[Lab] first try at cutting aluminum

[aaron at ottawarobotics.org]

First things to check is whether or not you have a nice sharp bit.
That can cause troubles. 

The next is to make sure you have the right
feed and rpm for what you are up to. That is all related to your milling
bit diameter and the number of flutes. 

For instance, a 1/8th endmill
with 2 flutes should be around 7640rpm and you can run at 76.4 inches
per minute. A 4 flute can run twice the speed (152.8 inches per minute)
because the flute can carry twice the number of chips out of the cutting
area. As you move up in endmill size, the rpm and ipm drop in half, so a
1/4" mill can run 3820rpm and 38.2ipm. That is all assuming that you can
enough torque and speed in the steppers and the milling head. 

The next
thing to worry about is removing the chips. If you leave alot of chips
in the channel that you are cutting, the milling bit ends up having to
'recut' those and that can cause everything to gum up. Vacuum or blow
the chips out of the way as you are running is the best bet. 

The final
thing you need to worry about is your cutting tool flexing. Once you
start to flex it, not only does your cutting path go wrong but you'll
likely end up breaking it. Bigger diameter tools are stiffer so they can
take deeper cuts. If you are using a skinny tool and have a couple
inches hanging out under your milling head, it will flex and cause
troubles. 

All that being said, I run at 15 IPM for aluminum with a
1/4" mill and 25mil cuts. Works ok. When I go to smaller milling bits, I
actually reduce the speed down to around 5ipm just to make sure that
poor thing isn't flexing. 

Aaron 

On Sun, 29 May 2011 11:14:21 -0400,
Darcy Whyte wrote: 

> I tried to cut aluminum for the first time last
night. Pictures of the results here
http://mambohead.com/2011/05/first-try-at-aluminum-with-cnc-mill/ [1] 
>
I think I had the feed rates wrong. Anybody have any idea why the
endmill gummed up?

  

Links:
------
[1]
http://mambohead.com/2011/05/first-try-at-aluminum-with-cnc-mill/
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