Converting and web handling · Buyer's guide
On an unwind or rewind, identify what measures tension, what sets it and what changes shaft torque or speed. This page follows load-cell and dancer arrangements, using PRE controller data and MAGPOWR installation guidance. Their individual components need a defined electrical and mechanical interface.
01
A load-cell loop compares measured web tension with a setpoint and adjusts a brake, clutch or drive. In a dancer loop, the mechanical loading establishes tension; position feedback adjusts the brake or drive to keep the dancer within its travel. The dancer stores or releases web length as line speeds vary. Open-loop radius-based torque control also exists; these two feedback arrangements are not an exhaustive list. [1] [2]
| Decision | Load-cell feedback | Dancer-position feedback |
|---|---|---|
| What is measured? | Reaction force at the measuring roller, converted to web tension using the installation geometry. [3] | Dancer position. A position signal alone is not a direct tension measurement. [2] |
| What establishes tension? | Controller tension setpoint and the complete calibrated measurement loop. [1] | Applied dancer load and the mechanical geometry; dynamic forces disturb the ideal balance. [2] |
| What must the actuator do? | Change braking/clutch action or drive command to correct the tension error. [1] | Correct the web-speed mismatch so the dancer returns toward its target position. [2] |
| Where does setup matter? | A changing wrap angle changes force sensitivity even at constant web tension. [3] | Arm geometry, loading, inertia and friction determine how motion affects tension. [2] |
02
The component reference below distinguishes the force-sensing arrangement from the optional dancer arrangement. It is not a model-specific manufacturing BOM, and it does not imply that every item is supplied with a controller.
| Component / BOM reference | Function in the loop | Construction and order boundary |
|---|---|---|
| Tension sensor and measuring roller | Web force loads the roller supports; the sensor converts the reaction into an electrical signal. MAGPOWR TS uses a full strain-gauge bridge. [3] | PRE describes LX housings as aluminium or steel according to rating. Its illustrated sensor principle conflicts with the text; obtain the exact model sheet. Neither description establishes a universal stainless-steel construction. [4] |
| Controller / signal interface | Accepts the selected sensor input, compares feedback with its target and sends a correction to the actuator. [1] | KTC-828A is a controller example, not the complete mechanical assembly. Its embedded table gives selectable input variants, but the page does not identify the enclosure alloy. Select the exact input version. [1] |
| Brake, clutch or motor drive | Changes shaft torque or speed according to the selected winding arrangement. A pneumatic brake uses a pressure interface; a powder brake uses its specified electrical drive. [1] [2] | Do not assign ceramic/composite friction material to every actuator: the PRE example is for magnetic-powder units. Obtain the actual brake/clutch model, electrical requirements and duty limits. [1] |
| Dancer roller, arm, position sensor and loading device — when used | Stores web length; its load establishes tension while the position loop corrects the speed mismatch. [2] | The MAGPOWR constant-tension design uses low-friction pneumatic loading. A spring-loaded roller is not the universal default: spring force changes with position. The cited guide does not establish the arm material for an unspecified machine. [2] |
03
PRE identifies KTC-828A as a digital closed-loop controller for LX-series detectors. Its page contains a specification table and wiring drawings as images; these add important information absent from the running text. [1]
The LX text says metal-foil strain gauge, 10 VDC excitation, 16 mV full-scale output and 350 Ω bridge impedance. Its embedded illustration instead labels a KLX differential-transformer sensor with DC 5 V excitation and an amplified 0–5 V output. The illustration’s 50–1,000 N range cannot be transferred to an unidentified LX strain-gauge model. Require the exact sensor order code and controller input/wiring diagram before connecting them. [4]
MAGPOWR TS specifies nominal 21 mV per sensor at full rated load with nominal 10 V excitation, while PRE’s LX text gives 16 mV. Both numerical outputs fall within a ±30 mV input span, but that alone does not establish excitation, polarity, wiring or calibration compatibility. The cited TS manual does not qualify KTC-828A as a compatible controller. [3] [4] [1]
If a rewind requires tension to reduce as diameter increases, define the taper and its diameter reference. The MAGPOWR guide discusses changing the dancer load for taper; a constant-load unwind arrangement cannot simply be assumed to implement it. [2]
04
MAGPOWR’s TS manual calls for an unchanging wrap angle and a sensing direction aligned with the web-force resultant. Its mounting diagram and rated sensor load describe the support force, not a universal web-tension range. [3]
For equal tension T in both web spans and a freely turning ideal roller, R = 2T × sin(θ/2), where θ is the change in web travel direction around the roller. If using the angle φ between the outward-pointing tension vectors instead, R = 2T × cos(φ/2). Do not mix those angle conventions.
