Forming of sheet metal

Abstract

A method of manufacturing a formed sheet metal structure is provided, and a corresponding apparatus. A sheet metal workpiece is processed using a main anvil tool and a main forming tool such that basal regions are fixed relative the main anvil tool. An auxiliary forming tool and an auxiliary anvil tool are used to contact the sheet metal workpiece such as to deform first and second sidewall portions with respect to the basal regions. Concurrently progressively sliding fold contact regions of the auxiliary forming tool and the auxiliary anvil tool along a fold region of the workpiece carries out shear material transfer in the fold region to form a deformed fold region. The auxiliary forming tool and the auxiliary anvil tool each has a workpiece tensioning region extending away from a side thereof. The respective sidewall portion of the workpiece is slidingly gripped by the workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool during the shear material transfer in the fold region.

Description

[0001] FORMING OF SHEET METAL

[0002] Field of the Invention

[0003] The present invention relates to method of manufacturing a formed sheet metal structure. The present invention also relates to sheet metal working apparatus.

[0004] Up to half of all the sheet metal made globally each year is not used in a final product but is cut off during manufacture. Two main causes of this loss are blanking (cutting a flat shape out of the coiled up long flat sheets made in rolling mills) and trimming after deep drawing, with the latter dominating. These losses are an unavoidable by-product of these processes. Further discussion and quantification of these losses is set out in Horton and Allwood (2017).

[0005] The cost in both money and carbon emissions associated with these losses is high, although at present the process of blanking followed by deep drawing is considered to be the most efficient way to make shaped sheet metal components such as e.g. car body components. In blanking and deep drawing, a key consideration is the avoidance of wrinkling and tearing during forming.

[0006] WO 2020 / 043832 A1 discloses a folding-shearing process for forming metal shells having a basal region and sidewalls with curved corner regions upstanding therefrom. In the process, shrink and stretch flanges can be formed from sheet metal with as little thinning or unwanted deformation as possible. In the process of forming a stretch flange, the material located at the curve requires stretching, but in such a way that sheet thinning and edge cracking in the curve can be limited. In the process of forming a shrink flange, the material located at the curve requires compression, but in such way that sheet thickening and buckling / wrinkling in the curve can be limited. In WO 2020 / 043832, this is achieved by shear material transfer in the process.

[0007] In WO 2020 / 043832, the base of the shell from which the sidewall upstand is planar. Therefore, it is only where there is a curved sidewall upstanding from the base that shrink and stretch flanges are formed and shearing needs to be conducted.

[0008] WO2024 / 079349 A1 proposed a development from WO 2020 / 043832 A1 in order to form metal shells having a non-planar base in a simplified forming process. The difficulty in forming such metal shells is that, even where there is not a curved sidewall, and therefore a shrink or stretch flange may not be present in the sense of WO 2020 / 043832 A1 , the act of bending the sidewalls to upstand from the non- planar base generates potential shrink and stretch zones in the adjacent regions of the sidewall extending from adjacent basal regions that are not co-planar. The shrink and stretch regions in the sidewall are prone to buckling / wrinkling and tearing, respectively when using known sheet metal working apparatus.

[0009] The approach used in WO2024 / 079349 A1 is to bend the workpiece to form at least a first basal region and a second basal region, with a bend between them. These basal regions are held between a main anvil tool and a main forming tool such that the basal regions are fixed relative the main anvil tool. A first sidewall portion extends between the first basal region and an edge of the workpiece, and a second sidewall portion extends between the second basal region and the edge. Using an auxiliary forming tool, 8659351

[0010] 2 the first and second sidewall portions are deformed with respect to the first and second basal regions to form a fold region between the first sidewall portion and the second sidewall portion. In some discussions of this technology, this fold region is referred to as a “beak”. In contact with the top surface of the workpiece, the auxiliary forming tool then progressively slides along the first fold region. An auxiliary anvil tool is in contact with the bottom surface of the workpiece. The auxiliary anvil tool also progressively slides along the first fold region concurrently with the auxiliary forming tool to control the deformation of the first second fold region. In this way, shear material transfer is carried out in the first fold region in a manner that can avoid wrinkling. The approach can be extended to include one or more further basal regions and bends, and thereby to include one or more corresponding sidewall portions extending between the further basal regions and the edge, and one or more corresponding fold regions. Additionally or alternatively, the approach can be extended to include a similar forming process with respect to an opposite edge of the workpiece.

[0011] Summary of the Invention

[0012] Although the approach used in WO2024 / 079349 A1 can avoid primary buckling / wrinkling associated with the fold region, a problem can sometimes arise that secondary buckling / wrinkling, e.g. caused by structures such as slanted sidewalls, can still occur.

[0013] The present inventors have realised that the approach used in WO2024 / 079349 A1 can be further improved in order to provide additional control over the workpiece during the shear material transfer in a manner that results in a higher quality formed shape.

[0014] Accordingly, in a first aspect, the present invention provides a method of manufacturing a formed sheet metal structure, comprising the steps of: providing a sheet metal workpiece having first and second surfaces opposed to each other and at least one edge; providing a main anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; constraining at least a part of a first basal region and an adjacent second basal region of the workpiece between the main anvil tool and a main forming tool such that the basal regions are fixed relative the main anvil tool, wherein a first sidewall portion extends between the first basal region and the edge, and a second sidewall portion extends between the second basal region and the edge; providing an auxiliary forming tool with a tool surface for contact with and constraint of at least a part of the second surface of the sheet metal workpiece; providing an auxiliary anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; directing the auxiliary forming tool along an axis of movement to contact the sheet metal workpiece such as to deform the first and second sidewall portions with respect to the first and second basal regions and thereby to form a first fold region in the sheet metal workpiece between the first sidewall portion and the second sidewall portion, until the first surface of the sheet metal workpiece contacts the auxiliary anvil tool; and 8659351

[0015] 3 concurrently progressively sliding first fold contact regions of the auxiliary forming tool and the auxiliary anvil tool along the first fold region of the workpiece to carry out shear material transfer in the first fold region to form a deformed first fold region, wherein the auxiliary forming tool has a first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary forming tool; wherein the auxiliary anvil tool has a corresponding first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary anvil tool; and wherein the first sidewall portion of the workpiece is slidingly gripped by the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool during the shear material transfer in the first fold region.

[0016] The first workpiece tensioning regions of the auxiliary forming and anvil tools thus apply tension to the workpiece by slidingly gripping the workpiece at the first sidewall portion, i.e. outside the first fold region. Advantageously, tension introduced in this way into the workpiece can reduce or eliminate instances of secondary buckling / wrinkling.

[0017] A further benefit of introducing tension into the workpiece using the workpiece tensioning regions is that it allows workpiece springback to be controlled. Such springback can occur when the formed sheet metal structure is released from the tooling and relaxation of stored elastic strain energy causes a postmanufacturing change of shape of the structure. Small amounts of springback can be compensated for by changing the shape of the tooling, but large amounts may not be compensatable in this way. However, tensioning the workpiece using the workpiece tensioning regions provides a route to change the amount of elastic strain energy stored in the as-drawn structure, and thereby control even relatively large amounts of springback, particularly springback that would occur in the sidewall portion (if it were not gripped by the workpiece tensioning regions).

[0018] The auxiliary forming tool’s first workpiece tensioning region may be a continuation of the auxiliary forming tool’s first fold contact region, or may be spaced therefrom by a gap. Similarly, the auxiliary anvil tool’s first workpiece tensioning region may be a continuation of the auxiliary anvil tool’s first fold contact region, or may be spaced therefrom by a gap.

[0019] The auxiliary forming tool may have a second workpiece tensioning region extending from an opposite side of the first fold contact region of the auxiliary forming tool, and the auxiliary anvil tool may have a corresponding second workpiece tensioning region extending from an opposite side of the first fold contact region of the auxiliary anvil tool. The second sidewall portion of the workpiece can then be slidingly gripped by the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool during the shear material transfer in the first fold region. The auxiliary forming tool’s second workpiece tensioning region may be a continuation of the auxiliary forming tool’s first fold contact region, or may be spaced therefrom by a gap. Similarly, the auxiliary anvil tool’s second workpiece tensioning region may be a continuation of the auxiliary anvil tool’s first fold contact region, or may be spaced therefrom by a gap. 8659351

[0020] 4

[0021] In the constraining step at least a part of a third basal region of the workpiece adjacent to the first basal region may be constrained between the main anvil tool and a main forming tool such that the third basal region is fixed relative the main anvil tool, wherein a third sidewall portion extends between the third basal region and the edge. In the directing step, the third sidewall portion may then also be deformed with respect to the third basal region thereby to form a second fold region between the first sidewall portion and the third sidewall portion, and in the sliding step, second fold contact regions of the auxiliary forming tool and the auxiliary anvil tool may also be concurrently progressively slid along the second fold region of the workpiece to carry out shear material transfer in the second fold region to form a deformed second fold region. In this case, the first workpiece tensioning region of the auxiliary forming tool may extend between the first and second fold contact regions of the auxiliary forming tool, and the first workpiece tensioning region of the auxiliary anvil tool may extend between the first and second fold contact regions of the auxiliary anvil tool. The auxiliary forming tool’s first workpiece tensioning region may be a continuation of the auxiliary forming tool’s second fold contact region, or may be spaced therefrom by a gap. Similarly, the auxiliary anvil tool’s first workpiece tensioning region may be a continuation of the auxiliary anvil tool’s second fold contact region, or may be spaced therefrom by a gap.

[0022] Conveniently, the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be planar and substantially parallel to each other. If present, the same applies to the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool. In such cases, to help avoid producing sharp bends in the workpiece, the normal to the planes of the first (or second) workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be disposed at an angle of 80° or less (preferably 70° or less, and more preferably 60° or less) from the axis of movement of the auxiliary forming tool, and / or the normal to the planes of the workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be disposed at an angle of 10° or more (preferably 20° or more and more preferably 30° or more) from the axis of movement of the auxiliary forming tool.

