Confused about Bend Allowance / Formula / Conversion
Hi, I'm trying to put the bend allowances of our sheet metals in a bend table Pro/E, but I'm confused about the help files. It's clear to me that for an angle of 90 degrees, the standard conversion formula would be: L=2*(T+R)-A (where A = allowance) But for angles below 90 degrees, my guess would be that the conversion formula would be: L=2*(T+R)*tan(ANG/2)-A Am I missing the point of the conversion formula, or is my formula right and is the help incomplete?? See http://downloads.neoposttechnologies.nl/neopost5/bend_allowance.jpg Am I using the right dimensions for x and y here?? Thank you for any clues! Kind regards, Jaap Kramer
RE: Confused about Bend Allowance / Formula / Conversion
Jaap, We currently let the sheetmetal mfg vendors deal with the bend allowance since they make the adjusments based on the machines they are using. Pro/E will work out the bend allowance automatically by using K-factor calculations. (In Pro/E the Y-factor = K-factor *pi/2 Bend allowances are calculated using a K-factor as follows: BA=pi(R+kt)A/180 where: 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) provided you know the correct K-factor to use ref only, these can vary Aluminum K-factor of .4850 steel Kfactor of .4800 Stainless Steel K-factor of .3900 Hope this helps
Minor correction: I think it should be T, not t, in your BA equation. (The purpose of the ratio K is to extract t from T.) Agreed that, in general, you should let your vendor make the BA calculations, unless, of course, you are the vendor.
Further note: Why bother with a Y-factor, since it is merely a constant (PI/2) times theK-factor? One way of seeing its utility is to look at its value for simplifying the arithmetic in a particular way. Generally, the Bend Allowance formulae and tables are normalized for 90 deg. For other angles, simply multiply by A/90. So, for 90 deg.: L=PI/2(R+KT)L=PI/2(R)+PI/2(KT) but, since Y=PI/2(K), this simplifies to: L=PI/2(R)+Y(T) In other words, L=l+YT, where l is the length on the inside radius (No calculation using PI required).
Hi, thanks for your answers! In the end, I found out that it was the conversion formula that confused me. I just skipped the conversion formula alltogether, and simply made correct formulas for each material / thickness. This way, it gives exactly the desired results. For example: