Field of the Invention

The present invention relates to method for working of sheet metal and to sheet metal structures that are obtainable by such methods of working of sheet metal. The present invention also relates to sheet metal working apparatus.

Background

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).

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.

WO 2020/043832 A1 discloses a folding-shearing process through which metal shells having curved sidewalls upstanding from a basal region in which 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.

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.

However, the present inventors have realised that is it also desired to form metal shells having a non- planar base. The difficulty in forming such metal shells is that, even where there is not curved sidewall, and therefore a shrink or stretch flange is not present in the sense of WO 2020/043832, 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.

The present invention has been devised in light of the above considerations. Summary of the Invention

In a first aspect there is provided a method of manufacturing a formed sheet metal structure. The method comprises 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; bending the workpiece to form at least a first basal region and a second basal region with a bend between them and constraining at least a part of the basal regions between the main anvil tool and a main forming tool such that the basal regions are fixed relative the main anvil tool, there being a first sidewall portion extending between the first basal region and the edge and a second sidewall portion between the second basal region and the edge; providing a first 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; contacting the sheet metal workpiece with the first auxiliary forming tool to deform the first and second sidewall portions with respect to the first and second basal regions thereby to form a first fold region in the sheet metal workpiece between the first sidewall portion and the second sidewall portion; and progressively sliding the first auxiliary forming tool along the first fold region to cause shear material transfer in the first fold region to further deform the first fold region.

A method of manufacturing the formed sheet metal structure according to the first aspect allows the formation of a side wall extending from a non-planar base within a sheet metal structure with reduced risk of buckling, wrinkling or tearing the material in the fold region of the sidewall. A fold region may form adjacent a bend formed such that the first surface of the workpiece is concave at the first bend. The steps of the method according to the first aspect may be performed in the order they are listed above.

The method may further comprise the step of providing a first 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 at the first fold region. Providing the first auxiliary anvil tool allows for greater control over the shear material transfer of material out of the fold region during the step of progressively sliding the first auxiliary forming tool along the first fold region. Constraining the first surface of the workpiece in the first fold region with the first auxiliary anvil tool also reduces the likelihood of buckling/wrinkling in the fold region.

The step of contacting the sheet metal workpiece with the main anvil tool and the first auxiliary forming tool may be executed such that a clamping pressure greater than or equal to 100 kPa is exerted on the portion of the sheet metal workpiece between the respective tool surfaces of the first auxiliary forming tool and the first auxiliary anvil tool. Exerting sufficient pressure on the portion of the workpiece clamped between the first auxiliary forming tool and first auxiliary anvil tool is beneficial in enhancing the shear material transfer in the step of sliding the first auxiliary forming tool along the first fold region. The clamping pressure may be adapted suitably according to the material and thickness of the workpiece.

The method may further comprise the step of progressively sliding the first auxiliary anvil tool along the first fold region. In such a case, the step of progressively sliding the first auxiliary anvil tool along the first fold region may be executed concurrently with the step of sliding the first auxiliary forming tool along the first fold region to control the deformation of the first fold region. Advantageously, sliding the first auxiliary anvil tool along the first fold region concurrently with the first auxiliary forming tool enhances the shear material transfer of material out of the fold region and reduces the likelihood of buckling/wrinkling in the fold region. In effect, the first auxiliary anvil tool provides a moving constraint along with the first auxiliary forming tool, constraining the material of the workpiece in the fold region to reduce buckling/wrinkling. As will be understood, it is intended that the first auxiliary forming tool slides along the second surface of the workpiece and that the first auxiliary anvil tool slides along the first surface of the workpiece.

The progressive sliding of the first auxiliary anvil tool along the first fold region may be effected by the progressive sliding of the first auxiliary forming tool along the first fold region. This provides a simple manner in which to ensure that the first auxiliary forming tool and first auxiliary anvil tool move in concert, for example with the same velocity (same speed and direction), enhancing the shear material transfer of material out of the fold region and reducing the likelihood of buckling/wrinkling in the fold region.

The main anvil tool and first auxiliary anvil tool may each be connected to a first press plate. In such a case, at least one of the main anvil tool and first auxiliary anvil tool may be movably connected to the first press plate. Advantageously, this configuration allows the main and first auxiliary anvil tools to be moved together as if a single tool, or to be moved independently of one another.

