Using the Uniform Droplet Spray Process
by
Jennifer Hyunjong Shin
Bachelor of Science in Mechanical Engineering
Submitted to the Department of Mechanical Engineering
in Partial Fulfillment of the Requirements for the Degree of
BACHELOR OF SCIENCE IN MECHANICAL ENGINEERING
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
May 1998
ABSTRACT
This work studied the feasibility of rapid prototyping using the
Uniform Droplet Spray (UDS) process. Straight and stable liquid metal jets
are crucial requirements in the application of UDS to rapid prototyping.
Methods to maintain the jet straight and stable were developed. Hardware
improvements include an auxiliary orifice mounting fixture and a new crucible
bottom with a tightly-fitting orifice-pocket. A droplet trajectory controller,
including deflection plates and a pulse provider to a charging plate, was
developed to precisely deliver droplets for deposition. The degree of separation
between deflected and undeflected streams of droplets was modeled and the
prediction was compared with experimental results. This comparison revealed
that the degree of actual deflection was approximately twice as high as
the predicted value. Using the trajectory controller, deposition was conducted
using pure tin (Sn) with droplet impact conditions of velocity and liquid
fraction of 4.5 m/s and 97%, respectively. The deposition frequency was
varied in the experiment to study its effects on deposit shapes. A low
frequency deposition at 57Hz produced a vertical pillar, whereas a high
frequency deposition at 574Hz resulted in a large drop.