Inspector Gadgets

A well-suited web inspection system can open the door to increased production and profitability for printers.

IN THE LAST 10 years, web inspection systems have come a long way. They have developed into automated machines with the ability for literal 100 percent web inspection, rendering the need for manual inspection nearly obsolete.

However, the highest quality inspection systems aren't necessary for every converter, and with so many options and confusing characterizations of the newest technology, knowing what system to choose can be difficult.

What to look for

There are three basic requirements a web inspection system should include, said John Woolley, vice president of sales and marketing at PC Industries (Gurnee, Ill.): high-resolution digital cameras, high-speed computer processing, and automatic print defect detection. High-resolution digital cameras produce better image detail and clarity, and faster computers are necessary for 100 percent web inspection, Woolley explained. Automated defect detection capabilities automatically alert the operator to changes in print quality.

It's important, however, that the defect detection technology not overreact to flaws in the print job, said Nat Stern, CEO of Eltromat Electronics Inc. (Chesapeake,Va.). "The [imaging technology] must react similar to an operator. Certain technical defects are not considered a defect by an operator and are called false alarms," Stern explained. "The more sensitive a system, the more the chance for false alarms."

Buyers should also look for computerized customer interfaces, said Wayne Storts, CEO of Summit Engineering (Keysville, Va.). Computerized interfaces give printers the ability to view and archive data by rolls produced, and they create an easy method for customers to setup defects by categories, Storts said.

Quality web inspection systems come with many benefits. They minimize or eliminate return products from customers, increase line speeds, reduce operator work loads, and produce a consistent product, explained Warren Friedersdorf, sales manager of TEKMATEX, Inc.'s (Charlotte, N.C.) Converting Machinery Group.

However, said Lance Shumaker, president of Advanced Vision Technology, Inc. (AVT, Atlanta, Ga.), "The real justification behind all of this equipment today is to improve profitability. You find defects before they become waste and you decrease costs. That's the major overriding factor."

Assessing equipment needs

Printers have several ways to assess their needs when shopping for a web inspection system. Ignatius Manning, president of Print Vision Systems (Lewiston, N.Y.), recommends first taking a look at what type of jobs are being produced, the industries served, and to determine the purpose of the inspection technology.

Another way to determine what kind of system is needed, Friedersdorf points out, is "How small of a defect does the customer need to detect?"

Printers serving the pharmaceutical industry are faced with tough printing standards stipulated by the FDA, Manning said. When miniscule defects like a missing decimal point need to be detected, such as in pharmaceutical label printing, a 100 percent inspection system is in order.

However, "If quality requirements are low and inspection is mainly needed to cut down on makeready and setup time, a web viewing system might be all that is required," Manning added

A web viewing system, as explained by Woolley, presents the operator with an image of the web, from which the operator manually inspects the print quality. But the sampling and 100 percent inspection systems on the market today are notably more reliable than human sight. That's not to say that web viewers aren't the best-suited equipment for some printers.

What it comes down to is the bottom line: "Web viewing systems typically cost $7,500 to $21,000; web sampling systems typically cost $75,000 to $130,000, and true 100 percent inspection systems cost $40,000 for some narrow-web gross-error detection applications, and up to $80,000 to $100,000-plus for 100 percent true color inspection systems," said Manning. "The key is in finding the right-sized solutions for a company's range of applications."

100 percent vs. sampling

The term 100 percent inspection has been made very confusing over the years. But simply put, said Jim Doerr, president and CEO of TruColor Vision Systems, Inc. (LaGrange, Ga.), "One hundred percent inspection must meet the requirement that every single inch (or meter) of the substrate, both in the repeat and across the web is being processed, captured, and/or inspected 100 percent of the time during production. If this is not the case, then the system is sampling."

One hundred percent inspection systems use a line CCD camera that takes a line of pixels from one side of the web to the other—covering every inch of the web, all the time—and memorizes the pixel formations, explained Shumaker.

Woolley added, "One hundred percent inspection can be accomplished using high-speed digital area scan cameras. The latest systems can merge multiple cameras mounted across the web and triggered down the web which provides true 100 percent continuous inspection of the web and a full image of the entire repeat."

An added benefit of this process is that 100 percent inspection systems can identify the location of a defect, said Friedersdorf. "The location is both in the machine direction (footage) and cross web direction (usually in inches)," he said. "This allows precise location of the defect."

Systems with 100 percent inspection have the ability to catch random defects, as well as repeat defects.

A sampling system, Shumaker said, uses a CCD, 3-chip color camera, which moves back and forth over the web, covering 100 percent of the web, but not 100 percent of the time. "The typical sampling system will only inspect approximately 3 to 10 percent of the total printed production," said Manning. "These web sampling systems will eventually inspect the entire pattern that is repeated, but not every segment of the web," and not immediately, added Stern. "Up to 100 percent of the surface is checked, piece by piece, or sampled," Stern explained. "Typically, each piece is inspected in one to five seconds. An entire 100 percent of the surface would take typically two minutes."

While sampling systems are very good at recognizing repeat defects, they aren't as reliable at detecting random defects. However, said Stern, "Sampled systems have higher resolutions and more time to make an intelligent decision about defects. The limitation is the inability to find sporadic defects. One hundred percent systems have lower resolutions and less time to make a decision, but can find sporadic defects. Sampled systems can detect the birth of a defect allowing corrective actions to be taken avoiding waste, thus are excellent tools for process control. One hundred percent is ideal for final inspection applications where zero major defects is required."

Looking ahead

Improvements in color measurement, press control, cameras, and process control are already happening due to advances in web inspection technology. But the future of web inspection, industry suppliers agree, is more automation and smarter machines, including a degree of artificial intelligence.

"In three to five years, you can expect inspection systems with a higher level of intelligence—that is to say to perform more and more like human inspectors—with the ability to make deterministic judgments, however, at production speeds of a magnitude beyond the capabilities of human inspectors," Manning said.

Stern agrees, saying, "The future systems will be refinements on today's technology with higher processing speeds, better resolution, more intelligent algorithms with self learning ability. The future systems will also start to suggest corrective actions required and eventually will feedback directly to the press, automatically correcting the problem."