As the design precision and efficiency requirements for automation equipment continue to rise, the selection of linear motion systems is no longer a simple matter of stacking specifications. A complete linear motion system encompasses dozens of components, including lead screws, guide rails, sliders, bearings, couplings, support units, and even drive motors. Ultimately, the concept of “fitness for purpose” is what determines the long-term stable operation of the equipment.
he Core of Converting Rotary Motion to Linear Motion – Ball Screws
The ball screw is the most critical transmission component in a linear module, consisting of three main parts: the screw shaft, the nut, and the ball bearings. Its core function is to convert the rotary motion of the motor into linear motion of the worktable.
Technical Characteristics: Because the balls roll between the screw shaft and the nut, frictional resistance is extremely low (approximately only one-third that of sliding lead screws), enabling high-precision linear motion even under heavy loads. However, ball screws do not possess the self-locking capability of trapezoidal lead screws. Therefore, when installed vertically, they must be paired with a braking motor or a balancing mechanism.
Linear Guides: The Foundation for High-Rigidity Guidance and Load Support
Linear guides (also known as linear motion rails or profiled rail guides) are used in linear reciprocating motion applications. They have a much higher rated load capacity than linear bearings and can simultaneously withstand certain torque loads, making them the “track” for achieving high-precision linear motion under heavy loads.
Structural Advantages: The contact between the guide rail and the slider is achieved through rolling elements—either balls or rollers—resulting in a low coefficient of friction and high rigidity. Compared to the “shaft + linear bearing” configuration, linear guides offer significant advantages in torque resistance and service life.
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The Slider – The Moving Component That Cooperates with the Guide Rail
The slider is the component that moves in cooperation with the guide rail, directly carrying the worktable or load and reciprocating along the rail. In screw-driven modules, the slider mounting plate also houses the ball screw nut mounting bracket. The screw nut is connected to the slider mounting plate, and when the screw rotates, the nut drives the slider and worktable to move along the guide rail.
Currently, the most common types are square type and flange type. Models range from HG15 to HG65, allowing selection of the appropriate slider type based on different load capacities.
Speaking of sliders, I must mention bearings. Unlike slider bearings, these are primarily used in the linear reciprocating motion of balls, bearing both axial and radial loads to ensure smooth screw rotation.
Ball Screw Support Units – How to Secure the Ball Screw
In the description above, we mentioned ball screws. So how is the ball screw fixed? This brings us to another component—the ball screw support unit.
Support units are structural components that connect both ends of the screw shaft to the mounting base. They consist of a fixed side and a support side, essentially serving as the “bearing housing” for the screw.
Fixed-side support unit: Contains preloaded angular contact ball bearings, connected to the motor end, responsible for axial positioning and thrust transmission. High-rigidity, high-precision bearings are selected to ensure stable rotational performance.
Support-side support unit: Contains deep groove ball bearings, supporting the rear end of the screw shaft. This allows axial floatation when the screw expands due to heat, preventing stress caused by thermal deformation.
Currently popular models include BK/BF, EK/EF, and FK/FF. Selection is based on the installation method to choose the appropriate mounting type.
Couplings – Compensating for Installation Deviations
In high-speed linear reciprocating motion, couplings serve as components that transmit torque while compensating for radial, angular, and axial installation deviations.
Common types:
Diaphragm coupling: Zero backlash, high torque transmission, suitable for high-precision applications driven by servo motors.
Slotted (bellows) coupling: Zero backlash, suitable for small to medium torque stepper motors.
Jaw (spider) coupling: Provides cushioning and vibration damping performance.
Oldham coupling: Simple structure, suitable for applications with lower precision requirements, such as cylinders or wire-wound motors.
Selection requires comprehensive consideration of torque requirements, deviation compensation capacity, rotational speed, and motor type.
Summary
To summarize, the six categories of components each play their distinct role in a linear motion system: the screw provides driving force; the guide rail and slider achieve guidance and load support; bearings and support units ensure rotational precision; and the coupling completes power coupling. When selecting components, comprehensive consideration must be given to four key dimensions—load, stroke, speed, and precision—so that the performance of each component matches the overall system requirements, thereby achieving long-term stable operation of the equipment.