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 surface of the first sidewall portion of the workpiece and at least a part of the first surface of the second sidewall portion of the workpiece during the step of contacting the sheet metal workpiece with the first auxiliary forming tool. Moreover, 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 first auxiliary forming tool along the first fold region. Thus, the main anvil tool sidewall can act to constrain the deformation of the workpiece and reduce the likelihood of tearing and/or buckling the workpiece during the deformation of the workpiece. The main anvil tool sidewall may be substantially planar.

The step of bending the workpiece to form the first basal region and second basal region may be executed by the step of clamping the sheet metal workpiece between respective tool surfaces of the main anvil tool and main forming tool. Executing the bending step in this manner is beneficial in that the bend 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 step of clamping the sheet metal workpiece between the main anvil tool and main forming tool may be executed such that a clamping pressure greater than or equal to 100 kPa is exerted on the portion of the sheet metal workpiece between the respective tool surfaces the main anvil tool and the main forming tool. Advantageously, exerting sufficient pressure on the portion of the workpiece clamped between the main anvil tool and main forming tool enhances the plastic deformation of the workpiece during the bending step. The clamping pressure may be set in order to balance the elastic recovery of the workpiece against the thinning of the workpiece caused by the clamping and subsequent deformation.

The sheet metal workpiece may remain clamped between the main anvil tool and main forming tool during the steps of: contacting the sheet metal workpiece with the main anvil tool and first auxiliary forming tool to deform the first and second sidewall portions; and progressively sliding the first auxiliary forming tool along the first fold region. Advantageously, clamping the workpiece between the main anvil tool and main forming tool prevents movement of the basal regions during later deformation steps.

The main forming tool and first auxiliary forming tool may each be connected to a second press plate, at least one of the main forming tool and first auxiliary forming tool may be movably connected to the second press plate. Advantageously, this configuration allows the main and first auxiliary forming tools to be moved together as if a single tool, or to be moved independently of one another.

The method may further comprise the step of bending the workpiece to form a third basal region with a second bend between the second basal region and the third basal region, there then being a third sidewall portion extending between the third basal region and the edge. The step of contacting the sheet metal workpiece with the first auxiliary forming tool may then also deform the third sidewall portion with respect to the third basal region thereby to form a second fold region in the sheet metal workpiece between the second sidewall portion and the third sidewall portion. The method may then further comprise the step of progressively sliding the first auxiliary forming tool along the second fold region to further deform the second fold region.

The first sidewall portion and second sidewall portion may be provided on a first side of the basal regions. A fourth sidewall portion may then extend between the first basal region and an edge of the sheet metal workpiece on another side of the basal regions and a fifth sidewall portion may extend between the second basal region and said edge. In such a case, the method may then further comprise the steps of: providing a second 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; contacting the sheet metal workpiece with the second auxiliary forming tool to deform the fourth and fifth sidewall portions with respect to the first and second basal regions thereby to form a third fold region in the sheet metal workpiece between the fourth sidewall portion and the fifth sidewall portion; and progressively sliding the second auxiliary forming tool along the third fold region to cause shear material transfer in the third fold region to further deform the third fold region. Advantageously, this allows corner-shaped sheet metal structures or channel-shaped sheet metal structures to be formed using the present method.

The second auxiliary forming tool may be formed integrally with the first auxiliary forming tool. Accordingly, there are fewer forming tools requiring independent control during execution of the method and the deformation caused by the tooling can be more precise by the distance between the forming tools being more tightly constrained by them being formed integrally with one another.

In a second aspect there is provided a workpiece obtained or obtainable using a method according to the first aspect.

In a third aspect there is provided sheet metal working apparatus suitable for performing a method for manufacturing a formed sheet metal structure according to the first aspect.

In a fourth aspect there is provided sheet metal working apparatus for manufacturing a formed sheet metal structure from a sheet metal workpiece. The sheet metal workpiece has first and second surfaces opposed to each other and at least one edge. The formed sheet metal structure to be manufactured has at least a first basal region and a second basal region with a bend between them, a first sidewall portion extending between the first basal region and the edge, and a second sidewall portion between the second basal region and the edge. The sheet metal working apparatus comprises: 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 at least a part of the basal regions; a first 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. The first auxiliary forming tool is configured to be contacted with the sheet metal workpiece such as to deform the first and second sidewall portions with respect to the first and second basal regions thereby to form a first fold region in the sheet metal workpiece between the first sidewall portion and the second sidewall portion. The first auxiliary forming tool is further configured to be slid along the first fold region to cause shear material transfer in the first fold region to further deform the first fold region.

