Backing Tension Control System
Primary Backing Tension Control serves many purposes in the Carpet Tufting Industry, depending on the product being tufted and the markets sought.
· Accurate stitch rate achievement saves yarn.
· Elimination of stop/start marks.
· Consistently uniform backing tension from full backing roll to empty roll.
· Side matching problems are minimized and in many cases eliminated altogether.
· As is often the case in the Carpet industry the problems caused by uneven backing tension have their unique set of solutions. Accurate design of the three primary system components cannot be minimized.
· Tension Sensor design depends primarily on the amount of torque imparted by the backing material as it enters the Tufting Machine.
· Brake design depends on reliability and torque required. Based on our research Magnetic Particle Brakes are by far the most reliable for the process.
· The control function is closed-loop PID (Proportional, Integral, Derivative) and must be accurately calibrated so as to maintain proper tension control automatically day-in and day-out as many of the original variables, such as backing roll weight, change.
Magnetic particles (very similar to iron filings) are located in the powder cavity. Without any voltage/current, they sit in the cavity; however, when voltage/current is applied to the coil, the magnetic flux that is created, tries to bind the particles together, almost like a magnetic particle slush. As the voltage/current is increased, the binding of the particles becomes stronger. The brake rotor passes through these bound particles. The output of the housing is rigidly attached to some portion of the machine. As the particles start to bind together, a resistant force is created on the rotor, slowing, and eventually stopping the output shaft.
When current/voltage is removed from the brake, the input is free to turn with the shaft. Since magnetic particle powder is in the cavity, all magnetic particle units have some type of minimum drag associated with them.
Cycling is achieved by turning the voltage/current to the coil on and off.
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