Ball Screws

A ball screw is a small mechanical linear actuator that converts rotational motion into precise linear movement. Ball screw assemblies consist of a threaded shaft and recirculating ball bearings, working together to deliver smooth, accurate, and highly efficient linear positioning. They are capable of handling high thrust loads while generating minimal internal friction, making them a reliable and long-lasting component in a wide range of motion control applications. Buy ball screws and linear ball screw assemblies from RS Australia for reliable precision motion control.

How Ball Screws Work

Inside the nut, ball bearings roll between the screw threads and the nut raceway rather than sliding, which reduces friction to near-zero. As the screw turns, the balls travel through the nut and are redirected back to the start via a return tube or end cap. This recirculation principle is what gives ball screws their high mechanical efficiency and low heat generation, allowing them to sustain precise, repeatable linear movement over extended periods of operation.

Ball Screw vs Lead Screw

A ball screw actuator uses recirculating ball bearings to achieve high efficiency, high speed, and minimal friction, making it the preferred choice for precision and high-duty-cycle applications. A lead screw actuator, by contrast, uses sliding contact between the nut and thread, which introduces more friction but provides a natural self-locking property and a lower cost of manufacture. Lead screw actuators are well-suited to lighter-duty or cost-sensitive applications where back-driving is undesirable.

Applications of Ball Screws

Ball screw units and assemblies are commonly used within a range of precision motion control and automation systems, such as:

• CNC machinery: Linear ball screw assemblies are used to drive X, Y, and Z axes in CNC machining centres, delivering the positional accuracy and repeatability required for precise cutting, milling, and drilling operations.
• Semiconductor wafer handling: The near-zero friction and high positional accuracy of linear screw drives make ball screws well suited to the delicate, highly controlled movements required in semiconductor manufacturing and wafer-handling equipment.
• Precision medical imaging tables: Ball screws are used in medical imaging equipment such as MRI and CT scanner tables, where smooth, accurate, and quiet linear movement is essential for patient positioning and diagnostic accuracy.
• Automotive power steering systems: Ball screw actuators are used in automotive power steering assemblies to convert rotational input into controlled linear force, providing responsive and efficient steering performance.

Ball Screws Types

There are various types of ball screw nuts available. They can be categorised by:

Nut Styles

Ball screw nuts are available in several configurations to suit different mounting and space requirements. Flanged nuts feature an integrated flange that simplifies mounting and is well-suited to applications where the nut needs to be bolted directly to a carriage or plate. Cylindrical nuts have a compact profile suited to installations where radial space is limited. Square nuts offer a flat mounting face and are commonly used where a rigid, stable fixing arrangement is required.

Motorised Units

A ball screw actuator with motor or a ball screw linear actuator with motor combines the screw assembly and drive into a single integrated unit, providing a drop-in motion solution that simplifies installation and reduces design complexity. These units are available with DC motordrives for applications requiring variable speed control and compact power delivery, making them a practical choice for robotics, automation, and portable or battery-powered motion systems.

How to Install Ball Screws

Correct installation of a ball screw assembly is critical to achieving accurate performance and a long service life. Follow these steps in sequence:

• Inspect all components: Check the screw shaft, nut, and any associated hardware for damage or contamination before beginning installation, as debris or surface damage can affect performance immediately.
• Align the mounting surfaces: Ensure the bearing supports and nut housing are precisely aligned before fixing any components in place, as misalignment places uneven loads on the ball bearings and reduces service life.
• Mount the end supports: Fix the bearing end supports to the machine frame, ensuring they are square and level with the axis of travel before tightening to the specified torque.
• Install the screw shaft: Insert the screw shaft through the end supports and secure it in place, checking that it rotates freely without binding or excessive runout.
• Fit the ball screw nut: Slide or thread the nut onto the shaft carefully, ensuring the ball bearings are not displaced during installation. Never remove the nut from the shaft without a temporary support tube in place.
• Connect the drive: Couple the motor or drive mechanism to the shaft using the appropriate coupling, ensuring concentricity and correct torque transmission without imposing axial loads on the bearings.
• Test and adjust: Run the assembly through its full range of travel at low speed, checking for smooth movement, correct preload, and accurate positioning before operating at full load or speed.

How to Choose Ball Screws

Selecting the right ball screw depends on the load, speed, precision, and environmental requirements of your application. Consider these five key factors:

• Lead and pitch: The lead determines how far the nut travels per revolution of the screw. A higher lead delivers faster linear speed with less torque, while a lower lead provides greater force and finer positional resolution. Match the lead to the speed and accuracy requirements of your system.
• Load capacity: Ensure the ball screw is rated to handle the dynamic and static loads of your application, including any shock or peak loads. Undersized screws wear rapidly and can fail prematurely under sustained load.
• Screw actuator length and diameter: Longer screws are prone to deflection and critical speed limitations, so diameter must be matched to the length and rotational speed. Selecting the correct diameter ensures the assembly remains stable across its full stroke.
• Preload and accuracy grade: Higher preload reduces backlash and improves positional accuracy but increases friction and heat generation. Choose an accuracy grade and preload level that reflects the precision demands of your application without unnecessarily overspecifying.
• Mounting and nut style: Consider whether a flanged, cylindrical, or square nut suits your mounting arrangement, and ensure the end support configuration is compatible with your machine design and available space.

Buy Ball Screws Online from RS Australia

RS Australia is your reliable source for high-quality ball screws and screw actuator solutions. We stock an extensive range from industry leaders like Ewellix Makers in Motion, NSK, and Bosch Rexroth. Our selection spans various configurations at competitive prices, ensuring you find the perfect linear actuator screw for your application.

We also carry other essential mechanical power transmission components, such as mitre gearsand sprockets, for other motion control and automation requirements. Buy ball screws and other accessories online with next working day delivery. For more details on delivery services and fees, please refer to ourDelivery page.