The elevator car is mainly composed of door panels, wall panels, three-piece sets (front wall, control wall, door light beam), ceiling decoration top and other components, as shown in Figure 1. The material is generally 1.0-2.0mm stainless steel plate or cold-rolled carbon steel plate. The processing route is generally cutting by a shearing machine, then punching or punching directly by laser cutting, and finally bending and forming.
In the bending process, in order to ensure product quality, it is necessary to set the min bending radius, min bending straight edge, min hole edge distance and other extreme values. Different plates have different min bending radii due to their different elongation rates. Among the commonly used thin metal plates, the min bending radius is shown in Table 1, where t is the thickness of the sheet.
The minbending straight edge refers to the distance from the boundary of the sheet to the bending edge. If its length is too small, it may cause bending deformation and even damage the mold. The distance is generally h> 2t.
Hole margin refers to the process route of punching first and then bending. If the position of the hole is in the bending deformation zone, the hole will be deformed during bending. When t ≤ 2mm, the hole margin S ≥ t+r; when t ≥ 2mm, the hole margin S ≥ 1.5t+r.
Bending sequence
When formulating the bending process route, the bending sequence is also an important content. Improper bending sequence may cause a large deviation in the forming size of the part, and even interfere with the result that the bending cannot be completed. In the bending process, the following four basic principles are generally followed: ⑴Bending from the inside to the outside; ⑵Bending from small to large; ③Bending special shapes first, and then general shapes; The process does not produce influence or interference. For example, when bending the control wall, the bending follows the principle of from inside to outside, and the bending sequence is shown in Figure 3.
Common problems and solutions of SMART CNC bending in CNC bending machine
After potential problems are discovered during the bending process, they need to be optimized and resolved in time. In the elevator car bending process, there are mainly the following problems.
The forming size does not match the drawing
The main reasons for the inconsistency of the forming size of the workpiece with the drawing are the error of the cutting size, the inaccurate bending positioning and the cumulative error of multiple bending. The solution is: adjust the bending coefficient, recalculate the unfolded size; adjust the positioning; select a reasonable positioning benchmark to eliminate the accumulated error. If the cutting size error and the accumulated bending error are within the allowable range, the forming size can be guaranteed first, and the error can be accumulated on the non-assembly side that has no effect on the workpiece.
Bending angle deviation
The bending angle of the workpiece is too large or too small to cause bending angle deviation, mainly due to improper V port of lower die, improper setting of die springback compensation parameters and mismatch of press brake pressure, etc. The solution is: refer to the bending mold table to select the appropriate lower mold, adjust the rebound compensation value and the pressure of the bending machine.
Cracks on the bend edge
The main reasons for cracks in the bending edge include too small bending radius, parallel plate texture and bending line, blank burrs facing outwards, and poor material plasticity. The solution is to increase the bending radius or grooving; change the direction of the workpiece layout; change the direction of the burr and place it on the inner corner of the workpiece; replace the material with better plasticity.
