Why do auxiliary workshops use PLC to complete control tasks?

The application fields of programmable controllers: logic control of switching quantities, closed-loop control of analog quantities, intelligent control of digital quantities, data acquisition and monitoring, communication networking and distributed control.

Other control methods: single-chip microcomputer, assembly language, VB, C, C++, etc.

It's hard to say, it generally depends on your engineering requirements, if your program is well written, the program steps can be reduced a lot, and the scanning time will be ultra-short.

The specific internal relay depends on the individual project. 9032--60291

The PLC is cyclically scanned, from top to bottom, from left to back, and so on.

Specifically, the control tasks you are talking about, there are a lot, automatic control, machine tools, constant pressure water supply, and so on.

When programming, in addition to inputs and outputs, most of the logic processing requires intermediate relays to connect and can be used when you need to use relays.

Absolutely. PLC is the brain of the entire CNC machine. It is the center of gravity of the CNC system. Hehe.

The control system of a device is generally composed of PLC, CNC, PC

PLCs are generally responsible for the input and output of action signals and the sequence of actions, and function similarly to the brainstem of the human brain.

CNC is generally responsible for the control of servo motors and simple machining procedures, and functions similarly to the cerebellum of the human brain.

PCs are generally responsible for complex logic and curve operations and function similarly to the brain of a human brain.

In fact, there is no obvious boundary between these three in the application, such as the PLC can control the servo motor after plugging in the position control board, and some PLC is even powerful enough to do multi-axis linkage control, and the function is close to CNC.

The CNC itself comes with a PLC and is equipped with a small number of IO points, which are generally for servo motors, such as mobile platform switches, in-situ switches, etc. There are also manufacturers to make the CNC computer system as powerful as the PC, and to further expand the IO point with PLC, so that the whole system looks like neither PLC nor PC only a set of CNC system, the general machining center is like this, using their own brand of special integrated system.

The PC controls the external CNC through an I-O board plugged into the motherboard, and I have seen an NC system where one device controls 7 servo motors at the same time with a single PC. Of course, the NC of each servo motor is very simple, just a servo amplifier and a limited number of IO points, and there is no interactive interface. Three of the seven motors are linked, and this linkage is realized by a PC.

However, which part of the program is executed by the PC is controlled by the PLC.

You can try the same logic function, without PLC, completely built with relays. You'll find that more relays are needed, and the complexity of the circuitry increases a lot. And it's not flexible, the logic has to change a little bit, and you have to change the circuit.

PLC is designed to replace relay logic circuits. With PLC, the circuit is much simpler and much more flexible. Complex control logic can be easily implemented programmatically.

The PLC control system has high reliability, and the PLC can communicate with a variety of external devices, and can be combined into a system of various scales and control functions by establishing communication protocols. In addition, PLC also has the characteristics of low power consumption, high control accuracy and good versatility.