Grasp the key factors to solve the debugging problems of automobile paint shop

This workshop adopts the mainstream phosphorus-free + B1B2 (free of intermediate coating) process, as well as environmental protection facilities such as dry carton paint mist capture, complete purification and incineration of spray paint exhaust gas, and online monitoring.

1 Bottleneck of internal spray window

The earliest problem is that the paint spraying robot frequently alarms, and the lack of paint is serious

In the early days, some economical internal painting lines used a seven-axis robot + accompanying layout, but now they mostly adopt a stop-and-go mode

Figure 1 The window restriction of six-axis robot + accompanying layout

From the above analysis, it can be seen that expanding the internal spray window time of the colored paint is the primary task.

Based on the previous experience and lessons from the transformation of the internal spray robot and the debugging of this line, and the overall development of the industry, it is recommended that the economical automobile coating internal spray adopts a seven-axis robot + stop-and-go one-stop layout mode, which will improve the efficiency of automatic spraying equipment and reduce production.

2 Pearlescent white difference

After debugging, it was found that there was a color difference on the door side of the pearl white body, which could not be mass-produced

The inner surface of the colored paint in this workshop is electrostatic sprayed, and there will be superimposed fat edges surrounded by electrostatic spray on the inner and outer surfaces of the door

After communicating with the supplier, a B1 coating with the same color as B2 was developed.

3 Electrophoresis adhesion failure

This workshop adopts phosphorus-free pretreatment technology, and the daily feeding and parameter monitoring business is contracted to the pretreatment agent supplier.

The pre-degreasing of this line is spraying, and the degreasing is dipping.

Non-phosphorus is generally an alkaline degreaser substance, corrosion inhibitors and the chelating agent A, agent B is a surfactant

In the non-phosphating technology, because the thin film treatment layer cannot be like phosphating, it will form a relatively strong dense bonding layer to compensate for small defects.

Microscopic observation and testing of the peeled electrophoretic layer sample revealed that its bonding surface with the car body contained a non-phosphorus film layer and zinc
.
In addition, the accident medicine was verified in the laboratory to pass the adhesion, but the adhesion of the production line was very poor
.
The reason for this problem is that the on-site working conditions of the degreasing section are different from the current conventional experimental conditions.
The hot and humid alkaline steam working atmosphere at the site will cause the zinc oxide to rapidly form on the surface of the galvanized layer if the corrosion inhibition effect is insufficient And the loose layer of zinc hydroxide (the volume of the mixture increases beyond the limit and collapses), resulting in the subsequent failure of the adhesion of the electrophoretic coating
.
The main laboratory and on-site cross-comparison and solution process are shown in Table 1
.

Table 1 Cross-checking process of electrophoretic adhesion

The age of phosphating paid little attention to the difference in degreasing ingredients and on-site working conditions.
For the development of the formulation of non-phosphorus-free mixed boards, special attention should be paid to the alkali washing and corrosion inhibition balance of various boards under the conditions of on-site use of degreasing agents
.
Aluminum ions will react with some corrosion inhibitors, and the alkaline corrosion of electro-galvanized, hot-dip galvanized, zinc-iron alloy, cold-rolled sheet, etc.
is different
.
The bus pre-treatment line is easy to make the body dry and return to rust, and the car pre-treatment is a closed channel with humidity and heat
.
For the development of degreasing materials for cars without phosphating agents, it is necessary to establish a damp and heat model that is closer to the use of the site, or to develop supporting degreasing materials at room temperature.
The design of the degreasing section of the phosphorus-free car line can also study how to reduce the humid and hot air atmosphere
.

4 Electrophoresis "return rust"

During the production, it was found that the red-brown "returning" phenomenon of the door near the hinge after electrophoresis (as shown in Figure 2), the film formation of the defective part was not continuous, and the serious position was exposed without electrophoretic paint.
Therefore, the produced car body was immediately replaced And stop the line for rectification
.

Figure 2 Symptoms of electrophoresis "return to rust" of door hinge attachments

After testing, it was found that this rust-returning phenomenon occurs when the resistance of the door hinge exceeds 3000Ω.
The greater the resistance, the more serious the rust-returning or even the bottoming
.
Use iron wire to connect the door inner panel and the car body to experiment on the production line, and there will be no back rust phenomenon
.
This happens because if the hinge has poor conductivity (the principle is shown in Figure 3), during the electrophoresis process, shaking the door will instantly cut off the electricity and become the positive electrode, and O2 will be precipitated, causing pinholes
.
This situation used to be between the rear of the first segment and the front of the second segment in the segment voltage
.

Figure 3 Principle of interference caused by poor power supply

Hinges with poor electrical conductivity will cause different results in the use of different production lines and coating systems.
Most production lines may not have rust back due to differences in body assembly and transportation and movement in the tank.
However, after this problem occurs, let the hinge Conduction is the best and most thorough solution
.

5 The inner surface of the right rear door sags

After entering the winter, sagging at the junction of the inner surface and the outer surface appeared in the metal paint construction, especially on the top of the right rear door frame
.
Sagging is a common defect in painting.
It is usually the adjustment of robots and paint formulations, but on-site adjustments cannot effectively eliminate this problem
.

B1B2，
。，，，（，4）
。，18℃，22℃，
。30℃，，
。

4

，
。，，，
。，
。，，，
。

6

There are many cases of solving debugging problems by eliminating the main factors in this workshop.
Due to space limitations, some key solutions are directly listed for reference: Use Klud 162 high boiling point solvent + ultrasonic to solve the problem of rotating cup cleaning and eliminate poor atomization Caused by edge bubbles, and local lack of paint on the inner surface due to poor atomization of the rotary cup; the addition of temperature control equipment to the gluing equipment solves the construction problem caused by the large temperature difference between morning and night in the summer glue room; use point contact instead of surface contact to solve The surface paint magnetic tooling is dirty and sag; the pipeline direction of the internal spray robot is reconstrained, the robot clothes are changed from split to one-piece, and the robot "sleeve" is added to solve the serious dirty; by adding the internal sprayer and opening the door The compressed air blowing of the device can solve the water-based wet paint mist conductive alarm on the atomizer and the dripping paint of the door opener
.
By improving the intelligent transfer and mixing function, the long-term cyclic shearing color difference of small-color paints is optimized
.

In addition, according to local conditions, the ability of the rich equipment in the workshop has also been improved: the appearance of 8 robots on the outer surface of the varnish was changed from one-pass spraying to two-pass spraying; the mode of 5+5 of 10 robots on the outer surface of the colored paint was changed to 4+ 4.
While solving the interference of paint mist, it can achieve the same-beat downgrade function, and reduce energy consumption and consumption; the quality management APP has been developed using the handheld device inspection system, which can realize the quality information input and completion of the workshop quality inspection personnel through the program click.
Aggregate and archive
.

7 Conclusion

There were many problems in the early stage of the project debugging, which made it impossible to put into production.
By solving the key factors that restrict each problem, instead of comprehensively analyzing and investigating to negotiate every possible influencing factor, quickly eliminating the problem is the ultimate goal of this workshop to achieve high-quality mass production.
Key
.