FUNDAMENTALS OF
`PACKAGING TECHNOLOGY
`Second Edition
`
`Walter Soroka
`
`~ ~p Institute of.
`~V Packaging
`Professionals
`Herndon, Virginia
`
`RJRV EX 1021
`
`

`

`·• :::JeiT!'f r:r · I r
`
`Publisher: Richard Warrington
`
`Text and Cover Designer: Gary Head
`
`Copyeditor: Beverly J. DeWitt
`
`Proofreader: Esther Riley
`
`Indexer: Trisha Lamb-Feuerstein
`
`Typesetter: Joan Olson
`
`Printer: TechniGraphix
`
`Copytight © 1995, 1999 by the Institute of Packaging Professionals. All rights reserved.
`No part of this publication may be reproduced in any form or by any means, electronic or
`mechanical, including photocopying. without permission in writing from the publisher.
`Statements of fact or opinion are made on the responsibility of the author alone and do not
`imply an opinion or endorsement on the part of IoPP, its officers, or its membership.
`Address all inquiries to the Institute of Packaging Professionals, 481 Carlisle D1ive,
`Herndon, Virginia 22070, U.S.A.: (703) 318-8970.
`
`Printed in the United States of Ameiica on recycled paper
`
`RJRV EX 1021
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`

`

`CHAPTER SEVEN
`
`METAL CANS AND CONTAINERS
`
`CONTENTS
`
`Background
`Early metal packaging, three-piece and two-piece con(cid:173)
`structions, advantages of two-piece and three-piece cans,
`common metal can shapes and applications.
`
`Can-Making Steels
`Black-plate steel, tin-plating, differential tin-plating, tin(cid:173)
`free steel, steel -alloys, temper,,RockweU hardness. base
`box measure, base box conversion factors, typical tin(cid:173)
`plating weights, typical steel application weights and
`thickness.
`
`Three-Piece Steel Cans
`Mechanica1 seaming applications, adhesive bonding
`applications, soldered seams, welded cans. welded-Cllll
`manufacture. sidewall beading, can-end expansion rings,
`compound, double seaming.
`
`Two-Piece Drawn Cans
`Manufacturing methods, shallow draw, predecorated shal(cid:173)
`low draw, draw limits, draw and redraw cans, the draw,
`and-iron process, expanded-wall cans.
`
`Impact Extrusion
`Materials, manufacturing sequence, collapsible tubes,
`dimensioning collapsible tubes, tip styles, advaotages and
`applications. coatiug and decorating, impact-extruded
`aerosol cans.
`
`Can Dimensioning
`Standard can dimensioning practice.
`
`Protective Coatings for Cans
`Purpose, resin types.
`
`Decoration
`Can lithography versus paper labeling, plastic sleeves,
`can lithography for flat sheers. offset letterpress for round
`shapes, decorating limitations.
`
`Industrial Metal Containers
`Standard industrial containers, regulated couta-iners, opeu(cid:173)
`ltead pails and drums, closed-head pails and drums, typi(cid:173)
`cal steeJ gauges, cover options.
`
`Aerosols
`Definition, product categories, history. propellants 1 pro(cid:173)
`pellant pressures, product formulations, actuators, mount(cid:173)
`ing cups, valve operation, valve options, other pressurized
`dispensing systems, regulation, aerosol container specifi(cid:173)
`cations.
`
`Resources
`Associations related to metal cans and containers.
`
`145
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`RJRV EX 1021
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`CHAPTER SEVEN
`METAL CANS AND CONTAINERS
`
`BACKGROUND
`
`Steel is one of the older packaging materials and was originally used for round,
`square, and rectangular boxes and canisters. Tea and tobacco were two of the first
`products packaged in tin-plated, mechanically seamed or soldered steel containers
`with friction or hinged lids. Today such labor-intensive metal boxes are limited to
`custom and upscale applications. The old-fashioned appearance of a fabricated
`metal box is effectively used by package designers to create nostalgia for specialty
`and gift-type containers.
`Of all the metal packaging forms, none has had as much impact on society as
`the sanitary food can. Thermal processing of food packed into hand-soldered
`cylindrical metal cans started in the early 1800s, and soon developed into a major
