US20040200256A1

US20040200256A1 - Formed panel and associated method

Info

Publication number: US20040200256A1
Application number: US10/412,612
Authority: US
Inventors: Edmund Chu; Jeffrey Shoup; Kirit Shah
Original assignee: Alcoa Inc
Current assignee: Howmet Aerospace Inc
Priority date: 2003-04-11
Filing date: 2003-04-11
Publication date: 2004-10-14

Abstract

An improved method of forming a panel out of a workpiece, the panel being substantially free of ripples and free of ruptures, includes forming a number of smooth bulges in the workpiece in order to effectively spread a quantity of excess material that results from forming a number of desirable features into the workpiece by taking up in the bulges an amount of material. The quantity, dimensions, locations, orientations, shapes, and configurations of the bulges with respect to the features are determined by an iterative process that examines the degree to which the excess material resulting from formation of the features is effectively spread about the panel. Effective material spreading can be characterized by at least one of reduced thickening of the workpiece, reduced amplitude of ripples in the workpiece, and increased period of the ripples. An improved panel formed according to the aforementioned process is also disclosed.

Description

FIELD OF THE INVENTION

The present invention relates generally to metalworking and, more particularly, to a method of forming metal panels substantially without ripples or ruptures therein, as well as to such a panel.

BACKGROUND OF THE INVENTION

It is known that many raw materials such as metals, plastics, woods, and the like initially exist in the form of sheets, bars, ingots, planks, and the like which are subjected to material forming operations in order to transform the materials into finished products. Among the many material forming operations are, for example, stamping, rolling, forging, and casting. The properties of the material and the configuration of the final product often are considered when determining the material forming operations that will be performed in creating the final product.

Numerous different types of stamping operations are known in the relevant art. One such type of stamping operation involves placing a sheet of material between two tools and bringing the tools together with sufficient energy to alter the shape of the sheet in a desirable fashion. The tooling typically includes a number of features that are transferred to the sheet during the stamping operation to form corresponding features in the stamped sheet. In forming such features in the sheet during the stamping operation, the tooling typically moves portions of the material of the sheet from initial locations to subsequent locations, with the result that during the stamping operation portions of the material can be said to flow between the initial and subsequent locations according to the various features of the tooling. The ability of the material to flow in the aforesaid fashion often is dictated by numerous mechanical properties of the material such as the yield strength and the elongation properties of the material, as well as other properties. Accordingly, tooling for stamping operations often must be configured with the mechanical and other properties of the workpiece, i.e., the sheet or block of raw material, in mind.

Many materials have certain properties that would be desirable in a final product, but also have other properties that may be undesirable with respect to economical manufacturing operations. For example, while aluminum has a lower density compared with steel, and thus a product manufactured out of aluminum often will weigh less than a comparable product manufactured out of steel, aluminum can be more difficult to form in a conventional stamping operation than steel.

It is thus desired to provide an improved material forming technique which overcomes various limitations imposed by the properties of the material being formed. It is also desired to provide an improved final product that is formed according to the aforementioned improved method.

SUMMARY OF THE INVENTION

An improved method and apparatus in accordance with the present invention meets and exceeds these and other needs. An improved method of forming a panel out of a workpiece, in which the resulting panel is substantially free of ripples and free of ruptures, includes forming a number of bulges in the workpiece to provide material flow and to take up a quantity of excess material that results from forming a number of desirable features into the workpiece. The bulges can be of numerous shapes including, for example, ovals, ellipses, kidneys, racetracks, and other shapes, whether or not symmetric. Each bulge additionally may include a first bulge portion and a second bulge portion, and the second bulge portion may be at least partially disposed on the first bulge portion. The first bulge portion protrudes from the panel in a first direction, and the second bulge portion may protrude in a second, different direction which may be a substantially opposite direction. The quantity, dimensions, locations, and orientations of the bulges with respect to the features are determined by an iterative process that examines among other values the change in thickness and the elongation of various portions of the workpiece to determine an optimum solution. An improved panel formed according to the aforementioned process is also disclosed.

