Background: A pattern is created on a moving web by a spinning steel wheel. The Web is only 5 mils thick. When the product is made right, the pattern is 3 mils deep into the 5 mil web, leaving exactly 2 mils left. During normal production, the line speed varies between 0 and about 2000 FPM. The speed changes cause the steel wheel to expand by 3.5 mils. Five engineers had tried to minimize scrap for 4 years.
Problem: Because of frequent line speed changes and corresponding wheel diameter changes, the depth of pattern can only be correct at one speed. Thus as the line speeds up and slows down it creates off-spec product and scrap, still costing over $ 2M/year after a switch to composite wheels.
Core Problem: The wheel growth is caused by centripital acceration of a weighted wheel, causing a force or tensile stress, that stretches the wheel into a larger diameter. To reduce wheel growth, the other engineers tired expensive composite materials to lighten the weight and increase the tensile modulus. Their approach could not reduce the wheel growth below 1.6 mils.
New Design Results: The new design eliminated wheel growth as it sped up and slowed down. It was also made of steel.
Process Results: Pattern Depth became consistent and independant of line speed, saving over $ 2MM/year in scrap and reducing required run time of equipment.
Bloomdahl Engineering 