`industry. Metal cans have the advantage of being relatively inexpensive, thennally
`stable, rigid, easy to process. on high-speed lines, and readily recyclable. Metal
`offers a total barrier to gas and light. Despite market changes brought on by freez(cid:173)
`ing and plastic-based packaging, metal cans remain an important means of deliv(cid:173)
`ering a shelf-stable product.
`Originally, all steel containers were fabricated from flat sheets that were cut to
`size, bent to shape, and mechanically clinched or soldered to hold the final shape.
`Food cans were three-piece constmction, a formed sidewall and a top and bottom
`end. (See Figure 7.1.)
`
`~---Canner's end
`component
`-
`~!'I!"""""'~
`
`Canner's
`end seam
`
`-Body
`
`Sidewall
`beading
`
`-Side seam
`
`Maker's
`end seam
`
`• Maker's end
`component
`
`Figure 7.1
`Three-piece and two-piece can construction.
`
`Canner's end
`component
`
`--• Canner's
`end seam
`
`One-piece
`body
`
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`148 Chapter Seven
`
`With time, ways of drawing metal (shaping metal by pushing it through a die)
`were developed. Shallow drawn containers with friction or slip covers were used
`for pastes, salves, greases, and other semisolid products. Later, two-piece shallow
`drawn cans with double-seamed (folded) ends were used for sardines.
`Two-piece cans have a body and bottom in a single piece with a separate
`attached end. (See Figure 7.1.) Immediate advantages are reduced metal use,
`improved appearance, and the elimination of a possible leakage location.
`However, while three-piece cans can easily he changed in length and diameter,
`two-piece cans require more elaborate tooling that is dedicated to one can form.
`Improvements in metallurgy and processing allowed deeper draws and multi(cid:173)
`ple draws and eventually led to a draw-and-iron process in which the walls of a
`drawn container were made thinner by an ironing step. Aluminum joined steel as
`a can material.
`Ductile metals, such as tin, lead, and aluminum, can be formed into tubular
`shapes by impact extrusion. Originally, only tin and lead were used to make col(cid:173)
`lapsible tubes. (A mbe that can be squeezed, or collapsed, to expel the contents.)
`Today, impact-extruded collapsible tubes are made from aluminum, except for a
`small number of special applications requiring the chemical properties of tin or lead.
`Impact-extrusion technology has advanced lo the point where heavier gauge
`aluminum extrusions can be used for pressurized aerosol containers.
`
`Common Metal Container Shapes
`
`Stock metal eans come in a great variety of sizes and shapes. A quick list of the
`most common would contain the following:
`
`• Three-piece steel sanitary food cans.
`• Aerosol cans, made by three methods:
`Three-piece steel cans (a welded body and two ends).
`'Iwo-piece cans (an impact-extruded aluminum body and an end).
`One-piece cans (an impact-extruded aluminum body, necked-in to accept
`the valve cup).
`
`• Steel or aluminum two-piece drawn-and-ironed beverage cans.
`• Two-piece steel or aluminum cans made by drawing or by draw and redraw.
`Full-opening, ring pull-top eans are used for Vienna sausage, potted meats,
`and dips. Double-seamed conventional-top cans ean be used for most
`canned food products.
`
`•
`
`• C'..ans with hinged lids, usually steel, \!Sed for medications, confections,
`small parts, and novelties.
`• Flat round cans of drawn steel or aluminum, with slipcovers. Used for oint(cid:173)
`ments, salves, confections, shoe polish, and novelties. (See Figure 7.2.)
`'Three-piece steel or aluminum ovals, typically fitted with a dispensing
`spout and used for oils. (See Figure 7.2.)
`• Traditional pear-shaped three-piece stee,L ham cans.
`• Oblong steel three-piece F-style cans used mostly to contain aggressive sol(cid:173)
`vents. (See Figure 7.2.) The "F' name comes from Flit insecticide, an early,
`large-volume user. 'There are no Ac, B-, C-, D-, or E-style cans.
`
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`""'I'
`
`• '
`•
`l • j
`t
`• l
`
`•
