One problem often encountered in guiding and measuring non-woven material arises from determining the average position of material edges. Because the density and distribution of the fibers may vary, the usual camera-based vision system will have difficulty determining where the material ends. With carefully adjusted backlighting the position information works well until the density changes or the fiber color is altered.
At the same time, there are processes that require accurate measurement and positioning of non-woven material webs. One example is found in the manufacture of asphalt roofing material. Here a non-woven fiberglass substrate must be accurately positioned before coating the material with hot asphalt. A misguided web will result in a major cleanup process to remove the asphalt that missed the target. Not coating the entire strip evenly from side to side will cause quality problems that result in high scrap rates. With Scan-A-Line’s scanned LED technology, the substrate edge is clearly defined as the short term average edge position. This permits reliable position guiding to 0.050 inches or better. Color and density have little or no effect on the edge position measurements. These systems are performing very reliably in the roofing industry, where the environment is dirty, dusty, hot, and generally inhospitable to precision measurements.
Before Scan-A-Line, the webs were traditionally guided by paddles that actuated pneumatic valves to adjust the web position. This ‘bang/bang’ style of correction seldom guided to better than +/- ¼ inch. The abrasive nature of the fiberglass web eventually wore through the edge paddles requiring monthly replacements. When a paddle finally failed it often caused the line to crash resulting in production downtime.
As non-woven materials continue to be used for more applications every day, there are many applications where Scan-A-Line may offer significant process improvements.
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