At first glance, the slitting stage of a production line seems simple enough: Take a large roll, then slice and spin it into several narrower rolls. Then, for maximum productivity, crank up the speed, right?
Well, not quite. Productivity in slitting/rewinding is a trifecta of increased machine speeds, larger capacities and minimized set-up/changeover times. After all, what good is a machine that zips through thousands of feet of film per minute but takes eons to prep for the next job? Suppliers recognize this balancing act and have developed several features to help converters keep slitters humming.
Set auto pilot for efficiencyTurret rewinders feature a rotating shaft system using two sets of rewind shafts, allowing the slitter to rewind on one shaft while the operator removes finished rolls and sets up new cores on the second shaft. Naturally, this technology significantly benefitted both the efficiency of slitters and the converting industry. However, even as recently as 10 years ago, neither turrets nor automation were a clean match for every converter remembers Keith Hamilton, sales manager at Deacro.
“It was pretty much always the big guys who were running the same job, the huge volume-type jobs,” says Hamilton. “Now turrets are more common because the quick set-up features mean you don’t have as much downtime,” an advantage that has universal appeal.
For short-run jobs, which is more typical for converters, Deacro systems have quick set-up features like automatic positioning of the knives and the cores, differential air shafts which eliminate any tooling of the rewind, and automatic positioning of web guide sensors.
Hamilton explains that on older slitters, it wasn’t unusual to spend an hour setting up a machine. “On newer machines, with the right technology, it’s not uncommon to have it done in a few minutes. Machines can be cranked up to high speeds, but you get a more dramatic impact by keeping that machine running. If you just eliminate the downtime or the set-up time, the throughput can be staggering.”
Keeping tabs on material useOne bottleneck in a slitting operation often occurs when ending one set of rolls and preparing the next. Parsippany, N.J.-based Catbridge addresses this production challenge through two developments, a tabber and roll enveloper.
“The tabber pre-tapes materials to cores at roll wind start, and supplies a ‘tail-tie’ for finished rolls,” explains Steve Crossett, sales at Catbridge. The tabber applies tape across the full web width, cuts it off at a length to match the material width and then applies it to the web. The system then draws the “tabbed” web through the slitting knives and stops it at the precise point where the turret’s cut-off knife cuts in the middle of the tabbing material. The leading edge of the tape serves as the tail-tie for finished rolls while the trailing edge secures the web to new cores.
“Removing these two tasks from the operator improves cycle time, assures consistent quality starts and a uniform appearance on roll finishes,” says Crossett.
The company’s enveloper likewise prevents waste, increases cycle times and improves a roll's performance. But it also eliminates adhesive material and the possibility of mirroring a fold-over ridge through an entire roll. This system includes a traversing shear or razor cut-off knife and an “enveloping” system that positions a precise amount of material around the new core (or the shaft in coreless operations).
“The elimination of tape or glue on a core offers operator time and material savings and a customer can use all of the product on a roll,” says Crossett.
Interface makes slitting a snapIntuitive interfaces capable of recalling job parameters have influenced flexible packaging for some time now and slitting operations are no exception. Comexi uses such an operator friendly computer in all its latest slitters, and as Randy Wolf, director of business development, points out, computers with job storage files guarantee reliable production.
“One of the biggest challenges the converting industry faces is integrating different operators and substrates into the process,” says Wolf. “The solution is through technology that is simple to use. Having the ability to store all of the important job settings in the computer ensures that all of the operators are on the same path to success.”
The computer plays a key role in Comexi’s Automatic Knife Setting System (AKSS) as well as splice tables, tension control systems and customized material handling devices.
Flexible packaging converters welcome any opportunity to maximize productivity. The latest developments in slitter rewinders, including automated positioning technology or intuitive interfaces, slim down your changeover and can beef up your productivity and profits.
Web exclusive: Streamlining: Integration and automationAlbert Einstein once remarked, “Life is like riding a bicycle. To keep your balance you must keep moving.” Like bicycling, slitting/rewinding keeps a good balance through a combination of production speeds, fast changeover and accurate results. To that end, Rotoflex’s new G3 URC controller maintains this balance and provides the operator with seamless integration of all rewinder functions.
“Operators can view all machine controls, counters and even 100% inspection on a single screen,” says Ken Daming, Rotoflex business unit manager. “Another update includes implementation of a combination razor/shear knife slitter cartridge, which accommodates a much faster changeover from one mode of slitting to another.” Another enhancement to the Rotoflex line of slitter/rewinders includes web inspection in both horizontal and vertical directions, depending on customer preference and requirement.
Daming explains that a common feature to the Rotoflex VSI/VLI line of rewinders is the central location of each machine’s controls and operations. All from one position, the operator is able to watch the slitting, inspect the product and unload the rewind coreholder, streamlining the converting process.
Such efficiency is also at the heart of Tidland’s e-Knifeholder, an electric shear-slitting knifeholder that allows an operator to electronically set side force and overlap before the device automatically calibrates and positions the blade.
“In general, we’re seeing a need to free up the operator from intervening with a machine,” says Peter Wood, slitting product manager for Tidland Corp. “We’ve simplified the most common point of interaction by creating an electronic knifeholder that is easy to use and intuitive, making the operator’s life easier and the slitter more productive.”
Wood explains the company’s knifeholders ensure operators are cross-trained throughout a plant because the settings are similar throughout the product line. A move from the Tidland’s Performance Series Knifeholder to the e-Knifeholder can improve efficiencies without the intimidation of learning new technology. In fact, an operator canbe trained in 90 seconds.
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