Flat Pattern Drawings that Agree with Layout by Hand
Flat Pattern Drawings that Agree with Layout by Hand
(OP)
I am trying to figure out how to adjust the sheet metal settings so the flat pattern dimensions agree with the dimensions I would use when laying out the part by hand. For example, a 2 x 2 (inside lengths) angle would be bent out of 4" wide sheetmetal for thicknesses 11 ga. or thinner. This is not what I get from a SW flat pattern.
What settings must I change?
What settings must I change?






RE: Flat Pattern Drawings that Agree with Layout by Hand
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RE: Flat Pattern Drawings that Agree with Layout by Hand
cliff
RE: Flat Pattern Drawings that Agree with Layout by Hand
RE: Flat Pattern Drawings that Agree with Layout by Hand
BA = bend allowance
R = inside bend radius
K = K-Factor, which is t / T
T = material thickness
t = distance from inside face to neutral sheet
A = bend angle in degrees (the angle through which the material is bent)
RE: Flat Pattern Drawings that Agree with Layout by Hand
"I think there is a world market for maybe five computers."
Thomas Watson, chairman of IBM, 1943.
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Flat Pattern Drawings that Agree with Layout by Hand
The bend radius and k factor will give you an accurate formed part based on the flat it creates providing you use an accurate radius, the k factor can be achieved by experimenting. We use sever different groups of Bend Radius and K factor combos depending on the machine the parts will be formed on and the thickness of the material. For instance for a 20 gauge galvanized part we use a bend radius of .033 and a K-factor of .5 This gives us very accurate part when the parts are formed with Airbending on one of our presses.
A way to figure out what works for you is to cut an accurate flat to 10.000 x whatever width, then put three or four bends in it and draw the part in solid works exactly as it measures (with calipers). Flatten the model and check the size, if it does not measure 10.000 long in the flat model, adjust your bend radius first, it should be 2/3 the material thickness or more. Then when you get it close to 10.000 fudge around with the k-factor til it is exactly 10.000 in the flat model. Run several test parts like this for each material and machine you use (or hand bending method if that is what you are doing). The longer your test peice and the more bends you put in it the more accurate you will be able to set your variables up. Good luck and have fun it is tough at first but if you are going to be designing a lot of sheet metal, setting up your bend radii and k-factor will be worth it.
RE: Flat Pattern Drawings that Agree with Layout by Hand
The one thing I would differ from aamoroso's advice is with regard to the bend radius. The bend radius shouldn't be tweaked, it should be entered as the value of the nose radius of the punch. Generally the inside bend radius should be 1.5 times the material thickness, though this is often violated. Most sheetmetal shops will have a standard set of tools with bend radii of .030, .060, .090, etc. Make sure that you and the shop are using the same value. This too is often violated (the shops would rather use what's in the machine than change to what you've specified). However, you should be designing with standard radii. With that said, we specified the finished formed part, including bend radii. Our flat pattern drawings were provided for their reference only. They (the fab shops) were free to use the FP drawings however they wished, so long as we got the formed part we wanted.
- - -Dennyd
RE: Flat Pattern Drawings that Agree with Layout by Hand
Fortunately it sounds like you have in house sheet metal fab. So you should be able to make the manufacturing process more efficient by integrating SW generated flats into your drawings.
RE: Flat Pattern Drawings that Agree with Layout by Hand
We do have a small shop, but also send out some work. I'll just have to set it up for what I'm used to and mark the flat pattern as reference for shops that do things differently.
Thanks again.
RE: Flat Pattern Drawings that Agree with Layout by Hand
If this is addressed above I couldn't understand it. I was just browsing the forum. If it is already addressed, sorry
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: Flat Pattern Drawings that Agree with Layout by Hand
See this link for an in depth review of bend allowance including neutral axis and K factor
http://
RE: Flat Pattern Drawings that Agree with Layout by Hand
Thanks. The K Factor seems to have covered what I was getting at. I had a formula from an ASM handbook on forming that I used to calculate where the neutral axis was located but couldn't recall the K-Factor.
A great Link!
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com