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Background:
Rapid Prototyping (RP)
processes (also known as additive manufacturing processes) have
extreme shape creation capabilities. Without specialized tooling or
setups they can fabricate complex shapes with very small lead time
compared to traditional processes. All RP processes build parts by
adding material in 2-D thin two-dimensional
layers. This essentially converts a 3D problem to a 2D problem.
The layered nature of is also the biggest drawback. For smooth
surface finish, the layer thicknesses have to be small. This can result
in build times that can range from hours to days making it impossible
to use RP in any scale of mass manufacturing.
In this research, we proposed to investigate direct three-dimensional additive manufacturing. If successful, this would eliminate the layered nature of RP and greatly reduce unit-part manufacturing time.
Method:We proposed to accomplish three-dimensional additive manufacturing through volumetric heating and fusing of powdered material. Volumetric heating is in turn effect through microwaves. Unlike visible light, microwaves can penetrate opaque materials. Certain material called microwaves susceptors absorb microwaves and convert the energy to heat through di-electric heating. However, the heating processes is strongly non-linear in range of the fusion temperature of these materials. This in turn affects microwave propagation. This implies that controlling the shape of the heated region is impossible. Our solution to this problem was to use a composite powder consisting of room-temperature susceptor material such as SiC and a low melting temperature material such as wax. The susceptor particles act as heat sources while the wax which is microwave transparent acts as the binder. Shape creation is achieved through constructive interference of microwaves emanating from dipole antennae array. The position of the region of high concentration of microwaves is controlled by modulating the phase and amplitude of the input signals to each of the di-pole antennae. Since heat generated is proportional to the square of the field intensity, there is preferential heating and fusion of the powder. This method is similar to the setup used in microwave hyperthermia used to treat breast cancer tumors
Results:
Publications:
Acknowledgment:
This project is funded in part by the National Science Foundation (NSF). Any views, finding, conclusions, or recommendations expressed in this document do not necessarily reflect those of the NSF.
| Dept.
of Mechanical Engineering-Engineering Mechanics Michigan Tech. University 1400 Townsend Drive Houghton MI 49931 Ph: 906-487-1001 |