Control Algorithm for an Unwinding Machine’s Electric Motor on a Rebar Production Line

One of the key factors leading to product quality improvement by reducing the imperfect product percentage on rebar production lines lies in modernization of electric motors' control system. Known technical solutions for those systems were developed without consideration of their effect to the quality of the rebar. One of the important quality factors characteristic of the rebar is depths of notches on it. It is established that the electric motors that drive the rebar line's units can affect the depths of notches on the processed rebar wire. The objective of this paper is the development of the unwinding machine's electric motor control system algorithm which would decrease imperfect product percentage caused by the deviation of the depths of notches on the wire from desired values. The objective was achieved based on analytical methods for solving algebraic problems, computer modeling methods and statistical processing of the experimental data consisting of depths of notches values and the line's electric motors' load torque alteration values. Novelty of the paper is in proposing new control algorithm for the unwinding machine electric motor. That algorithm stabilizes rebar wire tension on a specified level at the inlet of profile stand by the means of alteration of the breaking torque that is produced by the unwinding machine's electric motor. That, in turn, decreases depths of notches deviation. As a result of the implementation of this algorithm there was obtained decrease in rebar percentage that has depths of notches out of allowable range from 7.2 % to 1.1 %.