Types of Electric Linear Actuators Explained

Electric linear actuators turn rotary motor movement into straight-line motion, and the way they do it changes everything: load capacity, speed, accuracy, duty cycle and how long the unit lasts. Choose the wrong type and you'll fight short service life, missed positions or a motor that runs too hot. Choose the right one and the machine just works.

This guide walks through the main types of electric linear actuators, with the trade-offs that matter and the applications each one suits. If you want the wider picture first, start with our overview of electric linear actuators and then come back here to compare the mechanisms in detail.

How electric linear actuators work

Every electric linear actuator uses the same basic idea. A motor drives a mechanism that converts rotation into push and pull along a single axis. What sits between the motor and the moving rod (or carriage) is what separates one type from another.

The three big variables to weigh up are:

• Load — how much force the actuator has to push or hold.
• Speed — how fast you need the rod to travel.
• Life — how many cycles the unit must survive before wear becomes a problem.

Get those three right for your application and the rest follows.

Acme (lead) screw actuators

Acme screw actuators use a threaded screw and a nut, usually in bronze or a polymer. As the screw turns, the nut (and the load attached to it) travels along it.

They're the most cost-effective type and often self-locking, so they hold position when the power is off without needing a brake. That makes them a sensible choice for static holding and lighter-duty positioning.

The trade-off is efficiency. Sliding friction between the nut and screw generates heat and wear, so acme actuators suit lower duty cycles and moderate speeds rather than continuous high-throughput work.

Typical applications:

• Light to medium positioning tasks
• Infrequent or intermittent duty cycles
• Applications that benefit from self-locking hold

Ball screw actuators

Ball screw actuators replace sliding friction with rolling friction. Recirculating ball bearings run between the screw and the nut, which lifts efficiency well above an acme screw.

That higher efficiency means more force from the same motor, faster speeds and far longer service life under heavier, more frequent duty. They also offer good repeatability, which matters when position accuracy counts.

The trade-offs are cost and backdriving. Because they're efficient, most ball screws aren't self-locking, so a vertical load may need a brake to hold position. They also need proper lubrication to reach their rated life.

Typical applications:

• Higher-duty industrial automation
• Faster cycle times and heavier loads
• Tasks needing good positioning repeatability

Roller screw actuators

Roller screw actuators use threaded rollers arranged around the screw instead of recirculating balls. The result is more contact points carrying the load, which means higher force density, longer life under heavy loads and the ability to run at high speeds for long duty cycles.

They're the type to reach for when you're pushing serious force, running near-continuous duty, or need maximum life in a compact envelope. In those demanding cases a roller screw often outlasts a ball screw by a wide margin.

The main consideration is cost. Roller screws are a premium component, so they earn their place on the hardest-working, highest-force applications rather than light-duty ones.

Typical applications:

• High-force pressing, forming and clamping
• Continuous or near-continuous duty
• Heavy-load work where long life justifies the investment

Belt-driven actuators

Belt-driven actuators use a motor to drive a toothed belt that moves a carriage along a guided rail. Because there's no screw to turn over long distances, they handle long strokes and high travel speeds very well.

They're the natural fit for moving lighter loads quickly across a distance, such as gantries, pick-and-place and transfer work. Speed and stroke length are their strengths.

The trade-offs are force and stiffness. Belts carry less thrust than screws and have some give under load, so they're less suited to high-force pushing or holding heavy static loads.

Typical applications:

• Long-stroke travel
• High-speed transfer and handling
• Lighter loads moved quickly

Choosing the right type for your application

As a rough guide:

• Acme screw — lowest cost, self-locking, lighter and intermittent duty.
• Ball screw — efficient all-rounder for faster, heavier, repeatable work.
• Roller screw — highest force and longest life for demanding, continuous duty.
• Belt-driven — long strokes and high speeds with lighter loads.

In practice the choice comes down to your exact load, speed, stroke and duty cycle, plus the mounting, feedback and controls around the actuator. That's where a short conversation saves a lot of trial and error.

Speak to us about your application

We're the UK distributor for Tolomatic, and we've been supplying power transmission components since 1954. Tell us the force, speed, stroke and duty cycle you're working to, and our team will point you at the right actuator for the job, with high stock availability behind it.

Speak to us today.