Additive manufacturing of glass: post process surface treatment of DLP parts

There is a high demand for new manufacturing technologies in the production of technically functional glass objects and complex glass shapes. Optical components such as complex light guiding structures, adapted, miniaturised lenses and mirrors as well as components for optical data processing require high optical transparency. To address this demand, within the Glass3D project research is being conducted on production of optically transparent glass objects using Additive Manufacturing (AM). In a part of this study, objects are first additively manufactured using stereolithography/DLP (Digital Light Processing) and then sintered in order to remove binder and fuse the glass particles together. The material used, FP20, is a rapidly crystallising glass in which undesirable crystals form on the surface during the sintering process. These crystals must be removed post AM process by mechanical grinding and subsequent polishing. However, complex, thin walled geometries with curved surfaces or undercuts, as they are possible to be created by AM, cannot be processed using conventional grinding and polishing wheels. Thus, those processes are not applicable for complex shaped parts. Commonly applied sandblasting is very limited in reproducibility due to the manual control of the abrasive media nozzle. A possible alternative is automated particle blasting to remove the crystalline layer and reduce the surface roughness. Automated abrasive blasting enables processing of complex workpieces with controllable movement between particles and parts and therefore reproducible kinetic energy and process time. This study investigates feasibility of automated particle blasting to post-process glass objects from DLP material with high brittleness. Kinetic energy of the particles and the processing time are varied. The evaluation of the results by means of confocal microscopy showed that an improvement of the surface roughness (Rz) could be achieved.