PLC direct control of the hottest stepping motor

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PLC direct control of stepping motor

direct control of programmable controller of stepping motor can significantly reduce the cost of automatic production line control system of modular machine tool. This paper introduces the method of using PLC to control the NC sliding table driven by stepper motor, servo control, drive and interface, as well as the software logic of PLC control of stepper motor

1 overview

in the automatic line of modular machine tools, three kinds of slides are generally set according to different machining accuracy requirements (1) hydraulic slides are used in rough machining processes with large cutting volume and low machining accuracy requirements; (2) Mechanical slide, used in semi finishing process with medium cutting quantity and certain machining accuracy requirements; (3) CNC slide table is used in finishing processes with small cutting amount and high machining accuracy requirements. Programmable controller (PLC) is widely used in industrial automatic control because of its strong versatility, high reliability, simple instruction system, simple programming, easy to learn, easy to master, small size, great difficulty, less maintenance work, convenient installation of field interface and a series of advantages. Especially in the control of the automatic production line of modular machine tools and the s, t, m function control of CNC machine tools, the export unit price is improving, showing its excellent performance. Where is the rubber tensile testing machine mechanism applied to the numerical control slide control of the modular machine tool automatic production line, the numerical control system of the unit can be omitted, and the cost of the control system of the unit can be reduced by 70~90%. Even it only occupies 3~5 i/o interfaces and 4 hours of the automatic line control unit PLC. It should be fully considered for large production lines. With the hardware loop distributor, although the hardware structure is slightly more complex, it can save the number of i/o ports of PLC. At present, there are a variety of special chips available in the market. The stepping motor power driver amplifies the control pulse output by PLC to tens to hundreds of volts, a few to a dozen amps. Generally, the output interface of PLC has a certain driving capacity, while the load capacity of the usual transistor DC output interface is only ten to dozens of volts and tens to hundreds of milliamps. However, for the power stepping motor, the tensile test (stress-strain test) is required. 1. Generally, the two ends of the material sample are clamped on two fixtures with a certain distance between them to calculate the driving capacity of tens to hundreds of volts and a few to a dozen A. therefore, the driver should be used to amplify the output pulse

5.2 interface of programmable controller

if the servo mechanism adopts hardware circular distributor, the number of i/o ports occupied by PLC is less than 5 points, generally only 3 points. Among them, I port occupies a little bit as the starting control signal; The O port occupies 2 points, one of which is the pulse output interface of PLC, connected to the clock pulse input end of the hard ring of the servo system, and the other is the steering control signal of the stepping motor, connected to the phase sequence distribution control end of the hard ring, as shown in Figure 3; When the servo system adopts software circular distributor, its interface is shown in Figure 4

6 application examples and conclusions

the open-loop servo mechanism controlled by PLC is used in the NC slide of a large production line. Each slide only occupies 4 i/o interfaces, which saves the CNC control system. Its pulse equivalent is 0.01~0.05mm, and the feed speed is vf=3~15m/min, which fully meets the process requirements and machining accuracy requirements. (end)

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