Homing fail

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  • #1956 Quote

    Hey! I just finished assembling my Thor arm, everything works just great, however whenever I try to home I get a small movement in the 2nd articulation, followed by a full stop and a “ALARM: homing failed” alert.
    I have my endstops and everything properly installed and connected to the board. Any ideas about how to solve this issue?
    Thanks a lot!
    Here’s the gcode log after I try to home:
    >>> $H
    ALARM: Homing fail
    Grbl 0.9j [‘$’ for help] ‘ – Thor Version 1.0
    [‘$H’|’$X’ to unlock]

    #1957 Quote

    Sorry for hasty question, managed to solve it by changing the $5=1 value to 0. I guess different optic limit switches were used in the original build. Works flawlessly now. Will post a video of the robot soon!

    #1958 Quote
    Angel LM
    Admin

      I’m glad to know you solved it very quickly!

      I can’t wait to see the robot in motion! πŸ˜€

      #1962 Quote

      Angel hey, for some reason when I post a youtube link of the test video I shot for you, the message disappears. Is there some sort of an automatic moderation system enabled on the board? πŸ™‚

      #1965 Quote
      Angel LM
      Admin

        It should be fixed now, can you check it please? πŸ˜€

        #1959 Quote

        Hey Angel! Super nice to meet you, was building your robot for the last 2 weeks, now it’s so cool to talk to you at the end. πŸ™‚
        Just uploaded a quick test video for you: https://www.youtube.com/watch?v=O9H95x67o0E

        I had a few quick questions in the video, any suggestions about those would be very appreciated.

        Btw, I’m actually building the robot for an episode on my YouTube channel, hope that’s fine (of course the project page is credited in the video, and the links will be in the description πŸ™‚ ).
        In the channel I build robots and stuff, it’s in Turkish though but here it is: https://www.youtube.com/hallederiz

        #1967 Quote
        Angel LM
        Admin

          OK, it seems that was pending of my approval because of the URL inclusion… But it never notified that to me hahaha… Now users should be able to post links without me having to approve them all.

          #1968 Quote
          Angel LM
          Admin

            Regarding your video, woah! Your “fat” Thor looks amazing! I can’t really notice visually the difference of the added width in the pieces, but if it works it works!

            I’m not really sure about how it could be managed, but it would be nice to have your redesign available for other people in the same situation of being unable to find the steppers I used. Maybe you can do a fork in GitHub? Let me know if you like the idea!

            About your doubts:
            1. Yes, the zero position of Art56 is close to the endstop. I have to admit that it’s a bit confusing because real robots have the zero position in the most extended position… Maybe is something to add to the To-Do List hahaha.
            And, to be correct, it only does the home of the 5th articulation. I didn’t find an easy way to find the home position of Art6, so I do it manually :/
            2. About the stability of articulation 4… Yeah, it’s a known issue. I had to print several times the pieces that forms the bearing to get a close adjustment, and even with that it has a little play… In the endless To-Do List is noted to substitute that “custom” gear with a commercial one. Years ago, when I designed the robot I didn’t find a cheap bearing that could be fitted in that articulation, but recently I think I have seen some plastic bearings that could be used for that task.

            By the way… What a workshop you have! What envy! And that Iron Man armor… what a blast!

            I don’t know turkish, but you have a new subscriber! Can’t wait to see more videos! πŸ˜€

            PD: Whenever you want, post an image of your Thor, a location and an url to add your creation to the Worldwide Section πŸ˜‰

            #1969 Quote

            Hey Angel!

            Thought the URL was the issue!
            Glad you liked the workshop and the channel. I’ll have english subtitles to my videos soon.

            My 5th articulation also has a homing issue. It always homes to a different (sometimes 20-30 degrees off) angle. I believe it might be because of the wiggling that causes the optic endstop disk to give false positives, would this be a correct guess? I’m trying to hotfix this to finish the video, for now I just manually move it after homing.

            I was doing the exact same thing you suggested for the 4th articulation, I started printing multiple versions of the inner disk of the bearing by slightly scaling it up to see which one will fit the best with the plastic balls, glad to know I’m on the right path.

