Advice on making a forming die to bend flanges on aluminum sheet?

Needing to make about an 8 x 8" end cap with flanges of about 1/2" with 0.027 aluminum coil stock. Some of the corners are right angles so I can just notch the corners but would like to have a bit of cover over the mating part so thought I would leave 1/8 -1/4 that will need to form a compound curve - needs to compress and some minor wrinkling is ok. Notching the corners most of the way will hopefully minimize this issue. Some of the edges are curves so some stretching/compression will happen.

Also going to make a die to punch out the shape with flanges from flat sheet. That seems pretty straightforward.

For the forming operation I am thinking about how to hold the part. If I put the pocket in the lower die I can cut the outline of the part in the top of it for initial placement. But when the upper form comes down he part may shift. Seems like I need to clamp the center portion somehow. I have some ideas about this but all are fairly complex. Any suggestions on this?

Two of the edges are straight and parallel so I suppose I could do those edges first and then clamp them somehow to do the other edges but the corners where some compression will happen in the flanges is an issue. Looking for ideas/suggestions...

Can you post a picture of what you want to do. Almost sounds like you need a compound die, or make some roto-bend tools.

I can post some pictures later - don't have any handy right now. But it is an end cap for a large commercial size roof gutter. Standard ends fit inside the gutter and I want one that goes outside. Smaller sizes are thinner material and have a double bend forming a goove near the edge and have some wrinkling. Budget is very limited so wanting to try to do this myself. Have any examples of roto-bend tools?

Know your bending basics—Part II - The Fabricator

There is a couple of ways of doing it, the above article should point you in the right direction. What I called a roto-bender above is actually a Ready-Bender.

Seems a bit like using a brake for the bends. A bit harder for the curved lines but the real issue as I see it is how to handle the right angles where I want a little flange on the corner.

If by flange you mean something like this:

http://www.cnczone.com/forums/attach...d=379606&stc=1

Normally you would make the short bend first, then would make the long bend. It is possible to do both in a single station, but increases the die complexity.

No. Just a single bend but on multiple edges.
Here are pictures of something very similar to what I want to do. I am not sure how it is formed.

Attachment 379644
Attachment 379646

Here I have shaded a corner where I could remove material to minimize material wrinkling at the corner. I only plan to remove it for about half the width of the flange.

Attachment 379648

Looks like that was done in a drawing die. Basically shoved into a die in the same orientation as your second picture.

But this might be useful http://<a href="https://www.youtube....w5yEMsDxR8</a>

Quote:

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Originally Posted by Jim Dawson

Looks like that was done in a drawing die. Basically shoved into a die in the same orientation as your second picture.

But this might be useful http://<a href="https://www.youtube....w5yEMsDxR8</a>

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Interesting. I was involved in building/flying homebuilt airplanes earlier in my life - my Dad was very involved in it... But they avoid the issues I am concerned about by notching around the curve so there is almost no metal stretching/shrinking. Here's an interesting one I found after you pointed me in that direction.

https://www.youtube.com/watch?v=RhG8gISbWMA

It uses 1000 Bar pressure though (about 15,000 PSI if I converted correctly)!

The cutoff of the flange isn't straight on the example part which leads me to think the outline is cut out first and then it is formed. Or perhaps it is partly formed and then cut off and then the flange is bent the remainder of the way.

It takes a lot of press to do that, but the part sure came out nice. The upside is that the tooling to make the part is easy to make and inexpensive. If you wanted to build a press, it looks like the operation could be done in the home shop. Since your part is only about 8 inches square and about half the thickness of the 1.5mm part in the video, a bit smaller press would suffice. It is something I would try in my shop if I needed to make something like that.

Another method to concider.

https://www.youtube.com/watch?v=tm9VZhjndKI

Quote:

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Originally Posted by Jim Dawson

It takes a lot of press to do that, but the part sure came out nice. The upside is that the tooling to make the part is easy to make and inexpensive. If you wanted to build a press, it looks like the operation could be done in the home shop. Since your part is only about 8 inches square and about half the thickness of the 1.5mm part in the video, a bit smaller press would suffice. It is something I would try in my shop if I needed to make something like that.

Another method to concider.

https://www.youtube.com/watch?v=tm9VZhjndKI

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If you did it are you suggesting the method I posted by Quintus? I suspect a lot of the force is needed to sheer off the bottom scrap part. You say the tooling is easy to make - how is the gap between the die and the outside, hardwood part determined? Or would you use some other method?

The explosive forming is definitely interesting.

BTW, I was just in the Portland area visiting family for Thanksgiving. I grew up out there but moved to the midwest after college.

Yes, the method described by Quintus. The tooling is just the profile so should be simple to make. As far as the gap... I have no idea how to calculate that. I assume there might be some general formula based on the depth of the flange. If I had the time I would do some experiments to see what works, looks like fun stuff. The only die work I have done was all done for stamping presses so these other metal forming techniques are new to me. I'm learning along with you. :)

Would you try to include the cutoff of the scrap used to pull down the flange or do that as a second operation? Seems like that would take a lot more pressure than forming but I could be wrong. When I started this I was considering a conventional male/female die set. One issue I see is how to hold the part in position - the example has holes for pins but my part is solid. Perhaps I could extend the part taller for some positioning pins and trim that off after forming. Since it is in compression I could make both forms out of hardwood for initial testing I think.

I think it would take immense pressure to cut off, not so much for forming.

I think you could make your part with a more conventional male/female die. The bending forces are pretty evenly dispersed around the edge so with some luck it might self-center, or at least stay put in the process. The die clearances would have to be essentially 0 with the part in there, maybe a couple thou clearance. If you can bottom out the die hard, the material might stretch/shrink enough to give you a nice form with 90° bends that stay put without over bending.

I'm just fascinated that a piece of rubber can flow around the part and form like in the videos. Maybe some tabs located in the right place would hold the part, then those could be trimmed off later. Hardwood might work fine, but aluminum might be less costly. Hardwood is pretty expensive. The downside of aluminum is that is is sticky and would gall pretty easily. An aluminum part and an aluminum die might be a bad idea. Maybe some Never-Seize would work as a lube. Mild steel might make a cheap and easy die, and not much harder to machine than aluminum.

I'm just kind of rambling here. Just throwing out some general ideas because I don't have a solid solution for your question. If I were going to do this in a production setting, I would build a really expensive progressive die, run it in a 100 ton stamping press, and crank out 1000's of pieces per day. :) At this point, I would pick a direction and give something a try. If you can do it inexpensively, then not much resources have been lost if it doesn't work. Maybe trying a less complex shape first would give you a feel for how it all might work.

I have some scraps of hardwood so I might use that at least for tests. I plan to make a test part about 2" square to try out some things - much less time and material invested until I figure out what works. Thanks for all the ideas and such.

I want to add a flange as a stiffener across the other side that doesn't quite go to the corners so I could put that on the piece first with a brake and hold it with that. I was trying to figure out how to clamp the center of the part and have the rest of the die come down around it but it makes it much more complex.

What milling tool is used to form the radius at the top of the die? For wood there are bits with the convex profile but I haven't seen many for metal. Is this done with many passes of a ball end mill? A custom ground cutter?

You can use corner rounding endmills, they come in all sizes. Or just use a carbide tipped wood router roundover bit, yes they work just fine in steel.