Experimental investigation and parametric optimization of taper angle in 3D inkjet printing without support material

3D inkjet printing (3D-IJP), also known as material jetting, is one of the additive manufacturing (AM) technologies which is viewed as a key enabling technology for applications where miniaturized multi-material features are targeted, such as in printed electronics or microfluidic devices. In 3D-IJP, support material is deployed for small narrow features as well to ensure geometrical accuracy and stability. However, support materials often made up a large part of the printed part which are removed after printing. The removal does not only waste support material, but consumes cleaning solvents as well and contradicts with the claim of AM technologies for being sustainable. The influence of UV-parameters on edge quality has been reported in the literature. In order to facilitate sustainable fine feature printing without any usage of support material, this study investigates the effect of two UV-parameters on the edge straightness of printed pillars, namely UV-strategy and UV-intensity. Twenty-seven trials were performed with the settings UV-intensity 5.6, 4, 1.6 W/cm2 and curing strategies bidirectional and unidirectional curing (in print direction and only in the reverse print direction). ... mehrThe edge quality is assessed by the taper angles (0° means perpendicular to the substrate, the ideal value) for each pillar by means of an optical microscope. The test structure consists of three specimens, each of them containing pillars with aspect ratios 1 to 0.2 (height/width, consistent height of 400 µm). The smallest taper angles among the printed specimens were achieved for the UV-settings 5.6 W/cm2 curing intensity and unidirectional curing immediately after printing: 5.4° ± 3.6° for a 400 µm wide pillar and 28.33° ± 8.7° for a 2000 µm wide pillar.