The above method (otherwise termed herein a “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).

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. 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.

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.

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 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. 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 the reduce the occurrence of wrinkling and/or tearing during the forming process.

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.

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.

The term “curved” is considered to be synonymous to “rounded” and is used to generally refer to a region having some degree of curvature. The curvature may vary across the region. Accordingly, the terms curved or rounded are not used herein to solely refer to regions of constant curvature (i.e. they are not intended to be limited only to cylindrical or spherical regions).

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.

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

In a fifth preferred aspect, the present invention provides a kit comprising the sheet metal working apparatus of the third or fourth aspect and one or more further anvil tools and one or more further forming tools.

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

Examples illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

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;

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;

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;

Figures 4A - 4E 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.

Detailed Description of the Invention

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.

The process described herein can be understood as “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.

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 “Folding-Shearing”.

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 “Folding-Shearing” process.

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.

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).

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 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.

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 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 bend 56. In the case of the workpiece 1 in Figures 1A - 1 F, the 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 Figures 1 C - 1 F is where buckling/wrinkling is prone to occurring absent the present method.

Figure 1 D illustrates a stage of the process where the majority 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 the 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 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 is required to eliminate the raised part of the fold region 55 and bring the fold region 55 into conformity with the deformed sidewall portions 51 , 61 ; however, such further deformation liable to cause buckling/wrinkling of the sheet metal workpiece 1 in the fold region 55 due to the reduction in surface area required there.

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 buckling/wrinkling the workpiece 1 in this region. 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 wrinkling/buckling by shear material transfer in the fold region, with material transfer from the fold region to at least one sidewall portion. A lower portion of the fold region 55 is still raised in Figure 1 E and requires further shear material transfer in order for the fold region 55 to conform with the developed sidewall portions 51 , 61.

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. 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 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).

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 “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 the main anvil tool and the first auxiliary anvil tool are shown, in addition to the workpiece.

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.

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 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 a first auxiliary anvil tool 20, which also has a 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 manufacturing process may utilise the first auxiliary anvil tool 20 to exert greater control over the forming of the sheet metal workpiece 1 , as is described below in relation to Figures 2D - 2F; however, the present process can also be conducted without the first auxiliary anvil tool 20.

Where main and first auxiliary anvil tools 10, 20 are present, the main and first 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 first auxiliary anvil tool 20 is movable relative the main anvil tool 10; thus, where the main and first 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.

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 first auxiliary anvil tool 20 is provided adjacent the sidewall 16 of the main anvil tool 10 and takes the approximate form of an oblique triangular pyramid, optionally being truncated, with an apex laterally aligned with the bend 56.

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 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 a first auxiliary forming tool (not shown).

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 tool surface 25 of the first auxiliary anvil tool 20 at the fold region 55. The fold region 55 is supported by the first auxiliary anvil tool 20 such that it does not undergo deformation that would resulting in buckling/wrinkling of the sheet metal workpiece 1 in the fold region 55 whilst deforming the sidewall portions 51 , 61. Typically, the first auxiliary anvil tool 20 prevents buckling in the fold region 55 by providing a tooling 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%).

Figure 2E then illustrates the workpiece 1 part way through a later step of the manufacturing process, in which the first 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 into conformity with the developed regions of the sidewall portions 51 , 61 . 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 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 tool surface 25 of the first 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 first auxiliary anvil tool 20 must be withdrawn from underneath the fold region 55 such that it no longer constrains the whole of it.

In order to allow controlled deformation of the fold region 55, the first auxiliary anvil tool 20 is withdrawn from underneath the fold region 55 concurrently with the first 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 first auxiliary anvil tool 20 can be deformed by the first auxiliary forming tool. The portion of the fold region 55 where it is not constrained by the first 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 buckling/wrinkling. In Figure 2E the first auxiliary anvil tool 20 is lower with respect to the main anvil tool 10 and the workpiece 1 than it is in Figure 2D. This 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 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).

