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Time-varying reliability prediction modeling of positioning accuracy influenced by frictional heat of ball-screw systems for CNC machine tools |
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| Affiliation: | 1. Equipment Reliability Institute, Shenyang University of Chemical Technology, Shenyang, 110142, China;2. School of Mechanical & Automation, Northeastern University, Shenyang, 110819, China;1. Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116024, China;2. State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, China;3. State Key Lab of Digital Manufacturing Equipment & Technology, Huazhong University of Science and Technology, Wuhan 430074, China;4. The Key Laboratory of Vibration and Control of Aero-propulsion System, Northeastern University, Shenyang 110819, China;1. Department of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China;2. Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, T6G 2G8, Canada |
| Abstract: | Thermally induced elongation of a screw is the primary cause of deterioration in the positioning accuracy of half-closed-loop screw systems in machine tools. The failure mode of ball-screw feed-drive systems in relation to the positioning accuracy is defined as the response error of the carriage exceeding the axial tolerance. It is still challenging to accurately predict the thermal errors using conventional methods because the randomness of the influencing factors is not considered. This paper presents an improved random thermal network model subjected to dynamic thermal excitation for calculating real-time transient temperatures of ball-screw systems. Furthermore, a time-varying reliability model is proposed for estimating the gradual reliability of the thermally induced positioning accuracy of ball-screw systems with random thermal boundary parameters using the random thermal network. A ball-screw system of a computerized numerical controlled lathe is used as an example to show the practical application of the proposed model. Repeated experiments demonstrate the accuracy retaining ability and robustness of this method. This work provides the theoretical and practical method for real-time monitoring of the positioning accuracy reliability index for ball-screw systems and it has high accuracy considering the random parameters. |
| Keywords: | Time-varying reliability Positioning accuracy Ball-screw Random thermal network Machine tool |
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