Need help forming a dish

[siowenson]

Hi there folks, i need some pointers on how best to form a dish.
I have made a press tool which i thought would do the job but unfortunately it failed.
Here is a pick of the top and bottom tool, my first attempt(on the rhs) and my second attempt(lhs).



The first attempt crumpled up while forming the side walls of the dish as shown.
For the second attempt i reduced the outside diameter of the blank and it formed no problem. its just a pity the side walls are nowhere near the length i want

What am i doing wrong here? I'm guessing there's some sort of boundary involved when forming a dish with parallel side walls out of a circular plate?

Should i form the base of the dish with the press tool then try and spin the walls?
Help!

I dont have a spinning machine available but i do have cnc mills/lathes and conventional mills/lathes.

ps. im lookin to produce a couple hundred of these.

[wjfiles]

What material are you using
WJF

[siowenson]

i think those blanks are made from 6082 which is my fault because i never specified a grade to the laser programmer. Ill ask him later today to make sure and if it is 6082 ill get him to cut me some using a 50** grade.

[big_mak]

maybe try putting some back draft on the male side so the material has somewhere to go!!!!!!then it shouldn't bind quite so much. Did you account for a forming allowance?

[9lrac9]

9lrac9 Here... What is the thickness of the material that are trying to blank, as your other friend said leave the sides open and make the diameter larger, blank the material and let it deform the material, and then make a trim die for it a long as you have these machines avalible to you. other wise you can do like Coke does with their coke cans they start with a slug of alumnium and then drop the hammer into the die .016 smaller in dia, with the shape of the coke can and they drive it at high presure high speed and the material is forced into the shape of the coke can with no deformities. There is lots of ways to shape metal. How much time and how much money do you have and how much do you plan on making on each piece. if the are just one off parts you can do it crude. 9lrac9

[Med-Pac]

Good morning,
In regards to your forming problem, we formed something similar to what you are doing out of .05 6061 T-4. The biggest trick for us was to press the material very slow, (with the right die clearance).

[9lrac9]

Oh PS the die you made looks very nice for you first try


9lrac9

[9lrac9]

Make the draft on the sides about 10 deg and leave more material on the Dia and since you have the fancy hole in the center you can make a trim die to trim the excess of the edges simple stuff your on the right track. The hole will center it on the trim die and make it look clean


9lrac9

[siowenson]

Unfortunatly the ally was 6082 so im gonna get more cut out with 5251.

The material is 1mm thk.
In my naivety i never allowed any forming allowance so there is only around 0.1mm clearance when the blanks are being formed.
What forming allowance should i be working with?

Ill try putting a draft angle on that male tool and see how it goes with the 5251 ally. Will 5 degrees do it?

These will be part of a decorative candle holder. 5 dishes per holder. im hoping to get about £20-£30 each for the unit.

As for the condition of the die: im a supervisor in a small cnc mc shop so cutting those tools was run of the mill, its just the method of forming that has me stumped.

Thanks for the help so far.
Si.

[siowenson]

hehe, was typing my post when u were.
ill try the 10 deg.
Thx.

[siowenson]

not sure whats going on here but my 2nd last post has been persponed untill a mod has a look at it but my last one has went straight on.
Is this usual?

[One of Many]

I can't say I have a lot of experience here. I'll just suggest some issue that I'd think may help.

Besides the material forming properties being poor there are some changes I would consider.

Polishing the dies to get good material flow and using drawing paste/grease are very important. The dies should be steel or other material harder than the material being formed. There is also no lead in radius to the bottom edge of your female die. This will not allow the material to pull into the die as it needs it. Sure as the evidence of tearing in the sample pic's. It is unlikely the blanks trim edge can be formed without a secondary trimming step.

Metal spinning is one option, but slow for mass production. Another option would be with a solid rubber block captured in a steel cylinder for the upper die as a cheap alternative to hydroforming.


DC