Embossing question

[Chincia]

Has anyone tried embossing thin sheet metal with a CNC vertical mill? Am looking to make many, many tree leaves out of say 0.025 inch or thinner copper or stainless.

I would make a female tool bed to fasten to the table. Male embossing tool would be attached to the spindle as one of the tools. Program wold press several 'leaves, change tools, and then cut them out.

[Chincia]

I think I just answered my own question. Looking at other posts, it seems pressure in the Z axis without rotation is a bad idea.

[txcowdog]

You need a hydraulic press called a "Clicker" If you go to http://www.owossographic.com they can make the positive and negative dies you need for embossing. I you don't have a clicker, perhaps a press like would be used in an auto shop. In any case both dies are mounted in the machine (there is a trick to getting them aligned) then place the item to be debossed in between the the dies and the head is lowered to apply pressure. The pressure needed is in the tons. The clickers we use are 25 ton presses and on some items, they strain under the load. Best of luck with your project.

[lakeside]

Originally Posted by Chincia I think I just answered my own question. Looking at other posts, it seems pressure in the Z axis without rotation is a bad idea.

no I have used a cnc-mill to broach out corners before but it was in alum. All cnc have sensor for spindle and will trip if load increases

[Geof]

Originally Posted by Chincia Has anyone tried embossing thin sheet metal with a CNC vertical mill? Am looking to make many, many tree leaves out of say 0.025 inch or thinner copper or stainless. I would make a female tool bed to fasten to the table. Male embossing tool would be attached to the spindle as one of the tools. Program wold press several 'leaves, change tools, and then cut them out.

How big are your leaves? As txcowdog says you might need significant pressures. I have seen equipment for embossing broaches (that is the kind you wear not the kind used to make odd shaped holes) in thin brass and it developed very large impact pressures. I think embossing and then cutting out will be very difficult. Even just the cutting might be difficult; copper is not easy to machine and you would probably finish up with a very large burr along the edge and .025 is very thin so it would tend to pull up the cutter. Stainless also would be difficult to cut out with pulling up and also forming a large burr. Holding the material would also be very difficult and you would not be able to cut the leaves out all the way around; tabs would have top be left and cut by hand later.

You might be better looking at getting your shape cut by laser which works fine on stainless but I don't know about copper, then emboss them.

[Chincia]

Thank you all for the input. I too had wondered how I would cut them out after embossing.

I will not use the spindle to do the embossing. I have a press and will use that. I will make a test set of male & female dies with the CNC. Alignment will be with pins in the 4 corners. Will slip the material between them & put it in the press. Will cut them out manually with snips. If things work out, I will make a set of male/female dies for the leaf shape & proceed.

First I have to study techniques for the dies. I remember there were several things to consider when stretching & these have to be considered in this application. When I get smarter & actually make a leaf, I will post a pic.

[JPMach]

I believe with some research of course, you could build a two stage set of dies. Using a shop press or something the top would come down and emboss the shape and then with a little more force a second top piece comes down and cut out the shape. But then if you build thid this requires die springs to make the stages work in the right order and probably stripper plates (not the kind from the bar with no windows) to strip the embossed part from the cutout die and to strip the waste from the bottom die. I think it can all be done but it would take some time.

Course if you get that far you might as well go ahead and put in a auto feeder from coil stock and just set the controls for the shop press up with a few limit switches to cycle it up and down. Look up a book called DIE Design fundamentals, it has lots of informative stuff, I belive it even gets into two and three stage dies.

JP

[Chincia]

I had not intended to get back into it that deep. I remember watching my father making three stage dies. He did it in our garage just because something was needed at his work & nobody wanted to pay for someone to do it. Of course it worked & worked perfectly. But he was the kind of engineer who would have the patience to actually do all the steps in 'Machine tool reconditioning' by Connelly. I doubt I am that patient.

Thanks for the tip on the reading resource. It may be the same one I remember my dad had. Will have to dig through his stuff.