At 05:02 PM 6/21/2013, you wrote: >I'm thinking about converting my jet jmd-18 mill/drill with round >column, but thing that worries me the most right from the start is, >if Z axis would be accurate enough. > >There is one solution by reversing quill spring so it is forcing >axis all the time downwards and this way you get rid of backlash on >worm gear, next thing is how solve problem with quill lock, which is >meant to be used when quill is in desired position (height) so you >lock it to increase stiffness (and accuracy) on Z axis. >So did anyone here did any similar conversion and have a solution or >suggestion for this? > >here is machine's pic: >http://www.rustan.ru/sites/default/files/JMD-18F.jpg
I cnc'd my RF31 about 13 years ago and had the same concerns as you. Instead of reversing the spring, I got rid of it and replaced it with a needle thrust bearing and a cap to keep the pinion shaft from moving in and out (yes, it did and cause some problems as it allowed the worm wheel ride up and down on the worm enough to break the worm wheel) and put a counter balance on it to maintain tension. Then on the right hand side, I loosened the two socket head screws that holds the fine down feed housing to the head and gently tapped the housing to make a tighter fit of the pinion shaft to the rack (be careful as you can do to much!) and finally, as I put my servo on the fine down feed shaft, removed the chrome bezel and made a proper sized spacer that is held in by the plate for my servo motor to rigidly locate the worm shaft so it could not move in and out and again contribute to backlash. OH and the quill lock is in a drawer someplace. The servo maintains proper height. Has worked well for me all these years! Art Country Bubba > >------------------------------------------------------------------------------ >This SF.net email is sponsored by Windows: > >Build for Windows Store. > >http://p.sf.net/sfu/windows-dev2dev >_______________________________________________ >Emc-users mailing list >Emc-users@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
