New slitter rewinders for improved efficiency

13 February 2018



According to the latest market research figures from organisations like Research Corridor, the global slitting and rewinding sector continues to grow at a healthy pace worldwide – how and why is it thriving? Converting Today speaks with industry experts to learn more.


For a market that does not tend to see great changes in its technology or processes, the area of slitting and rewinding offers new methods that can greatly improve a converter’s capabilities and efficiency.

If you consider the industry-wide push for increased speed and volume, it is no surprise that operations and engineering staff are continuously striving to stay ahead of the curve. One of the most fundamental questions is: ‘How do we, as converters, increase productivity, minimise waste and increase profits on our slitter rewinders?’

Achieving ultimate efficiency

Randy Wolf, director of business development at Kampf Machinery, has wrestled with this question through his entire career, which spans a cool four decades.

“Though this might seem like a straightforward question with an equally straightforward answer, it is not actually that cut and dry,” he explains. “We must keep in mind that for years the slitting department has been looked upon as a loss centre when it comes to productivity and profitability.

“Today, there remains the mindset that whatever errors occur in the printing, coating and/or laminating departments, they will be corrected automatically in the slitting department. This is where the trouble begins – this train of thought is a production and profit killer. These departments – along with slitting – are all dependent upon one another to ensure a successful outcome. If one part fails, we all fail. As the slitter rewinder is generally the last piece of capital equipment that will touch materials before they get shipped to a customer, it is the final opportunity to ensure quality control, and that the operating process is running at maximum productivity and efficiency,” he adds.

One way for slitting and rewinding departments to advance is to embrace technology. Automation, for example, enables the slitter rewinder to become more operator-friendly, and reduces downtime and waste.

“Recent innovations have enhanced the slitter rewinder focus on pure productivity and profitability,” says Wolf. “This can be seen, for example, with the use of PLCs for PDFs or slit job-storage settings. These settings can include, but are not limited to, controlling and saving tensions, contact-roll pressures and overspeed settings, and slit-width patterns involving automatic knife-positioning systems. Finally, the job-storage feature means all operators can use the machine for the same purpose with the same degree of success and without any deviation in final quality.”

Improvements made with regard to the practicality of slitter rewinders have also led to improved downtime and increased efficiency. “The loading of master rolls, unloading of finished rewind rolls, and shaft handling are all areas that have caused headaches and potential injuries for converters for years,” explains Wolf. “Today’s machines, however, have solved these issues. Along with differential cantilevered rewind air shafts, there are now means to locate the rewind cores through laser core-positioning systems. This allows the operator to place the new rewind cores correctly onto the rewind shaft after unloading finished rolls. Again, this increases machine efficiency and reduces the time spent setting up new cores.”

Material-handling options: a necessity

Perhaps the most vital role of the slitter rewinder is its function as a material-handling converting system; the machine takes a blank canvas, creates its size, shape and width according to the desired specification of the customer, and all at high speeds.

With this complex combination of measurements, tools and materials, there is always opportunity for errors to occur. Wolf explains how an accurate material-handling option is less of a desire and more of a necessity in order to get the most out of a system.

“Included with your slitter rewinder should be material-handling features and options that will increase the productivity and profitability of the system,” he says. “You could have the fastest slitter rewinder available, but if you can’t get the finished rewind rolls off and reload the new cores onto the rewind shafts quickly, then the money you spent for that speed is lost. Material-handling options can include rewind-shaft roll pushers that automatically slide the finished rolls off the cantilevered rewind shafts onto an unloading unit that marries up to the rewind shafts. These units then automatically pivot away and turret over for the proper unloading height. Rewind-unloading units can even be designed to marry up to a conveyor or a robotic roll-handler that incorporates palletising and wrapping.”

In order to optimise performance and avoid delays, converters must thoroughly understand cycle times. As Wolf explains, the two distinct cycles – rewind and changeover – are critical for efficiency and often incorrectly calculated. The rewind cycle refers to the length of time required to remove finished rewind rolls and recore the rewind shafts for continuation of that specific job. Changeover time is just as critical and involves the changing of the slit-width patterns and materials themselves.

“Many converters fail to account for the time it takes to accomplish [changover],” Wolf says. “Here, again, the use of automation and technology, and similar job scheduling, play important roles in minimising job changeover cycle downtime. The PLC with PDF storage along with other options, such as automatic knife-positioning units, will minimise the time required to change over a slitter rewinder. Settings from when you last ran that job successfully are in the PDF and in conjunction with automatic knife positioning can reduce downtime from job changeovers by up to 75%.”

To answer the final part of the all-important question of how to optimise the efficiency and profits of slitter rewinders, Wolf believes that turrets are the key.

“If you currently run two or three standard duplex machines in your plant, the next logical progression would be to consider and understand the advantages of a turret slitter rewinder,” he says. “Turret designs have been available for many years, but recent advancements in automation, technology and material handling enable them to reach their full production potential. With automatic cut-off, automatic rewind core placement and linear-tracking contact rolls, rewind cycle times are now a fraction of that of a standard slitter rewinder. Such features as automatic roll-taping closure, coupled with a full range of custom material-handling systems, prove that turret slitter rewinders can increase productivity by 50–100% over a standard slitter rewinder.”

Changing the status quo

So what does this mean for converters? Wolf is clear that slitting and rewinding should no longer be thought of as a negative, nor as a loss centre. With the numerous system advancements available, developments in technology and automation, and effective operator training, modern converters can focus on increasing their productivity and profitability with ease.

“Technology and enhancements that we see occurring in this market are incredible, even for a market as old as paper-making is, there is still opportunity, innovation and engineering ingenuity to be seen,” says Dave Rumson, AIMCAL’s technical adviser. “The turret design, the positioning and accuracy of the knives for the slitting process, and the layout of the machines can all be constantly improved and reimagined to drive further quality, productivity and growth out of lines.”

Wolf’s sentiments are also shared by Joe Connelly, product manager of winding and slitting for Parkinson Technologies. “Overall, the challenges that today’s materials present to the converter can be overcome more easily by processing them on equipment that allows materials with slight variations to be processed at higher speeds into high-quality finished rolls in larger sizes, and with features that promote consistent web tracking and uniform finished-roll formation,” he says. “A uniform web path, created by maintaining a constant geometry within the machine, can lead to more predictable web-handling results.”

While today’s converters might question the productivity of their slitting and rewinding systems, when a problem occurs, what these experts show is that there is a solution, and that rather than a simple support tool, correct use of these machines can actually allow a converter to thrive, increasing productivity, efficiency and quality.

For many years, the loading and unloading of rolls has caused headaches – and injuries – for converters.


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