Seeking Advice On Sheet Metal Stamping 1

[JanusCole]

Hello,

I produce rear end deck lids for Porsche 911's in my basement workshop using traditional hammer forming techniques. I do them in aluminum since OEM parts in aluminum are NLA and so owners are willing to pay a premium. That said, each part takes a lot of time and may ability to add new parts to my product line is extremely limited (it can take months to build a proper hammer form). So I'd like to have the parts stamped in aluminum instead. Now to be perfectly honest, deck lids aren't incredibly complicated parts (see attached picture). There is a top exterior piece and a bottom structural piece and that is pretty much it. No complicated features or curves. And yet, I have approached a couple of shops that claim to do metal stamping and they all say that the tooling would be prohibitively expensive and difficult. Of course, they won't give me any ball park figures or explain why it would be so difficult. So I am baffled.

Now, I am accustomed to doing this stuff by hand in my workshop. So I know little about having manufacturing done for me. Can anyone give me some advice or point me to a place where I can learn how this is all done? I assumed I'd just have someone scan the top and bottom sides with a laser scanner into a CAD file and then I'd pay someone to cut a die. Then, presumably, I'd just have someone else do the stamping in aluminum. What am I missing here? Can anyone give me a ball park figure of what it might cost? I am encountering roadblocks at every turn and it is very frustrating.

Thanks,

-Janus Cole

 

[patprimmer]

Your link is password protected, so I cannot see the part, but I am reasonably familiar with 911s. Some early ones are fairly simple, but later ones are very complex with whale tails that hold A/C condensers etc.

Maybe the guys blow you off because you present like you have no idea of the costs, or because they presume you can't afford or justify it. If so, their fault, but you might do better if you play there game and dress the part when you visit.

A wild thought, is the OEM stamping die available, maybe as scrap.

I know nothing of stamping dies, but I do know something of plastics injection moulding moulds. The plastics moulds will be more complex, but would cost several tens of thousands of dollars. Just the steel would be thousands of dollars.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[JanusCole]

Thanks for the advice. It is genuinely appreciated. I didn't know that the picture would be password protected so I have uploaded a jpg. The ones I make are replicas of the original AL deck lid with no spoilers of any kind. Very simple stuff.

If startup costs were in the tens of thousands, then frankly, that would be okay. A halfway decent 30 yr old OEM 911 deck lid in AL goes for about $1,000 - $1,500 each - and AL hoods or duck tails would go for much more - if anybody made them. So I'm just amazed they aren't even willing to talk to me. I can recoup tooling costs pretty quickly...even substantial tooling costs.

Oddly enough, a friend in the garment industry tells me he had a similar problem until he moved his manufacturing overseas. He said American companies were routinely dismissive and rude. But when he went to India, he got a completely different attitude. I'd rather stay domestic. But I'll go overseas if I have no other choice. I just today emailed about 20 companies in India. We'll see what they say.

As for acquiring the original dies, I believe they were bought by a US company that specializes in steel reproductions. So I am out of luck there.

 

[patprimmer]

My advice is to seek alternate supply, in USA, China and possibly Australia. China, like USA normally only like long run production. Australia specialises in short run production and has a high ratio of skilled people in the workforce like other developed countries. Our $ is strong, so costs will he high.

The same guys who were arrogant to you will be the first to complain when challenged by imports.

You will also have an export market for your product. I can fix you up with people here who know that market.



Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MikeHalloran]

Stamping dies are different from injection molding dies because metal is not always plastic. Okay, duh, but bear with me.

An injection molded plastic part is, allowing for shrinkage, a geometric complement of the cavity that made it, so you can make an acceptable mold for a plastic reproduction from a cast of the finished part.

Not so for metal, which has to be overbent, working it along the stress/strain curve, which just for fun is different for steel and aluminum, and for different heats of each. Stamping dies bear only a passing resemblance to the finished part geometry, and there may be more than one pair of dies involved in progressively refining the shape from flat to whatever.

Metal also presents as sheet, not meltable pellets. The dies have to draw the metal from the blank into their cavity. In the process, the metal rubs, hard, on the die surface, possibly scarring the metal and eventually wearing the die.

Wait; it gets worse. The metal often wrinkles as it's drawn, so the dies may contain odd features to control the wrinkling, or to induce it to occur in a portion of the workpiece that will later be removed.

For exammple, I think the "SME Die Design Handbook" carries a photo of an old Ford rear roof section, mid- process, with a big ugly wrinkle right in the middle of it... where a hole would later be punched for the rear window.

That book would be a good investment for you.



Mike Halloran
Pembroke Pines, FL, USA

 

[EdDanzer]

One place to start is

http://www.mfgquote.com.

You will have better luck if you have one company digitize the part so other shops can import the data for modeling. You will need NDA’s for anyone who works on the project. As MikeHalloran mentioned spring back needs to be allowed for in the die shape and there is software to help get it right the first time. It may be advantageous to know if the shop has advanced modeling software to determine actual die shape.

As with any new expensive project many shops will be wary of spending a lot of time quoting a project like this. If you find a few places with actual capabilities and ask for a ball park range after supplying a digitized model and what they need as a down payment to get started you will be better received.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[GregLocock]

Concur on the sticker shock.

Aston Martin or Lotus would be the obvious people with expertise with low volume tooling. I think for aluminium you could use a soft form tool, in which the male part is a rubber block. I don't know what the quality would be like.

To be honest I think you are barking up the wrong tree, steel dies are designed for 20000 parts (or more) per annum, and need enormous presses.

