milling copper (99%)

[nervis1]

I tried to run a 3d program on a piece of 1X4X12 copper bar today. It was a disaster. I broke one 1/2 carbide ball mill, and ruined another before I gave up.

I'll just be honest here and tell you all that I just used my standard .1 DOC and 60 ipm , 6k rpm that has worked well in 6061 I have cut in the past. Well after looking at the Machinery handbook turns out I should have had like 1500 rpm and 2 ipm. Whoops. My question is this...why can't I just increase the rpm and feed in proportion? The material hardness is probably the issue I guess, but seems to me that should work for some reason.

This program is going to take like 6 hrs at this feed, bummer. Copper is a PITA, I'm sticking with aluminum.

Anyone have any experience with copper? I could use some tips.

[arvidb]

Copper is difficult to machine. I worked for a company that wanted a piece machined out of copper (because of heat conductivity requirements). We hired a professional firm with very modern machinery. They did manage, but said they hated it - and it was expensive. I have also tried machining copper myself on a small manual mill.

I guess the problem with going faster is heat. Copper likes to clog the tool and this gets worse with heat.

I'm sure others here will have a better answer, this is just my experience with copper...

Arvid

[c-c-cncboy]

Yo Nervis,
For copper, toolbit manufacturers produce specific tools with kinky geometry. A couple of examples from the very clever Union Tool (Japan) range are: straight endmills from their CPR range, ball endmills from their CPRB range. Mostly they suggest water/soluble oil coolant. In their 2003 catalog you can find these tools on pages 102+ and 180+ respectively. Such tool geometry is also cool for aluminium and for plastic rib slotting. OMG I spelt aluminium in UK English! I'm slipping. If you can't get that catalog, try MEGATOOL INC. 6955 Aragon Circle, Buena Park CA 90620, Tel 1-714-521-6242 who are the USA distributor. And feel free to email me. Union Tool rocks!

[JFettig]

Thats definatly way too fast for copper, with a regular 1/2" EM in copper I would be taking light cuts at about 4ipm and 2000rpm. and yes, its probably right2ipm is probably about good for it.

I have actually not had much problems with copper, just use proper coolant and lubrication and you should be good to go, I have done a lot of copper work in my days, most of it with 1/16" end mills and only broke one. broke a few 1/8" end mills though

Jon