Abstract:
A method of manufacturing a die for shaping metal containers comprises providing an expansion die for manufacturing metal containers and peening at least a portion of the work surface of the expansion die. Another method of manufacturing a die for shaping metal containers comprises providing a die for narrowing a diameter of metal containers and peening at least a portion of the work surface of the die.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims priority to U.S. Provisional Patent Application No. 61/600,373, filed Feb. 17, 2012, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    In the container industry, substantially identically shaped metal beverage containers are produced massively and relatively economically. In order to expand a diameter of a container to create a shaped container or enlarge the diameter of the entire container, often several operations are required using several different expansion dies to expand each metal container a desired amount. Also, dies have been used to neck and shape the containers. Often several operations are required using several different necking dies to narrow each metal container a desired amount. 
       SUMMARY 
       [0003]    An expansion die for manufacturing metal containers comprises a work surface configured to expand a diameter of a metal container having a closed bottom. The work surface comprises a progressively expanding portion and a land. The outer diameter of the land is a maximum diameter of the die. 
         [0004]    In some embodiments, a portion of the work surface of the expansion die has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. In some embodiments, at least a portion of the land of the expansion die has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. In some embodiments, at least a section of the progressively expanding portion has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%45%. The maximum ratio of the closed void area is the closed void area/total area measured (times 100 for percentage). 
         [0005]    In some embodiments, a portion of the work surface of the expansion die, including a portion of the progressively expanding portion and/or the land, has a normalized closed void volume in the range of about one of 1-2000 mm3/m2, 9-1674 mm3/m2, 33-388 mm3/m2, 100-300 mm3/m2, 100-250 mm3/m2, 125-250 mm3/m2, 150-250 mm3/m2 and 155-231 mm3/m2. The normalized closed void volume is the closed void area times the depth of the area and quantifies the amount of lubricant that is able to be trapped in the valleys of the surface. 
         [0006]    A progressively expanding portion has dimensions and a geometry that when inserted into the open end of a container works the container&#39;s sidewall to radially expand the container&#39;s diameter in a progressive manner as the container travels along the work surface. 
         [0007]    With respect to expansion dies, a land is the portion of the working surface of an expansion die having the largest outer diameter that contacts a section of a container while the die is expanding the container. It is possible for a die to have multiple sections, each section having a land, each land having a different outer diameter. The land having the smaller outer diameter travels farther into the container than the land having the larger outer diameter. An example of a die having multiple lands can be seen in  FIG. 1 . 
         [0008]    In some embodiments, an initial portion of the work surface of the expansion die has geometry for forming a transition in a container from an original diameter portion to an expanded diameter portion. In some embodiments, the transition is stepped or gradual. 
         [0009]    In some embodiments the expansion die has an undercut portion, wherein the land is between the progressively expanding portion and the undercut portion. The land portion has dimensions and a geometry for setting the final diameter of the container being formed by that expansion die. In one embodiment, the length of the land of the expansion die may be 0.12″ or more. In other embodiments, the length of the land of the expansion die may be 0.010″, 0.020″, 0.04″, 0.05, 0.08 or 0.10 or more or less. In one embodiment, the length of the land of the expansion die is in the range between line contact of a continuous radius to 0.01″. In some embodiments of the expansion die, an undercut portion follows the land portion. In some embodiments of the expansion die, the transition from the land portion to the undercut portion is blended. 
         [0010]    In some embodiments, at least a portion of the undercut portion has surface roughness average (Ra) of about 8 μ in. to about 32 μ in. In some embodiments, the progressively expanding portion has a surface roughness average (Ra) of about 2 μ in. to about 6 μ in. In some embodiments, at least a portion of the land of the expansion die has surface roughness average (Ra) of about 8 μ in, to about 32 μ in. In some embodiments, at least a portion of the work surface of the expansion die, including at least a portion of the land, the progressively expanding portion and/or the undercut portion has a surface roughness average measured in 3 dimensions (Sa) in the range of about 1-50 μ in, 1-48 μ in, 7-43 μ in, 20-50 μ in, 20-45 μ in, 25-45 μ in, 30-45 μ in, 20-40 μ in, 30-40 μ in. 
         [0011]    An undercut portion comprises an undercut surface having an outer diameter. The outer diameter of the undercut surface is at least approximately 0.01 inches smaller than the outer diameter of the land portion and no less than a minimum diameter so as to reduce but not eliminate frictional contact between the undercut surface and the metal container. The outer diameter of the undercut surface is dimensioned to minimize collapse, fracture, wrinkle and all other physical defects, which may occur during expansion. In some embodiments, the diameter of the undercut surface is about 0.0075 to about 0.035 inches less than the outer diameter of the land portion. In other embodiments, the diameter of the undercut surface is about 0.01, 0.02 or 0.03 inches less than the outer diameter of the land portion. 
         [0012]    In some embodiments, the work surface of the expansion die is dimensioned so that when inserted into the metal container the entire land and at least a portion of the undercut portion enter the metal container and the land causes the diameter of at least a portion of the container to expand. 
         [0013]    In another embodiment, a die for narrowing a diameter of a metal container comprises a work surface configured to narrow a diameter of a metal container having a closed bottom. The work surface comprises: a neck radius portion, a shoulder radius portion and a land. The inner diameter of the land is a minimum diameter of the die. 
         [0014]    In some embodiments, at least a portion of the work surface of the die for narrowing a diameter of a metal container has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. In some embodiments of the die for narrowing a diameter of a metal container, at least a portion of the land has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. In some embodiments of the die for narrowing a diameter of a metal container, at least a section of the neck radius portion has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. In some embodiments of the die for narrowing a diameter of a metal container, at least a section of the shoulder radius portion has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. 
