OPTICAL ONLINE MEASUREMENT OF THE THICKNESS DISTRIBUTION OF BLOW MOLDING PARISONS

An optical sensor has been developed which can measure the thickness p rofile of the parison on line just prior to its enclosure in the mold. The device determines thickness by striking the parison at an angle w ith a laser beam and measuring the separation between the beams that a re reflected from the outer and inner surfaces of the parison wall. A prototype was built and tested. The prototype uses three lasers at dif ferent angles and can make up to 250 point measurements during a one s econd scan. A personal computer uses specially developed software to r econstruct the profile of the parison wall from the raw data with an a ccuracy of +/-5%.