(1) Thin plate stacking and bending
Limited plate superimposed stretch bending refers to the folding of the two sheets of the sea board in a stretch mold, and the three parts are stretched and bent together during the netting process.
When the thin plate is laminated with multiple layers in the longitudinal direction, the tensile stress is slightly greater than the yield point value of the material but less than the tensile strength value of the material due to the short tensile force and the short bending force of the multilayer sheet material at the same time, and The stretch coefficient of the part is less than the limit stretch number (that is, K, <K.), so the shape and technical requirements of the part can be reached in one stretch and bending. At the same time, after unloading the formed part, although the inner layer and outer layer of the material under tensile stress will produce the same return, the rebound value is generally small, and the stretch-bent part will neither fold nor increase. Thickness and high precision. However, when the multi-layer thin plate cannot be stretched and formed at one time, it needs to be stretched multiple times and the barrel is annealed to relieve stress in each process. In order to prevent the cracking, it is necessary to strictly control the stretching once. For example, the tensile limit deformation of aluminum alloy is in the range of 4% to 8%. For parts with bulges and partially complex reinforcement grooves, since the stretch coefficient is greater than or equal to the limit stretch coefficient (ie K 2 Km), the shape of the part must be stretched twice or more times.
(2) Wool combination stretch bending
Wool combination stretch bending refers to combining several parts on a stretch bending die and simultaneously stretch and bend them with the same polar material. This method is used for parts with the same material grade and thickness. It is required that the wool between each part must be out. The cutting process surplus site of 20~50mm is required, and the process margin and the rough surface of each part must be kept smooth and streamlined.
(3) Combined stretch bending of wool
Wool joint stretch-bending refers to the use of stretch-bending and other forming methods in order to meet the requirements of the shape of the part. It is suitable for sheet metal processing parts that have complex shapes and cannot meet the requirements by the stretch-bending method alone.