What size press do I need?

jdholbrook33 · May 19, 2017

Say a person had some C110 copper (half hard) that was about 1/8" thick and 1.5 x 1.5" square and he wanted to use a press to make a depression about 1 x 1" square and about 0.020" deep.
Of course, using self made dies out of tool steel, possibly hardened.

What size, in tons of pressure, would it take to do something like that and make, say 10 per day?

magneticanomaly · May 19, 2017

Drawing (making the whole piece a shallow cup), not so much. 10 - 20 tons.Coining (squeezing the metal thinner to make the depression), a lot more, maybe 100 tons.

DDoug · May 20, 2017

Send some samples to Kpotter.

TDegenhart · May 20, 2017

Tonnage = ultimate strength x area.

In your case the area is one sq inch, the ultimate strength is in the area of 50,000-60,000 psi, depends on degree of cold work and the actual alloy. So the minimum would be in the 60 ton range. 100 ton may be over kill.

Tom

JLarsson · May 20, 2017

TDegenhart said:
Tonnage = ultimate strength x area.

In your case the area is one sq inch, the ultimate strength is in the area of 50,000-60,000 psi, depends on degree of cold work and the actual alloy. So the minimum would be in the 60 ton range. 100 ton may be over kill.

Tom

Is there some other math at work here, or is that a safety margin, or...? 50,000-60,000 is only 25-30 ton.

TDegenhart · May 20, 2017

OOPS!!!

Tom

cyanidekid · May 20, 2017

isn't it yield, and plastic flow, not UTS that govern here? are they always closely related? (don't think so, consider tungsten carbide, glass, iridium, pure tungsten, there are wide variations in the gap from yield to UTS)
if the depression can have some taper toward the center (i.e., conical) it would take less pressure, I would think.. dead soft obviously would be easiest.

yield in compression + rate of work hardening?

jdholbrook33 · May 20, 2017

cyanidekid said:
isn't it yield, and plastic flow, not UTS that govern here? are they always closely related? (don't think so, consider tungsten carbide, glass, iridium, pure tungsten, there are wide variations in the gap from yield to UTS)
if the depression can have some taper toward the center (i.e., conical) it would take less pressure, I would think.. dead soft obviously would be easiest.

yield in compression + rate of work hardening?

The reason I want to use a press is to get a perfectly flat depression.
I have tried milling it but all my efforts have not yielded a surface flat enough.
've tried different strategies and different end mills, I've tried end mills with wipers, I've tried two flute, three flute, four flute. Then it struck me to just use a press and press the depression into the copper.

Maybe some type of hybrid is the answer, mill the pocket and then use a press to make it perfectly flat. (Doesn't have to be perfectly parallel with the opposite surface)

I don't have the room in my shop or the budget for this project to afford a 100 ton press. I can see buying a 20 ton ($500ish).

The best solution would be to mill it out since it will be in the mill anyway.

Johnny N · May 20, 2017

mill it and leave a few thou, and then a nice 'bump' with a small, manual flypress ? Ive no idea on tonnage calcs, but I work for / in the metal processing industry and know what 100 ton of work looks like in a blow to a piece of metal! My gut feeling is your in 'whack with a sledge hammer / flypress' territory with this job for a .020" depression.

edit, unless you have a fancy (=higher tonnage) die, you will have 'dishing' when you put the impression into the material. you will then be into a 2nd flat die op. to push it back flat, or start with thicker material, and then mill the top and btm faces back to your 1/8". As you are displacing material with pressing / hammering , your 1.5" sq starting piece will end up, not uniformly, bigger. and need cropping or machining back to size.

Be interested in Kevin Potters opinion for sure.

cyanidekid · May 20, 2017

if you don't need the sharp corners (sub .015 radius), I'd keep trying to find a solution on the mill.

milling and then pressing would still leave some milling cutter marks, unless you had the full tonnage to get the metal to really flow, and you would still see "ghosting" from the cutter.

don't forget, if you displace the metal with tonnage,it will open up larger than the punch as the metal flows outward, with some "rollover" at the edge of the depression too.(and with probable cupping or dishing as pointed out by Johonny)

what is the problem now with the milled surface? flatness, or surface finish?

what are you trying to achieve here actually as far as flatness and surface finish? "perfectly flat" is meaningless. mirror finish, 2 microns, or 2 thousandths ?

what mill are you using?

what cutter(s), HHS? carbide? what coating? what lube?

have you tried double sticky tape to a steel backing block?

I think the question is "how do I get a better milled finish in copper" not what press...

what you would be asking the press to do is actually "coining"(concur with magnetic in #2), and that size coin is made on something like a 150t press..

