Posted to News on 28th Oct 2024, 16:30
Analogue inductives trusted to manage web tension
Textile handling machines push the boundaries of speed and precision, making a fit with the speed, precision, long range and reliability of Contrinex's analogue Inductive sensors. The sensor's accuracy of a few microns is used to measure the small changes in the position of a 'dancer' roller or 'follower', which tracks the fabric web's position and so indicates the web's tension.
As the textile web is unwound and fed into the machine, the control system must compensate for minor changes in tension. These can be due to variations in the properties of the fabric and from within the machine itself, such as slight deformation of the rollers, worn bearings, alignment issues, and the requirement to enable acceleration/deceleration to make speed changes.
A web tension control system registers these tension changes via a dancer roller, which rises and falls constantly in small increments ('dancing'). The customer typically uses an encoder or precision potentiometers to measure the 'dancer' roller's position, with the measurement being fed into a tension control system, which in turn provides continuous feedback to a variable speed drive to accelerate or decelerate accordingly.
Encoders and potentiometers have a moving shaft coupled to the pivoting dancer arm of the dancer system. Therefore, they are subject to wear and tear on delicate bearing surfaces and limitations in the service life of the encoders and potentiometers in a dusty or fluffy environment. To avoid these problems, the customer was looking for a non-contact solution.
Contrinex analogue inductive sensors combine high precision with long sensing ranges of up to 40mm. However, this application only utilised the sensor's precision measurement accurate to a few microns in this dusty environment. The sensor's Condist oscillator technology ensures excellent temperature stability and repeat accuracy, which is required for precision measurement in the micron range.
Their excellent speed, resolution and continuous non-digitised output is particularly suitable for fast precise measurement of the constantly 'dancing' roll in this feedback control system.
Using an analogue inductive sensor requires no mechanical contact but merely an elliptical metal target or direct view of the moving dancer arm. It is then possible to interface the sensor output directly to a controller, with several switch points included in a single device. This dramatically simplifies installation, while the problems of wear and tear associated with mechanical contact are also avoided.
