hey stuart yeah the ballscrew is connected both ends. i think one end has the big angular contact bearings etc
and the other only has deep groove ends probably (its much smaller than the driving end) on my other two cnc mills they have angular contact bearings both ends and the screws are stretched between them slightly with a tiny bit of preload hey guys i was reading the link that sam sent two and it looks like the two Pid loops are running side by side and then the outputs are added together before going to the servo drive would i be correct in thinking that they are using the "sum" component in linuxcnc to do that? if so this is getting pretty simple cheers andrew On Fri, Jan 2, 2026 at 3:07 PM Stuart Stevenson <[email protected]> wrote: > HI, > I don't think the LinuxCNC control scheme is cascaded or nested. I would > call it parallel. > > The only backlash problem I can imagine is if the backlash causes the > motor to dither trying to maintain position because cutting forces move the > axis enough to cause the control to try to correct the axis position. > > Is the ball screw supported on each end? If it is, then, is it possible > the screw has some stretch preload. > > regards > Stuart > > On Thu, Jan 1, 2026 at 4:10 PM andrew beck <[email protected]> > wrote: > > > hey guys > > sam i just looked at that link you sent > > > > that looks pretty cool > > > > only thing is i don't know is if it will work to reduce the backlash > issue > > i am getting. I have about 0.10mm of backlash on each axis. half of > that > > is from the thrust bearings which is fixable with new bearings > > the rest is from the ball nut i think and i am not willing to fix that > > > > but i can only try it. > > > > does anyone want to have a go with making a config like they did? one > axis > > would be best I am struggling to get my head around the different > layers. > > i probably need to write it all out or use a diagram or something. > > > > regardless i am sure i will work it out. just might take some brain > cells > > > > > > > > cheers > > > > Andrew > > > > On Fri, Jan 2, 2026 at 4:54 AM Sam Sokolik <[email protected]> wrote: > > > > > This was also John k.. I would trust his solution. He is the one that > > > came up with hal in linuxcnc... (Among other things). > > > > > > On Thu, Jan 1, 2026, 9:49 AM andy pugh <[email protected]> wrote: > > > > > > > On Thu, 1 Jan 2026 at 15:41, andy pugh <[email protected]> wrote: > > > > > > > > > > On Wed, 31 Dec 2025 at 22:14, andrew beck < > [email protected]> > > > > wrote: > > > > > > > > > > > just looking for a config example if possible for a mesa card > from > > > > someone > > > > > > that has this nested PID loop setup. > > > > > > > > > > This may not be as effective as you would hope. Cascaded PID > loops... > > > > > > > > Actually, what was done with the MPM jigmill wasn't a cascaded PID. > > > > What was done there was to run a P + FF control based on the motor > > > > encoder and an I control based on the linear scales. > > > > > > > > Then the two controllers were summed together to create a PID > > > > controller, but with I using a different feedback source than P and > D. > > > > > > > > -- > > > > atp > > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > > designed for the especial use of mechanical geniuses, daredevils and > > > > lunatics." > > > > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > [email protected] > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
