Bernard:
Thanks for the reply and offer. The formulas are lengthy and detailed.
Will this forum accept lengthy replies, or are there another email address
which I can send the formulas?
I will try it anyway. This is quoted from the book.
Estimating Flat-Blank Lenghts.
When a given piece part is produced by bending, the length of its required
workpiece "in the flat" is the same as the length of its neutral plane.
Estimating the required flat workpiece length is a matter of determining the
theoretical length of the neutral plane. To determine the theoretical length
it is necessary to calculate the bend allowance "A" for each bend. The
estimated blank length will then be the sum of the lengths "L" of the bend
legs and the allowances. Then, where "B" is the length of the flat blank; B=
L1 + A + L2, etc.
To find "A"
A = (R+C)0.01745N
Distance "C" from the inner surface to the neutral plane is a variable
factor depending largely upon the ratio of the stock thickness "T" to the
bend radius "R". Optimum value for "C" can be considered to be:
Where R < 2T then C=0.33T
R=2T to 4T then C=0.4T
R>T then C=0.5T
Thus, for any bend angle
Where
R<2T A=(R+0.33T)0.01745N
R=2T to 4T A=(R+0.4T)0.01745N
R>4T A=(R+0.5T)0.01745N
Example 1.
T = 0.030
L1 = 1
L2 = 2
L3 = 1.25
R1 = 0.18
N1 = 90
R2 = 0.09
N2 = 45
Then:
A1 = (0.18 + 0.015) 90(0.01745)
= (0.195) 1.5705
= 0.306
A2 = (0.09 + 0.012) 45(0.01745)
= (0.102) 0.785
= 0.080
Since B = L1+A1+L2+A2+L3
= 1 + 0.306 + 2 + 0.080 + 1.25
= 4.636
There can be a variable amount of bends to any flat blank.
I cannot define a formula to find "C"
Any help would be appreciated.
Lloyd