Accordingly, an aspect of the present invention is to provide an improved method of forming panels with a stamping operation.

Another aspect of the present invention is to provide an improved method of forming sheets of aluminum or other metals into finished products.

Another aspect of the present invention is to perform a stamping operation on a workpiece that avoids tearing and/or fracturing of the workpiece while resisting, minimizing, or eliminating the formation of ripples and ruptures in the finished product.

Another aspect of the present invention is to provide an improved method of performing a stamping operation on a sheet of aluminum or other metal.

Another aspect of the present invention is to facilitate the performance of a stamping operation on a workpiece by taking up a quantity of excess material that results from the formation of a desirable feature into the workpiece.

Another aspect of the present invention is to overcome many of the presently existing obstacles to the use of conventional forming operations on certain materials.

Another aspect of the present invention is to provide an improved method of economically transforming workpieces of certain materials into finished products.

Accordingly, an aspect of the present invention is to provide a method of forming a metal panel out of a workpiece, in which the general nature of the method can be stated as including forming a feature into the workpiece, drawing away a quantity of excess material of the workpiece from a region of the workpiece, avoiding fracturing the workpiece, and resisting the formation of visible wrinkling in the region.

Another aspect of the present invention is to provide a method of characterizing a degree of wrinkling of a metal workpiece resulting from forming a feature into the workpiece, in which the general nature of the method can be stated as including determining the degree of effective spreading of excess material that results from formation of the feature, said determining the degree of effective spreading including at least one of determining an amplitude of a ripple in the workpiece, determining a period of a ripple in the workpiece, and determining a change in thickness of the workpiece along a portion of the workpiece.

Another aspect of the present invention is to provide a metal panel that can be generally described as having a minimum of wrinkling while avoiding rupturing thereof during the forming process, the panel including an area that is structured and arranged to take up excess material during the forming process.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the invention can be gained from the following Description of the Preferred Embodiment when read in conjunction with the accompanying drawings in which: [0017]
FIG. 1 is a perspective view of a prior art panel formed in accordance with a prior art methodology; [0018]
FIG. 2 is a perspective view of an improved panel of the present invention that has been formed according to an improved method of the present invention; [0019]
FIG. 2A is a sectional view as taken along [0020] line 2A-2A of FIG. 2; FIG. 3 is an enlarged view of an encircled portion of the panel of FIG. 1; FIG. 4 is an enlarged view of an encircled portion of the panel of FIG. 2; FIG. 5 is an enlarged sectional view as taken along line 5-5 of FIG. 3; FIG. 6 is an enlarged sectional view as taken along line 6-6 of FIG. 4; and FIG. 7 is a schematic view of a bulge of a panel in accordance with the present
Similar numerals refer to similar parts throughout the specification. [0021]

