In corrugated cutting the same die gives a different result when the flute direction changes: a crease that folds cleanly one way cracks or crushes the other. Flute direction is therefore not a detail settled after design but the first input to the die layout, and no layout plan is drawn before it is read together with the drawing.

Flute direction decides crushing

The strength of corrugated board lies in the direction of the flute: cut and crease lines running along the flute meet little resistance, lines running across it have to collapse the flute. In a box form placed the wrong way the load-bearing panels end up in the weak direction; the box dimensions are right but it buckles under load.

On the drawing the flute direction is therefore shown with an arrow and the load-bearing panels are stated. A sheet layout may rotate a part to reduce waste; but if the rotation puts a load-bearing panel in the weak direction, the material saving comes out of the box’s strength. When critical fold lines are marked, the die is built accordingly on those lines.

  • Flute direction is shown with an arrow on the drawing.
  • Material and flute type (E, B, C, double wall) are stated.
  • Load-bearing panels and critical fold lines are marked.

The crease line works with the flute structure

On corrugated board a crease does not behave as evenly as on solid board: a crease along the flute folds easily, a crease across it has to crush the flute and wants a wider, rounder profile. On difficult lines a cut-crease combination, alternating short cuts with crease, makes the fold easier.

Channel and pressure decisions follow the flute type; the same drawing wants one profile on E flute and another on C flute. The fold direction (inward or outward) is stated too; a crease folded to the outer face stretches the outer liner and raises the cracking risk on a printed surface. The sample check is therefore made on the folded box.

  • E, B, C or double-wall information is written on the order.
  • Fold direction (in/out) and print face are stated.
  • The sample is checked as a folded box on the real material.

Rubbering affects product release

On corrugated, waste and product leave the die at different stiffnesses; a coarse flute springs back more and the rubber is chosen softer and thicker. Rubber that presses too hard crushes the flute before the rule arrives; too little rubber leaves the piece hanging on the rule and a stoppage begins.

Narrow pieces and small inner waste are marked on the drawing; rubber hardness in the narrow zone is chosen separately. When the press pressure is noted, the rubber layout is built for that pressure and the search for a setting at the first trial gets shorter.

  • Waste areas and narrow pieces are shown separately on the drawing.
  • Rubber hardness in narrow zones is chosen separately.
  • Machine type and working pressure are noted in the message.

Digital print and lamination are checked separately

On printed or laminated corrugated the risk of surface cracking and marking rises: the ink layer stiffens the outer liner, lamination carries the fold stress to the surface. The risk is highest on a crease across the flute; visual quality is assessed together with the production decision and the crease profile is softened where needed.

A photo of the printed surface and the lamination information are therefore added to the file. On the first sample the crease line is folded and the edge marks and any whitening of the outer liner are checked by eye; if there is a problem the pressure is not raised, the crease profile and channel are reconsidered instead.

  • A photo of the printed surface and lamination information are added to the file.
  • Cracking risk on creases across the flute is checked separately on the sample.
  • Edge marks and whitening are examined on the first sample, folded.

Quote details we clarify together

When the file, material, quantity and deadline are clear, the quote conversation moves faster and with less back-and-forth.

  • Current revision file
  • Material and quantity details
  • Critical dimensions or production notes
  • Deadline expectation and delivery preference