create metal plate 50mmx100mm, bend on the press brake , measure 2 sides for example 50mm+52.6mm=102.6mm. the number over 100mm is your bend deduction. 2.6mm
The key to coming up with the correct bend deduction is knowing what the final bend radius will be. Weither you're air bending , bottom bending or bending sharp the radius can still be figured out from the elongation factor. Bend deduction= 2 times outside setback - the bend allowance. Bend allowance = .(017453 x bend radius) + (.0078 x material thickness. Outside setback = material thickness+ the radius. ( only for 90 and 180 degree bends).
I believe your asking what opening to use for ur bends. So for anything up 1/8 material thickness you can go from 6 to 8 times the material thickness for ur vee opening (exp. Mat. =. 040 thick, times 6=.240 .040 X 8=.320 So for a sharp radius punch your vee opening should be from. 240 to. 320
Grain direction affects spring back more than anything. Meaning, it leads to variation in angles more so than bend deduction. You could definitely test this and see for yourself, but I think you will get similar results in bend deduction as long as your bend angle is always at 90 deg.
Nooo..... 😖 I cringe when I hear people refer to the bend deduction as "stretch". It's sooo misleading! BD is influenced by the stretching and compressing that takes place, but BD itself is not ALL "stretch". Your example...1.5mm BD does not mean that the flat part was elongated by 1.5 mm..... Good technique for finding the BD though... As long as you get the right value for your BD, it doesn't matter what makes it what it is (despite my rant above).
if you understand tensile and yield strength and what the material is doing under stress the term stretch out is pretty accurate. The key to coming up with the correct bend deduction is knowing what the final bend radius will be. Weither you're air bending , bottom bending or bending sharp the radius can still be figured out from the elongation factor. Bend deduction= 2 times outside setback - the bend allowance. Bend allowance = .(017453 x bend radius) + (.0078 x material thickness. Outside setback = material thickness+ the radius. ( only for 90 and 180 degree bends).
@@jimb7816 I think you've missed my point....BD is not a DIRECT MEASURE of the AMOUNT of stretch. That is all I was saying. If you arguing that stretching DOES takes place, then there is no need because i dont disagree. There are both tension and compression within the material durring all types of sheet metal bending. But too many people think when the BD is .100" that means the material has stretched by .100" and that is absolutely not the case.
@@jimb7816 Also you realize the BA formula you give here is empirical right? That will not be 100% accurate in all cases. You still have to do your own testing if you want to get completely accurate BD because everything is subject to variables that will change from company to company / scenario to scenario. Even with same material thickness and formed radius you can still have different BD because the k-factor and form shape could be different. That is also a reason I feel the actual formed radius is an elusive thing to base BD off of (like in your method) because it is hard to accurately measure. Have you ever looked at an air bent part under an optical comparator? It is typically not a perfect radius. It is more parabolic in shape. Thats why I have always felt that the BEST way to get accurate BDs is to do as much sampling as possible controlling for ALL variables. Specific punch, specific die, exact material types and thicknesses, bend angle etc. The second you start generalizing you will lose accuracy. In most cases its not a big deal as long as you're close, but if you need anything tighter than .010" or .020" on your flange lengths then you better have your BD dialed in as close as possible.
@@TheEngineeringToolboxChannel I've been bending metal for 25 years and used to be the lead sheet metal Fabricator for NASA I currently own my own business call Press Brake Applications. The empirical formula I quoted works for everything you just need to know how to use it. My name is Jim Bice look me up on LinkedIn I can prove if you would like.
@@TheEngineeringToolboxChannel a parabolic radius is cause from a sharp bend which causes the radius to be a percentage of the material causing the radius to be roughly 60 to 63%. If you know the Radius the formula works perfect!
create metal plate 50mmx100mm, bend on the press brake , measure 2 sides for example 50mm+52.6mm=102.6mm. the number over 100mm is your bend deduction. 2.6mm
The key to coming up with the correct bend deduction is knowing
what the final bend radius will be. Weither you're air bending , bottom bending or bending sharp the
radius can still be figured out from the elongation factor.
Bend deduction= 2 times outside setback - the bend allowance.
Bend allowance = .(017453 x bend radius) + (.0078 x material thickness.
Outside setback = material thickness+ the radius. ( only for 90 and 180 degree bends).
Where do the constants come from? I work with sheet metal a lot and want to know for practical reasona
Great job, thank you!
What is thickness of sample in mm
Thanks, 14.26-12.7= 1.56 if i not wrong hear ur speaking Sir
His math aint mathing lmaoo
How to select v block for bending?
I believe your asking what opening to use for ur bends.
So for anything up 1/8 material thickness you can go from 6 to 8 times the material thickness for ur vee opening
(exp. Mat. =. 040 thick, times 6=.240
.040 X 8=.320
So for a sharp radius punch your vee opening should be from. 240 to. 320
Tom, would it make sense to perform this trial with and against the grain and then average the results?
Grain direction affects spring back more than anything. Meaning, it leads to variation in angles more so than bend deduction.
You could definitely test this and see for yourself, but I think you will get similar results in bend deduction as long as your bend angle is always at 90 deg.
Exactly the grain will not effect your final dimensions
One must never justify using the metric system!
i have know how to make removal part programe for trupunch
Nooo..... 😖 I cringe when I hear people refer to the bend deduction as "stretch". It's sooo misleading! BD is influenced by the stretching and compressing that takes place, but BD itself is not ALL "stretch". Your example...1.5mm BD does not mean that the flat part was elongated by 1.5 mm.....
Good technique for finding the BD though...
As long as you get the right value for your BD, it doesn't matter what makes it what it is (despite my rant above).
if you understand tensile and yield strength and what the material is doing under stress the term stretch out is pretty accurate.
The key to coming up with the correct bend deduction is knowing
what the final bend radius will be. Weither you're air bending , bottom bending or bending sharp the
radius can still be figured out from the elongation factor.
Bend deduction= 2 times outside setback - the bend allowance.
Bend allowance = .(017453 x bend radius) + (.0078 x material thickness.
Outside setback = material thickness+ the radius. ( only for 90 and 180 degree bends).
@@jimb7816 I think you've missed my point....BD is not a DIRECT MEASURE of the AMOUNT of stretch. That is all I was saying.
If you arguing that stretching DOES takes place, then there is no need because i dont disagree. There are both tension and compression within the material durring all types of sheet metal bending.
But too many people think when the BD is .100" that means the material has stretched by .100" and that is absolutely not the case.
@@jimb7816 Also you realize the BA formula you give here is empirical right? That will not be 100% accurate in all cases. You still have to do your own testing if you want to get completely accurate BD because everything is subject to variables that will change from company to company / scenario to scenario. Even with same material thickness and formed radius you can still have different BD because the k-factor and form shape could be different.
That is also a reason I feel the actual formed radius is an elusive thing to base BD off of (like in your method) because it is hard to accurately measure. Have you ever looked at an air bent part under an optical comparator? It is typically not a perfect radius. It is more parabolic in shape. Thats why I have always felt that the BEST way to get accurate BDs is to do as much sampling as possible controlling for ALL variables. Specific punch, specific die, exact material types and thicknesses, bend angle etc. The second you start generalizing you will lose accuracy. In most cases its not a big deal as long as you're close, but if you need anything tighter than .010" or .020" on your flange lengths then you better have your BD dialed in as close as possible.
@@TheEngineeringToolboxChannel I've been bending metal for 25 years and used to be the lead sheet metal Fabricator for NASA I currently own my own business call Press Brake Applications. The empirical formula I quoted works for everything you just need to know how to use it. My name is Jim Bice look me up on LinkedIn I can prove if you would like.
@@TheEngineeringToolboxChannel a parabolic radius is cause from a sharp bend which causes the radius to be a percentage of the material causing the radius to be roughly 60 to 63%. If you know the Radius the formula works perfect!