Method and apparatus for double-sided incremental flanging

Abstract

Flanges formed on sheet metal parts to increase the part stiffness or create mating surface for further assembly are created in an incremental sheet forming process using forming tool and supporting tool that move along a specified tool path so as to gradually deform a peripherally-clamped sheet metal work piece into the desired geometry. With two universal tools moving along the designed toolpath on the both sides of the part, the process is very flexible. Process time is can also be reduced by utilizing an accumulative double-sided incremental hole-flanging strategy, in which the flange is formed in only one step.

Claims

1. A double-sided incremental forming tool for forming a flange in a work piece defining an X-Y plane, the flange to be formed defining a profile having a first portion in the X-Y plane of the work piece, a second portion extending in a direction out of the X-Y plane of the work piece, the tool comprising: a forming member configured to be mounted in a first tool holder, the forming member comprising a first forming surface defining the profile of the flange, with the first forming surface parallel to the X-Y plane of the work piece; and a support member configured to be mounted in a second tool holder, the support member comprising a first forming surface also defining the profile of the flange and complementary to the first forming surface of the forming member; wherein the flange to be formed thereby has a second portion extending perpendicularly to the plane of the work piece in a Z direction and a fillet having a radius of curvature intermediate the first and second portions; wherein the forming member comprises three forming surfaces, with a second forming surface extending in the Z direction perpendicular to the X-Y plane of the work piece, and a third forming surface intermediate the first and second forming surfaces having a radius of curvature corresponding to the radius of curvature of the fillet; the support member comprises three forming surfaces, with a second forming surface extending in the Z direction perpendicular to the X-Y plane of the work piece, and a third forming surface intermediate the first and second forming surfaces having a radius of curvature corresponding to the radius of curvature of the fillet; and wherein the forming member has a diameter of the forming member that is greater at the first forming surface of the forming member than a diameter of the forming member at the second forming surface of the forming member.

2. The tool of claim 1 wherein the second forming surface of the forming member and the first forming surface of the support member have a length in the Z direction greater than or equal to the height of the flange.

3. The tool of claim 1, wherein the first tool holder and the second tool holder are configured to move in unison in the X-Y plane, maintaining a fixed spacing between the forming tool and the support tool, to continuously engage an edge of the work piece.

4. The tool of claim 3 wherein the first tool holder and the second tool holder are configured to move in a concentric path in the X-Y plane from the edge of work piece aperture outward in incremental steps, with each successive incremental step being smaller than the preceding step.

5. The tool of claim 3 wherein the first tool holder and the second tool holder are moved in the X-Y plane from the edge of the work piece outward in a spiral path, with each successive orbit in the spiral a being smaller step than the preceding step.

6. The tool of claim 3, wherein the forming tool and the support tool are spaced apart a distance corresponding to a dimension of the work piece in a vertical direction.

7. The tool of claim 3, wherein the forming tool and the support tool are spaced apart a distance corresponding to a dimension of the work piece in a horizontal direction.

8. A double-sided incremental forming tool for forming a flange in a work piece defining an X-Y plane, the flange to be formed defining a profile having a first portion in the X-Y plane of the work piece, a second portion extending in a direction out of the X-Y plane of the work piece, the tool comprising: a forming member configured to be mounted in a first tool holder, the forming member comprising a forming surface defining the profile of the flange, with a first forming surface parallel to the X-Y plane of the work piece; and a support member configured to be mounted in a second tool holder, the support member comprising a forming surface also defining the profile of the flange and complementary to the forming surface of the forming member; wherein the forming surface of the forming member includes a concave shaped shoulder portion encircling an entire outer circumference of the forming member; and wherein the forming surface of the support member includes a convex shaped tip portion encircling an entire outer circumference of the support member wherein the forming member has a first outer diameter on a first side of the concave shaped portion that is greater than a second outer diameter on a second side of the concave shaped portion.

9. The tool of claim 8, wherein the forming member includes a vertical wall portion extending outward from the concave shaped shoulder portion.

10. The tool of claim 9, wherein the support member includes a vertical wall portion extending outward from the convex shaped tip portion.

11. The tool of claim 10, wherein the vertical wall portion of the support member extends downward.

12. The tool of claim 11, wherein the vertical wall portion of the forming member extends upward.

13. The tool of claim 10, wherein the first tool holder and the second tool holder are configured to move in unison in the X-Y plane, maintaining a fixed spacing between the forming tool and the support tool, to continuously engage an edge of the work piece.

14. The tool of claim 13 wherein the first tool holder and the second tool holder are configured to move in a concentric path in the X-Y plane from the edge of work piece aperture outward in incremental steps, with each successive incremental step being smaller than the preceding step.

15. The tool of claim 13 wherein the first and second tool holders are moved in the X-Y plane from the edge of the work piece outward in a spiral path, with each successive orbit in the spiral a being smaller step than the preceding step.

16. The tool of claim 13, wherein the forming tool and the support tool are spaced apart a distance corresponding to a dimension of the work piece in a vertical direction.

17. The tool of claim 16, wherein the forming tool and the support tool are spaced apart a distance corresponding to a dimension of the work piece in a horizontal direction.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a simplified perspective view of a double-sided incremental flanging apparatus according to the present disclosure.

(2) FIG. 2 is a simplified cross-sectional view showing the double-sided incremental flanging process according to the incremental forming apparatus of FIG. 1.

(3) FIG. 3 is a fragmentary side view showing the tools for use in the incremental flanging apparatus and method of the present disclosure.