            About the 5th and 6th articulation, I started imagining about a system where we could simply switch to a single stepper for the 5th (using a 10 to 20 pulley maybe?) and smack a servo to the middle of the Art56MotorCoverRing for 6th. This way 5th would be more stable and still can home, and you wouldn’t need to home the 6th since it’s now a servo. It would also decrease weight from the tip of the arm. It would only require changing a few of the parts in that module, so I might try this design at some point. If it works I’ll just fork the github and add all of the mods with the name Fat Thor. πŸ™‚

            I’ll definitely post it for the ww section once it’s complete.

            #1970 Quote
            Angel LM
            Admin

              How could I not like your workshop?! It’s like a dream come true for any maker! hahaha

              My 5th articulation also has a homing issue. It always homes to a different (sometimes 20-30 degrees off) angle. I believe it might be because of the wiggling that causes the optic endstop disk to give false positives, would this be a correct guess? I’m trying to hotfix this to finish the video, for now I just manually move it after homing.

              Do you mean the 4th Articulation? I had some issues with optic endstops until I painted the optic disks using black nail polish. These pieces were so thin that even though I printed them with black filament, at some points the light beam of the sensor managed to pass through the piece, causing some bad hommings. I think this issue is documented somewhere… Could be your case maybe?

              About the 5th and 6th articulation, I started imagining about a system where we could simply switch to a single stepper for the 5th (using a 10 to 20 pulley maybe?) and smack a servo to the middle of the Art56MotorCoverRing for 6th. This way 5th would be more stable and still can home, and you wouldn’t need to home the 6th since it’s now a servo. It would also decrease weight from the tip of the arm. It would only require changing a few of the parts in that module, so I might try this design at some point. If it works I’ll just fork the github and add all of the mods with the name Fat Thor.

              Sounds like a good solution! I hope to see that design done someday! πŸ™‚

              #1971 Quote

              Ah yeah, I meant 4th. I actually did see it in the documentation and black sprayed all the optic disks. Maybe the spray was not enough, I’ll try the black nail polish too, thanks a lot!

              For now to avoid homing I made an arm rest for the robot, uploaded it to thingiverse: https://www.thingiverse.com/thing:5401543
              It acts as a manual way to home it when it’s powered off, also keeps things safe and makes it easy to change the tool. Btw in the photo on thingiverse you’ll notice a revopoint 3d scanner attached as a tool. I wrote a sequence that scans someone with multiple passes when they sit in front of the robot, then turn it into an stl file. This robot is super fun. πŸ˜€

              #1973 Quote

              An update: I upgraded the 4th articulation bearing. I just printed a few differently scaled versions as mentioned, picked the smoothest one and added tons of lithium grease between the balls. It now works like a charm. I also did paint the optic disk with some different paint and now it homes perfectly. I don’t know if it was because of the earlier bearing (it was wiggly) or the paint, but finally I am a proud owner of a fully functioning Thor. ^_^

              #1974 Quote
              Angel LM
              Admin

                The arm rest piece is a clever solution! How the robot not slide when it powers off? Rubber/foam material?

                It would be awesome if you can share with us a video of an scan using Thor! Sounds cool!

                I’m happy to know that the 4th articulation is now homing perfectly, I’ll be watching your videos to see what applications you find for the robot!

                #1978 Quote

                Hey Angel,
                I actually adjusted the height of the arm rest and screwed it to the table in a position where the 2nd articulation reaches its end position, therefore that does’t slide and the 3rd articulation gently rests itself on the arm rest. The 5th articulation also rests on the extra piece you can see in the arm rest 3d model. I also added some foam to keep the arm from getting damaged.

                We did shoot lots of scenes with 3d scanning (I’ll let you know when we release it), but I also shot this short one for an IG story: https://drive.google.com/file/d/11E_QGewPlNFAE_KbJFsMGeHSOL92cF64/view?usp=sharing
                Moving the arm very slow using G1 commands when scanning, so the scanner can keep up. πŸ™‚

                Btw, I’m sometimes having a trouble with the articulation 2 skipping gears (when moving downwards). The driver vref is finetuned, shaft lengths and the gear positioning looks fine. Currently lowering the max feedrate of that articulation to find the sweet spot. Have any other recommendations to help me fix it?

                #1979 Quote

                Edit: Solved it by printing slightly larger gears (*1.05)

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