What's new with Cambridge?

A: Cambridge has taken the lead in single shaft winding for flexible packaging and other materials.

Patented technology and state-of-the-art designs and features allow us to offer extremely productive, precise, and ergonomically friendly machines. Also, our new slitting and rewinding lab will be fully functional in early February. Our lab will consist of two models, a 900 duplex and 324FP single shaft turret. The 900 duplex operates up to 2,800 fpm and can rewind to 32” maximum diameter, giving it a wide range of application possibilities including large diameter bottle labels. These machines will allow our customers to visit and run trials on different materials with shear, score or razor slitting.

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11. The Unwind and Rewind Tension Controls

The Unwind and Rewind Tension Controls Individual Top Riding Rolls

Being constantly aware of the obligation to provide equipment capable of satisfactorily winding at high speeds, the individual top riding roll for multiple roll slitting was developed as still another refinement to an already production proven and versatile piece of equipment

The development of the independent top riding roll permitted satisfactory high-speed winding of films and other off caliber materials because these rolls would positively maintain constant contact with the rewinding roll; thus, preventing air from entering between the layers of film.

The incoming web is guided precisely to and brought into contact with the rewinding roll so that side shift and weaving are eliminated, and individual rolls are not affected by off-gauge conditions of materials in adjacent rolls.

Individual top riding rolls are used to obtain straight, smooth sided rewound rolls, at high and low speed, when winding off-gauge, high slip - light tension "problem" materials.

Of all the progress which has been made about the slitting and rewinding of these materials, the development of the individual top riding roll for each individual rewound roll is probably the most outstanding engineering advance.

Efficient subsequent Operations. to a large extent, depend on the smooth edged, even density rolls of packaging materials which can be produced on the slitting-rewinding equipment.

Four major factors must be compensated for in order to produce the desired slit and rewound roll.

These factors are gauge variation, gauge bands.

slack zones and entrained surface air. which acts as a lubricant when an excessive amount is trapped and wound within the rewound roll.

Preventing Gauge Band Build-Up

In addition to eliminating air from between the layers of the rewound rolls, individual top riding rolls can be utilized to overcome the problems caused by the build-up of gauge bands.

For example, a roll with a gauge band build-up being wound without top riding rolls will develop tension concentration in the gauge band area resulting in uneven distribution of web tension across the full slit width.

Hence, for a 10 in. wide roll winding at one pound per inch of web width (10 lb. total) all 10 lb. will be concentrated at the gauge band.

Thus. if the gauge band is 2 in. wide, we will have a concentration of 5 lb. per inch instead of the desired 1 lb. This excess tension will cause distortion of most plastic films. causing further build-up of the gauge band. This in , turn causes wrinkles to form in the web coming into the roll.

Refer to Figure 111-12.

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When individual top riding rolls are used, this tension concentration is immediately redistributed to the full web width as the web wraps around the top riding roll.

Further, if the individual top riding roll is held parallel to the rewind mandrel, contact will be maintained only on the gauge.

Band, thus permitting air to be wound into the rewinding roll at all the other points.

The resulting roll will be tightly wound (without stretch) over the gauge band and soft throughout the remainder of the roll.

This roll can then be handled easily without telescoping or damage and will feed into the next machine operation without any problems.

Conclusion

Because top riding rolls are maintained in constant positive contact with the rewound rolls. the air which would be trapped between the layers of film is ironed out.

Top riding rolls are -sometimes referred to as "lay on rolls" or "ironing rolls". They also serve to distribute rewind tension evenly across the slit width. Because parallelism between the top riding roll and the rewind mandrel is maintained. uneven web tension due to build-up on the rewound roll is eliminated.

This action produces a wrinkle free rewound roll; and the rolls are

not affected by off-gauge material conditions in the adjacent rewinding roll.

Slitter Rewinder Overview

Cantilevered Slitters are machines with rewind shafts that are supported on one end. Deacro's cantilevered slitter rewinder machines are supported during the run-time for optimum performance.

When the rewind set is finished, shaft supports lower out of the way allowing finished rolls to be easily removed and new cores to be setup.

This allows operators to never handle heavy shafts or tooling. Cantilevered slitter rewinders are the most popular in the industry due to the reduced downtime between sets. This results in improved ergonomics, since they eliminate the requirement for operators to handle heavy shafts.

Common Adhesive Tape Winding Problems

In our world, we use tape-slitting machines that allow us to convert tape widths according to specification and the material itself. After the application of various coatings – which the backing material receives during the processing – the final coated product is delivered to the slitting machine in widths of 60 inches or more. In order to process these widths on a slitter, some tension must be applied to the material in order to keep it under control, and this tends to put a slight stretch in the tape. The tension and stretch will remain in the tape in the roll form. Or to think of it another way, the roll of tape has the same energy in it as a clock spring, but to a very minor extent.

How Much Stretch is Needed?

How much stretch the tape will receive during slitting will depend on many factors?

With the modern sophisticated slitting machine, every precaution is taken to keep the stretch to a minimum by automatic settings of the rolls that

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pull the tape through the slitter, and by the controlled speed of the machine. But not every machine is so sophisticated, and the settings of the machine tensions may be over-compensated, giving a very soft roll.

The settings can also be under-compensated, which results in a firm, tightly wound tape.

A Closer Look at Winding Challenges: Gapping, Gearing, and Telescoping

In nature, wherever there is a continual stress, objects will move to relieve that stress. And so, it is with the energy that has been built into the role of tape. It will want to dissipate that stress. For example, a soft-wound roll has its place, as in the case of cloth surgical tape with a soft adhesive. If it were tightly wound, that clock-spring gradually tightens with time, squeezing the soft adhesive into the cloth backing, resulting in tape that can’t be unwound.

However, a very soft wind in an industrial adhesive tape can be the cause of two problems. There is a still energy in that roll, and the roll gradually rebalances itself with time to dissipate that energy. This may take weeks or months. In the rebalancing process, gaps can begin to appear between the layers, and those gaps concentrate in very specific areas. So, we wind up with a roll problem that is known as

“gapping”.

There is a second problem, too. As the gradual movement begins to distort and misshape the roll so that it is no longer circular and can result in one or two bumps around the circumference. This is known as

“gearing”.

When the opposite occurs – when the roll is wound too tight – the stress in the roll results in a vector force at right angles, and the tape layers begin to slide over one another in the direction of the stress, the tape no longer remains flat, and eventually begins to take on a pyramid shape, known as “telescoping.”

Distortion … and How to Avoid It

The softer the adhesive, the more pronounced the distortion becomes. It is also encouraged by a high percentage of elongation in the backing or by more narrow widths of slit tape. Half-inch wide vinyl tape with a soft adhesive wound too tight can telescope in a minute or two. Only the tape-slitting department can overcome these problems, but the effect can be slowed down considerably by storing the tape at cool temperatures – in fact, the cooler the better. At colder temperatures, the adhesive firms up and restricts movement. Warmer temperatures will accelerate the deformations.

Salvage Rewinder Overview

Salvage rewinders allow operators to correct finished roll profiles, tensions, splice out defects and take edge trim. salvage rewinder lineup is even capable of basic slitting.

The high-performance reversible salvage rewinders that are ideal for inspection of printed webs and can reduce rewind times by 50-90%.

A reversible machine allows operators to maintain the print direction without running the roll more than once.

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12. Innovations Make Slitting/Rewinding Smarter

August 1, 2017

Flexible Packaging recently caught up with Randy Wolf, director of business development for Kampf Machinery Corp. USA, for a discussion on all things slitting/rewinding.

Q: What’s new in slitting/rewinding? Have you released anything new recently or have plans to release