## 2 Mechanical Performance Experiment of New TBM Integrated Cutter System  
### Structure Design of New TBM Cutter System  
Traditional TBM cutter system mainly has three types: double wedge blocks cutter system, upper and lower wedge blocks cutter system, and rear-installed cutter system. The main structure defect of the above traditional cutter system is a complex structure and has numerous parts. The disc cutter disassembly steps are complicated, which will significantly reduce the disc cutter replacement efficiency.  
This paper obtains inspiration from the automatic firearm's mechanism and optimizes the traditional cutter system's structure. We obtain a sliding block swing mechanism and evolve it into a fastening mechanism. Supplementing the cutter holder, high-strength bolts, disc cutter, wedge, shift fork, cutter side panels, and other components can get the complete design scheme of the wedge swing type new cutter system, as shown in Figure 1.  
The cutter system can be divided into the fastening module and supporting module according to the function. The main function of the fastening module is to fix the disc cutter tightly in the cutter system to ensure that it can reliably carry out a rock-breaking operation, and the main components are high-strength bolts, long shaft, shift fork, wedge, cushion block, fastening flange, etc. The main function of the support module is to limit the relative position between the cutter system's two sides and provide a grip  
Figure 1: Schematic diagram of wedge swing type cutter system.  
the cutter-changing robot when replacing the disc cutter. The main components are the grasping lever, side panels, cutter holder, cutter fixing bolts, etc.  
The cutter system installation process begins when the operator or the cutter-changing robot places the entire cutter system into the cutter holder by holding the grasping lever. Just rotate the high-strength bolt and drive the shift fork to move up. At this time, the wedge will swing in the direction of the cutter holder side panel around the long axis, and the wedge top will extend into the groove inside the cutter holder to limit the displacement.  
Conversely, when the cutter system needs to be removed, just rotate the high-strength bolt in the opposite direction and drive the shift fork to move down. At this time, the wedge will swing in the direction of the disc cutter around the long axis and the wedge top will leave the groove inside the cutter holder. So that the operator or the cutter-changing robot can lift the entire cutter system from the cutter holder through the grasping lever.  
The core advantage of the new TBM integrated cutter system is that it simplifies and integrates the structure of the cutter system, greatly reduces the operation steps, improves the disc cutter replacement efficiency, and provides the possibility for the cutter-changing robot popularization. The disassembly performance comparison between the new and the traditional cutter system is shown in Table 1.  
At the same time, the overall weight of the new TBM integrated cutter system is significantly reduced compared with the traditional cutter system because of the emphasis on the lightweight design at the beginning of the design process (the total weight of the new cutter system is only 354.4 kg, which is significantly less than that of the traditional cutter system). The smaller weight is helpful for the operation of the operator or the cutter-change robot, which can improve the construction efficiency.