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 “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.

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

In Figure 3A, the first auxiliary forming tool 30 has been provided for use in forming the sheet metal structure. The first 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.

Where main and first auxiliary forming tools 30, 40 are present, the main and first auxiliary forming tools 30, 40 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 first auxiliary forming tool 30; thus, where the main and first 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.

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 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.

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 first auxiliary anvil tool 20 positioned underneath the sidewall portions 51 , 61.

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 first 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 first 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 first 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.

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 first 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 first auxiliary forming tool 30 in Figures 3A - 3F also comprises an inverted ‘v’-shaped section that, as Figure 3E illustrates, aligns with the shape of the tool surface 25 of the first auxiliary anvil tool 20. As the sidewall portions 51 , 61 are deformed by the relative movement of the first 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 first auxiliary forming tool 30 and the tool surface 25 of the first auxiliary anvil tool 20. The first auxiliary forming tool 30 continues to move downwards until the fold region 55 is interposed between and fully contacting the first auxiliary forming tool 30 and the first auxiliary anvil tool 20. The downward movement of the forming tool 30 relative the workpiece 1 and the first auxiliary anvil tool 20 clamps the fold region 55 between the respective tool surfaces 35, 25 of the first auxiliary forming tool 30 and the first auxiliary anvil tool 20. The first 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. 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 fold region 55 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.

Figure 3F then illustrates the process of sliding the first auxiliary forming tool 30 along the fold region 55 to cause shear material transfer therein to further deform the fold region 55 and bring the fold region 55 into conformity with the developed regions of the sidewall portions 51 , 61 , as discussed in relation to Figures 1 E, 1 F, 2E and 2F. Between figures 3E and 3F, it is clear that both the first auxiliary forming tool 30 and the first 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. The first auxiliary forming tool 30 and first auxiliary anvil tool 20 continue to move downwards together, reducing the 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 . The movement of the first auxiliary forming tool 30 and the first 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 first auxiliary anvil tool 20 may be caused by the first auxiliary forming tool 30 transmitting a sufficiently large pressure onto the first auxiliary anvil tool 20 (through the workpiece 1 clamped therebetween, or through contact between the tools that lies outside the workpiece perimeter) that the first auxiliary anvil tool 20 is urged to move downward with the forming tool 30.

Figures 4A - 4E, progressing from Figure 4A to Figure 4E in order, illustrate various stages of the abovedescribed manufacturing process being conducted to form a formed sheet metal structure that has plural bends in the base, and accordingly plural fold regions are formed during the manufacturing process.

As with the example discussed in relation to Figures 1 A - 1 F, 2A - 2F and 3A - 3F, the workpiece 100 comprises first and second surfaces 103, 105 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 107. The shape of the sheet metal workpiece 101 and the one or more peripheral edges 107 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. At the stage of the process shown in Figure 4A, the workpiece 101 is flat and the main anvil tool 110 for contacting with and constraining at least a part of the workpiece 101 is provided, having a tool surface 115. The main anvil tool 110 further comprises a sidewall 116 extending from the tool surface 115 and in Figure 4A the edge at which the sidewall 116 and tool surface 115 meet is bevelled to aid the smooth deformation of the sidewall portions 151 , 161 at a later step of the process.

At the stage illustrated in Figure 4B, the workpiece 101 has been bent to form the basal regions of the workpiece. In particular, the workpiece 101 in Figure 4B comprises a first basal region 150, a second basal region 160, a third basal region 170 and a fourth basal region 180, with bends 156, 166, 176 present between adjacent basal regions. In the example of Figures 1A - 1 F, 2A - 2F and 3A - 3F, bend 156 is such that the first surface 3 of the workpiece 1 is at the bend 156. However, in Figure 4B, a combination of concave and convex portions of the first surface 103 are present. Specifically:

The first bend 156 is such that the first surface 103 of the workpiece is 101 is convex there;

The second bend 166 is such that the first surface 103 of the workpiece is 101 is concave there; and

The third bend 176 is such that the first surface 103 of the workpiece is 101 is concave there.

