Once UV, always UV
Expansion of UV flexo printing – print company Schulz in Baden-Baden installs an Smb FD5/1910 flexo press with IST UV technology
Over ten years ago UV flexo printing was on the brink of a major breakthrough. Since then UV technology has achieved this and has developed very successfully on presses in the narrow web sector such as roll labels and also on wide web applications such as printing on aluminium foils. In the area of packaging printing on central cylinder presses the big breakthrough of UV flexo is still awaited. Initial success has been achieved in specialist areas.This article discusses how UV flexo technology can be used successfully for printing profitably on packaging foils.
The printing company Schulz Flexodruck GmbH in Baden-Baden has been using a central cylinder flexo press with UV curing for seven years. In February 2002 the company invested in a new eight colour central cylinder press from Smb Sondermaschinenbau GmbH in Braunschweig. The company now has more than 50 printing stations and can print more than 110 million meters of packaging foil a year in one to eight colours. Designs of more than one colour are printed exclusively with UV flexo.
The company was founded in 1977 in Münzingen by Jürgen Schulz and now has around 70 employees and an annual turnover of around 8 million Euros. The current owner and managing director relocated the company to Sandweier near Baden-Baden in 1983. At the same time the company began to print on flexographic presses. The first presses were Metronic and BHS. In 1990 the company moved to new premises in Haueneberstein near Baden-Baden.
Gravure print quality at flexographic prices
Contract packaging companies are an important customer group for Schulz Flexodruck. These companies always demand extremely high quality products and Jürgen Schulz was determined to improve the print quality in order to meet these demands. This determination lead to the installation of a Uteco press for UV flexo printing in the mid-90s. If the only alternative had been foil flexo printing with solvent based inks then he would probably have chosen gravure printing. However, with UV flexo printing Jürgen Schulz could achieve the print quality required and at the same time avoid having to invest millions in a thermal oxidiser to remove the waste gases. Schulz is able to meet the "TA Luft" regulations (environmental regulations) without having to invest in expensive air purificatioin equipment.
Profitable short print runs
Dipl.Ing. Peter Darlapp, Sales and Applications Manager explains that the increase in the use of UV flexo in the seven years since the company started to use it is also the result of the specific benefits brought by UV technology (see the information box). The company‘s product range specialises in short and medium print runs of flexible packaging with very high quality requirements. A wide variety of different substrates is used from aluminium to polyamide, polyester, polypropylene etc to paper or fleece materials as well as the laminates widely used in this sector.
Peter Darlapp estimates that UV flexo is more cost-effective than conventional flexo printing for print runs up to around 80,000 meters. Schulz Flexodruck can even print competitively for print jobs of less than 1,000 meters.
Flexibility through in-house repro and stocks of substrates
In addition to being able to print short print runs of higher quality the Baden-Baden based print firm views the possibilities offered in terms of flexibility as a further key to the success of UV flexo printing. Rapid response to requests is particularly important for customers, who come mainly from the pharmaceutical, cosmetics and food packaging sectors. Schulz meets these demands partly by having in-house repro and photoengraving and partly by stocking a comprehensive range of substrates. This means that the company can, in very urgent cases, actually deliver a completed foil print job on the same day that it receives the print order.
Part of the printing is carried out by Schulz in cleanroom conditions. This facility is especially important for orders for the pharmaceutical sector. The company has two production areas which meet Class D cleanroom standards. (Ceanroom areas of Classes C and D are suitable for the less critical steps in the manufacture of sterile products. To meet the requirements for a Class C cleanroom a maximum of 3,500,000 particles per cubic metre of air is permitted with a diameter of 0.5µm and 20,000 particles with diameter up to 5µm. The new eight-colour central cylinder press has been installed in one of these cleanroom areas. The press is manufactured by the company Smb Sondermaschinenbau GmbH in Braunschweig and is fitted with a UV drying system supplied by IST METZ, which is based in Nürtingen.
Synergie of printing technology
The new press, a FD5/1910/UV, was installed in February 2002 at Schulz Flexodruck and is the flagship of the Smb product range. In the past the company has produced a total of 17 UV flexo presses with a central cylinder construction in the various press ranges, according to the Managing Director Dipl. Ing Sebastian Baumgart. The FD5 model, which has been installed once with this configuration, has a working width of 600mm and can operate at a maximum printing speed of 200m/min. The print speed depends greatly on what is being printed and is, in practice, around 110m/min. The maximum speed is, however, a secondary consideration for Schulz. When printing short and medium print runs, the make ready times are far more important.
The print units in the FD5 range are based on Fischer & Krecke technology. This is because Smb is part of the Beilefeld-based group Fischer Beteiligungsgesellschaft mbH, which also acquired Kochsiek GmbH at the beginning of 2002. The most important business areas for this group are flexo and roto gravure presses as well as specialised machines for the packaging industry. The group employs around 600 employees and has a turnover of approximately 140 million Euros.
Smb has 24 employees and specialises in producing narrow web speciality flexo presses and already has several references in the area of UV flexo presses. For several years these presses have been printing on tubing which is used for sausage skin. Sebastian Baumgart predicts that the development of such niche markets will lead to increased demand for UV technology in the area of foil printing in the future.
Specific press design for UV requirements
The FD5 press installed in Baden-Baden has been specially equipped for use with UV printing. For example, in order to be able to guarantee the exact diameter of the counter pressure cylinders during the print run, the actual operating temperature must be taken into consideration during manufacture. The water cooled cylinders are therefore manufactured at a temperature of 30o C which is the main operating temperature during the printing process.
The BLK® system has a maximum output of 84kW. The system is designed so that the tempering of the central counter-cylinder removes at least 15% of this energy as surplus heat. Rolf Müller of IST METZ explains that this is significant for the production in several respects. It guarantees constant conditions and therefore a reproducible print quality and allows printing on narrower. If foils which are narrower than the maximum width of 600mm are to be processed, the warm air will still be removed effectively from the whole width of the web path.
The FD5 in Baden-Baden is fitted with a BLK® system, which has UV lamps with an output of 200W/cm. The stepless output controls mean that the output can be adjusted between 100 – 200W/cm. For the first seven print units the UV units are installed directly after the print station. After the eigth print unit there is an extended web path of around 5m before the final curing. This leads to considerably higher gloss levels when varnishing.
Lower ink costs in the future
Schulz Flexodruck uses both cationic and radical ink systems. Cationic systems, which represent around 20% of production, are always chosen if low odour or good adhesion on difficult substrates are required.
Jürgen Schulz complains that ink costs are still too high. He hopes for an increase in the use of UV flexo so that increase in consumption would lead to price reductions. This is already happening in the market segment for sausage packaging sleeves. The growing acceptance of UV technology within print companies has already brought new ink suppliers onto the market. As a result the prices for UV inks for the sausage packaging sector have begun to fall.
More and more customers are discovering the quality of UV printing
Jürgen Schulz believes that use of UV flexo will really increase when the end customers recognise the quality benefits of UV printing. He has always found that once customers have experienced the quality of UV printing on foil packaging they are very reluctant to stop using it. The possibilities particularly in the area of fine halftone printing mean that UV flexo produces results which are far closer in quality to gravure printing than is possible with the conventional alternatives offered by solvent-based inks. Furthermore, additional varnishing is often not necesary as UV inks usually produce the required gloss levels and physical characteristics and fastness.
In addition to the benefits in terms of quality UV flexo also offers a higher reproducibility than solvent-based systems. One important requirement for using UV is the standardisation of anilox rollers, inks, etc., at least internally. For this reason also customers are increasingly shifting print jobs to UV flexo. Jürgen Schulz realises that customers, who up to now have used roto gravure for their packaging printing, are now showing increased interest in UV. Economic considerations are the decisive factors in this decision. Given the individual nature of the orders printed by Schulz and the predominance of narrow web presses in the company, the pre-print costs for UV flexo work turn out to be very favourable. In many cases the cost of plates and repro are a third of those of a gravure cylinder.
Background information
Quality, safety, economic and environmental benefits of UV
UV flexo users, suppliers of UV systems as well as UV ink and press manufacturers describe various advantages of using UV flexo compared to conventional printing with solvent-based inks. Some of these advantages are discussed below:
UV flexo produces brilliant colours, as the inks are solvent-free and are composed of 100% ink solids. Depending on the choice of pigment they also produce truer colours and have greater physical and chemical resistance. As there is no evaporation of solvents the ink constancy is also better. The dot gain is considerably lower in UV flexo and the varnishes, depending on ink, substrate and thickness of the layers, generally have a higher gloss. One important advantage of UV flexo is that it is possible to print on different substrates using one and the same range of inks. It is recommended that trials are carried out first with radical ink systems as adhesion is reduced on a few foils.
Looking at the print process as a whole UV flexo can result in cost savings despite higher ink costs because of the shorter make ready times and a higher degree of standardisation. Stable parameters in repro, for ink thickness and viscosity lead to a reduction in start-up waste and less ink wastage. Furthermore, downtime is reduced as specific cleaning times are not necessary. For example, cleaning is not necessary at the end of the shift as UV inks do not dry on the press. As long as printing continues with the same ink then no cleaning is required. As the inks do not dry on the plates there is no filling in of the dots which means that the printing plates do not have to be cleaned manually. As there is less load on the printing plates fewer plates are needed, particularly for repeat print runs.
UV flexo printing allows immediate further processing of products such as folding cartons or packaging for liquids. The possibility of having in-line processing, eg inline punching, increases productivity.
As UV flexo printing does not require any investment in air purification systems considerable cost-savings are possible, particularly with investment for expansion. This is particularly true if suitable technical equipment is not already on site. Another important consideration is that there is no need for explosion protection for the presses, buildings and ink warehouses. This results in lower insurance and building costs. The ink stocks required are also reduced because the same ink ranges are used on different substrates.
UV systems are solvent-free, which is an important advantage in terms of safety as there is no risk of explosion in the production area. The strict regulations and guidelines of the regulatory bodies ensure the safe use of UV technology and have been successfully implemented for many years. These regulations also ensure that the packaging for pharmaceutical and food packaging is safe. From an environmental point of view it is also beneficial that there are no solvents in UV printing as there are no exhaust emissions and the “TA-Luft“ requirements (environmental regulations) can easily be met.
Further Information
Information about this special UV application please see flexo wide web. For information about the UV subject area please see homepage.
