bgoldsberry
 
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I need some leads for obtaining recycled/reclaimed sheet/plate metal for CNC cutting.

This is a student project, designing a chair cut from plywood using a three-axis CNC router. I'm thinking that the legs may need to be cut from steel (I have access to a plasma cutter). The two pairs of legs are U-shaped measuring about 18"x26" square.

(1.) What metal thickness will suffice for chair legs? 1/2"?
(2.) How can I not spend hundreds of dollars on a sheet of metal?
(3.) Is recycled/reclaimed a wild goose chase?

Thanks,
Brandon

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1/2" steel is pretty serious stuff. Just to give you an idea, a 12"x12" sheet of 1/2" steel usually weighs about 20 lbs. Because geometry plays a huge roll in overall strength of a structure, we would need to see how you plan on using the sheet metal, otherwise it would be hard to make a recommendation on what thickness you need. As a reference, the chairs that Nxakt posted are likely 1/8" aluminum (anyone else know for sure?) and they look to be strong enough. Are you planning on cutting a strip of steel and bending it into the "U" shape, or cutting the "U" shape from the flat sheet of steel?

Using recycled metal is definitely not a wild goose chase. Here are some things to consider: If the chair is to be a one-off product, then you can find your material anywhere. If the chair is meant to be designed for mass production, then you need a constant source of material. The best option then would be to find outdated metal objects and figure out how to use them for your needs. If you couldn't make that work, then you would probably need to use new materials.

If the chair is to be a one-off product, you could easily source your material from a metal scrap yard. It would be recycled. These places know the value of scrap metal, and will charge you accordingly based on weight. Junk yards and resale shops are another good place to look. Often they base their pricing on the perceived value of the "object" instead of the market price of the material. This means you can sometimes get some good material for less than you would pay at a scrap metal yard.


bgoldsberry
 
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I'm in Iowa.

The chair is to be a one-off for the purpose of prototyping for mass production . . . so both. I was planning on cutting a u-shape from a flat piece rather than bending. However, I realize that bending is far more cost effective.

b

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I realize that bending is far more cost effective.


Be aware that most "steel yards" have odds and ends of various material left over from custom cut orders. These chunks of material usually end up out in a corner of the yard and are referred to as "rems" (remnants); as mentioned, they're sold by weight.

But have you ever tried to bend 1/2" thick plate steel? That is going to take a substantial press, or a lot of heat (and getting an aesthetically pleasing, uniform radius, bend is another thing altogether).

Post a sketch or two and maybe we can help you sort this out.

BTW, welcome to the boards Brandon.
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In North America specifically, all steel is primarily recycled. I believe there are no longer any steel mills left that alloy steel from iron ore, all process scrap metal from industry and post-consumer reclaimed, and have for several decades.

Pricing raw sheet metal usage is quite easy but laborious. Use your awesome CAD skills to estimate how much steel, aluminum, etc. your parts will use, either raw weight or square area. Phone any metal supplier in your area and they should be able to enter your minimal data and give you a price. Be aware though that for volume production this is a misleading figure as the cost of raw material is a small contributor to final part and finished product price. For a one-off prototype, design or statement piece, it's a valid exercise to estimate your cash outlay.

So here's my interesting anecdote. Doing the exact same as you on a project.... I got a price for a quantity of .250" aluminum plate of $111. Two days later when we realized that one prototype wasn't enough (surprise!), the same material was quoted at $540! Some metals market maker in New York, Chicago, London, Rotterdam or Singapore had made a move on aluminum futures and that's the result.


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