[YesAuto Factory Secret] Cadillac, a brand that flashes the halo of the US president, its models have always been loved by American political and business elites. Today, the brand's flagship car, the Cadillac CT6, is made in China, and its production plant has GM's most advanced manufacturing technology and equipment. How does this new factory create a high-quality Cadillac CT6? Please follow us to the factory to find out.
Cadillac’s Golden Bridge plant laid the foundation stone in June 2013 and was completed and put into production on January 21, 2016. The factory has a total investment of 8 billion yuan and covers an area of 477,000 square meters. There are three workshops in the factory: welding workshop, painting workshop and general assembly workshop. The factory is currently in the stage of capacity ramp-up, and it is expected to achieve the planned annual production capacity of 160,000 vehicles in 2017.
Cadillac CT6's body outer cover parts are all aluminum alloy stamping parts, which are produced by the stamping workshop of SAIC-GM Jinqiao North Plant using a 5-sequence stamping process (the steel plate uses a 4-sequence stamping process). Since the stamping performance of aluminum alloy plates is not as good as that of steel plates, more stamping procedures must be used to achieve the modeling requirements of aluminum alloy outer covers.
The inner frame of the Cadillac CT6 uses different materials. High-strength steel is used in parts such as A and B-pillar frameworks, door anti-collision beams, and underbody longitudinal beams to enhance the structural strength of the vehicle body and provide better protection for the occupants in the passenger compartment. The front anti-collision beams, front longitudinal beams, front wheel arches, and underbody cross beams are all made of aluminum alloy to achieve weight reduction.
The car body is made of steel only, and the connection between the parts can be made by various welding processes. The steel-aluminum hybrid body cannot be assembled by welding. This is because the physical properties of steel and aluminum are quite different. During the welding process, the joints of aluminum and steel will generate a lot of thermal stress, which is prone to produce brittle structures between metals, increase the tendency of cracks, and fail to form welds or cause post-weld failure. .
The welding workshop we visited this time is different from the welding workshops of most of the factories we have visited before, adding equipment for aluminum welding and steel-aluminum connection. The welding workshop will use aluminum laser welding and aluminum resistance spot welding to realize the welding between aluminum plate and aluminum plate; use self-tapping screw connection and self-piercing riveting to realize the connection between steel plate and aluminum plate.
The connection of the aluminum alloy roof and the body of the Cadillac CT6 and the connection of the trunk cover assembly are the above-mentioned aluminum laser welding technology. A laser is used to melt the brazing material made of aluminum to realize the connection between the aluminum plates . Among them, the aluminum laser welding weld of the trunk cover can be subjected to subsequent painting operations without grinding and other treatments, which shows the smoothness of the weld surface. The aluminum alloy weld between the roof and the car body does not need to be polished, just apply a layer of glue and scrape it before painting to ensure the quality of the subsequent paint finish.
The aluminum resistance spot welding in this workshop adopts a circular texture at the end of the metal welding head, which is a general patented technology, which can avoid the influence of the inherent oxide film on the surface of the aluminum plate on the welding quality to the greatest extent. We see the texture on the aluminum resistance spot welding joints on the car body is the “imprint” left by the metal welding head after the aluminum is melted.
The workshop will use the self-tapping screw connection process to connect the aluminum plate and steel plate on the car body. This process presses the screw on the surface of the workpiece and rotates the screw at a high speed, forming a thread by self-tapping in the double (multi-layer) sheet material, thereby quickly realizing the threaded screw connection between the sheets. Since there is no need to use a “clamp” welding gun to clamp the two sides of the panel to realize the connection of the panels like the spot welding process, the connection between the panels in the passenger compartment that could not be realized by automatic spot welding by robots is now self-piercing The riveting technology can be automatically completed by robots, which improves production efficiency .
Self- piercing riveting uses high-strength tubular rivets to penetrate the upper plate under high pressure. At the same time, the end of the rivet penetrates into the lower plate and expands under the action of pressure and the lower die to form a self-locking, thereby realizing the gap between different types of plates (aluminum, steel, plastic) Connection. This riveting process has been widely used in aircraft manufacturing (such as airplanes and rockets). Its connection strength is 120% of the strength of ordinary resistance spot welding, and it has low energy consumption, no smoke, no heat, and high production efficiency .
There are 386 robots in the welding workshop, and all welding/riveting/screw connection work is automatically completed by the robots. Due to the high degree of mechanization of the workshop, there are only more than 30 workers in the entire welding workshop. They are mainly responsible for the installation of four doors and two covers, the material of the body splicing line and the maintenance of equipment. The welding workshop supports up to 7 types of mixed-line production, and is currently GM's most flexible welding workshop.
This new factory has done a lot of innovative designs in the paint shop. From the appearance of the entire paint shop, you can’t find the tall chimney used to treat the spraying exhaust gas. That is the characteristic of the paint shop in the automobile factory. One, this is also the only paint shop in China's auto industry that does not have a high chimney. It doesn't look very eye-catching, but it is a qualitative leap in waste gas treatment.
In addition to the mentioned innovations in exhaust gas treatment, in the coating technology, from the pre-treatment to the final painting link has made a lot of breakthroughs. In addition, the material of the damping pad that we have paid attention to is also available on the Cadillac CT6. New attempt. Before entering the paint shop, according to the usual practice, first clean the whole body.
The body-in-white passes through the high-altitude passage from the welding workshop to the paint shop. Simply put, the body-in-white will complete two tasks here, one is anti-corrosion and the other is coloring. The anti-corrosion work is completed in a fully enclosed pre-treatment line, which is composed of several treatment tanks.
The new factory has made innovations in the damping pad. The traditional damping pad is made of asphalt, which may become a source of peculiar smell in the car. Spraying liquid water-based paint to the corresponding position can achieve environmental protection, sound insulation, The role of vibration reduction. From the perspective of the workshop, this method can be flexibly adjusted for different models in the future, and it also saves the trouble of material stacking.
The glue application process is relatively traditional, and manual operation is still the main method. Combined with the flow setting of the glue gun, the sealant is evenly applied to the weld. After that, the operator holding the squeegee will smooth the sealant and complete the trimming. .
The paint process has been improved to meet users' expectations of the visual perception of the appearance of the Cadillac CT6 model, by changing the traditional one-color paint to two-pass spraying. The red color you see is realized on the basis of spraying colored varnish. The colored varnish will highlight the contrast of light and dark of the entire paint surface, making the whole more brighter.
Cadillac's Jinqiao factory assembly workshop has three most intuitive impressions: quiet, efficient, and good air quality. Adhering to the concept of high flexibility, lean production, green environmental protection and people-oriented construction, the plant is currently one of GM's highest-standard vehicle production plants in the world. In the workshop, we can see advanced equipment such as the automatic logistics transportation system, the exhaust gas collection system with flaps, the automatic glue application robot, the auxiliary installation manipulator, and the silent transportation production line.
In order to ensure the clean air in the assembly workshop, a large number of ventilation pipes are installed above the workshop. At the same time, a flap-type exhaust gas collection system or a accompanying exhaust gas collection system is installed at the stations where the engine needs to be started, such as exhaust gas detection and drum testing, to avoid vehicle emissions The impact of the exhaust gas on the workshop environment. In order to save energy, a large number of skylights are installed in the workshop for natural lighting, reducing the power consumption for lighting.
The logistics transportation system is a highlight of the assembly shop. The use of high-speed Ethernet has brought the assembly shop closer to the parts suppliers. When the inventory in the final assembly shop is lower than the set value, the logistics system will automatically contact the parts suppliers for replenishment, which improves the efficiency of the supply system. At the same time, the automatic feeding system from the batching area to the side of the line realized by the automatic navigation car greatly reduces the consumption of human resources and reduces the probability of mismatched parts.
The assembly shop is equipped with various equipment that can reduce the labor intensity of workers. For example: hangers and brackets that can automatically lift the body according to the installation project, seats, wheels, and center console assisted installation of mechanical arms, wheel bolts electric tightening tools, etc.
In order to ensure the traceability of the installation quality, the tightening torque data of each key bolt on the car body will be transmitted to SAIC GM's server via Ethernet for storage, so as to trace possible installation quality problems. The quality management system will also monitor the tightening torque of each bolt from the electric torque wrench in real time, and immediately notify the workers on the production line to deal with the problem when it is found. This system is crucial to the improvement of the installation quality of the whole vehicle.
The Cadillac CT6 equipped with a 3.0T engine is equipped with a full-time four-wheel drive system. In general, the system distributes the front and rear axle torque in a ratio of 10:90. When the system detects wheel slip, it will dynamically distribute the front and rear axle torque according to the wheel slip. If necessary, the four-wheel drive system can distribute the front and rear axle power at a ratio of 50:50.
Some Cadillac CT6 high-end models are equipped with MRC electromagnetic suspension system. The core of the system is the electromagnetic shock absorber manufactured by Jingxi Heavy Industries, which controls the characteristics of the electromagnetic fluid inside the shock absorber by changing the magnetic field so that the damping of the shock absorber can be dynamically changed according to the road conditions. The MRC electromagnetic suspension system can perform 1000 adjustments per second, enabling the Cadillac CT6 to filter out most of the fine vibrations of the road surface and maintain sufficient support when cornering quickly and encountering large undulating roads.
At present, the assembly shop is carrying out the assembly of Cadillac 2.0T and 3.0T models in a 1:1 ratio. The main production on the day of the visit was 2.0T models, so we could not see the structure of the rear-wheel follow-up steering system on the 3.0T models. This system enables the rear wheels to achieve a maximum turning angle of 3.5°, thereby reducing the turning radius of the vehicle at low speeds and improving the handling stability of the vehicle at high speeds.
The 2.0T engine used on the Cadillac CT6 has been localized. The 8-speed automatic gearbox (code-named 8L45) that matches the 2.0T engine is an imported part. The 3.0T engine with closed-cylinder technology that can shield two cylinders under low load conditions and the matching 8-speed automatic transmission (code 8L90) are also imported.
Advanced technology such as a steel-aluminum hybrid body, two-layer color paint/colored varnish, as well as electromagnetic suspension, rear-wheel steering system and other configurations have made the factory's first off-line model, the Cadillac CT6, a product strength that has advanced to the BMW 5 Series. , Mercedes-Benz E-Class and Audi A6L challenge the strength. After reading this article’s introduction to Cadillac’s Golden Bridge plant, do you have stronger confidence in the CT6 in front of the screen? Our next article will also provide an in-depth analysis of the various workshops of the factory. If you are interested in the CT6 manufacturing process, you should definitely not miss it. (Photo/Text/Photo by Chang Qinglin/Li Boxu)