TDegenhart · May 22, 2017

If you want something flat in a press, use stippling on the die. Look at sheet metal used in computer hard drives, structure parts like that. The have series of diamond shaped marks. That is stippling. What it does is to cause plastic deformation uniformly and so eliminates the "squishing out" of a flat punch.

Tom

rogertoolmaker · May 23, 2017

Calulate /tonage requirement

jdholbrook33 said:
Say a person had some C110 copper (half hard) that was about 1/8" thick and 1.5 x 1.5" square and he wanted to use a press to make a depression about 1 x 1" square and about 0.020" deep.
Of course, using self made dies out of tool steel, possibly hardened.

What size, in tons of pressure, would it take to do something like that and make, say 10 per day?

To Figure Tonnage:
Material Thickness X Perimeter of Part X Tensile Strength of Material / 2000 lbs.= Blanking Pressure in Tons.

Estimated Tensile Strength of C110 Copper 20,000 PSI. To "Draw" a shell 1" square .020 deep about 25 percent of the blanking pressure. To "Coin" a 1" square .020 deep I estimate 65 percent more than the blanking pressure. Definitely harden the steel to 60-62Rc. I suggest O1 or A2. If you are going to run production levels use D2.

Roger 05/23/2017

jdholbrook33 · Jun 8, 2017

cyanidekid said:
if you don't need the sharp corners (sub .015 radius), I'd keep trying to find a solution on the mill.

milling and then pressing would still leave some milling cutter marks, unless you had the full tonnage to get the metal to really flow, and you would still see "ghosting" from the cutter.

don't forget, if you displace the metal with tonnage,it will open up larger than the punch as the metal flows outward, with some "rollover" at the edge of the depression too.(and with probable cupping or dishing as pointed out by Johonny)

what is the problem now with the milled surface? flatness, or surface finish?

what are you trying to achieve here actually as far as flatness and surface finish? "perfectly flat" is meaningless. mirror finish, 2 microns, or 2 thousandths ?

what mill are you using?

what cutter(s), HHS? carbide? what coating? what lube?

have you tried double sticky tape to a steel backing block?

I think the question is "how do I get a better milled finish in copper" not what press...

what you would be asking the press to do is actually "coining"(concur with magnetic in #2), and that size coin is made on something like a 150t press..

I have a HAAS VF4Ss and VF2, both relatively new.
The end mills I've tried have mostly been naked, name brand (Iscar, Kenametal, Sumitomo etc..) I did try a few coated end mills and couldn't see any difference.
In researching I read that copper likes diamond so I picked up a CVD and PCD 1/8" that I will try when I am able to get back on this project.
The copper blank is held in softjaws as it has an upset on the opposite side that makes it real convenient to drop it into a milled slot and the lip is used as reference for the second op which is the final trim to shape and the pocket we're talking about.

The copper will be used for a heat sink and the pocket is the area that touches the part that needs cooling.
The goal is to have the most efficient cooler possible so that means the most surface contact possible.
Milling marks = small valleys left from the cutter = less surface contact area.

I'm open to any suggestions to get it done on the mill

Maybe farming out to a press punch shop?
Up till now all jobs that I've farmed out have not worked out so well so I'm a little reluctant to go that route.

I have to say, the idea of some type of hammer punch sounds good. Get the guys out and see who can hit it the hardest with the side benefit of relieving stress while being productive at the same time.

HuFlungDung · Jun 8, 2017

jdholbrook33 said:
I have a HAAS VF4Ss and VF2, both relatively new.
The end mills I've tried have mostly been naked, name brand (Iscar, Kenametal, Sumitomo etc..) I did try a few coated end mills and couldn't see any difference.
In researching I read that copper likes diamond so I picked up a CVD and PCD 1/8" that I will try when I am able to get back on this project.
The copper blank is held in softjaws as it has an upset on the opposite side that makes it real convenient to drop it into a milled slot and the lip is used as reference for the second op which is the final trim to shape and the pocket we're talking about.

The copper will be used for a heat sink and the pocket is the area that touches the part that needs cooling.
The goal is to have the most efficient cooler possible so that means the most surface contact possible.
Milling marks = small valleys left from the cutter = less surface contact area.

I'm open to any suggestions to get it done on the mill

Maybe farming out to a press punch shop?
Up till now all jobs that I've farmed out have not worked out so well so I'm a little reluctant to go that route.

I have to say, the idea of some type of hammer punch sounds good. Get the guys out and see who can hit it the hardest with the side benefit of relieving stress while being productive at the same time.

