MAXSON AUTOMATIC MACHINERY COMPANY (Westerly RI USA) now offers a retrofit package for roll stands designed to allow for automatic brake compensation as the roll diameter decreases. The retrofit package frees the Operator from having to adjust the brake pressure while rolls are being converted. The proportional tension design is superior to either a dancer roll or load cell tension control approach because it is easier to install, simpler to use and provides the precise web tautness that is requried for accuare cut offs on sheeters.
The system includes a tension controller, an electronic-pneumatic converter and a proximity sensor. The Operator inputs the initial roll diameter, the core diameter and material thickness.
The sensor monitors the number of rotations. This signal is fed to the tension controller, which reduces the diameter. The controller continually transmits voltage to the electro - pneumatic (E-P) converter. As the roll diameter reduces, the voltage lessens proportionately. The E-P converter translates the voltage to a pneumatic output - air pressure. As the voltage decreases, the air pressure fed to the roll stand brakes is reduced.
When tied to the sheeter's logic control, an added feature of the retrofit package is the ability of thetension controller to monitor a preset “low roll” diameter condition. When a “low roll” diameter is reached, a signal is sent to the sheeter drive to slow down to a minimum line speed and stop at a preset diameter a few wraps before reaching the core.