Dimensional considerations in fixtures

by:Top Talent     2020-06-22
?In the welding shop, we use the fixture to position the workpiece in the correct position and clamp it to ensure the correct assembly relationship between the body parts. From the welding of stamping parts to the sub-assembly, then to the BIW assembly, and finally the assembly of four doors and two covers and fenders on the adjustment line, in order to ensure the successful completion of the welding and assembly process, fixtures are essential. ????Classification of fixtures in the welding shop? Welding fixture: mainly used in the welding station of the welding workshop to position and clamp the parts to ensure their smooth welding. Fixture for assembly: mainly used in the adjustment line to complete the assembly of four doors, two covers and fenders. ????Dimensional measurement items in the fixture The base plate, also known as the Base plate, is the mounting base plate of the clamping unit on the fixture. The assembly and measurement standards of the fixture are all on the base plate, which requires flatness. In order to check whether the assembly accuracy and processing accuracy of the fixture can meet the requirements, the fixture measurement reference needs to be measured with three coordinates after the fixture is assembled. The surface of the fixture substrate is provided with a measuring ball to establish a coordinate system or a shape that can create a reference system (general>= 4), and marked with the corresponding coordinate theoretical value. Positioning datum: The main feature of positioning workpiece, which includes positioning surface and positioning hole. Fixture coordinate system: generally refer to the body coordinate system, the rear direction is positive X direction, the right-hand rule is used to judge the Z direction and Y direction, ????Main points of fixture design dimensions: Safety first, in line with ergonomics. The positioning point is consistent with the drawing, no interference with the parts, and the parts are foolproof. The measurement is up to the point, and the accuracy meets the enterprise standard. Avoid welding torches and welding points, and do good welding guidance. The positioning pin is 3-5mm beyond the surface of the workpiece, preferably a fixed pin or a telescopic pin. The pressing force of the pressing block is greater than 50KG to meet the welding requirements. In order to prevent the pressure head from being too tight, a Stop block will be installed at the pressure arm. The support surface should be 20X20mm as much as possible, and the adjustment direction should be consistent with the body coordinate system.
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