2. The theory of correcting and monitoring index:
The light beam of the sensor is set to impinge on the print mark of the lid foil. Intensionally increasing the correct conveying length (X) to (X+0.05~0.1mm)by conveying length ruler .So the actual conveying length (X+0.05~0.1mm)must be larger than the interval of print mark(X±0.1).The print mark will diverge gradually from the light beam(finally ,the print mark is below the light beam further, as Figure A ) after running 3-8 times continuously .