How to effectively implement the car body assembly

2022-08-22
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How to effectively implement the car body assembly process

at present, domestic and foreign automobile enterprises have undergone major changes in the planning of the car body assembly welding production line. While paying attention to the improvement of body design, body welding process, plant expansion and equipment renewal, car manufacturing enterprises also actively adopt new technologies and processes such as laser welding, multi head automatic welding machine, welding robot, measurement and hybrid assembly automatic line, as well as various ways such as improving the transmission line, in order to plan out ways that can not only implement flexible production, but also ensure good product quality, simple manufacturing process A car body assembly and welding production line with short production cycle and low investment cost

planning of car body assembly and welding workshop

1 Selection of facilities and equipment

the car body assembly assembly and welding workshop should not only consider the lean and modular design concept, but also consider the flexible production of different categories and specifications of products, and also pay attention to the configuration of quality control methods in the formation process of different categories and specifications of products

(1) it should meet the system requirements of product processing. Due to the different functions of car body parts, these parts will have different product structures. Enterprises should choose different welding equipment and determine different testing equipment according to different product structures. In order to ensure the stability of welding arc voltage of these welders, the production line should be equipped with reliable regulated power supply to limit the change of arc voltage in the workshop circuit to within 0.5V; A large amount of exhaust gas will be generated during the assembly and welding of the car body. In order to ensure the stability and service life of the testing equipment, exhaust devices must be installed in the workshop and temperature control devices must be installed in the three coordinate test room. The welding methods such as circulating water cooling and gas protection used in vehicle body assembly also put forward control requirements for circulating water quality, mixing ratio of gas source and gas flow

(2) the ability requirements of welding equipment and testing equipment shall be ensured. First of all, the selected testing equipment and welding machine should have good and stable mechanical and electrical performance; Secondly, all kinds of welding machines should meet the special process requirements for the welding of their processed products, and the welding torch should ensure that the four-dimensional space can be adjusted steplessly according to the product welding process trajectory; Finally, the testing equipment and welding equipment should be able to meet the objectives of mass and efficient production. The testing equipment and welding machine should also meet the adjustment requirements of multi variety testing ability and welding ability of products, as well as various production rhythms

(3) pay attention to the main technical parameter requirements of testing equipment and welding equipment. The main technical parameters of the testing equipment should be considered from the aspects of input power supply, working voltage regulation range, testing accuracy, testing stability and testing speed; The main technical parameters of welding equipment should be considered from the stability of input power supply, rated welding current, working voltage regulation range, rated load duration, wire feeding speed, welding speed, empty stroke speed, etc

2. Determination of process method

the process evaluation of car body assembly should be considered for the following points:

(1) purpose of welding process evaluation. The purpose of the evaluation is to determine the parameters of various welding equipment and welding process according to the welding requirements of different products for different product structures, raw materials and auxiliary welding materials

(2) welding procedure qualification content. Its main content is to select the best welding method, welding sequence and replacement frequency of welding vulnerable parts (electrodes and electric nozzles) by determining the welding environment requirements, product raw materials, welding auxiliary materials (welding wires, welding rods, welding flux, shielding gas) and the shape and angle of cutting before welding of plates and quality inspection methods, To select the most reasonable range of welding equipment parameters (input power supply, rated welding current, working voltage, rated load duration) and welding process parameters (welding current, arc voltage, wire feeding speed, welding speed, idle stroke speed, gas mixing ratio and gas source pressure)

(3) welding procedure qualification procedure. The enterprise shall put forward the "product welding procedure qualification assignment" according to the performance requirements of different product parts of car body, product structural characteristics, welding steel, welding accessories (welding wire, welding rod, flux, shielding gas), etc; The assignment shall specify the requirements of welding environment, welding process method, welding auxiliary materials (welding wire, welding rod, flux, protective gas), testing items, etc., and shall also clarify the specific range of welding equipment parameters and welding process parameters; Then, under the supervision of the welding engineer, the relevant personnel shall implement it according to the specified assignment, and the welding engineer shall determine the welding process and welding equipment according to the physical quality and effectiveness of the product

3. Determination of test items

(1) establishment of test items. There are two bases and one principle for the establishment of the inspection project for the assembly and welding of various parts of car body assembly: the two bases are that each part of car body assembly must meet the requirements of product standards with the least deformation, and each part of car body must meet the technical requirements of specific users after formation; One principle is that the assembly and welding of all parts of the car body must be completed with high efficiency

(2) determination criteria of test items. Due to the different quality requirements of each part of the body assembly and welding, the judgment basis of the welding inspection items of each part must be formulated according to the special requirements, safety requirements and reliability requirements of each part product. Therefore, the inspection specification prepared according to the judgment criteria of welding inspection items must clarify the quality characteristics, inspection methods, inspection means and inspection frequency

