|
 Recently
a client came to us with a part that had been designed in a CAD
(computer-aided design) program. They needed a number of reasonably priced
bronze prototypes in varying sizes, which could be used in a special
application. It was possible to mill them, but not without extensive setup
time. Since we were unsure which final configuration of the bronze
"orbs" would suit the clients needs, we did not want to waste
valuable time building fixtures to produce parts that might not be
ultimately useful. Another possible choice that could work for prototyping
the small metal parts was investment casting.
Investment casting, also known as the
"lost wax process", is a venerable art used to make intricate
metal parts that would be difficult or impossible to produce any other
way. It is the method jewelry designers most often choose to produce their
artwork. Typically, patterns or forms used in investment casting are
fashioned from a special wax that has been carved by hand. In this case,
hand carving could not offer the required tolerances.
Jewelers are now using
high-tech equipment to make wedding rings and pendants.
This was a perfect
opportunity to use our new RP (rapid prototyping) machine, the SolidScape
Modelmaker II™. First, we designed the master orb patterns in SolidWorks™,
our CAD program of choice. Afterwards, we transferred the 3D files to the
machine and programmed it to build physical models in a high-tech
investment casting wax. The Modelmaker II constructs the wax forms with
micro droplets, layer upon layer, until the envisioned part is complete.
Since the layers are only 0.003 of an inch thick (the width of a human
hair), the final dimensions are very close to the original CAD files. The
resultant wax models are the master patterns used in the investment
casting process. In a modern twist we had combined the lost wax method
with our high-tech CAD program to fabricate the bronze orbs, which would
be costly and time consuming to produce any other way.
Below are the steps we
took to cast the bronze orbs:
The mold is oven-cured at 1350 degrees for 3 1/2 hours. Heat vaporizes the
wax tree, leaving a tree-shaped void in the plaster.
We combined the old and the new,
investment casting and a state-of-the-art RP machine, to produce these
intricate parts. Mike achieved the desired level of quality and accuracy
in a relatively quick and cost-effective manner.
Investment casting is not a process we
use frequently. It is simply another "tool" we have available
for specific circumstances. As mentioned before, it is common for jewelers
to use investment casting when creating their art, but it is rare for a
product development firm to offer the process as an option.
|
