SCRAP – STRIP LAYOUT
In the design of blanking parts from strip
material, the first step is to prepare blanking layout,
that is, to layout the position of the workpieces in the
strip and their orientation with respect to one another.
While doing so, the major consideration is the economy
of material.
Another important consideration in strip layout is
the distance between the blanks and the strip edge and
distance between blank to blank. To prevent the scrap
from twisting and wedging between the punch and the
die. The distance must increase with material thickness.
A general rule of thumb is to keep this distance equal
to from 1 to 1.5times the material thickness. The following
figure are example of strip layouts.
A – Front scrap
B – Bridge thickness
(space between parts and strip edge,and part to parts)
C – the distance from a point on one part to the
corresponding point on the next part.
H – Part width
l - Length of part
W – Width of strip
Y – Scrap recovery at end
N – Number of blanks
t– thickness of strip
L – Length of strip
B= 1.25t, when C is less than 2inch
= 1.5t, when C is more than 2inch
C = l + B
W = H + 2B
A = t + 0.015H
Y =L – Nc +B
N = L – B /C
tool operation. Scrap strip layout gives an idea on the
positioning of various punches, stops and pilots.
It ensures the ideal location of blanks in the stock strip.
Several trial layouts have to be made to confirm the
maximum percentage of utilization of stock strip. The
goal should be to have at least 75% utilization.
The percentage of stock used to calculated by the
formula:
% of utilization = Area of one blank X 100 /Lead X Width
Where, Lead = Length of component + Bridge thickness
Width= Breadth of component + 2 X Bridge thickness
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EXAMPLE 1: FOR STRIP LAYOUT CALCULATION
Length of part = 20mm : Breadth of part = 10mm
Thickness of part =1.5mm
Bridge thickness = one times of sheet thickness taken
= 1.0 X 1.5 = 1.50mm
Width of strip W = H + 2B
= 20 + 2 X 1.5 =23mm
Front scrap “a” = t + 0.015H
= 1.5 + 0.015 X 20
= 1.8mm
C =l + B = 10+1.5 =11.5mm
7 comments:
where did you get the 0.015 value on the front scrap "a" formula?
Good
I'm currently working on a progressive die design project.
And the customer has advised to add cookie bites and coining operation in the strip layout of given part (bracket).
So, can anyone please let me know what is cookie bite and coining and why/where it should be added?
It's been explained to me that the “Cookie Bites” are put in place so there are no burrs when trimming the part out in the blank station. This allows for good clean cuts in the parts.
Congratulation for the great post. Those who come to read your Information will find lots of helpful and informative tips. Deep Drawn Enclosures
Give more information
How to find out area for t type blank
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