hmm just read the link again to the example posted further up the email chain
yeah it's going to a sum component ok i understand this i think i will try hopefully in a couple of weeks cheers Andrew On Sun, Jan 4, 2026 at 6:29 PM andrew beck <[email protected]> wrote: > 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