         [0015]    In some embodiments of the die for narrowing a diameter of a metal container, a portion of the work surface, including a portion of the neck radius portion, the shoulder radius portion and/or the land, has a normalized closed void volume in the range of about one of 1-2000 mm3/m2, 9-1674 mm3/m2, 33-388 mm3/m2, 100-300 mm3/m2, 100-250 mm3/m2, 125-250 mm3/m2, 150-250 mm3/m2 and 155-231 mm3/m2. 
         [0016]    With respect to a die for narrowing a diameter of a metal container, a land is the portion of the working surface of an expansion die having the smallest inner diameter that contacts a section of a container. It is possible for a die to have multiple sections, wherein each section has a land, each land having a different inner diameter. The land having the larger inner diameter travels further into the container than the land having the smaller inner diameter. 
         [0017]    In some embodiments, the length of the land of the die for narrowing a diameter of a metal container is between about 0.02″ to about 0.08″. In other embodiments, the length of the land of the die for narrowing a diameter of a metal container is about 0.03″ to about 0.07″. In yet other embodiments, the length of the land of the die for narrowing a diameter of a metal container is between about 0.04″ to about 0.06″. In one embodiment, the length of the land of the die for narrowing a diameter of a metal container is about 0.04″. In one embodiment, the length of the land of the die for narrowing a diameter of a metal container is in the range between line contact of a continuous radius to 0.01″. 
         [0018]    A neck radius portion is a portion of the necking die that forms a radius on the container immediately adjacent to a neck or the portion of the container having its diameter narrowed by a land of the die. 
         [0019]    A shoulder radius portion is a portion of a necking die that forms a radius on the container being narrowed adjacent to a neck radius. 
         [0020]    In some embodiments of the die for narrowing a diameter of a metal container, the die has a relief, wherein the land is between the neck radius portion and relief. In some embodiments of the die for narrowing a diameter of a metal container, the transition between the land and the relief is blended. In some embodiments, at least a portion of the relief has surface roughness average (Ra) of about 8 μ in. to about 32 μ in. In some embodiments, at least a section of the shoulder radius portion has a surface roughness average (Ra) of about 2 μ in. to about 6 μ in. In some embodiments, at least a section of the neck radius portion has a surface roughness average (Ra) of about 2 μ in, to about 6 μ in. In some embodiments, at least a portion of the land has surface roughness average (Ra) of about 8 μ in. to about 32 μ in. In some embodiments, at least a portion of the work surface, including at least a portion of the land, the shoulder radius portion, neck radius portion and/or the relief has a surface roughness average measured in 3 dimensions (Sa) in the range of about 1-50 μ in, 1-48 μ in, 7-43 μ in, 20-50 μ in, 20-45 μ in, 25-45 μ in, 30-45 μ in, 20-40 μ in, 30-40 μ in. 
         [0021]    The dimensions of the relief are provided to reduce frictional contact with the metal container and the necking die, once the metal container has been necked through the land and knockout. Therefore, in some embodiments, the relief in conjunction with the Ra of the necking surface contributes to the reduction of frictional contact between the necking die wall and the metal container being necked, wherein the reduced frictional contact maintains necking performance while reducing the incidence of collapse and improving stripping of the metal container. In one embodiment, the relief extends into the necking die wall by at least 0.005 inches measured from the base of the land. The relief may extend along the necking direction (along the y-axis) the entire length of the top portion of the metal container that enters the necking die to reduce the frictional engagement between the metal container and the necking die wall to reduce the incidence of collapse yet maintain necking performance. The relief comprises a relief surface, wherein an inner diameter of the relief surface is at least about 0.01 inches greater than the inner diameter of the land portion and an inner diameter of the relief surface is no greater than a maximum diameter so as to reduce but not eliminate frictional contact between the sidewall of the metal container and the relief surface while maintaining necking performance when necking the sidewall of the metal container. In some embodiments, the diameter of the relief surface is about 0.0075 to about 0.035 inches greater than the inner diameter of the land portion. In other embodiments, the diameter of the relief surface is about 0.01, 0.02 or 0.03 inches greater than the inner diameter of the land portion. 
         [0022]    In some embodiments, the work surface is dimensioned so that when inserted into the metal container the entire land and at least a portion of the relief travel relative to the container in an axial direction and at least a portion of the relief travels beyond a top of the container. 
         [0023]    In another embodiment, an expansion die for manufacturing metal containers comprises a work surface configured to expand a diameter of a metal container having a closed bottom. The work surface comprises a progressively expanding portion; and a land. An outer diameter of the land is a maximum diameter of the die. When the expansion die is expanding a metal container, at least a portion of the work surface has a surface having a ratio of area in contact with the metal container to area not in contact with the metal container in the range of about one of 25-99%, 30-71%, 41-71%, 40-55%, 40-52%, 35-55% and 30-60%. In some embodiments, the expansion die of this paragraph has the same characteristics of the expansion die(s) described above. 
         [0024]    In another embodiment a die for manufacturing metal containers comprises a work surface configured to narrow a diameter of a metal container having a closed bottom. The work surface comprises: a neck radius portion, a shoulder radius portion and a land. An inner diameter of the land is a minimum diameter of the die. When the die is narrowing the metal container, at least a portion of the work surface has a surface having a ratio of area in contact with the metal container to area not in contact with the metal container in the range of about one of 25-99%, 30-71%, 41-71%, 40-55%, 40-52%, 35-55% and 30-60%. 
         [0025]    In another embodiment, a method of manufacturing a die for shaping metal containers comprises: providing an expansion die for manufacturing metal containers comprising a work surface configured to expand a diameter of a metal container having a closed bottom; and peening at least a portion of the work surface. The work surface comprises a progressively expanding portion and a land. An outer diameter of the land is a maximum diameter of the die. 
         [0026]    In some embodiments, at least a portion of the land is peened. In some embodiments, at least a portion of the progressively expanding portion is peened. 
         [0027]    In some embodiments, the work surface is peened with precision balls having a diameter in the range of about one of 1/16th in- 3/32th in and 1/16th in- 5/32th in. 
         [0028]    In some embodiments, the peened portion of the work surface has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. 
