Industrial processes

Coating is process in which a thin, continuous layer of material is applied to the surface of a packaging substrate (paper, board, plastic, metal, or glass) to modify its functional, protective, or aesthetic properties. It is engineered to provide barrier performance (against moisture, oxygen, grease, or light), adhesion properties, mechanical resistance, printability, or decorative effects.

Corrugation is the process of shaping a paper medium into a wave-like (fluted) structure under heat and pressure, which is then laminated between flat paper liners to form corrugated board. This fluted core provides strength, rigidity, and cushioning, making corrugated boards ideal for packaging.

The flutes can be produced in different sizes and profiles (e.g. A, B, C, E, F flute), each offering a specific balance of cushioning, stacking strength and material thickness.

Corrugated board can be single-faced, single-wall, double-wall or triple-wall, depending on the number of fluted layers and liners combined, allowing the structure to be tailored to different load-bearing and protection requirements. Thanks to its lightweight yet resistant structure, corrugated board is widely used for shipping cartons, secondary packaging and point-of-sale displays across virtually every industry.

Creasing is the formation of a groove in paperboard by compression between tools, intended to facilitate folding without surface rupture.

During the operation, the paperboard is weakened along well-defined lines that then act as hinges for folding, since attempting to fold uncreased paperboard typically causes the surface plies to crack or the fold line to remain undefined. The crease is formed using a creasing rule, a thin steel strip with a round, smooth edge, which presses the paperboard into a matching groove cut into a make-ready (also called matrix or counter-die) positioned beneath it, producing a permanent deformation. The relationship between the crease's width and depth is critical to quality: a crease that is too shallow or wide makes folding difficult, while a deeper, narrower crease generally produces a cleaner, lower-resistance fold.

Grammage also affects the process: thin papers (below roughly 180 g/m²) are often folded without any surface preparation, whereas heavier paperboard (above roughly 600 g/m²) typically requires multiple creases or scoring prior to folding.

Die-cutting is a mechanical converting process where a die (a hardened steel tool or mold) is pressed into packaging material to shear or cut it into a specific shape.

Depending on production requirements, different die-cutting technologies can be used, ranging from flatbed and rotary die-cutting, suited respectively to thicker materials/short runs and high-speed continuous production, to laser and digital die-cutting, which offer greater precision and flexibility, particularly for complex patterns, short runs or prototyping.

In packaging, die-cutting is widely used not only to cut folding cartons, corrugated boxes, labels and inserts to shape, but also to create functional features such as transparent windows, perforations and score lines that facilitate opening, folding or tearing.

The choice of die-cutting method and tooling therefore directly affects production speed, cutting precision and the range of achievable shapes and finishing details.

Extrusion coating is a process whereby molten plastic is applied to a thin substrate (paperboard, paper, plastic film, aluminium foil etc.) and subsequently chilled to form an extremely thin, smooth layer of uniform thickness.

The molten plastic can be used as an adhesive to laminate a plastic film or a metal foil.

In addition to lamination, extrusion coating is mainly used to provide protection against moisture, act as a barrier to gases (water vapour, oxygen, aromas, etc.), offer grease resistance, ensure heat-sealability and create an attractive appearance (glossy surfaces).

The process is carried out by extruding the molten polymer through a flat slot die directly onto the moving substrate, which is then pressed against a chill roll to rapidly cool and solidify the coating while defining its surface finish.

Low-density polyethylene (LDPE) is the most commonly used resin due to its good adhesion, sealability and processability, although other polymers such as polypropylene (PP) or ethylene vinyl acetate (EVA) can be used to achieve specific barrier or performance properties.

Because the coating is formed directly on the substrate in a single continuous pass, extrusion coating is typically faster and more cost-effective than conventional adhesive lamination for high-volume applications.

Dry forming is a fiber-based packaging technology that combines airlaid cellulose fibers with 3D thermoforming to create rigid, renewable packaging without the use of water or traditional wet pulp methods.

The process begins by separating cellulose fibers from the raw material and distributing them, through a dedicated air system, into an airlaid forming station, where they are evenly deposited and interlocked into discrete pads (or, in some process variants, a continuous web) of consistent grammage.

The formed fiber structure is then transferred to a 3D pressing stage, where heat and pressure are applied to bind the fibers together and shape them into the final packaging geometry, again without the addition of process water.

Depending on product requirements, finishing operations such as trimming, cutting or surface treatment may follow, and chemical additives can be incorporated to enhance properties such as water or oil resistance and mechanical strength.

