If you’re in the market for a slitter/rewinder to convert flexible packaging materials, but aren’t sure what type of machine will best suit your needs, this article can help zero in on a system that meets your production objectives.
Let’s start with the basics. A slitter/rewinder is a machine used to convert a roll of material into several smaller rolls. Its purpose is to slit and rewind the incoming material into a form needed for the next manufacturing step, the requirements of which can be used to help you select the type and configuration of slitter/rewinder needed for the application. As is often the case, there is more than one type of machine that can be used. Although they all fundamentally perform the same converting function, selecting a machine with the right capabilities and features can save time and money in the long run.
Most flexographers already understand which attributes in a roll-to-roll printing system are important for producing high-quality rolls of printed film at the required production speeds. To ensure success, these machines must have superior printing technologies and the required accuracy in the transport rollers to carry the web through the print stations, maintain print registration and not distort or damage it in any way before it is wound into a master roll.
This value-added roll of flexible material is typically not yet in its final form and is converted later into a component of a package or product, or as the final package or product itself. The rolls of printed material must withstand the sometimes-rigorous handling that occurs when being transported to the next manufacturing step, and must be suitably formed to allow unwinding into the next process. These same requirements, along with others, exist for the slitter/rewinder to ensure this next intermediate converting step has the same level of success.
Slitter/Rewinder Physical Size Limitations
The first step in narrowing down a search is to define the complete range of physical properties of the materials you intend to process and your production requirements.
These specifications include the following:
- Types of materials
- The diameter, width, weight range and core sizes of the parent rolls
- The widths, diameters, weights and core sizes of the finished rolls
These preliminary specifications will effectively eliminate certain machine types, based on their size or weight limitations in handling the rolls you require.
Operating Speed Constraints
Another selection factor is the operating speed or machine throughput requirements to achieve your production objectives. As a general rule, offline converting machines typically operate at least 1.5 times the speed of the lines that supply the parent rolls, and can be as much as 2.5 times faster to achieve the production throughput required. For some materials, operating at extremely high speeds in order to keep up with production requirements may not be possible due to limitations in the material itself.
There are, however, other ways of improving the converting operation’s efficiency beside simply turning up the speed. Machines with increased levels of automation can really reduce the idle time of the machine by assisting with the material handling or slitter knife setup changes. Improving the ratio of run time to stoppage time with automated features can provide higher throughputs without requiring excessively high operating speeds—something worth considering if your budget allows.