Part Two, Assembly.
By Richard A. Coyle
In Part One I outlined all of the modifications needed to create the masters for this intricate model.
Those of you who have done some prop casting will realize that I have left out many details about mold making, such as positioning of pour points and air vents, parting lines, etc.
The thrust of this initial article series is to relate the
making of the blaster model from a research, engineering, and fabrication
standpoint. To properly cover all
of these basic mold making details
could take as many pages as the first two articles combined.
Besides, it is a well covered
subject in many other sources, so I have decided to gloss over it here.
Perhaps some time in the near future I will do an article
series on making molds and casts in the context of creating this type of model.
Meanwhile, back to our saga:
With the new molds ready, I cast an initial run of four sets of every component. This was to insure that I would finish with at least two completed models, one for Phil and one for me, with a selection of spare parts from whatever was left over.
After casting the raw parts, all flash is trimmed (the
little extra plastic “lip” that typically finds its way into the parting
lines of a mold), and all pour
points and vents are dressed.
Next, all of the various holes must be drilled, and those that will have screws used to fasten parts are tapped to the appropriate thread.
Each model is then sanded with 300 grit sand paper, followed by 400 grit, and finally red Scotch-Brite® pads to a smooth finish.
I test fit the grips and sand them to fit.
models can now be “dry assembled” to check for proper fit and any correction
requirements. Any problems are fixed and the parts refitted.
I am satisfied that everything fits and functions well, all of the components
are disassembled and mounted on wooden posts for painting.
and every part gets a base coat of primer, two to three coats of enamel in the
appropriate color, and then three finish coats of clear enamel.
next step was to turn down an aluminum tube to the same outside diameter of
the bolt, and then bore it to the inside diameter
of the bolt’s necked-down end to provide for the rotation inside the receiver.
Again using the lathe, I turn down the ends of a 3/4-inch acrylic tube for the barrel and then crown the business end to reproduce a true gun barrel appearance.
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