Extrusion Molding Composites
Patents with Abstracts
Fiber Reinforced Materials (FRM)
“A thermoplastic molding system includes a thermoplastic extrusion die for the extrusion of a thermoplastic slab profiled by adjustable die gate members, i.e., dynamic die settings, for varying the thickness of the extruded material in different parts of the extruded slab. The thermoplastic extrusion die has a trimmer for cutting the extruded thermoplastic slab from the thermoplastic extrusion die. A plurality of thermoplastic molds, which may be either vacuum or compression molds, are each mounted on a movable platform, such as a rotating platform, for moving one mold at a time into a position to receive a thermoplastic slab being trimmed from the thermoplastic extrusion die. A molded part is formed with a variable thickness from a heated slab of thermoplastic material being fed still heated from the extrusion die. A plurality of molds are mounted to a platform to feed one mold into a loading position for receiving a thermoplastic slab from the extrusion die and a second mold into a release position for removing the formed part from the mold. The platform may be a shuttle or a rotating platform and allows each molded part to be cooled while another molded part is receiving a thermoplastic slab. A thermoplastic molding process is provided having the steps of selecting a thermoplastic extrusion die setting in accordance with the apparatus adjusting the thermoplastic extrusion die for varying the thickness of the extruded material passing therethrough in different parts of the extruded slab. The thermoplastic material is heated to a fluid state and extruded through the selected thermoplastic die which has been adjusted for varying the thickness of the extruded material in different parts of the extruded slab, trimming the extruded thermoplastic slab having a variable thickness to a predetermined size, and directing each trim slab of heated thermoplastic material onto a thermoforming mold, and molding a predetermined part in the mold so that the molded part is formed with a variable thickness from a slab of material heated during extrusion of the material.
This extrusion-molding" process also facilitates the formation of thermoplastic composite structures reinforced with long fibers (greater than about one-half inch) because the extruder dispenses the molten, thermoplastic composite material through the dynamic die, gravitating the material directly onto a lower mold that is movable with respect to the position of the dynamic die. As used herein, the term "lower mold" refers to the lower half of a matched-mold into which thermoplastic material is directed. Similarly, the term "upper mold" refers to the upper half of the matched-mold within which the desired thermoplastic part is formed, when the upper and lower mold halves are combined i.e., closed. The lower mold may be moved via a trolley to fill the cavity of the mold with varying quantities of the thermoplastic composite material. For example, if the cavity defined by the lower and an upper mold is larger over a certain horizontal range, the lower mold may be slowed down to receive more molten thermoplastic composite material in that region. The dynamic die employs flow control elements that vary or regulate the flow of the molten extruded thermoplastic composite material to deliver different quantities of material from each of the flow control element, to deposit the material selectively across the width of the lower mold in a direction perpendicular to the direction it is moving. The thermoplastic composite material may be molded with long fibers (greater than about one-half inch) having a concentration of at least ten percent (10%) by weight to as much as fifty to sixty percent (50-60%) by weight, with low fiber-fracture rates. After the molten extruded thermoplastic composite material gravitates onto the lower mold, the trolley is automatically transported into a press that closes the upper mold onto the lower mold to form the composite part.
One embodiment according to the principles of the present invention includes a system and method for forming an article from thermoplastic material and fiber. The method includes heating thermoplastic material to form a molten thermoplastic material while blending with the fiber. The molten thermoplastic material is blended with the fibers to form a molten composite material having a desired concentration of fiber by weight and/or volume. The molten composite material may then be extruded through the dynamic die to form a prescribed flow of composite material and gravitated onto a lower portion of a mold for forming the article. The lower mold may be discretely moved in space and time at varying speeds while receiving the flow of composite material to deposit a predetermined quantity of molten composite material thereon conforming exactly to the amount of material required in the mold cavity of the lower mold. The upper portion of the mold may be pressed against the predetermined quantity of molten composite material and closing on the lower portion of the mold to form the article.”
[Polk Jr and Polk Sr, US Patent 8,192,664 (6/5/2012)]
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Roger D. Corneliussen
Maro Polymer Links
Tel: 610 363 9920
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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 6/18/2012.