[0023] Alternatively, however, the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be smoothly curved surfaces which are spaced from each other by a gap of substantially uniform thickness. If present, the same applies to the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool. This can also help to avoid producing sharp bends in the workpiece while allowing the workpiece to turn through greater total angles than would otherwise be possible. For example, the first (or second) workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be curved such that the workpiece turns through an angle of 70° or more (preferably 80° or more) as, on being slidingly gripped by the workpiece tensioning regions, it is drawn through a gap therebetween.

[0024] The method may further comprise a step of bending the workpiece to form a respective basal bend between adjacent basal regions, the constraining step being performed on the bent workpiece. The bending step can be executed by clamping the sheet metal workpiece between respective tool surfaces of the main anvil tool and the main forming tool. Executing the bending step in this manner is beneficial in 8659351

[0025] 5 that the basal bend(s) formed in the workpiece will conform exactly with the shape of the respective tool surfaces of the main anvil tool and main forming tool. The basal bend between the first and second basal regions produces a shrink or stretch zone and thus is a factor in the formation of the first fold region. If present, the basal bend between the first and third basal regions may similarly be a factor in the formation of the second fold region.

[0026] Additionally, or alternatively, during the deformation of the first and second sidewall portions with respect to the first and second basal regions a first sidewall bend may be formed between the first sidewall portion and the first basal region, and a second sidewall bend may be formed between the second sidewall portion and the second basal region, the first sidewall bend being offset from the second sidewall bend. When the third basal region is present, during the deformation of the third sidewall portion with respect to the third basal region a third sidewall bend may be formed between the third sidewall portion and the third basal region, the first sidewall bend also being offset from the third sidewall bend. The offset between the first sidewall bend and the second sidewall bend produces a shrink or stretch zone and thus may be a factor in the formation of the first fold region. If present, the offset between the first sidewall bend and the third sidewall bend may produces a shrink or stretch zone be a factor in the formation of the second fold region.

[0027] The main anvil tool may comprise a sidewall. In such a case, the sidewall of the main anvil tool may constrain at least a part of the first surfaces of the sidewall portions of the workpiece during the directing step; and the sidewall of the main anvil tool may constrain at least a part of the first surface of the first fold region during the step of sliding the auxiliary forming tool along the first fold region. When a third basal region is present, the sidewall of the main anvil tool also constrains at least a part of the first surface of the second fold region during the step of sliding the auxiliary forming tool along the second fold region. The main anvil tool sidewall may be substantially planar. Alternatively, when offset first and second sidewall bends are formed, and optionally offset first and third sidewall bends are formed, the main anvil tool sidewall may have a respective step extending in the axis of movement corresponding to the location of each offset.

[0028] The final shape of any one, any two or all three of the first, second and third (if present) sidewall portions may include a respective planar major region which, on a cross-section perpendicular to the planar major region and containing the axis of movement of the auxiliary forming tool, deviates from the axis of movement by 1 ° or more, and preferably by 2° or 3° more. In some embodiments, this angle may be not more than 45°, or not more than 30°, or not more than 15°. The height of such a planar major region measured along the axis of movement of the auxiliary forming tool may be at least 50 mm, and preferably at least 100 mm.

[0029] The main anvil tool and the auxiliary anvil tool may each be connected to a first press plate, at least one of the main anvil tool and the auxiliary anvil tool being movably connected to the first press plate. When the auxiliary anvil tool is movably connected to the first press plate, the first press plate and the auxiliary anvil tool may be configured such that the auxiliary anvil tool’s first fold contact region, its first workpiece 8659351

[0030] 6 tensioning region and optionally its second workpiece tensioning region are movable independently of each other.

[0031] The main forming tool and the auxiliary forming tool may each be connected to a second press plate, at least one of the main forming tool and the auxiliary forming tool being movably connected to the second press plate. When the auxiliary forming tool is movably connected to the second press plate, the second press plate and the auxiliary forming tool may be configured such that the auxiliary forming tool’s first fold contact region, its first workpiece tensioning region and optionally its second workpiece tensioning region are movable independently of each other.

[0032] In a second aspect, the present invention provides a sheet metal working apparatus for manufacturing a formed sheet metal structure from a sheet metal workpiece, the sheet metal workpiece having first and second surfaces opposed to each other and at least one edge, the sheet metal working apparatus comprising: a main anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; a main forming tool, which, with the main anvil tool, is configured to constrain a first basal region and an adjacent second basal region of the workpiece between the main anvil tool and a main forming tool such that the basal regions are fixed relative the main anvil tool, wherein a first sidewall portion extends between the first basal region and the edge, and a second sidewall portion extends between the second basal region and the edge; an auxiliary forming tool with a tool surface for contact with and constraint of at least a part of the second surface of the sheet metal workpiece; an auxiliary anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; wherein the auxiliary forming tool is configured to be directed along an axis of movement to contact the sheet metal workpiece such as to deform the first and second sidewall portions with respect to the first and second basal regions and thereby to form a first fold region in the sheet metal workpiece between the first sidewall portion and the second sidewall portion, until the first surface of the sheet metal workpiece contacts the auxiliary anvil tool; wherein first fold contact regions of the auxiliary forming tool and the auxiliary anvil tool are configured to be concurrently progressively slid along the first fold region of the workpiece to carry out shear material transfer in the first fold region to form a deformed first fold region; wherein the auxiliary forming tool has a first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary forming tool; wherein the auxiliary anvil tool has a corresponding first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary anvil tool; and wherein the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool are configured to slidingly grip the first sidewall portion of the workpiece during the shear material transfer in the first fold region. 8659351

[0033] 1

[0034] Thus the apparatus of the second aspect is suitable for performing the method of the first aspect.

[0035] Accordingly, optional features of the method of the first aspect pertain also to the apparatus of the second aspect.

[0036] For example, the auxiliary forming tool’s first workpiece tensioning region may be a continuation of the auxiliary forming tool’s first fold contact region, or may be spaced therefrom by a gap. Similarly, the auxiliary anvil tool’s first workpiece tensioning region may be a continuation of the auxiliary anvil tool’s first fold contact region, or may be spaced therefrom by a gap.

[0037] For example, the auxiliary forming tool may have a second workpiece tensioning region extending from an opposite side of the first fold contact region of the auxiliary forming tool, and the auxiliary anvil tool may have a corresponding second workpiece tensioning region extending from an opposite side of the first fold contact region of the auxiliary anvil tool. The second sidewall portion of the workpiece can then be slidingly gripped by the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool during the shear material transfer in the first fold region. The auxiliary forming tool’s second workpiece tensioning region may be a continuation of the auxiliary forming tool’s first fold contact region, or may be spaced therefrom by a gap. Similarly, the auxiliary anvil tool’s second workpiece tensioning region may be a continuation of the auxiliary anvil tool’s first fold contact region, or may be spaced therefrom by a gap.

[0038] For example, the main forming tool, with the main anvil tool may also be configured to constrain at least a part of a third basal region of the workpiece adjacent to the first basal region between the main anvil tool and a main forming tool such that the third basal region is fixed relative the main anvil tool, wherein a third sidewall portion extends between the third basal region and the edge. The auxiliary forming tool may also be configured to be directed along an axis of movement to contact the sheet metal workpiece such as to also deform the third sidewall portion with respect to the third basal region and thereby to form a second fold region between the first sidewall portion and the third sidewall portion. Second fold contact regions of the auxiliary forming tool and the auxiliary anvil tool may then be concurrently progressively slid along the second fold region of the workpiece to carry out shear material transfer in the second fold region to form a deformed second fold region. In this case, the first workpiece tensioning region of the auxiliary forming tool may extend between the first and second fold contact regions of the auxiliary forming tool, the first workpiece tensioning region of the auxiliary anvil tool may extend between the first and second fold contact regions of the auxiliary anvil tool, and these first workpiece tensioning regions may be configured to slidingly grip the first sidewall portion of the workpiece during the shear material transfer in the first and second fold regions. The auxiliary forming tool’s first workpiece tensioning region may be a continuation of the auxiliary forming tool’s second fold contact region, or may be spaced therefrom by a gap. Similarly, the auxiliary anvil tool’s first workpiece tensioning region may be a continuation of the auxiliary anvil tool’s second fold contact region, or may be spaced therefrom by a gap.

[0039] For example, the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be planar and substantially parallel to each other. If present, the same applies to the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool. The normal to the 8659351

[0040] 8 planes of the first (or second) workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be disposed at an angle of 80° or less (preferably 70° or less and more preferably 60° or less) from the axis of movement of the auxiliary forming tool, and / or the normal to the planes of the workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be disposed at an angle of 10° or more (preferably 20° or more and more preferably 30° or more) from the axis of movement of the auxiliary forming tool.

[0041] For example, the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be smoothly curved surfaces which are spaced from each other by a gap of substantially uniform thickness. If present, the same applies to the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool. The first (or second) workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool may be curved such that the workpiece turns through an angle of 70° or more (preferably 80° or more) as, on being slidingly gripped by the workpiece tensioning regions, it is drawn through a gap therebetween.

[0042] For example, the main forming tool with the main anvil tool may be configured to form a respective basal bend between adjacent basal regions (e.g. by clamping the sheet metal workpiece between respective tool surfaces of the main anvil tool and the main forming tool), the constraint then being applied by the main forming tool with the main anvil tool on the bent workpiece. Additionally, or alternatively, during the deformation of the first and second sidewall portions with respect to the first and second basal regions a first sidewall bend may be formed between the first sidewall portion and the first basal region, and a second sidewall bend may be formed between the second sidewall portion and the second basal region, the first sidewall bend being offset from the second sidewall bend. When the third basal region is present, during the deformation of the third sidewall portion with respect to the third basal region a third sidewall bend may be formed between the third sidewall portion and the third basal region, the first sidewall bend also being offset from the third sidewall bend.

