On Tuesday 21 February 2017 10:34:30 Todd Zuercher wrote: > I am a wood worker in a large wood working CNC shop. But I need to > mill some aluminum for a project (a jig for another process in our > company) but I know next to nothing about milling such material. What > I need is to cut a large grid out of a 5ft x 10ft sheet of 1/4inch > thick MIC6 AL. The machines I will have to do this are large wood > working cncs with flat vacuum tables. We normally cut flat sheet > material like MDF or plywood on a MDF fall-board (vacuum sucking right > through the fall-board (holes, no jig tape, just porous MDF) These > machines have no provisions for coolant Just compressed air blast and > dust/chip collection (big centralized dust collector system). I will > obviously have to disable the dust collection, because I'm pretty sure > the local farmers who pick up our dust won't appreciate AL shavings in > their cow bedding. The machine I am probably going to use has a 12kw > 24krpm spindle. I would like to mill this with a 1/4" 2 flute carbide > end mill. Should I use an up o r down spiral cutter? What feed speed > and RPM would be appropriate? What depth of cut per pass? Do I need to > arrange some sort of mist system for cooling? What to use and how much > liquid in the mist? (Don't want to cause problems with the MDF > fall-board or vacuum hold down system.) The grid is only going to be > about 2 inches wide, with 12 windows in the 5x10 frame (a lot of > wasted material). At this point the plan is to set the milling up with > lots of bridges to hold the grid to the scrap then go back and trim > those off with a final finish pass.
You won't need that much rpm. Figure your speeds & loop decrements for a chip per cutting edge pass of perhaps 15 thou, cutting maybe 1/8" deep per loop unless the stickout is low. That much alu removed will pretty well finish a 1/4" TiAN coated tool unless some lube provision is made. If you can arrange a mist of cooking ( I've used safflower seversal times) oil so it hits the tool, that will help seal the alu from the oxygen in the air which forms a film of alu oxide, 2nd only to diamond in hardness (in about a thousandth of a second, alu is a VERY active oxidizer when exposed to air, but the resultant oxide film seals it up slowing the reaction rate by many magnitudes) and which the next cutting edge approaching must cut thru, resulting in much longer tool life and a 90% reduction in the generated heat, a huge percentage of which is not cutting friction, but the aluminum surface burning as the air gains access to it. The mister should be starved to an ounce of oil an hour, which will coat the alu and tool but shouldn't damage the MDF underlayment on the table if a vacuum is placed to suck up the cuttings. Generally, you want a cutting thick enough to carry away the cutting heat. A finish cut of .001" to pretty things up is the hardest on the tool cut you can make. And always climb cut. Dig cutting accelerates tool wear, a lot. Thanks Todd. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
