Design of PLC Controlled Stepping Motor Indexing
1 Introduction
The indexing and punching on the inside of the large bearing and the outer casing are the key processes in the bearing. Its process level and quality directly affect the quality, life and manufacturing cost of the bearing. At present, the indexing method of large bearing inner and outer casings in the bearing industry generally adopts manual indexing method, which has low indexing precision, large cumulative error, low work efficiency, and high labor intensity of workers, which has a great influence on the improvement of bearing performance. The large-scale numerical control indexing head developed by us adopts PLC programmable controller to control the stepping motor to drive the worm and worm to perform automatic indexing on the workpiece. The structure is simple and the manufacturing cost is low, which solves the practical problems in production.
2, the overall design
A stepper motor is an open-loop control element that converts an electrical pulse signal into an angular displacement or a linear displacement. In the case of non-overloading, the speed and stop position of the motor depend only on the frequency of the pulse signal and the number of pulses, and are not affected by the load change, that is, a pulse signal is applied to the motor, and the motor rotates through a step angle. Its important feature is that there are only periodic errors without cumulative errors. The operation of the stepping motor is driven by a stepper motor driver. This device converts the pulse signal from the control system into the angular displacement of the stepper motor, or: the control system sends a pulse signal every time. The drive rotates the stepper motor by one step angle. Therefore, the speed of the stepper motor is proportional to the frequency of the pulse signal. Therefore, controlling the frequency of the stepping pulse signal can accurately adjust the speed of the motor; controlling the number of stepping pulses can accurately position the motor.
In the CNC indexing head we designed, we use this linear relationship to electrically control with PLC, write the indexing algorithm program, control the frequency and pulse number of the pulse signal, and the stepper motor drives the worm gear to accurately perform the workpiece. Indexing, and can achieve a variety of electrical control such as adjustment, manual indexing, automatic indexing.
The electrical control scheme is PLC+ stepper motor and subdivision drive + digital scale. PLC selects DVP20EH00T, AC220 volt power supply 20-point 200HZ transistor output type; according to the classification accuracy requirements, select the subdivided driver and stepper motor, consider the torque of the workpiece when indexing M=FR=fNR, calculate the maximum torque as 27Nm. The stepping motor is selected according to the characteristics of the moment frequency, and the 130BYG350A three-phase hybrid stepping motor and the matching subdivision driver MS-3H130M are selected.
