From Beginner to Expert: Core Application Techniques of Siemens PLC in Electronic Component Production

The automation system for electronic component production requires high precision and stability. Siemens PLC, with its reliability and flexibility, has become the preferred control platform.

1. Hardware Configuration

Selection of PLC and Expansion Modules

The core control system of the electronic component production line uses the Siemens S7-1500 series PLC, with the main CPU being the 1516F-3 PN/DP, which meets the demands for high-speed processing and safety functions. For expansion modules:

• Digital Input Module: 16 points SM 521 DI 16xDC24V (for limit switches, buttons, sensor signal acquisition)

• Digital Output Module: 16 points SM 522 DO 16xDC24V/0.5A (for start/stop control, indicator lights, solenoid valve control)

• Analog Input Module: 8 points SM 531 AI 8xU/I/RTD/TC (for temperature, pressure, displacement sensor signal acquisition)

• Analog Output Module: 4 points SM 532 AO 4xU/I (for frequency speed control, proportional valve control)

I/O Point Allocation Table

Digital Input (DI):

• %I0.0~%I0.7: Start, stop, reset buttons

• %I1.0~%I1.7: Safety signals such as safety doors, emergency stops, over-travel

• %I2.0~%I2.7: Position signals for each station

• %I3.0~%I3.7: Material detection signals

Digital Output (DO):

• %Q0.0~%Q0.7: Motor start/stop control

• %Q1.0~%Q1.7: Solenoid valve control

• %Q2.0~%Q2.7: Indicator light control

Analog Input (AI):

• %IW64: Temperature sensor input

• %IW66: Pressure sensor input

• %IW68: Displacement sensor input

Analog Output (AO):

• %QW64: Main conveyor speed control

• %QW66: Heater temperature control

2. Control Program Design

Program Architecture Design

The control program for electronic component production adopts a hierarchical structure design to improve code reusability and maintainability:

• OB1: Main loop, responsible for calling various function blocks

• OB35: 100ms cycle interrupt for quick response handling

• OB82: Diagnostic interrupt for handling module faults

• OB86: Rack fault interrupt

• FB1~FB10: Process function blocks, such as material conveying, precise positioning, temperature control, etc.

• DB1~DB20: Data blocks corresponding to function blocks, storing parameters and states

Function Block Design

Taking the precise positioning function block (FB3) as an example:

// FB3: Precise Positioning Function Block

// Input parameters: Target position, maximum speed, acceleration time, deceleration time

// Output parameters: Current position, current speed, positioning completion flag

// Static variables: Position error, PID parameters, motion state


// Step 1: Calculate position error

#Position_Error := #Target_Position - #Current_Position;


// Step 2: Calculate output speed based on error (PID algorithm)

#Speed_Output := #Kp * #Position_Error + 
                #Ki * #Integrated_Error + 
                #Kd * (#Position_Error - #Last_Error);


// Step 3: Limit output speed range

IF #Speed_Output > #Max_Speed THEN
    #Speed_Output := #Max_Speed;
ELSIF #Speed_Output < -#Max_Speed THEN
    #Speed_Output := -#Max_Speed;
END_IF;


// Step 4: Determine positioning completion condition

IF ABS(#Position_Error) < #Position_Tolerance AND
   ABS(#Speed_Output) < #Speed_Tolerance THEN
    #Positioning_Done := TRUE;
ELSE
    #Positioning_Done := FALSE;
END_IF;


// Step 5: Update historical data

#Last_Error := #Position_Error;
#Integrated_Error := #Integrated_Error + #Position_Error;

Status Control Design

The state machine design pattern is used to manage the operating states of the equipment, including six states: initialization, standby, running, paused, alarm, and maintenance:

// State Control Function Block (FB1)

CASE #Machine_State OF
    0:  // Initialization state
        // System initialization code
        IF #Init_Done THEN
            #Machine_State := 1; // Switch to standby state
        END_IF;
        
    1:  // Standby state
        // Standby state code
        IF #Start_Command AND #No_Alarm THEN
            #Machine_State := 2; // Switch to running state
        END_IF;
        
    2:  // Running state
        // Running state code
        IF #Pause_Command THEN
            #Machine_State := 3; // Switch to paused state
        ELSIF #Alarm_Active THEN
            #Machine_State := 4; // Switch to alarm state
        END_IF;
        