         [0029]    In some embodiments, the peened portion of the work surface has a ratio of area in contact with the metal container to area not in contact with the metal container in the range of about one of 25-99%, 30-71%, 41-71%, 40-55%, 40-52%, 35-55% and 30-60%. In some embodiments the percent of area of the working surface that is peened is about one of 50-100%, 71-76%, 68-78%, 50-80%, 60-80% and 60-70%. In some embodiments, air pressure used to thrust the precision balls while peening the die surface is in the range of about one of 10-30 psi, 15-20 psi, 10-20 psi and 15-30 psi. 
         [0030]    In another embodiment, a method of manufacturing a die for shaping metal containers comprises: providing a die for manufacturing metal containers comprising a work surface configured to narrow a diameter of a metal container having a closed bottom; and peening at least a portion of the work surface. The work surface comprises: a neck radius portion, a shoulder radius portion and a land. An inner diameter of the land is a minimum diameter of the die. In some embodiments, at least a portion of the land is peened. In some embodiments, at least a portion of the shoulder radius portion is peened. In some embodiments, at least a portion of the neck radius portion is peened. In some embodiments, the work surface is peened with precision balls having a diameter in the range of about one of 1/16th in- 3/32th in and 1/16th in- 5/32th in. In some embodiments, the peened portion of the work surface has a surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15%. In some embodiments, the peened portion of the work surface has a ratio of area in contact with the metal container to area not in contact with the metal container in the range of about one of 25-99%, 30-71%, 41-71%, 40-55%, 40-52%, 35-55% and 30-60%. In some embodiments the percent of area of the working surface that is peened is about one of 50-100%, 71-76%, 68-78%, 50-80%, 60-80% and 60-70%. In some embodiments, the air pressure used to thrust the precision balls while peening the die surface is in the range of about one of 10-30 psi, 15-20 psi, 10-20 psi and 15-30 psi. 
         [0031]    All of the above embodiments are able to be used when narrowing or expanding a metal container without the use of lubricant. All of the above embodiments are suitable for use on any type of metal container including drawn and ironed aluminum containers having a closed, integral bottom, aka a two-piece container. In all of the embodiments above, the metal comprising the metal container may be any metal known in the art including, but not limited to, aluminum and steel. The metal container may or may not have a dome. In some embodiments, the metal container is a one-piece metal container having a closed bottom. In some embodiments, the metal container is comprised of multiple pieces of metal seamed together. 
         [0032]    A surface finish having a maximum ratio of the closed void area in the range of about one of 1%-30%, 4%-26%, 10%-26%, 10%-20%, 10%-15% and 12%-15% will be referred to as a “textured surface” herein. The open void volume and closed void volume are as characterized by WinSam (Surface Analysis Module for Windows) as described in (“Surface Characterisation in Forming Processes by Functional 3D Parameters,” S. Weidel, U. Engel, Int. J. Adv. Manuf. Technol. (2007) 33: 130-136), which is incorporated herein by reference. 
         [0033]    In one embodiment, the textured surface is created on the necking and expansion dies via peening with precision ball bearings to create a smooth, but dimpled, texture. Peening comprises thrusting precision balls with hardness greater than the die to create dimples in the tool surface. The design of the finished surface relies on the size and hardness of the balls, the velocity of the blast process, and the number of repeat hits against the die. For the purposes of this specification, a precision ball is a ball having a diameter that varies by no more than about 1%. 
         [0034]    A tool surface that is smooth, but not flat, is able to reduce friction without excessive debris generation or tool wear. The reduced friction is due to reduced area of contact between the die and the metal container. Contact area is as characterized by WinSam (Surface Analysis Module for Windows) as described in (“Surface Characterisation in Forming Processes by Functional 3D Parameters,”, S. Weidel, U. Engel, Int. J. Adv. Manuf. Technol. (2007) 33: 130-136), which is incorporated herein by reference. The reduced friction enables metal containers to be expanded or narrowed to a greater degree in a single stroke of an expansion die or a necking die without damaging the container. Damage includes wrinkling, fracturing, ludering, collapse of the metal container or anything that diminishes the appearance of the metal container. 
         [0035]    Some embodiments of this invention look at topography of the textured surface using 3-dimensional surface parameters and aim to minimize the area of contact of the tool with the work-piece. 
         [0036]    In some embodiments, use of a textured surface on an expansion or necking die may have any combination of the following advantages: maximizing the extent of metal forming in a single stroke of an expansion or necking die without damaging the container due to decrease in friction, thus reducing the number of metal forming steps and reducing the amount of scrap; reducing the starting weight required to meet final product dimension specifications; eliminating the need to use lubricant when forming the metal containers. In some embodiments, peening a die with precision balls results in a die that can form a metal container without defects more consistently than a highly polished die. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  depicts a cross-section of an expansion die having two lands; 
           [0038]      FIG. 2  is depicts a partial cross-section of the expansion die of  FIG. 1 ; 
           [0039]      FIG. 3  depicts a cross-section of a die for narrowing a diameter of a metal container; 
           [0040]      FIG. 4  illustrates the direction of metal flow; 
           [0041]      FIG. 5  shows the inside diameter of a portion of the working surface of the necking die after it has been peened as described above; 
           [0042]      FIG. 6  includes small field of vision images of the inside diameter of a portion of the working surface of the necking die shown in  FIG. 5 ; 
           [0043]      FIG. 7  shows the surface topography of a ground surface; 
           [0044]      FIG. 8  is a chart showing the average transverse Ra of the both the peened surface and the ground surface shown in  FIGS. 5-7 ; 
           [0045]      FIG. 9  shows the surface topography of the peened working surface of an expansion die; 
           [0046]      FIG. 10  shows the surface topography shown in  FIG. 9  with corresponding line profiles showing the depth and height of indentations; 
           [0047]      FIG. 11  shows the bearing area curve of the peened working surface shown in  FIGS. 9 and 10 ; 
           [0048]      FIG. 12  shows the amount of forming load an expansion die having a peened working surface placed on a metal container during expansion of the container; 
           [0049]      FIG. 13  shows forming energy of an expansion die having a peened working surface; 
           [0050]      FIG. 14  shows energy due to friction versus surface bearing area with respect to the non-peened surface; and 
           [0051]      FIG. 15  shows energy due to friction versus surface bearing area with respect to the peened surface. 
       
