Zone boundary
Identify the nipped or driven elements that isolate the unwind, process or rewind span. A controller cannot create a separate tension zone if the web path does not mechanically isolate it.
Resources / Choose a Tension Controller
How to Choose a Web Tension Controller
Choose the control architecture before choosing the controller model. Define the machine zone, feedback method, actuator or drive command, sensing range, interfaces and acceptance conditions so the shortlist matches the real web path.
Tension controller selection guide
Specify the control problem before the controller model
A usable specification connects the web zone, feedback architecture, actuator, signals and measurable commissioning targets.
1. Define the machine zone and control objective
Start by marking the controlled web span and the driven or resisting element that can change its tension. Siemens distinguishes a winder axis, where roll diameter changes, from a sectional tension-control axis without that changing-diameter dependency. That distinction affects the speed, torque and diameter information the controller may need.[1]
Control objective
State whether the task is to hold measured web tension, hold dancer position, calculate an indirect torque command, or provide a manual output.[1][2]
Operating cases
Record what must be acceptable at startup, acceleration, steady speed, deceleration, splice or roll change instead of specifying only one normal running point.
2. Choose the feedback architecture
The feedback architecture determines what the controller actually knows. An indirect or open-loop method does not use measured web tension as feedback. Load-cell control measures web tension directly, while dancer control normally regulates dancer position and relies on the dancer mechanics to establish the resulting tension.[1][2]
Indirect or open-loop
Use the machine model to calculate a command without direct tension feedback. On a centre-driven roll, diameter, gear ratio, friction and acceleration compensation can materially affect the result.[1][2]
Load-cell feedback
Use a force-measurement device when the controller must compare actual web tension with a setpoint and correct the command from that measured value.[1][2]
Dancer feedback
Use position feedback when the machine includes a dancer assembly and the control task is to maintain its position. Travel, applied force and mechanical geometry remain part of the tension system.[1][2]
Do not treat automatic closed-loop control as a universal upgrade. The correct choice depends on whether the machine can supply useful feedback, whether its mechanics support that method, and whether the resulting complexity is justified by the acceptance criteria.[1][2]
3. Match the output to the actuator or drive
A feedback sensor does not determine the complete control method. Rockwell documents distinct implementations for dancer position with speed trim, load-cell tension with speed trim, load-cell tension with torque trim, and open-loop torque. Its centre-winder application also requires a drive with torque-control capability when that architecture is selected.[2]
- Identify the existing actuator: pneumatic brake, magnetic-particle brake or clutch, motor drive, or another device.
- Confirm whether the drive accepts torque control, a speed-trim command, or only a speed reference; do not assume those interfaces are interchangeable.[1][2]
- Record the available analog or digital signal ranges, PLC communication, enable and alarm signals, electrical supply and isolation requirements.
- Confirm command direction, minimum and maximum output, fail-safe behaviour and whether a separate power amplifier or current driver is required.
4. Size the feedback range and installation
Load-cell selection is not based on target web tension alone. Maxcess's GTS manual sizes its specific load cells from maximum tension, sensing-roll weight and web-path angles, then requires a rating above the calculated load. The exact equation is product-specific, but the example shows why the real mounting geometry must be included in the sensor specification.[3]
- Record minimum, normal and maximum running tension, plus any temporary peak that the machine is intended to withstand.
- Provide the sensing-roll weight, wrap angle, mounting orientation and whether one or two load cells support the roll.[3]
- Check the chosen sensor manufacturer's sizing method and overload limits rather than copying a rating from a different load-cell family.[3]
- Match the sensor output and required signal conditioning to the controller input, and reserve suitable mechanical travel and position sensing for a dancer system.[1][2]
5. Use a controller selection worksheet
Use the following as a KRD engineering scoping worksheet. It organizes the inputs needed to compare controller families, but it does not replace machine drawings, safety review, sensor sizing or on-machine commissioning.
- Draw the web path and label the controlled zone, driven rolls, nip points, unwind, process and rewind sections.
- Record material, width, thickness, elasticity or stretch sensitivity, target tension range and full line-speed range.
- Record core diameter, maximum roll diameter, roll weight or inertia, winding direction and acceleration or deceleration requirements.[1]
- Choose the proposed feedback architecture and document the available load cell, dancer, diameter or line-speed signals.[1][2]
- Document the brake, clutch or drive model, supported control mode, command range, PLC interface and available cabinet space.[2]
- Define measurable acceptance cases for startup, steady production, speed changes and roll changes using the actual production material.
New machine
Specify the controller together with the sensor, actuator, drive mode and mechanical web path so the interfaces are designed as one system.
Retrofit
Verify what the existing drive or brake can accept, where feedback can be installed, and which present problems are mechanical rather than controller-related.
Controller replacement
Record every old terminal and signal function before selecting a replacement. Matching the supply voltage or panel cut-out alone is not sufficient.
6. Build a KRD shortlist after the specification
After the worksheet is complete, compare KRD automatic, semi-automatic and manual controller families against the required feedback and output method. Use individual product pages to confirm model-specific inputs, outputs and supported actuators; the article is a selection workflow, not a substitute for the current product specification.
- For measured-tension control, shortlist the controller and load-cell system together, including signal conditioning and mounting geometry.
- For dancer control, confirm the position-sensor signal, travel, force mechanism and whether the selected controller supports the intended drive or actuator command.
- For indirect or manual control, document how diameter, speed, torque or operator settings will change across the full roll and production cycle.[1][2]
Send KRD the completed worksheet, web-path drawing, control-cabinet information and clear photos of the proposed sensor and actuator locations. KRD can then narrow the product family for a further engineering review.
Sources & References
- Siemens AG. SIMATIC Winder and Tension Control Back
- Rockwell Automation. Drive Application Software - Tension Control Function Module Back
- Maxcess International. MAGPOWR GTS, GTSA, GTSB Load Cell User Manual Back
FAQ
What information should I provide before selecting a tension controller?
Provide the web-path drawing, controlled zone, material, width and thickness, target tension range, full speed range, core and maximum roll diameter, existing brake, clutch or drive, available feedback and command signals, cabinet power, and measurable acceptance cases.
Can one tension controller handle several materials?
Possibly, but the controller, sensor range, actuator and tuning must cover every intended material and operating condition. If stored parameter sets are required, confirm that function on the exact controller model and validate each recipe on the machine.
Can any load cell be connected to any tension controller?
No. Check the load-cell rating, mechanical geometry, output type, excitation or amplifier requirements, number of sensors and the controller's supported input range. Size the sensor with the chosen manufacturer's method.
Can an existing brake, clutch or drive be reused with a new controller?
It may be reusable only after its command type, voltage or current range, power stage, control direction, operating limits and fail-safe behaviour are matched to the new controller. A drive must also support the control mode required by the selected architecture.
Ask KRD to review your tension-control specification
Send the web-path drawing, material and tension data, roll sizes, line speed, existing actuator or drive, available feedback and I/O, plus the operating cases that must be verified. KRD can help narrow the controller, sensor and interface shortlist for engineering review.