[0043] For example, the main anvil tool may comprise a sidewall. In such a case, the sidewall of the main anvil tool may constrain at least a part of the first surfaces of the sidewall portions of the workpiece during the directing step; and the sidewall of the main anvil tool may constrain at least a part of the first surface of the first fold region during the step of sliding the auxiliary forming tool along the first fold region. When a third basal region is present, the sidewall of the main anvil tool also constrains at least a part of the first surface of the second fold region during the step of sliding the auxiliary forming tool along the second fold region. The main anvil tool sidewall may be substantially planar. Alternatively, when offset first and second sidewall bends are formed, and optionally offset first and third sidewall bends are formed, the main anvil tool sidewall may have a respective step extending in the axis of movement corresponding to the location each offset.

[0044] For example, the main anvil tool may be configured such that the final shape of any one, any two or all three of the first, second and third (if present) sidewall portions may include a respective planar major region which, on a cross-section perpendicular to the planar major region and containing the axis of movement of the auxiliary forming tool, deviates from the axis of movement by 1 ° or more, and preferably 8659351

[0045] 9 by 2° or 3° more. The height of such a planar major region measured along the axis of movement of the auxiliary forming tool may be at least 50 mm, and preferably at least 100 mm.

[0046] For example, the main anvil tool and the auxiliary anvil tool may each be connected to a first press plate, at least one of the main anvil tool and the auxiliary anvil tool being movably connected to the first press plate. When the auxiliary anvil tool is movably connected to the first press plate, the first press plate and the auxiliary anvil tool may be configured such that the auxiliary anvil tool’s first fold contact region, its first workpiece tensioning region and optionally its second workpiece tensioning region are movable independently of each other.

[0047] For example, the main forming tool and the auxiliary forming tool may each be connected to a second press plate, at least one of the main forming tool and the auxiliary forming tool being movably connected to the second press plate. When the auxiliary forming tool is movably connected to the second press plate, the second press plate and the auxiliary forming tool may be configured such that the auxiliary forming tool’s first fold contact region, its first workpiece tensioning region and optionally its second workpiece tensioning region are movable independently of each other.

[0048] The above method (otherwise termed herein an “Improved-Folding-Shearing” method) may allow for production of a formed sheet metal structure which requires minimal or no trimming after forming, in comparison to e.g. production of the same part via a deep drawing process. Additionally, the above method may allow for reduced metal waste whilst also maintaining satisfactory sheet qualities (e.g. reducing or avoiding unwanted material deformation such as wrinkling or tearing, and reducing or eliminating springback).

[0049] The precise shape of the bent base and the one or more sidewalls extending therefrom is not particularly limited, and may take a number of different forms depending on the specific forming process and the desired final shape of the product. In some embodiments, the sidewall(s) may be substantially planar, whereas in other embodiments both the base and the sidewall(s) may be bent, and further whereas in other embodiments the base may be substantially planar and the sidewall(s) may be bent. In some embodiments, the sidewall(s) extend substantially perpendicularly from the base, whereas in other embodiments the sidewall(s) may be at a different angle(s) to the base.

[0050] The term “basal region” is here used to define a region of the sheet metal workpiece that is a planar, base-like region. The basal region may undergo little or no bending and / or deformation during the forming process. In other words, the basal region may be a region of the workpiece which, during the forming operation, remains unchanged from its original size and shape. In some alternative forming processes, the basal region may undergo some shear deformation. The size and shape of the basal region is not particularly limited and may be selected as appropriate given the intended form of the formed sheet metal structure.

[0051] The precise nature of the further deformation of the fold region during the step of progressively sliding the forming tool along the fold region is not particularly limited and will depend on the specific forming process and the desired final shape of the product. The shear material transfer in the fold region may 8659351

[0052] 10 occur via material transfer from the fold region to at least one sidewall portion and / or material transfer into the fold region from at least one sidewall portion. However, in some embodiments, the shear material transfer in the fold region may additionally or alternatively occur via shear material transfer to or from a basal region of the sheet.

[0053] Material transfer from the fold region to at least one sidewall portion may provide for improved sidewall formation where the first surface of the sheet is concave between the adjacent basal regions. By allowing for such material transfer, it may be possible to create formed sheet metal structures with non-planar bases of a variety of shapes with little or no material thinning or thickening in the sidewalls, thus helping to reduce the occurrence of wrinkling and / or tearing during the forming process.

[0054] The anvil tool(s) and / or the forming tool(s) may comprise a rounded tool surface. The rounded tool surface of the anvil tool may be complementary to that of the forming tool. For example, the curvature of the rounded tool surface of the anvil tool may be opposite to the curvature of the rounded tool surface of the forming tool.

[0055] The terms “sidewall” and “sidewall portion” are used herein with respect to the workpiece to generally define a portion of the workpiece which forms a sidewall with respect to a basal region of the sheet. In other words, it is a portion of the sheet which is inclined, or is intended to be made inclined during the manufacturing process, relative to a basal region of the sheet in such a way as to form a sidewall. The bending / folding performed to form such sidewall portions may be partially elastic or may be fully plastic. In some cases, folding may occur along a fold line adjacent the basal region of the sheet. Such fold line may define an edge of the basal region. The number of sidewall portions may be selected as appropriate given the desired final shape of the formed sheet metal structure. As discussed above, there may be at least first and second sidewall portions. Preferably the sidewall portion(s) respectively extend from the basal region (e.g. from a fold line defining an edge of the basal region) to the edge(s) of the sheet metal workpiece.

[0056] Preferably, the sheet metal working apparatus is retrofittable to existing press-lines. For example, the bending stage could be performed by existing tools presently used in part of deep-drawing processes.

[0057] Preferably, the main anvil tool and the auxiliary anvil tool, and the main forming tool and the auxiliary forming tool are interchangeable for further anvil tools and further forming tools respectively.

[0058] In a third aspect, the present invention provides a kit comprising the sheet metal working apparatus of the second aspect and one or more further anvil tools and one or more further forming tools.

[0059] The invention includes the combination of the aspects and optional features described except where such a combination is clearly impermissible or expressly avoided.

[0060] Summary of the Figures

[0061] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which: 8659351

[0062] 11

[0063] Figures 1A - 1 F shows consecutive process steps in a method of manufacturing a formed sheet metal structure having a non-planar base and sidewalls extending therefrom;

[0064] Figures 2A - 2F shows consecutive process steps in a method of manufacturing a formed sheet metal structure having a non-planar base and sidewalls extending therefrom, and some of the sheet metal working apparatus used in said method;

[0065] Figures 3A - 3F shows consecutive process steps in a method of manufacturing a formed sheet metal structure having a non-planar base and sidewalls extending therefrom, and the sheet metal working apparatus used in said method;

[0066] Figures 4A and 4B show respectively front and side views of a target workpiece geometry;

[0067] Figure 5A shows a front view of a workpiece having the geometry of Figures 4A and 4B towards the end of a known folding-shearing process, and Figure 5B shows a front view of a workpiece having this geometry towards the end of an “Improved-Folding-Shearing” process;

[0068] Figures 6A and 6B show respective maps of amount (measured in mm) of springback superimposed on front views of the workpieces of Figures 5A and 5B at completion of the respective processing;

[0069] Figures 7A and 7B show respectively front and side views of a further target workpiece geometry;

[0070] Figures 8A and 8B show respectively front and side views of a workpiece having the geometry of Figures 4A and 4B towards the end of a known folding-shearing process, and Figures 8C and 8D show respectively front and side views of a workpiece having this geometry towards the end of an “Improved- Folding-Shearing” process;

[0071] Figure 9A shows a cross-section through a main anvil tool 310 and ‘U’-shaped workpiece, and Figure 9B shows a transverse cross-section corresponding to Figure 9A in which planar secondary tool surfaces of Figure 9A are exchanged for smoothly curved secondary tool surfaces.

[0072] Detailed Description of the Invention

[0073] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0074] The process described herein can be understood as “Improved-Folding-Shearing”. The process may be used for the deformation of sheet metal blanks into the shell shapes currently made by deep-drawing (such as cans, boxes or car body parts) with a reduced need for trimming after shaping.

[0075] The process will now be described with reference to Figures 1 - 4, each of which contains several subfigures that illustrate the shape of the sheet metal structure, and in some cases the shape and position of sheet metal working apparatus, at different stages of the process of manufacturing a formed sheet metal structure through “Improved-Folding-Shearing”.

[0076] Figures 1A - 1 F, progressing from Figure 1 A to Figure 1 F in order, illustrate the shape of a sheet metal structure 1 at sequential stages in the present “Improved-Folding-Shearing” process. 8659351

[0077] 12

[0078] The process starts initially with a flat sheet of metal, as shown in Figure 1 A, and the final formed sheet metal structure comprises a planar sidewall descending from a non-planar base of the workpiece at about 90°, as shown in Figure 1 F. However, an advantage of the process is that it is able to produce a planar sidewall even when the sidewall descends from the non-planar base at an angle that is not 90°, as explained in more detail below. A further advantage is that, by changing the amount and distribution of stored elastic stain energy in the workpiece, it enables better control of springback in the workpiece and particularly in the sidewall.

[0079] In the first stage of the manufacturing process, a flat sheet metal workpiece 1 as shown in Figure 1A is provided. The sheet metal workpiece has first and second surfaces 3, 5 opposed to each other - here the first and second surfaces are lower (not visible) and upper faces of the sheet, respectively. The sheet has a peripheral edge 7. The shape of the sheet metal workpiece 1 , and the one or more peripheral edges 7 it has, are non-essential and may be selected as appropriate based on the shape of the formed sheet metal structure that it is desired to produce. The sheet metal workpiece 1 is located in a sheet metal working apparatus (not shown in Figures 1A - 1 F).

