The central region model (CRM) cyclotron is the experimental platform for the key technology study of a high intensity beam cyclotron.In this paper we introduce the spiral inflector and central region designed for the CRM cyclotron,including the physical design,the numerical control machining and the installation precision control techniques.The shape of electrodes is complex,and machining with a strict tolerance must be done by a numerical control machine tool with the number of its axles no less than 4.The electrodes of central region were finished by using 3-axle machine tools.The size of gaps between the ground and Dee tip is very important,a special device was made to guarantee the installation precision,and the error of gaps was controlled within±0.05mm.
