How to Select a Web Guide Actuator for a Retrofit

1. Define what the actuator must move

Begin with the correction mechanism rather than an actuator model number. Nireco's guide-roll selection guidance treats web material, width, tension, required correction, speed and machine installation conditions as connected inputs, and distinguishes center-pivot from end-pivot arrangements.^[1]

For a retrofit, record whether the actuator shifts an unwind or rewind stand, moves a guide frame, pivots a steering assembly, positions a sensor, or performs another defined motion. Include the moving mass, support arrangement, motion direction, available space and the process section that must receive the corrected web.

2. Specify usable stroke and the neutral position

Nominal actuator stroke is not, by itself, a retrofit specification. RE's WG pivoting-frame technical table presents actuator stroke and speed together with roll length and maximum web tension across different guide sizes, showing that travel belongs to a mechanism-level selection rather than an isolated actuator label.^[2]

1. Measure the existing mechanism at its neutral position and at both permitted correction limits.
2. Record the normal web-position error band separately from the maximum mechanical movement available.
3. Identify hard stops, sensor range, cable movement, bearing travel and any structure that limits safe usable motion.
4. Confirm how the retained or proposed controller establishes centre, home and travel limits for the selected feedback method.^[5]

Do not add an arbitrary stroke allowance or assume the full catalogue stroke can be used on the machine. Final travel must be checked against the real geometry, permitted mechanism movement and controller configuration.

3. Match thrust, speed and response to the mechanism

Actuator data should be reviewed as a set, not as one headline value. BST's actuator brochure describes combinations of actuation path, force and speed, with or without position feedback, while KRD's PD series selection page organizes models by stroke, thrust, drive load and maximum drive speed.^[3][4]

The output is a matched operating point, not a claim that the actuator's maximum thrust, maximum speed and full stroke are simultaneously available or appropriate. Use the selected model's approved data and application review for the final combination.

4. Verify controller, feedback and commissioning interfaces

The actuator cannot be approved independently of its control interfaces. RE's SmartMotion documentation combines motor and control electronics, calculates and controls actuator stroke with its display, and lists power, sensor inputs, remote-control inputs and fieldbus interfaces; those functions are specific to that product family and illustrate the interfaces a retrofit review must verify.^[5]

Erhardt+Leimer's DRS20 system data likewise places actuating travel and speed beside supply voltage, current, digital I/O and sensor measuring range. This supports reviewing mechanical travel, electrical interfaces and sensing as one matched system, without treating another manufacturer's values as KRD specifications.^[6]

• Controller and drive output type, supply voltage, motor type and permitted current or power.
• Encoder or position-feedback type, home or centre method, travel limits and required calibration procedure.^[3][5]
• Sensor type, control reference, polarity, correction direction and the retained PLC or machine interlocks.^[5][6]
• Connector, cable length, routing, enclosure, mounting orientation and environmental constraints.

Treat manufacturer procedures as model-specific references, not universal commissioning instructions. The responsible machine team must verify the approved wiring, settings, limits, guarding and restart behaviour for the actual retrofit.

5. Prepare the data package for KRD review

KRD's PD series page asks for required thrust load, stroke, speed, mounting space and web width when requesting actuator sizing support. A useful retrofit package adds the machine drawing, guide-mechanism photos, existing component model numbers, control diagram, operating ranges and the quality issue that the correction must address.^[4]

1. Machine and web-path drawing with the correction point, web direction and critical downstream process marked.
2. Material, web width and tension ranges, normal and maximum line speed, and observed lateral error.
3. Mechanism mass or load information, movement orientation, available stroke, mounting dimensions and current actuator photographs.
4. Existing controller, sensor, motor, feedback, power, wiring and PLC interface information.
5. Required operating modes, acceptance checks and the responsible engineering owner for final machine approval.

KRD can use this package to review whether a PD linear actuator, PG guide mechanism, integrated EPC unit or another matched arrangement is the appropriate starting point. Final compatibility, sizing, installation and commissioning remain machine-specific.