Can manufacture

Abstract

A method and apparatus are disclosed which are suitable for use in the manufacture of two-piece metal containers. In particular, the method and apparatus disclose a way of making cups from metal sheet using a combination of stretching and (re-)drawing operations. The resulting cups have the advantage of reducing the thickness of the base of the cup relative to the ingoing gauge of material.

Claims

1. A method for manufacture of a metal cup, the method comprising the following steps: clamping an annular region on either or both of a sidewall and of a base of the cup to define an enclosed portion which includes all or part of the base, the base and sidewall of the cup being integral and formed of a metal sheet; deforming and stretching at least some of the enclosed portion to thereby increase the surface area and reduce the thickness of the base, the annular clamping restricting or preventing metal flow from the clamped region into the enclosed portion during this deforming and stretching step; and after the deforming and stretching step, drawing the cup to pull and transfer outwardly material of the stretched and thinned base into the sidewall.

2. A method as claimed in claim 1: wherein the annular clamping of the deforming and stretching step comprises using one or more clamping elements having a clamping face, the clamping face having a textured surface.

3. A method as claimed in claim 1, wherein the annular clamping is performed by clamping opposing surfaces of either or both the sidewall and the base of the cup between corresponding opposing first and second clamping elements, each of the first and second clamping elements having a clamping face with geometric discontinuities to thereby assist in disrupting the flow of the metal of the cup between the first and second clamping elements as the deforming and stretching step is performed.

4. A method as claimed in claim 3, wherein the geometric discontinuities comprise any one of: i. the clamping face of the first clamping element having one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features in the clamping face of the second clamping element; or ii. the clamping face of the second clamping element instead having one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features instead in the clamping face of the first clamping element; or iii. a combination of (i) and (ii).

5. A method as claimed in claim 4, wherein the first and second clamping elements are adapted such that, in use, the one or more beads, ridges or steps in the clamping face of the first or second clamping element urge metal of the clamped annular region so as to be wholly enclosed by and within the corresponding one or more relief features in the corresponding clamping face of the second or first clamping element.

6. A method as claimed in claim 1: wherein the deforming and stretching step comprises moving either or both of a stretch punch and the cup toward each other so that the stretch punch deforms and stretches the at least some of the enclosed portion.

7. A method as claimed in claim 6, wherein the stretch punch comprises an end face having one or more relief features.

8. A method as claimed in claim 6, wherein the stretch punch comprises a punch assembly, the assembly comprising a first group of one or more punches opposing one surface of the enclosed portion and a second group of one or more punches opposing the opposite surface of the enclosed portion, the deforming and stretching step comprising moving either or both of the first and second groups towards each other to deform and stretch the at least some of the enclosed portion.

9. A method as claimed in claim 1, further comprising an initial drawing step performed before the deforming and stretching step, the initial drawing step comprising drawing a metal sheet to form the cup.

10. A method as claimed in claim 1, wherein the drawing step comprises or is followed by a step of ironing the cup.

11. A method as claimed in claim 1 wherein the drawing step reduces a height of a dome formed during the deforming and stretching step by pulling and transferring material of the stretched and thinned base.

12. An apparatus for manufacture of a metal cup, the apparatus comprising: a clamping tooling adapted to clamp the cup formed of a metal sheet, the cup having a sidewall and an integral base, the clamping tooling adapted to clamp an annular region on either or both the sidewall and the base to define an enclosed portion which includes all or part of the base; a stretch tool adapted to deform and stretch at least some of the enclosed portion in a stretching operation to thereby increase the surface area and reduce the thickness of the base, the clamping tooling further adapted to restrict or prevent metal flow from the clamped region into the enclosed portion during this stretching operation; and tooling for drawing the cup, the drawing tooling adapted to pull and transfer outwardly material of the stretched and thinned base into the sidewall.

13. An apparatus as claimed in claim 12, wherein the clamping tooling is adapted to clamp an annular region on the base of the cup.

14. An apparatus as claimed in claim 12, wherein the clamping tooling comprises a clamping element having a clamping face, the clamping face having a textured surface.

15. An apparatus as claimed in claim 12, wherein the clamping tooling comprises a first clamping element and a second clamping element, the first and second clamping elements adapted to clamp opposing surfaces of either or both the sidewall and the base of the cup, each of the first and second clamping elements having a clamping face with geometric discontinuities to thereby assist in disrupting the flow of the metal of the cup between the first and second clamping elements as the stretching operation is performed.

