On Wednesday 08 May 2013 09:36:18 kqt4a...@gmail.com did opine: > Has anyone any experience converting a Grizzly G8689 mini mill > > Richard > Not that one specifically, but I've done the micro-mill.
I made the motor mounts and all metal sliding joint couplings to connect nema 23 steppers to the x,y screws, mostly on my then manual 7x12 lathe. Its now LCNC'd too. Then I bought 2 more of the bearing hubs on the ends of the tables the screws run in and carved them back a bit to put small ball bearing thrust washers in each face which reduced the motor required torque by half or more. I also drill & tapped them for grease fittings. And somewhere along the line LMS sold me the bigger table kit for it. On those smaller mills where the Z screw is behind the post, don't waste _any_ time trying to motorize that, the Z ways are about 3" too short and the instant a drill bit touches down it will wedge itself to the post. I tried that, but 5 lbs on the drill bit was the best a 425oz motor could muster. Very bad design, and one that, given the tools to cut v-ways, will get fixed with a whole new slider to run up and down the post. Eventually. If I don't fall over first. Also, the pull handle to advance the spindle has been removed, and the draw bolt in the casting to adjust the tension on the spindle barrel has been pulled up tight so that doesn't move and screw up LCNC's idea of where Z might be. The rack and pinion that drives that is so sloppy with backlash I never considered trying to motorize that with its 1/16" or more of backlash. The only thing it was good for was to supply the push the Z screw couldn't when using it for a drill press In the meantime, I turned the gearcase 90 degrees to make some clearance between the case and the post, and drilled into the top of the casting and planted a 1/2 Acme thread bolt about 1.5 inches or so in front of the post and thereby reducing the tilt leverage by about 5", then made an assembly that is bolted to the sides of the post, holding a ball bearing nut carrier carrying two of the nook nuts so I can adjust backlash, with the whole nut assembly turned by a 425oz motor with about a 2.5/1 geardown via a timing belt. I can now put a bath scale under the head and push the down button and get 155lbs of push to drill a hole. But as its worn into the post, stiction seems to be the order of the day, so if I need to do a 1 thou down move, I pick it up 20 thou and set it back down 21 thou in G0 move. I can fix it for an hours or so by splashing the ways with Vactra and running it up and down to distribute it, but it may come back mid job so I've gotten into the habit of just writing the rapids moves into my code. There are some pix on my web page in the sig below, click emc link, somewhat old now, but they show how the rebuilt Z is made. As far as linuxcnc, and its interface, a cnc4pc C1G breakout board, a 28 volt 10 amp switchmode supply, and 4 2m542 drivers are all in one box on a shelf above. Box is mostly sealed against swarf, has a strong internal fan to move the heat to the box walls, and the box walls are then cooled with a muffin fan blowing across the top of it. I also have a 425 motor on a 4 inch el-cheapo rotary table. Mountable as A,B,C depending on what I am doing. Also, the circuit board for the speed control in the gearcase was removed because it was catching flying grease, and it and a PMDX-106 were built into a separate box so I have LCNC control over spindle speed and direction of rotation. 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> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> BOFH excuse #94: Internet outage A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. This 200-page book is written by three acclaimed leaders in the field. The early access version is available now. Download your free book today! http://p.sf.net/sfu/neotech_d2d_may _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
