Design of a fast color change control system for automotive coating.

This article Dai Jianming, Cao Cheng, etc.
Source: 2020 Paint Industry No. 8
Team Profile
Dai Jianmin: Associate Professor, Senior Engineer, mainly engaged in electrical control systems and other research
Cao Cheng: Fujian Engineering College is a master's student, mainly engaged in industrial automation control systems, etc. Research
Yu Guixuan: Fujian Rui Agile Shun Industrial Intelligent Equipment Co., Ltd. senior electrical engineer
At present, the automotive factory paint room usually uses the traditional "circular line system", a tank needs at least 200 to 1000 kg paint, because of its production is not much, may not have production demand for several months. Paint long-term circulation in the pipe and use very little, the composition of the slurry, metal powder due to the pipe wall and valve shearing force and constant precipitation led to chroma problems, resulting in the end of paint. And these small colors of paint unit price is usually common large quantities of color paint 2 times or

. At the same time, the system is no longer able to meet the needs of a variety of personalized colors, quantities and rapid color change. Color change cleaning difficulties, resulting in a large amount of waste of cleaning solvents, seriously affecting the workshop production beats, making production efficiency inefficient. In order to ensure the quality of color at the same time, to minimize the waste of material process, is the coating production and manufacturing field has been the same goal.
in view of the problems existing in the production process of the above-mentioned automobile coating, a fast color change control system with high degree of automation, high stability, fast color change speed and strong cleaning ability is designed. The system is stable and reliable, high production efficiency, convenient and fast color change, to meet the production requirements of the enterprise workshop.
1 Process Introduction
Rapid color change control process mainly includes paint filling, recycling, cleaning 3 stages, in which the cleaning process ideas combined with the filling process and recycling process. The three-stage process analysis is as follows.
1.1 Paint Filling
When filling paint is required, the operator adds the processed stirred paint to the paint bucket and the operation control button fills it. The paint is sent from the paint bucket to multiple distribution stations on the paint production line by a closed polyethylene (TPC) soft supervisor through a double diaphragm pump, and the distribution station branch is filled after the supervisor has filled it. The distribution station station station branch filled with spray needs to remain in the pending spray state after filling. The fill process flow diagram is shown in Figure 1.
Figure 1 Filling Process Flow Chart
1.2 Paint Recovery
After the spraying work is completed, the TPC supervisor paint is recycled into the paint bucket through compressed air from the bead receiving module, due to the shorter distribution station branch lines, the paint is less not recycled, and the residual paint in the branch pipe is discharged directly into the waste bucket by compressed air. The recycling process is shown in Figure 2.
2 Recycling process flowchart
1.3 Cleaning
cleaning the entire equipment, TPC supervisor and distribution station branch after recycling. According to the above-mentioned process, the cleaning solvent is filled with the entire pipe, the cleaning solvent is pushed to the waste bucket by compressed air, pushed by the beading, and the cleaning is selected according to the nature of the paint (e.g. viscosity, etc.) to meet the requirements of cleaning clean colorless. The cleaning process is a process idea that combines the filling and recycling processes. After cleaning is complete, replace the other color paint for filling and color change spraying. The cleaning process is shown in Figure 3.
Figure 3 Cleaning Process Flow Chart
2 Fast Color Change Control System Hardware Design and Working Principles
The Rapid Color Change Control System consists mainly of electrical control module, base station module (including dual diaphragm pump, filter module, combination valve module, beading emission module), distribution station module.
electrical control hardware design is mainly integrated electronic control cabinet, through the programmable logic controller (PLC) control valve island group solenoid valve opening and closing state and then control the opening and closing of pneumatic valves. According to the actual engineering needs, comprehensive current market product cost-effective, electronic control cabinet mainly choose Siemens S7-1500 CPU1516-3PN/DPPLC as the core controller, TP1200 smart panel HMI as a human-computer interface; According to the equipment structure characteristics and control requirements, the hardware design structure of the electrical control module is shown in Figure 4.
Figure 4 Electrical control module hardware design structure diagram
According to the control system filling, recycling, cleaning function requirements, combined with the characteristics of the equipment structure, the system has 10 inputs, 28 bits of output, a total of 38 points, of which the input and output I/O assigned address as shown in Table 1, Table 2.
Table 1 I/O Distribution Table (Input)
Table 2 I/O Distribution Table (Output)
3 Fast Color Change Control System Software Design
3.1PLC Master Program Design
Write the main program of PLC using TIAV15 software platform, programming PC through Ethernet and PLC for program load and debugging. TIAV15 is an automated programming tool introduced by Siemens, which can effectively configure configuration hardware, perform automated tasks, and increase productivity.
3.1.1 Fill control step
. The filling process in the PLC automatic control program process is shown in Figure 5.
5 Fill Control Program FlowChart
(1) press the fill button for position 1.
(2) Open pump high-pressure valve, spray feed valve, waste valve corresponding to the output address is Q1.4, Q2.0, Q2.2 (can see Table 1, Table 2, the same below), place 1 (specified valve open the corresponding position 1; close the corresponding position 0. the same between). Delay 5s to fill the mechanical pipe with paint through the high-pressure pump.
(3) to close the waste valve, open the right main feeding valve, the right emission valve. The paint pushes the beads to fill the entire right supervisor and performs the next step after meeting the conditions of no beads in the right transmitter detection position (i.e. I0.1 bit is 0) and the right receiving station detection bit has beads (i.e. I0.3 bits are 1). If the conditions are not met, always wait for the paint to fill, set the delay time according to the length of the pipe, after the time alarm prompts the operator to detect whether the drop position is Caton.
(4) close the right supervisor feeding valve, the right transmitter valve, open the left supervisor feeding valve, the left transmitter valve. The paint pushes the bead to fill the entire left supervisor, after meeting the condition that the left transmitter detection bit has no beads (i.e. I0.0 bit is 0) and the left receiving station detection bit has the bead (i.e. I0.2 bit is 1) condition, the next step is performed. If the conditions are not met, always wait for the paint to fill, set the delay time according to the length of the pipe, after the time alarm prompts the operator to detect whether the drop position is Caton.
(5) Open the right supervisor feed valve, right transmitter valve, left supervisor feed valve, left feed valve and the distribution station feed valve for each distribution station station, filling the distribution station branch paint.
(6) keep the right supervisor feeding valve, right transmitter valve, left supervisor feed valve, left feed valve, to ensure the continuous supply of paint, waiting for car spraying operations. The fill is complete.
3.1.2 Recovery Control Step
. The recycling process in the PLC automatic control program process is shown in Figure 6.
6 Recycling control program flowchart
(1) the car is sprayed, press the recycling button.
(2) open the flushing air valve, pump low pressure valve, feed valve and return valve, delay 5s. The paint in the mechanical pipe is recycled into the paint bucket, driven by compressed air.
(3) open the return valve, the left supervisor feed valve, the left emission valve and the left receiving air valve. The left bead is reclaimed by high-pressure air in the left bead receiving station module. After meeting the condition that the left transmitter detection bit has a bead (i.e. I0.0 bit is 1) and the left receiving station detection bit has no bead (i.e. I0.2 bit is 0), the next step is performed.
(4) closes the left supervisor feed valve, the left transmitter valve and the left receiving air valve, and opens the right supervisor feed valve, the right transmitter valve, and the right receiving air valve. The right-hand supervisor paint is reclaimed by pushing the bead through the high-pressure air in the right bead receiving station module. After meeting the condition that the right transmitter detection bit has a bead (i.e. I0.1 bit is 1) and the right receiving station detection bit has no bead (i.e. I0.3 bit is 0), the next step is performed.
(5) open the waste valve for relief. The recycling is complete.
3.1.3 Cleaning control step
. The cleaning process in the PLC automatic control procedure is shown in Figure 7.
7 Cleaning control procedure flowchart
(1) paint recovery is complete, press the cleaning button.
(2) open the flushing solvent valve, pump high-pressure valve and spray feed valve, delay 5s. Fill the mechanical pipe with cleaning solvents.
(3) Open the right supervisor feed valve, right emission valve, cleaning solvent push bead filling the entire right supervisor, in the right transmitter detection position without beads (i.e. I0.1 bit 0) and the right receiving station detection bit has beading (i.e. I0.3 bit is 1) conditions, the next step is carried out.
(4) close the right supervisor feeding valve, the right transmitter valve, open the left supervisor feeding valve, the left transmitter valve. Cleaning solvent push bead filling the entire left supervisor, after meeting the left transmitter detection bit no bead (i.e. I0.0 bit 0) and the left receiving station detection bit has beading (i.e. I0.2 bit is 1) conditions, the next step is performed.
(5) keep the right supervisor feeding valve, right transmitter valve, left supervisor feed valve, left feed valve, to ensure the continuous delivery of cleaning solvents.
(6) to open each station distribution station feeding valve, each station distribution station waste liquid valve, the use of cleaning solvent to push the residual paint of the branch into the waste bucket. Clean the branch by the way.
(7) after cleaning the branch, close all station distribution station feed valves. Open the waste valve, the left supervisor feed valve, the left emission valve and the left receiving air valve. Push the left supervisor cleaning solvent into the waste bin by pushing the bead through the high pressure air in the left bead receiving station module. After meeting the condition that the left transmitter detection bit has a bead (i.e. I0.0 bit is 1) and the left receiving station detection bit has no bead (i.e. I0.2 bit is 0), the next step is performed.
(8) close the left supervisor feed valve, the left emission valve and the left receiving air valve. Open the right supervisor feeding valve, the right transmitter valve, and the right receiving air valve. Push the right supervisor cleaning solvent into the waste bin by pushing the bead through the high pressure air in the right bead receiving station module. After meeting the condition that the right transmitter detection bit has a bead (i.e. I0.1 bit is 1) and the right receiving station detection bit has no bead (i.e. I0.3 bit is 0), the next step is performed.
(9) detects whether the pipe is clean or satisfies the number of cleanings, and returns step 2 if the number of cleanings is not reached. After the number of cleanings has been satisfied, the cleaning is complete.
3.2 human-computer interface design
-man interface is the key link between operators and production equipment, and its operating interface is programmatically designed based on the TIAV15 platform for monitoring and control of the entire system. The operating interface of the touch screen in the design system is mainly composed of the base station operation interface, the distribution station operation interface and the alarm interface.
3.2.1 Base Station Operation Interface
Base Station Operating Interface is based on the actual pipeline wiring of the precise simulation design, through the base station operation interface can be real-time observation of the oil level in the paint bucket and the opening and closing status of each valve; Transmission station or receiving station, the interface gray rectangle turned green means that magnetic induction sensor sensed the beads in the table, the interface valve in the closed state of gray, the on state is green, the corresponding pipeline line also changed from black to green gives people an intuitive, simple, clear feeling.
in the lower right corner of the interface can be filled, recycled, cleaned, emergency stop, reset and other button operations, in the execution instruction bar according to the current running status display operation purposes, easy for the operator's understanding. The execution time represents the timing of the entire system's operation. If the gray rectangle triggered by the loop turns green, the loop is triggered, and the control process is completed. At the same time, the interface can be observed on the left and right sides of the bead run count value and the bead in the seat position. The simulation diagram of the base station operating interface is shown in Figure 8.
Figure 8 Base Station Operation Interface Simulation Figure
3.2.2 Distribution Station Operation Interface
The distribution station is closely connected to the robot, and the paint of the main channel is filled into the branch connected to the robot color changer valve by the opening of the spray feed valve. The opening and closing status of the valve, the execution instructions, the current state, the paint color sprayed, and the execution time can be seen on the distribution station operation interface. The distribution station operation interface simulation diagram is shown in Figure 9.
9 Distribution Station Operating Interface Simulation
3.2.3 Alarm Interface
which allows you to view current errors, alarm information, including error numbers, time dates, and text interpretations. The error message file or warning information file allows you to view historical error information and alarm information. The alarm interface is shown in Figure 10.
10 Alarm Interface Simulation Figure
4 Practical Application
This study writes the program described above to the PLC and controls the filling, recycling and cleaning process through the HMI touch screen. According to statistics, an automobile factory enterprise centralized paint system single paint change volume of about 600L; The control system is applied to the paint room of the automobile factory, and the length of the pipe is about 80m for test testing, the test results are shown in Table 3.
3 Test Data
From Table 3 data, it can be found that the rapid color change control system can complete the color change within 45 to 60min, greatly shorten the color change cycle, speed up the pace of production and improve efficiency. According to the paint recovery rate and cleaning solvent savings can be calculated according to the type (1), type (2).
that the system can recycle about 85.7% of the paint and can be used again. The more traditional circulating pipe system saves 82.8% of the cleaning solvent, saving enterprises a lot of economic expenses.
5 Conclusion
Fast color change control system with S7-1500PLC as the core controller, HMI touch screen as a human-computer interface, the operation of the entire control system can be real-time detection and debugging, to ensure that the system operation is accurate and reliable. The control system has been put into actual enterprise production, compared to the traditional cycle pipeline type.