The field generally relates to tools for hot forming of certain light weight sheet metal alloys. More specifically, the field pertains to the introduction of a thermal gap in a quick plastic forming tool to provide improved energy usage when the tool is in an open position.
Quick plastic forming (QPF) generally represents a process in which a relatively thin sheet metal workpiece is forced into conformance with a forming surface of a forming tool by a pressurized gas. Suitable sheet metal workpieces utilized in such hot blow forming processes are generally only about a millimeter to a few millimeters in thickness and are composed of materials capable of undergoing high deformation (sometimes superplastic deformation) such as known aluminum and magnesium alloys.
One exemplary embodiment may include the introduction of a thermal gap for a QPF tool that is created between the forming section of the QPF tool and the remainder of the associated components that may reduce or eliminate some of the conductive heat loss paths when the QPF tool is in an open position during part remove or sheet loading. By reducing conductive heat loss when the tool is in an open position, a more precise control for the QPF tool from manufacturing cycle to manufacturing cycle may be realized.
Another exemplary embodiment also includes, in addition to the above-described thermal gaps, a mechanism by which the part forming portion of the forming section may be lifted as the QPF tool is moved to an open position to create one thermal gap for the QPF tool as described above.
Yet another exemplary embodiment may also include, in addition to the above-described thermal gaps, a mechanism by which the pressurization chamber portion and or the part forming portion of the forming section of the QPF tool may be stabilized in a lateral direction when the QPF tool is moved to an open position to create the thermal gaps described above.
These and other exemplary embodiments will become apparent from the present description.
The following description of the embodiment(s) is merely exemplary (illustrative) in nature and is in no way intended to limit the disclosure, its applications, or uses.
An improved apparatus and method for forming shaped parts from thin sheet metal workpieces, or blanks, within a quick plastic forming (QPF) tool is disclosed. To form the shaped parts generally, the blanks are loaded into the QPF tool when the QPF tool is in an open position. The tool is closed and the part is formed to its desired shape using a QPF forming process, in which hot air pressure and heat are utilize to conform the blank to an inner press surface of the part forming section of the QPF tool to form a part having a desired outer appearance. The QPF tool is then opened and the formed part is removed to complete one cycle, wherein the next blank is loaded into the QPF tool to begin the next cycle.
The QPF tool 15 according to the prior art and the QPF tool 115 according to one exemplary embodiment are illustrated in an open position (
The QPF tool 15 or 115 may include generally a part forming section 116, wherein the blank is physically loaded and transformed to a formed part, and a press section 117, which includes all the associated components for moving the QPF tool 15 or 115 between the open position and closed position and other components not directly related to the movement but associated with the QPF tool 15 or 115.
The part forming section 116 includes a part forming portion 121 and the pressurized chamber portion 122 that both may have structures, such as internal electrical heating elements 123 as shown in this exemplary embodiment, to maintain the elevated forming temperature of the process. The part forming portion 121 and the pressurized chamber portion 122 may be both surrounded by an insulating layer 124 and sliding sheets 134. A first set 130A of adjustable tension rods 130 may be secured to pressurized chamber portion 122 and may be slidingly coupled within an upper load plate 127. A second set 130B of adjustable tension rods 130 may be secured to the part forming portion 122 and may be slidingly coupled within a lower load plate 128. The adjustable tension rods 130 may support the mass of the part forming portion 121 and the pressurized chamber portion 122 while the tool 115 is in an open position as shown in
In addition, one or more load posts 126 may be coupled between the pressurized chamber portion 122 and the upper load plate 127. Similarly, one or more load posts 125 may be coupled between the part forming portion 121 and the lower load plate 128. The upper load post 126 may be affixed to the upper load plate 127 and the lower load post 125 may be affixed to the lower load plate 128 using a threaded bolt (shown as 188 in
The load posts 125, 126 may also be used to reduce the area of conductive heat transfer from the heated part forming portion 121 and the pressurization chamber portion 122 to the upper load plate 127 and to the lower load plate 128 when the tool is in the closed position. To further reduce heat transfer to the upper press platen 140 and the lower press platen 141, the upper load plate 127 and the lower load plate 128 may have internal passages 129 through which a cooling fluid (not shown) is circulated. Heat energy may be dissipated into the atmosphere as the cooling fluid is circulated through a chiller mechanism or heat exchanger (not shown).
