I've hit a prototype wall

Hi all,
I have an invention I am attempting to make a prototype of and it is ALMOST done, but, I cant get one part made and would like your opinions.
[ATTACH=CONFIG]829[/ATTACH]
As you can see from the photo, the item is a double curved 16 gauge sheet metal section approximately 5" in diameter. I have brought it to a sheet metal shop and was basically told it would cost me an arm and a leg to make 1, let alone all 4.

I started thinking maybe I could find some 90 degree elbow of some sort and cut it to that shape. Any ideas?

Welcome to EE!

[QUOTE=moegilla;7848]Hi all,
I have an invention I am attempting to make a prototype of and it is ALMOST done, but, I cant get one part made and would like your opinions.
[ATTACH=CONFIG]829[/ATTACH]
As you can see from the photo, the item is a double curved 16 gauge sheet metal section approximately 5" in diameter. I have brought it to a sheet metal shop and was basically told it would cost me an arm and a leg to make 1, let alone all 4.

I started thinking maybe I could find some 90 degree elbow of some sort and cut it to that shape. Any ideas?[/QUOTE]

Define "arm and a leg" = $$..

Also, how many different quotes did get?

I was "no quote"ed twice and told 250$ or more each by the one shop that would talk to me.

$250 each for one or two pieces doesn't strike me as unusually high. You might save some money if you would be willing to make it out of a multiple flat segments, maybe bent or welded. If you do get into higher production levels you could afford to invest in tooling which would bring the per piece price way down.

The price could be perfectly fine, I just dont have 1000$ to spend on prototyping anything right now(mortgage, children to feed etc...) I was trying to find some way to get a very rough prototype going for proof of concept before shelling that out. I do not have any sheet metal forming tools with the exception of a pair of snippers, and no welding equipment.

I'd like to try a few more things before giving in and spending the money.

[QUOTE=moegilla;7852]The price could be perfectly fine, I just dont have 1000$ to spend on prototyping anything right now(mortgage, children to feed etc...) I was trying to find some way to get a very rough prototype going for proof of concept before shelling that out. I do not have any sheet metal forming tools with the exception of a pair of snippers, and no welding equipment.

I'd like to try a few more things before giving in and spending the money.[/QUOTE]

Ok, so how accurate does this geometry need to be? Can you hammer it out yourself?

[QUOTE=moegilla;7848]I started thinking maybe I could find some 90 degree elbow of some sort and cut it to that shape. Any ideas?[/QUOTE]
Like you said, I think your best bet is to find something ready made and cut it to shape, such as 90º ducting joint.

It's not quite the gauge you are looking for, but using a quick google search, I've found some [URL="http://www.ductincorporated.com/elbows.html"]here[/URL]. I'm not sure what the radius of your 90º bend is, but there are a few options. You could probably cut it with some large tin snips or an electric saw. If the radius or section diameter isn't quite right, some cuts and bends in the right places will get you close to what you want.

It's possible make it out of one single sheet, or welded out of multiple sheets but it takes time and skill, and the quotes you have been getting reflect that.

Can you cut it out of a standard HVAC elbow?

Just a couple hints....

Using your favorite internet search engine, check out the following:

5" exhaust elbow
5" conduit elbow

Find one of the appropriate bend radius, lay it flat on the table, mark a cut line along the center line of the tubing, flip it over and repeat.

Using appropriate safety apparel (gloves, face/eye protection) use a 1/4" die grinder with a 3" diameter, 1/16" thick cutoff wheel and cut along the lines you just marked.

Deburr the edges and call it a day.


Ron

Edit: more thinking.... Check with a shop that builds and installs exhaust systems in heavy, over-the-road trucks. They may have some sections of tubing already bent to size that you could cut as required. Heck, if you ask them nicely and provide some liquid refreshment, they may even bend and cut the pieces you need.

Unless I am mistaken, you can purchase a 5 inch 90° sweep from an electrical supply company, cut it in half and you will be home free. It might cost you 20bucks, but I doubt it will be that much

Could you make it from fibreglass?

Why don't you have it 3dprinted in Aluminum?
It's come on a long way now. Depending on the thickness it may work.

[QUOTE=redled123;7993]Unless I am mistaken, you can purchase a 5 inch 90° sweep from an electrical supply company, cut it in half and you will be home free. It might cost you 20bucks, but I doubt it will be that much[/QUOTE]
That's what i would do, unless your tolerances are critical.