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What you need for the perfect slitting process of a printed reel

FLEXOGRAPHIC PRINTING | Danilo Gatti, 13 October 2020

In the hygiene industry, it is crucial that the slitting of the printed reel is perfectly aligned with the printing machine if you want to achieve a perfectly centered image in each final reel. Moreover, you need a rewinder capable of eliminating the waste of material during reel change.

The slitting is usually performed by means of a slitter rewinder, which can be off-line, integrated directly into the printing machine or, if the printed product is to be laminated, be part of the lamination line itself. Nowadays, in the hygienic industry, two different cases can be considered:

  1. The converter works with printed reels already laminated
  2. The converter independently performs the lamination of the printed reels supplied 

In the first case, the supplier will have to transport the printed reel to the lamination line, where it will be laminated and slitted using the in-line slitting winder, while in the second case there will only be the need to slit the printed reel in the desired number of final reels. This can be done by using an off-line slitter rewinder or, better, by integrating the slitter rewinder with the printing machine. When it comes to this, A.Celli is unique, as we are the only supplier in the world that can offer both the flexo printing machine and the in-line slitter rewinder, thanks to the application of our know-how in winding and rewinding to the printing industry.

With this being said, let's take a look at the requirements needed to obtain a perfect reel slit and minimize material waste.

Center Turret winder versus Surface-driven winder

To rewind the printed and slitted material, thus obtaining the final reels ready to be sent to the converter, we can use center turret or surface-driven winders.

The center turret winder is characterized by a center-driven winding process: when the the desidered diameter of the reels is reached, the winder will rotate, positioning the new core in place of the reels just wound to allow both the winding of new reels and the unloading of the finished ones.

The problem that arises using this type of machine is that, from the beginning of this rotation to its end, the newly wound reels continue to drag the material during their repositioning. This leads to a loss of the correct tension of the material ensured by the dancer roller, and this will cause the reels to overlap each other. Result: this stretch of material, which is around 400 meters given that the center turret rewinder takes on average 35 to 40 seconds to perform the rotation, will have to be cut and discarded from the final reels before the packaging, storing or shipping to the converter.

This problem is solved with the use of a surface-driven winder like the A.Celli Nexus. With this solution the winding package is loaded against a driven drum equipped with a high grip coating, and the power necessary to rotate the package is transmitted from the outer surface of the drum itself. This will allow the elimination of the aforementioned waste of material resulting from the use of the center turret winder.

Automatic knives positioning system

In the hygienic industry there is often the need to print a pattern with a certain repeat length and the image centered in relation to each of the reels obtained with the slitting process. When no automation process is implemented, the knives of the slitting group must be manually positioned

In this case, If the printed reel must be slit into a certain number of smaller reels, each of the knives has to be positioned by hand with extreme precision to ensure the image is centered in each of these reels. Achieving this is very difficult: if the knives are poorly positioned even by one or two millimeters during the slitting, the image will not be centered in some of the reels, leading to a waste of material, time and, consequently, money

This without considering the neck-in error, which happens when the material is pulled, and thus shrinked, during processing. With manual operations, obviously, is extremely difficult to calculate how this error will affect the final result and therefore position the knives accordingly.

The A.Celli Slittomatic® system has been designed to solve these very problems. Our solution is an advanced system that will ensure a fast, accurate and completely automatic knives positioning. Moreover, thanks to our system, the knives positioning will be performed at the same time as the setup of the print job (colors registration, printing pressures etc…), which is impossible to do with manual operations.This will ultimately save you time and further reduce material waste, resulting in a high quality, defect-free product with no additional downtime.

If you would like to know more, contact us today for additional information on A.Celli solutions for flexo printing!

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