    
    
     DESCRIPTION 
       [0052]    An exemplary expansion die  10  is shown in  FIGS. 1 and 2 . A work surface  12  comprising a progressively expanding portion  14  and a land  16  is shown. An undercut  18  is also illustrated. 
         [0053]    An exemplary die  30  having a work surface  32  configured to narrow a diameter of a metal container is shown in  FIG. 3 . The work surface has a neck radius portion  34 , a shoulder radius portion  36  and a land  38 . A relief  40  is also shown. 
         [0054]    In one example, the work surface of a necking die was peened with 0.093″ diameter Class 1000 balls. The quality of the balls was sufficient to minimize dust generation or fracture of the balls. An analysis of the peened necking die follows.
       The inside diameter of the necking die was processed using a right angle lance   A replica of the inside diameter of the necking die was taken at one end   Topography and roughness data is from the replica   All topography images from replicas have been inverted to depict the true topography of the die surface   Definitions
           Sci is the Core Fluid retention index, Sci&gt;1 indicates good fluid retention.   Svi is the Valley Fluid retention index. 0&lt;Svi&lt;0.2 with high Sci indicates good fluid retention in the valley areas,   Vcl is the closed void volume indicating the void volume at the surface available to trap fluids   Vop is the open void volume indicating the void volume at the surface that allows fluid to escape   
           Instruments
           Topography—NanoFocus Surf I
               Using a 20× objective giving a field of view (FOV) of 0.8 mm×0.8 mm.   Large field of view (LFOV) topography 5.5 mm×2.15 mm   
               
