# Development and Performance Evaluation of an Integrated Disc Cutter System for TBMs
## 1 Introduction  
Tunnel boring machines (TBMs) have become the main tool of tunnel construction because of their high efficiency and safety compared with traditional blasting methods [1]. Disc cutters are parts that are distributed on TBM cutterheads according to certain rules. The weight of a 19 inch disc cutter is about 179 kg, as shown in Figure 1. As the key cutting tool of TBMs, the disc cutter acts directly with rock or soil, which easily causes it to experience wear or damage in the working process [2]. Some scholars have developed prediction models to calculate the performance of the disc cutter, which improves the safety of TBM construction to a certain extent [3, 4, 5, 6]. Therefore, to make TBMs reliable, replacing the disc cutter is an essential process in TBM operation. However, the replacement tasks currently rely on manual work. The workers who change cutters are exposed to muddy water, high pressure, tunnel collapse, rock burst, and other problems when they are performing cutter-changing tasks underground. According to statistics, accidents due to cutter-changing operations have become the main source of accidents in the process of tunnel construction [7]. In addition, the changing processes occupy over a third of the whole construction period [8]. The same problems are experienced with micro tunnel boring machines (MTBMs), where the difficulties of changing disc cutters are higher due to the reduced dimensions of the tunnels: It takes 2 or 3 days to replace the cutters [9, 10]. The danger and low efficiency of manually changing disc cutters has encouraged engineers to study technologies for the automatic changing of disc cutters. The research into technologies for the automatic changing of cutters is mainly divided into two popular topics. The first is the study of heavy-load robots to change cutters (load greater than 400 kg), which can adapt to the narrow space of the TBM and high pressure and high humidity environments [11]. Its function is to disassemble and transport the old and new cutters. Initially, scholars and enterprises [11; 12] used the traditional industrial robot body (6R) and installed a special end to implement cutter changes. The advantage of this kind of approach is that it can realize many kinds of actions. However, due to the limited space in the TBM and the load ratio of industrial robots, the cutter changing range of traditional industrial robots is limited, so they are not used in engineering applications. Recently, researchers [13; 14; 15; 16; 17; 18] have begun to design other robot configurations (Combination of R and P) to achieve large load ratios and large working ranges. However, the disadvantage of this kind of robot is that its disassembly and assembly actions are relatively simple. Therefore, the second hot topic for the automatic changing of cutters is to design a new integrated cutter system to adapt to the disassembly and assembly of a robot with sample actions. The traditional cutter system (TCS) has various kinds of parts, such as bolts, screw locking blocks, fixing blocks, and cutters, as shown in Figure 2. Obviously, the disassembly and assembly of the TCS is complex. Therefore, it is necessary to design an integrated cutter system (ICS) that is easy for a robot with low flexibility to disassemble and assemble. The French companies BOUYGUES and NFM [12] launched a link-slider mechanism type ICS, which does not require the structure of the cutter head to be changed. Moreover, the interface of the ICS is relatively simple. The Robot Innovation Center of the German Research Center for Artificial Intelligence (DFKI) [14] developed a slider-type ICS that has the advantages of a large impact load and simple interface at the end of the robot. HongRun Construction Group Co., Ltd. [11] proposed an ICS that uses an eccentric circle mechanism to lock the cutter. Figure 1: Layout of the disc cutter in a tunnel boring machine (TBM).