Heidelberg pushes offset IML opportunities

In-mold label (IML) is one of the fast­est-growing niche applications in the sheet-fed market, and Heidelberg has placed itself at the cutting edge with specially configured Speedmaster presses.

L&L was invited to see the Speedmaster XL 106 equipped for IML production at Heidelberger Druckmaschinen’s extensive production, showroom and R&D facilities in Wiesloch, located just outside the city of Heidelberg. This is the first IML demo press to incorporate Heidelberg’s own UV LED curing system, along with a technology package for handling IML label substrates without damage or static buildup.

The in-mold label market covers a diverse range of sectors including food (e.g. cheese, yoghurt, ice cream, margarine), industrial (paint, detergent, powders), household (storage containers, lunch boxes), cosmetics (creams, lotions), gardening (flower seeds, fertilizer), pet food, confectionary and toys. IML looks set to grow by a global average of 4.5 percent to 2020, when the market will be worth around 3.23bn USD.

The advantages of IML revolve around the integration of the label into the surface of the product, allowing the construction of strong and hygienic containers which can be easily be stacked without damage to the high quality print. A wide range of ‘look and feel’ options are available from different substrates, inks and coatings, and containers can be easily recycled and reused. Advances in molding technology now allow the label to be changed more quickly during production, creating a demand for shorter print runs.

Heidelberg sees these trends benefitting the offset process at the expense of both gravure and narrow web flexography.

‘With the increasing demand for shorter runs, we are seeing a strong movement from gravure to offset due to the far lower cost of offset plates compared to gravure cylinders,’ says Frank Steigleder, senior global account manager for labels in Heidelberg’s sheet-fed business unit. ‘Offset can more than match gravure quality and is more productive on short runs, particularly when used with rotary die-cutting.’

Technical challenge

Handling heat and static-sensitive 50 micron IML sheets at high speed is, technically, supremely challenging.

‘A high level of technical knowhow is necessary, raising the barriers to entry,’ says Steigleder. ‘Label converters must also be skilled in differentiating IML products with added value finishes like cold foil, special coatings, special colors and special effect inks.’ Other value-added techniques include perfecting, which allows printing on the reverse of IML films so the text shows up on the inside of clear-walled containers.

The demonstration Speedmaster XL106 IML press at Wiesloch is configured with six print units and coater, and fitted with the CutStar roll-to-sheet infeed from Heidelberg.

To assist in damage-free material handling and keeping static generation to a minimum, IML jobs typically run at 11,000sph rather than the XL 106’s top rated speed of 18,000sph. This ties in with a range of technologies developed by Heidelberg to handle IML substrates which the company calls its Foil and Thin Substrate packages.

Starting at the delivery end of the press, Heidelberg’s ‘dynamic sheet brake’ slows the IML sheet dramatically before it hits the delivery pile. The brake deccelarates the sheet in a controlled manner ensuring a perfect pile formation at high speeds.

At the infeed, the Speedmaster XL 106 for IML is fitted with the CutStar roll-to-sheet module from Heidelberg. The Thin Substrate Package adds features including cork covering for rollers, anti-static bars and ionized blast air to ensure a smooth transport of the IML film sheets.

At the point the sheets enter the press, there are further ionizing bars, ion blowers and rear edge blower with vent slots at the feed table.

Heidelberg says that compared to a sheet-fed infeed, CutStar reduces costs by around 10 percent and increases productivity by up to 15 percent.

Moving through the press, all parts of the sheet travel path are optimized for thin substrates and foils, with features such as wing grippers, printing nip blowers and ultrasonic sheet travel sensors in all printing/ coating units.

DryStar LED for IML

The Heidelberg Speedmaster XL 106 is configured with multiple drying options to handle the full range of inks and coatings currently on the market.

New to this press is Heidelberg`s in-house developed DryStar UV LED technology. Unlike in narrow web, where the LED arrays are almost touching the web, in sheet-fed presses

the arrays have to be placed at a greater distance (65-100mm) to avoid the sheet transport assemblies and get the necessary energy for curing to the sheet surface. The DryStar LED system uses Heidelberg`s unique double lens and focus technology to deliver a consistent 16W/cm² dose at the required 385nm wavelength. Heidelberg recommends its HD Saphira ink and coating consumables for IML applications.

DryStar UV LED brings clear benefits to in-mold label printing. Most important, heat is taken away from the curing process, with none of the IR radiation seen in classic UV lamp technology. The water-cooled LED arrays are instant on/off, leading to savings of up to 95 percent in power consumption during standby/ make-ready compared to standard arc lamps, and more up-time of the printing press.

