From the finishing to production department – A review of twenty-years of label converting

Print image-based web control: FE 52 colour line from Erhard+Leimer (Source: E+L)

For 20 years NarrowWebTech has accompanied the label printing and narrow web converting industries through interesting and sometimes quite fast times of technical developments and drastic market changes. During this time, the move from finishing to production department has occurred.

Written by Herbert Knott

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A great deal has changed in the printing industry since 1998. Around twenty or twenty five years ago digital printing simply did not have a presence in the label sector, whereas now it seems as if no label printer can get by without this technology. Has there been a similar fundamental change in web finishing, downstream from printing?

Changes in jargon would suggest this to be so. Twenty years ago the final stages in label production were handled by the “finishing shop”, whereas now the label runs through the converting division. But it is not just jargon. There has also been a massive change in terms of what actually goes on. Monitoring of the printed product, cutting the production reel into individual reels, rewinding cut-off lengths based on quantities required by the customer in a specified direction on to the right reel cores for the dispensing machine, sealing with a neutral label and packaging.

[Editorial comment: this article was published on the occasion of the 20th anniversary of NarrowWebTech – more articles find in our extensive special edition “20 years NarrowWebTech – A history of label printing”]

Where to start?

To begin with the correct cut-off lengths. Once upon a time a pocket calculator was used to convert the desired quantity of labels into linear metres because the counter on the reel cutter used a rotating wheel to measure the web and displayed its readings in metres. It was not always possible to avoid discrepancies through labels that were short or long or more tightly or loosely spaced.

Then, as now, the webs were slit into individual reels by a creasing blade acting against a roller, by a sheer cutter or by razor blades. In those days the spacings and, therefore, the individual reel widths were measured with a ruler and in some cases spacers were used. The winding hardness of the final reels was simply determined manually by feel, and sometimes reels would be over-wound with the adhesive squeezed out.

Dolordyne turns any converting system into a hybrid CMYK-W press (Sources: H. Knott)

Monitoring is an issue

“The customer is monitoring from here” — was the call to take care that features included for the customer were featured on prominently displayed posters in a factory’s final process department. This is still the case but the possibilities for evaluating quality efficiently have changed fundamentally over the past 20 years. Once, it was the eye that judged every aspect of a product to make the call between success and failure.

Missing labels, stripping waste, poor print or print to cut register, ink splashes, colour variations, hickies on the printed image or in the text, the filling in of text elements or missing individual characters were all aspects of quality that needed to be checked. And, in some cases, this involved foreign language texts, quite possibly in Asian or Arabic scripts, where even the slightest deviation could have dire consequences. The only aid that used to be available was a stroboscope, which, by synchronising its frequency to the speed of the web, was able to make a fast running web appear static.

Advertisements in NarrowWebTech proclaimed stroboscope-based monitoring and cutting systems as great advances and a look at some of the technical articles from the time confirms this. However, only the code readers for labels in the pharmaceutical and subsequently for EAN codes, represented real technical aids.

Improvement is a constant requirement

Time pressure and the drive for efficient working — and not just on the actual press — have also brought advances to the converting process. Examples, include, quick action clamping systems for slitting knives, which can be precisely adjusted in advance and then mounted in one action on the machine, reel winders with potentiometers for determining the right winding hardness, turret systems for flying reel changes and photocells to control winding so that the number of labels is precisely correct.

The first step towards the converting department was the move by some reel slitter manufacturers to integrate rotary die-cutters. This allowed blank labels to be produced cost effectively but also, although for a long time there was no thought of doing so, webs of printed labels could be die cut. But who needed to do that?

ABG shows its Digicon 3 (Source: Herbert Knott)

Digital printing entered the market
At this point digital printing entered the scene. An array of standalone units offered offline finishing that went well beyond the traditional tasks undertaken by simple slit and rewind machines. Digital presses did not offer finishing steps such as flexo spot coating, blocking, laminating or screen printing and only a few were fitted with die-cutting units.

