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    Oddly shaped holes?

    Scheduled Pinned Locked Moved
    Tuning and tweaking
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    • mrehorstdmdundefined
      mrehorstdmd @Surgikill
      last edited by

      @Surgikill As I posted above, clamping the bushings down a little tighter on the rod would help. If they aren't made to be tightened, cutting a slit with a saw will allow them to be tightened by modifying the clamps that hold them to have screws that let you squeeze the bushings a little tighter on the rods.

      https://drmrehorst.blogspot.com/

      Surgikillundefined 1 Reply Last reply Reply Quote 0
      • Surgikillundefined
        Surgikill @mrehorstdmd
        last edited by Surgikill

        @mrehorstdmd They're held on with zip ties, so not sure how well that will work. it could be a printer issue besides the gantry. I have a print running right now so I can't mess with it. I've attached a picture, maybe that will help.

        20200328_192249.jpg

        mrehorstdmdundefined 1 Reply Last reply Reply Quote 0
        • Phaedruxundefined
          Phaedrux Moderator
          last edited by

          Are those maybe the type of bushings that require a certain amount of compressive force on them to get them to fit properly on the rod?

          Z-Bot CoreXY Build | Thingiverse Profile

          1 Reply Last reply Reply Quote 0
          • mrehorstdmdundefined
            mrehorstdmd @Surgikill
            last edited by

            @Surgikill As you have discovered, zip ties are not a particularly good way to hold components of a precision mechanism together. I'd start with a redesign of the extruder carriage that allows those bearings to be securely fixed and also squeezes them down to fit the rods better.

            https://drmrehorst.blogspot.com/

            Surgikillundefined 1 Reply Last reply Reply Quote 0
            • jens55undefined
              jens55
              last edited by

              At minimum, I would add a rubber band and some nailing wire !

              (sorry, couldn't resist)

              1 Reply Last reply Reply Quote 0
              • Surgikillundefined
                Surgikill @mrehorstdmd
                last edited by Surgikill

                @mrehorstdmd Yea that's not happening. That is the redesign. I looked into bolting them on, and I lose a shitload of print volume, which is the whole point of this printer. I used the same design previously, and didn't have an issue. Also why I used 4 of them, instead of 2.

                It's also hard to see, but there is a cutout for the linear bushings to line up in. Those zip ties are only holding it in that groove.

                mrehorstdmdundefined 1 Reply Last reply Reply Quote 0
                • mrehorstdmdundefined
                  mrehorstdmd @Surgikill
                  last edited by mrehorstdmd

                  @Surgikill Then you're back to looking for rails that match the diameter of the bushings. Good luck- you're going to need it.

                  https://drmrehorst.blogspot.com/

                  Surgikillundefined 1 Reply Last reply Reply Quote 0
                  • Surgikillundefined
                    Surgikill @mrehorstdmd
                    last edited by

                    @mrehorstdmd They're 12mm rods. I don't think that's the issue. As soon as this part is done, I'll show it to you, but after loosening the belts up a bit I don't see the carriage wobbling anymore, but the artifacts are still pronounced, even on large circles (3" diameter)

                    jens55undefined JoergS5undefined 2 Replies Last reply Reply Quote 0
                    • jens55undefined
                      jens55 @Surgikill
                      last edited by

                      @Surgikill, picture ?

                      Surgikillundefined 1 Reply Last reply Reply Quote 0
                      • Surgikillundefined
                        Surgikill @jens55
                        last edited by

                        @jens55 20200329_002613.jpg 20200329_002555.jpg

                        @mrehorstdmd I might be able to use something like this. https://www.igus.com/product/1185

                        jens55undefined 1 Reply Last reply Reply Quote 0
                        • jens55undefined
                          jens55 @Surgikill
                          last edited by jens55

                          @Surgikill, I was looking for a picture of a round thing of 3" like you mentioned. Surely the first picture doesn't show a round object ... is it ? Sorry for not being clearer.

                          Surgikillundefined 1 Reply Last reply Reply Quote 0
                          • mrehorstdmdundefined
                            mrehorstdmd
                            last edited by

                            How fast do you print with that machine?

                            Maybe you should use the Igus rails that match the bushings.

                            https://drmrehorst.blogspot.com/

                            Surgikillundefined 1 Reply Last reply Reply Quote 0
                            • NitroFreakundefined
                              NitroFreak
                              last edited by NitroFreak

                              Carbon fiber rods aren´t precision ground sliding surfaces,
                              I don´t know who came up with that idea but it´s terrible. This will not last for any significant amount of time.
                              You may temporarily get less ringing, but so will upgrading the steel rods to a bigger size.
                              I would personally never use igus bushings or bushings in general because by design, they require a bit of slop / play that causes backlash.
                              An added negative is that the carbon fiber dust that will accumulate over time is REALLY bad for your lungs.