[0080] Figure 1 B shows the step of bending the workpiece 1 to form a first basal region 50 and a second basal region 60 that together form the base of the workpiece 1 . The first and second basal regions 50, 60 are individually substantially planar, but separated by a basal bend 56 positioned between them. In Figure 1 B, the bending of the workpiece 1 is such that the first surface 3 of the workpiece 1 is concave between the first basal region 50 and the second basal region 60 i.e. the angle between the basal regions 50, 60 perpendicular to the first surface 3 is less than 180°. Extending from the first basal region 50 is a first sidewall portion 51 , which extends to the peripheral edge 7 of the workpiece 1 . Equivalently, extending from the second basal region 60 is a second sidewall portion 61 , which also extends to the peripheral edge 7 of the workpiece 1 . At the stage shown in Figure 1 B, the first sidewall portion 51 and second sidewall portion 61 remain co-planar with their respective basal regions 50, 60, but are not co-planar with each other, having also been bent as part of the step forming the first and second basal regions 50, 60.

[0081] In a following step of the process, illustrated by Figure 1C, the first and second sidewall portions 51 , 61 are deformed with respect to the first and second basal regions such as to no longer be co-planar with their respective basal regions 50, 60. In the case of Figure 1C, the sidewall portions 51 , 61 are deformed in a downward direction such that the first surface 3 of the workpiece 1 is concave between the base and the sidewall (i.e. the angle between the first surface 3 in the first basal region 50 and the first surface 3 in the first sidewall portion 51 is less than 180° and the angle between the first surface 3 in the second 5 basal region and the first surface 3 in the second sidewall portion 61 is less than 180°). A sidewall bend 57 forms between the basal regions 50, 60 and their corresponding sidewall portions. In the process of deforming the first and second sidewall portions 51 , 61 , a fold region 55 is formed that approximately corresponds to the basal bend 56. In the case of the workpiece 1 in Figures 1A - 1 F, the basal bend 56 is concave with respect to the first surface 3 and thus the fold region 55 is where there will be excess material present in the workpiece when the sidewall portions 51 , 61 are deformed. The fold region 55 in 8659351

[0082] 13

[0083] Figures 1 C - 1 F is the location where primary buckling / wrinkling is prone to occurring absent the present method.

[0084] Figure 1 D illustrates a stage of the process where a significant proportion of each of the sidewall portions 51 , 61 has been deformed and now lie at the desired angle with respect to the basal regions 50, 60, which in Figure 1 D is approximately 90° when measured from the first surface 3 of the workpiece 1 - these regions of the sidewall portions 51 , 61 can be referred to as ‘developable regions’. However, the fold region 55, which incorporates non-developable regions of the sidewall portions 51 , 61 , forms a raised ‘beak’ shape where the sidewall has not developed due to a change in the surface area of the shape required to transition between the un-deformed sidewall state illustrated in Figure 1 B to the deformed sidewall state shown in Figure 1 F. In addition, extending from either side of the fold region 55 along the peripheral edge 7, further non-developable regions 52, 62 of the sidewall portions 51 , 61 are gripped such as to be held away from the desired angle with respect to the basal regions 50, 60.

[0085] In the case of the workpiece at the stage shown in Figure 1 D, the fold region 55 forms such that the metal in the fold region 55 has undergone minimal stretching and / or compression. Deforming the sidewall portions 51 , 61 to the stage shown in Figure 1 D does not result in a change of the thickness of the workpiece 1 , or only changes to a minimal extent, for example not more than approximately ±10%. In order to provide the final formed metal sheet structure illustrated in Figure 1 F, further deformation of the fold region 55 and gripped regions 52, 62 is required to eliminate the raised part of the fold region 55 and the regions 55, 52, 62 into conformity with the deformed sidewall portions 51 , 61. However, such further deformation is liable to cause primary buckling / wrinkling of the sheet metal workpiece 1 in the fold region 55 due to the reduction in surface area required there, and secondary buckling / wrinkling in other parts of the workpiece such as the sidewall portions 51 , 61 to either side of the fold region 55. Such secondary buckling / wrinkling can be most liable to form when the sidewall portions 51 , 61 descend from the basal regions 50, 60 at an angle that is not 90°, i.e. when the normal to a given sidewall portion is not orthogonal to the axis of movement of the auxiliary forming tool 30 discussed below in respect of Figures 3A - 3F.

[0086] During a subsequent step of the manufacturing process, a forming tool (not shown) is progressively slid along the fold region 55 to cause shear material transfer therein, allowing for further deformation of the fold region 55 without primary buckling / wrinkling the workpiece 1 in this region. At the same time, the forming tool slidingly grips the sidewall portions 51 , 61 to either side of the fold region 55 at the regions 52, 62, thereby applying tension to the adjacent sidewall portions 51 , 61 to prevent secondary buckling / wrinkling. Figure 1 E illustrates a stage of the process where this step is partly completed. An upper portion of the raised fold region 55 present in Figure 1 D has been flattened in Figure 1 E to form the sidewall without primary wrinkling / buckling by shear material transfer from the fold region to the sidewall portions 51 , 61. Moreover, this transfer has not produced any secondary wrinkling / buckling in the sidewall portions 51 , 61 to either side of the fold region 55, and at the illustrated stage of the process the regions 52, 62 are released from the grip of the forming tool and are now at the desired angle with respect to the basal regions 50, 60. A lower portion of the fold region 55 is still raised in Figure 1 E and requires further 8659351

[0087] 14 shear material transfer in order for the fold region 55 to conform with the developed sidewall portions 51 ,

[0088] 61.

[0089] The formed sheet metal structure at the end of the manufacturing process is shown in Figure 1 F, comprising a continuous sidewall extending downward from the base, the base being non-planar (i.e. having two basal regions that are not co-planar with each other) but the sidewall extending from that base being substantially planar across the sidewall portions 51 , 61 (at least in the case of the example illustrated in Figure 1 F). Whilst the sidewall in Figure 1 F is substantially planar across the sidewall portions 51 , 61 , a sidewall formed according to the present process may be non-planar across the sidewall portions 51 , 61 ; however, the greater the degree to which the sidewall portions deviate from being planar, the greater the amount of stretching or shrinking of the workpiece that the present process would need to accommodate. Advantageously, the formed sheet metal structure at the end of the manufacturing process is shown in Figure 1 F requires minimal or no trimming after forming, in comparison to e.g. production of the same part via a deep drawing process. Additionally, the above method may allow for reduced metal waste whilst also maintaining satisfactory sheet qualities (e.g. reducing or avoiding unwanted material deformation such as wrinkling or tearing).

[0090] The process described in WO2024 / 079349 A1 can sometimes have difficulties forming a planar sidewall portion which, on a cross-section perpendicular to the sidewall portion and containing the axis of movement of the auxiliary forming tool, deviates significantly (e.g. 1 ° or more, 2° or more, or 3° or more) from the axis of movement of the forming tool due to the secondary buckling / wrinkling that can occur in the sidewall portion as a result of the deviation. In general, the amount of deviation that can be tolerated decreases with the height of the sidewall portion, e.g. 2° or more of deviation may be problematic over a height of 100 mm, while 1 ° or more of deviation may be problematic over a height of 150 mm. However, advantageously the “Improved-Folding-Shearing” process described above is able to suppress such secondary buckling / wrinkling and is thus particularly useful when such deviations are present. It can also help to reduce or eliminate springback in the final structure.

[0091] Figures 2A - 2F, progressing from Figure 2A to Figure 2F in order, illustrate the shape of a sheet metal workpiece 1 at sequential stages in the present “Improved-Folding-Shearing” process and the interaction of the sheet metal workpiece 1 with some of the sheet metal working apparatus that may be used in that process. In particular, features of a main anvil tool and an auxiliary anvil tool are shown, in addition to the workpiece.

[0092] The shape of the sheet metal structure 1 in each of Figures 2A - 2F is the same as the shape of the sheet metal structure 1 in each of Figures 1A - 1 F, respectively. Thus, a detailed discussion of the shape of the sheet metal structure 1 in each of Figures 2A - 2F is omitted.

[0093] In Figure 2A, a main anvil tool 10 has been provided for use in forming the sheet metal structure. The main anvil tool 10 has a tool surface 15 (partly obscured by the sheet metal workpiece 1 in Figure 2A) to be brought into contact with the first (lower) surface 3 of the sheet metal workpiece 1 to constrain at least a part of the first surface 3. The tool surface 15 of the main anvil tool 10 is an upper surface of the anvil tool 10 in Figure 2A. The main anvil tool 10 further comprises a sidewall 16 extending from the tool 8659351

[0094] 15 surface 15 and in Figure 2A the edge at which the sidewall 16 and tool surface 15 meet is bevelled to aid the smooth deformation of the sidewall portions 51 , 61 at a later step of the process. Also shown in Figure 2A is an auxiliary anvil tool 20, which has a central part providing a primary tool surface 25 for contact with and constraint of at least a part of the first (lower) surface 3 of the sheet metal workpiece 1. The auxiliary anvil tool 20 also has wings extending away from either side of the central part to provide secondary tool surfaces 26, 27 which form workpiece tensioning regions of the auxiliary anvil tool. In Figure 2A these wings are shown as fixed extensions from the sides of the central part in which the secondary tool surface 26, 27 are continuations of the primary tool surface 25. However, in variants of the process, any given secondary tool surface 26, 27 may be non-continuous with the primary tool surface 25, i.e. spaced therefrom a by a gap. Additionally, or alternatively, the part of the auxiliary anvil tool 20 that forms any given secondary tool surface can be separate from the central part of the auxiliary anvil tool 20 such that in the latter stages of the process discussed below with reference to Figures 2E and 2F, the separate parts are independently withdrawable at different rates from underneath the sheet metal workpiece.

