The control system of facial mask production equipment directly affects product quality and production efficiency, a reasonable PLC control scheme is the key to ensuring efficient and stable production.
1. Hardware Configuration
1.1. PLC and Expansion Module Selection
The core of the facial mask production line control system uses the Siemens S7-1200 series CPU 1214C DC/DC/DC model, which has 14 digital input points, 10 digital output points, and 2 analog input points, suitable for the control needs of small to medium-sized facial mask production equipment. Based on the actual I/O point requirements, the following expansion modules are configured:
SM 1223 DC/DC: 16DI/16DO digital expansion module (for sensor signal acquisition and actuator control)
SM 1231 AI: 4-point analog input module (for monitoring temperature, pressure, liquid level, etc.)
SM 1232 AQ: 2-point analog output module (for controlling inverters and proportional valves)
1.2. I/O Point Allocation Table
| Address | Function Description | Signal Type |
|---|---|---|
| I0.0 | Device Start Button | DI |
| I0.1 | Device Stop Button | DI |
| I0.2 | Emergency Stop Button Status | DI |
| I0.3 | Raw Material Liquid Level Upper Limit | DI |
| I0.4 | Raw Material Liquid Level Lower Limit | DI |
| I0.5 | Raw Material Supply Ready | DI |
| I1.0 | Facial Mask Forming Photoelectric Detection | DI |
| I1.1 | Cutting Completion Induction | DI |
| I1.2 | Packaging Position Detection | DI |
| Q0.0 | Main Pump Motor Start | DO |
| Q0.1 | Heater Control | DO |
| Q0.2 | Facial Mask Forming Motor | DO |
| Q0.3 | Cutting Actuator | DO |
| Q0.4 | Conveyor Belt Motor | DO |
| Q0.5 | Alarm Indicator Light | DO |
| IW64 | Temperature Sensor | AI |
| IW66 | Pressure Sensor | AI |
| QW80 | Main Pump Frequency Control | AQ |
2. Control Program Design
2.1. Program Architecture Design
The control program for the facial mask production equipment adopts a modular design, mainly including the following program blocks:
OB1 (Main Loop Program): System scanning and calling various function blocks
FB1 (Device Initialization): Device power-on initialization and self-check
FB2 (Raw Material Control): Raw material supply and liquid level control
FB3 (Temperature Control): PID control of facial mask solution temperature
FB4 (Facial Mask Forming): Control of forming process parameters
FB5 (Cutting Control): Accurate positioning and cutting control
FB6 (Packaging Conveying): Facial mask conveying and packaging control
FB7 (Alarm Handling): Abnormal monitoring and alarm handling
DB1 (Process Parameters): Data block for storing process parameters
DB2 (Operating Status): Stores device operating status
DB3 (Alarm Records): Stores alarm information
2.2. Function Block Design Example
Taking temperature control FB3 as an example:
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FUNCTION_BLOCK "Temperature Control"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
VAR_INPUT
Actual_Temperature : Real; // Current measured temperature value
Target_Temperature : Real; // Process required target temperature
Control_Enable : Bool; // Temperature control enable signal
END_VAR
VAR_OUTPUT
Heater_Output : Bool; // Heater control output
Temperature_Normal : Bool; // Temperature within normal range indication
Temperature_Alarm : Bool; // Temperature abnormal alarm
END_VAR
VAR
Temperature_PID : "PID_Compact"; // Temperature PID controller instance
Temperature_Deviation : Real; // Temperature deviation calculation value
Heating_Output_Value : Real; // PID calculated output value
Temperature_Upper_Limit : Real := 65.0; // Temperature upper limit alarm value
Temperature_Lower_Limit : Real := 45.0; // Temperature lower limit alarm value
END_VAR
// Temperature deviation calculation
#Temperature_Deviation := #Target_Temperature - #Actual_Temperature;
// PID controller call
#Temperature_PID(
Setpoint := #Target_Temperature,
Input := #Actual_Temperature,
Input_PER := #Actual_Temperature,
Output => #Heating_Output_Value,
Enable := #Control_Enable
);
// Heater output control
IF #Control_Enable THEN
#Heater_Output := #Heating_Output_Value > 0.0;
ELSE
#Heater_Output := FALSE;
END_IF;
// Temperature status judgment
#Temperature_Normal := (#Actual_Temperature >= (#Target_Temperature - 2.0)) AND (#Actual_Temperature <= (#Target_Temperature + 2.0));
#Temperature_Alarm := (#Actual_Temperature > #Temperature_Upper_Limit) OR (#Actual_Temperature < #Temperature_Lower_Limit AND #Control_Enable);
END_FUNCTION_BLOCK2.3. State Control Design
The facial mask production equipment adopts a state machine control model, with main states including: initialization, standby, production preparation, running, pause, alarm, and shutdown. The state transition logic is as follows:
plaintext
// Device state definition
VAR
Device_State : Int; // 0: Initialization 1: Standby 2: Production Preparation 3: Running 4: Pause 5: Alarm 6: Shutdown
END_VAR
// State transition logic (executed in the main loop)
CASE #Device_State OF
0: // Initialization state
IF #Initialization_Complete THEN
#Device_State := 1; // Transition to standby state
END_IF;
1: // Standby state
IF #Start_Button AND NOT #Alarm_Exists THEN
#Device_State := 2; // Transition to production preparation state
END_IF;
2: // Production preparation state
IF #Ready THEN
#Device_State := 3; // Transition to running state
ELSIF #Stop_Button THEN
#Device_State := 1; // Return to standby state
END_IF;
3: // Running state
IF #Pause_Button THEN
#Device_State := 4; // Transition to pause state
ELSIF #Alarm_Triggered THEN
#Device_State := 5; // Transition to alarm state
ELSIF #Stop_Button THEN
#Device_State := 6; // Transition to shutdown state
END_IF;
// Other state handling logic...