The workpiece 101 in Figure 4B also differs from that in Figures 1 B, 2B and 3B in that in Figure 4B sidewall portions extend from the basal regions on another side of the basal regions as well as on the side proximate the edge 107 of the workpiece 101 . More specifically, in Figure 4B, there is the first sidewall portion 151 , second sidewall portion 161 , third sidewall portion 171 , and fourth sidewall portion 181 that all extend from the same side of the basal regions 150, 160, 170, 180 from their respective basal regions 150, 160, 170, 180 towards the edge 107, and there are also corresponding sidewall portions extending from those basal regions 150, 160, 170, 180 on the opposite side of the basal regions 150, 160, 170, 180 to the first to fourth sidewall portions 151 , 161 , 171 , 181 . Accordingly, when the manufacturing process is complete, the resulting formed sheet metal structure has a ‘U’-shaped cross section with two sidewalls extending from a non-planar base (see Figure 4E). It can be appreciated that the more complex arrangement of bends in the base of the workpiece 101 is not necessarily associated with the workpiece 101 having sidewall portions extending from the basal regions on opposite sides of the basal regions to form a formed sheet metal structure with a ‘U’-shaped cross section - the two features are separable.

Figure 4C illustrates a stage of the manufacturing process in which the step of contacting the sheet metal workpiece 101 with the main anvil tool 110 and the first auxiliary forming tool (not shown) to deform the sidewall portions 151 , 161 , 171 , 181 has commenced. Figure 4C illustrates how the first, second, third and fourth sidewall portions 151 , 161 , 171 , 181 are deformed such as to no longer be co-planar with their respective basal regions 150, 160, 170, 180. In the case of Figure 4C, the sidewall portions 151 , 161 , 171 , 181 are deformed in a downward direction such that the first surface 103 of the workpiece 101 is concave between the base and the sidewall (i.e. the angle between the first surface 103 in the first basal region 150 and the first surface 103 in the first sidewall portion 151 is less than 180° and the same applies for the other pairs of corresponding basal regions and sidewall portions). In the process of deforming the sidewall portions 151 , 161 , 171 , 181 , a stretch region 155 and two fold regions 165, 175 form that correspond to the bends 156, 166, 176. In the case of the workpiece 101 in Figures 4A:

The stretch region 155 is where there is insufficient material present in the workpiece and where tearing is prone to occurring absent the present method;

The first fold region 165 is where there is excess material present in the workpiece and where buckling/wrinkling is prone to occurring absent the present method; and

The second fold region 175 is where there is excess material present in the workpiece and where buckling/wrinkling is prone to occurring absent the present method.

In Figure 4C, deformation of the sidewall portions on the opposite side of the basal regions 150, 160, 170, 180 to the first to fourth sidewall portions 151 , 161 , 171 , 181 has also commenced. A second auxiliary forming tool (not shown) may be provided for contact with, and constraint of, at least a part of the second surface 105 of the sheet metal workpiece 101 and contacting the second auxiliary forming tool with the sheet metal workpiece 101 deforms these opposite sidewall portions, forming an equivalent stretch region and equivalent fold regions to the stretch region 155 and second and third fold regions 165, 175 visible in Figure 4C. In some implementations of the present invention, it may be desirable that the second auxiliary forming tool is movable relative the main anvil tool 115 independently of the first auxiliary forming tool, for example where the length of the sidewall portions (i.e. the distance between the basal region and the workpiece edge) to be deformed by the first auxiliary forming tool is different to the length of the sidewall portions to be deformed by the second auxiliary forming tool. However, in other implementations, the first auxiliary and second auxiliary forming tools may be formed integrally with each other, such that there are fewer forming tools requiring independent control.

