Rotary Equipment and Processes
The Rotary Die Cutting Press and the Converting Process
The primary piece of equipment used in rotary die cutting is the die cutting press. In general, a rotary press allows processing of material in roll form through various stations in the press, with each station completing a separate processing step toward completion of the final product. Basic rotary processing steps may include a combination of printing, laminating, die cutting, or embossing, in any combination. Some die cut parts may require several separate stations in sequence to complete all necessary cuts. Very advanced press equipment may also include stations dedicated to laser cutting, heat sealing, optic tolerance inspection, or even coating and drying. The general term for rotary processing is converting, named for the progressive act of converting roll stock materials into a finished product.
This discussion will focus on the die cutting stations of the rotary press. The die cutting station contains two main elements – a cylindrical cutting die and a corresponding cylindrical anvil, which rotate in sync and are typically driven by gearing fixed to one end. The material being processed travels between the die and anvil where the cutting blades act on the material in one of a variety of ways, which will be more specifically described later.
The die cylinder performs the cutting operation while the anvil acts as the solid support surface against which the material is cut. The blades which are machined or “engraved” into the die cylinder compresses the web material against the anvil with sufficient force such that it cleaves the material at the blade edge, creating the desired shapes, slits, or perforations.
Complexity – Rotary presses range widely in complexity from the simplest single-station unit to the most elaborate and sophisticated engineering marvel capable of extreme levels of precision, control and flexibility. Cutting a basic shaped part from a single web of material may only require a one-station press with a minimum number of features. On the other end of the spectrum is the multi-station press capable of performing all required processing steps inline with one pass of the material(s) through the machine. Complex equipment can precisely control and adjust web tension, laminate two or more layers of material / adhesive / liner together, cut material from the top or bottom of the web, or strip / eject waste materials from the web.
Web width capacity – Rotary presses are made to handle materials of various widths and are typically specified by the maximum web width that can be processed. That is, a 16-inch press can handle material with a maximum width of 16 inches. A wider press, although more expensive than a comparably featured narrower press, would be more versatile based on the size of parts that could be produced. Some presses are equipped with the ability to adapt down to accommodate various smaller die widths.
Speed / volume capacity – For high-volume applications, the maximum press speed should be considered, as this factor will determine how rapidly a specific linear length of web can be processed. Converters calculate their part volume capacity using the press speed (feet per minute, for example), the number of parts per lineal foot, and the assumed production running time of the press.
Flexibility – Another key parameter is how easily the press can be set up to run another product. More flexible presses have greater adjustability in terms of web path, tension, speed, location of rollers and more. In general, the more flexible the press, the more easily your shop can accommodate the requirements to produce parts for your customer. Ease of adjustment and changeover with a minimum of tools is also a desirable press characteristic.
As expected with any equipment, higher speed, size capacity, flexibility and control drive higher total cost. Substantial capital expenditures require thorough analysis to assure that the chosen equipment can meet the production requirements while remaining within budget.
Interested in learning more? Read Understanding Rotary Cutting