Frequently Asked Questions

Unlike other forms of guiding, the goal is to align the rewind roll to the position of the incoming web, ensuring a straight wound roll.

Specific reasons for this configuration include:

• Chasing Control System: Rewind guiding is fundamentally a "chasing control system" rather than a lateral control system. The rewind stand must physically move to position the winding roll directly downstream of wherever the web happens to be.
• Maintaining Relative Position: If the sensor were fixed to the ground (as it is in unwind guiding), the system would not know the relative position between the winding roll and the incoming web. By attaching the sensor to the moving stand, the sensor moves with the carriage. When the sensor detects the web edge, the controller moves the entire stand (and the attached sensor) until the sensor is re-aligned with the web, effectively "chasing" it to maintain the correct relationship.
• Roll Alignment: This setup ensures that the edge of the rewind roll is constantly aligned with the edge of the approaching web, regardless of where the web is drifting laterally.

Ideally, this sensor should be located just ahead of the last fixed idler in the machine and as close to the winder as possible to minimize instability caused by the mechanical arm's stiffness.

In rewind chasing applications, the sensor must be mechanically attached to the shifting stand because the control system is designed to keep the sensor output at "zero." When the sensor moves with the roll, the system naturally drives the stand until the sensor aligns with the web edge.

If the sensor were fixed to the floor (like in intermediate guiding), the system would lose the relative position between the web and the roll face. The result would be telescoped or uneven rolls because the guide has no reference point for where the roll edge should be.

The sensor should observe the web at a fixed idler immediately upstream of the shifting stand. This provides a stable reference point while the stand—and sensor—move together.

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.

Unlike traditional sensors that require recalibration for each material type, Roll-2-Roll® Sensors use adaptive edge detection algorithms that automatically adjust to different material characteristics.

This eliminates:

• Manual gain adjustments
• Teach mode procedures
• Operator-dependent settings
• Extended changeover times

The impact: Plants using legacy sensors typically lose 2 hours monthly to recalibration—time that Roll-2-Roll Technologies technology completely eliminates.

Yes. R2R fiber-optic sensors detect edges on clear films (PET, BOPP, cellophane) as accurately as opaque materials. The light scattering technology responds identically to any material—no special settings or sensors required.

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.

The Roll-2-Roll® Controller includes Loss of Contrast Logic specifically for this situation. When the sensor encounters a gap where the tracked feature disappears (such as the space between labels), the web guide holds its current position. When the sensor sees the same feature again—matching the width and hue characteristics taught during setup—tracking resumes automatically. This prevents the "hunting" or crashing behavior common with traditional line sensors.

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.

The "fixed sensor rule" is fundamental to unwind guiding physics and is the opposite of rewind chasing:

The Logic: In unwind guiding, you are positioning the web to enter the machine at a specific target location. The sensor acts as that target. The controller moves the shifting stand until the web edge aligns with the fixed sensor position.

The Common Mistake: If you mount the sensor on the moving stand (as you would in a rewind chasing application), the sensor moves with the error. When the stand shifts left, the sensor shifts left too—so from the sensor's perspective, nothing has changed. The system cannot detect or correct the misalignment relative to the machine frame.

Proper Configuration:

• Sensor: Fixed to the machine frame (floor or fixed structure)
• At least one idler roller: Mounted on the shifting stand (moves with it)
• Sensor position: Immediately downstream of the shifting idler

This configuration ensures the sensor sees true web position relative to the machine, while the shifting idler maintains a consistent web plane as roll diameter changes.

Roll-2-Roll Technologies actuators are specifically designed for hydraulic cylinder replacement in unwind and rewind guiding applications:

What You Eliminate:

• Hydraulic fluid and the risk of product contamination from leaks
• Filter changes and fluid maintenance (typically 2-4 times per year)
• Seal replacement and valve rebalancing
• Hydraulic power unit (HPU) maintenance and energy costs

What You Gain:

• Clean, dry operation—critical for food, pharmaceutical, and medical applications
• Full thrust at zero speed (hydraulics struggle with static positioning)
• Smooth response at variable speeds without the "stick-slip" behavior of hydraulics
• Digital communication via EtherNet/IP, PROFINET, or EtherCAT for integration with modern PLCs

Retrofit Options:

• RLA Series: Rotary stepper with belt/pulley and ball screw, thrust up to 2,000 lbf
• BLA Series: Inline stepper with external ball screw for terminal guide applications

Most hydraulic retrofits can be completed in a scheduled maintenance window without major mechanical modifications to the existing stand structure.

Roll-2-Roll® Sensors are vacuum compatible and can detect clear films in vacuum environments. This is a unique capability that no other edge detection technology can match:

• Ultrasonic sensors cannot function in vacuum—no air means no sound waves for detection
• Many optical sensors struggle with clear films even in normal atmosphere

Roll-2-Roll Technologies fiber-optic technology solves both problems, making it the only solution for applications like:

• Glass manufacturing processes
• Vacuum coating operations
• Semiconductor manufacturing
• Specialty film production

No. With Roll-2-Roll® Sensors, you do not need to purchase or install a separate sensor for line/contrast guiding. The same ODC or 1DC sensor family handles edge detection, line guiding, center guiding, and contrast guiding. For most high-contrast applications, the standard infrared light source works for both edge and line detection. For low-contrast or UV-printed lines, white light or UV light source options are available.

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.

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.

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.

R2R edge guiding systems maintain ±0.1mm accuracy at speeds up to 500 meters per minute (1,640 fpm). With a 500 Hz update rate, the sensors respond fast enough for high-speed converting lines.

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.

Simply adjust the "guide point" on the SCU6x touchscreen. The sensor stays fixed—no mechanical repositioning required. Width changeovers take seconds, not minutes.

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.

Roll-2-Roll® Sensors provide true spatial awareness—not just binary on/off detection:

This accuracy is maintained across all material types without recalibration—critical for precision applications like battery electrode coating, optical film production, and high-speed converting.

Roll-2-Roll® Sensors can detect and track lines with a minimum width of 2 mm (0.08 in). The sensors also support negative space guiding—tracking the gap between printed features (such as the white space between labels) rather than a printed line. This eliminates the need to print a dedicated registration line, saving ink costs and allowing closer trim to printed edges.

The choice between edge guiding and line guiding depends on what defines "correct position" for your process:

Use Edge Guiding When:

• The physical web edge is your reference (e.g., die-cutting to edge, edge-aligned lamination)
• Material has consistent, clean edges
• Processing unprinted or solid-color materials

Use Line Guiding When:

• Processing pre-printed materials where print registration matters more than edge position
• Web edges are inconsistent (ragged, variable width) but printed marks are reliable
• Guiding to a coating edge rather than the substrate edge
• Running materials with printed registration marks or tracking lines

The Roll-2-Roll Technologies Advantage: With ODC 960 wide-aperture sensors, you can switch between edge and line guiding modes without changing hardware. This is particularly valuable for slitter rewinder applications that process both plain substrates (edge guide) and pre-printed materials (line guide) on the same machine.

The sensor automatically adapts to detect either the physical edge or a contrast line based on your selection in the SCU5 or SCU6x controller interface.

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.