For bending products, we generally to bend the quality and quantity to evaluate. Which is subdivided into the size and angle of the accuracy and bending pieces of the grade (surface indentation, sissa injury and warping deformation, etc.), and the amount refers to the productive
The five factors that affect the bending quality of CNC bending machines are:
(1) mechanical properties, such as machine model, opening 0H, travel, tonnage, etc .;
(2) mold properties, such as the mold, the next model, die seat;
(3) material properties, such as cold rolling, hot rolling, or sheet metal,
(4) processing attributes, such as hollow bending, pressure at the end of bending, stamping bending;
(5) environmental attributes, such as light, dust, noise and on-site 5S management, as shown in Figure 1.
The choice of CNC bending machine and bending mold and the calculation of the bending expansion length are very important for the bending accuracy of the workpiece. The grasp of the bending sequence and other on-site operation is the important guarantee of the bending precision, In this paper, the bottom of the bending process as an example to elaborate. Figure 2 shows the structure of the bottom bending process, where F is the opening width of the lower mold, f is the plate thickness, ^ is the minimum bending dimension, ir is the inner bending radius, and i * r = 5F / 32, then the bending pressure i ^ cxlxfx ab / F (where c = l + 4f / F). A workpiece is pressed at the bottom of the bending method for processing, the workpiece material for the Q235A, thickness of 5mm, length of 5m, yield strength requirements of 45kg / mm2, the cross-section shown in Figure 3.
Calculate the bending tonnage, according to ir = 5mm, then push y = 32, c = 1 + 4×5 / 32 = 1.625, then the pressure F = 1.625 x 5 x 5 x 5 x 45/32 = 286, this result determines Choose a 300t / 5m bending machine. According to the cross-section of the workpiece using CAD to simulate, the results shown in Figure 4, the height of the mold / / = 300mm, the mold height / / T = 110? 130mni, the machine’s opening 0 / = 300 + 110 + 90 = 500) should be above 500mm.
Now the CNC bending machine configuration system can simulate the bending sequence and can automatically calculate the workpiece length L, but in the actual production of this function only play a reference role, and can not be used for actual production. To DELEM system DA-65W, for example, to DIN6935 as the standard calculation, Figure 3, the expansion length of L = 749mm, the bending sequence is the first folding ends, and then folded in the middle, this way obviously can not be dry production.
We know that bending a lot of ways to start, but there are deviations, and more to try to verify the size of the expansion, in this not to repeat. In the actual production, the most commonly used is the deduction method, in Figure 3, for example, rl.0 / V40, t = 5mm, BD = 9mm, then the workpiece length L = 28×2 +55 x2 + 178 x2 +286 – 6×9 = 754 (mm), of course, the thickness of the plate thickness of the 5D value also have a certain impact.
In order to ensure the quality of bending, it is necessary to strictly prepare the technical documents, must specify the upper / lower mold and bending the order, otherwise can not guarantee the accuracy of bending size, bending down mold and bending deduction options as shown in Table 1 Show.
As can be seen from Table 1, if L = 749mm, you need to use F = 60 under the mold, in order to meet the requirements of bending size, but ir too large, can not meet the requirements of the drawings. According to Z> 3mm, V> 8t principle, take 40mm, then the pressure F = 210t, bending machine tonnage requirements smaller and the internal i? Deviation is not. When the dry Hi is 300mm or more, the workpiece is bent with the upper or upper slider to interfere or anti-knife, so the upper mold chooses the straight knife. After bending, in order to avoid warping deformation, the lower table should use the NC bending deflection compensation (compensation center angle) function, although the bending sequence is the first end, but because it is cutting plate or punching reasons , The board straightness and diagonal deviation is large, it can not be used after the post-positioning device (BG-backgauge) as a mountain positioning bending, should first use BG bending two knives, and then use the machine before the positioning device (FG -frontgauge) Bend the other end of the two knives, and finally bend the middle of the two knives can be.
In summary, bending relative to the previous process in terms of technical and technical requirements of the higher, not only the need for on-site operation experience, but also on the machine, mold and other related fields have in-depth understanding. Only try to find the best technology and methods for the product, to create a satisfactory product.