Let me preface this hy saying that my machine was also due for its 100k mile checkup, so in the process of this mornings checking, I had to take up the gibs by a couple thou all around as I found I could grab the X table and slam it around the Z axis by a good 10 thou, so a good squirt of Vactra on the ways, and take up all the gib screws with a smallish screwdriver & tighten the locknuts w/o any backoff was done. The table feels pretty solid now and I can powerdown the motors and turn them by hand without any noticeable excessive drag. The x motors coupling locking setscrew was coming loose, which caused a dry rattling sound at certain speeds, and using the dial indicator, a Grizzly Presidents special to re-adjust the ini files backlash settings, I think I am in decent shape for the shape any HF micromill can be. The screw bearings on the end of the table have had small holes drilled into the bearing bore and a grease fitting installed, also pocketed on both faces for a teeny ball bearing thrust washer that reduced the drive load quite a bit, and because they are relatively hard, backlash once set there with a slight preload, is all in those pissy split nuts that are the backlash wear adjusters. They can't be gotten below 2 thou without huge drags on the screws until they wear back to around 3 thou.
1. I had to reduce the TRAJ MAX_ACCEL from 3.0 to 2.0 in order to get a reliable x table move start when that extra length x table is as far right as it can go without losing the screw out of the nut. That puts about a 30 pound out of balance on the X table as the motor is on the right end. 2. at no time did I find evidence of skipped steps. The only noticeable errors were when it was moving wide open and overshot the backlash getting stopped, slow it down, move 10 one way & back and it was dead on. 3. That Presidents special dial indicator is a POS, no screw can be so bad as to be out by 3 thou at 25 thou, and be back exactly on at 50 thou, one full turn of the screw. But for full turn moves (of the dial, 2 turns of the screw) it appeared to be very repeatable. What can I say, it was a 30 dollar, with magnetic base and positioning bars gage. 4. I have come as close as is practical at making a silk purse out of this sows ear. Only by putting in ball screws could I make it any better, and that would triple the cost of the machine. If I was to do that, I may as well drive up to Grizzly, about 6 hours each way. spend 3.5 grand & change for one of their X3 relabels along with new tooling and another grand on ball screws, exchanging an 80 pound machine for a 680 pound machine. And I still would not have an x table long enough to do a gunstock in one mounting between centers of a rotary table. 5. I need to get a cheap fan to blow on the drive box, after about 2 hours of playing, it was IMO too warm for good life of the electrolytic caps in it. I believe these MM-542's, and likely its bigger brothers that go up to 80 volts and 7 amps or so, will be usable stepper drivers, and at a reasonable cost premium over the xylotex & hugely better than anything running on the L298's. When I was all done, I set the feed overrode to 150% and ran the axis logo in 4:05. For that machine, I think that is quite decent. 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://204.111.66.235:85/gene/> Don't feed the bats tonight. ------------------------------------------------------------------------------ Doing More with Less: The Next Generation Virtual Desktop What are the key obstacles that have prevented many mid-market businesses from deploying virtual desktops? How do next-generation virtual desktops provide companies an easier-to-deploy, easier-to-manage and more affordable virtual desktop model.http://www.accelacomm.com/jaw/sfnl/114/51426474/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
