Servo motor-based CNC machine, design, fabrication and control.
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In this project we develop a prototype CNC (Controlled Numerical Computer) machine based on DC servo motors and feedback control systems. Nowadays, CNC machines technology is one of the most important modern technologies for metal and wood forming industries as the machine is fully automated using digital electronics, which enables it to perform very accurate tasks with high production rates. A typical CNC machine consists of 3 main parts: the spindle, which spins cutting tools for forming objects, the frame and gantry, the former carries most of the parts of the machine including the gantry, the motors, the guide rails and the electronic parts and the latter consists of moving perpendicular axes (via electric motors), which enable the spindle to move in the three directions x, y, z and Instrumentation, which consists of all electronic parts including encoders, sensors, power supply, microcontrollers, etc. In this project, we consider DC servo motor based CNC machines where feedback servomotor systems are adopted to control the positions of the three axes of the machine instead of using stepper motors. This will: 1-Improve system controllability: The use of feedback allows the positions and speeds of the axes to be fed back instantaneously to the microcontroller, then, it can use such information to update its commands to the actuators taking into consideration all external and internal effects on the machine, which are reflected in the measured data, to improve the operation of the whole system. 2-Improve system efficiency: Servo motors together with feedback can improve system efficiency related to electric power consumption up to approximately 90%, whereas stepper motors based machines have less efficiency of about 70% due to the large power consumption.