamp used in our printer and all three materials are highly transparent in the range of visual light, this low transparency of acrylic glass at small wavelength is of no relevance for our project.
Based on these spectra, several basins were built and coated with various substances providing a inert vessel for the resin. At the same time, it has to have low adhesive forces acting between hardened resin and the basin so the printed object sticks to the base plate and not to the resin basin.