                              1 Reply Last reply Reply Quote 1
                              • Surgikillundefined
                                Surgikill @mrehorstdmd
                                last edited by Surgikill

                                @mrehorstdmd I was considering just grabbing some cheap steel rods to see if that fixes it. I don't print that fast right now, but the goal was to have a light carriage so I could up the speed. I was looking at Igus aluminum rods. Not sure if I should get those or the steel rods.

                                @NitroFreak said in Oddly shaped holes?:

                                Carbon fiber rods aren´t precision ground sliding surfaces,
                                I don´t know who came up with that idea but it´s terrible. This will not last for any significant amount of time.
                                You may temporarily get less ringing, but so will upgrading the steel rods to a bigger size.
                                I would personally never use igus bushings or bushings in general because by design, they require a bit of slop / play that causes backlash.
                                An added negative is that the carbon fiber dust that will accumulate over time is REALLY bad for your lungs.

                                Not really sure how I'm going to get carbon fiber dust. The bushings are designed to wear. Not the rod.

                                NitroFreakundefined mrehorstdmdundefined 2 Replies Last reply Reply Quote 0
                                • NitroFreakundefined
                                  NitroFreak @Surgikill
                                  last edited by

                                  @Surgikill said in Oddly shaped holes?:

                                  Not really sure how I'm going to get carbon fiber dust. The bushings are designed to wear. Not the rod.

                                  The bushings are designed to wear on STEEL rods, or their anodized aluminum rods. IGUS never stated a compatibility with carbon fiber rods

                                  Surgikillundefined 1 Reply Last reply Reply Quote 0
                                  • Surgikillundefined
                                    Surgikill @NitroFreak
                                    last edited by

                                    @NitroFreak Igus sells carbon fiber rods.......

                                    1 Reply Last reply Reply Quote 0
                                    • Surgikillundefined
                                      Surgikill @jens55
                                      last edited by

                                      @jens55 2020-03-29 11.31.37.jpg 2020-03-29 11.31.43.jpg 2020-03-29 11.31.47.jpg 2020-03-29 11.31.53.jpg

                                      You can see there is this weird flat area where it' not a smooth curve, kind of like the other holes.

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                                      • jens55undefined
                                        jens55
                                        last edited by

                                        Thanks for posting the pictures!
                                        This is certainly a puzzle. It seems pretty clear that either x or y is not stepping in those flat areas but what is the other stuff going on in these areas. It seems like a combination of issues.
                                        Did you post your config.g? I looked over the thread but couldn't find it ....

                                        Surgikillundefined 1 Reply Last reply Reply Quote 0
                                        • Surgikillundefined
                                          Surgikill @jens55
                                          last edited by

                                          @jens55 Here's the config.g

                                          config.txt

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                                          • mrehorstdmdundefined
                                            mrehorstdmd @Surgikill
                                            last edited by

                                            @Surgikill I have a 24 x 8 mm linear guide for the X axis, 608 bearings for pulleys with 8mm bolts as axles, and a direct drive extruder with a 36 mm motor- a bunch of pretty heavy stuff. The X axis weighs about 1.5 kg. I drive the mechanism with two little 64 oz-in NEMA-17 steppers and it can print with acceleration set to 10k and speed at 200 mm/sec.. Of course, I don't ever print at that speed/accel combo, but it demonstrates that you don't need a particularly light assembly to keep the speed up. Extrusion and the behavior of molten plastic will become the limiting factors before the mass of the assembly will if you're using "normal" size steppers to move the mechanism.

                                            If you were building a really big machine to make really big prints, speed might be more of an issue. On a small machine, printing relatively small objects, printing faster doesn't mean the print will finish sooner. Let's say you have a print running at 400 mm/sec with high acceleration so you can actually hit that speed. Even if you manage to get the extruder to work properly at that speed, each layer will finish so fast that you'll have to allow some time for the plastic to cool before depositing the next layer or the print quality will suffer. That means you have to print a sacrificial object, or multiple copies of the print, or just move the extruder away from the print and sit and wait for a while upon completion of each layer. Even at speeds like 80-100 mm/sec, you often have to use those techniques to slow things down a bit to maintain print quality. Print speed is overrated.

                                            Reliability is the thing to shoot for, so you don't have to babysit the printer or restart failed prints. Then you can start up prints when you go to bed at night and they're done when you wake up in the morning. It doesn't matter if they take 1 hour or 6.

                                            https://drmrehorst.blogspot.com/

                                            Surgikillundefined 1 Reply Last reply Reply Quote 0
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