[0095] The main and auxiliary anvil tools 10, 20 may both be connected to a first press plate for attachment to a metal forming press. As described below in relation to Figure 2E, the auxiliary anvil tool 20 is movable relative the main anvil tool 10; thus, where the main and auxiliary anvil tool 10, 20 are connected to a first press plate, at least one of the anvil tools 10, 20 is movably connected to the first press plate. The movable connection of an anvil tool to the first press plate may, for example, be through a hydraulically or mechanically actuated ram.

[0096] In Figure 2B, the sheet metal workpiece 1 has been bent to form the first and second basal regions 50, 60 as discussed above in relation to Figure 1 B. Figure 2B illustrates how the workpiece 1 is bent to form the first and second basal regions 50, 60 such that when the first surface 3 of the bent workpiece 1 is in contact with the tool surface 15 of the main anvil tool 10, the first and second basal regions 50, 60 are congruent with at least a portion of the tool surface 15 such that the tool surface 15 constrains the basal regions 50, 60 against further deformation. The auxiliary anvil tool 20 is provided adjacent the sidewall 16 of the main anvil tool 10 and its central part that forms the primary tool surface 25 takes the approximate form of an oblique triangular pyramid, optionally being truncated, with an apex laterally aligned with the bend 56. The secondary tool surfaces 26, 27 provided by the wings on either side of the central part slope downwardly away from the sidewall 16 of the main anvil tool 10.

[0097] In a following step of the process, illustrated by Figure 2C, the first and second sidewall portions 51 , 61 are deformed with respect to the first and second basal regions 50, 60 such as to no longer be co-planar with their respective basal regions 50, 60. A sidewall bend 57 forms that is congruent to the bevelled edge between the tool surface 15 and sidewall 16 of the main anvil tool. The first and second sidewall portions 51 , 61 are deformed about the edge between the tool surface 15 and the sidewall 16 of the main anvil tool 10 such that the developable regions of the sidewall portions 51 , 61 of the sheet metal workpiece 1 approach the sidewall 16 of the main anvil tool 10. The fold region 55 that corresponds to the bend 56 forms due to the excess material present in the workpiece at this location as the sidewall 8659351

[0098] 16 portions 51 , 61 are deformed. This deformation is continued until the stage shown in Figure 2D is reached, wherein the developable regions of sidewall portions 51 , 61 has been deformed and the first surface 3 in these regions is now in contact with, and constrained by, the sidewall 16 of the main anvil tool 10. In the case of the main anvil tool 10 illustrated in Figure 2D, the sidewall 16 is substantially perpendicular to the tool surface 15 and resultingly the developable regions of the sidewall portions 51 , 61 at the stage shown in Figure 2D are substantially perpendicular to the basal regions 50, 60. However, the angle of the sidewall 16 relative to the tool surface 15 is not particularly limited and may be set such as to provide the desired angle between the base and sidewall in the formed sheet metal structure. The deformation of the sidewall portions 51 , 61 is achieved by contacting the sheet metal workpiece with the main anvil tool 10 and an auxiliary forming tool (not shown).

[0099] Figure 2D also illustrates that at least a part of the first surface 3 of the sheet metal workpiece 1 has come into contact with, and is constrained by, the primary tool surface 25 of the auxiliary anvil tool 20 at the fold region 55. The fold region 55 is supported by the auxiliary anvil tool 20 such that it does not undergo deformation that would resulting in primary buckling / wrinkling of the sheet metal workpiece 1 in the fold region 55 whilst deforming the sidewall portions 51 , 61. Typically, the auxiliary anvil tool 20 prevents buckling in the fold region 55 by providing a primary tool surface 25 that constrains the fold region 55 such that there is minimal stretching and / or compression of the material in the fold region 55 during deformation of the sidewall portions 51 , 61 and such that the thickness of the sheet metal workpiece 1 does not change substantially whilst deforming the developable regions of the sidewall portions 51 , 61 (i.e. the thickness of the sheet metal workpiece 1 does not change from the stage shown in Figure 2B to the stage shown in Figure 2D, or only changes to a minimal extent, for example not more than approximately ±10%).

[0100] In addition, Figure 2D illustrates that at least a further part of the first surface 3 of the sheet metal workpiece 1 has come into contact with, and is constrained by, the secondary tool surfaces 26, 27 on either side of the primary tool surface 25. Specifically, regions 52, 62 running along the peripheral edge 7 are slidingly gripped between the secondary tool surfaces 26, 27 and corresponding surfaces of the auxiliary forming tool, thereby tensioning adjacent regions of the sidewall portions 51 , 61 and preventing secondary buckling / wrinkling of the sheet metal workpiece.

[0101] Figure 2E then illustrates the workpiece 1 part way through a later step of the manufacturing process, in which the auxiliary forming tool (not shown) is progressively slid along the fold region 55 to cause shear material transfer therein and bring the fold region 55 and the gripped regions 52, 62 into conformity with the developed regions of the sidewall portions 51 , 61 .

[0102] In order to bring the fold region 55 into conformity with the developed sidewall portions 51 , 61 (for example, making the fold region 55 co-planar with the developed regions of the sidewall portions 51 , 61 as in Figure 2F) without primary buckling / wrinkling the material in the fold region 55, shear material transfer is required, with material being transferred from the fold region 55 into at least one of the sidewall portions, and potentially both sidewall portions 51 , 61 and / or into one or both basal regions 50, 60 adjacent the fold region 55. In Figure 2D, the fold region 55 is constrained by the primary tool surface 25 8659351

[0103] 17 of the auxiliary anvil tool 20, and thus the fold region 55 cannot be brought into conformity with the adjacent sidewall portions 51 , 61 . In order to allow the fold region 55 to be deformed, the auxiliary anvil tool 20 must be withdrawn from underneath the fold region 55 such that it no longer constrains the whole of it.

[0104] In order to allow controlled deformation of the fold region 55, the auxiliary anvil tool 20 is withdrawn from underneath the fold region 55 concurrently with the auxiliary forming tool (not shown) being slid along the fold region 55, such that at a given time, only a small portion of the fold region 55 that is not constrained by the auxiliary anvil tool 20 can be deformed by the auxiliary forming tool. The portion of the fold region 55 where it is not constrained by the auxiliary anvil tool 20 is brought into conformity with the adjacent developed regions of the sidewall portions 51 , 61 through shear material transfer out of the fold region 55 and into the sidewall portions 51 , 61 (and potentially the adjacent basal regions 50, 60). In Figure 2E, this controlled deformation of the fold region 55 is partly complete, the upper portion of the raised fold region 55 present in Figure 2D has been flattened in Figure 2E to conform with the developed sidewall portions 51 , 61 without primary buckling / wrinkling. In Figure 2E the auxiliary anvil tool 20 is lower with respect to the main anvil tool 10 and the workpiece 1 than it is in Figure 2D.

[0105] During at least initial stages of this shear material transfer, the regions 52, 62 are slidingly gripped between the secondary tool surfaces 26, 27 of the auxiliary anvil tool 20 and the corresponding surfaces of the auxiliary forming tool, and thus tension is continuously applied to the developed sidewall portions 51 , 61 to prevent secondary buckling / wrinkling therein. As sliding progresses, the sidewall portions 51 , 61 of the workpiece 1 , on leaving the gripped regions 52, 62, are developed into conformity with the sidewall 16 of the main anvil tool 10, and eventually (as shown in Figure 2E) the gripped regions 52, 62 disappear.

[0106] The sliding step is continued, causing the raised portion of the fold region 55 to gradually reduce in size, until the material in the fold region 55 is fully drawn through the forming tool and the shape of the formed sheet metal structure shown in Figure 2F is arrived at. The formed sheet metal structure in Figure 2F comprises a continuous sidewall extending downward from the base, the base being non-planar (i.e. having two basal regions that are not co-planar with each other) but the sidewall extending from that base being substantially planar (in the case of the example illustrated in Figure 2F). Here the sidewall lies in a plane offset by about 90° from the planes of both the basal regions. Advantageously, the formed sheet metal structure at the end of the manufacturing process is shown in Figure 2F requires minimal or no trimming after forming, in comparison to e.g. production of the same part via a deep drawing process. Additionally, the above method may allow for reduced metal waste whilst also maintaining satisfactory sheet qualities (e.g. reducing or avoiding unwanted material deformation such as wrinkling or tearing).

[0107] Figures 3A - 3F, progressing from Figure 3A to Figure 3F in order, illustrate the shape of a sheet metal workpiece 1 at sequential stages in the present “Improved-Folding-Shearing” process and the interaction of the sheet metal structure 1 with some of the sheet metal working apparatus that may be used in that process.

[0108] The shape of the sheet metal structure 1 , main anvil tool 10 and auxiliary anvil tool 20 in Figures 3A - 3F is the same as the shape of the sheet metal structure 1 , main anvil tool 10 and auxiliary anvil tool 20 in 8659351

[0109] 18

[0110] Figures 1A - 1 F and Figures 2A - 2F. Thus, a detailed discussion of the shape of the sheet metal structure 1 , main anvil tool 10 and auxiliary anvil tool 20 in each of Figures 3A - 3F is omitted.

