Inverted roller screws engineered for high performance
22 May 2017
SKF’s range of inverted roller screws ensure powerful electromechanical actuation in applications that require compactness, low torque and high load. They were developed for compact electromechanical cylinders – in which the motor is wrapped around the screw – and typically replace hydraulic or pneumatic actuation systems.
Common applications include factory automation (such as a car assembly line), welding guns, portable high power tools, oil and gas subsea equipment, and aerospace actuators.
“The big advantage of inverted roller screws is that all the rollers drive all the time – which means higher acceleration,” says Phil Nicholas, business development manager – linear and actuation technology at SKF.
Roller screws are premium products that require precision manufacturing – which explains their higher price. SKF offers three main types, which includes inverted roller screws. These have threaded rollers – which are synchronised to the screw shaft through toothed rings, and translate the screw shaft within the nut or indeed vice versa. Loads acting on the translating push tube are transmitted through the planetary rollers to the rotating shaft or nut. Toothed rings and guides ensure the rolling motion of the rollers and even their circumferential positioning – and avoid the parasitic friction between rollers.
SKF’s inverted roller screws come in two variants: the main ISR series has axial play, while the IBR series comes without backlash. The backlash-free variant helps to enhance equipment stiffness and accuracy.
Both variants are available in six different sizes (ranging from nominal 18 to 48mm diameter), and have load carrying capacities from 35.6 to 259kN. Leads range from 2.4 to 6mm. Even the small leads have robust threads, allowing high load carrying capacity and axial stiffness.
Inverted roller screws can be supplied with either left- or right-hand threads.