The present invention relates to investment casting, and more specifically to wax molds for investment casting.
The investment casting process (or lost wax process) has been used for thousands of years to create components out of metal. The process starts by creating a pattern out of wax that is a close replica of the final part. The wax pattern gets attached to a sprue to form a mold. The mold gets dipped or “invested” in liquid ceramic and then coated with sand to develop a ceramic shell around the mold. That dipping process can occur multiple times so that a sturdy shell is created around the wax. The wax is then removed (i.e., melted away), the empty mold is heated, and metal is poured into the empty mold. The cast parts are removed from the ceramic shell and finished to final form.
Wax patterns are created with a “gate” attached to them. The gate is the spot where 1) the wax pattern is attached to the sprue to create the mold; 2) the metal flows into the part; and 3) the parts gets separated from the sprue after the part is poured. Assembly of the mold occurs by attaching the wax patterns to the sprue. Attaching the wax patterns to the sprue typically includes the use of a guide that identifies placement of the patterns on the sprue. The guide is placed next to the sprue and the operator marks, typically with a marker, the spot on the sprue where the pattern is to be attached. Operators then heat a flat distal end of the gate and/or flat mating surface of the sprue, orient and place the gate in the previously marked location, and then melt the wax on the gate and sprue to “weld” the gate/pattern to the sprue. A torch is commonly used by the operator to perform this welding. The process is then repeated with each pattern until the mold is completely assembled.
The present invention provides an improved sprue that facilitates the attachment of the wax patterns for building the wax mold. The wax patterns are also designed to cooperate with the sprue to facilitate either manual or automated assembly of the wax mold.
The invention provides, among other things, a wax mold for investment casting. The wax mold includes a sprue having at least one pattern support. The pattern support includes a plurality of sockets formed therein. The wax mold further includes a plurality of wax patterns. Each wax pattern has a portion received in a respective one of the plurality of sockets to support the wax patterns on the at least one pattern support.
In another aspect, the invention provides a method of assembling a wax mold. The wax mold has at least one pattern support with a plurality of sockets formed therein, and a plurality of wax patterns. The method includes positioning a portion of each of the wax patterns into a corresponding one of the plurality of sockets such that the wax patterns are supported within the sockets. The method further includes heating an interface between each socket and wax pattern to weld the wax patterns into the respective sockets.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
As best shown in
The body portion 38 of the post 22 also includes a plurality of steps 46 formed thereon at axially spaced-apart intervals. As will be discussed further below, the steps 46 operate to create the desired axial spacing of the pattern supports 26a, 26b, 26c, 26d, 26e along the post 22. The illustrated steps 46 are formed by virtue of the body portion 38 including a plurality of cylindrical segments 50, 54, 58, 62, 66, and 70 that have different outer diameters. As shown in
While the illustrated post 22 includes six cylindrical segments 50, 54, 58, 62, 66, 70 to form five steps 46 (corresponding with the illustrated five pattern supports 26a, 26b, 26c, 26d, 26e), it is to be understood that other embodiments may include fewer or more segments 50, 54, 58, 62, 66, 70 and steps 46 depending upon the particular casting application. Furthermore, while the illustrated segments 50, 54, 58, 62, 66, 70 are shown as being cylindrical in shape, other embodiments could include different geometries, such as segments having rectangular, square, or other polygonal cross-sections.
