Web Guiding

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.

Roll-2-Roll Technologies electronic Master/Slave guiding eliminates the mechanical components that require constant maintenance in legacy systems:

Eliminated maintenance items:

• Motorized sensor positioner motors and drives
• Lead screws and anti-backlash nuts
• Sliding brackets and linear bearings
• Mechanical linkages between Master and Slave positions

What remains: Standard periodic inspection of sensors and guides—the same maintenance as any web guiding system, without the additional burden of sensor positioning hardware.

Typical customers report saving 10-20 hours annually in maintenance time previously spent on mechanical positioner systems.

Yes. Roll-2-Roll Technologies systems support multi-lane cascading alignment where each lane's edge position automatically sets the guide point for the next lane.

Example configuration (14 lanes):

• Each lane has two sensors: one monitors the "master" edge, one guides the web via a slave guide
• Lane 1's right edge position sets the guide point for Lane 2's slave guide
• Lane 2's right edge sets Lane 3's guide point, and so on
• Result: All lanes maintain edge-to-edge alignment automatically

For faster response: The SCU6x controller's industrial Ethernet connectivity enables a central PLC architecture where any lane change can instantly adjust guide points for all subsequent lanes simultaneously, rather than propagating lane-by-lane.

In Master/Slave guiding, timing is critical. The Slave guide must correct for a Master web movement at the exact moment that movement reaches the lamination nip.

The rule: Web path distance from Master Sensor → Lamination Nip should equal the distance from Slave Sensor → Lamination Nip.

Why it matters: If paths are unequal, the Slave might correct too early or too late (phase mismatch), causing misalignment at the actual lamination point.

The fix: If physical constraints prevent matching path lengths, Roll-2-Roll® Controllers can apply dynamic compensation—electronically delaying the feed-forward signal to match the transport time difference.

Both SCU5 and SCU6x controllers support two independent sensor channels, enabling single-controller Master/Slave configurations:

• Channel 1: Master sensor (monitors reference web position)
• Channel 2: Slave sensor (provides feedback for the guided web)

For multi-slave applications (3+ webs), the Master signal can be broadcast to multiple Slave controllers via industrial Ethernet (EtherNet/IP, PROFINET, EtherCAT, or Modbus/TCP). This enables scalable synchronization—one Master can drive any number of Slaves without mechanical complexity.

Yes. This is a unique capability of Roll-2-Roll Technologies Master/Slave guiding that legacy systems cannot match.

By using wide field-of-view sensors (ODC 480, ODC 768, or ODC 960) that see both edges of each web simultaneously, the controller can calculate the centerline of both the Master and Slave webs. It then guides the Slave web so its center aligns with the Master's center.

Key benefit: When web widths change, the centerline matching adjusts automatically. Operators no longer need to recalculate and enter new offset values—a tremendous time saver that eliminates a major source of alignment errors.

Example: A 400mm Master web and 350mm Slave web will automatically center-align without any manual intervention.