Corrugated Lecture Notes PDF

CORRUGATED LECTURE- CORRUGATED INDUSTRY - Integrated plants: consume at least 50% of materials from affiliated mills - Independent plants: source more than 50% of materials from external suppliers TYPES OF CORRUGATING PLANTS - Sheet feeder: manufactures corrugated board in sheet form for co...

CORRUGATED LECTURE- CORRUGATED INDUSTRY - Integrated plants: consume at least 50% of materials from affiliated mills - Independent plants: source more than 50% of materials from external suppliers TYPES OF CORRUGATING PLANTS - Sheet feeder: manufactures corrugated board in sheet form for converters, also known as corrugator plant - Sheet plant: purchases sheets from sheet feeders and converts them into boxes - Corrugator box plant: both manufactures boards and converts them into finished products, integrating both processes MANUFACTURING PROCESS OF CORRUGATED BOARD - Linerboard: typically made from kraft unbleached fourdrinier, it may be bleached, mottled, or oyster - Fluting medium: produced through a semi-chemical process, it contains a higher recycled content and its usually unbleached - Adhesive: a starch based adhesive is used, mixed in the plants “kitchen” to ensure optimal bonding - PROCESS OVERVIEW: the manufacturing process begins with the fluting medium being plasticized to become pliable. It passes through corrugating rolls where the tips of the flutes are coated with adhesive. The first liner is pressed onto the fluted medium, followed by the addition of a second liner, creating a double faced board. The board then passes through heated plating for curing and drying ensuring a strong bond. Finally the board is cut into sheets (blanks) for further processing into boxes CUTTING, SLITTING, AND SCORING - Scores: corresponds to the flaps of the box - Cuts: corresponds to the length needed for a box blank CORRUGATING BOARD CONFIGURATIONS FLUTES PROFILE - Defined by: height and pitch - Largest flute: A - Smallest flute: E - Larger profile: cushioning and compression - Smaller profile: better printing, primary packages and point of purchase displays  FLUTE MEDIUM HEIGHT A 3/16 - 1/4 B 1/8 C 5/32 E 1/16 F 1/32 SINGLE FACER KEY DETAILS - Preconditioning (heat and steam) for the liner and fluting medium - Fluting medium: moisture and heat plasticize the board - Liner: aids in adhesive bonding - Adhesive - Viscocity determines how much adhesive is delivered - Pressure between liner and medium - Liner 1 is passed between the pressure roll and corrugating roll - More pressure is applied to liner 1 than liner 2 (liner 1 is smoother/ easier to print on) DOUBLE FACER KEY DETAILS - Bridge gives more time for the bond between medium and liner 1 to cure - Adhesive - Applied to tips of flutes - Pressure - Less pressure is applied in order to prevent damage to flute - Liner 2 is outside of box - Pre-printed liners are always applied to double facer BOARD SPECIFICATIONS (BMC) - Basis weight components - Sheet size - Width is the same direction as flutes - Length is machine direction - Strength of board - Mullen burst - Edge crush test - Other performance properties - Wet strength COATINGS - Water resistance: polyethylene, wax, water based - Moisture resistance: most common low melting paraffin  - Oil and grease resistance - Abrasion resistance: reduce scuffing of graphics and of product CORRUGATED BOX DESIGN MATERIALS AND CONSTRUCTION - Linerboard: typically unbleached kraft paperboard, with options for coating to enhance printability - Corrugated medium: usually made from unbleached semi-chemical (NSSC) harwodd pulp, both virgin and recycled. It provides the structural integrity and cushioning from the box - Adhesive: bonds the linerboard and corrugated medium together - Fluting orientation: flutes are almost always oriented parallel to the depth dimension for optimal stacking strength DIMENSION AND STYLES - Dimensioning: - Inside dimensions: ensure product fit - Outside dimensions: account for transportation factors like scoring allowances - L= longest of the side panels - W= shortest of the side panels - D= distance between top and bottom openings - Scoring allowance: amount of material taken up in the fold of the box - Other things to consider: - Space on shelves - Space inside trucks, railcars or bins - Width of conveyors - Fillers and sealers - Center of gravity - Inserts or cushions to be used - Common styles: - Regular slotted container (RSC): the most common style with all flaps the same length - Half slotted container (HSC): similar to RSC but without top flaps - Full overlap (FOL): offers extra protection with fully overlapping flaps - Center special slotted container (CSSC): features flaps that meet in the center - Telescope boxes: two-piece boxes offering greater depth and protection - Folders: one piece construction that folds into shape - Rigid boxes (BLISS): offers premium protection and presentation - Self erecting: designed for quick and easy assembly MANUFACTURING PROCESS - Key stages: - Printer slotter: prints, cuts, creases, and slots the corrugated board - Folder gluer: folds and glues/ stitches the blanks into boxes - Flexo-folder gluer: combines printing, slotting, folding, and gluing for high output  - Die cutting: used for creating unique designs, cutouts and perforations - Types: rotary and platen (platen offers higher precision