Chase/Follow

Chasing systems move heavy machinery (slitter bases, coating heads) rather than lightweight web rollers. This imposes strict mechanical requirements:

1. Structural rigidity: The carriage must be stiff enough that its natural frequency exceeds the control frequency (typically >25-50Hz). If the sensor bracket wobbles, it creates "false error" and causes oscillation.
2. Breakaway force: The actuator must overcome static friction in the linear bearings. Roll-2-Roll® Actuators provide up to 2,000 lbf (8,900 N) thrust.
3. Acceleration over speed: The actuator must change direction fast enough to match web error rates. Speed alone won't help if the carriage can't accelerate quickly.

Rule of thumb: If the system oscillates or hunts, check carriage rigidity first—it's the most common cause of chasing failures.

In chasing applications, process upsets can cause the web to wander significantly—due to splice passage, tension changes, or roll eccentricity. This exposes a critical weakness in narrow-range sensors:

• Narrow sensor problem: If the target (line, edge, or pattern) moves outside the sensor's field of view, the system loses tracking. With older controllers lacking edge-loss protection, the actuator continues driving in one direction until it reaches its limit—potentially damaging equipment or producing scrap.
• Roll-2-Roll® Sensors + SCU5/SCU6x advantage: Wide-range sensors (up to 960mm) provide a large capture window that maintains lock on the target during extreme wander events. Additionally, the SCU5 and SCU6x controllers include a "Lock on Lost Edge" feature that inhibits actuator movement if the edge is lost—preventing runaway conditions. For line/contrast guiding, loss of contrast also inhibits the actuator.

Example: An ODC 288 sensor provides 288mm of sensing range. If the web edge wanders ±100mm during a splice, the sensor never loses sight of it—and the controller keeps tracking smoothly.

In Li-Ion battery electrode coating, the coating must align precisely with the current collector foil. Steering the foil creates stress and wrinkles that cause defects. Instead, Roll-2-Roll® Sensors enable coating head chasing:

• Sensor placement: ODC 96 or similar mounts directly on the coating carriage
• Edge tracking: The sensor continuously monitors the foil edge position
• Dynamic alignment: If the foil drifts, the coating head moves to follow—maintaining bead position within ±0.1mm

The benefit: No mechanical stress on the foil, no wrinkles, no electrode misalignment. This is critical for preventing lithium plating defects in finished cells.

In slit-to-feature applications, the cut must align with artwork or a printed line on the web—not the web edge. Roll-2-Roll® Sensors enable this through dynamic tool tracking:

1. Sensor mounting: The ODC 96 or ODC 192 sensor attaches directly to the knife holder bracket
2. Target acquisition: The sensor locks onto the printed line, coating edge, or contrast feature
3. Chasing: As the feature wanders, the controller drives the knife carriage laterally until the sensor re-aligns—maintaining ±0.0635mm registration

Why this matters: Print position varies relative to web edges due to registration error at the press. Standard edge guiding cannot solve this—the slitter must chase the print.

Standard web guiding steers the web to a fixed position, but in tool tracking applications like slitting to a printed line, the sensor must see the relative position between the tool and the web.

Here's why fixed sensors fail:

1. Fixed sensor upstream: The sensor sees web wander and commands the slitter to move—but it never sees the slitter move. The error signal remains, and the control loop is open.
2. Fixed sensor downstream: By the time you detect misalignment after the slitter, the cut has already happened. You cannot correct a cut that's already made.

The only solution is to mount the sensor on the moving tool carriage. When the carriage moves, the sensor moves with it, verifying the correction. This closes the feedback loop and enables true chasing.

No. Roll-2-Roll® Sensors are available in apertures from 48mm to 960mm, allowing a single sensor to accommodate a wide range of web widths without repositioning.

For example, an ODC 288 sensor can detect edges anywhere within its 288mm (11.3 in) sensing range. Whether you're running a 100mm web or a 250mm web, the sensor detects the edge without adjustment.

This eliminates:

• Changeover time: No 2–5 minute delays for sensor repositioning between SKUs
• Operator error: No risk of incorrect sensor positioning
• Motorized positioners: No additional hardware cost or maintenance

Combined with material-agnostic detection (no recalibration between clear films, opaque substrates, or metallic foils), Roll-2-Roll® Sensors enable true "set and forget" operation.

Telescoped (uneven) roll edges typically result from:

• Response lag: Hydraulic systems have inherent lag from valve response and fluid compressibility. By the time the guide reacts, the web has already wandered.
• Valve balancing issues: Unequal extension/retraction speeds cause inconsistent correction.
• Improper sensor mounting: If the sensor is fixed to the floor instead of the moving stand, or if the mounting arm is flexible, the system receives incorrect position feedback.

The Roll-2-Roll Technologies solution:

• Zero-backlash actuators: Electromechanical actuators respond immediately without the "spongy" feel of hydraulics
• Stiff control loop: Fast response prevents lag-induced wander, especially on outer roll layers
• Proper mounting guidance: Sensor on the moving stand, observing web at a fixed upstream idler, with structurally rigid mounting

The result is perfectly straight-sided rolls without the "drift" that causes telescoping during shipping and handling.

Yes. The SCU5 and SCU6x controllers can process two sensors simultaneously with independent enable/disable control. This is ideal for bidirectional coating machines that run forward and backward between passes.

Typical dual-sensor configuration:

• Sensor 1: Mounted on the rewind moving frame—enabled during forward winding
• Sensor 2: Mounted on the fixed machine frame—enabled during reverse (unwind) direction

Instead of repositioning a single sensor when direction changes, operators simply switch which sensor is active via the controller touchscreen or a PLC command over EtherNet/IP, PROFINET, or EtherCAT.

This eliminates sensor repositioning time, enables instant direction changes, and simplifies machine design by removing the need for motorized sensor positioners.

Roll-2-Roll Technologies rewind guides use electromechanical actuators (RLA and BLA series) instead of traditional hydraulic cylinders. This completely eliminates:

• Hydraulic fluid—no oil to leak, change, or dispose of
• Filters and seals—no consumables to replace quarterly
• Valve balancing issues—no unequal extension/retraction speeds
• Contamination risk—critical for food, pharmaceutical, and medical applications
• Hydraulic pumps—quieter operation without pump noise

Typical plants using hydraulic systems report spending 10–20 hours annually on rewind guide maintenance alone. Electromechanical systems reduce this to near-zero, with only periodic inspection required.

The SCU6x controller includes an integrated motor driver, eliminating the need for separate drive cabinets and simplifying installation.

Roll-2-Roll Technologies electromechanical rewind guides can handle loads up to 30,000 lbs (13,600 kg) when paired with low-friction linear rail bearings (coefficient ~0.01).

Key specifications:

• Maximum thrust: 50–1,500 lbf (222–6,670 N)
• Stroke length: 1–12 in (25–300 mm)
• Maximum speed: Up to 2 in/sec (51 mm/sec)

The critical factor for sizing is breakaway force—the static friction the actuator must overcome to start moving the loaded stand. Using low-friction linear rail bearings dramatically reduces the required actuator size compared to sliding shaft designs (coefficient ~0.25).

For extremely heavy loads, the RLA Series ball screw actuators provide thrust up to 1,500 lbf while maintaining precision positioning.