What is actuator stroke, and how do you calculate it?

Pneumatic cylinders are an integral part of many industrial automation systems, enabling precise linear motion in a variety of applications. One of the key parameters of these devices is stroke, which defines the maximum distance the piston can travel inside the cylinder.

What is an actuator stroke?

The stroke of a pneumatic actuator is a fundamental parameter that defines the distance the piston can travel inside the cylinder, determining the range of motion of the mechanism. It is the distance between the end of the piston rod in the retracted and extended positions.

The actuator stroke determines:

• the range of motion—the maximum distance the cylinder can move the load
• the distance the piston and piston rod can travel from the fully retracted position to the fully extended position

Selecting the appropriate actuator stroke

Properly determining the actuator stroke is critical to its efficiency and reliability in various industrial automation applications.

Determining the stroke is essential for:

• correctly selecting a replacement or original part
• replacing a damaged actuator or finding a replacement

How to calculate the actuator stroke?

Correctly determining the stroke is essential for properly selecting a cylinder, replacing it, or finding a replacement. There are several methods for measuring stroke that can be used depending on the availability and condition of the nameplate, the type of cylinder, and the measuring tools at hand. Below are the three most common methods for determining the stroke of a pneumatic cylinder.

Reading from the nameplate

The simplest way to determine the actuator stroke is to read this value from the nameplate located on the actuator. If the nameplate is legible, simply locate the stroke parameter, which is usually given in millimeters.

Measurement using a dimension table

If the nameplate is illegible or missing, the stroke can be calculated using a dimensional table for the specific actuator type (e.g., ISO 15552 or ISO 6432). Measure the distance between two points on the actuator body according to the diagram in the table and compare the result with the values in the table to determine the stroke.

Direct measurement of the piston rod

The stroke can also be measured directly on the cylinder rod. To do this:

1. Mark a point on the piston rod near the cylinder body with a marker when it is fully retracted.
2. Extend the piston rod fully and mark a point on the piston rod near the body again.
3. Measure the distance between the marked points—this is the actuator’s stroke.

When measuring directly, be careful not to damage the piston rod. It is best to use a caliper for the measurement. Smartphone measurement apps do not provide sufficient accuracy.

Knowing the stroke and the diameter of the piston and piston rod, you can calculate the actuator force using formulas or online calculators. The stroke is a key parameter for correctly selecting an actuator with the required operating parameters.