Wire Drawing Machine Automation

On a straight-line wire drawing machine each block consists of a capstan, the motor driving it and a die box in front of it. The wire is pulled through the die, wraps a few turns around the capstan and moves on to the next die. Section ratio: speed of block n+1 = speed of block n × (d_n / d_n+1)². As dies wear and wire temperature changes, the real elongation drifts from the design value, so speeds have to be corrected by measurement, not only by calculation.

Small speed differences between blocks are sensed by dancers the wire runs through: the dancer is held against wire tension by a pneumatic cylinder or spring and its position is read by a potentiometer or encoder. The controller corrects each block's speed by PID to hold the dancer in its middle position. Usually the last block (or the spooler) is the line speed reference and, working backwards, each block is set from the next block's speed and its dancer. On accumulating machines without dancers the wire builds up on the capstan; this layout can mark the wire surface and cause tension ripple.

Wet (slip) drawing machines are used for fine copper and aluminium wire; all steps turn from one motor through gears and the wire slips over the steps. On these machines control focuses on the main motor, the annealer (resistance annealing) and the spooler. On heavy wire and rebar (ribbed wire) lines, the drawing or cold rolling (ribbing) unit is followed by straightening and cut-to-length or coil winding.

On the spooler, speed drops as the spool diameter grows; tension is held by a dancer or by torque control from diameter calculation. A traverse guide lays the wire in layers on the spool and reverses at the flange. In fast stops all blocks have to stop together while holding their ratio; the energy released can be used by other motors over a common DC bus or fed back to the mains.

In the ONX architecture the last block or the spooler is the line speed reference; the other blocks get speed references as a feed-forward from the elongation ratio, corrected by PID from dancer position. This control runs in CODESYS and block drives are updated in the same cycle over EtherCAT or a fast network. Acceleration and deceleration ramps are applied to all blocks together.

Closed-loop vector AC drives are used for block motors; a common DC bus or regenerative supply handles braking energy. Spooler tension is held by diameter calculation and torque control and the traverse axis is driven by a servo. Die sequence, speeds and tensions come from the recipe; wire breaks and dancer end positions stop the line at once.

The architecture on this page is built on the drive and control platform ONX Control uses in load sharing, winder tension control and DC to AC retrofit applications. We work out your machine's block count and drive structure together in a meeting.

A typical picture on wire drawing machines: DC motor blocks, speed ratios set by hand with potentiometers, analog dancer circuits, frequent wire breaks and blocks stopping at different times in an emergency. In a retrofit the blocks, die boxes and spooler mechanics are kept; the drives are renewed or moved to AC and the speed cascade and dancer control move to one controller.