MADISON, N..J—During tough economic times it is tempting to reduce quality control to cut costs. However Dolph Beyer, an engineer with Mohawk Fine Papers, asserts doing this is actually counterproductive. He has determined using Pressurex® pressure indicating sensor film as a quality control tool actually decreases costs, while significantly improving product quality.
“By taking nip impressions with pressure indicating film every couple of weeks we have extended roll life by a few months in many cases,” says Beyer. “This quality control measure not only lowers costs for the replacement of these covers, but also minimizes equipment downtime.”
When placed between contacting rollers, the sensor film instantaneously and permanently changes color directly proportional to the actual pressure applied. Precise pressure magnitude is then easily determined by comparing color variation results to a color correlation chart (conceptually similar to interpreting litmus paper). Variations in pressure that lead to defects in papermaking, converting, and printing can be quickly and accurately detected and corrected—improving yield, decreasing scrap, and increasing productivity.
By examining pressure variations in the nip, corrections in alignment and crown profiles can be made. The film is effective on virtually all roller compositions and surfaces. A visual pressure mapping profile of an engraved pattern or drilled roll can be effortlessly produced that exposes minute surface defects and other imperfections.
Pressure indicating sensor film is cited by Beyer as being especially helpful with calendar rolls, which are swim rolls that have mechanisms to allow the center of the rollers to exert a different level of pressure. “Similar to crown rolls, swim rolls need to be carefully monitored to ensure even and exacting pressure is being applied to achieve optimum nip conditions,” says Beyer. “We use the film to create just the right nip and improve the roll shape and crown to deliver better sheet uniformity.”