Manufacturing Process

[KevinCPDSI]

Dear Sir or Madam,
Good day. I have a questions regarding possible forming processes for what is essentially a flanged open sheet metal box with a raised degign (not embossed). Sounds easy right? Please keep in mind I'm a student (no this isn't homework) and it's way outside anything I'm studying (e.g. I'm clueless).

My question is... What processes would be available and most cost effective to produce said box from copper in a water tight manner?

My research thus far...

Metal Stamping - Won't work. The design in the middle protrudes way to far.

Die Casting - Not sure about this. I know the tooling costs and production sizes are pretty high, and it doesn't really seem like copper is used that much. I tried contacting some companies listed on the North American Die Casting Association website, but the ones I've talked to a.) don't use copper or b.) stopped casting copper. I found one that does brass, but I really wanted red copper.

Fabrication - I thought about fabrication, but welding copper (especially thin copper) is supposed to be a pain. This may be good for low volume? I looked into this a little and some copper welds better; e.g. deoxidized copper. I also thought about brazing. Harris 0 (phos Copper) brazing rod is supposed to match copper color relatively well. They solder gutters and leaderheads, flashing etc. but the silver solder lines would really show. I tried riveting and soldering myself, but it didn't look to hot... Also any labor costs would be high, as it's difficult to make these.

Producing in plastic and metalizing - I was interested if this was a good idea. I saw that you can use ABS and then etch it to be electroless plated or it could be vacuum metalized. I've had trouble finding information on how well the copper would adhere, e.g. if hammer strikes from nailing it to a wall would damage the copper coating. I read that this is used by the automotive industry, so it is meant for exterior applications and durability, but I'm still concerned with how durable it would be. I'm also concerned about the ABS and copper having different expansion coefficients.


Please excuse the my ignorance. This is a hobby project that I'm doing between work and school for myself, so I spend whatever time I can on it. I'll attach a quick sketch I made of what I'm looking to create.

If this is the incorrect forum, I apologize. This is my first post.

Any advice is appreciated. I thought about trying to talk to a ME professor, but I don't think they have a lot of time right now and I don't personally know one.

 

[KevinCPDSI]

Also, I forgot to mention the design is hollow in the back. I didn't see how to upload multiple files. Here is another file. I anticipated filling the void with polyurethane foam or expanded polystyrene.
Thanks!

 

[KENAT]

So you're open to copper plating?

How about cast aluminum with copper plating, not sure if this is an issue from your thermal coefficient concern.

Doesn't have to be die cast, for lower volumes/tooling cost there are alternative processes such a Rubber Plaster Molding. I've used these guys

http://www.aljcast.com/

a couple of times but there are other suppliers out there.

For external application your copper may not stay copper colored that long - though I'm sure you realize that.

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[stanweld]

It could easily be stamped if you can radius the edges on the square protrusion.

 

[KevinCPDSI]

KENAT - thanks for the idea! I'll look into that. That may be a good alternative. Maybe I'll try to find out some more information in the "Paints/Coatings Engineering" section about adhesion and thicknesses. I saw one reference to plating up to .010" thick which isn't too bad.

stanweld - I am open to radius the corners, but I was told the star in the middle is the problem. They said that there isn't enough material to draw the star up in the middle like that. They said that it could only be embossed and raised to the material thickness (.027"). I was dealing with Component Engineers and their Reverse Engineering Department. I'm a little confused though, because previously I spoke with Mr. Judson at the Precision Metalforming Association and he said it should be a viable stamping project!

 

[mfgenggear]

Kevin

based on your design . how much do you want to pay?
because the way it is designed, it will have to be milled or cast.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[KevinCPDSI]

Well honestly I'm a bit of an entrepreneur at heart (ok maybe more than a bit).

What I'd like to do is to produce a small amount to validate market viability and hammer out defects and then increase production.

So far I've been using my own money, but eventually I may seek a loan from the Small Business Administration.

The problem is that you have to do a good job, or it's not going to be viable in the market. Especially since this is a luxury or specialty item, not a necessity.

It's the whole catch-22, chicken/egg problem. Doing a good job costs a lot of money, but it's not viable if you do a shoddy job.

I'm not sure if that answers your question though. Did you want a specific number? I've saved $1000 specifically for this project so far, after Christmas maybe $1200 . Anything much above that I would have to be really convinced and go to the SBA for a loan. I know die casting and stamping can range 50k+

 

[mfgenggear]

Kevin

being it's copper, milling will be easy. get a quote for each process.
then decide.

milling will be a viable method for low volume.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[SnTMan]

What they'd have probably done in the old days, before machine tools, is to carve a negative out of wood and hammered copper sheet into it. The given design would likely need "softened", few sharp corners, if any. Maybe a few annealing steps. One thing about the old days is that they designed around what they could make. Of course, the scrap mostly didn't survive as artifacts

I'm surprised it won't stamp, not that I know anything about that. Offshore the manufacturing to reduce cost?

It really all depends on the quantity and accuracy needed.

Regards,

Mike

 

[mfgenggear]

Based on the sharp corners and the difference in thickness, it will probable will tear.
but ya, I try to press one one, except no guaranty it will work. then the tooling cost involved.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[patprimmer]

I suspect it could be done by electro deposition.

http://www.bjsco.com/services-EF.php?ID=16

There was a company in Loddon England.Yes Loddon not London that did it, but I lost contact 20 years ago. I may have their literature buried somewhere.

