AbstractIn the cross‐cutting of plastic films, the edge life of knives ends when the cutting‐edge geometry in the transition zones is deformed to such an extent that a complete separation of the packaging material web is no longer possible. In nine long‐term tests under almost field conditions, those knife and machine parameters were investigated that determine the development of these zones. It is shown that longer knife‐edge lives can be obtained with high contact pressures, high angles of mesh, low dihedral angles and low cutting speeds. Lateral relative movements of the packaging material web proved to be a distinct improvement. The knife‐edge life criterion was determined by the presence of transitional zones of ‘wear’ at the extremes of the cutting zone. The quality of cutting edge and value of cutting pressures do not provide reliable information on the wearing condition