03-20-2019, 02:32 AM
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Master Modeler
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Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 6,507
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Quote:
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Originally Posted by Ez2cDave
I've been looking at molding techniques and I am intrigued by the use of a "Compression Mold" . . . The two parts could easily be 3-D printed . . . Still doing research . . . Basic concept below.
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David Merriman, a well-known modeler and diver (see: http://www.google.com/search?source...160.4TqoEZK9cBs ) has written several printed and online "How-To" articles on vacu-forming and resin casting (which involve--and can optionally involve, as there are several methods--the same types of molds and techniques that you described in your white paper. I avoided "re-inventing the wheel" in my resin casting by reading his articles. Another trick that I learned about vacu-forming parts came from PSS (Power Scale Soaring [R/C slope-soaring scale glider models of powered aircraft, including jet and rocket planes]):
While this problem seldom occurs in model rocket vacu-formed parts, it can occur in larger ones. PSS modelers (and "regular" scale sailplane builders) often make their own vacu-formed canopies, usually using the male mold process that you covered. PSS models (and many scale model sailplanes) often have green- or gray-painted canopies, to give the impression of transparency (because it obviates the need to include a detailed cockpit interior), while other PSS and scale sailplane modelers vacu-form transparent canopies. Also:
Because the heated plastic sheet--whether opaque or transparent--is pulled down over the male mold, the cooled plastic canopy retains internal stresses that soon form cracks, especially after bumpy landings, even on grass (which can be stopped by drilling holes through the canopy at each end of each crack. But the formation of such stress cracks can be entirely prevented by gently heat-treating the cooled canopy, before removing it from the male mold, as this provides relief of the internal stresses. |