`•
`
`•
`•
`•
`
`l •
`
`~
`J
`I •
`
`Metal Cans and Containers 149
`
`Figure 7. 2
`An_ F-style (oblong) can, square-breasted talc and spice cans, an oval can, and a flat
`round with li slipcover.
`
`• Oblong key-opening cans, three-piece steel, used for luncheon meat
`products.
`• Multiple friction cans of three-piece steel, used primarily by the paint
`industry. Also referred to as double- and triple-tight cans ( doubletite and
`tripletite ) .
`• Three-piece square-breasted steel cans. (See Figure 7 .2.) Larger designs are
`specific to the talcum, bath, and baby powder markets. Spice cans are
`smaller three-piece cans with a perforated metal or plastic top, used for
`spices and dry condiments .
`• Industrial pails and drums. The most common are 20-litre pails (5-gal U.S.)
`and 210-litre drums (55-gal U.S.). (See Figure 7.17.)
`• Two-piece, low-profile steel or aluminum ovals, with full-opening ring
`pull-tops for seafood products.
`• Impact extrusions, which are used for one-piece aluminum aerosol cans and
`collapsible metal tubes.
`
`CAN-MAKING STEELS
`
`The name "tin can" is not strictly correct, since low-carbon steel is the predomi(cid:173)
`nant can-making material. Bare steel corrodes readily when in contact with mois(cid:173)
`ture or other corrosive agents, and unprotected steel, or black plate, can be used
`only for such noncorrosive products as waxes, oils, or greases. Normally a coat(cid:173)
`ing is needed to protect the steel. This was first done by dipping black plate sheets
`into baths of molten tin. The original full term was probably "tinned canister."
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`150 Chapter Seven
`
`l !
`
`Table 7.1
`Embossing identif,cations tor tinplate,
`
`Heavy-Side Coating
`5,6 g1m2
`(No. 50)
`8.4 gim2
`(No. 75)
`11.2 glm2
`(No. 100)
`15.2 glm2
`(No. 135)
`
`All others
`
`Heavy-Side Marking
`
`Light-Side Marking
`
`Lines 12.7 mm apart
`(112 in. apart)
`
`25.4 mm squares
`(1 in. squares)
`
`Lines 25.4 mm apart
`(1 in. apart)
`
`25.4 mm circles
`(1 in. circles)
`
`Lines 38 mm apart
`(1-1/2 in. apart)
`
`Lines 50.8 mm apart
`(2 in. apart)
`
`Lines 76.2 mm apart
`(3 in. apart)
`
`25.4 mm x 38 mm diamonds
`(1 in. x 1-114 in. diamonds)
`
`25.4 mm hexagons
`(1 in. hexagons)
`
`Sine waves 76.2 mm apart
`(sine waves 3 in. apart)
`
`Today, black plate is electrolytically tin plated, allowing substantial reductions
`in the amount of tin used, as well as offering the ability to put different thicknesses
`of tin on either side of a steel sheet. The tin layer is extraordinarily thin, on the
`order of 0.38 micrometre (0.000 015 in.).
`Manufacturers identify differential tinplate as to both the amount of tin plat(cid:173)
`ing and the side having the thicker plate by embossing a light pattern onto one side
`of the sheet. (See Table 7.1.) The heavier tin deposit goes to the inside of the con(cid:173)
`tainer, where greater protection is needed.
`Tin-free steels (TFS), or electrolytic chrome-coated steel (ECCS), use chrome
`and chrome oxides for corrosion protection. 1FS is more economical than tinplate.
`However, it is necessary to remove the chrome to weld the can body, and the chrome
`coating is somewhat more abrasive. 1FS are often used for can ends or for drawing,
`where weldability is not a consideration.
`Alloy and temper are the most important variables when selecting a can
`maker's quality (CMQ) steel. Alloy type MR ("medium residual," referring to the
`amount of residual metal elements other than phosphorus) is the most common
`can-making steel. Alloy types Land I.:f have low residuals and are used for acidic
`foods and other corrosive products. Type D alloy has aluminum added to improve
`ductility and is used in applications where deep draw is required.
`Temper and hardness are affected by the method of rolling and annealing.
`Steels range from "dead" (easily folded over) to stiff and springy. Metal is work(cid:173)
`hardened if rolled while cold, thus producing a much stiffer steel. Double-reduced
`steel is rolled once, annealed, and then cold-rolled again. These 2CR or DR steels
