#linuxcnc Logs

Jul 06 2025

01:39 AM Deejay: moin
02:57 AM pere: Hello from the LinuxCNC gathering in Norway. :)
05:41 AM Tom_L: morning
05:57 AM lcnc-relay: <travis_farmer@> Morning
06:41 AM _unreal_: ARG.... I dont want to but I'm going to have to put all my epoxy under a tarp in the yard...
06:43 AM _unreal_: I have no room in my garage. In the end it wont be an issue and in the back yard. The problem is that I need my trailer that I want to store it in still has work to moving stuff from storage to my home
06:43 AM _unreal_: :(
06:43 AM _unreal_: just cazy how much I have
06:43 AM _unreal_: mostly tools at this point
07:16 AM -!- #linuxcnc mode set to +v by ChanServ
07:21 AM lcnc-relay: <sodakaustik@> why does linuxcnc use a pid loop for open loop position control
07:22 AM JT-Mobile: morning
07:22 AM lcnc-relay: <sodakaustik@> cant i just feed a ramped position target stepdir to the drives?
07:22 AM lcnc-relay: <sodakaustik@> norning
07:23 AM JT-Mobile: for Mesa stepper drives there's an advantage to use pid
07:23 AM JT-Mobile: but I forget what that is
07:25 AM lcnc-relay: <sodakaustik@> im using AC servos
07:30 AM JT-Mobile: https://forum.linuxcnc.org/38-general-linuxcnc-questions/35415-what-does-pid-mean-for-open-loop-steppers
07:30 AM JT-Mobile: see Peter's reply
07:34 AM lcnc-relay: <sodakaustik@> i see
07:34 AM lcnc-relay: <sodakaustik@> then why do i get huge following error
07:35 AM lcnc-relay: <sodakaustik@> the drives have 100% feedforward and behave perfectly according to what is given to them in terms of pulse frequency
07:35 AM lcnc-relay: <sodakaustik@> but alas, threading is an issue if i want to change rpm
07:36 AM lcnc-relay: <sodakaustik@> say i go from 300 to 500rpm during a threading operation, i can see the cutting edge lag by an additional 2mm~
07:36 AM lcnc-relay: <sodakaustik@> this is easily fixable by "just dont change rpm during threading"
07:36 AM lcnc-relay: <sodakaustik@> but i get the sense that its just not right
07:39 AM lcnc-relay: <sodakaustik@> i have no feedback, no linear scales and no encoder output from the drives
07:39 AM lcnc-relay: I scope them directly through their own software and get beautifully tuned graphs, following error is very very low and pretty much none at a steady velocity
08:02 AM _unreal_: I'll be moving my end mill and metal lathe to the house maybe this week
08:02 AM _unreal_: the lathe. my "friend/former business partner" really screwed it up. got a bunch of repairs to do. The endmill he created some minor damage :/
08:03 AM _unreal_: mainly the buttons for the auto feed on the X axis.
08:03 AM _unreal_: Though I plan to CNC convert that mini endmill regardless
08:03 AM _unreal_: will be amazing
08:03 AM _unreal_: just cant wait to be done MOVING
08:04 AM _unreal_: I'm considering cnc converting the lathe as well
08:05 AM _unreal_: main issue with it IMO is that its got plastic gears for the travel arm AND its seized.
08:08 AM _unreal_: later
08:16 AM lcnc-relay: <captainhindsight_.@> Lunar: you asked about pid loops with open loop motors then state that you are using AC servos, what is your question to be clear?