I. Overview (Background)
This grinder is mainly used for grinding specific parts of auto parts to a specified diameter, requiring stable and reliable operation and high machining accuracy. A grinder is equipped with two servos for spindle positioning and grinding wheel feed. The old scheme is that the numerical control system is used as the main controller, PLC+ servo is used for spindle positioning control, and the pulse is sent to the grinding wheel feed servo to execute the corresponding grinding action. In this scheme, the CNC system still acts as the master controller, but the basic actions are implemented by the servo, which saves the cost of the PLC, and the wiring is simple and the control effect is better.
Second, the process requirements
1. Spindle positioning: When the workpiece is machined by the grinding machine, after the workpiece is gripped by the spindle, the workpiece is rotated. After the machining is completed, when the rotation is stopped, the spindle may not be fixed because of the stop position of the spindle. The workpiece may be stuck on the fixture and cannot be removed, affecting the next workpiece. Processing. Prior to the change, the customer used [PLC+Servo] to achieve the spindle positioning and stopping function, the system was complex and the cost was high. According to the customer's request, the use of dedicated servos is improved, and the spindle stops at a fixed position after operation, which facilitates the clamping and removal of workpieces.
2. Grinding wheel feeding: When grinding the workpiece, the grinding wheel feeds at a high speed to a low speed, and gradually approaches the target position for processing, and returns to the starting position after the machining is completed. Before the change, the control system sends pulse control, which is divided into three stages and the control is complicated. According to the customer's request, using dedicated servo improvements, the specified distance is automatically travelled at the specified speed.
Third, the program
1. Spindle positioning: when the running signal is invalid, the servo locks; when the running signal is closed, it runs at a constant rotating speed; when the running signal is off, the number of pulses is automatically compensated according to the mechanical transmission ratio, and the travel is performed to the positioning point and the servo is locked.
2. Grinding wheel feeding: when the feed signal is invalid, the servo locks; when the main control system outputs the feed signal, it automatically switches the speed according to the stroke, and is divided into three segments. After reaching the designated position, the corresponding signal is output to the main control system; Wait for the main control output feed signal is invalid, return to the starting point according to the set speed, after the completion of the servo lock, output corresponding signal to the main control system.
Fourth, the program advantage
1, the disadvantages of the traditional way:
(1) Spindle positioning: It is necessary to add a PLC and write a PLC program. The cost is high and the system is complicated. (2). Grinding Wheel Feed: The control system has complicated programming, poor stability and low accuracy.
2, the advantages of this program:
(1) Spindle positioning: Substituting a dedicated servo for [PLC+Common Servo], it is easy to use and low cost.
(2). Grinding Wheel Feed: Simplify the system. According to simple instructions, perform specified actions. The control is simple and the precision is high.
Fifth, the implementation of this program
1. Wiring schematic (system block diagram)
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