`are used whenever maximum stiffness is required.
`Steel temper and hardness are related values. Stiffer steels are harder to work
`and do not draw well. Steel temper must be carefully matched to the application, and
`a compromise must be found between stiffness and workability. Metal temper is des(cid:173)
`ignated by an arbitrary number, using a-,Rockwell 30. T hardness tester. The
`Rockwell gauge measures the penetration of a hardened steel ball into the sheet sur(cid:173)
`face al a given force. (See Table 7.2.)
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`Metal Cans and Containers 151
`
`Table7.2
`Typical Rockwell hardness and applications for various tempers.
`
`Temper
`
`Rockwell
`Hardness
`
`" ~
`
`Application
`
`T1
`
`T2
`
`TS
`
`T4
`
`T5
`
`DR-8
`
`DR-9
`
`46-52
`
`50-56
`
`5-3
`
`58-64
`
`62-68
`70-73
`
`76-77
`
`Soft and ductile steel for deep draws
`
`Moderate-draw steel: shallow cans, closures
`
`Shallow-draw steel: general purpose, 8nds, crowns,
`closures
`
`General purpose, bodies and ends
`
`Can ends and bodies
`
`Maximum-stiffness ends and bodies
`
`Maximum-stiffness ends and bodies
`
`Table 7.3
`Base-box CQnversk>n factors,
`
`1 base box
`
`Base box x 4.9426
`
`= 31,360 square inches= 20.2 square metres
`
`= 100 square metres (SITA)
`
`Basis weight x 0,00011
`
`= Nominal decimal inches ot thickness
`
`1 pound per base-box plating weight
`
`= 22.42 grams per square metre
`
`Historically, tin-mill products were specified by the base box: the weight in
`pounds of 112 sheets measuring 14 by 20 inches. Plating weights are given as the
`weight added per base box, For differential tinplate, tbe values for each side are
`given, Metric practice quotes metal grammage: the mass per square metre. System
`International Tinplate Association (SITA) quotes tinplate in kilograms per 100
`square metres. Table 7.3 gives conversions for these different standards. Table 7.4
`shows designations for different plating weights. Table 7.5 lists the thickness of
`steel at various base weights and grammage,
`
`THREE-PIECE STEEL CANS
`
`Steel three-piece can bodies can be mechanically seamed, bonded with adhesive,
`welded, or soldered. (See Figure 7.3.) Aluminum cannot be soldered and cannot
`be welded economically. Welded sanitary three-piece can bodies are therefore
`made exclusively of steel. Mechanical seaming or clinching is used only for con(cid:173)
`tainers intended for dry product, where a hem1etic seal is not important.
`Adhesive bonding, or cementing, uses a thermoplastic (or other) adhesive
`extruded onto a hot can blank, The blank is shaped into a cylinder on a body for(cid:173)
`mer. The thennoplastic adhesive is heated, and the seam is "bumped" and quickly
`chilled to set the bond.
`Adhesive bonding is an attractive body-assembly method for those applica(cid:173)
`tions where tbe can will not be subjected to thermal processing. Unlike welded
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`152 Chapter Seven
`
`Table 7.4
`Typical coating weights of electrolytic tinplate.
`
`Designation
`
`Pounds per Base Box•
`
`Grams per Square Metre•
`
`10
`
`20
`
`25
`
`35
`
`50
`
`75
`
`100
`
`50/25
`
`75/25
`
`100/25
`
`100/50
`
`135/25
`
`0.05 I 0.05
`
`0.10/0.10
`
`0.125 / 0.125
`
`0.175 / 0.175
`
`0.25/0.25
`
`0.375 I 0.375
`
`0.50/0.50
`
`0.25 I 0.125
`
`0.375 I 0.125
`
`0.50 I 0.125
`
`0.50 I 0.25
`
`0.675 I 0.125
`
`1.12/1.12
`
`2.24/ 2.24
`
`2.8 I 2.8
`
`3.92 / 3.92
`
`5.6 I 5.6
`
`8.4 I 8.4
`
`11.2/11.2
`
`5.6 I 2.8
`
`8.4 I 2.8
`
`11.2 / 2.8
`
`11.2 / 5.6
`
`15.1 / 2.8
`
`*Weights are given for both sides.
`
`Table 7.5
`Steel weights and theoretical thicknesses.
`
`Base-Box Measure
`Nominal
`Thickness (inches)
`
`Base
`Weight
`
`50
`
`55
`
`60
`
`0.0055
`
`0.0061
`
`0.0066
`
`Metric Measure
`
`Grammage
`
`Thickness (mm)
`
`1,121
`
`1,233
`
`1,345
`
`0.140
`
`0.155
`
`65
`
`70
`
`75
`
`80
`
`85
`
`90
`
`95
`
`100
`
`103
`
`107
`
`112
`
`118
`
`128
`
`135
`
`0.0072
`
`0.0077
`
`0.0083
`
`0.0088
`
`0.0094
`
`0.0099
`
`0.0105
`
`0.0110
`
