The SCARA robot is a great example of the simple ball screw used for Z-axis motion, but this new configuration from NSK is a simple design with a few key benefits over the simple ball screw. In motion control rotary motion is common and so is linear motion, but what if you need to combine them in the same assembly? In this video, we spoke to Jeff Molter, linear segment manager at NSK Precision America. NSK makes bearings, ballscrews, motors, and other motion control components, such as linear actuators.
According to Molter, not many companies in the world, beside NSK, make this product. It’s a combination of a ball screw and ball spline, with a hollow shaft. The system provides compact Z-theta motion very accurately, with no backlash. The system features angular contact bearings on each nut, allowing the system to carry load axially.
Traditionally, linear motion and rotary motion were done by different types of drives. This system uses a pair of identical stepper motors or servomotors, controlled by an outside controller. If the motors are operated together, you get theta motion, or rotation. Operate them differentially, and you’ll see linear, Z-axis motion.
There are a few benefits of the hollow shaft. For one, it reduces weight. Secondly, it provides a channel to run vacuum hoses, wiring, or even coolant. In applications requiring high loads and speeds, such as pick and place or assembly robotics, heat dissipation can be a big issue. Through coolant may allow this system to perform sustained operation at higher loads or speeds.
Typical applications of this product include electronics and semiconductors, automotive, pharmaceutical, and automotive as well as general manufacturing.
For more on motion control, check out Video: Let a Black Box Do the Motion Control Dirty Work.