Gene Heskett wrote: > On Monday 24 November 2008, Andrew Ayre wrote: >> Gene Heskett wrote: >>> On Saturday 22 November 2008, Andrew Ayre wrote: >>>> Gene Heskett wrote: >>>> 30 IPM is an arbitrary value that I picked that I didn't feel >>>> comfortable going above. If I knew I could run it faster I would, but >>>> I'm just starting out. >>> One of the problems that pushes the speed up is that the cuttings are part >>> of the bit cooling, they carry away the heat. Cut too thin (on either >>> edge) and the bits get hot too fast. If you are seeing burns, slow the >>> bit rpms down, speed up the move, or replace the bit, its getting dull. >> This is an area I am still completely unsure about. I get chatter and >> nothing I seem to do helps. I've tried slowing the spindle down, >> increasing the feedrate, slowing the feedrate, etc. I guess it is slight >> runout in the spindle. > > The later dremels have an elastomer seat cushion for the spindle nose > bearing, > and its rather loosely coupled to the motor shaft itself. Another friend > made a new alu nosepiece with a precision seat for that bearing for his > dremel and it works much much better. Also, the last one I bought had a > seriously defective 1/8" collet, it allowed, and demanded, about a 20 thou > runout. I spotted a card of collets at Lowes, and a new one runs nicely.
I had the collet problem when I first started. Solved with a new collet. > There is, and I forgotten the name, a german maker of such goodies that is > very highly thought of, maybe someone will chime in with more details. I > believe its about the same diameter as the dremel, but an inch or so longer. I am planning on switching to a laminate trim router, perhaps by the end of the year. I just don't think a Dremel is up to the job. > I looked at that machine some time back and came to the conclusion it was a 6 > month machine. MDF warps over time when weight is applied, so I'd think it > would be hard put to maintain a flat bed over time. And 12x18x3 won't carve A slightly non-flat bed doesn't concern me too much right now. If needed I plan to skim the surface of a sacrificial bed every few months. I will likely do that if I switch to PCB milling, which requires depth precision. If you go to millpcbs.com the owner of the site is getting excellent results with an older FireballCNC machine, also made of MDF. > a gunstock, so I didn't persue it any farther. That would need 12x48x10 and > an A-B axis, the A to turn the stock on the x axis, the B to tilt the head > along the x axis so it could reach into stuff like thumbholes, which I'm > partial to. A is easy enough, but the B is a whole new design of the gantry > itself, which would gain considerable weight in the process. I have a mental > picture but haven't tried to draw it up in a CAD proggy yet. >> I've recently purchased a dedicated PC for EMC2 and I now have 2.2.7 >> running as of today. > > Great! Does it still do it? I'm not running the rapids at full speed, which is the only time the problem showed with pre-2.2 CVS HEAD. Are you saying that I should now be able to go at the full speed of my PC? >>>> X: 0.005375" >>> This could be adjust down I'd think. Wear? >> Not sure what you mean. It seemed to help quite a bit. See: >> http://www.britishideas.com/2008/06/19/measuring-cnc-backlash-and-software-c >> ompensation/ >> >>>> Y: 0.0025" >>>> Z: 0.0003" >>> Head weight is the preload? Not always realistic when pushing on a drill >>> bit to bore a hole. The hole won't be quite as deep as you told emc to do >>> in that case. >> Sorry, I don't know what "head weight is the preload" means. I'm still >> very new to this and I'm sure I'm doing a million things wrong. > > Well, your 'head' isn't nearly a heavy as mine. With mine, the whole thing > slides up and down a column that is (IMO) too slender, on a way sled that > really needs to be at least twice as long for good guidance. I'm probably > pushing 25 pounds up and down. But .0003"? That's almost magic unless its a > ball screw, preloaded to boot. My Z-axis weights perhaps 3 - 4lb plus the dremel. The 0.0003" was an average of several backlash measurement tests. There is no hardware backlash elimination. > Anyway, it sounds like you are making progress, Andy, which is good. > > > -- Andy PGP Key ID: 0xDC1B5864 ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
