Seven-step method for PLC project debugging - Mitsubishi PLC

Many novices in the electrical industry are not sure how to start debugging after completing the planning links such as electrical control cabinets and PLC programs. Perhaps some people due to inappropriate debugging methods have led to PLC burning and other problems, so how should the planned electrical system be debugged? Follow these seven steps.

Seven-step method for PLC project debugging - Mitsubishi PLC

Seven-step method for PLC project debugging - Mitsubishi PLC

1. Check the circuit according to the drawings (under the condition of no power transmission)

The drawings of the general PLC system include two parts: the drawings in the cabinet and the drawings outside the cabinet; The drawing in the cabinet refers to the wiring diagram inside the cabinet; The drawings outside the cabinet are the wiring diagrams of everything connected to the electrical cabinet. This part of the requirements is to look at:

1. Whether the drawing planning is reasonable, including the capacity of various components, etc.

2. Check whether the components are connected in strict accordance with the drawings according to the drawings.

In this process, the most important place to pay attention to is to check the power supply

1. Make sure that there is no short circuit in the circuit.

2. Make sure that the strong and weak currents are not mixed together

Since the PLC power supply is 24V, once the 220V is connected to the PLC due to wiring error, it is very simple to burn the PLC or widening module.

2. Check the external circuit of the PLC, which is also commonly known as "dotting"

After the power supply is acknowledged, the input and output points are tested, which is commonly known as "dotting", and the test IO points need to be tested one by one, including the operation button, the emergency stop button, the operation indicator light and the cylinder and its limit switch, etc., the specific method is that one person operates the button on the field side, etc., and the other person monitors the input and output signals in the PLC; For large systems, test sheets should be set up, i.e. marked after the test. If it is found that there is a wiring fault during the construction process, the local demand will be dealt with immediately.

In this step, it should be noted that you need to back up the program and then empty the program in the PLC, or disable the program to avoid the action of the device caused by the test.

3. Check the mechanical structure and test the motor load

This step needs to check whether the mechanical structure is tightened, etc., whether the motor load is well maintained accordingly, to avoid accidents caused by accidents, and after the end of the inspection, it is required to manually test the operation of the equipment, such as the positive rotation motor, whether the demand test line is missing and live test, the inverter class sets the corresponding parameters and optimizes the motor, static identification or dynamic identification, etc.

The need to pay attention here is that some special loads, such as the load requirements of vertical classes moving up and down, are required to be carried out by professionals to avoid testing incidents due to improper control.

Fourth, debug the manual/semi-active form and related logical relationships

After testing both the IO point and the load side, the next step is to debug in manual form. The manual form here can also be called the semi-active form, which does not directly press the solenoid valve or contactor by hand, but refers to the drive of the device through the button or HMI button, etc., which corresponds to the active situation.

The manual form of the test can divide the active form according to the person's wishes, and facilitate the test procedure.

The most important thing in this link is to test the safety function, that is, to test whether the safety function of the emergency stop, safety grating, etc. has the corresponding effect under the operation of the equipment.

Fifth, according to the production process debugging active form

After semi-active commissioning, active work can be further commissioned. This link is the most important, the need to test various chains according to the production process, including logic chains, safety chains, etc., and to test several more operation cycles to ensure that the system can be correctly connected to operate.

Sixth, the test of special craft

In addition to logic control, there are many broadened functions in the PLC system, such as PID control, etc., when these logic debugging is completed, you can start to debug analog and pulse control.

The most important thing is to select the appropriate control parameters. Generally speaking, this process is relatively long. It is necessary to adjust patiently, and the parameters should also be selected in a variety of ways, and then the best one should be selected. For some PLCs, the PID parameters can be obtained by autotuning. But this self-tuning process can only be completed at the moment when the demand is comparable.

7. The process of accomplishing all of the above

The whole debugging is basically completed, and then it is time to pre-produce the process, pre-production is the pre-production operation test, at this stage can cooperate with the production to carry out some special tests, such as whether the production rhythm is satisfied, whether the safety function can be effective under the load situation, etc., generally successive production must be able to deliver after the moment.

Novices especially need to pay attention to the power supply, I remember when I debugged the first project many years ago, because the construction unit connected the 220V contacts and 24V contacts of the rope switch of the large belt to the wrong (the rope switch of the belt is a safety device, two sets of contacts, one is 220V to disconnect the control loop, and the other group is 24V to enter the PLC), resulting in the burning of a digital input template, and then it was a long memory, and then the time of debugging must distinguish between 220V and 24V, and there was never a problem.

Seven-step method for PLC project debugging - Mitsubishi PLC

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