It can be appreciated that, where the bend 166, 176 is such that the first surface 103 is concave between adjacent basal regions, a fold region 165, 175 forms adjacent these bends 166, 176 that is similar to the fold region 55 discussed above and illustrated in Figures 1C - 1 F, 2C - 2F and 3D - 3F: there is excess material present in the workpiece at these fold regions and buckling/wrinkling is prone to occurring absent the present method when deforming the raised fold regions 165, 175. The second and third fold regions 165, 175 can be further deformed in the same manner discussed above in relation to Figures 1 E, 2E and 3F: the first auxiliary forming tool can be progressively slid along the second and third fold regions 165, 175 to cause shear material transfer therein, with material being transferred from each fold region into one or both of the sidewall portions adjacent that fold region, and potentially into one or both basal regions adjacent that fold region. One or more additional anvil tool(s) similar to the first auxiliary anvil tool 20 discussed in relation to Figures 2A - 2F and 3A - 3F can be used to support the second and third fold regions 165, 175 and assist the first auxiliary forming tool in further deforming the second and third fold regions 165, 175 without buckling/wrinkling he workpiece 101 in this area. Figure 4D illustrates a stage of the process where the step of further deforming the second and third fold regions 165, 175 is partly completed, with upper portions of the raised fold regions 165, 175 present in Figure 4C having been flattened in Figure 4D to lie in conformity with the developed sidewall portions 161 , 171 , 181 ; lower parts of the fold regions 165, 175 are still raised in Figure 4D and require further shear material transfer in order to bring the fold regions 165, 175 into conformity with the adjacent developed sidewall portions 161 , 171 , 181 . Although not visible in Figure 4D, an equivalent step of the manufacturing process can be conducted for the equivalent fold regions to the second and third fold regions 165, 175 on the opposite side of the base to the second and third fold regions 165, 175.

In contrast to the example discussed in Figures 1 A - 1 F, 2A - 2F and 3A - 3F, the example in Figures 4A - 4E also includes a stretch region 155 formed adjacent the first bend 156 where the first surface 103 of the sheet metal workpiece 101 is convex, rather than concave. Accordingly, material in the stretch region 155 is liable to tearing during the step of contacting the sheet metal workpiece 101 with the main anvil tool 110 and first auxiliary forming tool to deform the sidewall portions 151 , 161 , 171 , 181 with respect to the basal regions 150, 160, 170. The region 155 is termed a ‘stretch region’ because in the prior art the material in this region requires substantial stretching and thinning in order to be deformed to conform with the sidewall portions. This is because of the increase in the surface area of the sheet metal workpiece 101 required in the vicinity of the stretch region 155 to transition between the un-deformed sidewall state illustrated in Figure 4B to the deformed sidewall state shown in Figure 4C.

However, in the present embodiment, during the step of the manufacturing process in which the first auxiliary forming tool is contacted with the sheet metal workpiece 101 the part can deform stably by inplane shear material transfer within the limits of the deformation the material will withstand before substantial thinning and tearing occurs. The anvil and forming tools may be designed with suitable tool radii in accordance with conventional flanging tool design methods in order to enhance stable deformation in the stretch region 155. Although not visible in Figure 4C, an equivalent step of the manufacturing process can be conducted for the equivalent stretch region to the stretch region 155 on the opposite side of the basal regions 150, 160 to the stretch region 155. The formed sheet metal structure 101 at the end of the manufacturing process is shown in Figure 4E, comprising two continuous sidewalls extending downward from the base, the sidewalls being on opposite sides of the base, with the base being non-planar (e.g. in Figure 4E having four basal regions that are not co-planar with each other) but the sidewalls extending from that base being substantially planar (at least in the case of the example illustrated in Figure 4E). Here both sidewalls lie in planes 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 4E 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).

***

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.

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.

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.

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

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.

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 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%. References

One or more publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below.

The entirety of each of these references is incorporated herein.

Horton, P.M. and Allwood, J.M. (2017): “Yield improvement opportunities for manufacturing automotive sheet metal components”, Journal of Materials Processing Technology, 249 78-88.

Reference Numbers

1 , 101 sheet metal workpiece

3, 103 first surface

5, 105 second surface

7, 107 peripheral edge

10, 110 main anvil tool

15, 115 tool surface of main anvil tool

16 sidewall of main anvil tool

20 first auxiliary anvil tool

25 tool surface of first auxiliary anvil tool

30 first auxiliary forming tool

35 tool surface of first auxiliary forming tool

40 main forming tool

45 tool surface of main forming tool

50, 150 first basal region

51 , 151 first sidewall portion

55,165 first fold region

56, 156 first bend

60, 160 second basal region

61 , 161 second sidewall portion

155 stretch region

166 second bend

170 third basal region 171 third sidewall portion

175 second fold region

176 third bend

180 fourth basal region 181 fourth sidewall portion