METHOD AND SYSTEM FOR METAL DRAWING AND REDRAWING
A system and method of forming a drawn cup for production of a metal container is provided. The system and method contemplates the provision of gap pins to control the relative movements of cup forming features and provide for reduced risk of damage including pinching, chatter, slivering, and thinning of portions of the cup.
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This U.S. Non-Provisional Patent Application claims the benefit of priority from U.S. Provisional Patent Application Ser. No. 61/808,111, filed Apr. 3, 2013, the entire disclosure of which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTIONThe present invention relates to methods, systems and devices for drawing and redrawing a metal blank that reduces the occurrence of chatter, hairs, pinching, slivers, and thinning in the formed material. More specifically, the present invention relates to methods, systems and devices for drawing and redrawing metal containers and components thereof, including cups, from a blank of metal stock material that reduce defects in the final product.
BACKGROUND“Draw and reverse draw” processes for forming a can body are known in the art. In general, a metal sheet is clamped with pins, dies and other similar devices to secure positioning of various features. However, the existing tools and methods frequently create pinching in the metal and the formation of “hairs” or “slivers”. Pinching occurs at circumferential portions of a sidewall during cup formation. Pinching results in undesired anomalies in the formation process, including the hairs and slivers in the formed cup which are unsightly and problematic in the container manufacturing industry.
SUMMARYThus, a long-felt and unmet need exists for providing a draw and redraw process whereby pinching of the cup is reduced or eliminated. The present invention provides systems and methods for drawing and redrawing a cup for a metallic container, wherein gap pins are provided for securing and indexing a sheet of stock material, and for controlling or limiting relative positioning of dies and pads.
In operation, a plurality of small blanks, which are designed to receive the guide pins, are initially punched through a metal sheet (typically, an aluminum alloy sheet) as it is indexed. The small blanks surround and/or correspond to the perimeter of a blank that will be deformed in a subsequent draw/redraw process. After forming operations, the sheet is indexed again whereby the blank is located within the cupper tooling. Then, in the next cycle, the following sequence occurs substantially simultaneously: the blank and draw die, which are associated with guide pins, is moved towards the blank and the draw pad such that the ends of the guide pins are received within the small blanks previously punch through the sheet; just before the bottom surface of the blank and draw die contacts the upper surface of the draw pad, the blank and draw die contacts the upper surface of the sheet and forces it against the blanking die cut edge, which sheers the sheet to form a generally circular blank; in conjunction with the movement of the blank and draw die and the draw pad, the die center form punch and upper pressure sleeve are moved towards the also moving draw die; the draw die contacts the bottom surface blank which deforms it in a first direction; the die center form punch contacts the upper surface of the sheet in a second direction to create the finished shape; and the upper pressure sleeve works in conjunction with the upper surface of the draw die to pinch a portion of the blank during final forming of the blank by the die center form punch.
During this process, the guide pins contact an upper surface of the blanking die cut edge just after the blank and draw die create the circular blank. Thus the guide pins prevent contact between the lower surface of the blank and draw die and the draw pad, which allows the material of the blank to be sufficiently constrained during forming operations while allowing the blank material to move laterally with respect to the center axis of the cupping apparatus. This gap provided by the gap pins between the lower surface of the blank and draw die and the upper surface of the draw pad prevents warping of the blank and/or shearing thereof.
In various embodiments, methods of forming a drawn cup having a circular sidewall and an endwall are provided. In one embodiment, a method of forming a drawn and redrawn container body is provided, the method comprising providing a sheet of stock material comprising a plurality of preformed holes for receiving gap pins and positioning said sheet; providing a forming tool, the forming tool comprising: (i) a draw die; (ii) a draw pad; (iii) a blank and draw die; (iv) a center punch; and (v) a plurality of gap pins. The gap pins are provided through said preformed holes, such that said center punch and said draw die are aligned substantially coaxially with a blank to be formed. The gap pins preferably contact the draw pad at certain portions of the method, in contrast with known systems and methods wherein pins do not pass through the sheet of stock material or contact other components of the forming tool. A blank to be formed is provided between the draw pad and the blank and draw die, and a gap between the draw pad and the blank and draw die is approximately equal to a gauge of said sheet. The stock material is sheered into a circular shape by cutting the sheet with a cut edge of the blanking die. The generally circular blank is formed into a first shape by moving the draw die in a first direction and contacting a lower surface of the blank, wherein a portion of the generally circular blank conforms to the draw die under pressure, and wherein the generally circular blank is transitioned out of a space between the draw pad and the blank and draw die. The distal ends of the gap pins then contact a flange portion of said draw pad. Subsequently, an upper surface of the stock material is impacted with the center punch in a second direction to create a second shape, the second shape comprising a cup with a sidewall and an endwall. The tooling components are thereafter separated, allowing the cup to be extracted, and the tooling and sheet indexed or moved relative to each other to enable subsequent forming operations.
