Unit 5 Numerical Control (NC) (Điều khiển số) Sections: 1. Fundamentals of NC Technology 2. Computer Numerical Control (CNC) 3. Distributed Numerical Control (Kết nối nhiều máy NC) 4. Applications of NC (Ứng dụng của NC) 5. NC Part Programming (Lập trình để gia công chi tiết trên máy NC) Numerical Control (NC) Defined Định nghĩa Programmable automation (lập trình tự động) in which the mechanical actions (chu trình công nghệ) of a ‘machine tool’ are controlled by a program containing coded alphanumeric data that represents relative positions between a work head (e.g., cutting tool) and a work part Program Program Instructions Instructions Transformation Process Hình dạng, vật liệu, tính chất hóa học Machine Machine Control Control Unit Unit Power Power NC Coordinate Systems For flat and prismatic (block-like) parts:  Milling and drilling operations  Conventional Cartesian coordinate system  Rotational axes about each linear axis For rotational parts:  Turning operations  Only x- and z-axes Motion Control Systems (Điều khiển chuyển động) Point-to-Point systems (Điểm)  Also called position systems  System moves to a location and performs an operation at that location (e.g., drilling)  Also applicable in robotics Continuous path systems (Đường)  Also called contouring systems in machining  System performs an operation during movement (e.g., milling and turning) Interpolation Methods (Nội suy) 1. 2. 3. 4. Linear interpolation (đường thẳng)  Straight line between two points in space Circular interpolation  Circular arc defined by starting point, end point, center or radius, and direction Helical interpolation  Circular plus linear motion Parabolic and cubic interpolation  Free form curves using higher order equations Absolute vs. Incremental Positioning Tọa độ tuyệt đối và tương đối Absolute positioning Move is: x = 40, y = 50 Incremental positioning Move is: x = 20, y = 30. Computer Numerical Control (CNC)  Storage of more than one part program