16. An apparatus as claimed in claim 15, wherein the geometric discontinuities comprise any one of: i. the clamping face of the first clamping element having one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features in the clamping face of the second clamping element; or ii. the clamping face of the second clamping element instead having one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features instead in the clamping face of the first clamping element; or iii. a combination of (i) and (ii).

17. An apparatus as claimed in claim 16, wherein the first and second clamping elements are adapted such that, in use, the one or more beads, ridges or steps in the clamping face of the first or second clamping element urge metal of the clamped annular region so as to be wholly enclosed by and within the corresponding one or more relief features in the corresponding clamping face of the second or first clamping element.

18. An apparatus as claimed in claim 12, wherein the stretch tool comprises a stretch punch, the apparatus adapted to move either or both of the stretch punch and the cup toward each other so that, in use, the stretch punch deforms and stretches at least some of that part of the base which lies within the enclosed portion.

19. An apparatus as claimed in claim 18, wherein the stretch punch has an end face with a non-planar profile, the apparatus adapted to move either or both of the stretch punch and the cup toward each other so that, in use, the stretch punch deforms and stretches at least some of that part of the base which lies within the enclosed portion into a corresponding non-planar profile.

20. An apparatus as claimed in claim 18, wherein the stretch punch comprises an end face having one or more relief features.

21. An apparatus as claimed in claim 18, wherein the stretch punch comprises a punch assembly, the assembly comprising a first group of one or more punches opposing one surface of the enclosed portion and a second group of one or more punches opposing the opposite surface of the enclosed portion, the first and second groups moveable towards each other to, in use, deform and stretch at least some of that part of the base which lies within the enclosed portion.

22. An apparatus as claimed in claim 12, the apparatus further comprising tooling adapted to initially drawing a metal sheet to form the cup for the stretching operation.

23. An apparatus as claimed in claim 12, further comprising tooling for ironing the cup.

24. An apparatus as claimed in claim 12, wherein the drawing tooling is adapted to reduce a height of a dome formed by the stretch tool by pulling and transferring material of the stretched and thinned base.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

(1) FIG. 1 is a side elevation view of a container body of the background art resulting from a conventional DWI process. It shows the distribution of material in the base and sidewall regions of the container body.

(2) FIG. 2 is a graph showing in general terms how the net overall cost of manufacturing a typical two-piece metal container varies with the ingoing gauge of the sheet metal. The graph shows how reducing the thickness of the sidewall region (e.g. by ironing) has the effect of driving down the net overall cost.

(3) FIG. 3 is a graph corresponding to FIG. 2, but based on actual price data for UK-supplied tinplate.

(4) Embodiments of the invention are illustrated in the following drawings, with reference to the accompanying description:

(5) FIG. 4 is a graphical representation of the variation in base thickness of a cup resulting from use of a stretch punch (according to the invention) having a domed profiled end face.

(6) FIG. 5a is a side elevation view of the tooling of a cupping press used to form a first stage cup from a sheet metal blank. The figure shows the tooling before the initial drawing operation has commenced.

(7) FIG. 5b corresponds to FIG. 5a, but on completion of the initial drawing operation to form the first stage cup.

(8) FIG. 6a is a side elevation view of a stretch rig used to perform the stretching operation of the invention. The figure shows the stretch rig before the stretching operation has commenced.

(9) FIG. 6b shows the stretch rig of FIG. 6a, but on completion of the stretching operation.

(10) FIG. 7a shows a cross-section through a first embodiment of clamping means used to clamp the first stage cup during the stretching operation.

(11) FIG. 7b shows a cross-section through part of the base of the cup resulting from use of the clamping means shown in FIG. 7a.

(12) FIG. 8a shows a cross-section through a second embodiment of clamping means used to clamp the first stage cup during the stretching operation.

(13) FIG. 8b shows a cross-section through part of the base of the cup resulting from use of the clamping means shown in FIG. 8a.

(14) FIG. 9 shows an alternative embodiment to that of FIGS. 6a and 6b, in which the cup is clamped about its sidewall for the stretching operation.

(15) FIG. 10 shows an alternative embodiment of stretch punch to that shown in FIGS. 6a and 6b.

(16) FIG. 11 shows a further alternative embodiment of stretch punch to those shown in FIGS. 6a, 6b and 10, where the end face of the stretch punch includes various relief features.

(17) FIGS. 12a-d show perspective views of a bodymaker assembly used to re-draw the stretched cup. The figures show the operation of the bodymaker from start to finish of the (post-stretch) drawing operation.

(18) FIG. 13 shows a detail view of the re-draw die used in the bodymaker assembly of FIGS. 12a-d.

(19) FIG. 14 shows the sheet metal blank at various stages during the method of the invention as it progresses from a planar sheet to a finished cup.

(20) FIG. 15 shows the use of the cup of the invention as part of a two-piece container.

MODE(S) FOR CARRYING OUT THE INVENTION

Initial Drawing Operation

(21) A cupping press 10 has a draw pad 11 and a draw die 12 (see FIGS. 5a and 5b). A draw punch 13 is co-axial with the draw die 12, as indicated by common axis 14. A circumferential cutting element 15 surrounds the draw pad 11.

(22) In use, a flat section of metal sheet 20 is held in position between opposing surfaces of the draw pad 11 and the draw die 12. Steel tin-plate (Temper 4) with an ingoing gauge thickness (t.sub.in-going) of 0.280 mm has been used for the metal sheet 20. However, the invention is not limited to particular gauges or metals. The section of metal sheet 20 is typically cut from a roll of metal sheet (not shown). After the section of metal sheet 20 has been positioned, the circumferential cutting element 15 is moved downwards to cut a circular planar blank 21 out from the metal sheet (see FIG. 5a). The excess material is indicated by 22 on FIG. 5a.

(23) After the blank 21 has been cut from the sheet 20, the draw punch 13 is moved axially downwards through the draw die 12 to progressively draw the planar blank against the forming surface 16 of the draw die 12 into the profile of a cup 23 having a sidewall 24 and integral base 25. This initial drawing operation is shown in FIG. 5b, and includes a separate view of the drawn cup 23 when removed from the press 10. A detail view is included in FIG. 5a of the radius R.sub.12 at the junction between the end face of the draw die 12 and its forming surface 16. As for conventional drawing operations, the radius R.sub.12 and the load applied by the draw pad 11 to the periphery of the blank 21 are selected to permit the blank to slide radially inwards between the opposing surfaces of the draw pad 11 and draw die 12 and along forming surface 16 as the draw punch 13 moves progressively downwards to draw the blank into the cup 23. This ensures that the blank 21 is predominantly drawn, rather than stretched (thinned) (or worse, torn about the junction between the end face of the draw die and the forming surface 16 of the draw die). Dependent on the size of radius R.sub.12 and, to a lesser extent, the severity of the clamping load applied by the draw pad 11, the wall thickness of the cup 23 will be essentially unchanged from that of the ingoing gauge of the blank 21, i.e. negligible stretching or thinning should occur. However, in alternative embodiments of the invention, it is permissible for the load applied by the draw pad 11 to be sufficient that a combination of drawing and stretching occurs under the action of the draw punch 13. The cup 23 that results from this initial drawing operation is also referred to the first stage cup.

(24) Stretching Operation

(25) Following the initial drawing operation shown in FIGS. 5a and 5b, the drawn cup 23 is transferred to a stretch rig 30, an example of which is illustrated in FIGS. 6a and 6b. The stretch rig 30 has two platens 31, 32 that are moveable relative to each other along parallel axes 33 under the action of loads applied through cylinders 34 (see FIGS. 6a and 6b). The loads may be applied by any conventional means, e.g. pneumatically, hydraulically or through high-pressure nitrogen cylinders.

(26) On platen 31 is mounted a stretch punch 35 and a clamping element in the form of an annular clamp ring 36. The annular clamp ring 36 is located radially outward of the stretch punch 35. The stretch punch 35 is provided with a domed end face (see FIGS. 6a and 6b).

(27) On platen 32 is mounted a cup holder 37. The cup holder 37 is a tubular insert having an annular end face 38 and an outer diameter corresponding to the internal diameter of the drawn cup 23 (see FIGS. 6a and 6b). In use, the drawn cup 23 is mounted on the cup holder 37 so that the annular end face 38 contacts a corresponding annular region 26 on the cup's base 25 (see FIGS. 6a and 6b). Loads are applied via the cylinders 34 to move platens 31, 32 towards each other along the axes 33 until the annular region 26 is clamped firmly in an annular manner between the planar surface of the clamp ring 36 and the annular end face 38 of the cup holder 37. In this way, the clamp ring 36 and cup holder 37 each act as clamping elements, with the annular region 26 clamped in an annular manner between the planar surface of the clamp ring 36 and the annular end face 38 of the cup holder 37. The clamped annular region 26 defines an enclosed portion 27 of the cup. In the embodiment shown in FIGS. 6a and 6b, the annular clamping thereby separates the base 25 into two discrete regions: the clamped annular region 26 and the enclosed portion 27.

