Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

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Introduction
material to form metallurgical bonds, but the larger amount of heat transferred
tended to warp the substrate or delaminate it.
The SDM laboratory has produced custom-made functional mechanical
parts and has embedded prefabricated mechanical parts, electronic
components, electronic circuits, and sensors in the metal layers during
the SDM process. It has also made custom tools such as injection molds
with internal cooling pipes and metal heat sinks with embedded copper
pipes for heat redistribution.
Mold SDM
The Rapid Prototyping Laboratory at Stanford University, Palo Alto,
California, has developed its own version of SDM, called Mold SDM,
for building layered molds for casting ceramics and polymers. Mold
SDM, as diagrammed in Figure 11, uses wax to form the molds. The wax
occupies the same position as the sacrificial support metal in SDM, and
water-soluble photopolymer sacrificial support material occupies and
supports the mold cavity. The photopolymer corresponds to the primary
metal deposited to form the finished part in SDM. No machining is performed
in this process.
The first step in the Mold SDM process begins with the decomposition
of CAD mold data into layers of optimum thickness, which depends
on the complexity and contours of the mold. The actual processing
begins at Figure 11(a), which shows the results of repetitive cycles of the
deposition of wax for the mold and sacrificial photopolymer in each
layer to occupy the mold cavity and support it. The polymer is hardened
by an ultraviolet (UV) source. After the mold and support structures are
built up, the work is moved to a station (b) where the photopolymer is
removed by dissolving it in water. This exposes the wax mold cavity into
which the final part material is cast. It can be any compatible castable
material. For example, ceramic parts can be formed by pouring a gelcasting
ceramic slurry into the wax mold (c) and then curing the slurry.
The wax mold is then removed (d) by melting it, releasing the “green”
ceramic part for furnace firing. In step (e), after firing, the vents and
sprues are removed as the final step.
Mold SDM has been expanded into making parts from a variety of
polymer materials, and it has also been used to make preassembled
mechanisms, both in polymer and ceramic materials.
For the designer just getting started in the wonderful world of mobile
robots, it is suggested s/he follow the adage “prototype early, prototype
often.” This old design philosophy is far easier to use with the aid of RP
tools. A simpler, cheaper, and more basic method, though, is to use