END_CASE;3. Fault Diagnosis and Troubleshooting
3.1. Common Fault Analysis
Common faults and solutions for facial mask production equipment:
Raw Material Supply Abnormality
Phenomenon: Raw material liquid level fluctuates frequently or raw material viscosity is unstable
Diagnosis: Check the status of the raw material liquid level sensor and supply pipeline
Solution: Adjust the output of the supply pump or clear blocked pipelines
Temperature Control Instability
Phenomenon: Large temperature fluctuations lead to inconsistent facial mask quality
Diagnosis: Check PID parameter settings and heater working status
Solution: Retune PID parameters or repair the heating system
Facial Mask Forming Abnormality
Phenomenon: Uneven forming thickness or bubbles
Diagnosis: Check forming pressure and speed parameters
Solution: Adjust pressure sensor calibration values or optimize forming process parameters
3.2. Use of Diagnostic Tools
Utilize the TIA Portal online diagnostic function to monitor key data in real-time:
Use variable monitoring tables to observe process parameters
Analyze temperature curve fluctuations through trend graphs
Utilize program status diagnostic function block execution status
Check historical alarms through the system diagnostic buffer
4. Data Management and Storage
4.1. Parameter Configuration Table
Facial mask production process parameters are stored in the DB1 data block:
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DATA_BLOCK "Process_Parameters_DB"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
NON_RETAIN
VAR
Mask_Type : Int; // Current type of facial mask being produced
Temperature_Setpoint : Real := 55.0; // Process temperature setting (℃)
Pressure_Setpoint : Real := 2.5; // Forming pressure setting (bar)
Flow_Setpoint : Real := 75.0; // Raw material flow rate setting (ml/min)
Forming_Time : Time := T#3S500MS; // Facial mask forming time
Cooling_Time : Time := T#2S; // Cooling time after forming
Cutting_Speed : Real := 25.0; // Cutting speed setting (m/min)
Conveying_Speed : Real := 18.0; // Conveyor speed setting (m/min)
END_VAR4.2. Operating Data Recording
The system automatically records key production data, including:
Statistics of production quantity per batch
Device operating time and downtime
Energy consumption monitoring data
Records of deviations in key quality parameters
These data are stored in the DB2 data block and can be viewed or exported through HMI:
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DATA_BLOCK "Operating_Status_DB"
{ S7_Optimized_Access := 'TRUE' }
VERSION : 0.1
VAR
Current_Production_Quantity : DInt; // Current batch produced quantity
Target_Production_Quantity : DInt; // Current batch target quantity
Device_Start_Time : DTL; // Start time of this run
Cumulative_Operating_Time : Time; // Cumulative device operating time
Energy_Consumption_Record : Array[0..23] of Real; // 24-hour energy consumption record
Temperature_Record : Array[0..99] of Real; // Cycle temperature record
Pressure_Record : Array[0..99] of Real; // Cycle pressure record
Production_Record : Array[0..6] of DInt; // Weekly production record
END_VAR5. HMI Interface Design
5.1. Interface Layout Description
The HMI interface of the facial mask production equipment adopts a zoned design, mainly including the following screens:
Main Screen: Displays device operating status, current production information, and key parameters
Parameter Settings: Process parameter configuration and adjustment interface
Production Monitoring: Real-time data trend graphs and production statistics
Alarm Page: Current alarms and historical alarm queries
User Management: Operation permission settings and user login
5.2. Operating Monitoring Description
The operating monitoring screen focuses on displaying the following information:
Dynamic graphics of the status of each workstation
Real-time curves of temperature and pressure
Production counter and efficiency indicators
Device operating status indicator lights
Status of key components
The system uses different colors to indicate device status: Green indicates normal operation, Yellow indicates standby state, Red indicates fault state, Gray indicates shutdown state.
6. Conclusion
Siemens PLC can achieve precise process control and efficient fault diagnosis in facial mask production equipment, and a reasonable program design is the guarantee for stable production. We welcome you to share your application experiences!