               
 
         [0068]      FIG. 4  illustrates the direction of metal flow in relationship to the following topographic images. 
         [0069]      FIG. 5  shows the inside diameter of a portion of the working surface of the necking die after it has been peened as described above. 
         [0070]      FIG. 6  includes small field of vision images of the inside. diameter of a portion of the working surface of the necking die shown in  FIG. 5 . 
         [0071]    Surface characteristics of the working surface of the necking die after peening were as follows: Sa avg=18.8 μ in; Sci avg=1.63; Svi avg=0.11; Vcl avg=72.2 mm3/m2; Vop avg=1965 mm3/m2. 
         [0072]      FIG. 7  shows a ground, not peened surface. Surface characteristics of the surface shown in  FIG. 7  were as follows: Sa avg=20.5 μ in; Sci avg=1.24; Svi avg=0.16; Vcl avg=46.6 mm3/m2; Vop avg=2640 mm3/m2. 
         [0073]      FIG. 8  is a chart showing the average transverse Ra of the both the peened surface and the ground surface. 
         [0074]    Conclusions
       The peened surface had almost twice the closed void volume as a ground surface with similar Ra values   The fluid retention parameters Sci, and Svi both indicate the surface on the peened necking die has much better fluid retention than a ground surface   The closed void volume Vcl, and open void volume Vop parameters also shows the fluid retention to be good for the peened surface on the necking die   This indicates the peened surface would have much better tribological performance than a ground surface.       
 