In the exemplary embodiment as shown in
To form the formed part from the blank in accordance with either the prior art of with the exemplary embodiment as described above, the QPF tool 15 or 115 may first be placed in an open position, as shown in
Next, the QPF tool 15 or 115 may be closed. To accomplish this, force may be applied to the upper press platen 140 in a direction towards the lower press platen 141 (shown as downward in
In the prior art, as shown in
Conversely, as shown in the exemplary embodiment in
The continued force downward may then cause the part forming portion 21 to move downward as well, therein pushing the lower surface 180 of the part forming portion 21 against the springs 131 wherein the sliding sheets 134 move within their respective gaps 172 and wherein the tension rods slide through the opening 178 within the lower load plate 128. Note that no such gap is present in the QPF tool shown in
Next, in both the prior art as shown in
While the QPF tool 15 or 115 is in the closed position, heat generated by the internal heating elements 123 to the pressurization chamber portion 122 may be conducted to the upper load plate 127 through the upper load posts 126. The heat may be partially dissipated by cooling fluid that flows through the internal passages 129 in the upper load plate 127. At the same time, heat generated by the internal heating elements 123 to the part forming portion 121 may be conducted to the lower load plate 128 through the lower load posts 125. The heat may be partially dissipated by cooling fluid that flows through the internal passages 129 in the lower load plate 128. Thus, a substantial portion of the heat may be dissipated before contacting the upper press platen 140 and lower press platen 141 and the upper load plate 127 and lower load plate 128 prior to reopening the QPF tool 15 or 115, which may protect workers loading blanks and unloading formed parts and may also protect sensitive equipment associated with the QPF tool.
The use of load posts 125 and 126 in either QPF tool 15 or 115 may also aid in maintaining precise temperature control substantially uniformly along the entirety of the pressurization chamber portion 122 and part forming portion 121. The load posts 125, 126 may function to reduce the area of conductive heat transfer from the pressurization chamber portion 122 and part forming portion 121 while the QPF tool 15 or 115 is closed as compared to prior art presses not utilizing load posts (i.e. wherein the load plates form a portion of the pressurization chamber portion and the part forming portion). Thus, more of the heat may be maintained uniformly along the part forming surfaces (here the pressurization chamber portion 122 and the part forming portion 121) to improve part consistency from cycle to cycle.
After the blank is formed into the finished part, the QPF tool 15 or 115 may be opened by moving the upper press platen 140 away from the lower press platen 141 (upward as shown in
In the prior art as shown in
Conversely, as shown in the exemplary embodiment of
The movement of the respective load posts 125, 126 to create the afore-mentioned gaps 150A, 150B when the QPF tool 115 is in the open position may reduce the conductive heat paths from the pressurization chamber portion 122 and the part forming portion 121 to a few incidental component paths. Of course, the compressive springs 131 may provide an alternative path for heat transfer, but such a path contributes relatively smaller heat transfer than through the load posts, which has relatively larger surface areas through which to conduct heat. Given that the percentage of time that the QPF tool open may approach and exceed 50% of the manufacturing time (depending upon the configuration of the part formed), it is easy to appreciate that the pressurization chamber portion 122 and part forming portion 121 may retain substantially more heat than conventional QPF tools 15 such as that shown in
In another alternative exemplary arrangement, the insulating layer 124 may be modified such that the QPF tool 115 can be held in a semi-open position, approximately midway between the open position and closed position, so that the gaps 150A and 150B may be maintained while the QPF tool 115 is idled (i.e. not being cycled to form parts from blanks). In this arrangement, the size of the gaps 150A, 150B may be smaller than when the QPF tool 115 is in the open position.
Referring now to
Referring now to
As shown herein, a conical type washer spring 182 may be placed into a cylindrical recess 184 internal to the lower load posts 125 at a position above the threaded bolt 188. Additionally, a cylindrical protuberance 186, not physically attached to the part forming tool 21, may extend from the lower surface 180 of the part forming tool 121 within the confines of the cylindrical recess 184 internal to the lower load post 125.
The washer spring 182 may bridge the gap 150B formed when the QPF tool 115 is in the open position and are therefore designed to lift the part forming portion 121. In addition, the conical washer springs 182 and the cylindrical protruberance 186 provide sliding surfaces for the hot part forming portion 121.
The alternative exemplary embodiment provides a configuration therein that may offer control over the lateral movement (i.e. leftward or rightward movement as shown in
While not shown, the concept configuration of
In any of the exemplary embodiments shown in
Practices of the disclosure have illustrated in the description of exemplary embodiments. But the scope of the disclosure is not limited to these illustrations.