Method and apparatus for shaping a rim of a three-dimensionally arched sheet metal

Method for shaping a rim of a three dimensionally arched sheet metal, wherein the sheet metal is placed on a female die provided with a chamfer which follows the contour of a peripheral edge of the rim, the rim spanning the chamfer, and a male roller die is rolled on the sheet metal following the course of the chamfer while being pressed against the rim, thereby plastically deforming the rim locally into the chamfer while advancing along the chamfer in rolling contact.

BACKGROUND OF THE INVENTION

The invention is directed to the shaping of a rim of a sheet metal which is three-dimensionally arched, and is in particular directed to shaping a rim of a sheet metal component to be attached to or being already part of a vehicle, the vehicle preferably being an automobile.

Sheet metal components of automobiles are usually three-dimensionally arched or shaped for example by deep-drawing a flat sheet metal. Such components have peripheral edges which might be sharp or of an anaesthetic appearance. In other cases, the rim of such components, including the peripheral edge, needs to be stiffened in order to maintain the desired shape under regular operating conditions. Conventionally the rims are shaped manually by flanging along the respective peripheral edge.

SUMMARY OF THE INVENTION

It is desirable to enable shaping of a rim along a curved edge of a three-dimensionally arched sheet metal in improved quality and cost-effectiveness to be applicable in series production.

In one aspect, the present invention is a method for shaping a rim of a three-dimensionally arched sheet metal, the method comprising the steps of placing the sheet metal on a female die which is provided with a chamfer which follows the contour of a peripheral edge of the rim. The edge comprises one or more curved section(s) or is curved all over its course. The edge may be curved only in one plane or in all three dimensions. The sheet metal is placed on the female die such that the rim spans the chamfer. The sheet metal my bear on the die with its weight, in principal however the die may be oriented vertically or almost vertically or may even be oriented such that the sheet metal is placed on a die surface from below. With the sheet metal placed on the female die, a male roller die is rolled on the sheet metal following the course of the chamfer while being pressed against the rim in a rim zone which spans the chamfer. Thereby the rim is plastically deformed into the chamfer locally, namely at the momentary place of rolling contact of the male roller die advancing on the rim along the chamfer. The sheet metal is deformed into the cavity provided by the chamfer in a forming process comparable to deep-drawing, but only in principal, since the forming process of the invention effects only a local deformation which advances, as the roller die does, and is therefore a very gentle forming process resulting in the formation of a dent along the sheet metal rim.

Use of a female die and a male roller die guarantees high reproducibility in shape. A roller die is not restricted to a certain course of a rim but can flexibly be used to shape rims of different courses, in particular if the roller die is part of a tool head arranged to be connected to an actor which is movable in space, for example, a robot arm.

In at least one embodiment, the rim comprises an inner rim zone spanning the chamfer and a peripheral rim zone which includes the peripheral edge and protrudes beyond the chamfer and preferably protrudes beyond the female die freely to improve accessibility. In an embodiment of the method, a back-up roller is rolled along the peripheral rim zone pressed against the peripheral rim zone towards the male roller die. The peripheral rim zone is backed-up by this action of the back-up roller, while the male roller die is pressed in a rolling contact against the inner rim zone. So the male roller die exerts a pressure force on the rim towards the female die while the back-up roller is in rolling contact with the peripheral rim zone in the vicinity of the place of momentary rolling contact of the male roller die. This way the male roller die also serves the purpose of a down holder for the back-up roller. It is advantageous if the sheet metal is already deformed into the chamfer during this combined roller action. A region in which a circumferential working surface of the male roller die meets with a face side of the male roller die may serve as a block against which the rim is in abutment to better define a flanging edge about which the rim is flanged while advancing the male roller die and the back-up roller, the flanging edge extending between the inner rim zone and the peripheral rim zone. The flanging edge is best defined if the peripheral rim zone is backed-up while the inner rim zone is actually or has already been deformed into the chamfer completely, i.e. is in abutment with the surface of the chamfer all over the chamfer's cross-section. Preferably, the male roller die is just deforming the inner rim zone in such a complete abutment while the peripheral rim zone is backed-up by the back-up roller.

