Textile Machinery: Roller Gap and Tension Position

Displacement measurement on textile machinery concentrates on two places, drafting and loading and winding and tension. On the drafting side are roller gap and press-roller closing, which determine yarn linear density and fabric thickness. On the winding side are dancer (tension-arm) displacement and package diameter, which determine tension stability and package quality. The shared environment of both lines is airborne fly (short-fibre dust), high shop humidity, and oil at some stations, so dust protection and resistance to fibre wrapping of displacement measurement stand out.

Drafting side: roller gap and loading

In a roller-drafting system the top roller is loaded by the weighting arm onto the bottom roller; the gap between the two rollers determines fibre nipping and draft ratio. Displacement feedback is used for loading control, multi-spindle loading-consistency monitoring, and gap compensation after wear. Multi-spindle consistency is the key point — if gaps differ among spindles on the same machine, count variation results. Multi-channel sensors of the same model and the same measuring range are recommended, with attention paid to repeatability (typically of the order of ±0.002 mm; see the three accuracy terms) rather than the non-linearity figure of a single unit. If the loading actuator is a pneumatic or hydraulic cylinder, the selection framework is given in why hydraulic cylinder position control uses magnetostrictive sensing.

Winding side: dancer and package diameter

Dancer position reflects web/yarn tension directly. A displacement sensor reads the linear displacement corresponding to the dancer angle; the controller adjusts unwind or rewind speed accordingly to hold constant tension. Package diameter grows with winding; displacement feedback can be used for diameter tracking, forming a dual closed loop with the dancer. These mechanisms are mostly oscillating or short-stroke linear motion; a 5-20 μm resolution grade is recommended, and the refresh rate should be checked against the control cycle (see matching response time to the control cycle). After a power loss the dancer absolute position is retained, so homing on power-up is unnecessary (see absolute vs. incremental position).

Typical measuring-point layout on textile machinery

Installation points in fly and high-humidity environments

Fly wraps on the rod and magnet, changing the working gap over time and possibly being carried into the connector; high humidity tests the seal. Countermeasures: fit an anti-wrap sleeve or air-blow cleaning on the rod, specify connectors to IP67 or better (for the meaning of each rating see IP protection ratings), and for profile-type products see Series 18 profile type. For wet areas or stations that require washdown, specify Series 13 mobile hydraulic. Installation and anti-loosening practice is in installing and commissioning in practice; troubleshooting of abnormal readings caused by fibre wrapping is in common-fault troubleshooting.

Interfaces and line integration

Textile equipment is typically built around a servo system. Position feedback may be SSI (deterministic timing, suited to the position loop; see Series 192 SSI digital interface) or a fieldbus type for centralised multi-axis management. Tight-cycle winding stations should check refresh rate and fieldbus synchronisation (see matching response time to the control cycle). Displacement schemes for industrial-robot peripheral axes can be compared with industrial robots: seventh-axis and vertical-axis position.