[0111] In Figure 3A, the auxiliary forming tool 30 has been provided for use in forming the sheet metal structure. The auxiliary forming tool 30 has a tool surface 35 to be brought into contact with the second (upper) surface 5 of the sheet metal workpiece 1 to constrain at least a part of the second surface 5. The tool surface 35 is a lower surface of the forming tool 30 in Figure 3A. Also shown in Figure 3A is a main forming tool 40, which also has a tool surface 45 for contact with and constrain at least a part of the second (upper) surface 5 of the sheet metal workpiece 1 . The tool surface 15 of the main anvil tool 10 and the tool surface 45 of the main forming tool 40 are shaped such that they are approximately congruent with each other. The manufacturing process may utilise the main forming tool 40 to exert greater control over the forming of the sheet metal workpiece, as is described below in relation to Figures 3A and 3B.

[0112] The main 40 and auxiliary 30 forming tools may both be connected to a second press plate for attachment to a metal forming press. As described below in relation to Figures 3B and 3C, the main forming tool 40 is movable relative the auxiliary forming tool 30; thus, where the main and auxiliary forming tools 30, 40 are connected to a second press plate, at least one of the forming tools 30, 40 is movably connected to the second press plate. The movable connection of a forming tool to the second press plate may, for example, be through a hydraulically or mechanically actuated ram.

[0113] Between the stages shown in Figures 3A and 3B, the flat sheet metal workpiece 1 in Figure 3A is bent to form the first basal region 50 and the second basal region 60, which together form the base of the workpiece 1. In Figure 3B, the base of the workpiece 1 is clamped between the main anvil tool 10 and the main forming tool 40, such that the base is fixed in position relative the main anvil tool 10 and main forming tool 40. This secures the sheet metal workpiece 1 ahead of further forming steps, meaning that the basal regions 50, 60 are unable to move relative to the main anvil tool 10, which prevents the sheet metal workpiece being incorrectly deformed during subsequent steps of the process due to movement of the basal regions. It is possible for the step of bending the workpiece 1 to form the first basal region 50 and second basal region 60 to be executed by the step of clamping the workpiece 1 between the respective tool surfaces 15, 45 of the main anvil tool 10 and main forming tool 40. Executing the bending step in this manner is beneficial in that the bend 56 formed in the sheet metal workpiece 1 will conform exactly with the shape of the respective tool surfaces 15, 45. The step of clamping the base of the workpiece 1 between the main anvil tool 10 and main forming tool 40 is conducted by moving the main anvil tool 10 and main forming tool 40 towards each other with the workpiece 1 positioned therebetween. The main anvil tool 10 and main forming tool 40 contact the workpiece 1 and continue to be moved towards each other until the basal regions 50, 60 are in contact with, and congruent to, the tool surfaces 15, 45. The main anvil tool 10 and main forming tool 40 continue to move towards each other until a clamping pressure of greater than or equal to a first threshold clamping pressure is exerted on the portion of the sheet metal workpiece 1 interposed between the respective tool surfaces 15, 45 of the tools 10, 40. The first threshold clamping pressure may be set according to the Young’s modulus and yield stress of 8659351

[0114] 19 the material of the sheet metal workpiece 1 and thus how much pressure will need to be exerted on the workpiece 1 during the subsequent deforming steps of the manufacturing process. Typically, the first threshold clamping pressure is greater than or equal to 100 kPa. Optionally, the clamping pressure may not exceed the yield stress of the material forming the workpiece 1 , because too large a clamping pressure may result in unwanted thinning and tearing of parts of the workpiece. The clamping pressure exceeding the yield stress of the material forming the workpiece 1 may result in unwanted and unnecessary forging of the workpiece. Practically, an upper limit of the clamping pressure may be set according to the upper limit of gas springs or a hydraulic cushion exerting the clamping pressure.

[0115] As illustrated in Figure 3B, the sidewall portions 51 , 61 of the workpiece 1 extend to one side of the portion of the workpiece 1 clamped between the main anvil tool 10 and the main forming tool 40, with the auxiliary anvil tool 20 positioned underneath the sidewall portions 51 , 61.

[0116] In a following step of the process, illustrated by Figures 3C and 3D (corresponding approximately to the shape of the workpiece 1 in Figures 1C and 2C), the auxiliary forming tool 30 is brought into contact with the first and second sidewall portions 51 , 61 to deform them with respect to the first and second basal regions 50, 60. Specifically, Figure 3C illustrates the point of the manufacturing process at which the auxiliary forming tool is positioned above the second surface 5 of the workpiece 1 and moves downwards relative the workpiece 1 and main anvil tool 10 such that the tool surface 35 of the auxiliary forming tool 30 contacts the second surface 5 of the workpiece. Figure 3D then illustrates how the forming tool 30 continues to move downwards and in doing so, deforms the sidewall portions 51 , 61 thereby to reduce an angle between the first surface 3 in each sidewall portion 51 , 61 and the first surface 3 in that sidewall portion’s respective basal region 50, 60. A sidewall bend 57 forms that is congruent to the bevelled edge between the tool surface 15 and sidewall 16 of the main anvil tool. In the process of deforming the sidewall portions 51 , 61 , the fold region 55 in the workpiece 1 between the first and second sidewall portions 51 , 61 begins to form.

[0117] At the stage of Figure 3E, corresponding approximately to the shape of the workpiece 1 in Figures 1 D and 2D, the developable regions of the sidewall portions 51 , 61 have been deformed by the auxiliary forming tool 30 and are in contact with, and constrained by, the sidewall 16 of the main anvil tool 10 (see Figure 2D). The tool surface 35 of the auxiliary forming tool 30 in Figures 3A - 3F comprises an inverted ‘v’-shaped portion that, as Figure 3E illustrates, aligns with the shape of the primary tool surface 25 of the auxiliary anvil tool 20. As the sidewall portions 51 , 61 are deformed by the relative movement of the auxiliary forming tool 30 and the workpiece 1 , the fold region 55 is formed into a raised beak shape that comes into contact with, and is constrained by, both the inverted ‘v’-shaped portion of the tool surface 35 of the auxiliary forming tool 30 and the primary tool surface 25 of the auxiliary anvil tool 20. In addition, the tool surface 35 of the auxiliary forming tool 30 comprises secondary surface portions that extend from either side of the ‘v’-shaped portion. These secondary surface portions of the tool surface 35 form workpiece tensioning regions of the auxiliary forming tool 30 that are parallel with and correspond to the secondary tool surfaces 26, 27 of the auxiliary anvil tool 20. The relative movement of the auxiliary forming tool 30 and the workpiece 1 results in the regions 52, 62 of the sidewall portions 51 , 61 adjacent 8659351

[0118] 20 the peripheral edge 7 being trapped between the secondary surface portions of the tool surface 35 of the auxiliary forming tool 30 and the secondary tool surfaces 26, 27 of the auxiliary anvil tool 20.

[0119] As mentioned above with reference to Figure 2A, in variants of the process, any given secondary tool surface 26, 27 may be non-continuous with the primary tool surface 25. In this case, the corresponding secondary surface portion of the tool surface 35 may similarly be non-continuous with its ‘v’-shaped portion. As also mentioned above, the part of the auxiliary anvil tool 20 that forms any given secondary tool surface can be separate from the central part of the auxiliary anvil tool 20, and in this case the auxiliary forming tool 30 may also have corresponding separate parts, e.g. so that they can match the different rates of withdrawals of the separate parts of the auxiliary anvil tool 20.

[0120] The auxiliary forming tool 30 continues to move downwards until the fold region 55 is interposed between and fully contacting the auxiliary forming tool 30 and the auxiliary anvil tool 20. The downward movement of the forming tool 30 relative the workpiece 1 and the auxiliary anvil tool 20 clamps the fold region 55 between the respective tool surfaces 35, 25 of the auxiliary forming tool 30 and the auxiliary anvil tool 20. In addition, the regions 52, 62 of the sidewall portions 51 , 61 are interposed between and gripped by the secondary surface portions of the tool surface 35 of the auxiliary forming tool 30 and the secondary tool surfaces 26, 27 of the auxiliary anvil tool 20. The auxiliary forming tool 30 stops moving downwards when a clamping pressure of greater than or equal to a second threshold clamping pressure is exerted on the fold region 55 and the gripped regions 52, 62. The second threshold clamping pressure may be set according to the shear modulus of the material of the sheet metal workpiece 1 and thus how much pressure will need to be exerted on the workpiece 1 during the subsequent shearing deforming step of the manufacturing process. Typically, the second threshold clamping pressure is greater than or equal to 100 kPa. Optionally, the clamping pressure of the regions 55, 52, 62 may not exceed the yield stress of the material forming the workpiece 1 , because too large a clamping pressure may result in unwanted thinning and tearing of parts of the workpiece. The clamping pressure exceeding the yield stress of the material forming the workpiece 1 may result in forging of the workpiece. Practically, an upper limit of the clamping pressure may be set according to the upper limit of gas springs or a hydraulic cushion exerting the clamping pressure.

[0121] Figure 3F then illustrates the process of sliding the auxiliary forming tool 30 along the fold region 55 (and gripped regions 52, 62) to cause shear material transfer in the fold region 55, thereby further deforming the fold region 55 and bringing it into conformity with the developed regions of the sidewall portions 51 , 61 while maintaining tension in those regions, as discussed in relation to Figures 1 E, 1 F, 2E and 2F. Between Figures 3E and 3F, it is clear that both the auxiliary forming tool 30 and the auxiliary anvil tool 20 are concurrently slid downwards relative to the main anvil tool 10 and with the same velocity, such that material at the edge of the raised fold region 55 is drawn out of the clamped portion and deformed to conform with the developed sidewall portions 51 , 61 , whilst the remainder of the raised portion of the fold region 55 remains clamped between the two tools 20, 30. Similarly, material at the edge of the gripped regions 52, 62 is drawn out and deformed to conform with the developed sidewall portions 51 , 61. The auxiliary forming tool 30 and auxiliary anvil tool 20 continue to move downwards together, reducing the 8659351

[0122] 21 size of the raised portion of the fold region 55 as more material is drawn out of the clamped region, until the material of the fold region 55 is fully drawn through the forming tool and the fold region 55 is in conformity with the sidewall portions 51 , 61 . Likewise, the downwards movement reduces the sizes of the gripped regions 52, 62 until the material of these regions is also fully drawn out. The movement of the auxiliary forming tool 30 and the auxiliary anvil tool 20 during the sliding step may be controlled independently of each other (albeit such that they move concurrently and with the same velocity), or the movement of the auxiliary anvil tool 20 may be caused by the auxiliary forming tool 30 transmitting a sufficiently large pressure onto the auxiliary anvil tool 20 (through the workpiece 1 clamped therebetween, or through contact between the tools that lies outside the workpiece perimeter) that the auxiliary anvil tool 20 is urged to move downward with the forming tool 30.

