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The feeddrive of a CNC machine is a mechatronic system consisting of motor, mechanical transmission devices and worktable. The accuracy and precision of the feeddrive system determines the quality of the final part. Hence close control of the drive system is very important. Accurate modeling of this system and its simulation helps in system design and parametric optimization. In this paper, bond graph based approach has been used to model the feeddrive of a CNC machine. This technique is based on power flow and uses basic component types to develop models for complex multi-physics systems. The governing equations can be algorithmically derived from a visual representation of the system. In this model all linear and nonlinear effects such as backlash, stick-slip friction and cutting forces have been accounted for. The model is also enhanced through the addition of a control loop for position and velocity.

When an electric motor is switched off, an amount of energy, dependent on the design of the motor, can be emitted to the power device. Some of this energy is stored in the capacitors and needs to be discharged when the circuit is shut off. Also, the current through the inductive components changes rapidly, causing a large voltage to be discharged from the circuit. This phenomenon poses potential problems in automotive applications since this energy surge, known generally as a conducted transient, could cause damage to other electrical devices that share the same power grid. Automotive motors generally also have radio frequency interference filtering devices, which are significant contributors to this conducted transient energy.