The gap pins and methods of use described herein provide a stand off height between tooling components and prevent pinching which is known to cause hairs or slivers in the formed cup.
The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. Moreover, references made herein to “the present invention” or aspects thereof should be understood to mean certain embodiments of the present invention and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description of the Invention and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detail Description, particularly when taken together with the drawings.
Referring now to
Referring now to
Subsequently, and referring now to process step 50, the gap pins are pushed or biased against the draw pad and create a predetermined off-set or clearance between the draw pad and the draw die. Near the end of the operation, the aluminum area is greatly reduced and ears or peripheral edges become the last points of contact between the draw pad and the blank. The gap pins of the present invention are provided to create an off-set clearance, and the ears are therefore not stressed to the point of failure. Thus, hairs and slivers are reduced or eliminated by the aluminum shearing of the present invention. In various embodiments, it is contemplated that the off-set clearance provided by the gap pins is slightly smaller than the aluminum gauge. For example, the present invention contemplates clearance ranges of between approximately 0.0100 inches and approximately 0.0140 inches.
At process step 52, a reverse redraw operation is provided to complete the formation of the cup. An inner shut height, which comprises a gap distance between the draw pad and the blank and draw die, is controlled via “lift-off” timing. In certain embodiments of the present invention, an inner shut height is approximately 31 inches, with a tolerance of +/−0.050 inches, and an outer shut height is approximately 24.50 inches, with a tolerance of +/−0.060 inches. It will be recognized, however, that these values may vary widely based on various machine and tooling design. In various embodiments, the tooling of the present invention provides a pressure to the metal being formed or shaped throughout substantially the entire forming process. At or near the end of the forming process, pressure in the tooling is relieved by a separation of the components described herein. The lift-off timing of the present invention, which is at least in part a function of the shut heights, prevents clamping of the cup “ears” and thereby prevents hairs, pinching, and slivers associated with prior art devices and methods.
In a preferred embodiment, a gap between the draw pad and the blank and draw die after the reverse redraw step is less than the gauge of the blank, and is dictated by the distal ends of the gap pins which extend a predetermined distance away from the blank and draw die, and preferably extend through the blanking die.
At process step 54 the cup is re-drawn to a final desired shape, preferably by a downward movement of the center form punch. After this formation, the tooling is retracted or released at step 56. Process steps 46-56 may be repeated as desired with a single sheet or the entire process may be repeated by provision of a new sheet.
In certain embodiments, a gap 21 between the draw pad 12 and at least one gap pin 16 is provided in the process steps of
In various embodiments, pneumatic compressed air provides a pressure to one or more of the tooling components shown and described herein. For example, an upper tooling component, such as the pressure sleeve 6 may be provided with an “inner” air pressure, which applies a clamp pressure as shown in
Claims
1. A method of forming a drawn metallic cup having a sidewall, and a dome comprising:
- providing a sheet of stock metal material;
- forming a plurality of through holes in the sheet, the through holes provided for receiving gap pins of a forming tool;
- providing a forming tool, the forming tool comprising: i. a draw die; ii. a draw pad; iii. a blank and draw die; iv. a center punch; and v. a plurality of gap pins;
- providing said gap pins through said through holes such that distal ends of said gap pins are provided proximal a flange portion of said draw pad;
- wherein the stock material to be formed is provided between said draw pad and said blank and draw die;
- sheering the sheet to form a generally circular blank;
- forming the generally circular blank into a first shape by moving the draw die in a first direction, wherein a portion of the generally circular blank conforms to the draw die under pressure, and wherein the generally circular blank is transitioned out of a space between the draw pad and the blank and draw die;
- contacting said flange portion of said draw pad with the distal ends of the gap pins;
- contacting an upper surface of the stock material with the center punch travelling in a second direction which is substantially an opposite direction as the first direction to form the blank in a second shape.
