Successful Case Studies of Siemens PLC in Industrial Automation: Providing Referable Automation Solutions for the Industry

Introduction: How PLCs Become the “All-Rounders” in Industrial Control?

For professionals in the field of industrial automation, PLCs (Programmable Logic Controllers) are like the “brains” of the production line, capable of controlling motors, managing conveyor belts, and implementing complex motion control. A small PLC can easily handle these tasks. Siemens’ S7-200 SMART PLC has become a star product in recent years, inheriting Siemens’ high stability while being optimized for domestic market needs, making it the preferred choice for economical automation solutions.

Today, we will discuss the application results of the S7-200 SMART in industrial automation through several practical case studies and analyze the key technical points that solve problems. Whether you are a novice engineer or an experienced veteran, this article will provide you with inspiration and practical advice!

Case Study 1: “Precise Positioning” Control of Labeling Machines

Application Background

Labeling machines are very common in the packaging industry, requiring accurate labeling during high-speed operation. The customer’s requirement is 220 bottles per minute, with the ability to stop precisely based on color mark signals. In such a high-speed environment, mechanical inertia often leads to positioning deviations and frequent label misalignments.

Solution

The S7-200 SMART PLC achieves efficient control of the labeling machine through PLS (Position Triggered Output) instructions, combined with precise capture of high-speed input signals.

Key Technical Points

1. 1. High-Speed Pulse Input/Output (HSC/PTO)

* The color mark sensor signal from the labeling machine is input through the PLC's high-speed input interface.
* The PLC calculates the position of the bottles based on the received signals and triggers the labeling action in real-time.

1. 2. Multi-Stage Speed Application of PLS Instructions

* During the labeling process, the PLS instruction divides the labeling action into multiple speed segments. It decelerates as it approaches the target position to ensure more precise stopping.

1. 3. Deviation Correction Algorithm

* Using the PLC's built-in logic operation functions, the next trigger point is adjusted in real-time based on the deviation between the actual labeling position and the target position.

Example Ladder Diagram

|——[High-Speed Input]——[Counter]——[PLS Instruction]——[High-Speed Output]
|——[Deviation Correction Logic]——[Update Counter Value]

Actual Wiring

• • Sensor signals are connected to the PLC’s high-speed input terminal (e.g., I0.0).
• • Stepper motor control signals are driven through the high-speed output terminal (e.g., Q0.0).

Notes

• • Sensitivity of Color Mark Sensors: Ensure that the sensor can accurately capture target signals during high-speed operation.
• • Mechanical Inertia Issues: If the device has significant inertia, consider adding buffering devices or deceleration motors to optimize.

Case Study 2: 2D Material Handling with Linear Interpolation

Application Background

In an automated factory, the user needs to transport materials from point A to point B using a handling robot, with the ability to flexibly respond to different transport paths. The system is required to be efficient and quickly adapt to new path requirements.

Solution

The linear interpolation function of the S7-200 SMART PLC easily solves this problem, especially with the newly added Path Planning Function in version V2.7, which further simplifies the setting of complex paths.

Key Technical Points

1. 1. 2D Linear Interpolation Motion Control

* Continuous interpolation paths are generated through axis grouping functions (e.g., X-axis and Y-axis).
* The user only needs to provide the coordinates of the target point, and the PLC will automatically complete the path calculation and execution.

1. 2. Path Planning Function

* Multiple target points can be configured in a table format within the PLC program, and a subroutine can be called to complete the entire transport path.

Example Ladder Diagram

|——[Read Path Coordinates]——[Linear Interpolation Instruction]——[Motion Control Output]
|——[Target Point Arrival Judgment]——[Update Target Point]

Practical Application Case: Transporting from Point A to Point B

1. 1. Target Point Setting* Point A: (X1, Y1), Point B: (X2, Y2).* Configure the coordinate point table in the PLC program.
2. 2. Code Example

IF Current Coordinate ≠ Target Coordinate THEN
    Execute Linear Interpolation(X Target, Y Target, Speed);
END_IF;

1. 3. Hardware Setup* Two stepper motors control the X-axis and Y-axis, driven through the PLC’s high-speed pulse interface.

Notes

• • The unit of coordinate points and the proportional relationship with actual devices need to be calibrated.
• • For complex paths, testing can be conducted using simulation software (e.g., NX MCD).

Case Study 3: Automation Control of Wastewater Treatment Systems

Application Background

With increasing environmental protection requirements, wastewater treatment systems have become an important part of industrial sites. In a certain wastewater treatment project, the user needs to achieve automation control of bag filter equipment and reverse osmosis water treatment systems.

Solution

The S7-200 SMART PLC, in conjunction with HMI screens, achieves full-process control from equipment start/stop, process monitoring to alarm handling.

Key Technical Points

1. 1. Multi-Device Interlocking Control

* The PLC controls the start and stop of multiple devices through relay outputs.
* Data registers record device status for subsequent monitoring and analysis.

1. 2. HMI Interaction Design

* The HMI interface is designed to be intuitive, allowing users to view device operating status and adjust parameters in real-time via a touchscreen.

1. 3. Alarm Function

* When certain critical points (e.g., high water level, filter clogging) trigger alarm signals, the PLC logs the event and displays it on the HMI.

Common Issues

• • Signal Interference Issues: Due to significant electromagnetic interference in industrial sites, it is recommended to use shielded connections for sensors and PLCs.
• • Device Fault Diagnosis: Use the PLC’s diagnostic functions to promptly identify fault points.

Conclusion: Learning Efficient PLC Applications from Case Studies

The above case studies demonstrate the wide application of the S7-200 SMART PLC in industrial automation. Whether it is motion control, path planning, or multi-device interlocking, the S7-200 SMART can help engineers easily tackle various challenges with its powerful functions and flexible configurations.

Practical Suggestions

1. 1. Start with Simple Cases: Beginners can start with basic I/O control and gradually master advanced instructions (e.g., PLS, interpolation instructions).
2. 2. Make Full Use of Simulation Tools: Tools like Siemens’ TIA Portal software can significantly improve debugging efficiency.
3. 3. Focus on Hardware Selection: Choose appropriate CPU modules and expansion modules based on actual needs, rather than blindly pursuing high configurations.
4. 4. Learn from Cases and Be Bold in Practice: Refer to application cases to understand the underlying technical ideas and apply them flexibly in actual projects.

The world of industrial automation is full of infinite possibilities, and PLCs are the gateway to this world. I hope this article helps you progress faster and further on your journey of learning and applying PLCs!