Web Tension Control: Tension Range, Control Methods and Configurations
A web tension control system holds the longitudinal force on a moving web at a set value while the roll diameter, line speed and material change. This page lists the measurable specifications of the tension controllers, tension sensors and magnetic powder actuators manufactured by XW Machinery, explains the three control methods used on converting lines, and gives three typical configurations with their tension ranges.
If you need the concept first, read What Is a Web Tension Control System?. If you need the lateral alignment side of the specification, see Web Guiding Systems: Specifications and Model Selection.
Tension Control Specifications at a Glance
| Parameter | Specification | Model |
|---|---|---|
| Control method | Automatic closed loop with non-overshoot PI algorithm; manual constant-current open loop on micro controllers | TC-860, TC-200 |
| Torque range, standard magnetic powder units | 6 N.m to 400 N.m | Standard clutch and brake range |
| Torque range, micro units | 1 N.m to 5 N.m | 12 V micro clutch, 24 V micro brake |
| Controller range designation | 1000 N.m | KDT-C-1000 |
| Main output | 2 x 24 V / 4 A constant-current channels | TC-860, KDT-C-1000 |
| Auxiliary output | 2 x 0-10 V; or 1 x 0-5 V configurable to 0-10 V | TC-860, KDT-C-1000 |
| Sampling cycle | 50 ms | TC-860 |
| Conversion accuracy | 1 LSB, 16-bit A/D conversion | TC-860 |
| Sensor input range | 30 mV or 300 mV standard; 5 V input customizable | TC-860 |
| Controller power supply | AC 165-264 V; or AC 180-245 V; or 12 V / 24 V DC excitation for micro units | TC-860, KDT-C-1000, TC-200 |
| Communication | RS485 / Modbus-RTU, register map 0x00 to 0x19 | TC-860, KDT-C-1000 |
| Roll change control | Dual-station switching with adjustable shaft-change output ratio, standby output | KDT-C-1000, TC-860 |
| Measurement structure | Cantilever flange mount, pillow block foot mount, through-shaft | Tension sensor range |
| Sensor output signal | mV/V strain gauge output | Through-shaft sensor |
| Protection class | IP54 / IP65 | Through-shaft sensor |
How Tension Range Is Derived
Tension is not set directly by the controller. On a winding or unwinding station the controller sets torque on a magnetic powder clutch or brake, and the resulting web tension follows from the roll radius:
Web tension (N) = Torque (N.m) / Roll radius (m)
This is why the usable tension range of a zone depends on both the torque range of the actuator and the roll diameter range of the machine. A 6 N.m to 400 N.m magnetic powder brake does not deliver one fixed tension value: at a 0.05 m core radius the same torque produces far more tension than at a 0.4 m full-roll radius. Size the actuator across the full roll, not at the setpoint alone.
Practical consequence: the maximum torque required is set by the full roll diameter and the maximum tension the material tolerates, while the minimum controllable torque is set by the core diameter. Specify both numbers before ordering.
Three Tension Control Methods
1. Open Loop: Manual Constant-Current Control
The operator sets the output level and the controller holds excitation current constant. There is no tension feedback, so tension drifts as the roll diameter changes. This method suits short runs, simple machines and low-tension light webs where cost and simplicity matter more than repeatability.
- Hardware: TC-200 Micro Tension Controller with a 12 V micro magnetic powder clutch or a 24 V micro magnetic powder brake
- Torque range: 1 N.m to 5 N.m
- Typical use: labels, small rewinders, light web and compact machines
2. Closed Loop: Automatic Control with Sensor Feedback
Tension sensors or load cells feed actual tension back to the controller, which continuously compares measured tension with the target and adjusts output. This is the standard method for production lines where tension stability affects registration, winding hardness or material stretch.