[0123] Although in the example of Figures 1 A - 1 F, 2A - 2F and 3A - 3F the sheet metal workpiece 1 has two gripped regions 52, 62, one on either side of the raised fold region 55, in other examples it may be necessary to provide a gripped region on only one side of a given raised fold region, e.g. because secondary buckling / wrinkling and / or springback of the workpiece is only liable to occur on that side. Accordingly, in such examples the auxiliary forming tool and the auxiliary anvil tool may have workpiece tensioning regions arranged for tensioning a sidewall portion on one side of a fold region, but not on the other side.

[0124] In the example of Figures 1 A - 1 F, 2A - 2F and 3A - 3F, the sheet metal workpiece 1 has only one raised fold region 55 along peripheral edge 7. However, in other examples the workpiece can have plural such regions along a given edge. In this case, the auxiliary forming tool and the auxiliary anvil tool may have workpiece tensioning regions arranged for tensioning a sidewall portion located between adjacent fold contact regions on that edge.

[0125] In the example of Figures 1 A - 1 F, 2A - 2F and 3A - 3F, the basal bend 56 between the basal regions 50, 60 produced a shrink or stretch zone and thus was a factor in the production of the fold region 55. However, such zones can also be formed under other circumstances. Figures 4A and 4B show respectively front and side views of a target workpiece geometry in which the workpiece 101 has first basal region 150, a second basal region 160 on one side of the first basal region, and a third basal region 170 on the other side of the first basal region. First 151 , second 161 and third 171 sidewall portions extend from the respective basal regions to an edge 107. A first sidewall bend 157 is formed between the first basal region 150 and the first sidewall portion 151 , a second sidewall bend 167 is formed between the second basal region 160 and the second sidewall portion 161 , and a third sidewall bend 177 is formed between the third basal region 170 and the third sidewall portion 171 . The first 150, second 160 and third 170 basal regions are coplanar, but the first sidewall portion 151 is recessed relative to the second 161 and third 171 sidewall portions. In other words, the first sidewall bend 157 is offset from the second sidewall bend 167, and the first sidewall bend 157 is also offset from the third sidewall bend 177. The sidewall of the main anvil tool (not shown) is not planar but rather is stepped to produce the recess and these offsets. The offsets produce shrink or stretch zones which can be countered by adopting a similar approach to that described above in respect of Figures 1 A - 1 F, 2A - 2F and 3A - 3F, i.e. producing a 8659351

[0126] 22 fold region at each offset and using an auxiliary anvil tool and an auxiliary forming tool to slide along each fold region and perform controlled deformation by shear material transfer. In addition, however, the sidewalls portions 151 , 161 , 171 are slanted relative to the axis of movement of the auxiliary forming tool by an angle of 3°, the height of the sidewall portions being 100 mm.

[0127] To illustrate the effectiveness of the “Improved-Folding-Shearing” process, Figure 5A shows a front view of a workpiece 101 after an attempt to make the target workpiece geometry of Figures 4A and 4B using the approach described in WO2024 / 079349 A1 (i.e. processing without workpiece tensioning regions in the auxiliary forming and anvil tools to control secondary buckling / wrinkling). In Figure 5A the workpiece 101 has undergone stages 1 to 3 of the following process stages and is close to completing stage 4:

[0128] 1. A main forming tool is clamped to a main anvil tool over the coplanar first 150, second 160 and third 170 basal regions.

[0129] 2. The workpiece is bent downwards along the first 157, second 167, third 177 sidewall bends using an auxiliary forming tool so as to begin to form the first 151 , second 161 and third 171 sidewall portions corresponding to the respective basal regions, with two fold regions also beginning to form corresponding to the offsets between adjacent sidewall bends.

[0130] 3. The auxiliary forming tool is directed further downwards so as to continue forming the sidewall portions 151 , 161 , 171 and fold regions, while an auxiliary anvil tool is provided with first 125 and second 126 primary tool surfaces for contact with and constraint of the workpiece at the two fold regions.

[0131] 4. The auxiliary forming tool and the auxiliary anvil tool are slid downwards relative to the main anvil tool so that, under shear material transfer, material at the edges of the fold regions is drawn out from the constraint of the auxiliary forming and anvil tools and deformed to conform with the developed sidewalls 151 , 161 , 171.

[0132] Towards the end of stage 4, as shown in Figure 5A, only small regions of the first primary tool surface 125 and the second primary tool surface 126 are still in contact with the workpiece. However, unacceptable secondary buckling / wrinkling 180 has occurred in the sidewall portions 151 , 161 , 171 adjacent the two fold regions due to the slanting of the sidewall portions over their height.

[0133] Figure 5B then shows a front view of a corresponding workpiece at a comparable point of the “Improved- Folding-Shearing” process. This process is similar to that described above in respect of Figure 5A except that the auxiliary anvil tool has plates that provide secondary tool surfaces 127 extending between the first 125 and second 126 primary tool surfaces, and also extending from the opposite sides of the first 125 and second 126 primary tool surfaces. The auxiliary forming tool also has plates that provide corresponding secondary tool surfaces, and together these secondary tool surfaces grip regions of the sidewall portions 151 , 161 , 171 at an angle to the sidewall of the main anvil tool, thereby tensioning adjacent developed regions of the sidewall portions 151 , 161 , 171 . Advantageously, this tensioning prevents the formation of secondary buckling / wrinkling 180 in the sidewall portions 151 , 161 , 171. 8659351

[0134] 23

[0135] Figure 6A and 6B then show respective maps of amount (measured in mm) of springback superimposed on the front views of the workpieces of Figures 5A and 5B at completion of the respective processing. Evidently, the tensioning of the sidewall portions 151 , 161 , 171 in the “Improved-Folding-Shearing” process reduces the amount of springback, particularly at the lower corners of the sidewall portions 161 , 171.

[0136] Figures 7A and 7B show respectively front and side views of a simpler, further target workpiece geometry having just one offset. Specifically, a workpiece 201 with the further target geometry has a first basal region 250 and an adjacent second basal region 260. First 251 and second 261 sidewall portions extend from the respective basal regions to an edge 207. A first sidewall bend 257 is formed between the first basal region 250 and the first sidewall portion 251 , and a second sidewall bend 267 is formed between the second basal region 260 and the second sidewall portion 261 . The first 250 and second 260 basal regions are coplanar, but the second sidewall portion 261 is recessed relative to the first sidewall portion 251 so that the first sidewall bend 257 is offset from the second sidewall bend 267. The sidewalls portions 251 , 261 are slanted relative to the axis of movement of the auxiliary forming tool by an angle of 3°, and the height of the sidewall portions is 100 mm.

[0137] To further illustrate the effectiveness of the “Improved-Folding-Shearing” process, Figure 8A shows a front view of a workpiece 201 after an attempt to make the further target geometry using the approach described in WO2024 / 079349 A1 (i.e. processing without workpiece tensioning regions in the auxiliary forming and anvil tools to control secondary buckling / wrinkling). In Figure 8A the workpiece 201 has undergone stages 1 to 3 of the following process stages and is at an early point in the stage 4:

[0138] 1 . A main forming tool is clamped to a main anvil tool 210 over the coplanar first 250 and adjacent second 260 basal regions.

[0139] 2. The workpiece is bent downwards along first 257 and second 267 sidewall bends using an auxiliary forming tool so as to begin to form the first 251 and second 261 sidewall portions corresponding to the respective basal regions, with a fold region also beginning to form corresponding to the offset between the adjacent sidewall bends.

[0140] 3. The auxiliary forming tool is directed further downwards so as to continue forming the sidewall portions 251 , 261 and fold region, while an auxiliary anvil tool provides a first primary tool surface 225 for contact with and constraint of the workpiece at the fold region.

[0141] 4. The auxiliary forming tool and the auxiliary anvil tool are slid downwards relative to the main anvil tool so that, under shear material transfer, material at the edges of the fold region is drawn out from the constraint of the auxiliary forming and anvil tools and deformed to conform with the developed sidewall portions 251 , 261 .

[0142] Towards the end of stage 4, as shown in Figure 7A, only a small region of the first primary tool surface 225 is still in contact with the workpiece. However, unacceptable secondary buckling / wrinkling 280 has occurred in the sidewall portions 251 , 261 adjacent the fold region due to the slanting of the sidewall portions over their height. In addition, referring to Figure 8B, which shows a side view of the workpiece, 8659351

[0143] 24 including an expanded view of the region around the first sidewall bend 257, some of the top surface of the main anvil tool 210 is no longer in contact with the workpiece due to the occurrence of a region 280 of a form of secondary buckling / wrinkling in the first basal region 250, otherwise known as “puckering”. The main cause of this puckering is the sloped first sidewall portion 251 which causes the auxiliary anvil and forming tools to be spaced away from the first sidewall bend 257 at the edge of the first basal region 250. This shows that secondary buckling / wrinkling can be a problem not only in sidewall portions but also in other parts of the workpiece.

