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).

http://img401.imageshack.us/img401/7590/dsc00154eq4.th.jpg (http://img401.imageshack.us/my.php?image=dsc00154eq4.jpg)

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 :p

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.

What material are you using
WJF

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.

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 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

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).

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


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

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.

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

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?

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

Thanks for all the help folks.
Ive made another female tool and this time the side wall is slightly tapered and has 0.3mm more clearance all around, there is a 3.5mm radius on the leading edge(which is polished) and i've increased the overall depth.
I also used anti-scuffing paste.

Here's a wee pic of my new tools and one of the dishes stuck in the die:

http://img468.imageshack.us/img468/2919/dsc00160qa0.th.jpg (http://img468.imageshack.us/my.php?image=dsc00160qa0.jpg)

It seems as tho its a success but now i have to think up an ejection method that is quick and easy.

Any suggestions?

i was thinking of maybe boring a hole, slightly smaller than the first dish radius, through the back of the female tool which would be counter bored from the back face to allow for a removable spigot. That way, once a dish is formed, i could retract the press, take off the die and then knock out the dish with a piece of plastic and a hammer.

Could someone please help me with the design of the trim die as im not quite sure i know what it would look like?

Thanks,
Si.

To simplify ejection make your female die slightly deeper so you can have a larger diameter entry about 1.2 times as deep as the smaller section which forms you dish. This larger entry also acts to preform the material.

In the bottom of the female die drill three through holes then make an ejector which has three pins that fit through the holes in the male die.

Form your dish, turn the male die over, insert the ejector and push the dish out of the small forming diameter into the larger entry diameter; it will drop out of this diameter when you pick the die up.

For trimming make a mandrel which matches bottom of the female die and mount it in a lathe chuck. Make a plug that matches the male die and fit it on a live center. Grip the dish between these two in a lathe, machine off the rough rim and chamfer the corners.

I've got next to no experience in forming operations, although we've done some similar projects in the shop on steel parts.

I think the aluminum is going to be difficult on account of scuffing and seizing problems. Some of the aluminum bronzes might make a good die material, along with some kind of lubrication, of course.

Perhaps two dies would be advantageous, one with greater radial clearance that makes it easy for the material to flow, and gives an intermediate dish with slightly tapered sides. This die would not have to completely contain the dish, as its edge would merely serve as a fulcrum to get the rim to bend up uniformly. The part should just lift out of this die. This die could have the detail on the bottom to form the cove in the bottom corner. The punch should seat fully in this intermediate die.

Then, take the partially formed part, relube it, and press it into the finish die to reform the wall somewhat straighter. Or something :D

BTW, I think I'd dispense with the pin/pilot thing in the punch, it just makes a mess. It should not be too difficult to build a centering ring to lay the blank into.

The pin in the centre didnt do that damage, it was me while i was trying to eject the dish using a small diameter rod which fitted through the M8 spigot mounting hole. Oops :)

About the trim die: i thought you meant some contraption that would be used on the press. Trimming them on the lathe should be no problem, ill just use my male die to locate the dishes and have something on the other side to grip them.

Si.

Rather than using a female die at all, try a 3/4" thick pad of urethane around 90-95 durometer (will feel like hard plastic), put your aluminum blank on that and fasten the male die to the ram of a 20 ton hydraulic press, thats about 6k lbs. I use urethane often rather than a female die, half the work and a better surface finish on that side of the part.
For thinner material, cut a hole the shape of the part in steel, put the stel in the press, place the oversized material to be formed centered over the cavity in the steel, place the urethane over the material, place a thick cover plate over the urethane. Pump the press up in 1k lbs increments (helps to have a press with a pressure guage) until you have the degree of shape you seek. This is a common silversmithing/jewelry making technique.
Regards, Chrissi

Sometimes the trimming process should be setup in the drawing process. The choice becomes the quality of the trim edge that you can live with verses the time it takes to do each part and to minimize how many times you really want to handle it.

I don't think you need to draw that part so deep into the female die. That is unless you want to put the female center dome on die springs to push it back out as a one shot operation. More complex die, but I think you get the idea.

I tried to represent another approach to trimming the edge as a cross section of your finished part.

The option to the right is what to expect on a lathe operation. Slow, but certainly functional.

The one to the left is a punching/shearing operation that requires a bit more blank size, but much less draw on the part. The die can be a simple hole in a plate the finished part can be punched and pushed through(red line is the trim edge. Placing the parts dome down will self align. The top die only needs to penetrate the material thickness. The parts can be tumbled to clean up the trimmed edge. Quick, but the edge quality may not pass muster without some deburring. This will also take another modification to die set.

DC

Sometimes the trimming process should be setup in the drawing process. The choice becomes the quality of the trim edge that you can live with verses the time it takes to do each part and to minimize how many times you really want to handle it.

I don't think you need to draw that part so deep into the female die. That is unless you want to put the female center dome on die springs to push it back out as a one shot operation. More complex die, but I think you get the idea.

I tried to represent another approach to trimming the edge as a cross section of your finished part.

The option to the right is what to expect on a lathe operation. Slow, but certainly functional.

The one to the left is a punching/shearing operation that requires a bit more blank size, but much less draw on the part. The die can be a simple hole in a plate the finished part can be punched and pushed through(red line is the trim edge. Placing the parts dome down will self align. The top die only needs to penetrate the material thickness. The parts can be tumbled to clean up the trimmed edge. Quick, but the edge quality may not pass muster without some deburring. This will also take another modification to die set.

DC

Mr. DC, If a complete new die is in the works, how about incorporating a pressure ring on the periphery for control? Then, at the end of the forming, the actual button will be trimmed to finished dia, hopefully the desigh will allow a slight flair. These parts could be pierced/formed/blanked in one punch cycle from long strip.

Ejector springs you mentioned will clear the part, as long as the part does not hang on the male punch (a stripper will cure this), air jet or a fence to direct it to the exit chute. A one or two station die would be straight forward and could do auto advance indexing. Seems this is really a small punch press continuous feed job from a spool of strip/ribbon. Subsequent edge treatment must follow.

You covered the subject well. nicely done. Although I have mixed a few disciplines and methodologies here, "Thought breeds thought."

Lloyd

You got the idea. All we can offer is whatever we have added through the years to our own bag of tricks.

Now you are talking about a progressive die setup? That is a bit more involved in terms of stripping, alignment pins with lift and feed track, and shearing up the excess at the output end. That type of tooling costs has its payback when you can affordably ammaturize it in the part production price over high production quantities. At least you have the ability to handle much of it yourself to keep the price low. You are about to get very aquainted with tool steels, heat treating and grinding......

As had been mentioned, placing a slight draft angle at the lip edge, tangent to the radius on a shallow female die cavity should really help in keeping the part from being wegded into the female die. This may be what you meant by flair or flare?

After a bit of thought, some experimenting with your blanking diameter, you may be able to form the dish without trimming the edge. If you can end the radius short of wrapping 90deg on the outer lip diameter(with or without a draft angle), then there is no side pressures to lock the part to either of the dies. As a guess, you are only pressing the material 3/8-1/2" and as long as it is equally centered on the pin, it might be worth a try with the shallowest die you can get away with.

To prove the forming concepts one stage at a time, you may be able to just modify one of the die set you have. Cut some(most?) of the length off the female die lead in and add a ring to the male dome to control the trim flange wrinkle if you so choose?

The suggestion of using the concave dome for ejection in the female die was in the form of a captured piston setting on die springs inside a ring bolted to a sub-plate. This would now be the bottom die with a step cut into the rings top ledge to orient the blank on center. At rest the concave piston would be up, but the forming process will push it down to a dead stop. When the punch retracts, the dome pushes the finished part out.

DC

Remember the quantity is a couple of hundred. I think you are designing for a number with two or three more zeroes. :)

Mr. DC, you said it far more eloquently. Additionally, I seemed to get off track and not answer the specific question. Perhaps I suffer from that oft employed but not medically recognized "If I am going to do this , I may as well do . . ." syndrome. So. I lost my head. Sorry for the distraction.

Although, there are so many 'off the shelf' parts for die makers, coupled with this man's equipment and talent pool, I still believe starting with a clean die set and a few parts; blocks, die springs, stripper bolts, ground pins, shim stock, prototypes could be easily made in a shop press, thence production runs in a punch press..

The initial draw is a shallow cup, not difficult, just a little tuning will get a wrinkle free shape with clean non-scuff release, then whatever edge treatment to follow. I shall cease with this, you are far better equipped to give advice here, Siowenson is in good hands. Thanx for your comments, informative.

Geoff, thanx, yes I did address this matter above, good lesson for me to resist contributing till I thoroughly understand the initial query.

Lloyd

PJ, you are giving me far more credit than I deserve. Most of my offerings are back woods hypothesis from periodic exposure in several manufacturing arts. I'd say I may know a little about a lot of $--t, but I won't claim to know a lot about the little $--t!:p

I'd rather remain humbly One of Many, so what you, me or anyone else has to offer doesn't get us off the hook that easy. Shared talents are the treasure here...of which, I probably read 3 times more than I care/am confident to respond to.

DC

On the Discovery Channel show "How It's Made!" they did an episode about pots and pans. It was season 2 episode 11. Go to this web site and take a look www.crowncookware.ca/spinning.htm They discribe how they do their work. I you can find the show I suggest you watch it. You may find that it answers alot of your questions.