How To Maintain The Precision of A Ball Screw？

Ball screws, as core components of precision transmission, directly affect the machining quality of equipment. This blog reveals six methods for maintaining the precision of ball screws, from daily maintenance to professional upkeep.

1. Lubrication management determines lifespan.

High-quality lubricating grease is the first line of defense for precision protection. Select specialized greases rated ISO VG32~68, using an intermittent oiling method to replenish new grease every 200 hours of operation. Be cautious not to mix greases from different brands to avoid chemical reactions that could lead to lubrication failure.

Over-lubrication is more dangerous than lack of oil. Excess grease can attract metal particles, forming an abrasive paste that accelerates raceway wear. It is recommended to use a metering oiler to maintain a uniform oil film of 0.05mm on the lead screw surface. In high-temperature environments, synthetic fluorinated grease should be chosen, with a temperature resistance of over 150°C.

2. Cleaning protection isolation from contamination

Micron-level dust can influence precision. Configured with multi-layer labyrinth shields, the inner layer uses 0.1mm thick fluororubber scrapers. After daily shutdown, the tracks are blown clean with 0.3MPa compressed air, and non-woven fabric soaked in precision instrument cleaner is used to wipe the ball recirculator.

Chemical corrosion should not be ignored. In areas where cutting fluid splashes, it is recommended to install stainless steel corrugated tube protective covers. In acidic or alkaline environments, check the passivation film on the ball surface monthly, use pH test strips to monitor the internal environment of the protective cover, and keep the pH value between 6.5 and 7.5.

3. Preload adjustment maintains rigidity.

Preload loss is the main cause of accuracy degradation. Using dynamic torque method for detection, when the no-load driving torque exceeds the initial value by 15%, re-adjustment is required. Use a dedicated preload adjustment tool to tighten the lock nut in three increments, rotating the screw by 90 degrees each time to eliminate assembly stress.

Temperature compensation cannot be ignored. After preheating the machine tool for 30 minutes, use a laser interferometer to detect positioning accuracy. For every 10°C change in temperature, compensate by 2-3 μm/m. High-precision equipment should be equipped with temperature sensors to correct thermal expansion in real time.

4. Professional maintenance extends the service life cycle

Deep maintenance is crucial. After disassembly, use a coordinate measuring machine to inspect the raceway ellipticity, which must be ≤3μm. The grouping error of the ball diameters needs to be controlled within 0.5μm, and when replacing, the entire set must be updated simultaneously; mixing new and old ones is strictly prohibited.

Vibration spectrum analysis predicts faults. Regularly collect operating vibration signals, focusing on abnormal peaks in the 500-800 Hz frequency band. When the vibration acceleration value exceeds 8 m/s⊃2;, it indicates abnormal wear of the circulator or reverser, requiring immediate shutdown for inspection.

5. Testing and calibration

Dynamic stiffness testing reveals hidden issues. Using a dynamic force hammer to apply excitation forces ranging from 10 to 1000 N, the system's resonance frequency is detected. When the axial stiffness decreases by 20% or the damping ratio falls below 0.1, it indicates structural defects in the support bearings or nut seats.

6. Abnormal response

Abnormal noise diagnosis methods. A metallic scraping sound indicates insufficient lubrication, a periodic clicking sound points to damage in the circulator, a muffled humming suggests pre-load failure, and a sharp screeching is a signal of ball bearing breakage. Each type of abnormal noise corresponds to a specific treatment plan, and it is necessary to establish a sound spectrum database to assist in judgment.

Precision compensation. When mechanical repair does not meet standards, activate pitch compensation function. Use equal spacing compensation method, setting one compensation point every 50mm, corrected through CNC system parameters. The compensation amount should retain a 20% margin to prevent over-compensation from causing oscillation.

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