Inspection prevents costly rejects

Systems that prevent double sheets entering can and end forming processes and causing damage to tools and dies is the speciality of US-based Prime Controls, which has provided a check list of tips on how best to apply them.

The first tip is that double sheet detectors are an essential part of quality control, says Prime, and are used on or near the feeds to sheet feeders, slitter tables, destackers and printing presses. The systems use controls housed in safe cabinets away from the process, with single or dual probes that can be replaced easily to accommodate their wear.

The results of not using such systems can be very expensive. Prime says that at a canmaking plant a double blank entered a press, crashing the die and its repair cost $180,000. A double sheet detector was placed at the infeed and identified when the thickness reading was acceptable. If not, the blank was rejected, protecting the press.

The second tip is aimed at operators of end-making systems. Ends can very easily stick together during manufacture, or be formed in pairs during rotary curling. A set of detectors at the outfeed of these machines will prevent double ends from continuing down the line.

This can be applied to aerosol domes and cones. One of the severest cases was when a canmaker reported that one of its aerosol cans had exploded at a customer’s facility, causing slight injury to an operator. It was the result of two ends being seamed onto the can.

The entire shipment of cans needed to be inspected to ensure there were no more double ends, which was both time consuming and expensive, not to mention the possible loss of the customer. A double end detector would have prevented the occurrence.

The third tip is aimed at the possibility of minute cracks and holes being created during stamping and drawing processes. Depending on the type of can or end, leak detection of these flaws uses light or air. The light tester from Prime is said to be capable of detecting holes of less than five microns in size at speeds of 1,100 ends per minute per lane.

More information from Prime Controls, 4528 Gateway Circle, Dayton, Ohio 45440-1712, USA. Tel: 1 937 435 8659. Website: