Hemera direct drive untidy prints...

Discussion in 'HotEnds & Extruders' started by joss002, Feb 20, 2020.

  1. joss002

    joss002 Member

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    Ive had the Hemera on my Tevo Flash with 2100 drivers for 3 months and struggling to get decent quality prints.
    VREF set to 1.19 and I also set it back to 1 but there was no difference so set it back to 1.19
    Esteps set and it extrudes 100mm spot on.
    Ive tried coasting, combing on and off, outer walls before inner walls on and off, infill before walls on and off, different temp and fan settings for a few brands of PLA, and retraction settings from 0 to 2mm and at various speeds.
    Candy floss stringing is an issue, but the outer wall is very untidy. Fitted the E3D V6 to the Tevo Flash last year, set the esteps and it printed great no stringing or print quality issues at all but for the life of me I cant get the Hemera close to how the standard or the E3d V6 Flash was.
    In the photos the item on the left is combing all and on the right combing is off with retraction at .75mm and 35mm/s, print speed is 40mm/s and travel speed 90mm/s
    The Benchy is my first print with TPU, Ninjaflex 85A and that's come out nice for a first try with TPU.. IMG_E6498.JPG IMG_E6497.JPG IMG_6500.JPG
     
  2. joss002

    joss002 Member

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    One thing ive noticed when its retracting is the lever moves towards the front, like it you were releasing pressure to remove the filament, its only a small amount but noticeable. Is that normal??
     
  3. johny

    johny Member

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    Can you confirm that your printer and slicer are configured correctly? I know this is difficult, but have you updated the firmware according to the guide and run PID tuning? Also, have you set things like the nozzle/line width and flow rate correctly? What slicer are you using? It may help if you can share more details about the values/settings you are using.

    Retraction, tension and temperature would be the things I'd try to rule out first:
    • Retraction: The Hemera seems to require very little retraction (typically I use between 0 - 0.5mm), but you can also try lowering the retraction speed.
    • Tension: I do not tend to find the tensioner moves whilst retracting. For TPU I've found I get the best results with little to no tension. For PLA, PETG, etc. I tend to need a little tension (but not a lot). I suggest starting low and increasing it gradually.
    • Temperature: Compared to another printer/extruder I own, the Hemera seems to require a little more heat (around 10 - 20C more), but I am using a Nozzle X which can require up to 10C more. Stringing can indicate that your temperature is a little high, but a little bit of stringing can be normal with some filaments. Does the temperature stay constant whilst printing (e.g. +/- 1-2C)?
     
    #3 johny, Mar 6, 2020
    Last edited: Mar 6, 2020
  4. joss002

    joss002 Member

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    The nozzle is the .4mm that came with the Hemera and usually .2mm layer height and 40mm/s print speed and 90mm/s travel.
    Slicer is Cura 4.5.0

    I had already had a newish E3D heater and thermistor that I fitted to the V6 set up, that I carried on using, that was set up with Arduino.

    PID tuned with Pronterface and through the interface on the printer.

    Nozzle/line width and flow rate are as they are in Cura .4mm and 100%, as for correctly!! I dont know lol, as there no mention of recommended setting and the standard Tevo Flash as well as with the E3D V6 hotend worked great with those settings. And with the Esteps set it extrudes 100mm when asked to extrude 100mm.

    Retraction of .1mm gets rid of the stringing "branches" but candyfloss/cobweb stringing can be really bad on some prints, which again on the standard Flash and E3D V6 was never a problem

    When I first fitted the Hemera the tension was set pretty loose as there was no mention of how tight to set it but for a while now it is set with the white block flush with the body of the lever as recommended in the assembly guide and ironically my first print with TPU turned out pretty good set with the high tension !!

    Temp is pretty much solid with only +/- 1'c fluctuation for a second after long travel or extrusion. And Ive worked through the temp ranges for a few different types of PLA

    Ive been 3D printing for 14 months so Im not an expert by a long shot lol but surely it shouldn't be this tricky to get a nice print when basically all you've done is remove the bowden tube !!
     
  5. johny

    johny Member

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    Sorry ‘correct’ was a bad choice of word. Lol. I meant are they set as you expect as it can be easy to forget you’ve changed something when troubleshooting. Cura will indicate the settings you’ve changed.

    I am using 0.4mm and 100% too. The main difference between the config for my bowden printer and the one with the Hemera is the amount of retraction. The remaining settings are largely the same and I’ve not had to change settings for anything like combing.

    I don’t think it’s a print speed issue. 40mm/s is quite slow for PLA and the Hemera should easily handle faster speeds.

    The tensioner on mine set lower than yours. I’m not sure it’s a tension issue, but it’s curious that the tensioner moves as you describe. My printer is quiet and when the tensioner is set incorrectly I can usually hear faint clicking/grinding noises. It may be easy to miss this on noisier printers.

    My instinct is that it might be a temperature issue. I’ve seen similar defects when the temperature is set too high. I would experiment with temperatures (and cooling). I would probably start with printing a temperature tower, but I would also independently verify the temperature of the hot end (e.g. with an infrared thermometer).

    Another thing to consider is whether it could be something mechanical. For example, check the tension of the belts/pulleys on your printer, check for vibration issues and any loose bolts/screws? I don’t think that’ll be it, but there is no harm in checking these things from time to time, especially after installing new mods.

    If the temperature and mechanics check out, focus on Cura settings that relate to the extruder. Don’t be afraid to adjust things like the flow rate and line width slightly in either direction to see what effect it has. However, I recommend only adjust one thing at a time so that it’s easy to measure the effect.

    Good luck!
     
  6. joss002

    joss002 Member

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    I gave it a service when I fitted the Hemera and fitted some new wheels on the x carriage and everything was running smoothly and tight.
    Now 1 thing I just thought about is the 1st layer goes down great but after a while I need to adjust the z height in the baby steps by a couple of clicks as it looks like the nozzle it dragging a bit, I put it down to things expanding with the heat but could be worth trying the flow rate.
    I'll keep messing with it anyway lol

    Thanks for the help.
     
  7. johny

    johny Member

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    Enabling Z-hop may help prevent dragging, but I agree that it’s worth trying to identify the underlying cause.
     

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