Calculation of the difference between the unfolded length of grooved bending and ungrooved bending.
Grooved fold
For grooved bending, the total length is calculated as:
L=20-0.4+20-2X0.4+20-0.4=58.4
Ungrooved bending
For ungrooved bending, the total length is calculated as:
L=(20-1xt+k)+(20-2xt+2xk)+(20-1xt+1xk)=(20-1+0.2)+(20-2+2×0.2)+(20 -1+0.2 )=56.8mm
Note: “t” represents the thickness of the material and “k” is the coefficient.
The value of “k” depends on the thickness of the material, generally varying between 0.2 and 0.25. The value of “k” increases as the thickness of the material increases.
For this specific case, “k” is selected as 0.2.
1. Groove in square tube
As shown in the figure, a 20 × 20 mm square tube with a plate thickness of 1 mm needs to be grooved and bent.
The thickness “a” of the material remaining in the groove is determined by the size of the right-angle arc after bending, as well as the material thickness “t”.
Normally, when the material thickness is less than or equal to 1 mm, “a” is equal to 0.4 mm. For materials thicker than 1mm, “a” is equal to “t/2”.
The unfolded length of the example shown is:
L=2×(L1+L2)=2x((Edge length-1x-0.2)+(Edge length-2x))=2x((20-1x0.4-0.2)+( 20-2×0.4))= 77.2 mm
Note: For a slotted “L1” end, 0.2 mm is deducted regardless of material thickness.
2. Z-shaped groove
The bending and unfolding length is calculated using the following combination of grooved and ungrooved Z shapes.
For a 2 mm plate, the remaining thickness of the groove material is taken as t/2 = 1 mm. If the customer requires a smaller direct arc, a value smaller than 1mm must be chosen.
Therefore, the unfolding length is:
L=15-1+20-2×1+15-1=46mm
For a 2 mm thick plate without groove flexure, the k factor is chosen as 0.25. Therefore, the unfolded length is:
L=(15-2+0.25)+(20-2×2+2×0.25)+(15-2+0.25)=43mm
3. Multicurvature groove
The following calculation presents an example of a workpiece with multiple bends, both grooved and non-grooved.
Supposing the customer requires a small rounding of the right angle, for a 3mm thick board, the remaining material thickness is chosen as 0.5mm.
Unfolded length:
L = (40-0.5) + (30-2 × 0.5) + (30-2 × 0.5) + (10-0.5) = 107 mm；
For a 3 mm thick board, the coefficient k is chosen as 0.25. Therefore, the unfolding length is:
L = (40-3 + 0.25) + (30-6 + 2 × 0.25) + (30-6 + 2 × 0.25) + (10-3 + 0.25) = 93.5 mm
4. Reverse bending after grooving
The unfolding calculation method is presented below, using an example of reverse bending after channeling.
To calculate the unfolding length for reverse bending after the channel shown in the figure, follow these steps:
L = (20-2 + 0.2) + (30-2 × 2 + 2 × 0.2) + (20-2 + 0.2) = 62.8 mm
