The Impact of Preload on Ball Screw Performance in CNC Machines

Preload is the controlled axial force applied to a ball screw during CNC machine tool operation. It eliminates axial clearances and minimizes backlash, thereby enhancing the screw's stiffness, positioning precision, and servo responsiveness. So, how does adjusting preload influence ball screws in CNC systems?

Reducing Axial Gaps: Proper preload can diminish or eliminate axial gaps in ball screws, thereby boosting transmission precision and rigidity. This is crucial for maintaining high accuracy during complex machining tasks like 5-axis simultaneous operations or turn-mill processes on machining centers.

Enhancing Axial Stiffness: Preload amplifies axial stiffness, enabling ball screws to better withstand deformation from cutting forces (e.g., from high-speed spindles) and reaction forces from linear guideways. This diminishes errors in servo motor tracking.

Mitigating Wear: Appropriate preload optimizes the contact geometry between balls and raceways, reducing Hertzian stress per unit area. This lessens wear and extends the lifespan of ball screws within FANUC or Siemens closed-loop systems.

Thermal Considerations: Elevated preload levels can heighten friction, increasing nut temperature and inducing thermal elongation of the screw. Excessive preload escalates motor torque demands, reduces machining efficiency, and may truncate the lifespan of ball screws due to overheating.

Lubrication and Preload Compatibility: Preload adjustments should harmonize with the CNC machine's automatic lubrication system (e.g., intermittent or micro-oil-mist systems). This ensures the lubricant film remains intact under high pressure, preventing flaking or corrosion.

Load Matching Strategies: Preload ought to correspond to the machining center's cutting load profile. Proper preload compensates for deflection caused by cutting forces and preserves precision. However, under high dynamic loads (e.g., turn-mill applications), excessive preload accelerates fatigue and flaking in ball screws.

To sum up, optimal preload enhances rigidity and machining precision, whereas excessive preload diminishes ball screw longevity. Hence, preload settings should be meticulously determined based on machine type (e.g., vertical/horizontal machining center, gantry, turn-mill) and actual cutting parameters. For selection advice or technical inquiries, please contact JSWAY CNC COMPANY!