The ball screw spline can realize both straight line motion and rotation motion. The core principle is to combine the functions of the ball screw and the rotating ball spline into one axis. The combination of three types of motion is realized by the independent actuation of ball nut and spline nut. Here's a breakdown:
I. Structural Foundation: Dual-nut Design Achieves Motion Decoupling
The shaft body of the ball screw spline also possesses thread and spline grooves corresponding to the ball nut and spline nut respectively. Each nut is equipped with a radial bearing (such as angular contact ball bearings) to form separate movement units:
Ball nuts: responsible for converting rotational motion into linear motion, driving shaft body along the axis;
Spline nut: through the ball and spline grooves, the shaft body rotational movement of the transfer, allowing axial sliding.
II. Motion realization method: Switch between three modes as needed
By controlling the drive state of the two nuts, the following combination of movements can be generated:
Pure linear movement
Drive the ball screw to turn and keep the spline screw stationary. Because of the thread, the shaft body moves in an axial direction, and the fixed structure of the spline screw prevents it from rotating, ensuring pure linearity of movement.
Application scenarios: CNC machine tool table feed, 3D printer nozzle movement.
Pure spin
Drive the spline screw to rotate and keep the ball screw steady. The shaft rotates due to the combination of the spline groove and the ball, while the threaded structure of the spline screw restricts its rotation, ensuring pure rotation.
Application scenarios: Positioning of rotary table, rotation of robotic arm joints.
Spiral motion (linear + rotational synchronization)
At the same time, two screws are driven to make the shaft body move in an axial direction when rotating, forming a spiral trajectory.
Application scenarios: Threadwork, complex surface engraving.
Compounding motion (independent control)
The servo system is used to control the speed and direction of the two screws respectively to realize the combination of linear and rotational motion in any proportion. For example:
The shaft body rotates during slow feed (such as drill bit tapping);
shaft body moves in a fast straight line while fine-tuning the rotation angle (such as precision assembly).
III. Technical advantages: high accuracy, high rigidity and integration.
Motion synchronization
The precise alignment between the sphere and the raceway ensures the synchronization of rotation and linear motion. Repeated repeat positioning accuracy is ± 0.001mm, suitable for semiconductor manufacturing, medical devices and other high precision fields.
Load capacity
Axial load: borne by ball screw part, larger diameter, smaller pitch, stronger bearing capacity;
Radial load and torque: Scattered to the sphere through the keyway structure, can withstand large radial forces and torque.
Transmission efficiency
Rolling friction replaces sliding friction, with high efficiency of 85%-90%, low energy loss, suitable for high-speed movement (e.g. separation of robotic arm of automated production line).