`0.0113
`
`0.0118
`
`0.0123
`
`0.0130
`
`0.0140
`
`0.0149
`
`1,457
`
`1,569
`
`1,681
`
`1,794
`
`1,906
`
`2,018
`
`2,130
`
`2,242
`
`2,309
`
`2,399
`
`2,511
`
`2,645
`
`2,870
`
`3,027
`
`~
`
`"
`
`0.0168
`-
`0.183
`
`0.196
`
`0.211
`
`0.224
`
`0.239
`
`0.251
`
`0.267
`
`0.279
`
`0.287
`
`0.300
`
`0.312
`
`0.330
`
`0.358
`
`0.378
`
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`Metal Cans and Containers 153
`
`- Mechanical clinch seam
`
`Welded seam
`
`Figure 7.3
`Mechanical, welded, and adhesive-bonded side seams for three-piece cans.
`
`Adhesive-bonded (cemented) seam
`
`cans, adhesive-bonded constructions can have full wraparound lithography. At one
`time three-piece beverage containers were adhesive bonded. Some frozen juice
`concentrate and paint cans are adhesive bonded.
`To solder a can. engaging hooks are bent into the can blank similar to the
`approach for a mechanical seam, the body is formed, and the engaging hooks are
`flattened to hold the cylindrical shape. The seam is treated with a flux and is passed
`over a roll -rotating in a bath of molten solder. Solders are typically composed of
`97 .5% lead and 2.5% tin. Lead extraction by food products was always a potential
`problem with soldered seams, and the industry quickly adopted welding technol(cid:173)
`ogy when it became available. Soldered cans are no longer permitted for food in
`North Americ!'I. Some soldering is still done for industrial and nonfood applica(cid:173)
`tions. The lead content of many of the solders used has been reduced or eliminated.
`Welded cans are strong and eliminate potential lead hazards. Mo~t three-piece
`steel food cans are welded by a process initiated in Europe by Soudronic. The body
`sheet is formed into a tube with a slight overlap along the joint. In the most common
`process, the joint is passed between two continuous copper wire electrodes, and
`electrical current passing through the joint heats and fuses the metal. (See Figure
`7.4.) Lithographed can blanks require about 6 millimetres (0.25 in.) of undecorated
`strip along the weld edges to ensure good electrical contact for welding. The welded
`seam line is about 30% thicker than the two base metal sheets. Cans shorter than 75
`
`Wire spool
`
`Figure 7.4
`The can-welding process.
`
`Wire
`reclaim
`
`j
`
`H---Electrode
`Welded metal -- ➔~--
`
`Electrode
`
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`--
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`154 Chapter Seven
`
`~ - - - - - - - - Seaming panel
`Chuck panel
`Bead
`___ First expansion panel - - -~
`Second expansion --i
`panel
`l'
`
`Center panel
`
`Figure 7.5
`Typical can-end embossing pattem
`
`millimetres (3 in.) are too short to be welded individually and are made by welding
`a body twice the required length and then cutting it into two cans.
`All three-piece can bodies are pressure tested and have the ends flanged to
`receive the can top and bottom ends. The can maker applies one can end and sends
`the other end to the user for double seaming after the can is filled.
`Sanitary food cans that may be thermally processed have bead patterns
`embossed into the can sidewalls to improve resistance to collapse because of
`external pressure. (Refer back to Figure 7.1.) This prevents collapse (paneling)
`during pressure differentials encountered during retorting and enables the can to
`withstand an internal vacuum. Sidewall beading requires more material, reduces
`top-to-bottom compression strength, and complicates labeling. There are many
`sidewall bead geometries designed to maximize hoop strength while minimizing
`the accompanying problems.
`Can ends intended for thermal processing are stamped with a series of circu(cid:173)
`lar expansion panefs. (See Figure 7.5.) This allows for movement of the end pan(cid:173)
`els so that the contents can expand and contract witholtt bulging or otherwise
`distorting the can. The chuck panel is designed to give the proper clearance to the
`double-seaming chuck used to seal the can end to the body. A vital can-end com(cid:173)
