Board, caliper and allowances

Board has thickness, so a dieline is never just the inside size unfolded. The caliper decides how far apart the creases are, and the Box designer adds the right allowance at every fold.

Folding cartons#

A crease folds about the middle of the board, so each 90° fold costs half a caliper of inside length on each side of it. Crease to crease, a body panel is the inside size plus one caliper. Three corrections keep a tuck box on size: the panel opposite the glue flap gets one more caliper (the glue flap lies inside the other side panel), a flap that closes over another is hinged one caliper further out, and the dust flaps are relieved where the tuck slides past.

A board named in points has that caliper by definition: 18 pt is 0.457 mm. A board bought by weight has no caliper until you enter your supplier's figure.

Corrugated score allowances#

Corrugated plants score by a published allowance per flute, measured on the two panels away from the glued joint:

F flute has no published row: it uses the carton rule and says so. Double-wall calipers vary by supplier, so EB and BC boards need your supplier's caliper.

The table is for each flute's nominal caliper. When your board is thicker (a B flute at 3.4 mm, say), the allowances grow to the caliper (one caliper on length and width, two on depth), so the box is never smaller inside than you asked for. Allowances you measured yourself are used as you entered them.

Plant or rigid joint#

A corrugated box's Joint option (or the board's own joint, see calibrating) says how the glued lap is allowed for:

With plant allowances a 12 × 10 × 8 in C-flute box is 3.2 mm short across the glued strip and on size everywhere else; rigid keeps it on size for about 0.7 % more board (5.94 ft² per blank instead of 5.90 ft²). The flat joint gap is 3/8 in by default and at most half the glue lap, so at least half the lap is glued.

Grain and flute direction#

Folding cartons default to the machine direction around the box. Set the direction for each product and box to match your board and folding requirements. Corrugated flutes run along the depth for stacking strength. Blanks may turn 180° on the sheet but never 90°, unless the sheet's grain isn't set.

Calibrate from your samples#

Each board in your materials library can override the allowances after you measure a folded sample: the three corrugated allowances and the joint, or one factor for carton boards. The carton factor (0.5 to 2) scales every caliper allowance, and the fold check folds the board at that factor too: 1.2 means your board behaves 20 % thicker in the fold. A box keeps the allowances it was made with until you update it, so a sent quote never changes size on its own.

The board catalogue#

The Box designer and your board stocks share one catalogue of physical board values. It holds no prices: a board is priced once a stock in your materials library links to it, and the stock can then override the caliper and the allowances. A board with no caliper here needs your supplier's figure before a box can be drawn on it.