[0144] Figures 8C and 8D then show similar views of a corresponding workpiece at a comparable point of the “Improved-Folding-Shearing” process. This process is similar to that described above in respect of Figures 8A and 8B except that the auxiliary anvil tool has plates that provide secondary tool surfaces 227 extending from its primary tool surface along the first 251 and second 261 sidewall portions. The auxiliary forming tool also has plates that provide corresponding secondary tool surfaces, and together these secondary tool surfaces grip regions of the first 251 and second 261 sidewall portions at an angle to the vertical portion of the respective sidewall of the main anvil tool 210, thereby better tensioning not only the sidewall portions but also the first basal region 250. Advantageously, this tensioning prevents the formation of puckering in the first basal region 250, which remains in close contact with the main anvil tool 210.

[0145] Sometimes it is found that by suitable adaptation of the tooling and process parameters in the approach described in WO2024 / 079349 A1 (i.e. processing without workpiece tensioning regions in the auxiliary forming and anvil tools) sidewall secondary buckling / wrinkling is reduced or eliminated only for puckering to occur in a basal region, or vice versa. However, advantageously, the “Improved-Folding-Shearing” process is able to more reliably eliminate simultaneously both sidewall secondary buckling / wrinkling and basal region puckering.

[0146] In the above examples of Figures 1 A - 1 F, 2A - 2F, 3A - 3F, 4A - 4B, 5A - 5B, 6A - 6B, 7A - 7B and 8A - 8D, the sidewall portions extend on only one side of the sheet metal workpiece to a peripheral edge. However, in other examples, sidewall portions can extend on other sides of the workpiece to other edges. In particular, a workpiece may have sidewall portions extending on opposite sides such that the resulting formed sheet metal structure has a ‘U’-shaped cross section with two opposing sidewalls extending from a non-planar base. In such examples, the auxiliary forming tool and the auxiliary anvil tool may have one or more workpiece tensioning regions on each of the opposing sides of the main anvil tool.

[0147] In the examples of Figures 1 A - 1 F, 2A - 2F, 3A - 3F, 4A - 4B, 5A - 5B, 6A - 6B, 7A - 7B and 8A - 8D, the corresponding secondary tool surfaces of the auxiliary anvil and forming tools are planar and substantially parallel to each so that a gap of uniform thickness is formed therebetween. Such an arrangement is convenient and relatively straightforward to implement in tooling, and is illustrated in the cross-section through a main anvil tool 310 and ‘U’-shaped workpiece 301 of Figure 9A, the workpiece having a basal region 350, opposing sidewall portions 351 , opposing edges 307 and opposing sidewall bends 357. To avoid sharply bending the workpiece as it is drawn through the gap, the normal to the planes of the secondary tool surfaces 327, 328 is disposed at an angle, a, which may be 80° or less 8659351

[0148] 25

[0149] (preferably 70° or less and more preferably 60° or less) and / or 10° or more (preferably 20° or more and more preferably 30° or more) from the axis of movement of the auxiliary forming tool.

[0150] However, to further reduce sharp bending of the workpiece, it is possible for the corresponding secondary tool surfaces to be smoothly curved and spaced from each other by a gap of substantially uniform thickness. Figure 9B shows a transverse cross-section corresponding to Figure 9A in which the planar secondary tool surfaces 327, 328 of Figure 9A are exchanged for such smoothly curved surfaces 327’, 328’. The smooth curving requires more elaborate tooling, but by avoiding sharp bending can beneficially reduce stress concentrations in the workpiece. It can also allow the workpiece to turn through greater total angles as it drawn through from one side of the gap to the other than would otherwise be possible, e.g. through 70° or more (preferably 80° or more), and even approaching 90°.

[0151] Whether the secondary tool surfaces are planar or curved, it is generally helpful for the spacing between the secondary tool surfaces and the main anvil tool to be as small as possible.

[0152] ***

[0153] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0154] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0155] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0156] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0157] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0158] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it 8659351

[0159] 26 will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

865935127Claims:1 . A method of manufacturing a formed sheet metal structure, comprising the steps of: providing a sheet metal workpiece having first and second surfaces opposed to each other and at least one edge; providing a main anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; constraining at least a part of a first basal region and an adjacent second basal region of the workpiece between the main anvil tool and a main forming tool such that the basal regions are fixed relative the main anvil tool, wherein a first sidewall portion extends between the first basal region and the edge, and a second sidewall portion extends between the second basal region and the edge; providing an auxiliary forming tool with a tool surface for contact with and constraint of at least a part of the second surface of the sheet metal workpiece; providing an auxiliary anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; directing the auxiliary forming tool along an axis of movement to contact the sheet metal workpiece such as to deform the first and second sidewall portions with respect to the first and second basal regions and thereby to form a first fold region in the sheet metal workpiece between the first sidewall portion and the second sidewall portion, until the first surface of the sheet metal workpiece contacts the auxiliary anvil tool; and concurrently progressively sliding first fold contact regions of the auxiliary forming tool and the auxiliary anvil tool along the first fold region of the workpiece to carry out shear material transfer in the first fold region to form a deformed first fold region, wherein the auxiliary forming tool has a first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary forming tool; wherein the auxiliary anvil tool has a corresponding first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary anvil tool; and wherein the first sidewall portion of the workpiece is slidingly gripped by the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool during the shear material transfer in the first fold region.

2. The method according to claim 1 wherein: the auxiliary forming tool has a second workpiece tensioning region extending from an opposite side of the first fold contact region of the auxiliary forming tool; the auxiliary anvil tool has a corresponding second workpiece tensioning region extending from an opposite side of the first fold contact region of the auxiliary anvil tool; and the second sidewall portion of the workpiece is slidingly gripped by the second workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool during the shear material transfer in the first fold region.

3. The method according to claim 1 or 2 wherein:865935128 in the constraining step at least a part of a third basal region of the workpiece adjacent to the first basal region is constrained between the main anvil tool and a main forming tool such that the third basal region is fixed relative the main anvil tool, wherein a third sidewall portion extends between the third basal region and the edge; in the directing step, the third sidewall portion is also deformed with respect to the third basal region thereby to form a second fold region between the first sidewall portion and the third sidewall portion; in the sliding step, second fold contact regions of the auxiliary forming tool and the auxiliary anvil tool are also concurrently progressively slid along the second fold region of the workpiece to carry out shear material transfer in the second fold region to form a deformed second fold region; the first workpiece tensioning region of the auxiliary forming tool extends between the first and second fold contact regions of the auxiliary forming tool; and the first workpiece tensioning region of the auxiliary anvil tool extends between the first and second fold contact regions of the auxiliary anvil tool.

4. The method according to any one of the previous claims wherein the final shape of the first or second sidewall portion may include a planar major region which, on a cross-section perpendicular to the planar major region and containing the axis of movement of the auxiliary forming tool, deviates from the axis of movement by 1 ° or more.

5. The method according to any one of the previous claims wherein the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool are planar and substantially parallel to each other.

6. The method according to claim 5 wherein the normal to the planes of the workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool are disposed at an angle of 80° or less from the axis of movement of the auxiliary forming tool.

7. The method according to claim 5 or 6 wherein the normal to the planes of the workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool is disposed at an angle of 10° or more from the axis of movement of the auxiliary forming tool.

8. The method according to any one of claims 1 to 4 wherein the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool are smoothly curved surfaces which are spaced from each other by a gap of substantially uniform thickness.

9. The method according to claim 8 wherein the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool are curved such that the workpiece turns through an angle of 70° or more as, on being slidingly gripped by the first workpiece tensioning regions, it is drawn through a gap therebetween.86593512910. The method according to any one of claims 1 to 9 further comprising a step of bending the workpiece to form a respective basal bend between adjacent basal regions, the constraining step being performed on the bent workpiece.

11. The method according to any one of claims 1 to 10, wherein during the deformation of the first and second sidewall portions with respect to the first and second basal regions a first sidewall bend is formed between the first sidewall portion and the first basal region, and a second sidewall bend is formed between the second sidewall portion and the second basal region, the first sidewall bend being offset from the second sidewall bend.

12. A sheet metal working apparatus for manufacturing a formed sheet metal structure from a sheet metal workpiece, the sheet metal workpiece having first and second surfaces opposed to each other and at least one edge, the sheet metal working apparatus comprising: a main anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; a main forming tool, which, with the main anvil tool, is configured to constrain a first basal region and an adjacent second basal region of the workpiece between the main anvil tool and a main forming tool such that the basal regions are fixed relative the main anvil tool, wherein a first sidewall portion extends between the first basal region and the edge, and a second sidewall portion extends between the second basal region and the edge; an auxiliary forming tool with a tool surface for contact with and constraint of at least a part of the second surface of the sheet metal workpiece; an auxiliary anvil tool with a tool surface for contact with and constraint of at least a part of the first surface of the sheet metal workpiece; wherein the auxiliary forming tool is configured to be directed along an axis of movement to contact the sheet metal workpiece such as to deform the first and second sidewall portions with respect to the first and second basal regions and thereby to form a first fold region in the sheet metal workpiece between the first sidewall portion and the second sidewall portion, until the first surface of the sheet metal workpiece contacts the auxiliary anvil tool; wherein first fold contact regions of the auxiliary forming tool and the auxiliary anvil tool are configured to be concurrently progressively slid along the first fold region of the workpiece to carry out shear material transfer in the first fold region to form a deformed first fold region; wherein the auxiliary forming tool has a first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary forming tool; wherein the auxiliary anvil tool has a corresponding first workpiece tensioning region extending away from a side of the first fold contact region of the auxiliary anvil tool; and wherein the first workpiece tensioning regions of the auxiliary forming tool and the auxiliary anvil tool are configured to slidingly grip the first sidewall portion of the workpiece during the shear material transfer in the first fold region.

Images