The illustrated pattern supports 26a, 26b, 26c, 26d, 26e are initially molded individually from wax, and are then assembled onto the post 22. Each pattern support 26a, 26b, 26c, 26d, 26e includes a body portion 82, which in the illustrated embodiment is annular in shape to encircle the post 22 when the pattern support is installed onto the post 22. A hub 86 is provided to interconnect each pattern support to the post 22, and a plurality of spokes 90 interconnect and space each hub 86 relative to the body portion 82. In the illustrated embodiment, the hub 86 of each pattern support 26a, 26b, 26c, 26d, 26e is sized and configured with a bore 94 of a different inner diameter to substantially corresponds to a respective outer diameter of one of the cylindrical segments 50, 54, 58, 62, 66, 70. With reference to
The remainder of the pattern supports 26b, 26c, 26d, and 26e can be sequentially assembled onto the post 22 in the same manner, such that the support 26b abuts a step 46 and comes to rest along segment 58, the support 26c abuts a step 46 and comes to rest along segment 62, the support 26d abuts a step 46 and comes to rest along segment 66, and the support 26e abuts a step 46 and comes to rest along segment 70. In this manner, the pattern supports 26a-e are easily installed onto the post 22 in the correct sequence to achieve the correct spacing between the individual pattern supports 26a-e, thereby ensuring the proper build of the wax mold 10. The individual pattern supports 26a-e can be secured in place along the post 22 by welding using a torch 98 (see
Just as different geometries of the post segments 50, 54, 58, 62, 66, and 70 are contemplated above, the geometry of the pattern supports 26a-e can also vary in conjunction with changes to the post 22. For example, if the segments 50, 54, 58, 62, 66, and 70 were formed with a square cross-sectional shape, the bore 94 of each hub 86 could likewise have a corresponding square shape. Furthermore, while the body portions 82 are illustrated as being generally ring-shaped, other embodiments could include body portions 82 having square, rectangular, or other polygonal shapes depending upon the particular application.
Once the sprue 14 has been assembled in the manner described above, the wax patterns 18 can be installed onto the pattern supports 26a-e. To greatly facilitate the connection of the wax patterns 18 with the pattern supports 26a-e, each pattern support 26a-e includes one or more sockets 106 formed therein. The sockets 106 are formed into a first surface 110 (see
A plurality of side walls 122a, 122b, and 122c further define the socket 106 and extend between the opening 114 and the bottom wall 118. With reference to
The wax patterns 18 each include a gate portion 126 and a part portion 130. The part portion 130 will vary depending upon the shape and size of the part to be formed. The gate portion 126 is sized and configured to correspond at least in part to the shape of the socket 106 for insertion and retention therein. As best seen in
The use of the sockets 106 enables all of the wax patterns 18 to be installed onto the pattern supports 26a-e before any welding is needed to secure them in place. This is in contrast to prior art methods in which each wax pattern had to be both located and welded one-at-a-time. Furthermore, because the sockets 106 are accurately positioned during the molding of the pattern supports 26a-e, there is no need for any guide, template, or measuring to locate the wax patterns 18 on the pattern supports 26a-e. Instead, the location and spacing of the wax patterns 18 is predetermined and maximized by the location of the sockets 106, which are formed automatically when molding the pattern supports 26a-e. A human operator can quickly and easily install all of the wax patterns 18 into the respective sockets 106 without concern for accurate placement. Alternatively, an automated machine can also be used to install the wax patterns 18 into the sockets 106, with the machine's controller being programmed with the incremental spacing parameters required to locate the sockets 106. In the illustrated embodiment, the wax patterns 18 each include a cylindrical boss 146, which can be used to facilitate handling and placement of the wax patterns 18 by an automated machine. Of course, the specific size, configuration, and location of the boss 146 can vary depending upon the machine being used.
After all of the wax patterns 18 have been installed into the sockets 106, the wax patterns 18 can be welded to the pattern supports 26a-e to secure them in place. As best shown in
It is to be understood that the use of the sockets 106 for supporting the wax patterns 18 need not be used only with the illustrated sprue 14, and its particular form for assembly with the post 22 and the pattern supports 26a-e. Instead, various different conventional sprues could be modified to include the inventive arrangement of the sockets 106 and mating gate portions 126. This would include arrangements in which the pattern supports are pinned or otherwise secured to the post (i.e., without the steps 46 or cylindrical segments 50, 54, 58, 62, 66, and 70), or in which pattern supports of varying geometries do not get mounted onto posts at all. The use of the sockets 106 and the mating gate portions 126 greatly facilitates the positioning and securing of the wax patterns 18 to any suitable pattern support portion of a sprue, both in a manual or a machine-automated process.
Various features and advantages of the invention are set forth in the following claims.
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