Twenty years of NarrowWebTech and how the die-cutting sector has been transformed
Looking back over the last twenty years of the label industry, a whole host of major developments took place and a number of future trends were being introduced. A comment by NarrowWebTech editor Herbert Knott how the die-cutting sector, an essential part of each self-adhesive label production, has changed since 1998.
The most obvious change that has probably taken place is in the printing sector, with the switch from conventional printing technologies to digital printing. Labels were die-cut on linear, flat-bed die-cutters using steel rule dies, although the more modern presses were already using rotary die-cutting units that predominantly worked with engraved cutting cylinders.
Then, two companies, Kocher + Beck and Electro Optic, introduced major advances in die-cutting technology to the market. Developed in America Kocher + Beck brought as first company die-cutting system with magnetic cylinder and changeable flexible dies to Europe. It was a major step forward and shortened delivery times from 3 weeks to around a week, with costs also coming down substantially.
The second pioneer, Electro Optic, revolutionised die production worldwide with its ground breaking: fully automated CNC-sharpened dies. The resulting increase in quality over the hand-sharpened dies represented a quantum leap forward. The process developed by Electro Optic allowed die heights to be very precisely tailored to the die-cutting unit and it became possible to have two or three die line heights in one die for sandwich materials and for cross perforating. Worldwide, label producers continue to reap the benefits of this development.
Where do the current challenges lie?
Over the last twenty years label presses have increased in width for example from 180 mm to 520 mm (7” to 20.5”) to mention just two standard dimensions. The resulting higher demands on the die-cutting process have largely been met by the established die makers making constant quality improvements. In addition, adjustable anvil cylinders offer clear advantages when dealing with differing material thicknesses delivering time-savings and enhanced production reliability. Kocher + Beck, Rotometrics, Wink and Spilker offer various up to date technologies to meet the demands of the modern label production systems.
The trend to thinner and thinner label materials and carrier films currently represents the biggest challenge. In die-cutting, the face material is compressed by the cutting tool to such an extent that it breaks whilst the silicone layer and the carrier remains undamaged. As the face materials become thinner so it becomes increasingly more difficult to cut the label material, including the adhesive, but not the other layers.
The die-cutting process is quite complex involving label face stocks, carrier materials, magnetic cylinders, anvil cylinders some with substructures as well as intermediate support rollers. Then there is the general stability and stiffness of the die-cutting unit, which can generate vibration and oscillation. All of these components must be produced within certain tolerances.
However in day-to-day production not all the components are brand new which means that concentricity deviations of 10 µ are not uncommon in magnetic cylinders. Also anvil cylinders are often not round or are worn on one side which can alter the magnet cylinder nip by 0.480 mm often considerably more. PET and PP carriers of 23 µ, 18 µ and thinner are much less “forgiving” of such deviations than is the case with c. 35 µ to 50 µ carrier materials.
This challenge can only be mastered if the die-cutting unit is constantly maintained “as new” and the dies and magnetic cylinder produced with height tolerances of 2µ–which compares with the diameter of a human hair of around 30 µ.
And for the future?
Digital printing seen as a major new player has entered the fray and is capturing greater and greater market share. In many companies it is becoming an essential part of the label production, allowing highly fragmented and rush jobs to be handled without any problem. Laser cutting is also well suited to rush jobs as the change over from one job to the next involves no makeready time, no loss of material and no die costs. However, at present most converting lines are fitted with rotary die-cutting units using magnetic cylinders and dies.
Since laser cutting stations are still more expensive to purchase and maintain and are significantly slower and the quality of the die-cut result continues to be variable, there is currently no real alternative to rotary die-cutting. Spartanics and ALS are pursuing developments and SEI has now launched a four head system in order to increase speed.
It is all a question of cost. There is an interesting innovation from Cartes in which the delaminated web is lasered from the reverse side, stripped and the labels returned to the carrier by a suction tape. No scorching, no damaged silicone.
It’s absolutely clear: The trend is towards digital solutions. Whether in the printing or die-cutting sector, the industry will continue to benefit from competition between the various systems which is driving technology forward.
This review was published on the occasion of the 20th anniversary of our label magazine NarrowWebTech – more articles on this regard please find in this “20 years NarrowWebTech” overview!