# Experimental Study on In Situ Storage of Grease-Lubricated Ball Screws
## 4 Conclusions  
This in situ storage experiment on grease-lubricated ball screws aimed to analyze the performance changes in lubricating grease in the transmission mechanism of the actuating system after long-term storage and its influence on the transmission performance of ball screws. Through the above tests and relevant data analysis, the following conclusions are drawn:  
1. There are two main reasons for the failure of the lubricating grease studied in this article during storage. Firstly, the base oil in the lubricating grease contains ester oil, which is easily degraded by bacteria in the environment; on the other hand, there is a loss of the base oil during storage. Both reduce the effective lubricating components and lead to a decrease in lubrication performance. Based on the above analysis, it can be seen that after eight years of in situ storage, lubricating grease underwent continuous oxidation reactions in the temperature and humidity environment of our research institute, resulting in a decrease in various performance indicators. 2. The degradation of lubricating grease not only significantly reduces the transmission efficiency and friction torque of the ball screws, increasing the risk of wear and jamming of the ball screws, but also leads to a decrease in the heat dissipation capacity of the ball screw pair, which cannot maintain the normal working temperature of the screw, resulting in damage to the screws caused by overheating. Therefore, the degradation of lubricating grease has a significant impact on the operation and lifespan of ball screws. Figure 14: Temperature variation curve of ball screws at 4000 rpm. Figure 13: Temperature variation curve of ball screws at 2000 rpm. 3. The performance degradation results of lubricating grease after 8 years of in situ storage can provide an understanding of the failure mechanisms and failure modes of accelerated storage tests. A comparative test was conducted on the performance of the transmission mechanism in a degraded state (8-year in situ storage) and a normal state. The results showed that 8-year storage could cause changes in transmission efficiency and temperature rises but would not lead to a significant decrease in performance. Generally, unopened lubricating grease can be stored for about 5 years, while perfluoropolyether-based lubricating grease can be stored for 10 years or even longer. Lubricating grease should be sealed and stored. If conditions permit, it can be sealed with nitrogen gas and stored in a cool, dry, and ventilated environment. Lubricating grease packaging should be used as soon as possible after opening, and the use of small packaging is encouraged. Keeping the surface flat after using lubricating grease can reduce oil separation during storage and help extend the shelf life. 4. These performance changes in lubricating grease provide an experimental basis for the ball screw lubrication scheme. Synthetic lubricating grease with the slow degradation and volatilization rates of base oil, the slow consumption rate of antioxidants, and the strong antioxidant ability of thickeners needs further research and trial production. Through methods such as comparison, investigation, and composition compounding, key technologies for improving the storage stability of main components, such as base oils and thickeners, should be broken through, thereby improving the stability of lubricating grease and extending its storage life. 5. The results of the storage simulation test have significance in guiding the accelerated storage test design of lubricating grease. Based on the test results of this article, the rheological property detection results should be considered as the data basis for the accelerated degradation model, the oxidation induction period in the later stage of degradation as the modeling basis, and other indicators to explain the degradation mechanism from a microscopic perspective. Conceptualization, Z.H. ; Methodology, P.C. ; Software, H.Z. ; Validation, L.H. ; Formal analysis, Y.H. ([PERSON]); Investigation, P.C.