    3:  // Paused state
        // Paused state code
        IF #Resume_Command THEN
            #Machine_State := 2; // Return to running state
        ELSIF #Stop_Command THEN
            #Machine_State := 1; // Return to standby state
        END_IF;
        
    4:  // Alarm state
        // Alarm handling code
        IF #Alarm_Reset AND NOT #Alarm_Active THEN
            #Machine_State := 1; // Return to standby state
        END_IF;
        
    5:  // Maintenance state
        // Maintenance mode code
        IF #Maintenance_Done THEN
            #Machine_State := 0; // Return to initialization state
        END_IF;
END_CASE;

3. System Debugging Methods

Step-by-Step Debugging Method

The debugging of the electronic component production line adopts a “bottom-up” strategy to ensure that each link operates normally:

1. I/O Point Testing: Test each input and output point one by one to verify the correctness of wiring and address mapping

2. Unit Function Testing: Test each function block, such as material conveying, positioning, heating, etc.

3. Interlock Testing: Test the interlocks between each process according to the production flow

4. Full Process Testing: Complete production process testing to verify automatic, manual, and single-step modes

Parameter Tuning Steps

Taking the temperature control loop as an example:

1. Initial Parameter Determination: Determine initial PID parameters based on system characteristics

2. Step Response Testing: Provide a step signal and observe the system response curve

3. Parameter Fine-Tuning: Adjust PID parameters based on the response

• Excessive overshoot: Decrease proportional gain or increase derivative time

• Slow response: Increase proportional gain or decrease integral time

• Significant oscillation: Decrease proportional gain or increase derivative time

Interference Testing: Introduce artificial interference to test the system’s anti-interference capability

Parameter Confirmation: Verify control performance at different operating points

4. Operation Interface Design

Interface Layout Description

The HMI interface for the electronic component production line is designed based on WinCC and includes the following key screens:

1. Main Screen: Overview of the entire line status, production statistics, alarm notifications

2. Process Parameter Screen: Setting and monitoring of key process parameters

3. Manual Operation Screen: Manual control of unit devices

4. Trend Curve Screen: Real-time trends and historical trends of key parameters

5. Alarm Screen: Current and historical alarm queries

6. User Management Screen: Management of operational permissions

Parameter Setting Description

The parameter setting interface is designed in layers based on importance and frequency:

1. Production Parameters: Daily parameters adjustable at the operator level, such as speed, temperature, etc.

2. Process Parameters: Parameters adjustable at the technician level, such as PID parameters, positioning accuracy, etc.

3. System Parameters: Parameters adjustable at the administrator level, such as communication settings, alarm limits, etc.

Each parameter is set with upper and lower limits and provides different input methods based on type (sliders, input boxes, drop-down lists, etc.).

5. Fault Diagnosis and Troubleshooting

Common Fault Analysis

Common faults in the electronic component production line and their diagnostic methods:

1. Inaccurate Positioning

• Cause: Sensor drift, mechanical gap changes, inappropriate PID parameters

• Diagnosis: Check the deviation between current position and target position, analyze PID computation process variables

• Solution: Calibrate sensors, optimize PID parameters, check mechanical components

Unstable Temperature Control

• Cause: Insufficient heater power, slow sensor response, inappropriate PID parameters

• Diagnosis: Analyze temperature fluctuation trends, check heater duty cycle

• Solution: Adjust PID parameters, optimize sensor layout, replace with appropriately powered heater

Communication Interruption

• Cause: Network connection issues, device address conflicts, communication timeouts

• Diagnosis: Check communication status words, network connection status

• Solution: Check network connections, reconfigure communication parameters, eliminate electromagnetic interference

Use of Diagnostic Tools

For fault diagnosis in the electronic component production line, the following tools are recommended:

1. STEP 7 Online Diagnostics: Real-time monitoring of program execution, variable values, and communication status

2. ProDiag: Program logic monitoring and fault localization

3. SIMATIC Trace: High-speed data acquisition and waveform analysis, suitable for precision control loop issues

4. Network Analyzer: Analyze PROFINET communication issues

Conclusion and Outlook

The application of Siemens PLC in electronic component production is crucial for precise control, reliability, and flexible expansion. Feel free to share your practical experiences in the comments!

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