Rewind time

There is money to be saved when companies use slitting and rewinding technology effectively and efficiently. Michael Pappas, president of Catbridge Machinery, speaks to Converting Today about this often underutilised technology.

There are a number of developments in slitting and rewinding that are designed to improve quality and speed. Advancements in tension control and rewind shaft technologies ensure that static is reduced, and there is less waste due to the automated material feed, which quickly corrects any deviation. With precise taper-tension programmes, roll build can contain and maintain consistent tension. Safety is not a new concern, but the technology that improves it is constantly advancing. While there is an added cost to meet concerns about safety and operators' control, the benefits are justifiable.

Michael Pappas, president of Catbridge Machinery, says: "For turrets, new technologies at the start and end of roll rewinding improve quality. The latest automated turret designs have a tail tied to core processes that eliminates the problem of the roll being off-core at the first wrap. The new process also provides proper alignment at the last wrap, which eliminates the need to detach, realign and then resecure it. The savings in operator time and the improved appearance of the finished roll are significant."

Reducing inefficiency
Pappas says that problems beset most people using slitting and rewinding technology, but it is important to minimise them as far as possible. "Inefficiencies from downtime originate from four main sources: loading new parent or jumbo rolls, stopping and splicing for flags, knife-set-up changes and downtime between finished sets - when the machine stops to discharge rolls, place new cores and attach tails. Shaftless floor-pickup unwinds, autoknife-placement systems, autocore-loading and roll pushers address three of these inefficiencies."

For flags, however, a solution is to update the programmable logic controller (PLC). "Flag positions on a jumbo roll can be entered when the roll is loaded so that the machine slows down and then stops at a flag," Pappas says.

From a broader perspective, eliminating the need for flags has the most beneficial effect in the slitting department. This means fixing the problem at the source during a previous process such as printing or laminating. When this is not possible, some companies turn to the intermediate step of a roll editor. This is a machine specifically designed to deal with bad material, removing defects before the roll gets to the converting department. This adds a step to the process but studies in some plants have shown this approach ultimately saves time.

Gains in speed

For converters, alignment and tension control remain vital to slitting and rewinding. They are critical in three areas: the finished roll-build quality, edge quality and the speed at which material can run. Speed affects efficiency as the finished roll length increases. Modern slitters that are built well and easy to control should be able to run most materials at 2,500 to 2,800ft a minute. This will quickly add up on longer rolls. For example, if a 20,000ft finished roll runs at 1,500ft a minute, it would finish in about 14 minutes. The same roll at 2,500ft a minute would take approximately 8.5 minutes to run. That saves more than five minutes a set, every shift and every day. Even at shorter roll lengths the gains in speed must not be ignored.

Pappas says: "Aside from the issues of alignment and tension control, selecting the proper rewind-shaft technology and the proper controls for that technology are vital, especially for differential winding on centre winders. Gauge bands remain an issue. It's critical to choose the right shafts for the job. Should they be direct friction, indirect friction or even locked-core shafts? Also, the machine itself must be able to properly control the shafts to allow them to perform as required."

Like the rest of the converting sector, slitting and rewinding technology needs to be sustainable and reduce the waste of resources. Pappas says: "Because the converting department is the last step in a value-added process, sustainability and waste reduction will always have an impact. Rolls carry built-in value in the forms of raw material cost, energy, labour and overhead. A high percentage must go out the door as finished goods. The slitter has to run good rolls as consistently as possible. Proper tension control, alignment, system simplicity and repeatability for the operator help reduce waste and conserve materials and energy."

Modern slitter technology is leading to significant gains in throughput and waste reduction. Even saving a little bit of time when feeding through a roll properly is magnified when it applies to every run of every machine. A fast and robust slitter with modern tension and alignment control will cost more than a base, less expensive machine, but that expense will be worth the savings over the life of the machine. There is reduced waste, less throughput and diminished risk of injury to operators.

Slitting and rewinding news

TC Transcontinental Packaging uses a Titan SR800 slitter rewinder
Staff trust the Titan SR800. It is reliable and the team can consolidate the new machine into the existing Titan maintenance scheduling.
As with all slitting and rewinding processes, the risk to the final quality of the rewound package is the tension of the web. The Titan SR800 features a differential winding system and an S-wrap roller drive, which ensure constant rewind tension.
Jeff Lasley, general manager for TC Transcontinental Packaging, said: "The reliability and performance of our existing Titan fleet of slitter rewinders, plus the service and support we get from Atlas Converting, made the choice of the Titan SR800 easy for us. It allows us to meet our high expectations."

Universal Converting Equipment to exhibit at drupa 2016
Universal Converting Equipment's exhibition stand has been booked in response to interest in the Universal X6 Slitting Machine. In the last two years, the company has doubled manufacturing space, established a showroom and service centre in the US, and installed a range of CNC machining centres to manufacture their own mechanical parts.
At drupa, the company will be demonstrate a Universal X6 Slitter Rewinder, a Universal CCA Automatic core cutter and a hot-melt adhesive coating station.

Goebel IMS launches a two-drum slitter rewinder

Through a hydraulic system, the pressure of the independently driven rider roller can be adjusted to handle thin papers such as bible paper or teabag paper, packing paper and thick paperboard for cores. The slitter rewinder offers a wide range of features such as automatic knife positioning, automatic core loading, restarting and unloading systems, which can be customised. While guaranteeing excellent quality, the slitter rewinder allows a maximum production speed of up to 2,500m a minute. For short orders, the slitter rewinder features devices to speed up the in-feeding of the web into the machine, thus maximising productivity.