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Fast, accurate colour management is essential for large-scale operators and inline quality checking is quickly becoming de rigueur. Steven Kiernan looks at the latest developments.

Press technology is a fast-moving sector and as a result, printers have to ensure that they stay ahead of the game –  last year’s optional extras quickly become this year’s prerequisites.

Closed-loop quality control is one area that has come under scrutiny recently. Before Drupa 2008, sheetfed colour measurements were generally taken from pulled sheets at the console, but if it’s worth doing off-press, then it’s definitely worth doing inline, and this year’s show will be remembered as the scene of on-press evolution.

Inline colour management may just be a technological development, but it could also mark a cultural revolution in the press hall. On-press colour management systems take over all the tinkering. They read the colour bars as the press is running and feed the information back to the units, which constantly recalibrate ink flow to ensure colours are spot on. The systems provide a host of benefits for sheetfed offset, the first of which is colour quality and as ISO 12647 continues to gain momentum, there is a growing need for foolproof closed-loop colour management. "You couldn’t hope to conform day-to-day to ISO 12647-2 without some form of closed-loop colour," says Paul Sherfield, a partner at graphic arts consultancy Missing Horse. "The larger corporate buyers would like 12647-2 to be as valid as 14001 and 9001."

Then there’s the wastage argument – both economic and environmental. Inline colour control uses far fewer sheets to bring a press up to production than a manual or off-press system, a boon for those printers running expensive substrates, such as packaging materials. For example, Manroland claims its InlineColorPilot takes a complete colour measurement of a five-colour job in just three sheets, and requires only 40 sheets to hit sellable output. Fewer sheets equal shorter makereadies, and thus inline colour control is helping push offset down into short-run territory. A further overarching benefit is that these systems provide an audit trail for customers, giving the type of automatically generated reports that are becoming must-haves for some corporate buyers.

There are three distinct approaches to the technology. The most exact, and expensive, is to use a spectrophotometer. The second is to use a densitometer for process control and then calculate spectral values via ink film weight. The third is to redeploy the sheet inspection camera for process control, as KBA has done with its QualiTronic Professional.

KBA’s system was originally designed purely for sheet inspection, using an RGB line scanner to look out for imperfections such as hickeys or creases. At Drupa, KBA upgraded the technology to also provide inline colour management, a role previously performed by its off-press product Densi-Tronic. A second system can be fitted on perfecting presses to measure colour across both sides of the sheet in a single pass. KBA’s is the least expensive of the three German manufacturers at £120,000-£150,000 for the perfecting version, depending on spec, or around half that for the straight version.

Heidelberg’s Prinect Inpress Control was revealed at Ipex 2006 for the Speedmaster CD 74 and was added to by the XL 105 in 2007. This year’s Drupa marked its first commercial outing for perfecting presses. Inpress uses a measuring bar comprising eight spectrophotometric heads, each of which reads four colour patches as the sheet passes.

Heidelberg says Inpress requires 16 sheets to take a complete evaluation on a four-colour job and 20 for a five-colour. It takes just two minutes and 80 sheets to hit control, having done away with the need to pull and evaluate sheets, or check and correct the register. Inpress Control costs £132,355 to kit out a non-perfecting XL 105.

Pilot project
Manroland used Drupa to announce the newest development in its ColorPilot quality control technology. It has had an off-press quality control system for sheetfed presses, ColorPilot, for years, but used the exhibition to demonstrate the sheetfed applications of InlineColorPilot (ICP), which has been available on its web presses since 2004.

The system uses an array of densitometers, which read colour by analysing the ink film weight then using clever equations to work out a spectral value much quicker than a spectrophotometer – ICP takes just three sheets for a full measurement of a five-colour job and is claimed to match the control sheet after only 40 sheets.

The ICP measuring heads, which comprise 15 fixed sensors in a cassette that runs the entire width of the sheet, are situated inside the machine on the final unit for a straight press and also the perfecting unit for double-sided work. The head, which has a fixed LED array with no moving parts, uses an air curtain running across the apertures of the LEDs, meaning it only needs to cleaned every 80 days. The straight version of ICP comes in at £200,000, or around double that for the perfecting version. It is currently available for the Roland 900 and 900XXL, with plans to roll it out commercially across the 700 range in 2009, including retrofits to newer models.

Komori has taken a proactive approach to on-press quality control with updates to its KHS system. The Japanese manufacturer’s KHS-AI (advanced interface) product, which was launched at Drupa 2004 for web presses, has now been rolled out across its sheetfed Lithrone series for the LS 40, SX 40, LS 29 and SX 29 models. KHS-AI memorises ink key profiles from pre-press and ‘self-learns’ any changes the operator makes to download information, such as different paper types and ink values. It will then use those settings for any equivalent subsequent jobs. Komori says the system needs just 20 sheets to adjust the settings.

Photo finish
Drupa marked Ryobi’s assault on the B1 market with its 1050 press, which incorporates inline colour management and sheet inspection. Similar to KBA’s QualiTronic, it uses a CCD camera over the last transfer cylinder to read the colour bars and automatically feed data back to the ink keys.

As well as the above manufacturers’ own technology, Drupa also played host to a new third-party OEM system that can be retrofitted to sheetfed presses. SpectraCon is the brainchild of Theta System chief executive Theodor Tatarczyk, who six years ago helped develop Manroland’s InlineColorPilot. Other than Heidelberg, SpectraCon is the only product covered here that uses a spectrophotometer for inline colour control. It is also the only one offering inline in-image measuring, a feature also available off-press with Heidelberg’s ImageControl. Each SpectraCon system comes bespoke – an entry-level system with a 2D spectrophotometer on a traverse bar that scans at 70mm per second takes a full reading in 60-80 seconds and costs about €50,000 (£40,000). At the upper-end, the system can be specified to cover the entire press width with a high-speed scanner that hits 240mm per second. Tatarczyk claims a makeready takes around 200 sheets, although that number depends on both the speed of the press and its software. A first-time install can take anywhere up to five months to integrate the system.

With prices running from the tens up into the hundreds of thousands of pounds, inline quality control doesn’t come cheap. But expensive doesn’t necessarily mean unaffordable.

The technology currently only resides with larger-format kit and it’s debateable whether it will become economically viable in the B2 market, and extremely unlikely it’ll move down into B3. However, even though ISO 12647 continues to demand standardised printing conditions and watertight process control, market penetration is still a matter of cost, not demand, but one day, inline colour management could well become a prerequisite across the sheetfed sector.