Help with stamping die design

[zpelgrims]

Hi.

New here, and relatively new to the machining craft as well.

I am looking for advice on how to create a die in order to create a specific shape. The shape looks like this. The sheet metal (likely mild or stainless) is 1mm thick. I am also making the blanking dies for inner and outer diameter blanking. I am remaking an existing part of a lamp. Small production volume. Outer diameter of the unformed blank is 120mm. I am 99% sure the original part was also formed in a die, so it must be possible..

Before I commence making the die set, I would like to tick off some (likely, since I am new at this) common mistakes...

• Should I blank the inner and outer diameter before forming the part?
• To achieve the rounded shape, should I push a positive feature into a square cavity, not touching the end of the cavity? Or should I make matching positive/negative features and press until both meet?
• How can I design the die so the part will be removable? I am worried about the extremely sloping sides. I feel like this will squeeze and stretch the metal between the die, making it nearly impossible to remove. How is this usually done? I understand springs can be used as ejectors, but it seems to me the clamping forces would be excessive for any spring I could fit into this die design.
• Is it possible to achieve the amount of deformation we see on the sides with a small hydraulic press? I think it's probably around 15 tons - unfortunately there is no pressure rating on the press as it was home-built some 50 years ago.
  
  Any other pointers are also very welcome...
  
  

 

[BajaFire]

1) blank after forming I think would work well here.
2) you're correct that the metal won't touch the sharp cavity corners. However, make the shape you want in the die, accounting for springback (in the absence of calculations, trial and error might help)
3) Part will be easy to remove if you don't blank it first. Also, spring back will help remove the part from the die. Use some WD-40 as lubricant before pressing
4) 1mm (.040") steel on a 15-ton press? I'd doubt it. Maybe you could use thinner steel or perhaps aluminum (it's only a lamp, right?)

 

[zpelgrims]

1) blank after forming I think would work well here.
2) you're correct that the metal won't touch the sharp cavity corners. However, make the shape you want in the die, accounting for springback (in the absence of calculations, trial and error might help)
3) Part will be easy to remove if you don't blank it first. Also, spring back will help remove the part from the die. Use some WD-40 as lubricant before pressing
4) 1mm (.040") steel on a 15-ton press? I'd doubt it. Maybe you could use thinner steel or perhaps aluminum (it's only a lamp, right?)

Blanking after forming would only apply for the internal diameter, correct?

I'll see what the lowest gauge steel is I can form. The original part is 1mm so maybe aluminium is a good bet. The original part certainly isn't aluminium, but this may be an acceptable compromise given my equipment. There is a pressure gauge on the press but it's in a unit I haven't been able to convert to the more common tonnage. I'll have a look when I'm in the shop.

 

[gbent]

For low volume work it is possible the part was spun.

 

[BajaFire]

Blanking after forming would only apply for the internal diameter, correct?

No; use a sheet way bigger than the final part, then blank both dias. afterwards. This helps account for uneven drawing (otherwise your part might suck into one side of the die faster, leaving you with an unfinished piece).

 

[implmex]

Hi zpelgrims:
Nuts as it sounds, for a small volume of parts I'd consider CNC turning from slugs or rings of heavy wall pipe it if spinning it from sheet is a problem.
Bonus if you don't NEED to turn out the inside...lamp bases can usually benefit from having some weight.
I wouldn't try to build a die for it unless I had lots (thousands) to make.

You're going to need a decent sized press for it too...it's 4 3/4" diameter, so you're going to need some poop to blank it and more poop to draw it.
You can find calculators on line to tell you how much tonnage: (it's a lot more than 15 tons for sure)
Here's a link to one:

https://societyofcostengineers.com › 2021/07

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[zpelgrims]

Gotcha re:blanking. Makes sense. I will just need to make a die that will allow for the already formed section to not deform. I think I might try to spin the edge, seems like a reasonable option since it's such a short section. I'm looking to produce about 200 of these, so to keep costs down I definitely would want to fabricate it out of sheet metal. It's just a part of a lamp assembly, not the base.

I did already make a 4 3/4" diameter blanking die, which worked fine in my press (using a sloping punch).

 

[Garwood]

Post pictures as you go along. More people need to see what you can do with a punch press and some basic tools.

 

[Hobby Shop]

Here’s a little die I made that’s similar to the part you’re making. I posted a couple pictures of it before but here they are again. Unfortunately I didn’t take any pictures of the punch but it was nothing special.

All in it took about 2hrs to make the die and 5-6 parts before I handed it off to my buddy.