Sea is the application of PLC in electrostatic spraying line
**Foreword:**
With the rapid advancement of intelligent manufacturing, industrial robots are becoming increasingly popular. Spraying automation is accelerating the transformation of traditional painting industries by offering high-quality coating and a strong return on investment.
Currently, most manufacturing industries in China still rely on manual spraying methods. To meet customer demands for film thickness and surface quality, additional grinding and re-spraying are often required, leading to labor-intensive work, low efficiency, and health risks for workers due to long-term exposure to paint fumes. Challenges such as difficulty in recruitment, rising wages, and environmental concerns are now significant issues in the painting industry. To address these challenges, the automation of the painting line must be considered to improve efficiency, product quality, and reduce operating costs.
**Keywords:** Haiwell PLC, electrostatic spraying automation, high-speed pulse output, inverter, 485 communication
**1. Control Requirements**
Traditional spraying involves directly applying paint onto glass bottles using a spray gun, followed by drying and removing excess paint through water. This method not only wastes paint but also causes serious environmental pollution.
Now, the system requires atomized paint to be sprayed at high speed onto the outer surface of the glass bottle using a rotating stainless steel disc that moves up and down rapidly. The speed of the glass bottle's forward movement and its rotation are controlled by frequency inverters.
**2. Main Hardware Configuration**
**PLC Selection: T24S0T**
The controller uses the T24S0T model from Haiwell. It has an external 24V DC power supply, 16 digital inputs (DI), and 8 relay outputs (DO). It comes with two communication ports (RS232 + RS485) and can be expanded to support up to five communication ports. It also includes two 200kHz high-speed pulse inputs and two 200kHz high-speed pulse outputs. With a maximum expansion of seven modules, this system is ideal for controlling multiple inverters to adjust the speed of the glass bottles, preventing over-spraying or under-spraying.
The T24S0T supports both master and slave communication modes and can connect to various third-party devices such as inverters, instruments, and barcode readers. Its flexibility makes it suitable for integration into complex automation systems.
The motor's rotation drives the nozzle up and down, allowing for more accurate application of paint on the glass bottle. The T24S0T supports several output modes including single pulse, pulse/direction, forward/reverse, A/B phase pulse, and synchronous pulse output. This wide range of options ensures compatibility with different motor types.
**3. Part of the Program**
Haiwell’s PLC communication program is straightforward. No matter which protocol you use, one command is sufficient to handle complex communication tasks. In this example, the inverter operates at a baud rate of 9600 with data format E,7,1. Below is an example of a program used to read the inverter frequency.
In this case, the servo uses the pulse plus direction output mode. Therefore, the PLC is configured to use pulse/direction output. The nozzle moves up and down via the PLSY high-speed pulse instruction. When the pulse count is positive, the motor rotates forward, moving the nozzle downward; when negative, it rotates backward, lifting the nozzle upward.
**4. Conclusion**
Haiwell’s PLCs feature multiple communication ports that can be programmed and networked. They can function as either master or slave units and support various networking configurations such as 1:N, N:1, and N:N. By using the Haiwell PLC, multiple inverters can be easily connected to control the movement of the glass bottles.
Haiwell’s PLC supports up to 8 channels of 200kHz dual-phase high-speed pulse output, with features like acceleration/deceleration, multi-segment envelope, and unique synchronization pulse output. These functions enable precise control and synchronization. Using the high-speed pulse output of the Haiwell PLC, the motor can be controlled to drive the nozzle, resulting in more efficient and faster electrostatic spraying.
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