Introduction to passive unwinding of film slitting machines

Passive unwinders, also known as brake unwinders, use brakes on the unwind roller to generate resistive torque and create tension in the film substrate.
During the rotation of the slitting machine, since the diameter of the web is constantly changing, the unwinding brake should be compensated accordingly to maintain a constant material tension. When the diameter of the roll becomes smaller, the unwinding brake must gradually reduce the torque tension. Excessive tension may cause the material to stretch or even break. The tension sensor transmits the detected tension signal to the PLC. After PID and comparison calculations, the PLC issues instructions to the tension amplifier, and then gradually reduces the input current to the magnetic powder brake to achieve the purpose of reducing the torque to maintain appropriate film constant. Tension run. Generally speaking, this unwinding method is suitable for small film slitting machines with narrow width, but not for some tension-sensitive materials.