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Lights, Camera, Action!

No matter what type of inspection you employ, when a fault is detected, action is taken.

February 2008 by Chris Mc Loone
Boy, there’s a lot to inspection! In-line versus off-line, rewind versus press-mounted, the human eye versus video—these are only a few, but critical, considerations. There are various inspection systems on the market, some for use on the press, and some for use on the rewinder as the web is rewound. Each inspection system is designed to take certain actions when it detects a defect in the printed product. These defects can range from registration to incorrect characters. In addition, with brand protection emerging as a growing market niche, the ability to inspect microprinting and other security markings not visible to the naked eye is becoming even more critical to the success of a print run.

Taking action

No matter what type of inspection you employ, when a fault is detected, action is taken. Alfonse Novelli, owner, ­Novation, notes three possible actions:

1. The web can be automatically marked or flagged by a piece of equipment for removal of the defect at a downstream process;

2. The inspection rewinder, if running slowly enough, can be stopped at the location of the defect for removal and splicing at that time; and

3. The inspection rewinder, if running too fast to be stopped at the location of the defect, can be reversed to the location of the defect for removal and splicing at that time.

Tim Lydell, Label Vision Systems cites four actions the inspection rewinder can take when an error is detected:

1. Display the error on a monitor/notification light so the operator knows a problem was detected;

2. Activate a flagging or marking device so the error is marked for extraction in subsequent operations;

3. If it is on a printer, stop the print line and make the correction to the defective area; and

4. If it is on a rewind inspection device, it can stop the rewinder and reposition the defect at the cut table so it can be corrected as needed.

Brian Ivens, manager of sales and marketing for Arpeco, states that, “Most finishing machines provide several functions [like inspection, slitting, counting, and rewinding] at the same time to maximize throughput and minimize the number of passes that the product must go through.” According to Ivens, when slitting and rewinding, it is undesirable to reverse the web direction because of potential slitting inaccuracies, so most machines that perform these functions are unidirectional. “On a typical unidirecitonal machine, traveling at speeds of up to 1,000 fpm, when an error is detected the machine slows down and forward-places the fault to a position suited for operator correction,” he says. However, after the operator makes the necessary corrections, the web is not reinspected, leaving potential errors, which may have been missed by the operator, on the finished roll and shipped to the customer. “For some products, this is not a problem,” Ivens adds.” But for pharmaceutical or the security or high value-added products, these errors are unacceptable.”


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