As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.
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Each mold half 10, 12 includes a tool body 18, 20 with a forming surface 22, 24 for forming the article. For the embodiments illustrated, each mold half 10, 12 includes an array of four forming surfaces 22, 24 for collectively forming four articles in a single molding operation. For the particular embodiment illustrated, the forming surfaces 22, 24 collectively form a polymeric cap that is utilized for plugging apertures in electrical junction boxes. Although one embodiment is illustrated and described, the invention contemplates any number of tools or mold members, and any molded, cast, stamped article or the like in accordance with the spirit and scope of the present invention.
The mold halves 10, 12 are also illustrated with tool bodies 18, 20 that are formed from a series of laminate sheets 26, 28. Laminate mold tooling provides many advantages and benefits over non-laminate mold tooling that is formed from a single block. These advantages include reduction in labor and costs, reduction in material utilized, reduction in tool body inventory requirements, and advantages in manufacturing, heat transfer and the like. Other advantages and benefits of laminate tooling are set forth in the Manuel U.S. Pat. No. 6,587,742 B2 patent; the Weaver U.S. Pat. No. 5,031,483 patent; and the Manuel U.S. Pat. No. 7,021,523 B2 patent; which have been incorporated by reference.
Typically, laminate tools include a forming surface that is provided collectively across a plurality of laminate sheets. However, some forming operations require a homogenous forming surface to provide a uniform surface upon the article formed by the tool. Such articles may include the caps formed by the first and second mold halves 10, 12 of
Laminate tooling is not typically used for die casting because a uniform or corrosion resistant forming surface is required in die casting. For example, in laminate tooling with a forming surface formed across a series of laminate sheets, the die cast material, such as aluminum attacks the joints of sequentially bonded laminate sheets thereby damaging the tool and diminishing the quality of the article cast by the tool. Accordingly, by utilizing a tool body 18, 20 having the forming surface 22, 24 formed through a single laminate sheet 30, 32 of the respective tool body 18, 20, the joints of the laminate sheets 26, 30 and 28, 32 are not exposed to the die cast material during the casting operation. Thus, the tools 10, 12 of the present invention utilize the benefits of both solid block molds, by providing homogenous forming surfaces and non-laminate forming surfaces, while employing the benefits of laminate mold tooling for rapid fabrication and controlled and/or conformal heat transfer.
By providing compound laminate tooling for forming operations, various materials may be utilized where required. For example, various forming operations require that the forming surface 22, 24 have an adequate hardness for the forming operation. However, to enhance the conformal and controlled heat transfer within the tool body 18, 20 a different material may be provided for the non-forming laminate sheets 26, 28. Thus, the compound tooling of the present invention provides tooling formed from multiple materials for getting the benefits of a hardened surface for the forming operation and a thermally conductive medium for heating and cooling of the forming surface 22, 24.
For example, tool steel is often utilized for the block of the forming surface for die casting operations. For die casting operations, the forming laminate sheets 30, 32 may be formed from tool steel to provide an adequate hardness or corrosion resistance for the die casting operation. For example, the forming laminate sheets 30, 32 may be formed from American Iron and Steel Institute (AISI) tool steel designation H13, which can be hardened to a high hardness. The remaining layers of the tool body 18, 20 may be formed from a material that does not require the forming surface hardness or corrosion resistance properties, yet has sufficient structural integrity to withstand stresses of the tool body during the molding operation. Thus, the non-forming laminate sheets 26, 28 may be formed from an AISI designation 4130 stainless steel for supporting the forming laminate sheets 30, 32 during the molding operation and providing adequate thermal conductivity for controlled and conformal heat transfer of the forming surfaces 22, 24.
Of course, the invention contemplates various combinations of materials for the multiple layers of the tool body 18, 20 in accordance with the present invention to maximize the quality of the article created by the tool 10, 12 by providing the appropriate material hardness or corrosion resistance for the forming surfaces 22, 24 and the appropriate materials for supporting the forming laminate sheets 30, 32, while providing adequate thermal conductivity to the adjacent laminate sheets 26, 28 for controlling heating and cooling of the forming surfaces 22, 24 and the associated article. Such controlled and conformal heating and cooling may increase the quality of the formed article and reduce defects of the formed article while minimizing cycle time. The desired hardness, structural integrity, and rates of heat transfer may be predetermined by conventional mechanics and heat transfer calculations, finite element analysis, or the like, and these design criteria may be specific for each forming operation.
The tools 10, 12 may be utilized for an injection molding machine for molding a polymeric article. In such applications, a tool steel such as AISI designation S7 may be utilized for the forming laminate sheets 30, 32 to provide the adequate hardness for the forming operation, such as a Rockwell measurement within a range of mid-forties to mid-fifties. The non-forming laminate sheets 26, 28 may be formed from a material that is not as hard as S7, but has a higher coefficient of thermal conductivity, such as aluminum or copper. Thus, the S7 layer would provide the appropriate hardness for the forming surfaces 22, 24, while the aluminum or copper offers an improved rate of heat transfer. For example, S7 tool steel has a coefficient of thermal conductivity of approximately twenty-five to thirty-five W/m*K (Watts per meter*Kelvin), with heat transfer that is greatly improved by utilization of copper for the non-forming laminate sheet, since copper has a coefficient of thermal conductivity of approximately 360 W/m*K.
As stated above various combinations may be utilized in accordance with the teachings of the present invention. For example, for some polymeric molding operations, AISI 4130 stainless steel or P20 tool steel, may be utilized for the forming laminate sheets 30, 32, while utilized in cooperation with an enhanced thermally conductive material for the non-forming laminate sheets 26, 28, such as various copper alloys, various tool steel or stainless steel alloys, or the like, or combinations thereof.
In tooling that is formed from solid blocks of material, large quantities of material and time are employed for hollowing out a back surface of the block for reduced weight, and/or improved heat transfer characteristics. By utilizing the compound tooling of the present invention with layers of various materials, the non-forming laminate sheets may have a density less than that of the forming sheet for reducing the overall weight of the tooling. Additionally, the non-forming laminate sheets may be formed with cavities collectively formed therethrough for reducing weight and/or improving heat transfer characteristics.
Another benefit of the compound material laminate tooling of the present invention, is material costs. Tool steels and other hardened layers which are often required for adequate hardness of the forming surfaces 22, 24 are relatively costly in comparison to other materials. Thus, the costs of the tools 10, 12 may be reduced by utilizing a lower cost material for the non-forming laminate sheets 26, 28 that is adequate for the structural integrity and heat transfer characteristics required for the non-forming laminate sheets 26, 28.
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The invention contemplates any number of forming laminate sheets and non-forming laminate sheets in accordance with the present invention. Referring now to
In summary, the present invention combines the advantages and benefits of both block mold tooling and laminate sheet tooling into a common tool or method for making the tool for increasing the advantages, benefits and flexibility of mold tooling while reducing the costs, weight and labor required to fabricate the tooling.
The tooling for forming the article may be fabricated by: providing a first portion of the tool, such as the forming laminate sheet 32 of the second mold half 12 of
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.