On Tuesday 25 March 2008, Gary Fixler wrote: >> One of the reasons I often drill a useless hole someplace at the start of >> the >> project, and write my code with that as the 0,0,0 point. That makes >> getting >> back to within a couple thou a bit easier. > >That's a great idea. I would love an absolute positioning system - something >that was always the same for the mill, at least between full strip-downs, >and rebuilds. > >Definitley test the ones you are going to use, & if its not up to that sort > >> of >> music, there's always that 45 gallon roughneck cannister just outside the >> door to store it in till the truck comes by. I'd run these on a bit less, >> but that is what happened to be available. > >One of the reasons I've been out of the list since last week was that I was >running my first intricate project, at least for me. It's a very simple >thing - two rings cut out of 1/4" aluminum to raise my coworker's Jeep >suspension by that much, but the ID needed to be radiused, and as they were >too big for my mini mill, I had to design the code to work by moving the >rotary table diagonally, doing the radiused hole with diagonally-incremented >steps, which makes all the radii actually the inverse of the square root of >2 times those radii, used to offset both X and Y. I got it all right, but it >kept failing. I finally did a full strip-down of the mill, polishing away >all rust on my Z column with a Dremel polisher, and recalibrating >everything, especially with the help I got in here to get values dialed in >properly, and the parts came out great. > >Back on topic, I could definitely have used some cooling. I can only dig >through aluminum in 0.001" vertical increments, without stressing things, or >tearing apart my clamping assemblies, so it takes forever.
.001"? Ouch. If I watch the feed rates, my micromill will cut the alu I have at .5" deep while moving against the side of a 1/4", 4 flute TiN plated carbide bit, but more like .010" at decent feed rates in the 10 ipm range. But for plunge cuts with std end mills, it seems to take some sideways motion too.ATM its busy taking .190" off the top of a 3x5" piece of alu, at .005" per pass and feed rates of about 7ipm. I can go faster, but the darned screws start squalling and they are up to their collective chins in oil, so its slow going for that much, so it will be about 2am to complete. The shavings, when its working against the side of the bit at a .050" minute feed rate, are very dangerously thin and sharp, I've picked many of them out of my hands. I was cutting the slots for the holddown bolts when I was doing that this afternoon. What its doing right now, with the spindle at maybe 300 rpm, is rooting through all the swarf its already cut, but that pile of swarf has a couple of tablespoons of cutting oil soaked into it, and the finish when brushed clean is quite good. The oil not only keeps it from piling up on the bit, it helps to seal the alu against atmospheric oxygen, so alu oxide doesn't form near as fast and bits stay sharp many times longer if they don't have to cut that oxide film everytime a flute comes by. Alu oxide is the second hardest substance, second only to diamond. Without that oil, the oxide film re-forms less than .001 seconds behind the edge of the bits exposing it, alu is a VERY reactive metal. With the oil wetting everything, the reaction is slowed quite a bit, not stopped, but slowed. But the Z axis on that micromill is my own design, see it at <http://gene.homelinux.net:85/gene/emc> that is a 425 oz/in motor on the Z, and I can run the bathroom scales up to 155 pounds under the spindle before the motor slips a cog. I can drill a 1/4" hole in steel 1/4" thick without using a peck cycle, just set feed to about .5" minute, spindle to a couple hundred revs and tell z to go down to the desired depth. Those pix are somewhat dated, the keyboard shelf is now bigger, there is a sheet of acrylic between the machine and the computer stuff, and a box with the spindle controling stuff in it is now mounted to the clean side of the plastic just above my standing line of sight, right behind the strut holding up the front of the keyboard shelf. And the strut has been pulled toward me about 5" from where it is in that dated pix. That big black UPS up on the shelf with the cpu now has its own shelf up on the ceiling beams a couple of feet out of sight. >The weather had >turned that day toward summer-like, and I had the mill's motor, 4 steppers, >and a shop vac going for 8 hours! It got really hot in that room, and I >couldn't even touch the motors. I'm actually thinking of running some pipe >from the portable A/C unit in the next room into the mill enclosure I'm >building, because putting it in a box like that will only make things worse. > >> Watch your store bought cabling for the parport, make sure the cable you >> use >> actually has all 25 wires in it. > >Will do! Thanks for the tip. I have a knack for excitedly running home, only >to find I've gotten the wrong part, or cable. It can really ruin an evening. Been there, done that, bought the beer even. >> >There's never nearly >> >enough time in a day, or a weekend. >> >> Chuckle, heck, I'd be happy to have enough time to get what I want to do >> done >> before I fall over. I suspect my plans will outlast me, diabetis >> beginning >> to slow me down, darnit. I hate unfinished business. :) > >No talking like that! I just got here! You have lots of work left to do, >teaching us newbs how to not lose our fingers, and such :) I'll leave that to the guys who wrote this software, a right sharp bunch of guys. Basic safety goes a long ways, particularly around BIG iron, which this machine isn't, but that doesn't mean it hasn't drawn blood by an accidental brush of the back of the hand against a stationary bit above the workpiece, those carbide bits are SHARP. Besides, they are, generally speaking 10 to 45 years younger than me. At 73, I think I qualify for the old fart designation. There is 2 or 3 of us in that category I think. -- 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) "You're a creature of the night, Michael. Wait'll Mom hears about this." -- from the movie "The Lost Boys" ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
