MAXSON AUTOMATIC MACHINERY COMPANY (Westerly RI) offers a retrofit package for unwinds allowing automatic brake compensation as the roll diameter decreases.
The retrofit package frees the Operator from adjusting 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
- Provides the precise web tautness that is required for accurate cut offs on sheeters.
The retrofit package includes a tension controller, an electronic-pneumatic (E-P) 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 of the roll stand spindle. This reducing diameter signal is fed to the tension controller.
The controller sends voltage to the E-P converter. As the diameter reduces, the voltage lowers. The E-P converter translates the voltage to air pressure. As the voltage decreases, air pressure 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 the tension 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.