Roller Offset Forming Tool and Method of Mitigating Distortion in a Metal Sheet

The disclosure relates to a roller offset forming tool and a method of mitigating distortion in a workpiece formed from a metal sheet.

Roller offset forming is a sheet metal fabrication technique useful for forming complex three-dimensional (3D) metal panels and shapes. Roller offset forming processes may bend and form a flat metal sheet into a desired 3D shape using a set of rollers that move along a predefined path. The set of rollers may apply bending forces to the metal sheet to create plastic deformation as the rollers follow a manually or computer-controlled path. Although distortion may be induced in the metal sheet in areas apart from the path of the rollers, roller offset forming may be well-suited for prototyping and medium production volumes and may be capable of producing complex shapes with excellent dimensional accuracy and high geometrical flexibility.

A roller offset forming tool includes a first roller configured to rotate in a first direction about a first longitudinal axis against a metal sheet. The first roller includes a first bead having a first shape. The roller offset forming tool also includes a second roller disposed opposite and configured to engage with the first roller. The second roller is configured to rotate in a second direction that is opposite to the first direction about a second longitudinal axis against the metal sheet to thereby deform the metal sheet and form an offset feature therein. The second roller includes a secondary bead having a second geometry. The first bead is configured to align and mate with the secondary bead along a first vertical axis that is substantially perpendicular to the first longitudinal axis and the second longitudinal axis to thereby hold the metal sheet between the first roller and the second roller. The first shape and the second geometry are configured to mitigate a distortion of the metal sheet in an area apart from the offset feature and stiffen the metal sheet at the offset feature.

In one aspect, the first bead may define a first channel therein and the secondary bead is configured to protrude into the first channel along the first vertical axis.

In another aspect, each of the first bead and the secondary bead may be symmetrical across the first vertical axis.

In an additional aspect, the first bead may be symmetrical across the first vertical axis and the secondary bead may be asymmetrical across the first vertical axis.

In a further aspect, the first roller may further include a primary bead spaced apart from the first bead along the first longitudinal axis and having a first geometry. The second roller may further include a second bead spaced apart from the secondary bead along the second longitudinal axis and having a second shape. The first geometry and the second geometry may be configured to mitigate a distortion of the metal sheet in an area apart from the offset feature and stiffen the metal sheet at the offset feature.

In one aspect, the second bead may be configured to align and mate with the primary bead along a second vertical axis spaced apart from the first vertical axis along the second longitudinal axis to thereby hold the metal sheet between the first roller and the second roller.

In another aspect, the second bead may define a second channel therein, and the primary bead may be configured to protrude into the second channel.

In a further aspect, the first bead may have a first radius, the primary bead may have a primary radius that is less than the first radius, the second bead may have a second radius, and the secondary bead may have a secondary radius that is less than the second radius.

In one aspect, the first roller may have a first distal end, and the second roller may have a second distal end aligned with the first distal end along a vertical axis that is substantially perpendicular to the first longitudinal axis and the second longitudinal axis. Further, the primary bead may be disposed at a first distance from the first distal end, the secondary bead may be disposed at a second distance from the second distal end, and the second distance may be from 20% of the first distance from the first distal end to 80% of the first distance from the first distal end.

In another aspect, the first bead and the secondary bead may mate along a first vertical axis that is substantially perpendicular to the first longitudinal axis and the second longitudinal axis. Further, the primary bead and the second bead may mate along a second vertical axis spaced apart from the first vertical axis along the second longitudinal axis.

In one aspect, a motor vehicle may include an article formed by the roller offset forming tool.

In another aspect, a roller offset forming system may include a metal sheet sandwiched between and disposed in contact with the first bead and the secondary bead of the roller offset forming tool.

In an additional aspect, the metal sheet may be substantially free from distortion in the area spaced apart from the offset feature.

In one embodiment, a roller offset forming tool includes a first roller configured to rotate in a first direction against a metal sheet. The first roller includes a first bead and a primary bead spaced apart from the first bead and having a first geometry. The roller offset forming tool also includes a second roller disposed opposite and configured to engage with the first roller. The second roller is configured to rotate in a second direction that is opposite to the first direction against the metal sheet to thereby deform the metal sheet and form an offset feature therein. The second roller includes a second bead and a secondary bead spaced apart from the second bead and having a second geometry. The first geometry, the first shape, the second shape, and the second geometry are configured to mitigate a distortion of the metal sheet in an area apart from the offset feature and stiffen the metal sheet at the offset feature. Each of the first shape and the second geometry includes a bottom fillet, a top fillet spaced apart from the bottom fillet, a top, a bottom spaced apart from the top, a side wall connecting the top and the bottom, and an angle of inclination defined between the bottom and the side wall. Further, each of the first shape and the second geometry is defined by at least one of: a first variable set including a bottom fillet radius, a top fillet radius, a bottom half width, a top half width, and a bead height; and a second variable set including the bottom fillet radius, the top fillet radius, the angle of inclination, a side wall length, and the top half width.

In another aspect, the first shape may be dependent upon the second geometry.

In an additional aspect, the first shape may be independent of the second geometry.

In a further aspect, the angle of inclination may be greater than 0° and less than or equal to 90°.

A method of mitigating a distortion of a workpiece includes forming the workpiece having an offset feature and a plurality of areas each spaced apart from the offset feature from a metal sheet with a roller offset forming tool. The roller offset forming tool includes a first roller configured to rotate in a first direction about a first longitudinal axis against a metal sheet. The first roller includes a first bead having a first shape. The roller offset forming tool also includes a second roller disposed opposite and configured to engage with the first roller. The second roller is configured to rotate in a second direction that is opposite to the first direction about a second longitudinal axis against the metal sheet to thereby deform the metal sheet and form an offset feature therein. The second roller includes a secondary bead having a second geometry. The first bead is configured to align and mate with the secondary bead along a first vertical axis that is substantially perpendicular to the first longitudinal axis and the second longitudinal axis to thereby hold the metal sheet between the first roller and the second roller. The first shape and the second geometry are configured to mitigate a distortion of the metal sheet in an area apart from the offset feature and stiffen the metal sheet at the offset feature. The method also includes measuring a height (h) of the offset feature and an actual height (h) of each of the plurality of areas, and assigning a distortion degree value (DDV) to the workpiece. Further, the method includes determining whether the distortion degree value (DDV) is less than or equal to a threshold distortion degree value (DDV). If the distortion degree value (DDV) is greater than the threshold distortion degree value (DDV), the method includes changing at least one of the first shape and the second geometry and forming a subsequent workpiece. If the distortion degree value (DDV) is less than or equal to the threshold distortion degree value (DDV), the method includes forming the subsequent workpiece without changing at least one of the first shape and the second geometry to thereby mitigate the distortion of the workpiece.

In one aspect, assigning may include calculating the distortion degree value according (DDV) to formula (I):

DDV=root mean square()  (I)

In another aspect, forming may include sandwiching the metal sheet between the first bead and the secondary bead.

In an additional aspect, forming may include turning the first roller in the first direction against the metal sheet and turning the second roller in the second direction against the metal sheet such that the primary bead deforms the metal sheet at the secondary bead and thereby forms the offset feature.

The above features and advantages, and other features and attendant advantages of this disclosure, will be readily apparent from the following detailed description of illustrative examples and modes for carrying out the present disclosure when taken in connection with the accompanying drawings and the appended claims. Moreover, this disclosure expressly includes combinations and sub-combinations of the elements and features presented above and below.

Referring to the Figures, wherein like reference numerals refer to like elements, a roller offset forming tool() and method() of mitigating distortion() in a workpiece() formed from a metal sheet() are shown generally. The roller offset forming tooland methodmay be useful for applications requiring three-dimensional articles() formed from the metal sheetand including an offset feature(). In particular, the roller offset forming tooland methodmay be useful for inducing one or more offset featuresor bends in the metal sheetwithout creating undesirable distortionin an area() spaced apart from the offset feature.

More specifically, the roller offset forming tooland methodform the offset featureusing a customized set of rollers,() that include a first bead() and a secondary bead() configured for inducing deformation to the metal sheet, increasing a stiffness of the metal sheetat the offset feature, and controlling distortionat areasapart from the offset feature. The set of rollers,may be customized with the first beadand secondary beadto avoid additional tool investment and ensure excellent dimensional accuracy of the offset featureand stiffness of the formed workpiece. As such, the roller offset forming tooland methodmay enable production of articleshaving complex shapes and excellent dimensional accuracy without excess distortion.

Therefore, the roller offset forming tooland methodmay be useful for automotive applications such as, but not limited to, prototyping and manufacturing articlessuch as shear plates, skid plates, ducts, brackets, wire tracks, tools, assembly aids, and other vehicle components. For example, a motor vehicle() may include the article, such as a shear plate for a battery, formed by the roller offset forming tooland method. Alternatively, the roller offset forming tooland methodmay be useful for non-automotive applications such as, but not limited to, prototyping and manufacturing articlesand components for aerospace, aviation, marine, transportation, robot, architectural, industrial, medical, and consumer product applications.

Referring now to, the roller offset forming toolincludes a first rollerconfigured to rotate in a first directionabout a first longitudinal axisagainst the metal sheet(). The roller offset forming toolalso includes a second rollerdisposed opposite the first rollerand configured to engage with the first roller. The second rolleris configured to rotate in a second directionthat is opposite to the first directionabout a second longitudinal axisagainst the metal sheetto thereby deform the metal sheetand form the offset featuretherein. For example, the first rollerand the second rollermay be annular and may be configured to hold the metal sheettherebetween during roller offset forming processes. In one non-limiting example, the first rollermay be configured as a punch and the second rollermay be configured as a die.

As best shown in, the first rollerincludes the first beadhaving a first shape(). Similarly, the second rollerincludes the secondary beadhaving a secondary geometry(). The first beadis configured to align and mate with the secondary beadalong a first vertical axis() that is substantially perpendicular to the first longitudinal axisand the second longitudinal axisto thereby hold the metal sheetbetween the first rollerand the second roller.

In another embodiment described with continued reference to, the first rollermay also include a primary beadspaced apart from the first beadalong the first longitudinal axisand having a first geometry. To be clear, the first beadand the primary beadmay not necessarily have the same shape or form. That is, the first beadand the primary beadmay have different shapes. The first shape() is used herein to describe the first bead, and the first geometry() is used herein to describe the primary bead. Similarly, the second rollermay also include a second beadspaced apart from the secondary beadand having a second shape(). To be clear, the second beadand the secondary beadmay not necessarily have the same shape or form. That is, the second beadand the secondary beadmay have different shapes. The second shapeis used herein to describe the second bead, and the second geometryis used herein to describe the secondary bead.

As set forth in more detail below, the first shapeand the second geometryare configured to mitigate the distortionof the metal sheetin the area() apart from the offset feature() and stiffen the metal sheetat the offset feature. Further, for embodiments including two sets of beads, i.e., the first bead, the secondary bead, the second bead, and the primary bead, the first geometryand the second geometryand the first shapeand the second shapemay be configured to mitigate the distortionof the metal sheetin the areaapart from the offset featureand stiffen the metal sheetat the offset feature. In particular, referring to, the offset featureitself may be formed due to an inclination offset of the first rollerand the second roller, e.g., at a sloped or inclined surface() between the first beadand the primary beadthat is paired with a corresponding sloped or inclined surface() between the second beadand the secondary bead. However, the first shapeand the second geometrymay control and/or minimize the distortionin the areaapart from the offset feature. More specifically, the first shapeand the second geometrymay form satellite features that surround the offset featureand minimize distortion apart from the offset feature. That is, for embodiments including two pairs of beads-,-, based on the first geometryof the primary beadand the second geometryof the secondary bead, in combination with the respective first and second shapes,of the first and second beads,, the metal sheetmay be substantially free from distortionin the areaspaced apart from the offset feature.

As described with continued reference to, each of the first bead, the primary bead, the second bead, and the secondary beadmay be annular and may either protrude in a radial direction from or be recessed toward respective centers of the first rollerand the second roller. The primary beadmay be relatively smaller than the first beadand the secondary beadmay be relatively smaller than the second bead. That is, the first beadmay have a first radiusand the primary beadmay have a primary radiusthat is less than the first radius. Similarly, the second beadmay have a second radiusand the secondary beadmay have a secondary radiusthat is less than the second radius. The first bead, the primary bead, the second bead, and the secondary beadmay be referred to as mini beads because the beads,,,may be small as compared to an overall dimension of the respective first and second rollers,. That is, a step size or height of protrusion of the primary beadand the secondary beadand a step size or depth of recession of the first beadand second beadmay be comparatively smaller than an overall dimension of the first and second rollers,, respectively. The mini beads,,,may be shaped to induce additional deformation to the metal sheet, form the offset feature, stiffen the metal sheetat the offset feature, and mitigate the distortionof the metal sheetin the areaapart from the offset feature.

In particular, and as described with continued reference to, during roller offset forming operations, the first beadmay be configured to align with the secondary beadand the second beadmay be configured to align with the primary beadto thereby hold the metal sheetbetween the first rollerand the second roller. The first beadmay define a first channelor concavity or depression therein and the second beadmay define a second channelor concavity or depression therein. That is, the first shapemay be the first channeland the second shapemay be the second channel. The primary beadmay be configured to protrude into the second channeland the secondary beadmay be configured to protrude into the first channel. As such, the first rollerand the second rollermay mate at the first bead—secondary beadpairing and at the second bead—primary beadpairing to thereby hold the metal sheettherebetween. As the first rollerturns in the first direction() and the second rollerturns in the second direction() that is opposite to the first direction, the roller offset forming toolmay form the offset featurein the metal sheet.

In greater detail and referring again to, the first rollermay have the first longitudinal axisand the primary beadmay be spaced apart from the first rolleralong the first longitudinal axis. In addition, the second rollermay have the second longitudinal axisand the secondary beadmay be spaced apart from the second beadalong the second longitudinal axis. That is, the first rollermay have a first distal endand the second rollermay have a second distal endaligned with the first distal endalong a vertical axisthat is substantially perpendicular to the first longitudinal axisand the second longitudinal axis. The primary beadmay be disposed at a first distancefrom the first distal endand the secondary beadmay be disposed at a second distancefrom the second distal end. The second distancemay be from 20% of the first distanceto 80% of the first distance, e.g., from 25% of the first distanceto 75% of the first distance, or from 50% of the first distanceto 65% of the first distance.

Further, as described with reference to, the first beadmay have a first face widthalong the first longitudinal axisand the secondary beadmay be positioned along the second longitudinal axisso as to align with the first beadwithin the dimension of the first face width. Similarly, the second beadmay have a second face widthalong the second longitudinal axisand the primary beadmay be positioned along the first longitudinal axisso as to align with the second beadwithin the dimension of the second face width. Therefore, acceptable positioning of the primary beadand the secondary beadmay be selected and optimized within the constraints of the second face widthand first face width, respectively.

With continued reference to, the first beadand the secondary beadmay align and mate along the first vertical axisthat is substantially perpendicular to the first longitudinal axisand the second longitudinal axis. Likewise, the second beadmay be configured to align and mate with the primary beadalong a second vertical axisspaced apart from the first vertical axisalong the second longitudinal axisto thereby hold the metal sheetbetween the first rollerand the second roller. That is, the primary beadand the second beadmay align and mate along the second vertical axisspaced apart from the first vertical axisalong the second longitudinal axis.

Referring now to, in one non-limiting example, each of the first beadand the secondary beadmay be symmetrical across the first vertical axis. That is, the first shapeof the first beadmay match the second geometryof the secondary bead. Additionally or alternatively, each of the second beadand the primary beadmay be symmetrical across the second vertical axis. That is, the second shapeof the second beadmay match the first geometryof the primary bead.

However, referring to, in another non-limiting example, the first beadmay be symmetrical across the first vertical axisand the secondary beadmay be asymmetrical across the first vertical axis. That is, the first shapeof the first beadmay not match the second geometryof the secondary bead. Additionally or alternatively, although not shown, the second beadmay be symmetrical across the second vertical axisand the primary beadmay be asymmetrical across the second vertical axis. That is, the second shapeof the second beadmay not match the first geometryof the primary bead.

Referring now to, in another embodiment, each of the first shapeand the second geometryincludes a bottom fillet, a top filletspaced apart from the bottom fillet, a top, a bottomspaced apart from the top, a side wallconnecting the topand the bottom, and an angle of inclinationdefined between the bottomand the side wall. The angle of inclinationmay be greater than 0° and less than or equal to 90° so that the offset featuremay have a gradual transition between the bottomand the side wall.

For this embodiment, each of the first shapeand the second geometryis defined by at least one of a first variable set() and a second variable set(). The first variable setincludes a bottom fillet radius, a top fillet radius, a bottom half width, a top half width, and a bead height. The second variable setincludes the bottom fillet radius, the top fillet radius, the angle of inclination, a side wall height length, and the top half width.

The first variable setand/or the second variable setmay be iteratively optimized, for example, based on a feedback loop of Gaussian Process Regression and Bayesian Optimization and finite element analysis to thereby provide the first shapeof the first beadand the second geometryof the secondary bead. Further, design criteria and parameters based on the first variable setmay be correlated with and converted to design criteria and parameters based on the second variable set.

For example, using the first variable setor the second variable setof five independent variables, each side of the first beadacross the first vertical axisand each side of the secondary beadacross the first vertical axismay be parameterized to define the respective first shapeand second geometryof the beads,. Symmetric design of the two sides of the first beadand the two sides of the secondary beadmay not be required. However, for an asymmetric design, both sides of the first beadand/or secondary beadmay be defined by the first variable setand/or the second variable set. In addition, each side of the second beadacross the second vertical axisand each side of the primary beadacross the second vertical axismay be parameterized to define the respective second shapeand first geometryof the beads,. Symmetric design of the two sides of the second beadand the two sides of the primary beadmay not be required. However, for an asymmetric design, both sides of the second beadand/or primary beadmay be defined by the first variable setand/or the second variable set.

Further, the first shapeof the first beadand the second geometryof the secondary beadmay be identified independently or dependently. That is, the first shapeof the first beadmay be dependent on the second geometryof the secondary bead. Alternatively, the first shapeof the first beadmay be independent of the second geometryof the secondary bead. Similarly, the second shapeof the second beadand the first geometryof the primary beadmay be identified independently or dependently. That is, the second shapeof the second beadmay be dependent on the first geometryof the primary bead. Alternatively, the second shapeof the second beadmay be independent of the first geometryof the primary bead. Likewise, the first shapeof the first beadand the second shapeof the second beadmay be identified independently or dependently. That is, the first shapeof the first beadmay be dependent on the second shapeof the second bead. Alternatively, the first shapeof the first beadmay be independent of the second shapeof the second bead. In like manner, the first geometryof the primary beadand the second geometryof the secondary beadmay be identified independently or dependently. That is, the first geometryof the primary beadmay be dependent on the second geometryof the secondary bead. Alternatively, the first geometryof the primary beadmay be independent of the second geometryof the secondary bead.

In one non-limiting example best shown in, the first shapemay be dependent on the second geometry. That is, a design of the first shapemay depend on a design of the second geometry. In another non-limiting example best shown in, the first shapemay be independent of the second geometry. That is, the design of the first shapeand the second geometrymay not depend on one another.

The first and second shapes,and the first and second geometries,may also be constrained by other considerations such as manufacturing feasibility of the first rollerand associated beads,and second rollerand associated beads,. For example, referring to, for some applications, the bottom fillet radiusand the top fillet radiusmay be constrained by a minimum value. Similarly, the bottom half widthmay be greater than or equal to the top half width.

In addition, although the roller offset forming toolis described herein as including at least one bead pair, i.e., the first beadand the secondary bead, or in some embodiments, at least two bead pairs, i.e., additionally the primary beadand the second bead, the roller offset forming toolmay include more than four beads or two pairs of beads according to desired characteristics and location of the offset feature. For example, although not shown, the first rollermay include a third bead and a tertiary bead spaced apart from the third bead. Likewise, as a non-limiting example, the second rollermay include a fourth bead and a quaternary bead spaced apart from the fourth bead. The third bead may be configured to align with the quaternary bead and the fourth bead may be configured to align with the tertiary bead.

Advantageously, the roller offset forming tooloptimizes a stiffness of the workpiecewhile mitigating the distortionof the workpieceat areasapart from the offset featureby allowing for optimized first and second rollers,that include one or more mini-beads, e.g., the first beadand the secondary bead, disposed at calculated positions according to the desired offset featureand desired stiffness of the workpiece.

Referring now to, a roller offset forming systemmay include the metal sheetsandwiched between and disposed in contact with the first beadand the secondary beadof the roller offset forming tool. Likewise, the roller offset forming systemmay also include the metal sheetsandwiched between and disposed in contact with the primary beadand the second beadof the roller offset forming tool. The metal sheetmay be formed from any suitable metal according to an application or end use of the workpiece. In one non-limiting example, the metal sheetmay be formed from an aluminum alloy such as AA5754-O and may be from 1 mm to 1.5 mm thick.

Referring now to, the methodof mitigating the distortionof the workpieceincludes formingthe workpiecehaving the offset featureand a plurality of areas() each spaced apart from the offset featurefrom the metal sheetwith the roller offset forming tool. That is, formingmay include sandwiching the metal sheetbetween at least the first beadand the secondary bead, and in some embodiments, additionally between the second beadand the primary beadas set forth above. Further, formingmay include turning the first rollerin the first directionagainst the metal sheetand turning the second rollerin the second directionagainst the metal sheetsuch that the first beaddeforms the metal sheetat the secondary beadand thereby forms the offset feature.