At T = 300 N, θ = 90° gives R ≈ 424 N; θ = 30° gives R ≈ 155 N. These are calculated roller resultants, not sensor ratings or measured performance.
Add the roller-weight vector and other relevant loads, then resolve forces along the sensing axis and calculate each support reaction. Weight may add to or oppose the web-force component. R/2 applies only to two supports sharing a centred, symmetric load; an offset web or cantilever needs its own balance.
Size the selected sensor for maximum support force, tare and anticipated transients, while retaining useful low-tension resolution. Overload stops do not expand its calibrated measurement range. [3]
The force equations and examples are editorial statics calculations with the assumptions stated above. MAGPOWR’s cited manual is 850A260-1, 10/04 Rev. D; verify the current drawing and availability for the ordered code. Its upload path is not a new revision date. [3]
05
MAGPOWR’s Figure 2 uses two parallel web spans pulling on the dancer. Its equation is 2T = L + Ma + Dv + Kx: applied cylinder load plus weight, inertial force, damping force and spring force. T = L/2 is the ideal quasi-static result when the additional terms are negligible. Different span angles or lever arms require the actual force and moment balance. [2]
For unstable tension, inspect free pivot/roller movement, loading pressure behaviour and web routing before adjusting the position loop. The primer’s detailed tuning example names MAGPOWR controls; its settings are not a KTC-828A procedure. For TS live-shaft and in-roll bearings, the sensor manual calls for periodic lubrication using its specified grease; do not label the complete installation maintenance-free. [2] [3]
06
A complete web-handling system has no single generic tension, speed, weight or protection rating. The fields below replace unsupported category-wide ranges with the conditions that the selected assembly must meet.
| Field | Unit or published basis | What belongs in the specification |
|---|---|---|
| Web tension | N total, or N/m of web width | State which quantity is controlled and give web width. Select sensor ratings from support reactions, not simply from the web-tension number. [3] |
| Tension accuracy | N or % with an explicit reference | Define steady and transient error over the required speed/diameter range. TS’s 0.5% F.S. nonlinearity/hysteresis limit is not ±0.5% of tension setpoint. [3] |
| Dynamic response | Time plus allowable deviation and test condition | PRE’s image table gives a 50 ms sampling interval, not a measured ≤50 ms tension-loop response. Specify the speed step, roll inertia, allowable deviation and settling criterion. [1] [2] |
| Line speed | m/min, with acceleration/deceleration | Supply the actual operating envelope; actuator capability and dancer dynamics must be assessed for it. No generic 10–500 m/min rating is supported. [2] |
| Electrical supply / command | Separate controller supply, sensor excitation and actuator outputs | The KTC-828A image table states 165–264 VAC, 50/60 Hz supply; its brake/clutch output is 0–24 V. The sensor excitation and tension input variant are separate interfaces. [1] |
| Power and actuator duty | Electrical power and rated torque / speed as applicable | Size the ordered actuator separately from controller electronics. Do not use the old 0.5–2 kW category range as a drive or brake rating. [1] |
| Operating temperature | Component-specific °C | TS manual: −30 to +90 °C. PRE’s LX text: −20 to +90 °C, subject to its unresolved model/illustration conflict. Neither is the complete cabinet or KTC-828A rating. [3] [4] |
| Ingress / environmental protection | IP designation for each supplied enclosure and sensor | PRE’s waterproof/dustproof wording does not provide an IP code. TS’s 3K3 climate class is not IP65. Obtain the relevant enclosure and connector ratings. [4] [3] |
| Materials | Housing, roller/web-contact surface and environment | LX text lists aluminium or steel housing according to load. It does not establish all wetted/contact materials, corrosion suitability or stainless steel for every component. [4] |
