Help with Bending Forces for 3mm (1/8") Copper Sheet

The forces are different, depending on your design.

Where you clamp it.

How big of a bending radius is allowed.

If it is for one piece, a bench vise, some wood and a heavy hammer does it. If it is for mass production consider a press with a cutting and forming caliper in one move.

If designed well there is enough stretch in your material.

And it will not leak if you press a box.

It can work with a combination caliper, or with ejector or opening anvil. You can have it made too, but if you want to do it yourself, prototypes are often hand made.

If you have access to a slinger press, a garage press or a hydraulic press, you can make yourself a solid V- block.

The angle should be slightly less than 90 degrees. Make it 86 degrees.

You can use that as an anvil and fix it solid under the press.

On your plunger you need a little steel block that fits into the opening of your box. This should have a wedge below, a V also, that can go down into the V- block. The angle should be about 82- 84 degrees. Give it some height too.

Line everything out well and fix the V block properly. Once you place the copper plate on the anvil, you bring the plunger down straight on the line and push it downwards into the V- groove block. Make your piece shorter, because the bend will save some copper. It will work easy when your press is 1 ton (metric) or more.

The dept will determine you end angle. The material will make the angle bounce back a little, that is why 90 degrees is not sharp enough. If you have groove marks, adjust the edges with a fine file or sandpaper. You can also apply some grease, oil or petroleum on the copper to smoothen it out.

Make sure the plunger is guided and cannot rotate. Keep your fingers away while pressing.

When you make a box, calculate with the inside measurements. Good luck.

Find a local sheet metal shop with a press brake. they will have the equipment and expertise to fabricate your prototypes.

I am most grateful to dvmdsc and others for their advice,

The difficulty we have is that whilst my description was "box –like" the folds are not parallel. All four folds converge at a single point requiring the anvil as suggested by dvmdsc to be diamond shaped. Thus it is my understanding that the part cannot be folded on a normal break-press, even one with removable/adjustable fingers?

I had forgotten about the sheet material having a memory and relaxing after bending and the advice regarding using the internal measurements was also most helpful.

I am currently exploring a simple bench press typically 3 – 10 tonne capacity but I am slightly hesitant over the support for the bottom anvil which because of its diamond-like shape cannot be supported directly under the centre-line of the load.

Any other advice would be most welcome.

Thank you once again.

Christopher

If you want to press it in one time, your 10 tons will be sharp. How big is your ton? (1000 kg?)

But pressing it in one move is the best for you. It is quite simple.

A sketch of the part would be quite helpfull, I can't quite visualize it from your description. I have some 40 years experience building and design press tooling, so once I have a better idea of what you are trying to make, I may be able to give you some ideas.

Thank you gringogreg for your kind offer of help which is greatly appreciated.

I will model the component in AutoCAD this evening but I am not sure how I introduce the drawing onto the thread; can anyone give me so advice on the correct format etc., please?

I apologise for being quite so naïve as to how the forum works.

Thank you all,

Christopher

Good morning all,

I have appended below 3 simple sketches of a somewhat simplified version of the 3mm thickness copper plate I am trying to bend. Any further advice would be greatly appreciated.

Thank you all.

Christopher

Simplified view of anvil arrangement.

Anvil with simplified folded component.

Simplified template of 3mm copper sheet before bending.

Is the base square or triangle? You show both.

You don't need such a complex template, but depending on the variation in thickness you allow, a caliper that stretches or crimps or do both.

Your "RAW" stock will be almost a triangle or a square.

When you stretch, your material becomes thinner. If that is not allowed, corrections need to be made to let the material "flow".

You remember steel corners for flight cases? They are also made in one move.

Just don't even think of bending per line.

Bending force and bending radius depend on width of prism:

At prism width W = 16 mm, force per 100 mm of bend F = 2500 kg, internal radius R = 2.0 mm.

At W = 20 mm, F = 1800 kg, R = 2.5 mm.

At W = 24 mm, F = 1400 kg, R = 3.5 mm.

Dear Efim,

Thank you for your most informative reply.

There's just one problem, can you please define "prism?"

Are you also able to expand on the information you have kindly supplied, namely are these properties just for half-hard copper?

Thank you so much.

Christopher

Prism is lower tool (Die)

Dear Efim,

Thank you for the concise clarification.

Can you please advise whether the values you kindly supplied relate just to C106 copper and is there anywhere where I might find such values in the future.

Finally, is there a problem in the fact that my prism is the upper section of my anvil arrangement.

I have concluded, that to enable me to rotate my part as it is folded I cannot have the prism at the bottom?

Thank you once again.

Christopher

Forces and radii are given for a material with ultimate stress 290 MPa (e.g. C11000-H02). C11000-H04 has bigger strength and may crack at bending.

More convenient to put a blanck (flat pattern) on a prism when prism is lower tool. The bending angle shall be adjusted by strock of upper tool (punch).

Dear Efim,

Thank you.

Christopher

Hi Christopher,

I'm home from work now. I had a chance to look over your sketches and I have some ideas that will make this a lot simpler than you thought. You should be able to form your part using only two tools, and they can be very cheaply constructed, at least for the first trials. Unfortunately, I don't have SolidWorks or AutoCad on this computer, so I will have to give you descriptions in words. Tomorrow, I will try to send you some sketches if I can figure out how to do this. I have never tried up until now.

First, to simplify things, I want to modify your blank layout slightly. Change the 47.57 dimension to 50 mm so that each face is an equilateral triangle. This will give you a 45 degree pyramid or one half of an Octahedron (I like the symmetry). Now, if you have not already done so, layout your blank on paper, including the fold lines, and cut it out. Lay the blank with the two half faces on the bottom and label each face, in a clockwise direction, starting with the left half face: A B C D E. These will be the inside faces of your pyramid.

You will note that the fold lines AB and CD are in a straight line (the reason for changing your blank dimensions). Now, keeping faces B, C, and D flat on the table, fold faces A and E up to 60 degrees. This will be tool #1.

Next, keeping face C flat on the table, fold faces BC and CD up to 60 degrees until the edges of A and E meet and tape the two edges together. You now have your pyramid! This will be tool #2. Note that because of the geometry that I have specified, that the angle between faces C and AE is 90 degrees. Can you see how the two tools will work?

Now let's do the same thing with your 3mm copper blank. The nice thing is that all of the bends will be 60 degrees, therefor you do not need much of a bend radius to avoid cracking, 1mm should be enough, and the bending forces necessary will be reasonable.

The first bend is easy, you could do this in a press brake, a box brake or with a simple V die, or even in a bench vise. But it will be necessary to achieve an accurate 60 degree bend in this operation.

I have to take a break now, dinner time, but I will be back soon with my ideas for construction of the second, and crux tool. For now, play with your paper model and I hope you can visualize what I have in mind. A hint, this will be what I call a "pad die" we will be pucshing face C straight down against a rubber pad between sides that will bend up CB and CD.

This thread seems to have died, at least for the moment. But as I promised this is my idea for a second operation tool to complete your formed pyramid If you have further interest, get back to to this discussion for more details.