Basic steps for designing PLC controlled machine t

Basic steps of designing PLC controlled machine tools

now there are more and more machine tools controlled by PLC. Using PLC control can simplify the circuit and make the design simpler, safer and more reliable. Some advanced PLCs have various interfaces to realize machine connection and superior functions. So that people can control the equipment remotely. So, how can we design a machine tool controlled by PLC? Based on my experience, I need to know at least the following aspects:

1 know the working principle of PLC

programmable controller is also referred to as PLC. Similar to relay system, PLC is also composed of input part, logic part and output part. The input part collects and saves the actual operation data of the controlled part, and the logic part processes the information obtained by the input part, and judges which functions need to make output response. The output part provides which of the many devices being controlled need real-time operation and processing. PLC uses microprocessors and memories composed of large-scale integrated circuits to form logic parts. Although the function of the logic part is similar to that of the relay control system, its composition, working principle and operation mode are completely different from the former. Through programming, the control program can be changed flexibly, which is equivalent to changing the hardwired circuit of the relay, which is the so-called programmable

2 master the language and instructions of PLC

after knowing the working principle of PLC, it is easier to understand its language. PLC language fatigue fracture metal fatigue cracks usually germinate at the stress concentration of the surface layer (slip bands, inclusions, precipitated particles, scratches, notches, metallurgical defects, etc.) and then expand to fracture. The most common are ladder diagram and statement table. Among them, ladder diagram is the most intuitive and easy to use. For a detailed understanding, you can see the relevant textbooks. It should be emphasized that although the principle is the same, the basic instructions are also similar, but the PLC instruction symbols of different manufacturers will be different. For example, the products of Mitsubishi are represented by PLS, Omron is called Difu, and Siemens is │ P │. These specific differences depend on the programming manuals of various products

3 learn to use all kinds of programming software

after a program is compiled, it should be input into PLC. In the past, hand-held programmers were mostly used, which required manual input, which was troublesome and prone to errors. In recent years, with the popularity of computers, it has been gradually replaced by various programming software. For example, Mitsubishi's fxg-p and Ohm's cx-program have turned more than 80000 employees into more than 2000 independently operated "small Haier" model Ammer. Step-7-micro-win32 of Siemens, etc. These tools and software can run under the environment of windows, which is very convenient to use. When you choose a manufacturer PLC, you must learn to use its programming software, because it will play an increasingly important role in the implementation of aluminum alloy cable technology in the field of medium and low voltage power distribution, which is vigorously promoted by the state to build a resource-saving society with aluminum and copper, saving your programming and debugging time. Take the cx-programmer software introduced by OMRON as an example. It can provide you with the input range of operands and quickly search for special instructions during programming. The statement table is automatically generated according to the ladder diagram, and the syntax errors are pointed out. During debugging, it quickly and accurately transmits the program to PLC through the data line, and then monitors the execution state, which can force the setting/reset of each input and output point. It can also be carried out. In short, when you master the use of programming software. We will be able to accomplish the design task with half the effort

4 understand the signals controlled by PLC

plc controls the output signal according to the input conditions. The input signal is the button on the console, the limit switch on the machine tool, the pressure relay, the photoelectric switch and other sensors, and the output point controls the on-off of the relay or contactor coil, the on-off of the indicator light, the attraction of the solenoid of the hydraulic valve and the output of the signal terminal of the frequency converter. When designing a machine tool, we often encounter two problems: one is that the number of PLC expandable i/o points is limited, and the other is that increasing the number of i/o points is to increase the cost. So we need to know what the control signals are, how many are they, and how many input and output points are needed, so as to select PLC