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

A prior art panel D formed according to a prior art method is indicated FIG. 1. The panel D includes a feature H formed therein which results in wrinkling of various degrees in various regions of the panel D. The feature H is a bend formed in the panel D, but as used herein the expression “feature” and variations thereof shall refer broadly to the result of essentially any type of metal forming operation performed on a workpiece with the possible exception of a cutting operation. It is desired to provide an improved method and a resulting improved panel having a lesser degree of wrinkling than the panel D. [0022]
An improved panel [0023] 4 in accordance with the present invention and formed in accordance with an improved method of the present invention is indicated generally in FIG. 2. As will be described in further detail below, the method of the present invention permits the panel 4 to be formed with a minimum of wrinkling while avoiding rupturing of the material thereof during the forming process. An example of the method of present invention will be described herein as being performed on an aluminum workpiece, whereby the resulting exemplary panel 4 is formed out of aluminum. It is expressly noted, however, that the method of the present invention and the panel 4 can be formed out of other nonmetallic materials, and also can be formed out of metals other than aluminum, without departing from the concept of the present invention. Additionally, while the exemplary method in accordance with the present invention is generally described herein in the context of a stamping operation, it is noted that the various advantageous aspects of the method of the present invention are not limited to use in conjunction with stamping operations, and rather can be employed in conjunction with other forming or other types of operations.
Portions of the method of the present invention and the panel [0024] 4 are described in terms of a workpiece. As employed herein, the expression “workpiece” and variations thereof refers generally to a member upon which an operation can be performed as well as a member upon which an operation has been performed. As used herein, the expression “a number of” and variations thereof shall refer to plural as well as singular quantities without limitation.
The exemplary panel [0025] 4 depicted in FIG. 2 can, as indicated above, equally be referred to as a workpiece. The exemplary panel 4 depicted in FIG. 2 could, for instance, be a component of an automobile and is formed out of a sheet of aluminum. As used herein, the expression “aluminum” and variations thereof shall refer equally to pure aluminum, aluminum alloys, and substantially any other material that incorporates aluminum in one form or another. The exemplary aluminum discussed herein is 6022-T4 aluminum, although other types of aluminum or other materials can be employed in conjunction with the method of the present invention to form the panel 4 without departing from the concept of the present invention. The method of the present invention can be employed without limitation to form structures other than the panel 4.
The panel [0026] 4 includes at least a first feature 8 formed therein, and to this extent shares some similarity with the panel D having the feature H formed therein. The reference numeral 8 of FIG. 2 identifies a contour line indicative of a bend formed in the panel 4.
The panel [0027] 4 additionally and advantageously includes a number of bulges 12 formed therein. As will be explained in further detail below, the incorporation of the bulges 12 into the panel 4 permits the panel 4 to be manufactured with minimal ripples and without rupturing of the material thereof. As used herein, the expression “ripple” and “wrinkle” and variations thereof may be employed interchangeably and refer broadly to an undulation, a bend, or other type of discontinuity in a piece of material, and may be visible or invisible to the naked eye depending upon its nature. The bulges 12 themselves are generally not considered to constitute rippling or wrinkling.
Currently known aluminum materials that have been used commonly in automotive and aerospace applications generally at most have an elongation of about 25% in uniaxial tension. As used herein, the term “elongation” and variations thereof refers to the amount by which a dimension of a workpiece can be plastically extended, i.e., stretched, before the occurrence of a failure in the material, such as a rupture or other failure. The elongation properties of aluminum are, at least in part, based upon the processing techniques employed in forming the aluminum sheets as well as the alloying elements incorporated into the sheet. Previously known aluminum had an elongation in the range of only about 10-15% at room temperature. It is also known that steel has an elongation in the range of about 30-40%. [0028]
