1. Field of the Invention
This invention relates generally to a method and apparatus for injection molding and for release of a mold tool from injection molded material.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In molding operations such as mold-in-place injection molding it can be difficult to de-mold an open-face rigid injection tool from cured materials such as low observable (LO) performance coatings that have been molded onto an outer surface of an aircraft. When injected materials cure they typically develop a high surface friction contact interface not only with the work surface onto which they have been deposited in the molding process, but also with the cavity or face of an injection mold tool used in that process. This makes it difficult to readily remove such a mold tool from cured material without using wedges or pry methods to break the contact between the tool face and the injected material. To facilitate the use of an automated process to place and remove an open-face injection mold tool it would be advantageous if such a mold tool were configured to be readily demoldable from injected material. If, in an automated process, an injection tool is not readily demoldable from injected material deposited on a work surface, significant damage could occur to the work surface and/or to automation equipment. Automation equipment may be damaged by the application of the amount of pressure, i.e., pull force that would likely be necessary to break surface friction amount of pressure, i.e., pull force that would likely be necessary to break surface friction between tool face and cured material. The sticking of a tool face to cured material formed on a work surface would probably also require personnel intervention, exposing personnel to unnecessary danger.
In vacuum-molding operations one approach to insuring the release of cured molded material from a mold tool face is to affix a stiff pre-formed air-permeable liner to the mold face and connect the liner to a vacuum source. Sheet material to be molded is then placed on the liner and the vacuum source is actuated to draw air from the liner and create suction between the sheet material and the tool face, drawing the sheet material against the tool face. The liner thus functions as a suction conductor between the tool face and sheet material and effectively vacuum forms the sheet material against the tool face. After the sheet material has cured, the liner is separated from the cured material and remains affixed to the tool. To aid in separating the cured sheet material from the liner air may be blown into and through the liner.