On Tue, 2012-08-28 at 02:45 -0400, jeremy youngs wrote: > kirk the issue of this thread I have a very fine large matson mill ive > just conerted and I would like to reduce friction and I cannot afford > the 1500 bucks roght now for ballscrews it only has .005 backlash but > thats enough to screw my circles up even with backlash comensation .
(IMO, LinuxCNC's backlash comp is only useful if one can lock the joints after the move.) > So i am trying to get advice or methods that may help in the mean time I see it this way (thought stream ahead). I believe, even if you reduce the joint friction, you will still have backlash problems because the cutting action will pull the the joint until the nut's backlash is taken up. Moglice might be used on the nut to fill in the clearance, but in my opinion, the nut's bearing area is too small for the load to have the Moglice survive for very long. Ball screws are the only solution that have proven to be up to the task. Moglice has been effectively used in the restoration of joints, or rather, ways, but these have large bearing areas relative to the load. Plus, the surface the Moglice works on, still needs to be reasonably flat to prevent binding at the ends of travel. If backlash is a problem, one needs to reduce the backlash where it lives, either at the nut and/or the joint. If the lash is too high due to wear, the screw/nut or joint needs to be restored to new condition. Otherwise, binding will be a problem when the lash is adjusted out. If the new condition has too much lash, the design needs to be changed and the most common method is to use preloaded ball screws. For joints, more attention to scraping may help or going to a preloaded roller design may be appropriate. If your machine where in my shop, I would spend time with a dial gauge to figure out where the lash is (nut/screw, screw/screw end bearings/table, axis joint/jibs) and why it's there . For machines that where not designed for CNC, backlash is not usually designed out because the operator is expected to use techniques that avoid the effects by locking the joints for round features and such. So for these machines, a design change is most likely needed. If so, new designs will need to allow for bearing loads, speed, wear, contamination, temperature, lubrication, et al. After that, the issue is how to pay for or make it. On the other hand, I bough my CNC mill, nearly ready to go, for about the cost of converting my manual mill to ball screws (let alone restoring the ways), so looking for a different mill might be cheaper. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
