Automobile welding fixture is a fixture used to ensure the size of the weldment, improve assembly accuracy and efficiency, and prevent welding deformation. Its design is a highly empirical and comprehensive technology. When designing, you must first determine the production program, be familiar with the product structure, understand the deformation characteristics, grasp the precision of the parts and assembly, and understand the process requirements, and then you can perform a full range of welding fixture the design of.
The car body is generally composed of an outer cover, an inner cover and a skeleton member. The thickness of the steel plate of the cover member is generally 0.8-1.2mm, and the thickness of the steel plate of the skeleton member is mostly 1.2-2.5mm, that is, they are mostly thin plate members. For welding fixture design, it has the following characteristics:
Complex structure shape, difficult composition
The car body is a space shell made of sheet metal stamping parts. In order to have a beautiful appearance and a certain rigidity of the shell, the parts that make up the body are usually drawn and formed into a space curved body with a complicated structure.
Poor rigidity and easy deformation
The formed sheet metal stamping parts have a certain degree of rigidity, but the rigidity is much worse than that of machined parts, and a single large stamping part is easily deformed. Only after welding into the body shell, it has strong rigidity.
Assembly accuracy includes two aspects: appearance accuracy and skeleton accuracy, appearance accuracy refers to the gap surface difference after door assembly, and skeleton accuracy refers to three-dimensional coordinate values. The assembly accuracy of the truck direction is generally controlled within 2mm, and the sedan is controlled within 1mm. The design of the welding fixture must not only ensure the welding requirements between the process parts, but also the overall welding accuracy, and adjust the matching state between the process parts to meet the overall assembly requirements.
The purpose of welding fixture design is to limit the freedom of movement in 6 directions. This limitation not only depends on the positioning and clamping device of the fixture, but also on the mutual constraint relationship between the parts. Only by correctly understanding the characteristics of welding production of sheet metal stamping parts, and correctly understanding the 6-point rule, can this principle be correctly applied.
The body welding assembly is generally composed of the bottom plate, the front wall, the rear wall, the side wall, and the top cover. Different vehicle models have different division methods. When selecting a positioning benchmark, generally:
1.Ensure the assembly size of the door opening
2.Ensure the accuracy of the position of the front and rear suspension holes
3.Ensure the assembly size of the front and rear wind windows
Modularity of fixture components is the basis for achieving combination. A series of standardized and standardized fixture components with modularized design to quickly assemble various fixtures has become the basis for the development of fixture technology.
The design of automotive body welding fixtures is closely related to the structure and accuracy of stamping parts, process parts, and is full of rich particularities. In the design, in addition to considering general rules, specific issues must be analyzed.