# Study of Fault Identification of Clearance in Cam Mechanism
## 1 Introduction
By establishing the electro-hydro-dynamic (EHL) model, and providing the model with three basic parameters, the minimum oil film thickness, the maximum oil film pressure, and the minimum oil film thickness distribution, it is possible to analyze the kinematic parameters of the entire system, such as the velocity, acceleration, and displacement of the cam, under actual working conditions through numerical equations. The lubrication conditions of the mechanism are estimated to predict the actual life [9]. Considering non-Newtonian effects, thermal effects, and variable angular velocity angles of the rollers from the perspective of mixed lubrication, using load distribution and surface roughness analysis, a quasi-static analysis of the heavy-duty cam roller follower was carried out [9; 10]. The results show that, when the non-Newtonian effect and thermal effect are ignored when the contact surface is in a low-friction state, the main roller is in a pure rolling state, and the lubrication performance is also better. Furthermore, as the friction in the needle roller contact is upgraded, the contact force, non-Newtonian properties, and viscosity-pressure properties are also upgraded, and the SRR increases sharply. After that, the system changes from the full-film lubrication state to the mixed lubrication state [10]. The cam mechanism constitutes the heavy-duty part of the automaton of the Gatling gun, and it plays a significant role with respect to the shot speed, such as shot frequency, shot accuracy, and shot intensity. The traditional design of the main roller and cam focuses on reasonably optimizing the bolt's motion law and rationally arranging a cyclic diagram of the device's law [11]. A new optimization design method for the end face of the cam curve groove was recommended to reduce the lateral impact of the main roller [12]. The pure rolling criterion of the main roller for the fixed cam followed with rollers was deduced theoretically [13]. The power spectrum analysis, the phase-plane mapping, and the Lyapunov exponent parameters were involved in investigating the non-periodic motion of the roller follower [5]. The profile errors were revealed by changing the center distance between the cam and the pivots with the clearance [14]. A numerical analysis method for identifying the assembly defects of the cam curved groove mechanism was proposed following the Hertz contact theory [15]. The multi-body dynamic analysis and the optimization of the end groove curve among the rollers were performed [16; 17]. However, the face-to-face interaction between the fixed cam curve groove and the roller and bolt group with a high speed has been less studied, especially failure diagnosis and prediction on the roller-camdevice. The positive pressure and friction force change quickly and influence multiple aspects of the high-speed revolving main roller. Intensive further study is needed. This study introduces a fixed cam device with several rollers. Additionally, the requirements for the pure roller of a cylindrical cam in recoil with clearance are investigated. Figure 1 illustrates the automaton mechanism [7]. The structure of the fixed-cam curve slot and the bolt is shown in Figure 2. The specific structure of the bolt body is shown in Figure 3.  
body in synchronization, and it transfers along the guide groove on the revolving body. The bolt group is co-axially connected to every main roller. The rollers, the second part as shown in Figures 2 and 3, run along with the curve slot on the cam, which is the first part as shown in Figure 2 and the fourth part as shown in Figure 1. The distinguished merit of the device is that the designers can place several sets of guide grooves and bolt groups along the circumferential direction as needed to achieve high efficiency. The bolt group works under a high-speed and heavy-load transfer motion mechanism. It is a critical part of the cam design, and the cam curve slot determines its rule of motion.