At a takeaway counter there is no time to tape each box shut: the server picks up the box, presses the base in one motion and it locks itself. What gives that speed is not the artwork but the tab and crease geometry of the auto-lock base. When a food packaging cutting die is designed, the lock-tab form, the crease allowances and the behaviour of greaseproof board are planned together. This guide explains those three decisions with real figures.

A food box has to set up fast

Burger, wrap, pastry and dessert boxes are usually stored flat-packed and assembled at the moment of service. A classic glued base falls short here: you cannot wait for adhesive to cure and there is no glue at the counter. With an auto-lock (crash-lock or snap-lock) base, the four base flaps interlock and the box locks the instant it is pressed; the server brings the box up to ready in a single motion.

That behaviour starts in the die. The cut form of the base flaps, the gap the lock tab drops into and the position of the crease lines decide whether the box snaps shut with a clean “click”. However good the graphic design is, if the tab geometry is wrong the box will either pop open or refuse to close.

  • Flat-pack storage plus fast counter assembly is the core demand of a food box.
  • An auto-lock base locks on pressing, without waiting for glue.
  • The lock behaviour comes from the tab, gap and crease geometry in the die.

Lock tab and creasing balance

In a crash-lock base, the lock tabs on two opposing flaps pass under the other two flaps and seat in place. The tab width, shoulder angle and entry radius decide how firmly the lock holds. A tab that is too narrow or sharp-cornered tears in use; one that is too wide will not pass under the flap and the box will not close. In practice the tab shoulder is set back 1.5–2 mm (a relief allowance) so the tab enters easily yet does not sit loose.

Crease allowances are thought through with the lock. The crease lines of the base flaps are positioned to compensate for board thickness: on 350 gsm coated board the crease allowance is set slightly wider than for 300 gsm, otherwise the flap will not fold square and the tab arrives at the wrong angle. Building cut and crease in balance on the same die is what makes the lock give the same “click” on every box.

  • Tab width, shoulder angle and entry radius set how firmly the lock holds.
  • A 1.5–2 mm relief at the tab shoulder gives a tight but non-jamming lock.
  • Crease allowance follows board gsm; if the flap does not fold square the tab will not seat.

Coated and greaseproof board behaviour

Most food boxes are made from coated board for a grease and moisture barrier: single- or double-sided coated, PE lamination or a water-based barrier coating. This coating behaves differently from plain board under creasing and cutting. On a coated surface, if the crease runs through the wrong channel the surface cracks and grease seeps through the crack; that is why the crease channel is chosen a little more generously on coated board and the creasing rule back is rounded rather than sharp.

Coating matters at cutting too: on PE-laminated board, if the rule edge does not cut cleanly you get fibre pull or coating peel at the edge, which becomes a hygiene problem on a food-contact edge. Rule height and edge bevel are chosen to suit the coating thickness; where needed, the cut depth is trialled on a sample for a clean edge on the coated face.

  • On coated board the crease channel is wider and the crease back is rounded.
  • A wrong crease cracks the coating; grease and moisture seep through the crack.
  • On PE-laminated board, rule edge and height are validated on a sample for a clean cut.

Layout, ups and waste

Food boxes are usually high-volume jobs, so instead of a single up, several boxes are placed across the layout. Following the blank shape, the boxes are nested so they interlock; if the protruding flaps of an auto-lock base drop into the gap of the neighbouring box, more boxes come off the sheet and waste falls. The number of ups is set by the press sheet size and the board size in use.

When the layout is planned, the bridge allowance between rules, stripping access and the machine’s maximum cutting area are weighed together. A good ups layout both lowers paper waste and lets the stripping die clear the waste cleanly; a poor layout means both material loss and jams on the press.

  • Nesting the blanks raises the number of boxes per sheet and cuts waste.
  • The number of ups follows the press sheet size and board size.
  • Bridge allowance, stripping access and the maximum cutting area are planned together.

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 or box sample
  • Board type, gsm, coating and quantity details
  • Critical dimensions, lock type or production notes
  • Deadline expectation and delivery preference