Press brake basics
The Press Brake
Let's run some simulation to understand this better:
On a V=1" (25mm) every .019" (0,5mm) the ram comes down our part closes more than 2°!!!!
In this V=24mm the 90° sheet bend forms the 45° as part of the triangle shown in solid line.
x and y have the same length and h is 1.414 times x or y (thanks Pitagora for this hint).
Trig ratios always stay the same on right triangles. This is a right triangle and the trig ratio we are interested on is:
Tangent = Opposite/Adjacent
Why? we want to see what happens when y is increased by ^y. Please note that x does not increase, and that is why our angle becomes acute.
But how much ^y is needed for every angle degree closed?
Well.... since trig ratios stay the same we can calculate this:
x=12 (half the V opening)
so... on the new angle (let's call it B) we have:
Tan(B) = 12/12,5 (x/y+^y) = 0,96.. which is the tangent of 43,83° (i used the calculator for that my friend)
Which means that by increasing the ram travel by 0,5mm (.019") we closed our part by over 2° (the triangle is only half of our part bending)
This gives us the idea of how precise every movement of the ram must be in order to obtain correct bends.
To complicate things further we will need to deal with material spring-back which will affect the angle, the radius and the blank we need to cut.
The press brake CNC will calculate the ram travel and adjust for the spring-back, but the radius and the blank might be another story, since that's also related to the V opening used.