`ponent is the compound applied around the perimeter curl. This compound acts as
`a caulk or sealant when the end is mated and double-seamed to the can body. (See
`Figures 7.6 and 7.7.)
`
`Seam
`hicknes
`
`Lining
`compound
`
`,I h
`H
`etg I
`
`i
`
`Can end
`
`Body wall
`
`Figure 7.6
`Double-seaming, the attachment of the can end to the body, involves two curling steps.
`
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`--
`
`Metal Cans and ContaineIS 155
`
`Seaming wall radius -----
`
`Body hook radius
`
`Seaming wall
`
`Body hook
`
`End hook
`
`~ - - Seaming panel radius
`
`Chuck wall
`
`,----- Chuck wall radius
`/
`
`End hook radius ~
`
`M - - - Body wall
`
`Figure 7.7
`The double seam is a
`critical can component.
`Every angle, radius, and
`dimension must be correct
`to ensure a hermetic seal.
`
`TWO-PIECE DRAWN CANS
`
`There are three methods of making steel or aluminum two-piece cans depending
`on the geometry and application:
`
`• Draw
`• Draw and redraw (ORD)
`• Draw and iron (D&I,l
`
`Draw Processes
`
`Shallow-profile cans (cans whose height is less than their diameter) can be drawn
`directly from a circular metal blank. The metal blank is stamped or drawn through
`a die and re-fonned into a new shape. The thickness of the finished can sidewall
`and bottom remain essentially the same as in the original blank. The process is
`sometimes referred to as "shallow draw."
`Blanks for drawn cans may be decorated prior to drawing. Art must be dis(cid:173)
`torted so that when the metal is re-formed, a correct image will develop. (See
`Figure 7.8.) Cans that have continuous decoration across the sidewalls and bottom
`have been printed prior to drawing.
`
`Figure 7.8
`Straight lines become
`distorted in different
`directions during drawing.
`
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`..
`
`156 Chapter Seven
`
`1. Coil feed
`
`2. Cut blank &
`draw cup
`
`3. Wall iron &
`bottom panel
`
`4. Trim
`
`6. Apply O'S
`base coat
`
`5. Wash &
`chemical
`treatment
`
`DO
`D co ( U\ 0
`( 0
`EJ B 8
`
`.
`
`C,
`D
`
`.,,.
`
`(
`
`U\ 0
`
`a
`D
`►
`
`001;1'
`
`7. Varnish
`bottom
`
`8. Cure
`coatings
`
`9. Apply
`decoration
`& bottom varnish
`
`10. Cure
`printing
`inks
`
`11. Inside lacquer
`spray
`
`12. Cure
`lacquer
`
`13. Lubricate end
`
`14. Neck in
`
`15. Flange
`
`16. Pressure test
`
`17. Unitize for shipment
`
`Figure7.9
`The manufacturing sequence for a necked D&I can.
`
`A single-draw operation is limited in how far the metal can be reshaped. Cans
`having a height about equal to the diameter require a second draw. The first draw
`produces a shallow cup. The second draw reduces the diameter as the can is deep(cid:173)
`ened. Cans having a height significantly greater than the can diameter require a
`third draw. If the container is to be thermally processed, si\:!ewall beads are rolled
`into the walls in a separate step. Body flanges for engaging the can end are rolled
`on in a manner similar to that used in three-piece can manufacture.
`
`Draw-and-Iron Process
`
`Carbonated beverage cans arc made by the draw-and-iron (D&I) process. A blank
`disk is frrst drawn into a wide cup (step 2 in Figure 7.9). In a separate operation
`(step 3 in Figure 7.9), the cup is redrawn to the finished can diameter and pushed
`through a series of ironing rings, each minutely smaller in diameter than the pre(cid:173)
`vious one. (See Figure 7. IO.) The rings iron, or spread, the metal into a thinner
`sheet than the original disk.
`The bottom of a D&I can has the same thickness as the starting disk; however,
`the sidewalls are considerably reduced in thickness, and the metal area of the final
`can is greater than that of the initial disk. Necking operations reduce the diameter
`of the can top, thereby reducing the ~d-piece diameter. This results in significant
`metal savings, since the end piece i_s much thicker than the sidewalls.
`The thin walls of the D&I container restrict its use to systems that will not
`undergo severe thermal processing and that will lend s·upport to the walls.
`
`RJRV EX 1021
`
`

