What shape cell?
Published: 20 March 2013 | No comments yet
Manufacturers of anilox rollers and sleeves are still not agreed on the best approach to meet the demands of the increasingly sophisticated flexo printing process. The introduction of high definition printing challenged the standard cell engraving and a number of solutions have been launched subsequently. By Neel Madsen.
The cell geometry of anilox rollers hascome a long way in recent years with various solutions offered to the eternalproblem of ensuring even and consistent ink release onto the printing plate. High definition flexo printing puts even tougher demands on manufacturers as dot dipping, smoothink release and consistent print results even at high speeds, to name but a few issues, has to be resolved satisfactorily.
Georg Selders (right), sales director, Apex Europe, with customers
Is nano the answer?
Anilox Laser Technology Ltd has introduced a new engraving known as Nano. This new cell structure has been developed to give maximum cell volume release whilst keeping the cell depth at a minimum for optimum ink evacuation. It promises to allow the printer the ability to produce a wide range of work using a high line count anilox specification, increasing print definition while reducing the range of anilox screens needed. Since its launch last year, the company has run a number of tests that have shown a range of significant improvements in several market sectors, including 100% increased lay down compared to standard 60° formats, sharper print results, improved print consistency on long runs, greatly improved resistance to cell contamination, and reduced cleaning times and anilox inventory.
Anthony Jewell, managing director, said, ‘The flexo print process has made significant steps over the last few years, and now with HD technology in plate production, it is even more important to control the anilox transfer. Nano can optimise the ink transfer whilst maintaining good print definition over a wide range of work types, all from one anilox specification.’ The new product will be offered in the corrugated industry exclusively through Print-Tech Solutions Ltd. Steve Turner, owner, commented, ‘We have worked closely with ALT for some time, so the development of Nano is extremely exciting for us and our customers, especially in the corrugated post print sectors where expectations of print quality are increasing, but paper quality is creating issues. We are extremely confident that it can offer the corrugated industry a solution to a growing problem, something that has not been available in the past.’ Nano anilox technology is the latest introduction into ALT’s catalogue of cell engravings. It also has the Rainbow cell range, which is already extensively used within all parts of the industry, the Ani-FLOW for efficient varnish and white base laydown and the Ani-PLUS can be used for high volume transfer of inks in all print applications including HD flexo. Plans are also underway to install a second fibre optic laser machine later this year. ‘Our previous experiences showed us that there was a new way to look at the application of the anilox roller or sleeve, and we can see the importance to the printer to have the minimum amount of downtime on press, especially in the current economic climate. This was the driver to develop our new technology,’ concluded Mr Jewell.
ALT’s latest engraving is the Nano
Or is a revolution needed?
Apex Group of Companies initiated and coordinated a new project aimed at meeting the demands from the flexographic printing industry, which it lists as covering a wide colour spectrum with CMYK alone, printing at ever higher speeds, protecting the environment through lower emissions, reducing costs and saving time as well as ensuring that every job produces predictable results that are of a consistently high standard and reproducible on a daily basis throughout a print run. Known as the ‘Flexo (R)Evolution’ project, this is an open engineering platform for suppliers and printers which brings standardisation and control to the process by finding the optimum combination of components, including Apex’s own GTT (Genetic Transfer Technology). Featuring open ink channels engraved in a slalom pattern instead of the traditional cell structure, the GTT anilox rollers are available in a range of different profile types covering the entire range of different industries, ie flexible packaging, corrugated board, labels, offset printing, varnishing and coating applications. In flexible packaging, especially in the high quality range, the GTT S and XS are for printing fine lines and screens. They are suitable for plates with up to 100 l/cm, and very fine dots can be reproduced as dot gain can be kept under control more effectively. More constant inking allows a stable printing process, especially with four colour printing, where GTT makes it possible to cover a wide colour spectrum. ‘The GTT XS and S give us two types of roller that enable us to satisfy all the requirements of high quality printing in the flexible packaging industry. With its optimum harmonisation of the most up-to-date technologies, the XS is used for plates with high ink transfer or flat top dots with very fine screens, while the S allows us to bridge the gap between high quality and conventional jobs involving standard technologies and round dots, even for very fine screens,’ said Georg Selders, sales director, Apex Europe. The company is quick to point out that the technology is for both conventional printing and high quality printing. Nick Harvey, technical printing expert at Apex, said, ‘It is important to us to deal with both aspects because, even if flexographic printing is clearly moving in the direction of high quality, it must still be possible to print conventional jobs reliably and reproducibly in future!’
The HD is flowing
Pamarco Global Graphics first launched its EFlo cell structure for the corrugated, flexible packaging and labels industries in 2009. In early 2012, this was extended with the addition of a high definition engraving, the EFlo-HD, which was subsequently HD Flexo certified by Esko. This cell structure is achieved using bitmap technology and developed for HD Flexo printing. Pamarco says it is the most consistent laser engraved cell structure on the market today. The company achieved several of its strategic milestones in 2012. Technological advances led the way with the installation of state of the art 500W multi beam laser engraving systems now completed in all its anilox plants. In addition the UK facility in Warrington successfully completed a major upgrade to its ceramic coating operations and implemented formal ISO 9001:2008 Quality Certification. Offering the latest technological innovations in anilox, allied with guaranteed quality supplied from the most efficient manufacturing operations are a core part of the company’s ‘customer satisfaction strategy’. In the corrugated sector, the EFlo extended cell engraving is increasingly being adopted as a standard, whether for simple codes, large block solids, or the finest process or combination work. In the flexible packaging sector, the company has completed three major press installations for UK-basedgroups utilising the latest EFlo-HD to deliver quality improvements for global brands at the same time as reducing anilox inventories. The EFlo-HD is now in its third generation and capitalises on the latest laser developments allowing customisation of power delivery using bitmap files. This allows for the shallowest, flat-bottomed cells, giving proven benefits in ink delivery as well as long term clean-running operation. In the label sector, Pamarco has continued to develop its position with Nilpeter, working together both as an OEM supply partner and sharing distribution for Pamarco anilox sleeve, roller and hand proofer products in an increasing number of territories.