         [0079]    In another example, an expansion die was peened with 0.1575″ (4 mm) Class 1000 balls. 
         [0080]      FIGS. 9 and 10  show the surface topography of a portion of the working surface after peening.  FIG. 11  shows the bearing area curve of the peened portion of the working surface. 
         [0081]    In another example, the working surfaces of several expansion dies were modified by peening and the resulting effects on friction were compared to a baseline friction from a die surface that has been hard turned and lightly polished. The hard turned and lightly polished surface is not textured but has an Ra value of 8 to 10□in. All other factors were held constant (Pre-Form, Tool Geometry, no air stripping used, no lubrication used). 10 samples were taken for each surface combination. A “B Ball” is a precision ball having 1/16th inch diameter. A “C Ball” is a precision ball having a 3/32 inch diameter. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Pre-Form 
                 Tool 
               
               
                 Working Surface 
                 Lubricant 
                 (Constant) 
                 (Constant) 
               
               
                   
               
             
             
               
                 Hard turned and 
                 No 
                 53 mm Diameter 
                 Multi Tier Final 
               
               
                 lightly polished 
                 Lubricant 
                 (7.2820 inch 
                 Expansion Die 
               
               
                 (HT&amp;P) 
                   
                 height) 
                 (no air stripping) 
               
               
                  1/16 th  Precision Ball 
                   
                 Factory Coated 
                   
               
               
                 Peen on top of Hard 
                   
                 and Inside 
                   
               
               
                 turned and lightly 
                   
                 Sprayed 
                   
               
               
                 polished (HT&amp;P 
                   
                   
                   
               
               
                 to ‘B’) 
                   
                   
                   
               
               
                 C’ Ball re-peened on 
                   
                   
                   
               
               
                 top of ‘B’ Ball Peened 
                   
                   
                   
               
               
                 tool as described (‘B’ 
                   
                   
                   
               
               
                 Ball to ‘C’ Ball) 
                   
                   
                   
               
               
