METHODOLOGY AND CHARACTERIZATION OF PHOTO-POLYMERIZATION PROCESS USING UV CURABLE RESIN
Abstract
Photo-Polymerization (PP) based Additive Manufacturing (AM) technology, also known as Stereolithography (SLA), Rapid Prototyping, or Resin Printing, is very popular technique in 3D printing (3DP) applications. It offers a great advantage over the most common type of 3D printing technique called Fused Filament Fabrication (FFF) in terms of resolution, because resolution in SLA or PP is primarily determined by the spot size of the ultraviolet (UV) source and has a better surface finish due to reduced required force in the layer formation in comparison with FFF. In this research work, the PP module of the multi-modality BioPrinter was developed and the process was characterized using UV light and Solarez 3D printing resin. The process parameters considered in the characterization experiments were nozzle-to-bed distance, nozzle diameter, print head speed and power of the UV Light Emitting Diodes (LEDs). The effects of resin viscosity and resin feed value on the process were also studied. The resin viscosity plays a major role in influencing the dimensional stability of the polymer resin and affects the geometry and the cross-section of the strand fabricated. The characterization experiments for the PP process based on the partial Design of Experiment (DOE) using Design Expert Software from Stat-Ease® were performed assuming cylindrical profile for the strands fabricated. The width (response data) of the strand were found to 3-4 times the nozzle diameter due to the low viscosity of the Solarez resin used. In this work, the viscosity of the Solarez resin was increased by freezing the resin in a conventional freezer. The rationale was to improve the dimensional stability of the resin for stable filament extrusion and thus perform the characterization experiments. The feed for the characterization experiments should also be adjusted based on the observed segment of a circle profile rather than the assumed cylindrical profile. Also, it is recommended to use a high molecular weight resin to minimize the effect of viscosity on the geometry of the fabricated strands.