`

`Metal Cans and Containers 157
`
`Punch
`
`Bottoming end tool
`
`Wall-ironed can - - - '
`
`Circular ironing dies
`
`Figure 7.10
`The second draw and the ironing stages are all accomplished in one continuous
`movement The punch and the ironing rings are shown in this exaggerated illustration. The
`punch finishes its srroke against th& bottoming tool.
`
`Carbonated beverage cans, where the internal pressure of the carbon dioxide keeps
`the walls from dentiQg, is the primary application. Some noncarbonaled juices
`develop internal pressure with inert nitrogen gas.
`Both steel and aluminum are used to produce D&I beverage cans. Aluminum
`alloys such as 3004 are used for can bodies, whereas the softer 5082 and 5182
`alloys are used for can ends.
`Soft drink producers can use either steel or aluminum equally well. Beer, how(cid:173)
`ever, is particularly sensitive to traces of dissolved iron while being relatively
`insensitive to aluminum.
`Draw-and-iron manufacturing has been used to produce beverage cans as
`large as 2 litres.
`
`Expanded-Wall Cans
`
`Cans produced by conventional manufacturing have straight and perpendicular
`sidewalls. Shaped walls can be incorporated into a can design by sliding the two(cid:173)
`or three-piece can body over an expanding chuck, or mandrel. When the can body
`is in place, movable parts on the mandrel open outward and expand the can walls
`into the selected shape. At the completion of the expansion, the mandrel folds back
`into itself, and tbe shaped can body is removed from the tool. Figure 7.11 shows
`a beer can expanded to take on the appearance of a barrel.
`
`IMPACT EXTRUSION
`
`Impact extrusion forms ductile metals such as tin, lead, and aluminum into seam(cid:173)
`less tubes. Tin and lead were the first metals to be formed by this method, and until
`tbe 1960s most collapsible tubes were either lead or tin. Tin's high cost prohibits
`
`RJRV EX 1021
`
`

`

`158 Chapter Seven
`
`Figure 7.11
`An expanded-sidewall can.
`
`Punch----+
`
`Stripper plate --,-i::=:;i
`
`Extruded
`tube --►
`
`Extruded
`tube ---lo-[
`
`Figure 7.12
`Impact-extrusion sequence.
`
`its use with the exception of collapsiblfrtubes for certain pharmaceutical prepara(cid:173)
`tions. Lead, once the mainstay of the toothpaste market, is now used only for
`applications where its chemical inertness is an asset. Most impact extrusions are
`made from aluminum.
`In impact extrusion, a metal slug ls located on a shaped striking surface. or
`anvil. A punch strikes the slug with great force. Under the enormous impact pres(cid:173)
`sure, the metal flows like a liquid straight up along the outside of the striking
`punch, forming a round, cylindrical shape. (See Figure 7.12.) Tube height is gov(cid:173)
`erned by the thickness of the initial slug and the impacting force.
`
`RJRV EX 1021
`
`

`

`Metal Cans and Containers 159
`
`T
`
`A
`
`DIMENSION
`A
`B
`C
`D
`H
`
`Figure 7.13
`Tube dimensions.
`
`C
`
`DESCRIPTION
`Outside diameter
`Body length
`Wall thickness
`Shoulder thickness
`Neck length
`
`DIMENSION
`I
`K
`L
`T
`
`,(
`'-- t_--""
`DESCRIPTION
`Orifice diameter
`Decorated length
`Shoulder angle
`Finish neck diameter
`
`The shoulders and tip of the collapsible tube are formed as part of the process.
`Tubes with a dispensing hole in the tip will have a hole in the slug, while tubes
`that need a dispenser with a thin web of metal over the opening (a blind end) will
`start with a solid slug. Embossed shoulders are another option.
`The force of the impact work-hardens the aluminum and makes it stiff.
`Collapsible tubes are annealed to remove the stiffness. The tubes are trimmed to
`length, threads are turned into the tube neck, and the tubes are sent for finishing.
`Dimensions given for impact-extruded tubes always refer to the undecorated and
`unfilled tube. Dimensions are given as the outside diameter and the body length
`from the shoulder to the open end. Figure 7 .13 shows these and other dimensions
`that apply to tubes.
`Neck designs are negotiated with the supplier and are specified by a number
`indicating the opening size in 64ths of an inch. Thus, a No. 12 neck has an open(cid:173)
`ing of 3/16 inch. Figure 7. I 4 shows some commonly used tips.
`Metal tubes have a number of distinctive characteristics compared with lami(cid:173)
`nate and plastic collapsible tubes:
`
`• They form the best barrier to all gases and flavors.
`• They have the best dead-fold characteristics (ability to be flattened or rolled
`up). This feature is particularly important for some pharmaceutical appli(cid:173)
`cations, where air suck-back into the partly empty tube could contaminate
`the contents or expose the product to oxygen.
`
`• They can be decorated in a manner that takes advantage of their metallic
`character.
`• They have a wide range of lining options because of the metal's ability to
`withstand high curing temperatures.
`
`RJRV EX 1021
`
`