It is noted that formation of the features H and [0029] 8 into the panels D and 4, respectively, can cause the formation of a quantity of excess material. Such excess material results inherently from performing the formation action and refers to material that may result in the formation of ripples or other imperfections if it is not spread out or taken up in some fashion. Ripples are undesirable because they are aesthetically unappealing and can result in inconsistent dimensions, and also because they can result in sealing problems that permit the intrusion of water or present other leakage problems in some applications.
In accordance with an aspect of the improved method of the present invention, the [0030] bulges 12 are advantageously provided in the panel 4 to effectively spread out a sufficient portion of the excess material to resist the formation of visible rippling or wrinkling into the panel 4 while avoiding rupturing of the panel 4. As used herein, the expression “effectively spread” and variations thereof shall refer broadly to any of a variety of operations that can be caused to occur with respect to a panel whereby excess material that results in a given location in the panel due to formation of a feature in the panel is caused to be distributed about the panel to a sufficient degree to resist the formation of visible rippling. The bulges 12 of the present invention are advantageously provided to effectively spread the excess material to a sufficient degree to resist the formation of visible wrinkling while avoiding rupturing of the panel 4.
It is generally stated herein that portions of the excess material resulting from formation of the [0031] feature 8 are taken up in the bulge 12. Such an expression is not, however, intended to mean that the specific portion of the workpiece constituting the excess material is translated across the panel 4 and formed into the bulges 12 and thus becomes resident therein. Rather, the expression refers to the general flowing of the material of the workpiece, including the excess material, in a direction generally toward the bulge 12, and that formation of the bulge 12 takes up a sufficient quantity of the material of the workpiece that the excess material thereof does not cause rippling. As such, the specific excess material that had originated from formation of the feature 8 may not be disposed in the bulge 12, but rather the general flowing of the material toward the bulge 12 results in sufficient material being taken up by the bulge 12 to resist the formation of visible rippling.
The [0032] bulges 12 can be of virtually any configuration, whether being symmetrical or asymmetrical, as is indicated by the bulge 12 of FIGS. 2 and 2A. The exemplary bulge 12 includes a first bulge portion 14 and a second bulge portion 18. The exemplary first bulge portion 14 can be said to be disposed on the panel 4, and the exemplary second bulge portion 18 can be said to be disposed on the exemplary first bulge portion 14. As is particularly depicted in FIG. 2A, the first bulge portion 14 protrudes in a first direction from the panel 4, and the second bulge portion 18 extends from the first bulge portion 14 in a second, generally opposite, direction. The combination of the first and second bulge portions 14 and 18 extending in generally opposite directions allows the net height of the bulge 12, i.e., the maximum departure of the bulge 12 from the panel 4, to be less than would otherwise be the case if the first and second bulge portions extended in the same direction from the panel 4.
It can also be seen that the exemplary [0033] first bulge portion 14 is of a different size, shape, and orientation than the exemplary second bulge portion 18. Such a diverse relationship may or may not occur or be required in all circumstances. It is also noted that one or more of the bulges may be configured to not include multiple bulge portions depending upon the needs of the application.
The resulting panel [0034] 4 thus is relatively inexpensive to manufacture and is substantially free of ripples and free of rupturing. The aforementioned method in accordance with the present invention advantageously can be employed in numerous different formation processes or product forms, or other processes or product forms employing different materials, for the production of different final products without departing from the concept of the present invention.