(4) FIG. 4 is a plan view showing a blank or work piece having a circular aperture for use in the incremental flanging apparatus and method of the present disclosure.

(5) FIG. 5 is a perspective view of a target geometry according to the incremental flanging apparatus and method of the present disclosure.

(6) FIG. 6 is a fragmentary side view illustrating the incremental flanging process according to the prior art.

(7) FIG. 7 is a side view of three different products created by the incremental flanging process according to the prior art.

(8) FIG. 8 is the photograph of a product created by the incremental flanging process according to the present disclosure.

(9) FIG. 9 is the photograph of an asymmetric product created according to the incremental flanging process of the present disclosure.

(10) FIGS. 10(a)-10(f) are examples of alternative profiles for flanges that may be made according to the tool and method described herein.

(11) FIG. 11 shows two alternative tool paths, concentric and spiral, that may be utilized in the method described herein.

DETAILED DESCRIPTION OF THE INVENTION

(12) In accordance with the present method, a one-stage hole-flanging strategy is employed in which the forming tool and support tool are moved in unison from an initial position engaging the edge of the aperture formed in the work piece in an outward direction until the desired boundary of the flange is achieved, with the space between the complementarily-shaped surfaces of the working tool and the supporting tool corresponding to the thickness of the work piece. The tool path is essentially only in the plane of the work piece (the X-Y plane, as illustrated), and provides a forming zone in a line, with the relative positions of the forming tool and support tool being fixed.

(13) Thus, the supporting tool engages the blank along the boundary of the forming area, rather at the target boundary. Further the forming and supporting tools engage the work piece in a line of contact. Such a tool path forms the vertical-wall directly, and has been found to achieve better geometric accuracy and changes the thickness distribution. Furthermore, with the fillet controlled by the supporting tool radii, the bulge in the unformed area is almost eliminated, and complex profiles including both shrink flanges and stretch flanges can be successfully achieved.

(14) To illustrate the flanging process, a circle hole-flanging cross section is shown and described. In a circular flange, a “shrink flange” is formed. However, it should be understood that the apparatus and method are also applicable to forming asymmetric flanges and flanges that include both shrink flange portions and stretch flange portions.

(15) FIG. 5 illustrates an exemplary target geometry for the flange to be formed. In this example, flange 20 is the target feature on part 10. It contains fillet 20a and vertical wall 20b (as shown in FIG. 7). As shown in FIG. 1, incremental forming apparatus 100 comprises a lower clamp 110 and an upper clamp 120. The blank 10 is mounted between the lower clamp 110 and upper clamp 120. Further details as to the forming apparatus may be found in, e.g., U.S. Pat. No. 9,168,580, which is incorporated herein by reference.

(16) A forming tool 150 and supporting tool 160 are provided that are mounted in tool holders/spindles (not shown) so as to be disposed on each side of the blank and movable relatively along the X, Y and Z direction. With reference to FIG. 2, the, tool 150 is moved to touch the edge 10a of the aperture in the blank (as shown in FIG. 4, in which 10a is the initial hole for flanging, which can be obtained with laser cutting or water jet cutting). The tools are then moved from inside out in the in-plane direction.

(17) More specifically, the shoulder of tool 150 (150c in FIG. 3) contacts the blank surface and the edge 10a touches the fillet of tool 150. At the same time, tool 160 is moved to contact the other side of the blank 10 while keeping the distance between tool 150 and tool 160 in both the Z direction and in-plane direction to correspond to the blank thickness.

(18) Next, tool 150 and tool 160 are gradually moved together along a tool path from inside to outside in an in-plane direction (either in concentric or a spiral shapes, as shown in FIG. 11), with the distance between them being maintained. During this process, the blank material is bent and flows along the curvature of the tool from in-plane direction to vertical direction. Flange 20 (as shown in FIG. 5) is achieved. With reference to FIG. 11, from one orbit of the flow path to the next, the incremental change in the radius, dRn, (or, more specifically, the space between consecutive orbits) decreases from the inside of the aperture out. Thus, as the forming process proceeds, and the line of contact or forming line between the forming member, the support member, and the work piece increases, the incremental change is decreased in order to control the force exerted on the work piece in the X-Y plane.

(19) With reference to FIG. 3, details of the tools 150 and 160 for making the exemplary target geometry are shown. Specifically, both tools are designed to create the designed flange 20 in FIG. 5. Shoulder 150c and tip 160c works together to maintain the Z level of the blank. Curve 150b and curve 160b work together to guide the material flow and control the fillet of the flange 20. Vertical walls 150a and 160a constrain the achieved flange. Shoulder 150c and tip 160c may be revised according to the achieved part geometry before flanging. Curve 150b and 150c can be redesigned according to the desired flange cross section shape. 160b and 160c are designed to cooperate with 150b and 150c. The in-plane lengths of 150c and 160c can be adjusted to avoid possible collision with the part.

(20) More particularly, it should be appreciated that the profiles of the tools 150 and 160 can be varied to create flanges having numerous different profiles, as long as profiles of the tools corresponds to the profile of the flange to be created, so that the line of contact defined by the tools is the same as the profile of the flange. Examples of different flange profiles that may be created using the method and tool described herein are shown in FIGS. 10(a)-10(f).

(21) The tool and method have been used to create flanges in work pieces. FIG. 8 is a circle flange part formed with present method. FIG. 9 is an asymmetric flange part, having both shrink flange portions (where the curve of the flange is an outside curve, like in a circular flange) and stretch flange portions (where the curve of the flange is an inside curve) formed with the present method.