Redex Provides Trouble-Free Web Tension Systems with Load Cells

Precise web tension control is essential to achieving optimal converting performance across industries, including composites, wire and cable, textiles, packaging, labeling and finishing. Stable material flow, product quality and consistency, and machine efficiency depend on how well web tension is measured and regulated. Otherwise, issues like product deformation, web breaks and print misregistration can arise.

Measurement accuracy is critical for load cells used in web tension control applications. Redex has examined the critical load cell characteristics that contribute to measurement accuracy and optimal web tension system performance.

Web tension load cells feature the following:

Low deflection: Keeping materials on a precise path — without steering to one side, experiencing registration errors, suffering web breaks or stretching — is critical to maintaining product quality and process efficiency.

Cantilever designs: By eliminating errors caused by side loads or inconsistent web positioning, the load cell provides continuously accurate tension measurements.

Repeatability: Inconsistent web tension is usually a sign of trouble, either caused by the machine or the material itself. In a closed-loop system, a load cell with good repeatability allows operators to be confident that the controllers are making accurate adjustments.

Good signal integrity: Electromagnetic interference (EMI) often hinders the accuracy of feedback signals, leading to overcompensation from the controller.

One load cell series for web tension applications offers these advantages and more. Redex Group’s Merobel WAT+ transducers combine accuracy and design flexibility for a host of industries, such as composites, wire and cable, and textiles, as well as packaging, labelling and finishing equipment.

The series features a dual-beam design that resists side-loads and inconsistent web alignments to ensure strict tension control and measurement accuracy. The Cantilever Compensation Concept (3C) design maintains a constant measurement value over the full length of the roller. Thanks to the 3C design concept along with advanced research and finite element calculations performed on the internal structure of the transducer, the WAT+ family provides repeatable measurement values. The series achieves 0.5 or 0.3 percent accuracy full scale (FS), depending on the model and size.

The WAT+ family is highly modular, with a universal design that can accommodate many accessories, pulley or shaft configurations. The Size 1 modular package covers 50N-250N-500N (10-50-110 pounds), and Size 2 covers 1000-2500-5000N (225-560-1,125 pounds). The standard unit consists of four gauges, with an output signal value of ~2 mV/V.

One variant, the WAT+.sp, comes with an embedded signal amplifier that provides strong and highly reliable measurement signals which can also be directly transmitted to a programmable logic controller (PLC) or drive. Another variant, the WAT+.sl, can be integrated with another WAT+ on opposite sides of the roller to balance deflection and protect against misalignment or zero measurement drift issues.

WAT+ can be paired with the Merobel DGT300+ digital controller to create a precise, closed-loop tension measurement and regulation system. Supporting measurement feedback with load cells, DGT300+ features a built-in precision amplifier, automatic variable P.I.D. regulation function and dedicated web tension functions such as taper, inertia compensation, no stop and more. Advanced, user-friendly Microsoft software is provided for easy setting, and it also facilitates live acquisition recording.

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