Proc. International Congress on Applications of Lasers & Electro-Optics (ICALEO) 2018
Type: Zeitschriftenaufsatz (reviewed)
Conventional stereolithography has a bath based system, in which a constant layer thickness is applied to realize 3D printing. This approach limits the fabrication of parts consisting on one material only. Other drawbacks are coating on only flat and non tapered surfaces without any edges or trenches. To overcome these issues we developed a new approach for additive manufacturing using UV curing polymers. In a layer by layer process, first a liquid monomer film is applied using an Aerosol Jet. Two droplet generators allow the deposition of pure materials as well as various compositions of both materials. In this way, a discrete transition from one pure material to another one from one layer to another is possible. The Aerosol Jet is also able to atomize materials with a high viscosity of more than 1000 mPas, allowing a wider range of materials compared to conventional stereolithography. In this study it is shown, that layer thicknesses between 1 μm and 80 μm are possible and can be applied on non-flat surfaces. After coating, a laser initiates the one photon polymerization reaction. The laser beam is guided with a galvanometric scanner ensuring the 2D patterning on each layer. In the multimaterial approach, the sensitivity and reaction rate of the polymers are different, so that the process parameters have to be adjusted. Due to different feasible material compositions, the polymerization behavior in terms of penetration depth and line width varies. The laser dose depending penetration depth is investigated in this study to obtain an optimum polymerized layer thickness. In the case of a too high laser dose, overpolymerization occurs and overhanging structures lead to less shape accuracy. In the opposite case of a too less laser dose, the single layers cannot connect to each other avoiding the layer by layer process. The results show that a multimaterial additive manufacturing technique can be used to vary the material from one layer to the other and allows the application on non-flat surfaces. By changing the materials within the process, 3D printed pieces can be set with varying properties and opens a wide field of applications.