On Monday, February 13, 2012 12:40:45 AM Jon Elson did opine: > gene heskett wrote: > > Hi Guys; > > > > I just broke my last brand new 1/16th carbide end mill in about 15 > > minutes running time, a 4 flute with about 1/2" of working length, > > trying to get started on another alu encoder wheel, getting about 80% > > of the way around the outside, running at 2500 revs, and 1.5 ipm, > > cutting only .005" deep, running in a puddle of cutting oil. > > > > Obviously the 4 flute is a no-no in soft alu as it was pushing alu > > ahead of itself for 90% of what it did cut which tells me it was half > > plugged after the first 1/2" of feed in that heavy duty (0.0037" > > thick) coors can alu . Filled up the flutes nearly instantly even if > > it was swimming in cutting oil. > > > > So, I need to find a more suitable mill for this, I assume only 1 or 2 > > flute, and maybe only 1/8" of working bit. > > You ought to be able to do this. I use water-based coolant. The trick > is to keep the > WORK cold, and I do mean COLD where the cutting is going on. You should > up the feed rate and/or make it in several passes, stepping down in Z > each pass. > 1.5 IPM is way too slow. At 2500 RPM with 4 flutes, that is 10,000 > cutting edges > per minute. So, each tooth is only cutting .00015", which is WAY too > small. My McDonnell-Douglas slide rule suggests a .00062" feed per > tooth, so that would be 6.2 IPM. You should only plunge 1/32" per pass > with a 1/16" cutter (half the tool diameter). > > I use a 4-flute cutter in aluminum ALL the time, rarely use a 2-flute. > You should be climb milling, this causes much less rubbing and therefore > heat > generation. Climb milling causes the cutter to plunge directly into the > un-cut > material, conventional milling causes the cutter to slide across the > already-cut > surface until there is enough pressure to penetrate it. That rubbing > causes heating of the workpiece, which makes the aluminum soft. > > > Since I don't have a 10,000 rpm spindle, 2500 is it, what mill should > > I buy, and how fast can I feed it? Or am I doomed to go find some > > harder sheet alu that cuts cleaner and won't plug up a mill? > > Just keep it COLD, and it will cut fine, as long as it isn't 1000 > aluminum or > something meant only to feed into an extruder. That's the beauty of > water-based > coolants, the evaporation of the water really cools stuff off. > > Wait, you're only cutting .005" deep per pass??? WHY?
This particular sheet of alu seems to be dead soft. The chips it was making looked about the right size spinning around in the oil. I don't have water out there other than used. :) And no real drainage system exists although I have considered just setting the whole mill into a pan about an inch deep, if I could find a suitable pan. > I might tend to > go a bit less than half the tool diameter, but that is too conservative > even for HSS, and way too conservative for carbide. If you insist on > such small Z plunge, you should be cutting this at 20 IPM or something! > > I don't have much experience with 1/16" carbide end mills, but use > 1/8"carbide > 4-flute mills as one of my most standard cutters for .060 - .125" > aluminum panels. I frequently run a whole day on one cutter. And, I > do it usually at about 2800 RPM. > > If the wad of aluminum around the cutter develops, you are already sunk, > you have to avoid the softening of the material. Running under cutting oil, about 1/16" deep, is a shop that's showing 51F, really s/b cold enough. There was no heat or smoke, it simply stopped cutting and well before I could hit the button, it had bent about 40 thou and went ping, with no clue where it went. I was digging what was effectively a straight ahead ditch 1/16th wide, and at 5 thou deep, there are 30 thou fins sticking up all over what it did before the ping. I would probably be time & screwing around ahead of the game to see if I have a big enough piece left from the last brass door kickplate to make this. There's no reason I couldn't make it from a plastic, like formica, except that stuff is shipped rolled up and is not capable of ever being flattened again. I need flat stock that won't wobble. I cut the first one, whose slots it turned out weren't long enough, in a much harder sheet of alu, cutting in two passes all the way through a .0625 sheet, with an identical bit from the same order. But that is almost too thick for these opto's slots, hence the attempt to cut a thinner one. I have also rerouted the board to make it much easier to assemble, so I'll probably make another board which will allow me to stand the Z sensor high enough to catch the z slot in the outer rim, otherwise the hole circle is so small that when the A/B sensors are about right, the z sensor is completely missing the edge of the wheel, a good 1/8" outside of the Z slot. So I am gradually getting eagle figured out. Next board might be even better if I can keep a fine bead on Murphy. He and I know each other well, but that doesn't mean we're friends. :) Thanks Jon. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> Go directly to jail. Do not pass Go, do not collect $200. ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
