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  • Strings and more Strings

    new to the forum but have been addicted to the videos since my wife got me an Ender 5 last Christmas. I have an odd stringing problem. Using temp tower and retraction tower from Cura and the post processing scripts. Using PLA. The retraction tower at 200C showed 5mm to be good. But the temp tower at 5mm retraction shows more strings at lower temps. This is puzzling. The cali-cat is 20.1mm, so i may be over extruding but by about 0.5%. The cat was printed at 200C and 5mm, which should be good, but shows heavy stringing. Printing hotter to avoid strings is counter-intuitive.
    Any hints?

  • #2
    It's about finding the right balance. If, for example, 5mm retraction @ 210C nozzle temp works well, then use it. I would call the stringing on the CaliCat moderate.

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    • #3
      To explain all possible variations of temperature, extrusion rates, and retraction rate, you probably need to Ph.D. in fluid dynamics. I would not worry about why; just find a combination that works for you. P.S. The combination that works with one brand and one color of the filament may not be optimal with another.

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      • #4
        I agree with Irv Shapiro. What I try to do is come up with a profile for each filament that works with my printer, knowing that the profile likely would not work for anyone else. It might be a starting point, but would most likely need tuning.

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        • #5
          To reinforce the point made earlier. I generally find that importing someone else's profile is a sub-optimal solution. Sometimes they work, and sometimes they do not. Using a 3d Printer is both a science and an art. Much like woodworking. You need to begin by learning basic techniques. Then apply what you learn to your current problem. In 3d printing, key techniques include:

          - Bed Leveling
          - Setting Appropriate Extruder Temperatures
          - Setting Appropriate Bed Temperatures
          - Stepper Motor Calibration
          - Slicer Concepts
          - Advance Slicer Techniques
          - What is an Overhang?
          - What is a Bridge?
          - Using Supports
          - Bed Adhesion Techniques

          This is just the beginning of the list. When I started using a wood lathe, I needed to learn an equally difficult set of skills with the added dimensions of complex hand/eye coordination. Hitting a golf ball takes a lot of practice. Few things that are worth during are easy.

          Stick with it. Once your master 3d printing concepts, you will be able to move from one slicer to another, one 3d printer to another easily, and produce wonderful projects.

          Then, when you think you have learned it all, you can learn to model your own solutions in a CAD program, add electronics with programs, and more.

          Welcome to the world of makers.

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          • #6
            As a research engineer, I should be able to experiment my way through this. I printed a heard of CaliCats at different temps. At 240 the tail strings went away but issues with the ears started. Somewhere between 220 and 240 might be optimum for this spool of PLA. At 270 (max temp for my stock Ender 5) things got really bad.

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            • #7
              Oh yeah, I would never print PLA at 270C. Not sure what happens to the plastic @ that temp, but I don't imagine it's anything too good. To be honest, anything over 210C seems high for PLA. I'm thinking you might have retraction &, perhaps, flow rate issues.

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              • #8
                I had same issues found a video on you tube (I honestly forget who) he goes over step by step calibrations. This helped me but basically he started with a stepper motor calibration, then bed level, then temp tower followed by retraction tower. By doing this I was able to eliminate most of my stringing accept on the smallest of parts.

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                • #9
                  I ran the temp test to the full flight envelope of the Ender 5 to be complete. That stringing minimizes at 240c for PLA seems odd to me but that is the data. It defies the theory I know. Almost out of that spool. Perhaps another type? Is there a quantitative way to evaluate a print quality? Without this its just guessing.

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                  • #10
                    As I mentioned before, run tests on retraction. It could well be that filament is oozing &, when the nozzle moves to another point to start printing again, the oozed filament strings out. Correct retraction will help reduce it.

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                    • #11
                      Is there a coupling between head temperature and extruder speed to account for the lower viscosity of the hotter filament ?

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                      • #12
                        Yup, there is a relationship. I'm sure it will come as no surprise to you that higher hotend temps permite faster print speeds. However, it's not without complications. The counter to that relationship is the fact that many printing issues can be resolved by slowing down the print speed. I find this is particularly true for the initial layer.

                        Oh, & I wouldn't go looking for a mathematical formula. I think there are just too many variables for that. It's about experimentation & coming up with the correct balance. I've read & seen video of people saying they zero in on 1 particular brand of filament to reduce some of the variables.
                        Last edited by Ender5r; 05-31-2021, 09:19 PM.

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