Yes, near the limit switch, outside of the normal travel area, I can not measure any backlash. That pretty much points the finger squarely at wear on the screw as the main culprit. I think I have figured out the "springy" backlash uptake mystery. It is simply the weight of the screw sagging down and resting on the nut pushing the table to the center of the ball grooves (remember the screw is more than 14ft long.)
Anyone know of any good ball-screw refitters in the States? I already checked with one and they didn't want to touch it. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Stuart Stevenson <stus...@gmail.com> Sent: Monday, April 12, 2021 11:12 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Worn Ball Screw? [EXTERNAL EMAIL] Be sure links are safe. Plus or minus .010 is an amazing amount. Also, you mentioned another area on the screw you saw .001 lost motion. This leads to a screw problem. I would do what Jon Elson says as this sounds strange but I would expect to find screw wear. If it was nut wear the backlash in all areas of the screw would be close to equal. Not knowing the drive train maybe there is a gear train and one area of the gear train has worn teeth and where you found almost no lost motion is where the gear train is the best. Expect screw wear but hope for a gear train problem. HTH Stuart On Mon, Apr 12, 2021 at 5:15 PM Jon Elson <el...@pico-systems.com> wrote: > On 04/12/2021 09:48 AM, Todd Zuercher wrote: > > Those here who have had to deal with a worn out ball screw. > I'd dig into the works and examine everything. It does NOT sound like > simple wear. > The rotating nut likely runs in a pair of either angular-contact > bearings or tapered roller bearings. There will be a preloading > arrangement to constrain the nut. Also, the screw is usually fixed at > both ends. If the clamp has gotten loose at one or both ends, it > could allow some flex of the mount under load. Attach a dial test > indicator to the slide and read against the end of the screw, and > watch for movement when you apply load. > > Some old ballnuts were actually TWO completely separate nuts that were > preloaded against each other with Belleville washers. It is possible > some of the Bellevilles have cracked. > Also, they often used dowel pins to align the two nuts rotationally. > If one of the dowels has cracked, that could cause this kind of issue. > > Jon > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Addressee is the intended audience. If you are not the addressee then my consent is not given for you to read this email furthermore it is my wish you would close this without saving or reading, and cease and desist from saving or opening my private correspondence. Thank you for honoring my wish. _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
