Research on on-line monitoring technology for steel ball's forming process based on load signal analysis method

• Published in: Mechanical systems and signal processing 2013-04, Vol.36 (2), p.317-331
• Main Authors: Li, Ying-jun, Ai, Chang-sheng, Men, Xiu-hua, Zhang, Cheng-liang, Zhang, Qi
• Format: Article
• Language: English
• Subjects: Cold heading; Computer simulation; Finite element method; Forming; Forming quality; Mathematical models; Monitoring; Polyvinylidene fluorides; PVDF force sensor; Sensors; Signal analysis; Steel ball; Structural steels; Vibration and wave
• ISSN: 0888-3270; 1096-1216
• DOI: 10.1016/j.ymssp.2012.10.013

This paper presents a novel on-line monitoring technology to obtain forming quality in steel ball's forming process based on load signal analysis method, in order to reveal the bottom die's load characteristic in initial cold heading forging process of steel balls. A mechanical model of the cold header producing process is established and analyzed by using finite element method. The maximum cold heading force is calculated. The results prove that the monitoring on the cold heading process with upsetting force is reasonable and feasible. The forming defects are inflected on the three feature points of the bottom die signals, which are the initial point, infection point, and peak point. A novel PVDF piezoelectric force sensor which is simple on construction and convenient on installation is designed. The sensitivity of the PVDF force sensor is calculated. The characteristics of PVDF force sensor are analyzed by FEM. The PVDF piezoelectric force sensor is fabricated to acquire the actual load signals in the cold heading process, and calibrated by a special device. The measuring system of on-line monitoring is built. The characteristics of the actual signals recognized by learning and identification algorithm are in consistence with simulation results. Identification of actual signals shows that the timing difference values of all feature points for qualified products are not exceed ±6ms, and amplitude difference values are less than ±3%. The calibration and application experiments show that PVDF force sensor has good static and dynamic performances, and is competent at dynamic measuring on upsetting force. It greatly improves automatic level and machining precision. Equipment capacity factor with damages identification method depends on grade of steel has been improved to 90%. ► A novel on-line monitoring technology based on load signal analysis method is presented. ► The die's load characteristic in cold heading forming process of steel balls is revealed. ► Method by using three signal characteristic points is advanced. ► A novel PVDF piezoelectric force sensor is designed and fabricated. ► Presented PVDF force sensor is competent at dynamic measuring on upsetting force.