On Friday 16 February 2018 00:09:14 Chris Albertson wrote: > On Thu, Feb 15, 2018 at 8:06 PM, Gene Heskett <ghesk...@shentel.net> wrote: > > On Tuesday 13 February 2018 20:04:27 jeremy youngs wrote: > > > I had to service this motor today, as a previous technician had > > > improperly installed the brushes and it would are off at speed. In > > > doing so I removed the tach cover and found plenty of room for an > > > omron encoder. So I will not likely try these for spindle encoder. > > > But will be putting them in as home switches soon. > > > > > > Gene, you are absolutely right about the optos, the strongest and > > > best these have performed today after I replaced the bob to a > > > straight through board. However, I discovered my y axis ballscrews > > > is bent. > > > > Ouch. Time to do it right. But how the heck did it get bent? I'd > > find out why, and fix it. > > If you have a massive machine and a powerful motor the motor can > accelerate and produce a large force. > The ball screw is no different from any other steel column and based > on the ratio to length over diameter will buckle if enough force is > applied. In other words nothing has to be broken to bend a ball screw. > OK the CNC controller has the maximum acceleration set to high. To > protect the ball screw the acceleration has to be limited based how > far down the screw the nut is. From a mechanical engineering point > of view a ball screw is simply an unsupported column. > > The force on the screw might be much more then the weight of the > machine.
I'd submit that the screw was originally too small for the job. A Y screw in the context of a milling machine, usually has only the table and its mounted mass to deal with and the weight is handled by the ways. If it was under a half ton of knee, I could see it being stressed, but in that case I'd expect to see nut damage before it bent. But pix of the machine I haven't seen, so all this is idle assumptions on my part as I may not have a good image in my mind. Thanks Chris. -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
