Space Grant Consortium - University of Wisconsin - Green Bay

Dynamics Characterization of the Electron Beam Freeform Fabrication System
Introduction
Matthew Kallerud
Milwaukee School of Engineering
Abstract
Electron beam freeform fabrication, a layer-additive manufacturing process, is a
technology with promising applications in aerospace. The process melts metal
wire with an electron beam and creates metallic parts. There are several
parameters in this process that can affect build quality, including the system
dynamics of a six axis robotic motion system. An understanding of the system
dynamics was required to investigate its effect on build quality. High speed
measurement equipment revealed that the robotic system consistently overshot its
target velocity. This overshoot was reduced by one order of magnitude by
utilizing existing commands within the control system.
Electron b eam freeform fabrication (EBF 3 ) is a layer additive manufacturing process that uses
wire feedstock to build metallic parts. The electron beam creates a m olten pool on a substrate,
wire is fed into the molten pool, and the robotic system translates the molten pool to deposit the
melted wire. This process is used to fabricate metallic parts and structures, of primarily titanium
and a luminum, for a w ide v ariety o f aerospace applications. C ompared to c urrent me tallic
fabrication methods, this process is more efficient in terms of energy, time, and material, which
drives f urther r esearch of t he pr ocess. The p rocess, w hich o perates i n a v acuum, h as b een
deployed in a portable system and proven to work in zero, Lunar, and Martian gravities. In the
near future astronauts will be able to use it to construct structures in space or fabricate parts on
the moon, Mars, or the International Space Station. It also has novel application in aeronautic
structures; for ex ample, non-orthogonal structures ar e more eas ily built w ith E BF 3 than with
conventional machining processes [1] [2] [3].
EBF 3 Dynamics
The EBF 3 system includes a robotics system that moves on six axes. In addition to normal x, y,
and z m ovements, t he s ystem i s cap able o f tiltin g th e electron b eam gun, tiltin g th e ta ble on
which the part lies, and rotating the table. Six degrees of freedom allows for unusual shapes and
formations when building.
The r obot i s c ontrolled through p rogrammed commands c alled G -code. These a re s equential
commands that can control robot movements via time or distant constraints.
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