Method and apparatus for controlling the stacking height of stackable products during compression molding off stops
Method and apparatus for controlling the stacking height of stackable products during compression molding off stops includes slides that are movable into and out of an end of blind pockets in a compression mold in which the stack height surfaces are formed during the molding cycle. The slides are held in a retracted position until after the mold is closed and the molding compound flows to the shape of the molding cavity inside the mold including the blind pockets. Then the slides are extended into the ends of the respective blind pockets the same distance to compress the molding compound and obtain the desired height of the stack height surfaces formed by the blind pockets.
1. A method of controlling the height of stack height surfaces of stackable products during compression molding of the products off stops comprising the steps of placing a charge of molding compound in a compression mold while the mold is open, closing the mold to apply pressure to the molding compound causing the molding compound to flow to the shape of a mold cavity inside the mold that includes blind pockets that form the stack height surfaces during the molding cycle, and extending slides into an end of the blind pockets the same distance after the mold has been closed a predetermined length of time to compress the molding compound and obtain the desired height of the stack height surfaces formed by the blind pockets.
2. The method of claim 1 wherein the slides are held in a retracted position during initial closing of the mold.
3. The method of claim 2 wherein the mold includes a fixed mold half and a movable mold half, and the slides are axially slidable in openings in the fixed mold half in alignment with the ends of the respective blind pockets.
4. The method of claim 3 wherein the slides have the same perimeter shape as the ends of the stack height surfaces contacted thereby during extension of the slides into the blind pockets and provide venting control of any trapped air from the blind pockets through clearance spaces around the slides.
5. The method of claim 1 wherein all of the slides are simultaneously extended into the ends of the respective blind pockets.
6. The method of claim 1 wherein the slides create high pressure areas in the ends of the stack height surfaces contacted thereby during extension of the slides into the ends of the respective blind pockets which densify the molding compound to minimize non-fills and porosity in the stack height surfaces.
7. The method of claim 1 wherein the mold includes a fixed mold half and a movable mold half, and the extension of the slides into the blind pockets after closing of the mold is limited by push back pins on a common travel plate for all of the slides contacting stops on the movable mold half when the mold is closed.
8. The method of claim 7 wherein the stops on the movable mold half are shimmible to adjust the distance that the slides move into the ends of the respective blind pockets when the mold is closed.
9. The method of claim 1 wherein the pressure that is applied to the slides to cause the slides to extend into the ends of the respective blind pockets is relaxed before the mold is opened in order to keep the molded product in the mold cavity during opening of the mold.
10. The method of claim 9 wherein the slides are further extended after the mold is fully opened to eject the molded product from the mold.