Filament size not consistent.



  • I'm trying to tune my max extruder rate on my new Hermera. It will start to extrude with a width of 0.4 mm but the it will grow to 0.75 mm
    I started with G1 E50 F120 and in steps went up to G1 E50 F460. here are some photos.!
    IMG_20200219_215514.jpg IMG_20200219_215542.jpg IMG_20200219_215612.jpg IMG_20200219_215635.jpg IMG_20200219_215825.jpg

    The first two are at the lower speeds while in the third and fourth, which are at G1 E50 F420 the is a loop which is always consistent and when it does the loop there is a clicking noise.
    Not wondering if this is the Hermera or something strange in my setup.
    Thanks for the help.



  • When you are tuning for maximum extrusion rate, you are not concerned with the filament diameter as it exits the nozzle. There are a number of reasons why it comes out thicker (it doesn't actually come out thicker but mis-forms because it is in thin air).
    All you need to be concerned about is the clicking which is what you want to avoid.
    Maximum extrusion rate is just a tad below where you get the clicking.

    Having said that, F420 seems very slow. What material and what nozzle temperature are you using ?

    Edit: Never mind the comment about slow, did the calculations and it seems about right (if my calculation is correct)



  • Thanks Jen55! I'm doing the tests at 220°. I would have thought the Hermera would go a bit faster. My problem is in the benchy test that in the bow there is some sagging (droops) as you can see in the photo.
    IMG_20200219_231829.jpg ! IMG_20200219_231813.jpg .
    Agree its not the best color. 🙂

    Fan is on during the test print of the benchy.



  • An average hot end can melt about 8-9 cubic mm per second, a Volcano hot end about twice that.
    Volume is filament radius squared * pi * extrusion speed or (1.75/2)**2 * 3.14 * 420mm/60sec which is roughly 2.4 square mm * 420/60 or roughly 16.8 cubic mm per second. That means that either I screwed up on my calculation or you are running a Volcano (or similar) hot end.



  • That sagging could be caused by too hot an extrusion temperature or not enough cooling with the fan. Try at 205 for extrusion temperature.


  • Moderator



  • thanks Phaedrux yes I did see it but had tried a different test for max extuder speed. Just finished do that test and I was too high so now its almost right. Will try some new test to see what happens.

    Jen55 I think your math is good but for sure 420 is too fast seeing the Hermera has a hotend like the Titan Aero only it is more direct.


  • Moderator

    @Synapsis said in Filament size not consistent.:

    seeing the Hermera has a hotend like the Titan Aero only it is more direct

    It doesn't matter how hard you push it, you're still up against the melt rate.


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