Need to think outside the box

[MarkDavis]

Just been reading on 3D metal filaments, the material is powdered metal, 50-70% and polymer.
If the choice of nickel-silver was due to it's ringing quality, my guess is a printed cover will be unsatisfactory.
Not very strong either.

Taking a sheet of nickel silver and hammering to shape in a form will be much stronger than any thing cut from a billet or glued together with plastic.

 

[Maplehead]

I agree Mark, I don’t think anything 3D printed is for final work. I bought a bar of aluminum and I will attempt my own simple punch and die and figure out how to draw press these covers. If that works then I will figure out a way to do the real covers with the rounded sides and D logo.

 

[Maplehead]

Hi All
Ok, so I made my drawings for my simple punch and die. I'm going to be forming nickel silver that is .020" thick. The dimensions will be 1.25" long by .75" wide with .25" walls.
So here's my approach on how I will make this aluminum die set.
Die opening will be 1.79" x .79" x .406" deep
The bottom inside edge will have a .031" radius
The top of the die will have a .125" radius
Punch will be 1.25" x .75" x.426" tall
The punch top will have a .031" radius on it's edges
I made the .125" radius on the die for allowing the sheet to slide into the die. That portion of the sheet will be trimmed off.
That means the total height of the finished cover will be .25" + .031" equalling .281".
The sheet blank will be 2.14" x 1.64" and will basically go up to the .25" aligning holes.
Any thoughts on how this will go and/or improvements?

 

[whitmore]

So here's my approach on how I will make this aluminum die set.
Die opening will be 1.79" x .79" x .406" deep
Punch will be 1.25" x .75" x.426" tall

The sheet blank will be 2.14" x 1.64"

The sidewall area, that 0.4" step, represents stretching of the sheet; instead of stretching,
it can alternately wrinkle, and pull the edges of the blank sheet out-of-rectangular.
Stretching a sheet of nickel-silver that is 2.14" long, to a length of 2.8", requires your
die to exceed the tensile yield strength of the 0.020" material in that strip,
Alloy 770 (some data here) <http://www.nealloys.com/nickel_silver.php> wants
something like 40kpsi to stretch, and that means the long dimension has tensile stress
of 1300 lbs. The narrow dimension has maybe three times that.

I'm thinking the sheet edges won't remain straight, unless you clamp them hard, and starting
with an oversize blank (maybe with a few holes that slip over pegs) will be required. The 'waste'
area of the blank will act as a frame to keep the center stretching, rather than wrinkling.

 

[derf]

A simple form operation like that will still require a pressure plate. Basically a spring loaded ring around the cavity to hold the material down while stamping.

 

[Maplehead]

I was incorrect on the die opening being 1.79”. I meant 1.29”. Basically, .040” more than the punch to compensate for the sheet thickness, times two.
I have to digest the last two replies as I don’t understand them fully. I guess I have some more research to attend to.

 

[Maplehead]

Update
I made a test die set out of aluminum and then pressed a nickel silver test cover.
This can be done!
The sides of the cover are not perfectly smooth because my die sides were not perfectly smooth.
I need to drill out the middle of the die waste first, AWAY from the final edges. I always forget about doing that.
Anyways, now I just need to get the real die made but I nee CNC to mill the curves.