MT Series Belt-Driven Linear Actuators: Which One Should You Choose?

Linear actuator selection is one of the most important decisions in machine design. Belt-driven actuators use an electric motor to turn a toothed pulley. The pulley engages with a flexible, steel-reinforced belt with evenly spaced teeth, called a timing belt. The belt is attached to a moving platform, called the carriage, which carries the machine’s load along the actuator. Because the belt teeth fit into matching grooves on the pulley, the belt moves without slipping, allowing the carriage to travel quickly, smoothly, and repeatedly to the correct position.

Belt-driven actuators can also achieve longer stroke lengths because they do not rely on a long rotating screw. Stroke is the usable distance the carriage can travel from one end of the actuator to the other. In a screw-driven actuator, the screw must become longer as the required stroke increases. A long screw can bend slightly, vibrate, or whip when it spins at high speed, which limits both travel length and operating speed. A timing belt does not have this same problem because it is flexible and moves around pulleys instead of rotating like a long metal shaft. To increase the stroke, the manufacturer can use a longer actuator profile and a longer timing belt. The belt itself is longer than the stroke because it forms a complete loop around the drive pulley and idler pulley, while the carriage travels along only the straight working section of that loop.

MTB, MTE, and MTS actuators from PBC Linear all use this belt-and-pulley system, but they support and guide the carriage in different ways. The MTB uses two internal linear guides, which support the carriage from inside the actuator body and help keep the system compact and protected. The MTE uses one external linear guide, which supports the carriage from outside the actuator body and can improve its ability to handle side loads and twisting forces. The MTS uses two external linear guides, creating a wider support structure for the carriage and making the actuator better suited to heavier loads, larger mounting plates, and stronger moment loads.

The linear-guide arrangement matters because the timing belt creates the motion, but the linear guides support the carriage and control how it moves. The belt pulls the carriage forward and backward, but it cannot by itself prevent the carriage from tilting, twisting, or shifting under an off-centre load. Internal linear guides keep the support components enclosed and help reduce the actuator’s overall size. External linear guides can be positioned farther apart, giving the carriage a wider base of support. Two external linear guides provide the greatest resistance to pitching, rolling, and yawing forces, which improves rigidity and stability under demanding loads.

This feature blog post compares the specifications, design differences, motor options, carriage support systems, and best applications for MTB, MTE, and MTS actuators so you can understand how each design works and choose the right belt-driven actuator for the machine.