Hi Bushflyer,
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Are you roughing or trying to get a decent finish - there's quite a difference between the two I've found.
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For roughing I am using mostly a 6mm single flute carbide end mill using 16,439rpm and somewhere between 550 and 650 mm/min - when this is right and the tool is sharp its almost noiseless when roughing through 6082 T651. The lower feed rate seems to be better when the tool is slotting (6mm width) and higher when running at my normal 45% step-over. Also that's all at 2mm DoC - I've tried deeper at 3mm which is OK'ish and much deeper at 5mm but the latter was shrieking.
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I'm using GWizard, which now has a gantry router setting and this is on either the 2nd or 3rd setting (highest kills tools and lowest is resulting in "rubbing" i.e. there's a lot of crap not being cut and being "pushed" out of the way.
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Finishing paths are a different ball game as the very low "step overs" mean you can get chip thinning i.e. heat which needs getting rid of and also means high feed rates (3000mm/min+) and if that runs into a slot condition goes bad very quickly.
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Hope that helps and I'm always on the lookout for experience in this, as getting in the "window" of feeds and speeds means the difference between nice, acceptable and ruined parts - especially with gantry routers.
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Oh also a misting/flood system is a must IMHO for aluminium, as is paranoid blowing out of chips with compressed air - I have had everything cooked right before and snapped a tool just from clogged chips in a slot before.
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Hope that helps.
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Chris
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PS. See my Youtube channel for some examples of pocketing 6082 T651.