The chamfer has two opposed side walls. The side wall being closer to a protruding peripheral edge of the rim and facing away from that edge is advantageously shaped such that it ends, at the rim where the chamfer transitions into the surface of the female die, parallel or at least almost parallel to the pressure force exerted by the male roller die in its rolling contact. Such a shape is advantageous for backing-up the peripheral rim zone and, furthermore, for a subsequent further flanging process in which the peripheral rim zone is bent back towards the chamfer by means of a hem roller. Subsequently bending back the peripheral rim zone is not necessarily the subject of the invention but is an advantageous further development in order to improve in particular the rim's appearance further.

As mentioned, the invention can advantageously be combined with a flanging process which is performed subsequent to the forming process in which the rim is deformed into the chamfer. In such a further development, after having deformed the rim into the chamfer, the male roller die is moved out of its previous working area and a hem roller is positioned to press against a surface of the sheet metal opposed to the surface against which the male roller die has been pressed before. The hem roller is now rolled along the peripheral rim zone following the course of the chamfer and acts on the peripheral rim zone such that it is bent back towards the chamfer. This flanging process is preferably carried out only subsequent to a back-up process, preferred features of which have been outlined above. The bending-back process may be carried out in only one roll pass of the hem roller or, preferably, in several passes, for example two or three passes, in order to bend back the peripheral rim zone so far that the peripheral edge protrudes into the cavity of the dent formed by deforming the rim into the chamfer. This covers embodiments in which the peripheral edge is only in a partial overlap with an opposing rim of the dent. It may be desirable that the peripheral edge is flush with this rim, a small clearance remaining between the peripheral edge and the rim of the dent.

In another aspect, the present invention provides an apparatus for shaping the rim, suited in particular for carrying out the method of the invention. The apparatus comprises a female die with a chamfer in a die surface on which the sheet metal can be placed, and a tool head arranged for being fastened to an actor of a robot. The robot can be an industrial robot with a robot base and a robot arm protruding therefrom. The base can be stationary in a working area of the robot. In most applications the actor is the end of the robot arm. The actor is preferably movable in space in all six degrees of freedom with respect to motion. The tool head comprises a male roller die shaped to mate with the chamfer for deforming the sheet metal into the chamfer by advancing the roller die in the course of the chamfer in a rolling contact with the sheet metal rim. The female die and the male roller die can advantageously be shaped and arranged to operate as outlined with respect to the method. The features already disclosed with respect to shape and arrangement are also preferred features of the apparatus.

The rim may be deformed into the chamfer in only one roller pass of the male roller die. In preferred embodiments, however, the forming process of deforming the rim into the chamfer is performed in more than one roller pass, either with different male roller dies or preferably with the same male roller die. Deforming into the chamfer in more than one pass is advantageous with respect to quality since the forming process can be performed more gentle per pass. An advantageous compromise between quality requirements and time constraints is achieved when the rim is deformed into the chamfer in two or three roll passes. Also, two or three male roller dies may be arranged on the tool head in a tandem or triple arrangement, one following the other in the direction of advancement and all acting on the rim in the same roll pass.

In at least one embodiment, the tool head further comprises a back-up roller disposed aside, preferably adjacent to the male roller die. The axis of rotation of the back-up roller is inclined with respect to the axis of rotation of the male roller die such that a circumferential working surface of the back-up roller is facing a face side of the male roller die. The axes can be inclined under an angle of 90°, preferably they are inclined at an angle smaller than 90° e.g. an angle in the range of 30° to 70°. The arrangement is such that the male roller die can roll on a first surface of the sheet metal rim while the back-up roller rolls on a second surface of this rim, the surfaces being disposed on opposite sides of the sheet material and being inclined one relative to the other, at least after the back-up roller has acted on the second surface. Most preferred, the first surface is a surface of the inner rim zone and the second surface is a surface of the peripheral rim zone. The axes of rotation may extend in two different planes, although not preferred. In such embodiments the planes are parallel with only a small offset. If such an offset is present, the back-up roller is arranged such that it closely follows the male roller die during advancement along the course of the chamfer. Expediently the axes of the rollers are extending in the same plane.

In another embodiment, the back-up roller is movably supported on the tool head to be adjustable with respect to the male roller die. In such embodiments, the tool head further comprises an adjusting unit coupled with the back-up roller to adjust the position of the backup roller. The back-up roller is preferably movable in the plane of its axis of rotation and in at least one degree of freedom with respect to motion, which can be a translational or rotational degree of freedom. The invention uses the word “or” in it's usual logical meaning, i.e. as an “inclusive or” covering the meaning of “either: or” as well as the meaning of “and”, as long as the respective context does under no circumstances allow for one of the two meanings. So the back-up roller may be movably supported on the tool head and accordingly be adjustable in only one translational, only one rotational, one translational and one rotational or in two translational and one rotational degree of freedom in that plane. Preferably, the back-up roller is movable back and forth parallel to the axis of rotation of the male roller die. Such a movability is advantageous for adjusting the position to adapt for varying thicknesses of different metal sheets or the same metal sheet and also for moving the back-up roller so far apart from the male roller die that is cannot interfere when positioning the tool head on the sheet metal or in a pre-forming roll pass of the male roller die, which can in particular be a first roll pass of the male roller die.

A preferred apparatus comprises a hem roller arranged such that the male roller die and the hem roller can selectively be used to act on the sheet metal.

The method can be carried out, in particular, with the female die being stationary and the roller or several rollers mentioned before being moved in space during the forming process or the several forming processes, i.e. the deforming into the chamfer, the backing-up and the bending back. Alternatively, the roller or several rollers can be kept stationary while the female die is moved in space to pass it together with the sheet metal along the stationary roller(s) according to the course of the chamfer. In yet another alternative embodiment the female die can be also a roller die and can even be a roller die arranged on another or the same tool head of the apparatus of the invention such that the circumferential working surfaces of the female roller die and the male roller die are opposedly facing one another.

A tool head comprising the male die roller and the back-up roller is advantageous as such, not only in combination with the female die, but is however a preferred subject-matter in combination with the female die.

Lastly, the invention is also concerned with a sheet metal component with a rim which has been shaped by the method of the invention. Subject-matter is the component as such before assembling and also in the assembled state forming part of a higher-level assembly. Particularly, the component can be part of or intended for attachment to a vehicle, preferably an automobile. A preferred example of such a component is a fender of or for an automobile. Most preferred applications are retro-style automobiles.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a retro-style automobile having fenders1attached to an automobile body. The fenders1are three-dimensionally arched sheet metal components each with a shaped rim2along its peripheral edge. The rim2is shaped as a softly curved dent which does not only stiffen the respective fender1but also improves the overall appearance. The rims2are shaped in an automated process, which delivers high quality shaping and meets the needs of series production.

An apparatus for carrying out the process is composed of a female die7, shown inFIG. 2, and a tool head10comprising a male roller die12, shown inFIG. 3.

The female die7comprises a surface8adapted to the shape of a three-dimensionally arched sheet metal. In the example given above the sheet metal is one of the fenders1and is therefore referred to as sheet metal1in the following. The female die7furthermore comprises a chamfer9in the surface8, the chamfer9being close to one edge of the female die7. The chamfer9, and also the free die edge in its vicinity, follows the contour of a peripheral edge of the rim2of the sheet metal1. For the sheet metal1being one of the fenders1the course of the chamfer9is a three dimensional curve.

In the example embodiment the chamfer9has a width which is larger than its depth, as is preferred not only for the example of the sheet metal1being a fender of an automobile but also in general for carrying out the method of the invention. The chamfer9has a cross-section which is preferably the same over the whole length of the chamfer9. The chamfer9may have a width in the range from e.g. 5 mm to e.g. 50 mm, the width preferably being constant over the length of the chamfer9.

The tool head10comprises a fastening member11for fastening the tool head10to the end of a robot arm. The fastening member11preferably provides not only for mechanical fastening but also for supply of the tool head10with media required for its operation, for example electrical energy, control signals or pressure fluid. The fastening member11can in particular be a docking member for an automatic docking and separating to and from the robot arm. The tool head10comprises a male roller die12mounted to be rotatable about a roller axis R12. The roller axis R12can be stationary on the tool head10. The roller die12has a circumferential working surface in a shape which mates with the chamfer9in order to operate as the male die part to the female die7.

The tool head10comprises in addition a back-up roller13mounted rotatably about its roller axis R13and furthermore movable as a whole relative to the male roller die12. The back-up roller13can be moved back and forth between a working position, shown inFIG. 3, and a non-working position in which it is further away from the male roller die12. To be movable as a whole the back-up roller13is mounted rotatably about its roller axis R13by a support structure15which is movable back and forth such that by this movement the back-up roller13is moved in and out of its working position. In the example embodiment the support structure15is a slide being movable along an axis which is parallel to the roller axis R12. The tool head10also comprises an adjustment unit16to position the back-up roller13in relation to the male roller die12. The adjustment unit16is a linear drive connected to the support structure15.

Lastly, the tool head10also comprises a hem roller14mounted rotatably about its roller axis R14. The hem roller14is arranged such that either one of the male roller die12and the hem roller14can selectively be positioned relative to a work piece, e.g. a sheet metal1placed on the female die7, by the movement of the robot arm.

The male roller die12and the back-up roller13are arranged such that their roller axes R12and R13both extend in the same plane. The roller axis R13is inclined with respect to the roller axis R12. The angle of inclination is not so important with respect to the basic function of the back-up roller13but is expediently chosen under the influence of space which is only rarely available on the tool head10. In principal, the axes R12and R13can extend under an angle of inclination of 90°. With respect to function it is more important that a circumferential working surface of the back-up roller13is facing the face side of the male roller die12. In the example embodiment the circumferential working surface, i.e. the rolling surface, of the backup roller13is extending perpendicular to the axis R12of the male roller die12. The axis R13of the back-up roller13is fixed in relation to the support structure15, but may be adjustable in it's inclination with respect to the axis R12in a further development. The working surface of the back-up roller13is conical in adaptation to the inclination the roller axis R13has in relation to the roller axis R12.

FIG. 4illustrates co-operation of the female die7and the tool head10in shaping the rim2of a metal sheet1. Shown is a roll pass of the tool head10in which the male roller die12is deforming the rim2into the chamfer9while, at the same time, the back-up roller13is backing up an outermost part of the rim2.

FIGS. 5-9illustrate a method of shaping the rim2in a plurality of roll passes to be carried out sequentially one after the other, thereby roll forming the rim2stepwise to the desired shape.FIG. 5illustrates the first step in which the three-dimensionally arched sheet metal1ofFIG. 4is placed on the female die7in a forming position in which the rim2is following the course of the chamfer9. The sheet metal1is fixed in the forming position, for example by clamping it against the female die7. In the forming position the rim2can virtually be divided in an inner rim zone3spanning the chamfer9and a peripheral rim zone4protruding beyond the chamfer9. The peripheral rim zone3including the peripheral edge5protrudes freely from the die7which has only a small web forming the side wall of the chamfer9adjacent to the peripheral edge5, this web being small as compared to the width of the chamfer9.

With the metal sheet1fixed in the forming position the tool head10is moved to a predetermined position and is then applied to the metal sheet1such that the male roller die12contacts the inner rim zone3. The male roller die12is pressed against the inner rim zone3with a pre-determined pressure force and the tool head10is moved in space by the robot to roll the male roller die12on the inner rim zone3following exactly the course of the chamfer9with the male roller die12pressing the sheet material1into the cavity provided by the chamfer9with the pre-determined pressure force. The pressure force is selected to deform the sheet metal1plastically only to a certain extend, not completely, into the cavity provided by the chamfer9. If necessary, a second pre-forming roll pass is carried out with the male roller die12being in pressing rolling contact with the inner rim zone3to deform it deeper into the chamfer9. While advancing the male roller die12in such a pre-forming roll pass, the peripheral rim zone4flips up, as indicated inFIG. 6, improving access for the back-up roller13. The peripheral rim4of that portion of the sheet metal1which is ahead of the male roller die12, with respect to its advance direction, is plotted in a dashed line. In the course of a curve of the chamfer9the peripheral rim4does not flip up so much as it would in a straight section. Furthermore, there is a tendency that wavy distortions develop within the peripheral rim zone4.

At least in a final roll pass of the male roller die12, shown inFIG. 7, the back-up roller13is also applied against the sheet metal1. While the male roller die12is pressed, in the inner rim zone3, against a first surface of the sheet metal1, the back-up roller13is pressed, in the peripheral rim zone4, against an opposed second surface of the peripheral rim zone4, thereby flanging the peripheral rim zone4about a flanging edge which extends between the inner rim zone3and the peripheral rim zone4along the rim of the chamfer9. In the final forming pass of the male roller die12the sheet material1is deformed such that it is in full abutment all over the cross-section of the chamfer9to form the rim2as a dent6corresponding in cross-sectional shape to that of the chamfer9.

The single or plural pre-forming roll passes may be carried out with only the male roller die12being applied to the sheet metal1. Alternatively, the single or plural pre-forming pass(es) may be carried out with also the back-up roller13being applied to avoid development of wavy distortions from the beginning or at least after a first pre-forming roll pass in which the peripheral rim zone4is flipped up to some extend to facilitate access for the back-up roller13.

When the male roller die12has completed its final forming pass the robot moves the tool head10apart to bring the hem roller13into a working position. Then the tool head10is moved again to a pre-determined position and applied against the sheet metal1, now with the hem roller13coming into contact with the peripheral rim zone4. The hem roller13is pressed against the peripheral rim zone4, as shown inFIG. 8, and rolled on that zone4following the course of the chamfer9. In this hemming roll pass the peripheral rim zone4is flanged towards the chamfer9, i.e. towards the cavity of the dent6, the flanging angle being 45°. The peripheral zone4which is in front of the hem roller13and still in its flipped up position during the first hemming roll pass is plotted in a dashed line.

FIG. 9shows the hem roller13during a second roll pass in which the peripheral rim zone4is flanged back further about 45°, such that it is flush with the opposing rim of the dent6with only a small clearance between that rim and the peripheral edge5, thereby forming the dent6as an almost closed cavity.

The method has been exemplified with two hemming roll passes of the same hem roller13. Alternatively, the peripheral rim4may be flanged back in three or even more hem rolling passes, e.g. in three passes with a flanging angle of 30° each. Furthermore, the tool head10may comprise two or more different hem rollers and the hemming roll passes may be carried out with the different hem rollers being applied to the sheet metal1. Lastly, two or even more hem rollers may be arranged on the tool head10as disclosed in EP 06 001 600.3 incorporated herewith by reference. To compensate for back spring, i.e. elasticity of the sheet metal1, the hem roller13or some other hem roller if arranged on the tool head10, may be applied such that the peripheral edge4is flanged back more and over the position in which it is flush with the opposing rim of the dent6so that it comes back to the desired position once it is released from the pressure force of flanging.