                  3/32 nds  Precision Ball 
                   
                   
                   
               
               
                 Peen on top of Hard 
                   
                   
                   
               
               
                 turned and lightly 
                   
                   
                   
               
               
                 polished (HT&amp;P 
                   
                   
                   
               
               
                 to ‘C’) 
               
               
                   
               
             
          
         
       
     
         [0082]    Changes in friction due to tool surface were evident from changes in Forming Energy. Forming Energy totals were calculated from Load vs. Displacement data using a numerical integration technique. 
         [0083]    Tool surfaces were characterized by Sa (3-D parameter for Surface Roughness), Vcl (Normalized Closed Void Volume), αclm (Maximum Ratio of the Closed Void Area(/total area measured)) and percent contact area for each surface finish. 
         [0084]    Strain Energy was calculated using Finite Element Analysis using the given Tool and Pre-Form Sample Geometry to provide Forming Energy in a frictionless state. Friction data was then tabulated by subtracting the Strain Energy from the Forming Energy totals to arrive at Energy figures due to Friction. 
         [0085]    Results are provided with a Percent Change in Friction Energy for each surface characterized in percent contact area. 
         [0086]      FIG. 12  shows the amount of forming load the expansion die placed on the metal container.  FIG. 13  shows forming energy.  FIG. 14  shows energy due to friction versus surface bearing area with respect to the non-peened surface.  FIG. 15  shows energy due to friction versus surface bearing area with respect to the peened surface. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                 Forming Energy Comparison 
               
               
                 No Lubrication/2.625 inches of Travel 
               
             
          
           
               
                   
                   
                   
                   
                   
                 Connect- 
               
               
                   
                   
                 Number 
                 Mean 
                 Std Dev 
                 ing 
               
               
                   
                 Tool Surface Level 
                 of Runs 
                 (inlbs) 
                 (inlbs) 
                 Letters 
               
               
                   
               
             
          
           
               
                 
                           
                 
                 HT&amp;P 
                 10 
                 1139 
                 17.1 
                 A 
               
               
                 
                           
                 
                 HT&amp;P to ‘B’ Ball 
                 10 
                 1062 
                 20.1 
                 B 
               
               
                 
                           
                 
                 HT&amp;P to ‘C’ Ball 
                 10 
                 945 
                 14.8* 
                 C 
               
               
                 
                           
                 
                 ‘B’ Ball to ‘C’ Ball 
                 10 
                 978 
                 16.5 
                 C 
               
               
                   
               
               
                 *Standard deviation calculation excludes open circled outlier from Forming Energy data. 
               
               
                 Adding the ‘C’ ball finish on top of an original hard turned and lightly polished tool surface was shown to reduce Forming Energy by 15 to 19 percent with no use of lubricant. 
               
               
                 Using a smaller diameter ball (‘B’ Ball) was shown to reduce Forming Energy by 4 to 10 percent with no use of lubricant. 
               
               
                 Re-peening the ‘B’ Ball surface created above with the ‘C’ Ball did not produce a statistically significant change in Forming Energy. 
               
             
          
         
       
     
         [0087]    For the purposes of this specification, terms such as top, bottom, below, above, under, over, etc. are relative to the position of a finished metal container resting on a flat surface, regardless of the orientation of the metal container during manufacturing or forming steps or processes. A finished metal container is a metal container that will not undergo additional forming steps before it is used by an end consumer. In some embodiments, the top of the container has an opening. 
         [0088]    Although the present invention has been described in considerable detail with reference to certain versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the versions contained herein. 
         [0089]    All features disclosed in the specification, including the claims, abstracts, and drawings, and all the steps in any method or process disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in the specification, including the claims, abstract, and drawings, can be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0090]    Any element in a claim that does not explicitly state “means” for performing a specified function or “step” for performing a specified function should not be interpreted as a “means or step for” clause as specified in 35 U.S.C. §112.