Once a radio design shape has been selected.  We use our computer to render an electronic drawing of the radio's shell casing.  At this time we correct any design flows or defects that were not apparent in the sample model radio.  From the computer images we develop  plastic injection molds which will be used in mass production of the radio's parts.  Plastic resins are mixed together and then our molding machines begin producing the radio's parts.


     The first step in mold making consists of plug construction and/or preparation.  The plug may be constructed of nearly anything, as long as its surface can be finished well enough to give a suitable mold surface.  As stated previously, the plug can either be an existing item or something fabricated specifically for the mold-making process. Some of the materials commonly used in plug construction include wood, plaster, metal and polyurethane foam.  The latter comes either as pre-formed sheets or as a two-part “mix and pour” system that chemically reacts to form the foam.  The “mix and pour” foam will conform to the shape of any cavity into which the ingredients are poured. 

     The surface of the plug must be finished at least as well as the desired surface on the part to be produced. In most applications, the preferred plug surface would be a perfectly smooth and polished class “A” finish.  If a particular texture or pattern is desired on the finished part, it can be incorporated into the plug surface.  A high quality, sandable surfacing primer such as the Duratec Grey Surfacing Primer (#1041-B), works well as the finish coat on the plug.  Incorporate flanges and any necessary parting dams onto the plug at this point (see “Special Mold Construction Considerations.) 

      Before beginning construction of the mold, a release agent must be applied to the plug.  This is the most important step in the process, because if the release agent fails to perform, the mold can’t be removed without damaging it and the plug.  A little extra effort at this point is better than hours spent trying to correct damage to the plug and mold.  The release agent can either be a combination of parting wax and PVA, or a one-step release agent such as FibRelease.


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