Depending on the complexity of the shape , thinner simpler parts can be cut by shearing or punching . Routing is also used, as is CNC routing. Water-jetting also works for any of these parts and these days is not any more expensive than other methods. With Laser you will have to deal with a heat affected zone at the periphery of the parts. A great deal will depend on the capabilities of your prototype shop. With any of these parts the greatest time is involved in either laying out the part, or programming the tool path to cut it on a machine.
B.E.

You are judged not by what you know, but by what you can do.

Will a hand held jig saw with a paper template glued on not work? Cheap and fast.

Berkshire: I should have mentioned this would be for complex shapes. I would prepare drawings in CAD and on send for fab. Like you say, for these automated processes, I would be guessing the majority of cost is in the setup.

Compositepro: Ha, speaking of, have you seen shapertools.com ? - generally for wood working, but it adapts a fairly standard router to a handheld CAD controlled platform.

For the thinner sheets, consider steel rule dies, in a mechanical press or a hydroforming press. The latter can also simultaneously emboss stiffeners and raise minor flanges.

Mike Halloran
Pembroke Pines, FL, USA

Whilst the CNC tools have superseded most of the disposable die methods , for many years I made that style of tooling . A hardened steel top die pressed through a relieved 6061 t6 tool plate bottom die, would cut several hundred aluminum parts before the bottom die was replaced and the top die re sharpened.
B.E.

You are judged not by what you know, but by what you can do.

1/4" isn't really "thin" aluminum IMO..
A turret press (Amada,etc..) is typically the most cost effective depending on volume,etc... for sheet metal
A laser or waterjet is more expensive vs turret press..

Blank on the turret press and form in press brake/roll former..
But that all depends on the specifics of the part..

One thing to watch out for with punching methods is micro cracking at the periphery of the part, a lot of aircraft parts made by turret press have holes punched undersize, and are then opened up by drilling to remove any possible micro cracking. You do not have this problem with routing, although a lot of CNC routers are fitted with dedicated drills to save wear and tear on spindle lead screws.
B.E.

You are judged not by what you know, but by what you can do.

We cut aluminum sheet from .040 to .25 on the table saw with a carbide tipped blade. We use a saw wax on the blade. We also use a radial arm saw for cit off. I even use it to chamfer square and rectangular tubing, angles and channels for welding. It amazing how accurate you can cut these with just a good tape measure and a sharpy pen.

I made an aluminum back rail for the radial arm saw as the original wasn't square. I can cut trailer parts to under .010" almost every time. You can take a " fuzz cut" to trim on occasion if necessary.

The nice thing about these saws is that only a little wire brush work is necessary prior to welding.

You need to wear sealed goggles and a face shield to protect against hot chips.

For years I cut Aluminum plate from 1/8" to 3/8" on a table saw with a carbide tipped blade, I do not classify this as "THIN" sheet metal. The OPs question was about cutting THIN sheet metal. The problem with the way this thread is going is the definition of thin. To an aircraft worker or a roofer anything less than 0.020" is thin , to a boat builder anything less than 0.375" is thin.
B.E.

You are judged not by what you know, but by what you can do.

I have a 48" x 24" CNC router fitted with a Porter Cable router. I cut 6061 with it regularly. I use wax. I stick with cutting no deeper than the mill diameter. I typically use an 0.062" mill but have gone down to 0.031". The key for longevity of the system is to make sure you use a vacuum pickup to keep the chips out of the leadscrews.

I use AutoCad or the clone DraftSight to do the part. Then run it thru the extremely straightforward and spectacularly supported SheetCam to generate the G-Code. I feed it to cheap but capable MACH3 to run the router. It's very straight forward and the process does not get in the way of the task. Often I'm making sheet metal enclosures with lots of bends in them. I route reliefs in sheetmetal to show where the bends need to be. This method works extremely well for creating sheetmetal forms that need to fit into undimensioned places like a Zero Case where there's major draw and undefined lengths. I can make radiused corners with strange changing radii and tapered sides. I start undersized and then tweak the dimensions larger and larger until I hit perfection. I do 3 or 4 evolutions quickly with the above described process.

It's also very useful to include a sheetmetal brake with the removable brake teeth for these type projects.

I use Fullerton Tool 3215 TiAlN mills - Titanium Aluminum Nitride good for dry/wax.

Keith Cress
kcress - http://www.flaminsystems.com