As set forth above, the configuration of the [0035] bulges 12, i.e., position, orientation, size, shape, quantity, and the like, are selected such that formation of the bulges 12 and the feature 8 in the same forming operation results in effective spreading of the excess material that inherently results from formation of the feature 8 sufficiently to avoid visible wrinkling. Effective spreading of the excess material of the panel 4 during the formation operation can occur from one or more of the following occurrences: resisting thickening of the material, reducing the amplitude of the wrinkles, and increasing the period of the wrinkles. In regard to the latter two situations, a wrinkle is considered in generally the same terms as a sine wave, i.e., having an amplitude and a period. The “period” of a wrinkle is the distance along the panel occupied by a single wrinkle, i.e., undulation. In accordance with the method and apparatus of the present invention, a given wrinkle or undulation will be relatively less visible if its height, i.e., amplitude, is reduced and/or if its period is increased, i.e., the wrinkle is “stretched” or “spread” such that it occurs across a relatively larger portion of the panel.
With regard to resisting thickening of the panel [0036] 4 in the encircled region of FIG. 2, a correlation has been noted between thickening of a location and the occurrence of visible wrinkling in the panel. Accordingly, it has also been found that when a forming operation is simulated with the help of commercially available simulation software, the selection of a configuration for the bulges 12 that results in a relatively reduced degree of thickening of the material of the panel 4 in the encircled region of FIG. 2 also results in a relative reduction in the amplitude of the ripples and/or an increase in the period of the ripples.
Major differences exist between the method of the present invention and the common practice of providing simple take-up beads to eliminate wrinkles. Such simple take-up beads are disposed in the locations of a panel where wrinkling is expected to occur in order to take up excess material in those locations. The method of the present invention advantageously permits the [0037] bulges 12 to be positioned in areas that are spaced from the locations where wrinkling would occur, and such spacing of the bulges 12 can be advantageously employed to permit the final configuration of the panel 4 to fall within the design constraints thereof. The bulges 12 are placed strategically around the regions where wrinkling is expected to occur, with the bulges 12 being arranged to cause stretching of the excess material toward the bulges 12 to a sufficient degree to avoid the formation of visible wrinkling in the panel 4 while avoiding rupturing. The numbers of bulges 12, as well as, for instance, the locations, orientations, sizes, shapes, depths, and configurations thereof with one or more bulge portions, are selected through an iterative process and by determining the degree of effective spreading of the excess material throughout other regions of the panel 4 as characterized by one or more of reduced material thickening, reduction in ripple amplitude, and increase in ripple period.
In accordance with the present invention, an improved method of characterizing a degree of wrinkling in a workpiece, such as that depicted in FIG. 3, may include determining a change in thickness of the workpiece along a portion of the workpiece, and determining a length for the portion of the workpiece along which the aforementioned change in thickness occurs. Additionally or alternatively, the method may include analyzing the rippling of the workpiece to determine if a reduction in the amplitudes of the ripples and/or an increase in the periods of the ripples has been achieved. A baseline characterization of thickening is shown in FIG. 3, and a baseline characterization of ripple amplitude and period is shown in FIG. 5. [0038]
With regard to thickening of the panel, it is desired to reduce the change in thickness, i.e., thickening, in certain regions under consideration of the panel [0039] 4. It is also desired to increase the size of the regions across which such change in thickness occurs, such as would occur from the spreading of the excess material. It is alternatively desirable to reduce the degree of the change in thickness so that the thickening becomes relatively more uniform across the region while maintaining or increasing the length of the region across which such change in thickness occurs as long as the result is a reduced degree of visible rippling.
As is indicated in FIG. 3, various changes in thickness occur in the depicted exemplary encircled (FIG. 1) region of the panel D as a result of forming the feature H into the panel D. As indicated above, the degree of visible rippling can be indicated, at least in part, by thickening of the panel D and the length of the portion of the panel along which such thickening occurs. Since the degree of thickening varies across the region under consideration, it likely is practical to identify a range of values of the change in thickness and a corresponding length along which the range of values occurs. For instance, the numeral K in FIG. 3 indicates a region of the panel D that is 77.0 millimeters in length and across which the change in thickness ranges between 0 and 4.5%. In the instant example the change in thickness is characterized as a percentage change in thickness. The maximum thickening, i.e., the peak change in thickness, is 4.5% of the original sheet thickness. [0040]