but is slower) PRINTING AND FINISHING - Direct printing: common, suitable for small flutes - Preprinting: offers higher quality, economical for short runs - Litho-labeling: glues printed labels onto the board - Flexography: fast, fine print, quick set up time - Silk screen: low volume, high quality - Offset lithography: best for small flutes - Digital: good speed and resolution PREFORMANCE AND TECHNIQUES: - Duration of loads: strength decreases over time under load - Humidity: high humidity reduces strength - Stacking pattern and position: overhang and position within the stack impact load distribution - Warehouse conditions and transportation modes: environmental factors and vibrations during transit play a role - Box compression test (BCT): 5.87 x ECT x caliper of combined board x box perimeter - ASTM D 4169: transportation simulation - ASTM D 642: compression strength JOINTS - Glued - Needs flaps - Least expensive - Starch based or hot melt adhesive - Need to allow drying and set-up time - Stitched or stapled - Needs flap - Strongest - May be hazard to product and people - Expensive - Taped - No flap - Weakest - PSA tape or water activated BOX CONVERTING FLEXO-FOLDER-GLUER - Used to make the simplest boxes: RSC - Combines several operations in one machine STEPS - Feed section: sheets are fed to the machine - Slit to the width of the blank - Scored across the flutes - Cut to the length of the blank - Rollers feed them one at a time for printing - Fed with the soft edge (short) direction - Flexo section: blanks are printed (flexography) - Scoring section: body scores (creases) are made - Slotter section: slots are cut to create top and bottom flaps - Folder-gluer section: folds along the second and fourth creases and applies adhesive - Delivery section: counts finished boxes and bundles in predetetmined sets PRINTING - Flexography is the most common and the cheapest - Typically 2 color - 4 to six colors also common - Liners can be pre-printed to create better print quality: flexo and gravure are used depending on runs - Litholaminations: lithographed sheet is printed and then added to the single face board or to the combined board - Commodity boxes will have minimal printing - High quality printing adds advertising opportunity PRINTED ELEMENTS 1. Box maker certificate 2. Brand identity for contents 3. SKU: stock keeping unity number BOX MAKER CERTIFICATE - Usually placed on bottom outer flap - Box maker name and location - Minimum combined weight of facing and minimum burst test - OR - Edge crush value for the combined board BRAND AND COMPANY - Primary identification on a box - Might be colorful and high quality or might be minimal depending on company objectives STOCK KEEPING UNIT - Packer/ filler’s code for each product variation  - Brand - Size - Configuration - Flavor - Used to keep inventory - Used at many stages of supply chain: must be easy to read - May be printed by the box maker or may be added as a label OTHER PRINTED ELEMENTS - Information about recylability or recycled content - Handling instructions: “this side up”, “do not stack” - Standard sets of symbols: NMFC - International symbols are standardized by ISO PAPER CHARACTERIZATION AND PROPERTIES PAPER CHARACTERIZATION - Factors considered - Moisture content - Physical characteristics - Strength properties - Optical properties MATERIAL VS PACKAGE TESTS - Material tests: conducted before conversion, mostly by suppliers - Package tests: focus on performance, used by converters and buyers TESTING PROCEDURES - Publishes standards: ASTM, TAPPI, ISO - Ensures repeatability and reproducibility - Repeatability: one operator in one lab - Reproducibility: different labs and equipment MOISTURE CONTENT - Equilibrium moisture content: moisture content of a given area of material when it reaches equilibrium in an atmosphere with a given relative humidity and temperature - Isotherms: shows how moisture absorption varies based on relative humidity - Hysteresis: the difference in moisture content observed when drying a material compared to when increasing its relative humidity EFFECT OF MOISTURE CONTENT ON PAPER - Good storage practices are key - moisture resistant wrappings, follow manufacturers recommendations for storage, allow materials to come to equilibrium, and protect after process - Moisture content affects both dimensions and flatness - Dimensional effects - Fibers swell and shrink more on thickness than length - Mechanical pulp reacts more than chemical pulp - Curling: due to uneven fibers swelling, mostly along the machine direction (MD) PHYSICAL PROPERTIES - Basis weight: paper weight per ream - Caliper: paper thickness (0.001’ = 1 pt) - Density: basis weight/ caliper - Smoothness, gloss, gas transmission, and curl all relate to performance BASIS WEIGHT/ GRAMMAGE - Price specified in $/ton - Related to strength and stiffness, but not solely defining it - Ream: - Paper: 3000 ft2 - Paperboard: 1000 ft2 MECHANICAL PROPERTIES - Includes tensile, tear, fold, and compression tests - Tensile strength = MD>CD - Coefficient of friction: relates to machiniability and behavior in storage and packaging lines TEAR STRENGTH - Measures the energy required to propagate a tear - Elmendorf test BURST STRENGTH - One of the most widely used tests - Correlated to tensile strength - Used in industrial linerboards