Howver, if you /do/ find a method that works there are a lot of car companies that would be interested, prototyping is a lucrative if challenging business.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[JanusCole]

Thanks very much! This info is incredibly helpful. I clearly came to the right place. I can't thank you enough. I am quite familiar with the traditional metal forming with hammer form and hand held hammers. But taking the leap to automation has proved a daunting task.

PATPRIMMER WROTE: The same guys who were arrogant to you will be the first to complain when challenged by imports.

Funny you should mention this because I got the following email today...I don't think I have ever called a client a "crybaby" at any point in my entire career...I replied to him saying he had done me the favor of removing his company from my list of prospects...

And to establish the context, he is correct that I didn't include size measurements - however I did include a PHOTOGRAPH of the part in question clearly showing the size...

Amazing...will I need to beg US metal working companies to even talk to me?

-Janus Cole

--- On Sat, 7/5/08, John Baker wrote:

From: John Baker
Subject: RE: Contact Us Form for General A&E
To: JanusCole
Date: Saturday, July 5, 2008, 4:44 PM

Don't be a cry baby.

Consider other alternatives. You haven't even said how big the lids are. If they're bigger than a foot in either direction then of course tooling would be prohibitive. You should look at other ways of manufacturing it that specialize in larger items. Why not consider hyroforming or vacuum forming. Cheaper tooling, slightly higher unit price. The Internet should make your work easy.

 

[GregLocock]

John must be my twin brother, that's one reason I don't work in sales!

Hydroforming is an interesting suggestion - I haven't seen it suggested for a body panel.

What sort of quantites were you thinking of?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

Hydroforming is an excellent suggestion for the parts in question. It can do the large radius forming and the small radius drawing, in one step.

If a low production rate can be tolerated, the tooling can be relatively inexpensive, e.g. stacked plates bolted together instead of an actual press. It might be possible to do both the shell and the reinforcement in one inflation cycle.



Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Mike do you think you'd get a Class 1 finish?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[JanusCole]

Yes, excellent point. I will begin obsessively googling "hydroforming" to learn as much as I can. I did actually take the content of Mr Baker's email seriously. It was just his introduction that I didn't like so much.

Thanks,

-Janus Cole

 

[BrianPetersen]

Hydroforming as I know it is incredibly expensive. The process as I know it consists of taking a pre-formed (generally steel) tube, placing it in what amounts to a mold, then essentially "inflating" the inside of it with high pressure liquid, forcing the tube to shape itself to the inside of the mold. It's used for frame members and similar tubular parts. The equipment to do this costs millions and it's only practical / cost effective for parts produced in the hundreds of thousands (e.g. GMT900 frame members).

Vacuum forming, or possibly something like it (with a little more pressure from the open side of the mold, perhaps) might be what some people really mean. Vacuum forming as I know it is used for thermoplastic parts. You take a thermoplastic flat sheet, heat it up uniformly so that it is soft but not melted, place it over a mold that has many openings to allow vacuum to be applied underneath it, and suck the sheet into the shape of the mold. It's limited to parts for which a flat sheet can seal against the outside of the mold - otherwise, the vacuum just leaks in from around the edges. Of course, if this is not convenient for the finished part, it's possible to make the part bigger than necessary so that it *does* satisfy this limitation, then trim it to suit. I've never seen this done with metal, but that doesn't mean it's impossible. Controlling wrinkles could be an interesting challenge. With softened thermoplastic, this is not a problem.

 

[GregLocock]

We use hydroforming for prototyping and production, maybe there are similar but different techniques with the same name. Lotus were certainly interested in it for low volume production, as I remember Matra use it as well.

However those are all for tubular constructions more than external panels, hence my question to Mike.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

Long before anybody thought to hydroform a tube into a usefully distorted shape, people were selling and using hydroform presses, principally for making aircraft parts of aluminum. In those, a rubber blanket is forced, by means of pressurized hydraulic fluid behind it, against a flat blank which is partially supported by the male tool behind it. The tool takes the form of, say, profiles for a whole set of wing ribs. Given a urethane blanket and some sharp edges in the tool, it was possible to also cut out relief holes and edges.

Free-form hydroforming is also possible, as in welding up the edges of two suitably pre-shaped blanks, and inflating two boat hulls, just by pumping oil into the space between the blanks. Essentially no tooling cost, but limited control over the finished article shape.

I was thinking in terms of a traditional blanket type hydroforming press, except without the press, and doubled up with two blankets and two workpieces sandwiched between two platens with simple tools affixed.



Mike Halloran
Pembroke Pines, FL, USA

 

[carnage1]

If you are going to hydroform I suggest explosive forming. from a practical standpoint there would be less cost for the explosives than for pump equipment for small runs, and more importantly explosions are cool

the biggest benefit I see is the need for only one Die.

 

[NickE]

For the kind of quatities it seems you are talking about, a kirksite tool in a simple press would work.

Have you tried talking to prototype sheet houses out of detroit? Business is kinda slow here, most places seem to need some work.

http://www.thomasnet.com/products/stampings-short-run-79140208-1.html

I can honestly say that I've been to these three: Matrix, Oakley, and Quasar, seemed like good shops.


Nick

 

[GregLocock]

Do any of these single step processes get a class 1 finish?



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

They probably produce an A1 finish with less finishing work than free form hand beating.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[EdDanzer]

I think explosive hydro-forming will provide a finish equal to the die. The explosion will have to provide enough energy to exceed the yield strength of the material as it work-hardens during the deforming process and enough volume to fill the deformed shape. The die and backer need to be structurally strong enough to take the pressure which should be over 16,000 psi (the yield strength of 0 grade 5052 aluminum.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com