This type of system measures the forces created by the tension in the material web as it passes over a roller placed in the web path. This force is measured by the load cells at each end of the roller and provided as an input to the tension controller. The tension controller itself will vary dependent on the customer requirements, from a simple dedicated controller unit to a software driven PC type system and all points in between. The customer has control of this part of the specification.
The controller will provide either a voltage or pressure output to the brake, clutch or motor to change the tension either up or down dependent on the difference between the actual measured tension and the desired tension setting.
This is a closed loop system with the tension being measured continuously and fed back to the controller for continuous corrections, enabling the system to maintain the desired tension.
Dependent on the most suitable or customer required system configuration, setting of the desired tension is achieved with various methods from a simple dial on the front of the control unit to remote input over the internet.
As with all our systems we look for quick and simple installation, requiring only the necessary services to the control cabinet. Fix into the pre-determined position the measuring roller with its pre-connected load cells using the brackets provided. Output connection will vary dependent on the system, but most commonly 6mm Nylon airline to either brake, clutch or Differential shaft and the system is ready to go.
Closed Loop Tension Control Systems
Closed Loop or “Feedback” Tension Control systems operate by continuously monitoring the Web Tension and continuously adjusting the torque applied to the material roll to achieve the desired tension in the material web.
The component parts of a closed loop system are as follows: –
Continuous Monitoring of Web Tension
This is achieved with the installation of a measuring roller within the web path, at a location which allows the material to form a suitable wrap around the roller and create a force upon it. The measuring roller is usually fitted with a correctly sized “Load Cell” on the journals at each end of the roller. However, when narrow webs are being used it is often the case that a single load cell is employed within a specially designed cantilevered roller.
The force applied to the measuring roller by the tension in the material web is measured and fed back to the controller.
The Controller is a device which carry out the following operations: –
Receive the load cell inputs, which will be in normally measured in mV DC and amplify them amplify them to a 0 – 10 v DC range. The input voltages from each of the two load cells are then averaged, to provide accuracy, especially if the web is oscillating across the roller.