In order to further characterize the degree of thickening of the panel D, it may be desirable to identify one or more sub-regions of the aforementioned region K, with the sub-regions characterizing the lengths over which smaller ranges of the change in thickness values occur. For instance, FIG. 3 indicates the sub-regions P and T, which are sub-regions of the region K. [0041]
The change in thickness along the sub-region P ranges from 1.6% and 4.5%, it being noted in the present example that 4.5% is the same peak change in thickness identified above in the region K. The change in thickness between 1.6% and 4.5% in the sub-region P occurs along a length of 32.0 millimeters. In the exemplary sub-region P, the nonzero minimum change in thickness of 1.6% determined from calculations can be arbitrarily chosen depending upon the various changes in thickness of the panel D. [0042]
It can be seen that the sub-region T is not only a sub-region of the region K, but is also a sub-region of the sub-region P. In the sub-region T, the change in thickness of the panel D ranges between 2.8% and the peak of 4.5%, and such range of values occurs over a length of 14.0 millimeters. While the region K may characterize the gross or overall degree of rippling across a relatively large region, the identification of the sub-regions P and T further characterizes the change in thickness by characterizing the distribution of the various values of the change in thickness. [0043]
In order to configure the panel [0044] 4 to reduce thickening in such a way as to reduce or minimize visible rippling, the method of the present invention improves upon the baseline values described by the region K and the sub-regions P and T in FIG. 3. In so doing, one may employ the aforementioned iterative process and measure the effect of various configurations and positions of the bulge 12, which potentially would include analysis of different configurations of first and second (and possibly additional) bulge portions 14 and 18. It is ultimately desired to reduce the peak change in thickness. It is preferable to additionally reduce the lengths of the regions across which the change in thickness occurs, although this is not necessarily required in order to provide an improvement in the degree of rippling of the panel 4, and it is also noted that desirable spreading of excess material may desirably increase the size of the regions across which thickening occurs.
It is repeated that a reduction in visible rippling can additionally or alternatively result from a reduction in the amplitudes of the ripples and/or an increase in the periods of the ripples. The ripples in the regions K, P, and T are depicted in cross section in FIG. 5. The area in which ripples would inherently be highly visible is at the edge of a bend, such as in the encircled portion of FIG. 5. The encircled portion of FIG. 5 includes two ripples, and the amplitude and period of each of the two ripples can be said to establish baseline values for ripple amplitude and period that could be improved upon in reducing the appearance of visible rippling. [0045]
The regions of the improved panel [0046] 4 depicted generally in FIGS. 2, 4, and 6 demonstrate an example of a reduced degree of rippling. FIGS. 2 and 2A depict at least two of the bulges 12 formed in the panel 4, and FIG. 2A depicts the contour resulting from formation of the bulges 12 as compared with the contour show in broken lines that would result from formation of the feature 8 in the absence of the bulges 12. The gross or overall rippling in the encircled portion of FIG. 2 is indicated in FIG. 4 at the numeral 16, which shows that a change in thickness of between −0.8% and 1.64% occurs over a range 107.0 millimeters. It thus can be seen that on the improved panel 4 the peak thickness has been reduced from a value of 4.5% on the panel D to 1.64% on the improved panel 4. It can also be seen that the change in thickness occurs along a portion of the panel 4 that is 107.0 millimeters length, which is a greater region that that characterized by the length of 77.0 millimeters in the region K of the panel D. Such an increased length of material spread can be indicative of material spreading. The significant reduction in the peak change of thickness from 4.5% in the panel D to 1.64% in the panel 4 is indicative of rippling of a lesser degree in the panel 4 than in the panel D.
