Wet proofing on AV Flexologic machine
Presenting the customer with a proof that is as close to the finished print as possible while keeping costs down remains a challenge for flexo pre-press houses and printers. By Neel Madsen.
Getting to press with aniloxes, plates and ink that will produce the correct print the first time is what flexographic printing is all about. But with a process that has so many variables, the importance of accurate proofing becomes ever more important. Both flexo proofers and digital proofing each have their own advantages and we look here at some of the many options available.
Flexo proofing
Traditional freestanding proofing machines are still used by many printers as these have the advantage of being able to check the contents of the plate and ensure that they have been produced correctly before they go on the press. Other options include machines that combine the mounting and proofing operations.
Having sold over one thousand proofing machines and proving that there is a definite demand for flexo proofing, JM Heaford’s customer base is made up of printers, repro houses and plate and sleeve manufacturers, and in the case of gravure, also cylinder manufacturers.
Sally-Anne Heaford said, ‘While digital proofing obviously has its benefits, customers continue to purchase flexo proofing machines because they can replicate press parameters without the expensive business of supplying incorrect plates or running production press trials for customer approvals. They remove the remaining uncertainties from digital proofing and can also be used for testing production inks and substrates saving the significant costs associated with carrying out this testing on production press.’
The company said that flexo proofing presses, using production aniloxes and doctor blades, ink and substrate are able to achieve a match of between 95% and 98% of the production result. Customers use the flexo proof presses for either quality control of platemaking and continuous sleeves or customer approvals. A colour takes 10 minutes to proof and the investment in the machine is quickly recovered. One customer in South America said that the cost of the machine was recovered in less than a year on savings on airfares from not flying customers to its facility for on-press approvals.
Flexo proof presses are available in narrow or wide web, geared or servo driven and can be used for cylinders, sleeves or continuous sleeves. Servo driven machines are fully electronic with motors controlling the rotation and impressions settings. Any issues can be dealt with via a remote diagnostics. The proofing function can also be incorporated into the plate mounting process and the company has a wide range of mounter proofers on the market.
Ms Heaford continued to explain that while it is difficult to provide an absolute answer on costs of digital versus flexo proofing, the following factors are relevant. Capital costs are higher for flexo proofers but the life times are much longer, 15 to 20 years compared to 3 to 5 years. Operating costs for inks and consumables are higher for digital proofing. Key in the calculations is the savings from elimination of production press proofing.
She concluded, ‘Flexo proofing will identify the faults that digital proofing can’t, namely manufacturing errors in plates and sleeves. Though digital proofing is becoming more prevalent, there is still a definite requirement for flexo proofing. The increasing technology incorporated into our proof presses reflects the users demands on this type of proofing.’
AV Flexologic’s Flexo Proof Press has a chromium coated cylinder to support the substrate, a cantilever sleeve change system for printing sleeves and an anilox sleeve. The ink deck is driven with AC servo motors, while the ink chamber has been designed so that it is very easy to change ink and clean the system. With a max proofing length of 3500 mm and width up to 1700 mm, the proofer prints at speeds of up to 100 m/min.
Many of the company’s mounting systems also offer the operator the ability to make a 100% print before bringing the sleeves to the printing press. As such, the complete image can be checked for plate mistakes, and with a magnifier it can also be determined if the printing plates are mounted within registration. This can either be done by the operator manually or by using a computer controlled system which positions the proofing drum and pulls a proof automatically.
Digital proofing
Until the late 1990s, the printing industry mainly relied on manual processes to produce proofs, but with the arrival of wide format inkjet devices, software developers began to develop front end proofing solutions to control both data interpretation and colour output. From a production perspective, the benefits of utilising inkjet technology were threefold: the low cost of proof, speed and automation.
Early software developers engineered proofing applications that printed continuous tone, or ‘Contone’ images, which output a stochastic or FM screen, giving a photo-like effect on the proof. Since the early inkjet devices were limited to an output resolution of 720 dpi, the decision to choose Contone as an output format was understandable and Contone proof systems became popular among the largest target market, the offset printing industry.
Mimic then merge
The flexo sector however required a more refined solution to show the effect of various production influences, and Kodak’s Approval system (see below) became popular amongst the packaging fraternity. Software to meet the challenge of using inkjet devices to produce a cost effective yet colour correct halftone proof was developed by ISI Graphic System, the developer of the Star Proof proofing system.
Graphic Republik’s Steve Donegan explained, ‘Star Proof works by using the final colour separated 1-bit Tiff or Len files which will be used to image the flexo plate. Each colour is independently corrected for ink hue, dot gain, overprint and grey balance to mimic different press/substrate characteristics. The separations are then merged to create a final print file with the resultant inkjet proof showing the actual dot structure, which will be seen on press.’
Additional flexo related features are also available, such as ‘ink spread’ which shows the effect of pressure related dot gain, ‘dot loss’ which mimics the effect of lost dots in highlight areas, and ‘spot colours’ which are automatically calibrated via a multi colour library.
More recent developments by inkjet manufacturers have further expanded the quality offering. Additional ink sets, such as orange and green, help to closer match spot colours, and devices are now capable of outputting at high resolutions of 2880 dpi. With the introduction of the Stylus Pro WT7900 device, Epson has addressed another key packaging proof requirement – the appearance of white ink.
Released in 2010, the WT allows for an opaque white ink to be printed on substrates ranging from transparent and adhesive films through to metallic foils. As the white can be applied surface or reverse print, it enables a broad spectrum of packaging proofs and mockups to be created. One additional benefit is that this white ink set is water based and needs no special ventilation is unnecessary.
Linking with the cloud
Esko’s FlexProof, an option on the Imagine Engine RIP solution, will also output contract proofs to a range of Epson printers. It integrates with Color Engine and PantoneLIVE for colour management and Automation Engine for workflow.