| Mass | Bare component and assembly masses, kg | PRE lists packed weights of 2 kg/controller and 4 kg/pair of LX sensors. These do not establish net mass or installed assembly weight. The controller packing dimensions also need reconciliation with the larger mounting drawing; obtain a current shipping schedule. [1] [4] |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Supply scope: controller [ ] / sensors [ ] / brake or drive [ ] / dancer [ ]; quantity [ ] Web material, width and thickness: [ ]; total tension [N] or width-normalised tension [N/m]: [ ] Unwind / intermediate / rewind position: [ ]; minimum / maximum roll diameter: [ ] Line speed, acceleration/deceleration, roll mass/inertia and splice sequence: [ ] Feedback: load cells [ ] / dancer position [ ]; web-path and support drawing attached [ ] Sensor order code, rated load, wrap-angle convention, roller mass and web offset: [ ] Sensor excitation, output sensitivity, wiring and controller input range: [ ] Actuator model, coil or drive input requirements, speed/torque mode and scaling: [ ] Dancer load, cylinder/regulator, span angles, lever arms and available travel: [ ] Taper requirement and roll-change behaviour: [ ]; communication/register map: [ ] Steady/transient tension acceptance test and calibration records: [ ] Ambient conditions, enclosure protection, materials and installation dimensions: [ ] Destination, delivery date and supplied manuals: [ ]
These companies publish different parts of a web-handling system. A component listing does not establish a tested, mutually compatible package; specify the interfaces and acceptance duty for the actual order.
Publishes KTC-828A controllers and LX foot-mounted detectors, with powder-brake/clutch and drive outputs. Its LX text and embedded KLX drawing conflict, so require a matched input/sensor specification before ordering.
Product scope checked 2026-10-10
LX sensor and interface conflict ↗
Publishes ZMZL web-tension load cells. The feature list gives nickel-plated alloy steel with stainless steel as an option, while the introduction describes stainless construction; specify the ordered material. This is a sensor offering, not evidence of a complete controller/brake package.
Product scope checked 2026-10-10
The tension-control catalogue includes LS400 through-axis sensors, TIR2020 air-pressure regulators, magnetic-powder brakes/clutches and shaft supports. Match the selected components; the category also contains web-guiding equipment, which controls lateral position rather than replacing a tension loop.
Product scope checked 2026-10-10
Publishes the EM610 tension-control VFD with closed-loop speed, open-loop torque, closed-loop torque and constant-linear-speed modes. It is a motor drive; selecting a mode and signal interface is separate from buying a powder-brake controller.
Product scope checked 2026-10-10
Lists STC-858A automatic and STC-002 manual controllers, LS/LC detectors and LB sensor rollers. The STC-858A description specifies 0–24 V clutch/brake output and 0–5 V servo torque command; these are not PRE’s output specifications. Confirm the actual model package.
Product scope checked 2026-10-10
Group entities and contact offices ↗
Identifies XW Machinery as a brand of Dongguan Xiangwang Machinery Parts Co., Ltd. and lists magnetic-powder brakes/clutches, air shafts and tension-control solutions. The homepage establishes its stated offering; request the specific controller/sensor data before treating it as a selected system.
Product scope checked 2026-10-10
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
For the primer’s ideal two-parallel-span balance, with negligible inertia, damping and spring-force contributions, T = L/2. L includes the specified loading and weight contribution. Other span angles, lever arms or dynamic conditions require their actual balance. [2]
Only when two supports share a centred, symmetric load. Resolve roller weight, sensing-axis direction and support reactions for the actual web position. The wrap-angle formula assumes equal tension in both spans and must use the stated angle convention. [3]
PRE lists made-to-order ±30 mV, ±300 mV or ±5 V inputs. LX text gives 16 mV full scale; TS gives nominal 21 mV at nominal 10 V excitation. An input-span match alone does not prove compatibility. PRE’s embedded KLX illustration shows another sensing interface, so match the exact order codes, excitation, wiring and calibration. [1] [4] [3]
For the primer’s constant-tension arrangement, damping adds a motion-dependent force and can conceal the underlying tension disturbance. Check inertia, friction, air loading and loop behaviour first; use the machine designer’s validated solution rather than copying another controller’s tuning. [2]
Sources checked 2026-10-10. Standards bodies and regulations define the requirements; manufacturer pages show published ranges for those models only. CNFX does not certify products or suppliers.
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