2. The method of claim 1, wherein the forming tool further comprises a blanking die.
3. The method of claim 2, wherein the blanking die comprises a cutting edge for sheering the sheet.
4. The method of claim 2, wherein the gap pins extend through apertures in said blanking die.
5. The method of claim 1, wherein prior to forming the generally circular blank into the first shape, a gap between said draw pad and said blank and draw die is approximately equal to a gauge of said sheet of stock material.
6. The method of claim 1, wherein after forming the generally circular blank into the first shape, a gap between said draw pad and said blank and draw die is less than a gauge of said sheet of stock material.
7. The method of claim 1, further comprising indexing said sheet of stock material and performing further drawing and redrawing operations.
8. A method of forming a drawn and redrawn container body, the method comprising:
- providing a sheet of stock material comprising a plurality of preformed holes for receiving gap pins and positioning said sheet;
- providing a forming tool, the forming tool comprising:
- a draw die;
- a draw pad;
- a blank and draw die;
- a center punch; and
- a plurality of gap pins;
- providing said gap pins through said preformed holes, such that said center punch and said draw die are aligned substantially coaxially with a blank to be formed;
- wherein said blank to be formed is provided between said draw pad and said blank and draw die, and a gap between said draw pad and said blank and draw die is approximately equal to a gauge of said sheet;
- sheering the sheet to form a generally circular blank;
- forming the generally circular blank into a first shape by moving the draw die in a first direction, wherein a portion of the generally circular blank conforms to the draw die under pressure, and wherein the first shape is withdrawn from a space between the draw pad and the blank and draw die;
- wherein an upward movement of the draw pad is limited by the gap pins wherein distal ends of the gap pins contact a flange portion of the draw pad; and
- contacting an upper surface of the stock material with the center punch in a substantially opposite direction as the first direction to create a second shape comprising a cup.
9. The method of claim 8, wherein the forming tool further comprises a blanking die.
10. The method of claim 9, wherein the blanking die comprises a cutting edge for sheering the sheet.
11. The method of claim 9, wherein the gap pins extend through apertures in said blanking die.
12. The method of claim 8, wherein prior to forming the generally circular blank into the first shape, a gap between said draw pad and said blank and draw die is approximately equal to a gauge of said sheet of stock material.
13. The method of claim 8, wherein after forming the generally circular blank into the first shape, a gap between said draw pad and said blank and draw die is less than a gauge of said sheet of stock material.
14. The method of claim 8, wherein the gap pins prevent said draw pad from contacting said blank and draw die.
15. The method of claim 8, further comprising indexing said sheet of stock material and performing further drawing and redrawing operations.
16. A device for forming and reforming a drawn cup for a metal container body, the device comprising:
- a forming tool comprising a draw die, a draw pad, a blank and draw die, a center punch, a blanking die and a plurality of gap pins;
- wherein the draw die is provided substantially coaxial with and movable relative to at least one of the draw pad and the blank and draw die;
- wherein the gap pins comprise a first end, a second end and a predetermined length therebetween;
- the first ends of the gap pins are secured to the blank and draw die such that the second ends of the gap pins are provided at a fixed distance relative to the blank and draw die; and
- wherein a shut height between the draw pad and the blank and draw die is limited by said gap pins.
17. The device of claim 16, further comprising a blanking die, the blanking die comprising a cutting edge adapted for cutting a circular blank of material to be deformed by the device.
18. The device of claim 16, wherein at least one of the draw pad and the blank and draw die comprise an internal void and wherein the draw die is translatable within said internal void.
19. The device of claim 16, wherein an outer circumference of the draw die corresponds to an internal diameter of a cup to be formed.
20. The device of claim 16, wherein the draw die comprises an annular feature adapted to receive the center punch during reforming of a cup.
Type: Application
Filed: Apr 3, 2014
Publication Date: Oct 9, 2014
Applicant: Ball Corporation (Broomfield, CO)
Inventor: Matthias van de Liefvoort (Louisville, CO)
Application Number: 14/244,198
International Classification: B21D 22/24 (20060101); B21D 28/02 (20060101); B21D 35/00 (20060101);