Forming process for stamped workpieces
Disclosed herein is a method of making a stamped workpiece from a base material sheet. The base material sheet has a thickness and defines a first plane. The stamped workpiece, upon completion of the process, has a protrusion and a crease line substantially adjacent thereto. The crease line divides the stamped workpiece into a first section and a second section. The method comprises a number of steps. One step in this method is the provision of at least one protrusion in the base material sheet. A workpiece periphery is defined in the base material sheet, the periphery bounding an area of the base material sheet. The area has a first section and a second section. The workpiece periphery adjacent to the first section is substantially separated from the remainder of the base material sheet. The first section is bent away from the first plane along a crease line. The thickness of the base material sheet along the crease line is then substantially reduced. The workpiece is detached from the base material sheet along the workpiece periphery. Optionally, the workpiece may be a tab opener for a food or beverage can.
1 . A method of making a stamped workpiece from a base material sheet, said base material sheet having a thickness and defining a first plane, the stamped workpiece having a protrusion and a crease line substantially adjacent thereto, the crease line dividing the stamped workpiece into a first section and a second section, the method comprising the steps of:
a) providing at least one protrusion in said base material sheet;
b) defining a workpiece periphery in said base material sheet, said periphery bounding an area of said base material sheet, said area having a first section and a second section;
c) substantially separating said workpiece periphery adjacent to said first section from the remainder of said base material sheet;
d) bending the first section away from said first plane along a crease line;
e) substantially reducing the thickness of the base material sheet along the crease line; and
f) detaching the workpiece from said base material sheet along said workpiece periphery.
2 . A method as claimed in claim 1 , wherein said at least one protrusion comprises a first protrusion and a second protrusion.
3 . A method as claimed in claim 2 , wherein said first protrusion is opposed to said second protrusion.
4 . A method as claimed in claim 3 , wherein said first protrusion is positioned within said first section and said second protrusion is positioned within said second section.
5 . A method as claimed in claim 4 , wherein said first protrusion and said second protrusion are each provided with an abutment face, said first and second protrusions being positioned such that said abutment faces are opposed one to the other.
6 . A method as claimed in claim 1 , further comprising the additional step of bending said first section back towards said first plane, such that said first section lies substantially coplanar with said second section.
7 . A method for forming pull tabs for containers from a base material sheet, said base material sheet having a thickness and defining a first plane, the pull tab having a protrusion and a crease line substantially adjacent thereto, the crease line dividing the stamped pull tab into a first section and a second section, the method comprising the steps of:
a) providing at least one protrusion in said base material sheet;
b) defining a tab periphery in said base material sheet, said tab periphery bounding an area of said base material sheet, said area having a first section and a second section;
c) substantially separating said tab periphery adjacent the first section from the remainder of said base material sheet;
d) bending the first section away from said first plane along a crease line; and
e) substantially reducing the thickness of the base material sheet along the crease line.
8 . A method as claimed in claim 7 , wherein said at least one protrusion comprises a first protrusion and a second protrusion.
9 . A method as claimed in claim 8 , wherein said first protrusion is opposed to said second protrusion.
10 . A method as claimed in claim 9 , wherein said first protrusion lies within said first section and said second protrusion lies within said second section.
11 . A method as claimed in claim 10 , wherein said first protrusion and said second protrusion are each provided with an abutment face, said first and second protrusions are positioned such that said abutment faces are opposed to one another.
12 . A method as claimed in claim 7 , further comprising the additional step of bending said first section back towards said first plane, such that said first section lies substantially coplanar with said second section.
13 . A method as claimed in claim 7 , wherein said first section is bent downwardly sufficiently to cause material deformation along said crease line.
14 . A method as claimed in claim 7 , wherein said base material sheet is an elongated strip.
15 . A method as claimed in claim 14 , wherein said steps (a) through (e) are performed concurrently in a progressive die for sequential pull-tabs.
16 . A method as claimed in claim 15 , wherein said strip has a width sufficient to accommodate the formation of at least two pull tabs positioned parallel to one another, and wherein each of said steps is performed concurrently for each of said at least two pull tabs positioned parallel to one another.
17 . A method as claimed in claim 7 , further comprising the step of detaching the pull tab from said base material sheet along said tab periphery.