MACHINING C110 Copper Vs C360 Vs Aluminum 6061

[imagineers]

Ok so I have a part I need machined, and I want to use C110 copper for its heat transfer characteristics, however I have read a lot about it having a 20% machining rating vs say c360 at 100%, aluminum has better thermal transfer rate than C360 but I need atleast a 63 microinch surface finish on the outside and not sure aluminum can accomplish this??? I guess my question is can I use C110 copper to make this part with a .025 critical tolerance on the inside diameter, and a surface finish like I mentioned (used for o-rings)?? If not what the best option

 

[BillPSU]

Your next run of this part complete the run and then put an aluminum part in the fixture and make one. See how it comes out. You should really change the machining speeds and feeds but for a test you may not want to mess with the machining parameters. You may have some special copper coolant which may not work well with aluminum which yoy may have to change.

Bill

 

[dgallup]

Some (most?) aluminum alloys machine very well. You want to use it in one of the harder conditions so it is not gummy. I've had very good success sealing o-rings using 6061-T6.

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[MikeHalloran]

If you model the complete heat transfer system, you will see that various boundary layers and related processes dominate the overall system performance, and that a difference in bulk material conductivity of a thin metallic wall affects the overall situation so little that it is very difficult to actually measure such a difference.

I.e., use the free machining brass, or maybe the aluminum, based on cost/ weight/ strength/ joining criteria, and forget the copper.



Mike Halloran
Pembroke Pines, FL, USA

 

[TVP]

I completely agree with Mike. Forget the C110 copper, and use either 6061-T6 or C360 brass. 6061-T6 will have a good surface finish when machined properly (specific feeds & speeds, tool geometry, coolant). Many millions of automotive suspension dampers (shock absorbers) have used 6061-T6 aluminum rod guide bodies/housings with o-ring grooves for sealing high pressure hydraulic fluid.

 

[imagineers]

Thanks guys, I would have liked to use the 110 copper for its heat transfer characteristics as this will be attached to an aluminum plate underneath and that transfer of heat will also be critical. reasons not to use the Copper??

 

[TVP]

Expensive, poor machinability, potential for galvanic corrosion...

 

[MikeHalloran]

You also have the option of combining the aluminum whatsit with the aluminum plate, thereby completely eliminating the thermal resistance of a mechanical interface and any corrosion within from the heat transfer equation.

The thermal resistance of air and liquid boundary layers is greater than that of a mechanical contact surface pair by orders of magnitude, even if the mechanical interface is lapped smooth and filled with a heat transfer compound.

... and the thermal resistance of a thin wall of metal is orders of magnitude lower than that of the best mechanical interface.

You are wasting your time diddling with material selection, unless you use aluminum and combine the parts to eliminate an interface as mentioned above.


Mike Halloran
Pembroke Pines, FL, USA

 

[capnhook]

What MikeHalloran and TVP and dgallup and BillPSU said...

You don't need an "imagination" to select the correct material, just use common sense (and try to combine the aluminum parts, also).

Proud Member of the Reality-Based Community..

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[ornerynorsk]

Your part is a perfect candidate for aluminum extrusion. To get the surface finish, a light machining or electropolishing should be all that's required.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[tomsmith01]

There are most important and expensive part of metals. Aluminum is quite good than copper.

 

[JNieman]

The rest seems covered well, so I'll just add to the mechanical feasibility of aluminum: 63micro-inch is quite easily feasible in a machining process. 32 isn't even that bad. When you hit 16 micro inch, you will see a little bit of a price increase on your quotes but it's still quite feasible. 63 micro inch is still well within the realm of standard machining without a separate finishing pass, even.

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