First, groove the sheet metal before bending.
From the bending process, it is known that after bending, the decorative surface and edges of the bent workpiece are arc-shaped, with the radius proportional to the thickness of the metal sheet. The thicker the sheet metal, the larger the radius of the arc formed during bending. In the assembly of elevator cabins, if the bending radius is large, there may be significant gaps in the joints of the cabin wall panels and the bent ceiling panels, affecting aesthetics. In this regard, for some elevator cabins with special assembly requirements, we generally groove the sheet metal first before bending. Grooving the metal sheet significantly reduces the remaining thickness of the sheet, thereby reducing the bending radius of the workpiece and effectively controlling assembly gaps. Due to the thinner remaining thickness at the bending area after grooving, the deformation force during bending is correspondingly reduced, without spreading to affect the unbent areas. As a result, the glossiness on the surface of the bent area of the workpiece is greatly reduced. Besides the advantages mentioned above, grooving before bending also reduces the tonnage required for bending equipment, facilitates bending complex workpieces, and better controls springback. Additionally, there are several key points to consider in grooving processes. The depth of the groove varies depending on the thickness of the metal sheet. In the grooving and bending process for elevator cabins, the remaining thickness after grooving is generally 40% to 50% of the original sheet thickness. For example, for a sheet thickness of 1.0mm, the groove depth is 0.5mm, leaving a thickness of 0.5mm; for a thickness of 1.2mm, the groove depth is 0.7mm, leaving a thickness of 0.5mm; for a thickness of 1.5mm, the groove depth is 0.9mm, leaving a thickness of 0.6mm; for a thickness of 2.0mm, the groove depth is 1.2mm, leaving a thickness of 0.8mm. Shallow grooving may result in unclear bending effects, while excessive depth can affect the structural strength of the workpiece. Regarding the angle of the V-groove, even though springback is significantly reduced after grooving, it still exists. Therefore, when grooving a V-shaped groove, the groove can be flexibly adjusted based on the bending angle of the workpiece. The angle of the V-groove for stainless steel thin plates should be 1° to 2° greater than the forming angle, for example, for a workpiece with a forming angle of 90°, the V-groove angle is generally 92°. This helps to avoid angle errors caused by bending springback.
