Screw drive trains, a popular linear actuation technology, are designed to act as force multiplication devices, taking rotary torque input from a motor and converting it to linear thrust. A wide range of options are available, each with its own advantages and disadvantages. When choosing a linear actuator solution for your next motion control application, understand the three major screw drive technologies available.
The lead screw
Lead screws are a mechanical drive train choice for applications requiring low precision and low duty cycle for a low cost. Lead screws are composed of a metal screw that interfaces with a nut made of a softer material (often plastic or bronze). Primary manufacturing techniques are rolling or grinding.
Lead screws are not always an ideal technology for industrial applications given their wear characteristics, but they work well for applications requiring low-duty cycle adjustments to positions or a self-locking drivetrain.
The ball screw
A majority of linear motion control applications employ ball screws to convert motor torque to linear thrust due to their commercial availability, ease of manufacture, high efficiency and load-life characteristics.
A ball screw is composed of a metal screw and nut, which uses metal ball bearings as the mating interface between the threads. They may be manufactured by rolling, grinding or whirling. Ball screws are an ideal solution for industrial applications with high duty cycles that also require high thrust.
The roller screw
A roller screw is composed of a screw and an interfacing nut, with small rollers that rotate to provide contact between the nut and the screw. Manufacturing techniques to produce these screws are quite costly, due to the tight machining tolerances required, making their manufacturing lead time long when compared to ball or lead screws.
With line contact between the rollers, nut and screw, this technology is superior to ball screws in terms of shock load and overall stiffness. Roller screws are well-suited to motion control applications requiring a large load and extremely long life.
Most design engineers can quickly decide whether or not lead screws will work for their application so our next post will focus on using a performance calculator to make a choice between ball screws and roller screws for your application.
In the meantime, you can download our whitepaper on choosing the right linear drive train.
Article contributed by Electromechanical and Drives Division, Parker Hannifin Corporation.
Much of this content was first published in April 2016 as “As the Screw Turns” on Design World’s website.