It is noted that further improvement potentially could be achieved if the peak change in thickness of the panel [0047] 4 were reduced to less than 1.64% or if the length of the range 16 were increased beyond 107.0 millimeters or both. What is desired, however, is to improve, i.e., reduce, the rippling of the panel 4 to a sufficient degree that any rippling that had been visible in the panel D is substantially invisible to the naked eye in the panel 4 while avoiding rupturing of the panel 4. It is understood, however, that this represents an ideal solution that potentially may not be achieved in some circumstances, and thus an improvement would still exist if the degree of wrinkling is reduced even if such wrinkling is still visible to the naked eye. In such a situation, an improvement would be achieved if the improved panel has a greater degree of material spreading and/or a decrease in the degree of thickening when compared with the baseline panel.
It can be seen from FIG. 4 that two sub-regions, i.e., a [0048] sub-region 20 and a sub-region 24 have been identified. In the sub-region 20, the change in thickness varies between 0.4% and 1.64%, and such change of thickness values occur over a length of 54.0 millimeters. The change in thickness values in the sub-region 24 range between 1.6% and 1.64%, and such thickness change values occur over a length of 2.0 millimeters. It is noted that the sub-regions 20 and 24 are not intended to correspond with the sub-regions P and T of the panel D inasmuch as the calculated nonzero minimum change in thickness values of 0.4% and 1.6% of the sub-regions 20 and 24, are each significantly less than the calculated nonzero minimum change in thickness values of 1.6% and 2.8% of the sub-regions P and T, respectively. However, the length of the sub-region 20 of 54.0 millimeters is greater than the length of the sub-region P of 32.0 millimeters, and the degree of thickening in the sub-region 20 is significantly less than that of the sub-region P, which indicates a marked improvement with respect to thickening over the baseline values.
The amplitudes and periods of the ripples of the improved panel [0049] 4 are indicated in FIG. 6. The two ripples encircled in FIG. 6 can be said to correspond with the encircled baseline ripples of FIG. 5 and to indicate an improvement over the baseline performance. Specifically, the encircled zone of FIG. 6 occupies a relatively larger region of the panel 4 than the encircled region of FIG. 5 occupies of the baseline panel D. As such, the periods of the exemplary two most important ripples of FIG. 6 have been increased, which represents an improvement over the baseline ripple periods and results in a relatively reduced degree of visible rippling in the improved panel 4. The two encircled ripples in FIG. 6 are also of lesser amplitudes than the two encircled ripples of FIG. 5, which represents an improvement over baseline performance and is indicative of further reduced visible wrinkling in the improved panel 4.
The exemplary improved panel [0050] 4 thus has reduced visible wrinkling when compared with the baseline panel D, and such improvement is indicated by a reduction in thickening, a reduction in the amplitudes of ripples, and an increase in the periods of ripples. As indicated above, an improvement over baseline performance in the panel 4, i.e., a reduced degree of visible wrinkling, can result from any one or more of reduced thickening, reduced amplitude, and increased period.
The exemplary bulges [0051] 12 depicted in FIG. 2 include exemplary first and second bulge portions 14 and 18 that are each generally non-symmetrical, both width-wise and length-wise. Such asymmetry, or symmetry in other applications, is highly dependent upon the design constraints of the panel 4. The two exemplary bulges 12 of FIG. 2 also appear to include a number of generally dished-shaped components.
In this regard, an [0052] exemplary bulge 112 is indicated schematically in FIG. 7. The exemplary bulge 112 includes a perimeter 168 having curved and straight portions. While not expressly depicted in FIG. 7, the exemplary bulge 112 also is of varying depths. The bulge 112 includes first and second bulge portions 114 and 118.
The material of the panel [0053] 4 out of which the exemplary bulge 112 is formed is drawn from a number of locations in the immediate vicinity of the bulge 112. One such exemplary location 172 depicted in FIG. 7 is indicated as lying along a perpendicular 176 to a tangent 180 to the perimeter 168 at a point 184 on the perimeter 168, with the perpendicular 176 extending through the point 184. By varying the parameters of the bulge 112, i.e, the perimeter 168, and the size, shape, positioning, and depth of the first and second bulge portions 114 and 118, a sufficient portion of the excess material of the panel 4 resulting from formation of the feature 8 can be taken up by the bulge 112 and/or spread across the panel 4 so as to reduce the degree of wrinkling of the panel 4, preferably to a minimum, or at least to a point where such rippling is substantially invisible to the naked eye.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof. [0054]

