The tension sensor was integrated into Maxes in 1996. Also known as a tension detector, the tension sensor is an instrument utilized in measuring the tension value of the web during the tension control process. Tension sensors are categorized into strain gauge type and micro-displacement type based on their operational principles.

The strain gauge type involves connecting tension strain gauges and compression strain gauges in a bridge manner. When subjected to external pressure, the resistance value of the strain gauge changes, and this change is proportional to the amount of tension. On the other hand, the micro-displacement type applies load through external force, causing displacement in the leaf spring, which is then detected to measure tension via a differential transformer. Given the minute displacement of the leaf spring, approximately ±200 μm, it earns the designation of a micro-displacement tension detector. Additionally, based on structural appearance, it is further classified as pedestal type, through-axis type, cantilever type, etc.

The tension frame applies a downward pre-tension force to itself via its own weight and spring tension. During operation, the tension frame is adjusted to a corresponding position that aligns with the set tension of the winding wire. This position, termed the reference position, serves as the center for swinging up and down during operation. Swinging upward increases tension, while swinging downward decreases tension.

Adjustments to the tension control signal are made based on the tension reference position signal. The tension input control signal is bifurcated into two signals: one being the tension position reference signal, which is the initial signal of the tension sensor when the tension frame is in its initial position. Its magnitude is preset to the frequency converter through the function code as per site conditions. The other signal is the tension dynamic signal, representing a change signal generated under the tension position reference signal. These two signals are superimposed and compared to produce an error signal. The error signal is processed by the PI controller to generate a tension frame position correction signal, which is then superimposed with the speed signal to produce an inverter frequency control signal.

A. Reasons for Maintaining Constant Tape Tension During Printing

When printing on web paper, maintaining constant tension of the paper tape throughout the printing process is imperative because:

1. Insufficient tension can result in issues such as paper tape loosening, wrinkles, and inaccurate registration.
2. Excessive tension increases machine load and stress on the paper tape, potentially causing breakage if it surpasses its strength limit.
3. Unstable tension can cause paper tape jumping, leading to problems like inaccurate overprinting and ghosting, particularly during machine start-up and shut-down, where unstable tension may cause paper breakage or jams.

B. Reasons for Unstable Paper Tape Tension During Printing

For paper feeders, the pulling force that propels the paper tape forward is typically generated by the printing cylinder. Reasons for unstable paper tape tension include:

1. The gradual reduction in size of the paper roll during the printing process, resulting in changes in resistance torque that affect paper tension.
2. Non-circular paper rolls or uneven paper, grooves in the printing cylinder, or other factors that cause fluctuations in paper tape tension.
3. Unstable machine dragging.

C. Solution

Install a tension control system in the paper feeding device to automatically adjust tension. Consistent tension is achieved through coordinated interaction between the paper roll drive and paper roll brake. The tension sensor converts tension into an electrical signal via the tension control system. Through the frequency converter, speed is controlled to achieve synchronization, reducing the likelihood of paper breakage. This feature is also one of the characteristics of our company's paper coating machine—setting tension sensor.