- Hardware: TC-860 Automatic Tension Controller or KDT-C-1000 Automatic Tension Controller with cantilever, pillow block or through-shaft tension sensors
- Features: 50 ms sampling, 1 LSB conversion accuracy, non-overshoot PI algorithm, zero and full-scale calibration
- Typical use: slitting, rewinding, printing, laminating, coating, lithium battery roll-to-roll
3. Dancer Control
A dancer roller provides mechanical tension storage and is often combined with a closed-loop controller on lines with frequent speed changes or splices. XW Machinery supplies the controller and sensor side of these systems; dancer mechanics are built by the machine builder. See Open Loop vs Closed Loop Tension Control for a full comparison.
Three Typical Tension Control Configurations
Configuration A: Light Web, Low Tension
TC-200 Micro Tension Controller driving a 12 V micro magnetic powder clutch (1-5 N.m) or a 24 V micro magnetic powder brake (1-5 N.m). Manual constant-current output, no intermediate power amplifier required on micro and small frames.
- Torque range: 1 N.m to 5 N.m
- Control method: manual, open loop
- Add a tension sensor and an automatic controller to upgrade to closed loop
Configuration B: Standard Single or Dual Station Winding and Unwinding
KDT-C-1000 Automatic Tension Controller with two 24 V constant-current outputs driving magnetic powder clutches and brakes directly, paired with cantilever tension load cells for feedback. Dual-station switching with an adjustable shaft-change output ratio reduces tension shock during roll changeover.
- Controller range designation: 1000 N.m
- Outputs: 2 x 24 V constant current, 1 x 0-5 V auxiliary configurable to 0-10 V
- Power: AC 180-245 V; RS485 supported; limit output relay supported
Configuration C: Multi-Zone High-Specification Control with PLC Integration
TC-860 Automatic Tension Controller with through-shaft tension detectors or pillow block tension transducers. Dual 24 V/4 A main outputs drive the magnetic powder units while dual 0-10 V auxiliary outputs connect to inverters, servo drives or external control systems.
- Processor: 32-bit high-speed CPU, 50 ms sampling, 1 LSB conversion accuracy
- Inputs: 30 mV / 300 mV standard, 5 V customizable
- Communication: RS485 / Modbus-RTU, register map 0x00 to 0x19
- Power: AC 165-264 V wide range
How to Choose a Tension Sensor
- Cantilever load cell: flange-mounted structure, easy installation, low temperature drift, high overload protection. See the Cantilever Tension Load Cell.
- Pillow block transducer: foot-mounted under the bearing housing, higher load capacity and structural stability for wide-web and high-speed lines. See the Pillow Block Tension Transducer.
- Through-shaft sensor: direct force transmission through the roller shaft, mV/V output, IP54 / IP65 protection. See the Through-Shaft Tension Sensor.
Read How to Choose a Web Tension Sensor for the full selection procedure, and How to Choose a Tension Controller for controller selection.
Frequently Asked Questions
What tension range can XW Machinery supply?
Tension depends on torque and roll radius. The magnetic powder clutch and brake range covers 6 N.m to 400 N.m on standard units and 1 N.m to 5 N.m on micro units. Send your maximum roll diameter, core diameter and target tension and we calculate the required torque range for each zone.
What is the difference between open loop and closed loop tension control?
Open loop estimates tension from a manually set output and does not correct for roll diameter change. Closed loop uses actual feedback from tension sensors or load cells and regulates output automatically, giving higher accuracy and stability. See Open Loop vs Closed Loop Tension Control.
Can one controller drive two actuators?
Yes. Both the TC-860 and the KDT-C-1000 provide two independent 24 V main output channels, which suits machines with two controlled tension actuators or dual-shaft winding and unwinding structures.
Can the controller integrate with a PLC?
Yes. RS485 / Modbus-RTU communication is available, with a defined register map from 0x00 to 0x19 on Modbus-enabled TC-860 configurations.
Why does tension change during rewinding?
Roll diameter, speed, roll changeover and material behaviour all affect tension. See Why Web Tension Changes During Rewinding and Unstable Web Tension: Causes and Solutions.
Get a Tension Control Configuration for Your Line
Send your material, web width, roll diameter range, line speed, target tension and number of control zones, and our engineering team will recommend a controller, sensor and actuator set with parameters and a wiring diagram. Complete the product requirements survey, or browse the full web tension control systems collection.