Claims

What is claimed is:

1. A method of forming a metal panel out of a workpiece, the method comprising:

forming a feature into the workpiece;

drawing away a quantity of excess material of the workpiece from a region of the workpiece;

avoiding fracturing the workpiece; and

resisting the formation of visible wrinkling in the region.

2. The method of claim 1 wherein

said drawing away a quantity of excess material includes forming a bulge into the workpiece and drawing generally toward the bulge at least a portion of the excess material.

3. The method of claim 2 wherein

said forming a bulge in the workpiece includes selecting a configuration for the bulge to resist the formation of visible wrinkling in the region during said forming a feature in the workpiece.

4. The method of claim 3 wherein

said selecting a configuration for the bulge to resist the formation of visible wrinkling includes selecting a configuration for the bulge to effectively spread at least a portion of the excess material away from the region.

5. The method of claim 2 wherein

said drawing away a quantity of excess material includes effectively spreading at least a portion of the excess material away from the region.

6. The method of claim 5 wherein

said effectively spreading includes at least one of:

reducing the amplitude of a number of ripples formed in the region;

increasing the period of the ripples formed in the region; and

resisting thickening of the workpiece in the region.

7. The method of claim 5 wherein

said effectively spreading includes determining a distribution of thickening along a portion of the workpiece, and selecting a configuration for the bulge to spread the distribution of thickening along the at least portion of the workpiece.

8. The method of claim 2 wherein

said forming a bulge in the workpiece includes forming the bulge in a location that is spaced from the region.

9. The method of claim 2 wherein

said forming a bulge in the workpiece includes forming a substantially smooth bulge.

10. The method of claim 2 wherein

said forming a bulge in the workpiece includes forming a first bulge portion and forming a second bulge portion, the second bulge portion being at least partially disposed on the first bulge portion.

11. The method of claim 10 wherein

said forming a first bulge portion includes forming the first bulge portion to protrude outwardly from the workpiece in a first direction;

said forming a second bulge portion including forming the second bulge portion to at least partially extend from the first bulge portion in a second, different direction.

12. The method of claim 11 wherein

said forming the second bulge portion to at least partially extend from the first bulge portion in a second, different direction includes forming the second bulge portion to at least partially extend from the first bulge portion in a substantially opposite direction.

13. The method of claim 2 wherein

said forming a bulge includes forming a bulge having a perimeter;

said taking up a quantity of excess material including drawing at least a portion of the quantity of excess material from a location disposed on a perpendicular to a tangent to the perimeter at a point on the perimeter, the perpendicular extending through the point.

14. A method of characterizing a degree of wrinkling of a metal workpiece resulting from forming a feature into the workpiece, the method comprising:

determining the degree of effective spreading of excess material that results from formation of the feature, said determining the degree of effective spreading including at least one of:

determining an amplitude of a ripple in the workpiece;

determining a period of a ripple in the workpiece; and

determining a change in thickness of the workpiece along a portion of the workpiece.

15. The method of claim 14 wherein

said determining a change in thickness includes determining a length for the portion of the workpiece along which the change in thickness occurs.

16. The method of claim 15 further comprising

providing a characterization of the degree of wrinkling based upon both the change in thickness and the length.

17. The method of claim 15 wherein

said determining a change in thickness of the workpiece along a portion of the workpiece includes determining a range of the change in thickness along the portion of the workpiece.

18. The method of claim 17, further comprising

determining a peak change in thickness in the range of the change in thickness.

19. The method of claim 17 wherein

said determining a range of the change in thickness along a portion of the workpiece includes determining a nonzero minimum change in thickness and a peak change in thickness along the portion of the workpiece.

20. The method of claim 15 wherein

said determining a change in thickness of the workpiece includes determining the change in thickness as a percentage change in thickness.

21. A metal panel having a minimum of wrinkling while avoiding rupturing thereof during the forming process, the panel including an area that is structured to take up excess material during the forming process.

22. The panel of claim 21 wherein

the area includes a substantially smooth bulge.

23. The panel of claim 22 wherein

the bulge protrudes from a portion of the panel surrounding the bulge.

24. The panel of claim 23 wherein

the bulge includes a first bulge portion and a second bulge portion;

the first bulge portion protruding from the panel;

the second bulge portion being at least partially disposed on the first bulge portion.

25. The panel of claim 24 wherein

the first bulge portion protrudes outwardly from the panel in a first direction;

the second bulge portion protruding from the first bulge portion in a second, different direction.

26. The panel of claim 25 wherein

the second bulge portion protrudes from the first bulge portion in a substantially opposite direction.

27. The panel of claim 22 wherein

the bulge includes a perimeter, and wherein at least a portion of the excess material out of which the bulge is formed includes material drawn from a location disposed on a perpendicular to a tangent to the perimeter at a point on the perimeter, the perpendicular extending through the point.

28. The panel of claim 22 wherein

the bulge is asymmetric.

29. The panel of claim 21 wherein

the panel includes a feature formed therein, the excess material resulting at least in part from formation of the feature.

30. The panel of claim 29 wherein

the bulge is disposed at a location that is spaced from the feature.