and papers on combined corrugated board OPTICAL PROPERTIES - Includes brightness, opacity, gloss, smoothness, and color - Influenced by surface roughness, coatings, basis weight, and light interactions - Interactions with light: - Reflectance: glossy → more reflectance - Scattering: more scattering → whiter looking - Transmission: how much light passes through - Light absorption: non-transparent or colored material absorbs instead of reflecting PAPER TYPES - Kraft paper - Made from sulfate pulp, used for multiwall sacks and wrapping  - Strong - Often unbleached - More tensile strength in the machine direction because of fiber direction - Sulfite paper - Typically bleached - Used for smaller bags, labels, and laminating PAPERBOARD TYPES - Solid bleached sulfate (SBS) - Preferred for high speed packaging - 100% virgin pulps - Solid unbleached sulfate (SUS) - Clay coated for printability - May contain some recyled pulp - Stronger/ heavier - Chipboard - 100% recycled - Doesnt work in fast machine - Low strength - Folding boxboard - Most common in Europe - Mechanical pulp is used in middle layers (adds stiffness) - Outer layer is bleached chemical pulp - Back of board is not bright white (cream) because bleached layer is translucent - Is using for food or high-end products no recycled fiber CONTAINERBOARD TYPES - Linerboard - Southern pine or douglas fir fibers - Two or three ply sheet - Corrugating medium - Hardwood and recyled fiber  - Stiffness and low cost TYPES OF PAPER PAPER TYPES - Tissues - Lightest type of paper - May be used for laminations - Neutral pH and low chemical residues may be required depending on application - Used for tea bags - Greaseproof - Highly refined fibers with high hydration create a non-porous paper, resistant to oil and grease - Lots of refining → beating so the cells collapse, making the fibers more permeable - Fast food wrappers - Glassine - Supercalendered greaseproof paper treated with steam heat to collapse fibers and enhance hydrogen bonding - Results in a smooth, semi-transparent surface resistant to air and essential oil vapor - Paper you would use for a product sensitive to air - Thin - Parchment paper - Treated with sulfuric acid, partially dissolving cellulose and leading to fibers swelling, extensive hydrogen bonding and pore plunging - Stronger when wet than dry, with a chemically neutral, fiber free surface - Highly grease resistant - Clay coated papers - Coated with an aqueous mix of clay and pigments for improved graphics and smoother surfaces - Reduced pore size enhances barrier properties - Labels, bags, and laminations LAMINATED AND EXTRUSION COATED PAPERS - Extrusion coating: melted plastic is applied to the paper surface for wet conditions and heat sealing - Laminations: a sheet of plastic film, foil, or another paper is bonded to the paper using a thin layer of melted plastic adhesive - Foil laminations are common, with low density polyethylene being the most common plastic - Different plastics address specific needs like… - Sealing through dust - High temperature applications (oven/ microwave trays) - Longer shelf life  - Blister board packaging using vinyl coating METALLIZED PAPER - Offers the look of foil without lamination - Achieved by vaporizing aluminum and depositing a thin layer of particles on the paper surface - Cost- effective due to less material usage, although the aluminum layer is not continuous CELLOPHANE - Manufacturing - Made from high purity wood pulp dissolved in carbon disulphide and sodium hydroxide, then cast onto a drum and stabalized with sulfuric acid - Plasticized with ethylene glycol and propylene glycol, and coated with nitrocellulose or PVDC for barrier and heat sealing properties - Current use - Reduced usage due to the availability of cost effective plastics like PP and PE - Remains in niche markets requiring stiffness, a dead fold (hard candy), and specific color qualities (gift baskets) MOLDED PULP - Process: fiber slurry formed into 3-dimensional shapes like egg cartons, corner protectors, plates, trays, and produce trays - Two main processes → plain molding and precision molding - Plain molding: slurry deposited on screen molds, water removed by pressure and sometimes vacuum, then dried with heat - Produces thick parts (cushioning, corner protectors) and thinner parts (trays, cartons) - Precision molding: used when appearance is important- produces smooth surface parts using “thermoformed fibers” between two heated matching molds - Parts are fully dry upon leaving the mold EQUATIONS - ESTIMATING COST OF BOX - MCKEE EQUATION: - 𝐵𝐶𝑇 = 5. 87 𝑥 𝐸𝐶𝑇 𝑥 𝑐𝑎𝑙𝑖𝑝𝑒𝑟 𝑜𝑓 𝑐𝑜𝑚𝑏𝑖𝑛𝑒𝑑 𝑏𝑜𝑎𝑟𝑑 𝑥 𝑏𝑜𝑥 𝑝𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 - BASIS WEIGHT CALCULATION: TEXTBOOK NOTES CHAPTER 8: - Repeatable: if the same sample is tested in the same lab again - Reproducible: from one lab to another - TAPPI: technical association for the pulp and paper industries - ASTM: american society for testing and materials - ISO: international standards organization - Material tests: address the material in isolation, evaluating properties like thickness or tensile strength - Primarily for suppliers - Package tests: - For the converter package, and specify properties like compression strength or drop-height survival - Primarily for buyers - 8.1 caliper - Thickness - Paperboard: >10 points - Paper: