Aluminum cans occupies a large proportion of beverage packaging containers. The manufacture of cans combines advanced technologies in many industries such as metallurgy, chemical industry, machinery, electronics, and food, and has become a microcosm of aluminum deep processing. With the continuous intensification of competition in the beverage packaging market, for many can manufacturers, how to minimize the thickness of the sheet, reduce the weight of a single can, increase the utilization rate of materials, and reduce production costs in the production of cans are important goals pursued by enterprises . For this reason, technological transformation and technological innovation characterized by lightweight is quietly emerging. Lightweight cans involves many key technologies, of which the can body molding process and mold technology are very important aspects
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[ Manufacturing process and technology of can body ]
Stretching die for can body
The stretching process of a can body is actually the stretching process of a cylinder. During the stretching process, the flange part of the material is prone to destabilization under compressive stress, resulting in wrinkling. When the material passes through the die, the corners of the die are a transitional zone with complicated deformation. After the material has passed through the die corner, it is in tension. Since the tensile force from the pressure of the die is transferred through the corner, the material thins most at the corner of the die, making it the most susceptible to breakage.
A. Die material: Both convex and concave dies are made of carbide inserted material.
B. Deformation: In the can industry, the tensile ratio δ is generally used to indicate the amount of deformation.
The first tensile δ1 is 36.6% and the second tensile δ2 is 25.8%. The total tensile ratio δ≦64%, δ1≦40%, δ1≥δ2≧……≧ δn is generally required for two stretches.
C. Edging device: wave type edging ring, 0.2~0.3Mpa compressed air as power source.
D. Stretching Die Workpiece Parameters
Take 3.556mm for radius rA and 1.78mm for radius rA1.
Take 2.921mm for radius rB and 2.286mm for radius rB1 of the convex die.
Large gap (Z/2) between the convex and concave dies on one side of the stretching process reduces friction and can reduce the frictional force, but large gap makes it difficult to control precision.
A small gap (Z/2) on one side of the stretched convex and concave die will cause high friction and increase the tensile force.
The single-sided gap Z/2 can be calculated according to the following formula: Z/2=tmax k1
t-Nominal material thickness, take 0.285mm k-Factor, take 0.08 when t＜0.4mm
where tmax–maximum material thickness, take 0.285 0.005mm.
Thin Stretch Die
Can body forming is actually a combination of re-stretching and three thinning stretching processes, and the design of the thinning stretching die is briefly described below.
A. Mold Materials
Die: The base material is alloy tool steel, the die material is M2, the heat treatment hardness is 60-62 HRC, plated with TiN.
Concave Die: (thinning tension ring) base material is alloy tool steel, die opening material is carbide (brand VALENITECID-H.L.D or KE-84KENNAMETAL).
B. Volume of deformation.
Canmaking plants often prepare ring and die matching tables for technicians, mold maintenance personnel, and operators to select dies and rings based on given material thickness, can thickness, thin-wall requirements, ring and die sizes, tensile accuracy, and other conditions.
C. Working part parameters of the die.
Cam die: Cam die arc R 1.06±0.025mm,
Re-stretching of the cam arc R2.286mm, the arc of the outer wall of the bottom groove R10.478±0.013mm, the thinning stretching ring: concave die cone angle α=5°, the working strip width h=0.38 0.025mm.
Bottom Forming Mold
Alloy tool steel Cr12MoV is used as the material for the convex bottom die. The heat treatment hardness is 60-64 HRC, and the contour shape should be consistent with the can design. The bottom rim die is made of alloy tool steel Cr5MoV, with heat treatment hardness of 58-60 HRC, and its contour shape should match the convex die.
[ Experiences ]
Important factors to be considered in the drawing process are: tensile ratio, convex and concave die radius, convex and concave die gap, aluminum mechanical properties, lubrication, and operating parameters.
The size of the cone angle
The taper angle of the die in the thinning process depends on the flow properties of the metal in the deformation zone, the amount of stress, and the force applied to the die, which is a reasonable range.
Appropriate can design
Appropriate cans design is the key to the implementation of lightweight technology. Research shows that for CCB-1A tanks, the choice of design parameters: the angle between the outer wall of the bottom trench α1=32°, and the angle between the inner wall of the bottom trench α2=5 °, the convex mold arc R=1.016mm, the spherical surface and the inner wall arc of the tank bottom groove R1=1.524mm, the tank bottom spherical radius R=45.72mm, which can greatly increase the strength of the tank.
[ Can body making process ]
In the assembly line production process of the can body, you can roughly see the process:
Coil conveying → coil lubrication → blanking, stretching → tank forming → trimming → cleaning/drying → stacking/unloading → base color → drying → color printing → primer coating → drying → inner spraying → inner Drying → tank mouth lubrication → necking → spin compression neck
★The aluminum coil used to make cans weighs about 9 tons, is 1.5 meters wide, and makes 750,000 cans;
★The process of applying ink and varnish is 1,800 per minute;
★Aluminum can necking requires 11 steps, which is efficient industrial automation!
★Blanking, stretching, can body forming, trimming, reducing diameter, rotary compression diameter/flanging process requires mold processing, among which blanking, stretching and can body forming process and mold are the most critical, and its technological level and mold The level of design and manufacturing directly affects the quality and production cost of cans.
Process of making ring pull can lid
Pre-coated aluminum or steel sheets delivered to the can plant in coil or sheet form
Press out discs
Sheets are pressed through the press to produce thousands of discs per minute.
Fold Out Edge
Fold out the edge of the cover sheet in the same process
The lid is fed by a liner that precisely inserts a composite seal into the rim of each lid.
Check the lid
A video inspection system is used to check if the lid is perfect.
Punching and cutting of sheets
Pull rings are made from narrow aluminum or steel sheets. The sheet is first perforated and cut, and then further processed.
Pull Ring Forming, Loading on Can Lid
The lid is scored in a series of molds, the pull ring is further shaped, and the pull ring is loaded onto the lid.
Form a can lid with pull ring
Finally, a can lid with a pull ring (full opening lid for food cans and small opening lid for beverages) is formed
The lid is packed and shipped to the can filling plant
The finished can lids are packed in paper tubes, stacked and transported to the bottling plant, ready to be loaded on the filled can body
If you want to know more about the production process of cans, please click on the video below.
please click here to watch the production process of modern can beverages.