oyostepper

Astepper motor linear actuator converts the rotary motion of a servo or best linear stepper motor into linear motion. There are a range of actuator types, including lead screw actuators, ball screw actuators, planetary roller screw actuators, belt drives, and so on. Designs can be rodless, rod style, or even integrate the motor into the actuator.

So how do you choose?

Like most things in engineering, the choice of actuator comes down to the application. Before you consider the various technologies, be clear about your requirements, from the load, speed, and accuracy, to the lifetime and duty cycle required. Will the actuator be operating in a washdown, vacuum or other harsh environment?

How much space do you have? And, of course, what is your budget?

Armed with this information, you can make an informed choice and find the technology that will provide optimal performance for the investment. “As a design engineer you have four or five technologies looking back at you,” says Scott Frederick, applications engineer at Kerk Motion Products Inc. (Hollis, New Hampshire). “When you go all the way through a specific application, by the time you get to the end of it, you might only have one or two options left.”

Threaded nut, or linear motor lead screw, designs provide good performance for cost. (Courtesy of Kerk Motion Products Inc.)Screw Technology.So what are some of those options? Linear actuators can be broadly divided into screw type and belt type. In the first category, a turning screw generates the motion. Screw-type actuators can be further divided into lead screws, ball screws, and planetary roller screw types.

In the most basic design, commonly referred to as a lead screw actuator, a threaded nut moves with respect to the screw, generating motion in whichever element is not fixed. The term ‘lead screw’ is actually a misnomer, because all of the screw designs are based on lead screws, but for purposes of this article and to minimize confusion, we will use it. Lead screw technology is simple, economical, and widely used. The actuators tend to be quiet and suffer less from back driving than other alternatives.

Because the surfaces of the nut are sliding against the threads of the screw, however, friction, and thus wear, become issues. This reduces lifetime, efficiency, speed, and also performance, because wear on the solid nut may affect accuracy/repeatability. Frictional resistance may even necessitate higher input torques.

Design of Controlling System for Linear Stepper Motor Based on DSP2407