Flat bed die-cutting – for corrugated and carton
All the converters’ hard work in carefully laying down ink onto board can be wasted if the job is badly die-cut. So what should you consider when looking to invest in new die- cutting capacity.
There is nothing more fundamental to quality die-cutting of board than the accuracy of the registration between print, and in the case of cartons, the foil, cutting, creasing and embossing. Physical lays are unable to adapt to any variation in the position of the print, or to cope with the varying overlap of litho- laminated sheets, and this is why dynamic register systems have become a very important weapon in the box makers’ arsenal. Dynamic systems use high speed video cameras to identify printed marks on the sheet and move it on-the-fly so that the cutting and creasing of the sheet is in perfect registration with the print. The latest systems can also read from underneath the sheet, for litho-laminated and corrugated applications, and can read print on metalized or synthetic materials.
Initially, dynamic register systems were developed specifically to enable die-cutting presses to run faster; the old physical lays having restricted run speeds. Armed with powerful dynamic register systems, today’s die- cutters can now exceed this. However, as ‘Just In Time’ manufacture brings shorter run lengths across the industry, make-ready times have become as important as running speeds. At drupa 2012 there were a number of die-cutter developments on show geared to improving Overall Equipment Efficiency (OEE), and in particular to delivering faster make-readies.
Equally important to achieving high OEE is maximising the available production time – something which requires not just physical reliability but also means keeping stops in production under control. Here, systems which feed information back to the feeder, so that it can adjust pallet positioning or sheet arrival timing to compensate for variations in the pile, make a significant difference to the number of stops suffered, in some machines cutting them to less than a quarter of those suffered by ‘conventional’ machines.
Bringing many tons of pressure to bear on the sheet creates huge stresses on the die-cutting equipment delivering it and, if not distributed correctly, can lead to poor cutting quality
and eventually to machine failure. Some die-cutters are designed to balance out these pressures, resulting in higher accuracy and less patching up. Equally important is how the sheet travels through the machine. Because flat bed die-cutting is a stop and start process, the smoother the sheet transport can be, the less disturbance is introduced into the process. Cam driven gripper bars lower the stress on each sheet, meaning that fewer nicks are needed, better quality can be achieved and sheets can be run at higher speeds.
Of course, price is important, but total cost of ownership is even more important. While a low purchase price always looks attractive, hidden costs such as a failure to meet performance criteria mean extra costs every day. So it’s worth exploring whether the running speeds and make-ready times the equipment manufacturer quotes are being achieved by other users and whether they will stand by them for your particular work-mix. Depreciation is another hidden cost, with some machines starting to free fall in value as soon as they are installed, while others maintain their value well.
One particular cost worth highlighting is that of premature tool wear. With good tools and correct patching up, a good quality die-cutter should achieve and maintain ‘kiss-cut’ die- cutting without difficulty. On the other hand, some machines will require extra pressure and constant re-patching to maintain cutting and creasing quality. This extra pressure results in the die-cutting tools needing re-knifing or re- making sooner than need be – and also leads to premature quality problems such as ‘angel hair’. Because tooling accounts for an element of the cost of any job, leading equipment
Author: Dan Brunton, Publisher
manufacturers have begun to introduce ways to minimise the wear and tear on tools, such as systems for taking them instantly off pressure when no sheet is present.
In today’s high pressure manufacturing environments, being able to track how each of your pieces of equipment is performing – both in terms of production and availability – is vital. Some manufacturers now offer smartphone and tablet apps which allow supervisors and managers to see the current and historical performance of their equipment, wherever they happen to be in the world, as long as they have an Internet connection.
Does your potential supplier have after sales support facilities – in particular do they have them in your country? If you suffer a breakdown, will it take days, or even weeks, to get an engineer or parts to you? And most important of all, will the supplier still be around in two, five or ten years’ time to fix a problem? Also worth exploring is the level of customised support that your chosen manufacturer can supply. Do they have a track record of supplying tailor made solutions for particular applications – maybe a very bespoke job you handle – and are they willing to help you assess if and how you could die- cut that job you are bidding for?
Checking out your potential supplier’s attitude to ongoing support can pay dividends – after all, there’s nothing worse than finding out your machine can’t be upgraded, even if it’s relatively new.
A good supplier will support their equipment for many years with retro-fits that can maximise performance, improve product quality, or deliver new functionality.
10 - 12 March 2015 • Munich Trade Fair Centre, Germany
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Branchen-News | Industry News CCE
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