(3) allocation of inspection means. In order to realize the stable quality of car body assemblies and components produced under a series of experimental conditions such as stretching, tightening and tearing of various shaped auto parts and other items, it is necessary to determine appropriate detection means according to different product characteristics, process characteristics and the production tempo of the actual welding production process of each component, so as to ensure the product quality requirements

assembly and welding process design of car body assembly

1 Welding procedure of four door and two cover assembly

in order to realize the beautiful appearance and product safety of four door and two cover assembly, foreign automobile enterprises first start from the improvement of product design. For example, the four door and two cover assembly of a GM car originally had more than 900 parts. Through the design improvement of replacing small parts with large sheet metal parts and assemblies, the use of parts was reduced by about 45%; The second is to ensure product safety through technological innovation. With the continuous development of the global construction market, the company adopts multi-functional spot resistance welding machine to weld the outer plate, reinforcing plate and bumper plate of the door cover. At the same time, it applies advanced gluing and flanging technology, which reduces the weight of the product structure and improves the flatness, strength, rigidity and assembly accuracy of the external surface of the product

2. Welding procedure of left and right side wall assemblies

due to the complex design structure of the left and right side wall assemblies of cars, foreign automobile enterprises originally used mobile spot welding guns for manual welding. In order to improve production efficiency, GM first improved the mobile spot welding gun to reduce the total number of welding and achieve automatic welding; At the same time, the welding wiring of the left and right wall assemblies is transformed, and the rotary table conveyor and the welding fixture of the left and right walls that can act alternately are installed to realize automatic clamping on one side and automatic welding on the other side, so that the parts can be transported by the mechanical conveyor belt according to the specified production pace, and electronic eyes are installed on all automatic welding machines used for assembly to prevent accidental operation

secondly, some parts of the left and right wall assemblies are made of new materials, such as the interior trim panel and the hand rest are cast into one by plastic, so as to realize simple, firm and clean assembly; Adopt new processes for some parts of the left and right side wall assemblies, such as laser welding instead of overlap welding, so as to make the weld smooth and smooth, so as to reduce the weight of the left and right side wall assemblies; In order to improve the welding process of the left and right wall assemblies, General Motors also adopts the bonding process to combine the internal buffer block, reinforcing block and cross reinforcement, and adopts the new process of high-frequency heater heating. The use of these new processes not only reduces the processing time, but also greatly improves the product quality

3. Welding procedure of underbody engine compartment assembly

underbody engine compartment assembly is a key component of car body assembly. The welding and transportation system of underbody engine compartment assembly of General Motors adopts the transmission line type, and the workshop uses hooks to transport, lift and lower along the runway. The allowable positioning error between sub assembly groups is about 1 mm. The assembly of the underbody engine compartment assembly is completed on the mobile assembly platform. This welding platform is composed of five station assembly platforms, each of which is connected by tracks. The parts to be welded are sent to the station through the power driven conveyor belt, and are automatically divided on the mobile conveyor belt, so that the underbody engine compartment assembly can be correctly positioned and clamped in the specified station of the assembly platform

the work content of the first and third stations is installation; The work content of the second and fourth stations is welding, which is to complete the laser welding of the bottom plate and the engine compartment through multiple automatic welding robots; The work content of the fifth station is the assembly and welding of the underbody engine compartment assembly, which is to weld the completed underbody and the engine compartment after closing. This is also completed by laser welding through multiple automatic welding robots. The completed underbody engine compartment assembly is sent to the assembly and welding production line of the body assembly through the power driven conveyor belt

4. The welding process of car body assembly

the welding and transportation system of car body assembly of General Motors also adopts the transmission line type. The workshop uses hooks to transport, lift and lower along the overhead lane, and the allowable value of positioning error between sub assembly groups is also about 1 mm. Automatic line is adopted for the assembly of body assembly, which has the ability of automatic positioning, automatic clamping and automatic loading and unloading

the conveyor belt of the body assembly assembly platform adopts a high-power mechanical conveyor, which can complete the correct indexing within 8 seconds. The vehicle body assembly assembly assembly platform first automatically places the chassis engine compartment assembly on the vehicle body assembly assembly assembly platform through the accompanying fixture, and correctly positions and clamps it in the specified station, and then automatically moves the left and right wall assemblies into the vehicle body assembly assembly assembly platform through the accompanying fixture by the end of 2016, and positions and clamps it according to the specified station. The integral roof is sent to the vehicle body assembly assembly assembly station through the overhead conveyor line by the accompanying fixture, Then position and clamp according to the specified position. When these assemblies are positioned and clamped, start welding the key parts of the body assembly as required

in order to ensure that the body assembly has sufficient stiffness and the body structural dimensions have sufficient accuracy, more than 90% of the 1600 welds on the body are laser welded by more than 70 automatic welding robots. After completing the welding of the positioning weld of the body structure size, the accompanying fixture will be automatically removed, and the body assembly will leave the assembly line of the mobile body assembly and enter the special conveying system. There are several automatic welding machines on both sides of the special conveying system to complete the laser welding of the remaining welds of the body assembly. Each automatic welding machine correctly repeats a series of specified action instructions according to the specified procedures. After all are completed, the body assembly automatically assembles the door and other components, and then enters the paint workshop

quality control of assembly and welding of car body assembly

1 Welding strength inspection

welding points of car four door and two cover assembly, underbody engine compartment assembly and left and right wall assemblies

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