In addition, due to the speed of a converting system, it was possible to handle the output of two or even three digital presses with one such machine.

RFID labels and booklet labels are also finished on converting systems without slowing down the printing process too much. The same is true for inmould labels on the reel.

It required some effort to control the web and print to cut register. This was achieved through servo motors plus web control systems that worked from printed elements rather than taking the web edge as their reference point for positioning the web correctly transversely.

[Editorial comment: this article was published on the occasion of the 20th anniversary of NarrowWebTech – more articles find in our extensive special edition “20 years NarrowWebTech – A history of label printing”]

From visual inspection to Big Brother

The pressure for quality from print customers in the food and the care & beauty industries in particular has grown massively over the last 20 years. The look of such brands on TV needs to be a close visual match with the packaging and the label, placing considerable demands on printing and quality control.

A printers’ eye is now no longer good enough. Camera systems on converting lines offer much higher performance, are “unerring” and never tire. Electronic proofing compares the original design or a scanned proof with the production sample or a camera image. 2D and line cameras offer two different systems for differing requirements.

2D cameras check the printed results for a label or area of the printed web against a reference at defined time intervals. However, only a part of the printed web is checked simultaneously. Line cameras, on the other hand, constantly check the entire web. The highest level of monitoring capabilities is offered by inline spectral colour measurement.

Rotocontrol is also well represented in the market with its DT 440 line (Source: Herbert Knott)

Go beyond the parameters

The latest generation of inspection devices go beyond the parameters that were previously checked — print and print to cut register, stripping, the legibility of codes of all kinds, as well the integrity of the print and the absence of faults (ink splashes, hickies, etc.) — to assess the correct colour rendering of the printed result compared with the original. Until now this has definitely been something for which a trained printer has been responsible. In addition, the results of these checks can be fed back in order to optimise the data processing for the following print jobs.

When it makes sense to carry out such checks on the press in order to avoid wastage, data logs are forwarded electronically to the downstream converting department so that detected errors and deviations can be removed automatically.

Workflow management

Modern systems handle the integration of a converting system into the workflow. Job-related automated make ready steps are controlled by MIS systems or by the use of imprinted codes. This allows the positioning of the die-cutting / blocking station / flexo spot coating and the adjustment of the knives in the reel cutter to be automated. The reel cutter prints an EAN code on the sealing label that provides details of the product name, production batch, reel number and label quantity. All of this massively boosts the efficiency of converting systems as we move towards the industry of the future.

Everything is now working so well with flexo coating units for full surface or spot coating, foil, hot or cold blocking and laminators – which means that “conventional printing” still has a place. These comprehensive converting capabilities offer the opportunity for the last department of the production line to handle all these converting steps rather than to install expensive special units on flexo or offset presses.

Mutual benefits rapidly developing

Digital presses were the catalysts for equipping converting systems with an array of finishing units. Now, however, the reverse is happening. Digital imprinting systems are increasingly to be found on converting systems. This allows individual details such as batch numbers, EAN codes or QR codes, sequential number or action codes to be added to conventionally printed labels.

For sure, it is able to go the whole way and insert a digital printing unit such as a Colordyne into the converting system, ending up with a full-blown press — but the advantage of the higher output of the converting system is lost.

Summary

The development of the converting department into a key component for label production is well underway and its pace has been accelerated by the increasing number of digital presses. All that is holding back the development of full capability converting machines are the rapid advances in functional inks in the area of inkjet printing. It is already possible to deliver foil blocking, structural coatings, reactive inks and braille print by installing a printbar and a laminator.

The development of the finishing shop into the key production unit of a label printer has had many and varied consequences. I am keen that NarrowWebTech should continue to keep its finger on the pulse over the next 20 years.

Editorial comment: More articles regarding the 20th anniversary of Narrow WebTech and thus, twenty years of label printing, please find in our overview of “20 years NarrowWebTech” with all published articles – click here!

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