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grs-pms(at)comcast.net
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 Posted: Thu Dec 27, 2007 2:01 pm Post subject: Developed length "dl" |
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"Developed length" comes from the aircraft engineering practice of flat pattern development. Sheet metal parts are trimmed and shaped "in the flat" and then formed by brakes, or over form blocks or dies in presses. A flat pattern must be developed to define the shape of the flat stock which is to be formed. Developed length is the length of the flat stock needed to make the part.
The reason that developed length is not the same as the width or length of the finished part plus the height of the flanges is that the bends do not have sharp corners, but are radiused. In the flat, the dimension of the flange is less than it will be after forming because it takes less material to go around the radius than it would to go all the way to the corner, then make a sharp bend. The term "setback" is used to define the material "saved" by not going all the way to the corner
I can't speak for the way designers define flat parts in this day and age, but 50 years ago flat patterns were developed and drawn by hand (usually by junior engineers and draftsmen). Extensive handbook tables which considered material thickness, bend angle and bend radius were used to define setback. The drawings were then transferred to the material from which templates and forming dies were made.
It was tedious, painstaking work, but there was a certain satisfaction in doing it.
George Swinford
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Thu Jan 03, 2008 4:03 am Post subject: Re: Developed length |
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Developed length to me means, length plus 10 mm, then make part then trim back unused length. LOL
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planecrazydld(at)yahoo.co
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| Posted: Thu Jan 03, 2008 8:11 am Post subject: Developed length "dl" |
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[quote][b]
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