View attachment 200621 View attachment 200622 View attachment 200623

Don't they use silver bearing compounds like Arctic Silver between chips and heat sinks any more?

I'm of the opinion that the width of tool marks is nothing (if the surface is smooth) compared to the conduction rate of copper, so far as being a heat sink is concerned. I take it that you are interpolating the flat face with an endmill, and not simply plunging.

jdholbrook33 · Jun 9, 2017

Don't they use silver bearing compounds like Arctic Silver between chips and heat sinks any more?

I'm of the opinion that the width of tool marks is nothing (if the surface is smooth) compared to the conduction rate of copper, so far as being a heat sink is concerned. I take it that you are interpolating the flat face with an endmill, and not simply plunging.

Arctic Silver is old school now. The latest are liquid metal type based on Gallium. A magnitude more efficient than AS or any of the older products.

Intel's latest processors are so screwed up that people are dropping their temps by 20c to as high as 30c just by using the liquid metal type on the CPU die under the heat sink.

I'm aiming at the enthusiasts and they want bare copper and mirror finish on both sides.
The top side I can get a really good finish with a face mill then hit it on the buffer.
I'm just having trouble getting that pocket floor free from tool marks.
So I figured using a press would be the way to go.

This weekend I'm going to chuck up the diamond end mill and give it another go. Ramping in, big overlap and ramping out.

Any other suggestions on milling a good floor finish?

HuFlungDung · Jun 9, 2017

I find in turning copper commutator bars, the copper chips themselves, even if very light, tend to stick to the tool, then pass through at various intervals, and I always get a bit of surface scuff (probably chip rewelding) that could look like tool marks, but is not actual tool marks. If you've got high pressure coolant, you may be able to prevent this on a milled surface.

Giving the part an actual bump with a highly polished punch in a coining press may work best (comparable to burnishing), but I think you'd have to experiment to find out how truly flat it would be.

adama · Jun 9, 2017

I think the 60 ish ton range would be a fair guess, if it was annealed first, you may get away with a fair bit less, it would be easy to press it enough to get it back upto half hard. Some of the large cheap shop presses would be just enough to get there. if you want the best part contact though, you probaly want to then anneal it back soft so it can deform as much as possible to the actual parts your trying to thermally link.

I have had reasonable luck making dies like this out of Hardox wear plate ofcuts. Holds up surprisingly well, finish on the dies will exactly be reproduced in the final parts, assuming half decent finish on the sheet to start with its possible to end up with near optical qualities of finish if the tooling is ground that flat and polished - lapped that well.

With the limited quantity and the efforts your going to have you considered silver? its a fair bit more thermally conductive and on a part this size the costs not too silly these days either.

jdholbrook33 · Jun 10, 2017

adama said:
I think the 60 ish ton range would be a fair guess, if it was annealed first, you may get away with a fair bit less, it would be easy to press it enough to get it back upto half hard. Some of the large cheap shop presses would be just enough to get there. if you want the best part contact though, you probaly want to then anneal it back soft so it can deform as much as possible to the actual parts your trying to thermally link.

I have had reasonable luck making dies like this out of Hardox wear plate ofcuts. Holds up surprisingly well, finish on the dies will exactly be reproduced in the final parts, assuming half decent finish on the sheet to start with its possible to end up with near optical qualities of finish if the tooling is ground that flat and polished - lapped that well.

With the limited quantity and the efforts your going to have you considered silver? its a fair bit more thermally conductive and on a part this size the costs not too silly these days either.

For sure Silver is better and there are 3 prototypes in the wild. Reports are 5c cooler than stock (stock is nickle plated copper).
I have a Silver supplier who casts rough blanks which get machined. Now, using a punch / press on the silver could be the perfect solution as it is quite a bit softer than copper.

I was struck by an idea last night (funny how we do our best thinking while laying in bed just before sleep).
Why not angle the surface and hit it with a ball end mill? Use a super small step over and just ball track it smooth?

Reptar · Jul 22, 2017

I know all our presses at our shop will tell you how much tonnage it took to get to the position in the stroke it took.

I'd simply send out and have a sample part done. Ask them to record how much tonnage it took. In our case we do free samples all the time for customers if theirs any hint of more work behind it coming.

What size press do I need?

Plastic

Titanium

Diamond

Diamond

Cast Iron

Diamond

Titanium

Plastic

Cast Iron

Titanium

Diamond

Cast Iron

Plastic

Diamond

Plastic

Diamond

Diamond

Plastic

Plastic

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