On Tuesday 29 January 2019 21:34:57 Jon Elson wrote: > On 01/29/2019 03:27 PM, Gene Heskett wrote: > > Greetings all; > > > > I just found the only way to cut this panel alu is to keep the tool > > cold with a blast of air at around 125 psi blowing on the nut and > > tool. > > > > Anything less and the heat telegraphing down the tool from the > > motors front bearing, combined with the alox formation and friction > > gets the tool so hot it burns the cutting oil away and welds the alu > > into the flutes of a 4mm coated SC tool. Hell to pick it out. > > My idea of how to work aluminum is to take very light > depth/width of cut, and keep the cutter moving along at a > high feedrate, to prevent the heat from building up at one spot. > I can't believe the spindle bearing is heating up the > cutter. If so, then the bearing has already burned out. > But, aluminum gets hot from the cutting action (supposedly > there is heat generated by the "burning" of the freshly > exposed metal in air, too).
That is the majority of the heat generated when machining alu, and with a good misting system keeping the alu sealed away from the air by directing the mist into the cut, wetting it and sealing away the air as close to the cutters edge as the edges passes, this heat virtually vanishes. > But, I think it is just the > heat of cutting accumulating in the workpiece. Thats the show stopper, regardless of the src of the heat. > I don't have a 25000 RPM spindle working here, so am > unfamiliar with the actual numbers, but you want very small > chip/tooth numbers, like .0001". This will eat up your > cutter faster, it can handle a LOT more chip/tooth, but the > heat has to be dealt with. You should be running at a > feedrate of 20 IPM or so, or faster if you can. 25 to 40 ipm, and .008" to .010" incremental depth of cut since it goes clear thru the panel. Effective stepover can range up to the diameter of the tool and in this case usually is. That means it will dwell in the hole for up to 8+ revolutions around the hole leaving a stem in the middle. I think the next panel I cut, since I'm making 2 of these, may get cut at a greater depth of cut just to cut away the heat faster. I seem to be polishing the bottom of the half finished holes, and unless I keep it really cold, I'm plowing up a fence 30 thou high both on top, and out the bottom of the holes so I've cleaned them up with a $30 step drill. And I have 4mm tools from two srcs now, so I might try the other for the next panel. Thanks Jon. > > I use water-based coolant, as I do aluminum almost > exclusively. That probably removes a lot more heat than an > oil-based coolant (or brushed-on cutting oil, for sure!) > > Jon > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