There was also one somewhere in Canada. Webester seems to ring a very old rusty bell.

Electrodeposited moulds are used in high volume FRP work or where a very accurate reproduction of an existing surface is required, like taking leather grain directly off a piece of leather.

Regards
Pat
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[telecomguy]

I'm going to go with stamping. This reminds me of the old ceiling tiles that were stamped or possibly hand formed as Mike mentioned above. But you may have to be open to some thickness variation, especially in the corners where your side flanges fold up to make 90deg corners. Or these could be a secondary forming operation and soldered.

 

[berkshire]

Kevin
I have made pieces like that, part of your problem, is that a formed sheet metal piece does not look like you have drawn it. A minimum radius inside corner will have an outside radius of at least the thickness of the metal, if you want sharper you get into very expensive coining dies, or V grooving the back side of the part to make a sharper radius. If you can accept the outside radius of a formed part, this can be done by stamping with multiple dies, and annealing between each forming operation. If you cannot, then you get into the machining, and electro deposition methods others have mentioned.
If you soften up the edges and get rid of some of the sharper corners, you can do this with a single male die into a hard rubber block by the Guérin rubber-forming process , or by hydroforming, if you start with an annealed sheet.
This is a common process for architectural sheet metal embossed pieces on older buildings.
Another way of fabricating this piece, is to make the " star" separately, add tabs to its underside, then use a technique called sweating to join it to your plate, any surplus solder is cleaned off by scraping and polishing to give a pure copper appearance.
A thicker copper sheet than the 20oz you have specified will also help, but of course will give you bigger corner radii.
B.E.

Here is a link to copper thicknesses and weights per square foot :

http://www.copper.org/applications/architecture/arch_dhb/fundamentals/dimensions.html

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[TVP]

If conventional metal stamping won't work, then sheet hydroforming is another possibility. Here are two potential vendors that have reasonable process descriptions on their websites:

http://www.helandermetal.com/hydroforming-services.html

http://www.jmpforming.com/hydroforming/index.htm

 

[KENAT]

Not sure if you can superplastically form Copper, you can Al though.

http://en.wikipedia.org/wiki/Superplastic_forming

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[KevinCPDSI]

All,

Thanks for all the input! I really appreciate your advice.

Some things I wanted to clarify:

The corner radii can be changed. The only reason they are square is because I did the Jpeg in Google Sketchup real quick.

Berkshire - Maybe the reason I was told it couldn't be stamped is because it needs compound stamping. I'm not sure. I hadn't looked at the Guérin rubber-forming process, that's cool. I'll look into that. I've actually looked at hydroforming, but that won't work for a piece this big (unless I can find a company with a machine that big). I thought about soldering it together like you said. Really for that, you might as well have the whole thing soldered, corners and all. The pan can be formed with a sheet metal brake. The problem with that is I wasn't sure how well it would turn out looking. A lot of the really good shops actually weld the copper too. I was trying to avoid this, but maybe that's the way to go. You should check out

http://www.hanscopper.com/

if you want to be amazed by a copper artisan.

TVP - Thanks. I've actually talked to JMP before and a couple other hydroforming companies. The diagonals were too big for them to handle. JMP has a 32" bed. I found a company in San Diego with a bed big enough, but they said they don't form copper.

Kenat - Thanks! Yes, I read an article that says that copper can be superplastically formed. It says, "The results demonstrate that as-casting QAl10-3-1.5 copper alloy shows good superplasticity without prior-treatment. The maximum elongation of 545% is obtained at 790◦C and initial strain rate of 1.0×10-2 s-1, while the maximum flow stress is only 12.4MPa." (

http://www.scientific.net/MSF.551-552.)

I'm going to look into all the options.

I really appreciate all your advice.

 

[KENAT]

Off topic but for external use, is theft a problem?

thread765-334356

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[berkshire]

KevinCPDSI,
Have you checked out
Hydroform Usa
2848 East 208th Street Carson, 90810., They had done some copper work about 10 years ago.They also had a Verson Wheeler machine with a 4' x10' bed.
If you are in the San Diego area, you could check also with Ehmcke sheet metal corp in National city. They specialise in architectural sheet metal and used to make embossed panels for some banking institutions. They also are quite expert at welding copper so you cannot see where it is joined .
For what you are doing, or trying to do, Hans does not have the equipment to stamp, he can only form on a handbrake, weld and solder.
I used to work for him as a contractor in 1999 making leader heads so I know what he has, he purchases the stampings.
B.E.

"A free people ought not only be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government."
-George Washington, President of the United States----

 

[MikeHalloran]

Like SnTman said.
Buy some copper sheet and learn to repousse', in person, yourself.

OR, if you really want to mass produce it, a part that large and that thin, in copper, will hydroform at pretty low pressure, so you could do it with wooden tooling in a frame made of steel channels or some such.



Mike Halloran
Pembroke Pines, FL, USA

 

[mfgenggear]

actually if the radius are increased at the corners, then the Guérin rubber-forming process as stated by berkshire to my opionion would be the cheapest & fastest method. the out side perimeter would have to be trimmed. Hydro forming could do but more expensive tooling cost.

I never formed copper, & depending if alloyed or pure. pure copper would & should be easy.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.