Rotary dies, like flatbed dies, are used widely in the production of packaging in the corrugated industry where the choice between the two often comes down to the volume of product needing to be die cut.
Dies can be designed to perforate and crease the material at the same time as cutting it. A well designed die will create a packaging product that is ready for assembly as soon as it comes out of the press.
Rotary dies are often run in-line with a printing press so that the blank comes straight through print units and directly into the rotary die. Indeed, on casemaker machines the cartons are also glued in line so that the whole boxmaking process is effectively completed in one machine. Such machines can run at speeds up to 20,000 boxes per hour.
A very wide variety of industries rely on flatbed and rotary dies for their packaging needs. Everything from ready meals, premade sandwiches and cereals to beverages, medicine and other pharmaceuticals are packaged using die cut products.
It is not only packaging that is produced using rotary die cutting. Gaskets for many different industries are also produced this way as are electronic components, decals, free-standing point of sale units. Circuit boards printed onto flexible plastics have a range of uses particularly in compact electronic devices. These can be cut to shape quickly and easily using cutting dies, as can decals and fascias for the devices.
Point of sales displays are commonly fabricated using flat dies. These are a cost effective way to make an impression on customers at the point when they are making a choice as to what product to purchase.
Characters can be punched (using Coscode or Perfatype) directly into the material for batch numbering or marking dates. Braille components can also be fitted to flat dies. This is particularly important for the production of pharmaceutical product packaging. Many countries require that these products have Braille labelling.
Managing Accuracy with Rotary Dies
The production of the actual die itself is a process that requires a great deal of skill and expertise. Rotary dies in particular are more challenging to fabricate due to their shape. While the cylindrical form allows for higher running speeds, when it comes to making the die itself the shape is certainly not straightforward.
Technological capabilities such as laser cutting and Computer Aided Design have made the process more efficient but there are some challenges that only the hand of a skilled craftsperson can overcome.
One of the main challenges posed in the fabrication of a rotary die relates to correct allowances for the rotational distances and speeds at which the die and anvil cylinder rotate.. This article on the International Association of Diecutters and Diemakers website goes into the subject in a lot more detail but essentially the problem is one of circumference. The circumference of the die at the tip of the blades is larger than that at the point where the blade is mounted and due understanding and allowances have to be made where appropriate.