Re: Getting Metal Bent

"Rich Grise" wrote
I'm designing a sort of rack to carry hot plates with. I've come up with a
> sort of finger thing for the underside of the plates, made of probably
> 304L or 316L, about .093 thick, bent to look like this:
>
formatting link

> And I'm wondering, how do I present this to a metal-bending outfit? >
> Will just the 3 views + isometric do, or should I show them the pre-bent
> flat profile and call out the bends, or something else?
>
Far more complex parts have been made with just a three view print. When
using a program that will make a flat pattern for you, I would add that to
the drawing (make sure you have the correct material, and gauge set to get
the correct bend allowances). The isometric should only be used to make
visualizing easier, so add it if it does not crowd your print.
Just remember when in doubt ask your venders for their preferences, they
have to do the work so have a vested interest in getting what they need to
make you happy (and maybe make it better). Some of the preceding depends on
volume, for a couple prototypes you obviously can leave more to the vender
then a high volume production item.
Reply to
Stephen B.
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Three views are not very intuitive. And an isometric does not provide as much insight as you might want.
But I think that a flat outline of the sheet material and an isometric of the formed rack might do the job. A stamping diagram with multiple racks set out to optimize the material might also be helpful?
Brian Whatcott Altus OK
Reply to
Brian Whatcott
A lot of sheet metal vendors will take your 3D model directly. Most will develop their own flat pattern based on your drawing and/or 3D model. Be careful if you supply them the flat pattern that you use the correct K values, bend allowances, etc.
Reply to
ms
Any metal bending shop has the tables for this. The short answer is, "yes, it compresses on the inside and stretches on the outside." But the neutral axis isn't exactly in the middle and the amount you "lose" in overall dimension depends on the metal thickness, bend radius, and bend angle.
There is an empiracal formula for determining bend allowance (the amount of material actually in the bend) based on the length of the neutral axis. You add that dimension to the flat side lengths to get the flat template dimensions:
Per degree of bend, the bend allowance = 0.0078T + 0.1743R.
However, given a 3-view with overall dimensions, any compentent shop can figure out what the right flat template is that will bend up to your final dimensions.
Tom.
Reply to
Tom Sanderson

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