(28) The stretch punch 35 is then moved axially through the clamp ring 36 to progressively deform and stretch (thin) the metal of the enclosed portion 27 into a domed profile 28 (see FIG. 6b).

(29) In the embodiment shown in the drawings, the enclosed portion 27 is domed inwardly 28 into the cup (see FIG. 6b). This inward doming helps to minimise the volume envelope occupied by the cup and thereby assists subsequent handling operations of the cup. However, in an alternative embodiment, the enclosed portion 27 may instead be domed outwardly outside of the cup.

(30) Ideally, the clamping loads applied during this stretching operation are sufficient to ensure that little or no material from the clamped annular region 26 (or from outside of the clamped region, such as from the sidewall 24) flows into the enclosed portion 27 during stretching. This helps to maximise the amount of stretching and thinning that occurs in the domed region 28. However, as indicated above in the general description of the invention, it has been found that stretching and thinning of the enclosed portion 27 can still occur when permitting a limited amount of flow of material from the clamped annular region 26 (or from outside of the clamped region) into the enclosed portion.

(31) In summary, this stretching operation and the resulting thinning of the base 25 is critical to achieving manufacture of a cup or container body having a base thickness which is less than that of the ingoing gauge of the metal sheet.

(32) FIGS. 7a & 8a show detail views of two embodiments of the clamp ring 36 and cup holder 37 used to clamp the first stage cup during the stretching operation.

(33) FIG. 7a shows the face of the clamp ring 36 provided with an annular step 361 having a width w that opens out to the radial interior edge of the clamp ring. A corresponding annular cut-out 371 is provided in the face of the cup holder 37. In the embodiment shown, the step 361 and cut-out 371 have a height h of 1 mm and radii R.sub.361, 371 of 0.5 mm. The axially extending sides s.sub.361,371 of the step 361 and cut-out 371 are radially offset from each other by a distance greater than the thickness t of the metal sheet they are intended to clamp (see distance in FIG. 7a). This avoids the metal sheet being pinched or coined during clamping and thereby helps to minimise the formation of a weakened region that would be vulnerable to tearing during the subsequent drawing operation (or any subsequent ironing operation).

(34) FIG. 7b shows a partial view of the base of the corresponding cup that results from use of the clamping arrangement shown in FIG. 7a.

(35) FIG. 8a shows the face of the clamp ring 36 provided with an annular bead 361 located away from the radial interior and exterior edges of the clamp ring. A corresponding annular recess 371 is provided in the face of the cup holder 37. In this alternative embodiment, the bead 361 is capable of being wholly enclosed by and within the recess 371in contrast to the embodiment in FIG. 7a. Expressed another way, in use, the bead 361 of FIG. 8a urges metal of the clamped annular region 26 so as to be wholly enclosed by and within the recess 371. In this embodiment, the bead 361 has a height h of around 0.5 mm, with radii R.sub.361, 371 of around 0.3 mm and 0.75 mm respectively. As can be seen from FIG. 8a, in common with the embodiment in FIG. 7a, the bead 361 and recess 371 are profiled to avoid the metal sheet being pinched or coined during clamping.

(36) FIG. 8b shows a partial view of the base of the corresponding cup that results from use of the clamping arrangement shown in FIG. 8a.

(37) Both clamping embodiments have been used on 0.277 mm and 0.310 mm gauge metal sheet. However, this statement is not intended to limit the scope or applicability of the method or apparatus of the invention.

(38) Table 1 below shows for both clamping embodiments (FIGS. 7a and 8a) the axial clamping loads required during the stretching operation to achieve a given amount of stretching of the drawn cup 23. They clearly show that having the bead 361 adapted to be wholly enclosed by and within the recess 371 (as in the embodiment of FIG. 8a) drastically reduces the clamping loads required by almost 50% relative to the loads required when using the clamping arrangement of FIG. 7a. The reason for this difference in required axial clamping loads is that having the bead 361 capable of extending wholly within the corresponding recess 371 provides greater disruption to metal flow during the stretching operation and thereby provides an improved clamping effect. The disruption to metal flow is greater for the embodiment of FIG. 8a because the metal flow is disrupted by both axially extending sides s.sub.361 of the bead 361, whereas for the embodiment of FIG. 7a the metal flow is only disrupted by a single axially extending side s.sub.361 of its bead.

(39) TABLE-US-00001 TABLE 1 Clamping Embodiment Axial Clamping Force (kN) Slippage (mm) FIG. 7a 46-53 0.85-1.3 FIG. 8a 25-29 0.05

(40) In an alternative embodiment shown in FIG. 9, the sidewall 24 rather than the base 25 is clamped during the stretching operation. FIG. 9 shows an annular region 26 of the sidewall adjacent the base being clamped between cup holder 370 and clamping element 360. Either or both of the cup holder 370 and clamping element 360 may be segmented to facilitate the clamping of the sidewall, and to accommodate cups of different sizes. The annular clamping of the sidewall 24 defines an enclosed portion 27 inward of the clamped annular region 26 (see FIG. 9). A stretch punch 35 is also indicated in FIG. 9. Note that other features of the stretch rig are excluded from FIG. 9 for ease of understanding.

(41) In a further alternative embodiment, the single stretch punch 35 is replaced by a punch assembly 350 (as shown in FIG. 10). The punch assembly 350 has:

(42) i) a first group 351 of an annular punch element 351a surrounding a central core punch element 351b; and

(43) ii) a second group 352 of an annular punch element 352a.

(44) For ease of understanding, FIG. 10 only shows the punch assembly 350 and the drawn cup 23. Although not shown on FIG. 10, in use an annular region 26 of the cup's base 25 would be clamped during the stretching operation in a similar manner to the embodiment shown in FIGS. 6a and 6b.

(45) In use, the first and second groups of punch elements 351, 352 face opposing surfaces of the enclosed portion 27. The stretching operation is performed by moving both first and second groups of punch elements 351, 352 towards each other to deform and stretch (thin) the enclosed portion 27. The enclosed portion 27 is deformed into an undulating profile 280 (see FIG. 10).

(46) In a further embodiment, a single stretch punch 35 has a number of relief features in the form of recesses/cut-outs 353 provided in its end face (see FIG. 11). In the embodiment shown in FIG. 11, there is a central recess/cut-out surrounded by a single annular recess/cut-out. However, alternative configurations of recess/cut-out may be used.

(47) (Re-)Drawing Operation on Stretched Cup

(48) For the embodiment of the invention shown in FIGS. 6a and 6b, the stretched cup with its thinned and domed region 28 in the base is transferred to a bodymaker assembly 40 (see FIGS. 12a to 12d). The bodymaker assembly 40 comprises two halves 41, 42 (indicated by arrows in FIGS. 12a to 12d).

(49) The first half 41 of the bodymaker assembly 40 has a tubular re-draw punch 43 mounted on the same axis as circumferential clamp ring 44. As can be seen from FIGS. 12a to 12d, the clamp ring 44 circumferentially surrounds the re-draw punch 43 like a sleeve. As will be understood from the following description and looking at FIGS. 12a to 12d, the re-draw punch 43 is moveable through and independently of the circumferential clamp ring 44.

(50) The second half 42 of the bodymaker assembly 40 has a re-draw die 45. The re-draw die 45 has a tubular portion having an outer diameter corresponding to the internal diameter of the stretched cup 23 (see FIG. 12a). The re-draw die 45 has a forming surface 46 on its inner axial surface, which terminates in an annular end face 47 (see FIGS. 12a to 12d). The annular end face 47 of the re-draw die 45 corresponds in width to that of the annular region 26 on the base of the stretched cup.

(51) In use, the stretched cup 23 is first mounted on the re-draw die 45 (as shown on FIG. 12a). Then, as shown in FIG. 12b, the two halves 41, 42 of the bodymaker assembly 40 are moved axially relative to each other so that the annular region 26 of the base of the stretched cup is clamped between the annular end face 47 of the re-draw die 45 and the surface of the circumferential clamp ring 44.

(52) Once clamped, the re-draw punch 43 is then forced axially through the clamp ring 44 and the re-draw die 45 (see arrow A on FIGS. 12c and 12d) to progressively re-draw the material of the stretched cup along the forming surface 46 of the re-draw die. The use of the re-draw punch 43 and die 45 has two effects:

(53) i) to cause material from the sidewall 24 to be drawn radially inwards and then axially along the forming surface 46 of the re-draw die 45 (as indicated by arrows B on FIGS. 12c and 12d). In this way, the cup is reduced in diameter (as indicated by comparing FIG. 12a with FIG. 12d); and
ii) to cause the stretched and thinned material in the domed region 28 of the base to be progressively pulled out and transferred from the base into the reduced diameter sidewall (as indicated by arrows C on FIGS. 12c and 12d). This has the effect of flattening the domed region 28 of the base (see especially FIG. 12d).

(54) FIG. 12d shows the final state of the re-drawn cup 23 when the re-draw punch 43 has reached the end of its stroke. It can clearly be seen that the formerly domed region 28 of the base has been pulled essentially flat, to provide a cup or container body 23 where the thickness of the base 25 is thinner than that of the ingoing blank 21. As stated earlier, this reduced thickness in the base 25and the consequent weight reductionis enabled by the stretching operation performed previously.

(55) As shown in the detail view of the re-draw die 45 in FIG. 13, the junction between the forming surface 46 and the annular end face 47 of the re-draw die 45 is provided with a radius R.sub.45 in the range 1 to 3.2 mm. The provision of a radius R.sub.45 alleviates the otherwise sharp corner that would be present at the junction between the forming surface 46 and the annular end face 47, and thereby reduces the risk of the metal of the stretched cup 23 tearing when being re-drawn around this junction.

(56) The re-drawing stage illustrated in FIGS. 12a to 12d may also be followed by one or more further re-drawing stages to induce a further reduction in diameter of the cup 23.

(57) Note that although FIGS. 12a to 12d show use of a tubular re-draw punch 43 having an annular end face, the punch may alternatively have a closed end face. The closed end face may be profiled to press a corresponding profile into the base of the cup.

(58) The drawing operation described above and illustrated in FIGS. 12a to 12d is known as reverse re-drawing. This is because the re-draw punch 43 is directed to invert the profile of the stretched cup. In effect, the re-draw punch reverses the direction of the material and turns the stretched cup inside out. This can be seen by comparing the cup profiles of FIGS. 12a and 12d. Reverse re-drawing the cup in this context has the advantages of:

(59) i) preventing uncontrolled buckling of the domed region 28 of the base of the stretched cup (especially when using a re-draw punch having a closed end face); and

(60) ii) maximising transfer of material from the domed region 28 to the sidewalls 24.

(61) Note that although the embodiment shown in FIGS. 12a to 12d illustrates reverse re-drawing, conventional re-drawing would also work; i.e. where the re-draw punch acts in the opposite direction to reverse re-drawing and does not turn the cup inside out.

(62) FIG. 14 shows the changes undergone by the metal blank 21 from:

(63) a) before any forming operations have been undertaken, to

(64) b) forming into the first stage cup in the cupping press 10, to

(65) c) the stretching and thinning operation performed in the stretch rig 30, to

(66) d) the re-drawn cup that results from the bodymaker assembly 40.

(67) A location on the stretched and thinned domed region 28 of the stretched cup is indicated as X in view c of FIG. 14. The figure illustrates the effect of the re-drawing operation in radially pulling out the material at X (view c) to X (view d). The figure shows that the base of the cup at that location after stretching (t.sub.stretch) (and after the re-drawing operation) has a reduced thickness relative to the ingoing gauge of the blank 21 (t.sub.in-going), i.e. t.sub.stretch<t.sub.in-going. As previously stated, this thinning of the base is enabled by the stretching operation.

(68) To maximise the height of the sidewall 24 of the cup with its thinned base, the re-drawn cup may also undergo ironing of the sidewalls by being drawn through a succession of ironing dies (not shown) in an ironing operation. This ironing operation has the effect of increasing the height and decreasing the thickness of the sidewall, and thereby maximising the enclosed volume of the cup.

(69) FIG. 15 shows a container 100 where the final resulting cup 23 has undergone such an ironing operation to form container body 110. The container body 110 is flared outwardly 111 at its access opening. Can end 120 is provided with a seaming panel 121, the seaming panel enabling the can end to be fastened to the container body by seaming to the flared portion 111.