`

`160 Chapter Seven
`
`A
`
`B
`
`C
`
`D
`
`E
`
`F
`
`Applications
`Tip
`A The round end is the most common tip. Blind-end tubes have a metal mem(cid:173)
`brane across the end and are used for applications where a positive seal is
`required.
`B Screw-eye openings are used mostly for adhesives that would bind a nor(cid:173)
`mal screw-cap closure.
`C Nasal tips are used for nasal ointments and for products that require local
`point application. Eye tips are similar and are used for ophthalmics and for
`fluids that are dispensed by the drop.
`D Mastitis tips are similar to nasal and eye tips but have a fine, needlelike tip.
`E Neckless tubes can be used to dispense powders and for single, entire(cid:173)
`content applications.
`F Grease tips are used for dispensing greases when an applicator tip is
`required.
`
`Figure 7.14
`Typical impact-extruded tube tips.
`
`Tubes are normally coated with a white enamel base and then cured. Tubes are
`printed by dry offset ( offset letterpress), similar to any round container. Most man(cid:173)
`ufacturers offer six colors.
`By starting with heavier slugs, strong cylinders can be made by impact extru(cid:173)
`sion. These have been used to hold special greases and caulks and as humidor
`tubes for expensive cigars. A major application is for aerosol products, where the
`sleek, seamless appearance of these cans is an asset. Unlike collapsible tubes, for
`aerosol cans a stiff sidewall is desirable, and so aerosol cans are not annealed. The
`sidewall is trimmed to length, turned down, and curled over to accept the spray
`nozzle base. (See Figure 7.15.)
`
`CAN DIMENSIONING
`
`Nominal can dimensions are given as the overall diameter by the overall height.
`(See Figure 7.16.) Each dimension is given in three digits. The first digit is in
`whole inches, and the second two digits represent l6ths of an inch. A 307-by-314
`can would be 3-7 /l 6 inches in diam61er and 3- l 4/16 inches high;
`Necked cans where the diameter'of the can body is reduced through several
`stages report dimensions indicating each neck diameter followed by a last
`dimension indicating the height. In metric practice the dimensions are given in
`millimetres.
`
`RJRV EX 1021
`
`

`

`Metal Cans and Containers 161
`
`Figure 7.15
`Three impact-extruded aerosol can designs and a three-piece welded-steel aerosol can.
`All aerosol cans hav(;l __ bottoms that are domed upward against internal pressure.
`
`~ Overall diameter -.J
`-+J Countersink diameter ft-
`
`~ Inside diameter ➔ Overall
`
`height
`
`·"
`
`-JI---- Typically 1.5 mm (1/16 in.)
`
`Figure 7.16
`Nominal can dlrnensions.
`
`PROTECTIVE COATINGS FOR CANS
`
`Most cans require organic coatings to help protect the product and the container.
`In some instances. the tin layer helps maintain flavor and appearance. Evaporated
`milk. some vegetables, and most light-colored fruits can be packed in uncoated tin
`cans, although a somewhat heavier tin deposit may be required.
`
`RJRV EX 1021
`
`

`

`162 Chapter Seven
`
`Table 7.6
`Protective can coatings.
`
`Resin Type
`
`Flavor
`
`Acrylic
`
`Alkyds
`
`Epoxy-amine
`
`Epoxy-ester
`
`Epoxy-phenolic
`
`Oleoresin
`
`Polybutadiene
`
`Vinyl
`
`Vinyl-phenolic
`
`Fair
`
`Poor
`
`Good
`
`Fair
`
`Good
`
`Fair
`
`Fair
`
`Good
`
`Fair
`
`Flex
`
`Fair
`
`Fair
`
`Good
`
`Good
`
`Good
`
`Good
`
`Fair
`
`Good
`
`Good
`
`Color
`
`Good
`
`Good
`
`Good
`
`Poor
`
`Poor
`
`Poor
`
`Fair
`
`Good
`
`Fair
`
`Retort able?
`
`Yes
`
`Fair
`
`Yes
`
`Yes
`
`Yes
`
`Yes
`
`Yes
`
`No
`
`Fair
`
`Various coatings have been developed to solve particular canning problems.
`Some dark fruits bleach in direct contact with tin. In these instances an organic
`coating is essential. Similarly, sulfur-containing foods (meats, corn, onions.
`asparagus, etc.) develop a dark stain when they come into direct contact with tin.
`The stain is harmless but it is unsightly. Special release formulations are available
`for products such as luncheon meats that must be easy to remove from the can.
`Products that contain aggressive solvents or corrosive agents require coatings
`resistant to these chemicals. Table 7.6 lists the characteristics of typical coatings.
`Can coatings should not crack or chip if the can is abused.
`
`DECORATION
`
`Cans may be decorated either by printing directly on the metal or by applying a
`paper label. Generally, high-volume single-product applications favor a decora(cid:173)
`tion applied directly to the metal.