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
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: