Clear or rigid plastics do not behave like board: a sharp corner, high pressure or the wrong rule edge leads to cracking and whitening that is invisible on the cutting table and appears on the shelf. Preventing cracks takes four steps: knowing the thickness, giving the corner a radius, agreeing the visible surface up front and making a trial cut before the production run.

Material thickness is the first decision

The same shape cuts cleanly on thin acetate and can crack on thick PVC; as thickness grows the stress built up during the cut grows with it, and the angle, height and pressure balance of the rule edge change accordingly. Flexibility matters too: rigid PET and soft PVC do not give the same edge from the same rule.

Thickness is therefore written in millimetres on the order, with the material type and hardness by name; where possible an uncut sample is sent. Even two PVC sheets carrying the same name can differ in brittleness through their additive ratio; when the supplier or lot changes this information is shared again.

  • Thickness is stated in millimetres with material type and hardness.
  • An uncut sample of the real material is sent where possible.
  • A change of supplier or lot is noted on the order.

A corner radius lowers the cracking risk

Plastic is not a fibrous material like board but one that stores stress; a sharp inner corner concentrates the stress from the cut at one point and the crack starts there. The crack usually advances quietly not at the cut but during folding, transport or cold storage; a box that looks sound on the sample separates on the shelf.

Where the product allows, every inner corner gets a small radius; even a rounding the eye cannot see removes the crack origin. Critical holes and narrow necks are marked on the drawing; details that seem to demand a sharp corner usually become both producible and indistinguishable with a small radius, and the decision is taken together with the workshop.

  • Inner corners are checked; no inner corner is drawn with zero radius.
  • Critical holes and narrow necks are marked on the drawing.
  • A radius revision is assessed together before production.

Print and cut marks can be visible

On clear material the cut edge is the face of the product: whitening, scratches or rubber marks that hide on board show at once on plastic. A blunt-edged rule separates the material by crushing rather than cutting and leaves whitening on the edge; that mark is the visible evidence of excess stress.

The visual expectation is therefore agreed at the start: which surface is visible, is there a protective film, from which face will the cut be made. Protective film information and the visible face are stated on the order; when the edge appearance on the sample is shared as a photo, rule edge and rubbering are chosen for it.

  • Protective film information and the cutting face are stated.
  • The visible face and edge expectation are agreed at the start.
  • The sample edge and surface are shared as a photo.

A trial cut reduces the production risk

On plastic a trial cut usually gives the most reliable answer: edge cleanliness, whitening and any crack origin at the corners are checked on a small piece, and pressure and rule decisions are settled from the first result. The lowest pressure that cuts through is the right pressure; more crushes the edge.

The trial has two stages: a cut check first, then a use simulation; the fold lines are worked, the product is brought to shape and, where possible, left for a few days in the environment it will live in. The approval step before the production quantity keeps its own slot in the schedule; when the lot or supplier changes the test is briefly repeated.

  • The test is made on a small piece; edges and corners are checked.
  • Edge whitening is checked; pressure is kept at the lowest value that cuts through.
  • An approval step is set before the production run; the test is repeated on a lot change.

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