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]

Kenat - Theft will not be a problem. The flanges sit beneath lap siding and are nailed in. If they steal this they might as well steal something out of your house.

Berkshire - That's awesome! Leader heads are crazy to me. I can sweat copper and have put in a ton of 3/4" and 1/2" pipe, but nothing beyond that. I kind of wanted to learn, but the flat iron torch and all costs about $600. Then you have to practice for years to be good I would think. I'll probably check with a copper shop (not Hans I think he's really pricey) and see how much to hand brake and solder just one. That way I have a prototype in hand.

MikeHalloran - Haha, so actually that was my first idea for the prototype too Mike... I should post my repousse, it would give you a good laugh.

 

[KevinCPDSI]

I figured I'd update you guys.

Thank you again for all your help! I really learned a lot and I appreciate all your advice.


I ended up contacting an architectural copper shop like Berkshire was talking about. They're going to look at it and either solder or weld it. This was the cheapest way to prototype it and it will give me an idea of the cost to produce it this way. I think it's probably the cheapest way to product small amounts of them as well.

If small amounts go well I can look into some of the options above.

I'll take a picture of the piece after it's produced and post it on here so you guys can take a look.


Once again, thank you!

P.S.- Now I have to do tons of school work. I may have been slacking off a bit... I probably won't be able to check this for a bit.

 

[KevinCPDSI]

I said I'd post a pic, so here it is!

 

[MintJulep]

Looks pretty good.

Does the cross have to be open to the "inside"?

 

[KevinCPDSI]

MintJulep,

I'd actually rather it wasn't, but with them fabricating it they have to.

I had considered that in the future the "face" could be stamped and then fabricated onto the box/flange, however then I'd run into all the really expensive tooling for stamping etc.

The company I had fabricate it does all sorts of architectural finials, leader heads, etc. so it's waterproof. There's a lot of solder in the "inside" of it.

 

[MintJulep]

"but with them fabricating it they have to."

I don't see why.

The cross can be made from four bent pieces, then just sit on the flat bottom plate - without a cutout. Should be easier to make that way.

 

[KevinCPDSI]

MintJulep,

Thanks for the reply!

I think the problem with that is that you have to have large solder lines (e.g. 1" with common roofing irons) in addition to the bent pieces. That would make the front look unattractive.

Additional options would be to rivet it to the front or a combination of riveting and soldering.

I think the reason it is done this way is that the solder lines are very small and barely visible while still being waterproof.

 

[1gibson]

They couldn't form the cross out of one sheet, with small flanged edges? Cutout of the flat sheet that is sized for the base of the cross, drop it from the back side and seal the edges (capillary action would assist) then clean up seam from the front side if necessary. The way I imagine it going, you would not have much of the solder coming through on the front.

 

[KevinCPDSI]

1gibson,

I may be confused.

They did drop the star (cross) in the flat sheet form the back and then solder the back tabs.

The star (cross) can't be one piece, the shape won't allow it.

 

[1gibson]

Ok, I see, that is what I was describing. Might get cleaner results if soldered in vertical position instead of face down? I am assuming here that it was done face down based on some of the "drips" at the corners.

I can understand not being able to form that cross into the flat sheet, but would think the geometry is ok to form that cross as one piece, then drop into the flat sheet.

I actually just had surprising success making the cross shape by cutting/folding one piece of a post-it note, so I am pretty sure it can be done in copper sheet. Maybe some minor changes to reduce height or increase base size, but I don't buy that "the shape won't allow it."

 

[KevinCPDSI]

1gibson,

I think you're right. I let them come up with the dimensions for the stare. It makes sense that with changes to the base and height it could be one piece. That's a really, really good point! I appreciate your help.

 

[1gibson]

No problem. Try it yourself, draw it on graph paper so it is symmetrical, then fold it to make sure it works, then give them approximate dimensions. I think there are also free 3d paper modeling websites that you could use and get exact dimensions.

This might be beyond that particular shop's capabilities (maybe they can only form 1 bend per sheet?) but of course see all previous replies with respect to forming processes.

 

[berkshire]

Kevin I am coming late to the party here, The prototype does not look bad, except for the soldering.
The Journeyman needed to have scraped off the excess solder and cleaned the surfaces. There may have been financial considerations there, because that is a time consuming process.
You should have no problem getting that shape hydroformed using a dead soft copper sheet.
B.E.