Authors: A. Kalani Brubaker
Mentors: Nathan Crane
Insitution: Brigham Young University
Binder Jetting is an exciting form of Additive Manufacturing in which a binding agent is selectively deposited on layers of powder to bind the powder together and create a 3D printed part. It is notable for its wide range of materials, energy efficiency, and built-in supports. Much research has been done on how to achieve desirable properties of binder-jetted parts and post-processing, but the fundamental principles of binder-powder interaction and the effects of changing printing parameters are still not fully understood. This research aims to increase that understanding. Each binder-jetted part begins by depositing individual binder droplets in a straight line, and the binder-powder droplets coalesce to form a single line. Adjacent lines are then printed to form a cross-section of the part, the next layer of powder is applied, and the process continues until a 3D part is printed. If the spacing between the droplets is too large or the inter-arrival time too short, the droplets form spheres on the surface of the powder (a phenomenon called balling), and a continuous line is not formed. This research determines how continuous line formation is affected by droplet spacing, inter-arrival time, and controlled misting of the powder bed prior to printing. To examine the effects of these parameters, lines were printed in dry and prewetted powder beds while varying the spacing and inter-arrival time between droplets. The beds were then examined using an optical microscope to determine whether continuous lines were formed. The results were recorded on a graph of inter-arrival time versus droplet spacing, and the “boundary line” for successful line formation was found for each bed. The results showed that the boundary on the prewetted data exhibited a different relationship than dry powder beds, suggesting that a different binder-powder principle may dominate after prewetting. The prewetting also shifted the boundary upwards, making it possible to form continuous lines at higher droplet spacings and shorter inter-arrival times. This increased ability to form continuous lines has the potential to significantly increase the throughput of binder-jetted parts.