‘In the packaging market, the accuracy of brand colours is critical. Research shows that consumers spend five seconds or less making their decision on what product to pick from the shelf – the brand colour is a key to picking the product. Consistency and predictability of colour in packaging is an important requirement for the brand owner,’ said David Harris, Esko product manager, RIPs and screening.
An end-to-end workflow for brand colours, such as PantoneLIVE recently announced by X-rite, promises to deliver this predictability. A uniform digital colour standard in the cloud is made available to all stakeholders from brand owner, designer, pre-press to printer. This standard is used for proofing (soft and hard copy contract) to formulate the ink for press, and to quality control the final result. Use of this uniform standard is a way to assure that the proof matches the printed result.
Esko has partnered with X-rite in the PantoneLIVE workflow, to implement the connection from the cloud into pre-press software – especially the FlexProof contract proofing solution. In the latest Esko Suite 12 software, FlexProof can use PantoneLIVE data to accurately match the brand colours when driving a range of inkjet proof printers.
FlexProof accurately matches both spot colour solids and breakdowns (undertones) and includes a patented model for prediction of spot colour overprints. It also has a comprehensive tool for matching dot gain and highlight break behaviour, essential for prediction of the result in flexo printing.
With approval
With Kodak’s true colour halftone quality proofing system Approval, the flexo printer can build colour as on press, accurately capturing all the variables and provide a contract quality proof. The system can check accuracy, consistency, colour and appearance and consistently control screen angles, screen ruling, density per colour and dot shapes.
Approval was designed to mimic the quality of a printing press using high resolution imaging (2400 or 2540 dpi similar to the printing plate) and halftone screening to accurately reflect what would be seen on press. In addition, stochastic screening (or FM screening) can be used to proof print runs with this screening technique. Being able to simulate screening effects with high fidelity makes it possible to detect undesirable screening artefacts, such as moiré patterns, before going to press, consequently saving time and money.
The company explained with that the wide range of colour donors possible with this system, the printer can simulate and accurately process spot and metallic colours for flexo and gravure printing creating three-dimensional, corporate brand package mock up proofs with appearance identical to the final product on the store shelf. Process donors include cyan, magenta, yellow and black with additional donors, orange, green and blue extending the colour gamut. There are two opaque donors: white and metallic, which combined with the other colour donors allows for the creation of a wide range of metallic colours, such as gold, copper and bronze. This produces special effects not possible via inkjet printers but commonly used in today’s packaging print process.
For packaging applications it is possible to transfer the images to many of the different substrates used in the industry today. White is a critical tool in replicating packaging printing that will be applied to clear packaging. The adjustable laydown order allows exact representation of the pre-press shop’s most difficult print jobs such as package labels and lottery cards were white or silver is required on the top and bottom. Approval proofs are also highly effective for three dimensional mock ups of the actual package.
Elephant in the room
To meet the needs of the packaging and label sector, with its greater substrate and spot colour diversity, GMG’s FlexoProof software offers production reliability due to its screen control. It processes the original 1-bit data of the imagesetter RIP. The data is colour profiled, retaining the original screen information, and output on inkjet printers in contract proof quality.
However, according to the company, there remains one unsolved problem, or ‘elephant in the room’, in colour management, and that is what is known as ‘spot colour overprint’, ‘multi-channel profiling’ or ‘extended gamut printing’.
Launched at drupa this year, OpenColor is a new solution that predicts ink behaviour on a specific substrate for each press set up without the rigours of ‘proprietary chart based’ press fingerprinting. This technology uses process modelling algorithms coupled with spectral ink measurement that analyses the ink pigments within each ink colour as well as the substrate’s colourimetric properties.
The company said, ‘Until now, the overprinting behaviour and colour interplay between CMYK and spot colours could only be reproduced by combining a CMYK profile with spot colour libraries. This method required considerable effort to depict all possible combinations of spots and process colours ‘as accurately as possible’. The major drawback of this method was the inaccurate simulation of spot colour overprints.’
With the increasing use of multi-colour printing, the simulation of spot colour overprints currently poses one of the biggest challenges for packaging printers and OpenColor claims to be the first profiling tool on the market that provides this capability. Offering accurate predictions of overprints, it creates high quality multi-colour profiles simulating the printing behaviour of diverse printing technologies, media types and screenings.
Going live
Hybrid Software’s Proofscope is a new online soft proofing, annotation, viewing and editing solution, which extends the functionality of the company’s Frontdesk upload, ordering and job management portal. It is a pure HTML 5 solution, which does not require any applet or plug-in to be installed and as such conforms to the customer’s IT security regulations. This makes it compatible with almost all desktop and mobile browsers, including Android, iPhone and iPad.
The software has been designed to ensure the customer can participate seamlessly in online approval and collaboration projects, with comprehensive and extensive viewing and annotation functionality, without the need to send the actual production file across the network.
drupa saw the launch of Proofscope Live, which adds the ability to make live, last minute corrections to production artwork from a remote location using any web browser. PDF files are published directly in the browser, with all aspects of the layout available for editing, such as fonts, images and colours. The multi-platform server software – Windows and Mac OS X – is simple to use and supports multiple, concurrent users. The software offers a range of professional tools including separation viewing, densitometer, measuring capabilities, difference viewing between versions of files and annotations.
‘Proofscope Live is an enhancement, which allows online soft proofing, annotation, viewing and live editing,’ said Mike Rottenborn, president and CEO. ‘It has been designed to work with HTML 5 and JavaScript, which means that the viewer can be used with any tablet or mobile, unlike most other soft proofing systems on the market. No Flash code or Java applets are used in Proofscope or Proofscope Live, eliminating the security bottlenecks that exist with many other soft proofing tools.’
