On Thu, Dec 10, 2009 at 07:08:21AM -0500, Gene Heskett wrote: > 3. face up & making a sprocket, or lathe style & carving gears, backlash will > be a problem. So it may be wise to add a 2nd lock brake so that the table is > locked pretty solidly when the motor is not moving it. I'm still figuring > out how to do that with mine as it has a thumb screw with limited holding > power.
It was with some shock and disappointment that I discovered that my brand new several-hundred-dollar rotary table has backlash, even with the variable-engagement worm adjusted for maximum engagement. It has two locking screw-clamps, each with a short captive tommy-bar, but if EMC is to control them, then powerful pneumatic brakes and solenoid valves would perhaps be easier to control. Perhaps I should disassemble the rotary table, to check how hard it is to improve worm and wheel engagement so that both flanks make contact. (I'm still aghast that a reputable manufacturer doesn't achieve that, out of the box.) > <http://gene.homelinux.net:85/gene/emc/A-drv.jpg> > shows the motor mount I made for a cheap 4" Grizzly table. > > The coupling inside it is a heavy steel rig, two cups facing each other, with > 1/4" slots cut across, with a steel disk trapped in the middle which has a > 1/4" wide fin, laying 0-180 on one face, and 90-270 on the other so it > presents a sliding u-joint with very little backlash that can absorb the > axles being out of line a couple thou. That sounds a lot like an Oldham coupling, Gene. For the OP, there are some pictures here: http://en.wikipedia.org/wiki/Oldham_coupler One idea I'm considering is driving via a toothed belt, from a motor clamped nearby, in the T-slots. Just looping the belt over a pulley added behind the rotary table handwheel allows it to still be used manually, when it isn't worth mucking with gcode. Erik -- Ninety-Ninety Rule of Project Schedules: The first ninety percent of the task takes ninety percent of the time, and the last ten percent takes the other ninety percent. ------------------------------------------------------------------------------ Return on Information: Google Enterprise Search pays you back Get the facts. http://p.sf.net/sfu/google-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