An important energy saving feature is the DryStar LED auto format setting (AFS) which turns off unused LED zones in both lateral and press direction, meaning LEDs are only on when the sheet passes the LED bar. Heidelberg says this gives an additional energy saving of up to 40 percent for each sheet.

The LED bars can be integrated in the inter-deck or end-of-press position. They are interchangeable and can be combined with other dryer system like conventional dryers or arc lamp systems. Automated set-up of the LED system according to sheet size is fully integrated into the Prinect Press center.

Martin Zibold, product manager of Heidelberg`s sheet-fed DryStar LED team, says the technology is now proven with more than 380 print units and over 100 bar systems in the field worldwide.

For many IML applications migration is a potential issue. Zibold says Heidelberg has tested inks in combination with the DryStar LED system with both dry and wet migration tests. Concludes Zibold, ‘You have to have the right hardware and consumables in combination for low migration, and now this is coming together. It opens up a new chapter in sheet-fed offset with LED curing in the field of packaging and label printing – and especially for IML.’

IML automation

As noted earlier, IML is fast developing the requirement for shorter runs of labels – often multiple variants of a standard design. To achieve this without significant waste requires a high degree of automation. This is well demonstrated on the IML press at Wiesloch, enabling what Heidelberg calls ‘industrialized digital printing’ in a conventional press environment.

‘IML is a kind of business model where you need a certain knowhow to offer new products and applications. With this business innovation mindset you can generate additional value for the print buyer,’ explains Frank Steigleder. ‘At the same time operational excellence means you can cut costs, so a successful print shop needs a mixture of both.’

Overall press efficiency is measured by an index called Overall Equipment Effectiveness (OEE). The OEE index for an ‘ideal’ press would show 100 percent across time, speed and quality – so a press which is always printing, at maximum speed and only producing good sheets.

‘On average, todays print shops achieve an OEE of between 20-25 percent, so there is a lot of room for improvement,’ says Frank Steigleder. ‘In fact, we already have customers doing much better. One with a Speedmaster XL 106-5 is achieving a score of almost 60 percent on an average run length around 4,000 sheets, but this is the exception.’

The more shorter runs are produced, the harder it is to increase your OEE score. ‘If you are printing ten jobs a day, then high net speed is required; if ten jobs per shift, automated fast make-ready; but with ten jobs an hour, new solutions are required.’

Heidelberg calls this new solution Push to Stop, a ‘paradigm change’ where the process runs autonomously and is only interrupted to change jobs.

The core enabling technology for Push to Stop’s ‘navigated and autonomous printing’ is Heidelberg’s IntelliStart 2, integrated into the Prinect Press Center XL2.

Intellistart 2 calculates the fastest make-ready strategy, comparing the job currently in the press with the new job, and guides the operator with clear instructions through the individual steps.

Heidelberg offers various levels of plate automation for the Speedmaster XL 106, but for IML recommends AutoPlate Pro, which allows fully automated changing of all printing plates in a ‘staggered’ sequence so other activities – cleaning in particular – can be run in parallel.

Frank Steigleder explains: ‘AutoPlate Pro is the right way for labels and packaging printers rather than simultaneous eject and insert, because washing up between ink changes is their biggest make-ready factor.’

Heidelberg’s Hycolor Multidrive technology allows the inking unit to be driven separately from the main gear drive using a planetary gear system. This allows high speed wash-up of the inking unit to take place in parallel with blanket and impression cylinder wash, and with staggered plate change. The result is a full make-ready – including ink and plate change and pre-inking – in four minutes on a typical 6-color XL 106, a saving of more than 60 percent compared to earlier presses, where these processes took place sequentially.

During make-ready, CMYK and spot colors are monitored by the Inpress in-line spectral color and register measurement system integrated into IntelliStart 2, avoiding the need to stop the press to measure sheets off-line. Once quality parameters like delta E per ink are met, the press goes automatically into production.

In conclusion, it is clear that IML is a dynamic and fast-growing market sector, but with uniquely high barriers to entry – whatever print process is chosen – due to the demanding converting requirements of in-mold substrates and the need for static-free finished labels which work seamlessly with molding machines.

But the requirement to master complex technology also means that a good market position can be achieved, making IML a profitable niche in a sheet-fed sector dominated by commoditized wet glue labels. These opportunities are clearly perceived by Heidelberg, and its IML-configured Speedmaster XL106 provides all the tools necessary for entry into this tough but rewarding market.