Harper produced this totem design engraving to illustrate its capabilities
Going to the extreme
Harper Corporation said that we are in an exciting period in the flexo industry and identified the main trends as increased use of printing to numbers, increased polymer plate line screens, high definition flexo, specialty ink applications and expanded gamut printing. For the increased trend of printing to numbers, its XLT (Xtreme Laser Technology) and XVR technology correlates directly with any print targets chosen. Whether printing to density numbers, dot gain number, G7 or other targets, each anilox roller engraving specification can be matched to the print target and tolerances. This relationship enables printers to operate at a highly efficient level. As the anilox engraving specification is matched to print targets, it enables the standardisation of inventory throughout the operation, minimising the need for ink toning and improving up time. The company has customers using its anilox technology and printing at 600 m/min, using HD Flexo plates and expanded gamut. Harper continues to develop additional engraving options to meet the demand of other sectors of the flexo market for specialty applications such as metallics, fluorescents, glitter and tactile inks. Its channelling technologies include 30° channel, tri-helical, XTR-89°, 75° and XDW. The options of these engravings enables printers to apply unique features to their end product in a flexo set up. As an example, using channel engravings a raised or tactile graphic element can be applied using 40 bcm (billion cubic microns) to 70 bcm rollers on a narrow web press. Having this option eliminates the need for a rotary screen station and enables the printer to finish products in a fast, efficient manner. For the coatings applications, the company has a family of LaserKote engravings. These anilox coating rollers are engraved to unique specifications and delivers specific coat weights requested by the customers. Due to the nature of ceramic, these rollers are extremely durable and once an engraving specifications solution has been found, the result is the delivery of a consistent coat weight for a very long period of time.
‘The increased use of HD technology has set new challenges for the anilox producer. The fine specifications required intricate new cell shapes as ink release and control becomes paramount,’ said managing director of Cheshire Anilox Technology, Paul Smith. He went on to say that the industry initially encountered an overreaction with anilox producers recommending line counts of 1800 lpi and above for UV ink, however, this has proven impractical as ultra fine specifications can damage and score very easily. Tests have proven that once the minimum dot and density has been achieved, there is no need to supply line counts higher than 1600 lpi. The company has found that the majority of its customers have settled for using 1400 lpi, 1200 lpi and 1000 lpi aniloxes.
The company has developed the ProFlo cell engraving, which offers maximum ink release enabling density targets to be reached. Mr Smith said, ‘We are very satisfied with the results and positive feedback from our customers. A by-product of this engraving has been to eradicate spitting problems which is still an issue for some printers.’ Last year, it invested in additional laser technology, a new 500W fibre laser, which incorporates a custom pulse mode that enables graphical control for the creation of bespoke cell shapes. This has helped it to develop a new range of specifications; its research so far has focused on maximising ink release and achieving density and controlling the way ink is transferred. With regard to solvent-based ink, the company is finding that the flexible packaging industry has settled using line counts between 1000 and 1200 lpi for HD plates. Its new range of specifications are improving quality in corrugated envelope and the coating industry, however, concluded Mr Smith, ‘This still requires a high level of consistency and repeatability so control of the ceramic coating is very important which is why major anilox companies are investing in this technology.’
Pamarco offers the EFlo-HD for high definition printing
New coatings plant
Sandon Global works closely with printers and ink manufacturers to beta test and resolve print quality issues. It has just commissioned a new £500,000 thermal plasma coating facility at its premises in Runcorn, Cheshire, giving it full control over the entire production process. For advanced plate systems and high definition printing, Sandon has the iPro engraving technology. The design of this engraving, with its tri-axial ratios, facilitates higher ink release and therefore gives the ability of strong process colour on screens of up to 1200 l/inch. The cell structure combined with a modified and improved cell angle profile provides a more consistent and improved ink lay. The cell angle allows printers to work with an enhanced colour gamut, with no discernable loss of colour density or the anilox angle creating screen clash with the printing plate. Its high opacity white (HOW) and high opacity colour (HOC) engravings were developed for the narrow web market. These were followed by a product specifically for wide web printing, the high volume process (HVP) engraving that enhances efficiency and productivity, together with offering a better image definition and print consistency.
Phil Hall, managing director of Troika Systems, who works with all the major anilox manufacturers providing anilox volume measurement equipment, has his own views, ‘The industry is moving towards a more open cell structure, ie elongated cells or channels. There is the ability to produce different and better cells now and this is reflected in the print we see.’ He continued to say that there is a desire in the market to get more consistent readings and knowing the real volume of each anilox. Printers are becoming aware that there are time and ink savings to be had in production by accurate measurement. On the topic of high definition printing, Mr Hall said, ‘We are seeing some fabulous results now with HD Flexo printing. This is due to better aniloxes and inks, as well as a better understanding of the plates. For finer line aniloxes though there needs to be a solid wall structure in place as these are otherwise prone to breaking because they become too thin. A balance between reliability and enough volume must be found.’