HDPE for drawing aluminum sheet?

Have some thick chunks of HDPE and wondering if that might work for drawing some 1/2" deep cups of 0.027" thick aluminum "coil stock". I could build a metal ring around the female section to resist spreading. Or do I really need steel which is what I have been planning? Any links or info on using HDPE or is it just not going to hold up even for a few parts?

It should work, take a look at these videos for some ideas.

https://www.youtube.com/watch?v=xw5yEMsDxR8

And this one

https://www.youtube.com/watch?v=fxzqkhmcRlY

Ran across this video of shaping steel sheet with wood forms with a little help from some steel covers. Clever way to use additional jack in press frame to provide pressure for blank holder (toward the end).

https://www.youtube.com/watch?v=29iC6RlbL7s

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Originally Posted by Jim27

Have some thick chunks of HDPE and wondering if that might work for drawing some 1/2" deep cups of 0.027" thick aluminum "coil stock". I could build a metal ring around the female section to resist spreading. Or do I really need steel which is what I have been planning? Any links or info on using HDPE or is it just not going to hold up even for a few parts?

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You would normally use Urethane; you make a form then press the form into the Urethane
https://www.polyprod.com/polyurethan...thane-tooling/

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Originally Posted by mactec54

You would normally use Urethane; you make a form then press the form into the Urethane
https://www.polyprod.com/polyurethan...thane-tooling/

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Yes, I understand the process with Urethane for one side and a solid form for the other. That's not what I am planning. I am talking about making the male and female form out of HDPE. Obviously won't hold up like steel but might work for at least a couple parts to test out things. Maybe more. I don't need thousands of parts.

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Originally Posted by Jim27

Yes, I understand the process with Urethane for one side and a solid form for the other. That's not what I am planning. I am talking about making the male and female form out of HDPE. Obviously won't hold up like steel but might work for at least a couple parts to test out things. Maybe more. I don't need thousands of parts.

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How big is the inside form cup??

The pressure required will also have to be worked out, depending on the form size, this will determine the material you can use

There are people that are 3D printing plastic forms to make parts like this so you may be able to use anything for just a few parts

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Originally Posted by mactec54

How big is the inside form cup??

The pressure required will also have to be worked out, depending on the form size, this will determine the material you can use

There are people that are 3D printing plastic forms to make parts like this so you may be able to use anything for just a few parts

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Total area for the cup is about 48 square inches but the stress limit on the plastic or whatever is used is PSI not total pressure. The pressure is also heavily dependent on the sharpness of the corners and the draw ratio as I understand it.For a trial run I am working on a part that is about 1/4 size with bend sizes of the full size part.

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Originally Posted by Jim27

Total area for the cup is about 48 square inches but the stress limit on the plastic or whatever is used is PSI not total pressure. The pressure is also heavily dependent on the sharpness of the corners and the draw ratio as I understand it.For a trial run I am working on a part that is about 1/4 size with bend sizes of the full size part.

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It will be a good experiment to see what you can do with the HDPE that's a large part, at the least you should have the male form made from a solid material, like steel aluminum Etc.

Hi Jim - "drawing" requires a double acting press? One action to push the die into the mould and one action to hold the edges of the blank so the sheet is maintained in tension. You describe the shape as a cup. If you have a flat sheet and a die that pushes into a hole it will wrinkle? What is the AL alloy and temper? Peter

I think it is 3105 H15 or possibly H24. It's fairly formable - I did an embossing die that works well but that's a less complex operation. For the double acting press see the video on steel toe crocs - he added a second jack to a low cost press to get the blank holder force.

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Originally Posted by Jim27

I think it is 3105 H15 or possibly H24. It's fairly formable - I did an embossing die that works well but that's a less complex operation. For the double acting press see the video on steel toe crocs - he added a second jack to a low cost press to get the blank holder force.

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You can do it also with Die springs or even urethane springs, the more pressure you put on the top form the more the piece of material is gripped, so in his case with using the jack it is not increasing the pressure, which is what you want to happen to keep the sheet under tension, so it forms and prevents Wrinkling at the edges, the more pressure you can keep on the sheet the better the finished part will be

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Originally Posted by mactec54

You can do it also with Die springs or even urethane springs, the more pressure you put on the top form the more the piece of material is gripped, so in his case with using the jack it is not increasing the pressure, which is what you want to happen to keep the sheet under tension, so it forms and prevents Wrinkling at the edges, the more pressure you can keep on the sheet the better the finished part will be

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Was trying not to put the additional load of the blank holder on the main (small 20T)press as I think I may be near the limit just with the main press force. As far as increasing the pressure with stroke there seem to be lots of different theories and use cases on constant force or varying it during the press. In any case some springs may be good to keep nearly constant pressure as the thickness varies slightly.

I have considered making the corners slightly less sharp and then doing a secondary operation to sharpen the corners. Corner radius are about 0.2". I could take some narrow strips of material, bend it to a bigger radius and then try stretching it to tighter corner. Seems a little counter intuitive - compressing it to form the walls of the cup and then stretching it at the corners - but I am thinking that the larger radius would have better chance of success in the drawing operation.

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Originally Posted by Jim27

Was trying not to put the additional load of the blank holder on the main (small 20T)press as I think I may be near the limit just with the main press force. As far as increasing the pressure with stroke there seem to be lots of different theories and use cases on constant force or varying it during the press. In any case some springs may be good to keep nearly constant pressure as the thickness varies slightly.

I have considered making the corners slightly less sharp and then doing a secondary operation to sharpen the corners. Corner radius are about 0.2". I could take some narrow strips of material, bend it to a bigger radius and then try stretching it to tighter corner. Seems a little counter intuitive - compressing it to form the walls of the cup and then stretching it at the corners - but I am thinking that the larger radius would have better chance of success in the drawing operation.

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I was talking about Die springs not regular springs, die springs are designed for this, and yes you need a constant pressure, that will increase when the male form pushes down if it does not then you won't form your part, aluminum is quite easy to form so your .2 radius should not be a problem

If the material can't stretch, then you will have a lot of winkles

I was looking at some of this again and I linked to the wrong video for the press details - same person and project but this is the next video that shows what I wanted to point out about using a second jack in the press frame for the blank holder force at 21 minutes in.
https://www.youtube.com/watch?v=IcjgrB9vTec