The manufacturing of corrugated boxes involves multiple stages, transforming raw materials into durable packaging solutions. Below is a step-by-step overview of the process, from sourcing raw materials to creating finished boxes.

1. Raw Material Preparation

a. Virgin Wood Pulp

  • Source:
    • Softwood trees (e.g., pine, spruce, fir) for long, strong fibers.
  • Process:
    • Wood is debarked, chipped, and chemically pulped using the kraft process.
    • Pulp is then washed, screened, and dried into rolls of kraft paper.

b. Recycled Paper

  • Source:
    • Collected post-consumer and post-industrial paper products (e.g., old corrugated containers, newspapers).
  • Process:
    • Paper is shredded, de-inked, and re-pulped to produce new paper suitable for liners or fluting.

c. Additives

  • Starch-Based Adhesive:
    • Used for bonding layers of the corrugated board.
  • Coatings:
    • Optional wax, polyethylene, or water-based coatings for moisture resistance.

2. Corrugated Board Production

The corrugated board is the foundation of the box, made by combining flat paper liners and a corrugated (fluted) layer.

a. Corrugator Machine

The corrugator machine is the core equipment used to manufacture corrugated board. It operates in several stages:

  1. Fluting Formation:
    • The middle layer (fluting medium) is passed through heated rollers to form the characteristic waves or “flutes.”
    • Heat and steam soften the paper, making it pliable for shaping.
  2. Liner Bonding:
    • A layer of kraft liner is glued to one side of the fluted medium using a starch-based adhesive.
    • Another liner is glued on the opposite side to form a single-wall board.
    • For double-wall or triple-wall boards, additional fluting and liners are added.
  3. Drying:
    • The board passes through heated plates to cure the adhesive and ensure a strong bond.

b. Cutting and Sizing:

  • The corrugated board is trimmed to the desired width and cut into sheets of specified lengths using rotary or longitudinal cutters.

3. Box Conversion

The corrugated sheets are converted into boxes through the following steps:

a. Printing (Optional)

  • Flexographic Printing:
    • Logos, product information, and graphics are printed onto the board.
    • Typically performed before die-cutting and folding.
  • Digital Printing:
    • Used for short runs or highly detailed, customizable designs.

b. Die-Cutting

  • Flatbed or Rotary Die-Cutting:
    • Custom shapes, slots, and perforations are created based on the box design.
    • Common for creating features like hand holes or ventilation slots.

c. Folding and Gluing

  • The sheets are folded along pre-creased lines to form box shapes.
  • Glue, staples, or tape are applied to join edges, creating the finished box structure.

4. Quality Control

Each box undergoes thorough inspection to ensure it meets industry standards and customer requirements.

Tests Include:

  • Bursting Strength Test: Measures resistance to rupture under pressure.
  • Edge Crush Test (ECT): Evaluates the stacking strength of the box.
  • Moisture Resistance Test: Assesses performance in humid conditions.

5. Packaging and Distribution

  • Bundling:
    • Finished boxes are flattened and bundled for easy shipping and storage.
  • Delivery:
    • Bundles are shipped to customers or warehouses, ready for use.