Core advantages of ball screw in transmission stiffness and positioning accuracy
1.Transmission Stiffness Advantage: Strong Deformation Resistance, Stable Load Response.
The transmission stiffness of ball screw mainly comes from their "ball-raceway" point-contact transmission structure and high precision manufacturing process. First, the runway between the stud and nut hardens, providing strong resistance to bending and compression deformation. Secondly, double-nut preload (such as shim preload or tooth difference preload) eliminates transmission backlash and even produces a slight interference fit, ensuring a tight fit between the sphere and runway under load and minimizing elastic deformation. The deformation of the ball screw under axial load is only 1/ 3 to 1/ 5 of that of the traditional sliding screw, compared with linear guide rail (which focuses on the stiffness of the drive, which depends on the drive ball screws) and synchronous belts (which is flexible and prone to tensile the deformation under load). This ensures linear transmission displacement under different loads and avoids transmission lag or position deviation due to insufficient stiffness.
2.Positioning Precision Advantages: Small Errors, High Repeatability
The positioning accuracy of ball screws depends on precision machining and structural design. One is the high precision of the lead. The screw The screw shaft line is machined by high precision rolling or grinding processes to ensure that the actual displacement of each guide wheel is least deviated from the theoretical value. Next, "rolling friction" replaces the "sliding friction" of traditional sliding screws with a friction coefficient of only 0.001-0.005 (compared to about 0.1-0.3 for sliding screws). This eliminates the "creeping" phenomenon associated with sliding friction (displacement wobble caused by low speed friction fluctuations) and ensures consistent displacement accuracy from low to high speed. Third, ball screws has excellent repeatability (usually ± 1m-± 5m). Combined with servo motor closed-loop control, multiple stable positioning can be achieved, far exceeding synchronous belts performance (repeatability ± 0.1mm).
ii. Typical case of preferred Ball Screws
1.High-Precision Positioning Requirement: there are strict requirements for displacement accuracy and stable, repeatable positioning.
Precision machine tools such as the Z-axis (axial feed) of CNC lathes and machining centers require a feed accuracy of 0.001mm to produce a high precision hole, groove or surface. The positioning accuracy of ball screws can meet the strict size tolerance requirements of machining.
Semiconductor equipment, such as the worktable movement mechanism of wafer lithography machines, requires nanoscale positioning. With high precision and low friction, the ball screws can achieve precision servo systems wafer alignment and avoid lithography error caused by positioning error.
Electronic component assembly equipment, such as the nozzle movement shaft of a chip placement machines, requires the chip to be placed precisely where PCBs are intended. Repeatable positioning accuracy of ±0.005mm is required. Ball screw ensures consistency of position and reduces defect rates.
2. High stiffness load: Large axial loads must be supported to avoid transmission deformation.
Heavy automation equipment, such as slide drive mechanism for mechanical presses, must be able to withstand axial pressures ranging from a few tons to several dozen tons. The transmission stiffness of ball screw ensures accurate slide displacement under high pressure and prevents stamping dimension deviation due to insufficient stiffness.
Industrial robots, such as the axial transmission joints in the forearms and wrists of six-axis robots, must support the weight and workload of end effectors such as fixtures and tools. The deformation resistance ability of the ball screw ensures the stability of the robot movement and prevents posture deviations when load changes.
Precision detection platform, such as the lifting mechanism, must carry testing instruments (can weigh hundreds of kilograms) to achieve smooth lifting. The stiffness of the ball screw can prevent tilt or displacement of the platform during the hoisting process, and ensure the accuracy of the test data.
3. High-speed, stable transmission scenarios: In high-speed operation, precision must be maintained to avoid frictional losses.
Packaging machinery: For example, the label feed shaft of a high-speed labeling machine can operate at speeds exceeding 1000 mm/s. The low friction characteristics of the ball screw reduces heat and wear during high-speed operation, ensures accurate label feed length and prevents label deviation due to transmission errors.
Laser Cutting Equipment: For example, the cutting head axis of a fiber laser cutter requires high-speed movement (up to 5000 mm/min) to improve cutting efficiency. The low friction and high positioning accuracy of the ball screw ensure that the laser focus is always along the cutting path, avoid path deviation and degrade cutting quality.
