Views: 815 Author: Site Editor Publish Time: 2022-10-10 Origin: Site
The result calculated by using the neutral layer of CAD and the K factor of SolidWorks has been checked by actual bending. The expansion of the dead edge is actually L=A+B. The result calculated according to A+B has a small error with the actual processed size can be ignored.
When unfolding a large arc bend, select the neutral layer when unfolding with CAD, and the neutral layer is the position between the inner circle and the outer circle after bending. For example, the outer circle of bending is R20. Go to half the thickness of the board.
As shown in the figure, the green line and the neutral layer are the arc length of the green arc.
Of course, some factories calculate that the bending is wrong according to the neutral layer, then adjust the position of the green line in the above picture according to the size difference after bending.
We generally follow this formula to calculate the step difference bending expansion as shown in the figure below
Expanded length L=A+B+C (net size)-plate thickness+0.4
The 0.4 added at the back can be adjusted, see the size adjustment after processing
4 Right-angle bending and unfolding
Right-angle bending: unfolded dimension L = outer dimension plus minus bending deduction
After these 4 methods are explained, let's look at this picture to calculate the bending and unfolding size.
First look at the expanded size of the section difference
L1=20+120+3-1.5+0.4=141.9
Arc bend spread is the length of the perimeter of a quarter circle of the neutral layer
The arc radius of the neutral layer is 20-0.75=19.25
Expand L2=3.14*19.25/2=30.22
Dead edge and right-angle expansion
L3=20+120+100-2.36=337.64
The above 2.36 is the bending deduction for the right-angle bending of the plate thickness 1.5
So the expansion of the above figure is
L=L1+L2+L3=141.9+30.22+337.64=509.76
The simplest calculation method of the bending coefficient is the empirical formula of the 90-degree bending coefficient: the calculation method of 1.7 times the material thickness.
In the 90 sheet metal bending process, a right-angle bend is reduced by 1.7 times the material thickness. For example: the material is 1mm iron plate, the bending angle is 90 degrees, and the bending dimensions are 100 and 50 respectively, then the calculation and expansion method is: 100+50-1.7=148.3mm. The calculation is to expand the length. This 1.7 is said to be 1.6 or 1.65 times, which can be slightly adjusted. Because the bending dies used by each sheet metal factory are not the same, there are slight errors, and they can be used without adjustment. If the requirements are high, you can adjust them slightly.
A special angle is mentioned here, and the bending coefficient can be calculated in a simple way. When the sheet metal bending angle is 135 degrees, the bending factor can be reduced by 0.5 times the material thickness. For example: the material is 1mm iron plate, the bending angle is 135 degrees, and the bending dimensions are 100 and 50 respectively, then the calculation and expansion method is: 100+50-0.5=149.5mm. Other sheet metal thicknesses can also be calculated in the same way. Only applicable to 135 degrees, other angles are not available.
There is also a special angle bend in sheet metal bending, which is sheet metal hem, also called dead edge, which can be calculated in a simple way.
The bend factor is equal to 0.4 times the sheet metal thickness. For example: the material is a 1mm iron plate, the bending is a dead edge, and the bending dimensions are 100 and 10 respectively, then the calculation and expansion method is: 100+10-0.4=109.6mm.
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