Cutter head movement concept

Abstract: This master thesis has been conducted at Svea Teknik on behalf of Atlas Copco and deals with the design of a cutter head motion system for mechanical rock excavation machines. Mechanical rock excavation allows tunneling to be done with just one machine in a continuous process. Such a machine is called a tunnel boring machine (TBM) and excavates rock by pressing a rotating cutter head with disc cutters against the rock face. By moving the cutter head in different patterns, tunnels of different profiles and sizes can be excavated. Atlas Copco has currently a conceptual TBM with an associated cutter head motion solution attached. The main task of this master thesis is to examine if an alternative solution to this motion system could be incorporated to the conceptual TBM, and to develop this solution to a functional concept design. In order to find a suitable alternative design nine concepts where generated and evaluated against the current concept solution using a weighted PUGH-matrix. The chosen concept was refined into a final functional concept design. The produced concept design consists of a two part linkage arm construction connected via a cylindrical joint. At one end of the articulated arm the cutter head is located and at the other end the linkage arm is connected to a rotatable base which allows the arm to rotate and swing to the sides. This rotatable base is in later turn supported by a base structure mounted to the main body of the current concept machine. All motion is achieved by hydraulic cylinders which are mounted in their respective ends using spherical bearings to minimize the need of narrow tolerance spans. The benefits of this alternative design are a greater choice of tunnel profiles along with simpler bearing solutions which may reduce manufacturing- and service costs. The downside is instead added weight to the front of the machine which will move the center of mass closer to the cutter head. This may have a negative effect on the machine propulsion system.