Unwind guiding

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.

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.

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.

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.

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.

Sizing an unwind actuator requires more than knowing the total load weight. The key factors are:

1. Breakaway Force: The actuator must overcome static friction to start movement. This depends on the bearing type:
   • Low-friction linear rail bearings (coefficient ~0.01): A 10,000 lb load requires only ~100 lbf to start moving
   • Sliding shaft bearings (coefficient ~0.25): The same 10,000 lb load requires ~2,500 lbf
2. Acceleration Requirements: Higher acceleration for faster response requires proportionally more thrust
3. Safety Factor: Include 20-30% margin for binding, misalignment, and wear

Recommendation: Always use low-friction linear rail bearings. The cost savings on a smaller actuator typically exceeds the bearing cost difference, plus you get better dynamic response.

Roll-2-Roll Technologies RLA and BLA series actuators provide thrust from 50 lbf to 2,000 lbf, handling loads up to 30,000 lbs when paired with proper bearing systems.