Linear Actuator Selection Guide: Load, Stroke and Speed Calculation

Why does picking the right linear actuator matter?

A linear actuator is the critical component that defines the basic kinematics of a machine through its push/pull force and travel range. The wrong choice does not just affect the initial investment — it has a serious impact on total cost of ownership through service life, energy consumption and downtime. In this guide we examine five critical criteria — load, stroke, speed, IP class and control interface — with field examples.

1. Load analysis: separate static, dynamic and peak values

A common mistake when choosing maximum thrust is mixing static and dynamic loads. Static load is the force the actuator must hold at rest; dynamic load includes the additional forces during acceleration and direction changes. A safety factor of 1.5× over dynamic load is recommended in the field.

Practical formula

F_select ≥ (m × g + F_friction + m × a) × 1.5. Here m is mass, g is gravity (9.81 m/s²), and a is maximum acceleration. In industrial applications a is typically 0.5-1 m/s².

2. Stroke calculation: useful travel and mechanical tolerance

Stroke is the difference between the shortest and longest position of the actuator. A minimum 10% mechanical tolerance should be added on top of the useful travel. This tolerance is required so end stops can absorb impact loads and so thermal expansion does not push the system out of range.

3. Speed profile: constant velocity or ramp?

A constant-velocity profile is sufficient for conveyors and positioning; precise positioning for robotics or medical applications requires a ramp (soft-start/soft-stop) profile. The Hedron HDR-LA series ships with ramp-capable controllers as standard.

4. IP class: classify the environment correctly

IP65 provides high dust protection and protection from low-pressure water jets; IP66 protects against strong jets; IP69K covers high-pressure hot-water washdown. Minimum IP67 is recommended for agriculture and food lines; IP69K for industrial cleaning environments.

5. Control interface: open loop or closed loop?

A potentiometer open-loop suffices for simple position control; hall sensor or encoder feedback is essential for repeatable precise positioning. For projects with Modbus, CANopen or 4-20 mA, drive-compatible variants should be preferred.

Summary checklist

• Have you calculated maximum load and applied a safety factor?
• Does the stroke add 10% tolerance to the useful travel?
• Does the speed profile match the application (constant / ramp)?
• Is the IP class adequate for the environment?
• Is the control interface compatible with your drive and PLC?

The Hedron engineering team prepares a project-based sizing report based on actual load, stroke and environmental data from your project. Contact us via the form for details.