Folding‑gluing is the converting process that transforms a flat, die‑cut, and pre‑creased carton blank into a finished folding carton by folding its panels along defined creases and bonding them with adhesive (typically hot‑melt or cold glue) in a continuous inline operation.

Blanks are fed individually into the machine and precisely aligned before critical creases are pre‑broken, or pre‑folded, to a partial angle in order to condition the board and ensure reliable, high‑speed folding downstream.

Adhesive is then applied to defined glue flaps in a precise pattern synchronized with blank position and machine speed, after which the panels and flaps are folded into their final position through a sequence of belts, rails, hooks and guides, bringing the glued surfaces into contact.

The folded cartons subsequently pass through a compression section that maintains pressure for a defined time to allow the adhesive to set and reach adequate bond strength before being discharged.

Finished cartons are then counted, formed into shingled streams or bundles, and made ready for packing, palletizing or direct feeding to downstream cartoning or case-packing equipment.

Gluing is a joining process in which an adhesive substance is applied between two surfaces, creating a bond through adhesion to the substrates and cohesion within the adhesive layer as it cures, forming a permanent or semi‑permanent joint.

Lamination process consists of bonding together two or more films of different materials (i.e. Al/Paper,  Al/Plastic, Plastic/Paper etc.).

By combining materials with complementary properties, lamination allows the resulting structure to achieve barrier performance, mechanical strength, printability and sealability that none of the individual layers could provide on their own, making it a key process for producing high-performance flexible packaging.

Several technologies can be used to bond the layers together, including

adhesive lamination, in which a wet or solvent-based adhesive is coated onto one substrate before the layers are pressed together and cured;

extrusion lamination, in which a molten polymer is extruded directly between the two substrates, acting simultaneously as the bonding layer;

and thermal lamination, in which heat and pressure are applied to activate a heat-sealable coating already present on one of the substrates, without the addition of a separate adhesive.

Press forming is a discrete deformation process in which a sheet‑like metallic or fiber‑based substrate is shaped into a defined three‑dimensional geometry by compressive force applied between a punch and die in a press system. The process induces controlled plastic or viscoelastic deformation, depending on material class, and relies on the mechanical properties, frictional behavior, and tool design to achieve dimensional accuracy and functional performance.

With metallic substrates such as aluminium, forming is typically carried out at room temperature and can involve a blank holder to control material flow and prevent wrinkling, with the depth and complexity of the shape limited by the material's ductility before tearing occurs. With fiber-based substrates, such as moulded pulp or paperboard, press forming is generally combined with heat and, in some cases, moisture control, so that the fibers can be rearranged and consolidated into the target shape without excessive cracking or splitting of the sheet.

The technique is widely used in packaging to produce rigid, self-supporting formats such as trays, cups, lids and blister-type components, where consistent wall thickness, edge definition and stacking strength are key quality requirements.

Because each ply is fed at an angle rather than at right angles to the mandrel axis, the resulting seam runs helically along the tube rather than straight, and successive layers overlap and stagger relative to one another, distributing joints around the circumference and along the tube's length. As the mandrel rotates continuously, the plies are drawn forward and wound onto it in an uninterrupted helix, allowing the tube to be cut to any required length after forming, unlike convolute winding, where tube length is constrained by the width of the pre-cut sheets.

This continuous feeding method makes spiral winding particularly suited to high-speed production of long tubes and cores, with the number of plies, paper grade, winding angle and adhesive type adjustable to achieve the required strength, rigidity and surface finish.

Vacuum metallising is a process in which a thin layer of metal, typically aluminium, is deposited onto a plastic film, paper or other substrate inside a vacuum chamber, through evaporation and condensation of the metal at the molecular level.

The substrate is unwound and passed close to metal-coated ceramic filaments or boats, which are resistively heated until the aluminium wire fed onto them vaporises; under the low pressure of the vacuum chamber the metal vapour travels in a straight line and condenses onto the cooler, moving substrate, forming a continuous, extremely thin metallic layer typically only a few tens of nanometres thick.

Because the coating is so thin, metallized films retain much of the flexibility, transparency (when viewed against light) and processability of the base substrate, while gaining a reflective, mirror-like appearance together with barrier properties against light, oxygen and moisture.

Vacuum metallizing is widely used in flexible packaging (for example on BOPP, PET or paper webs) to enhance shelf appeal, provide product protection, and, in some applications, offer a lower-cost, easier-to-recycle alternative to laminating a separate aluminium foil layer.