SOLVED Calibrating E steps

Discussion in 'Calibration, Help, and Troubleshooting' started by Alex9779, Apr 18, 2016.

  1. R Design

    R Design Well-Known Member

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    40mm3 / s from the volcano (that could be 0.6mm layer height, 1.25mm extrusion width, 53mm/s print speed)

    For 1.75mm filament we have:

    pi * ( 1.75/2 )**2 = 2.4 mm3 / mm

    So an extrusion speed of :

    40 / 2.4 = 16.5mm / s

    I got to about 75% of that and it seemed crazy fast + my regular extruder was skipping with XT !

    However if you have the regular 30W heater I reckon you'll be worrying more about Thermal Runaway which is an issue with these higher nozzle temperatures.
     
    #61 R Design, Apr 19, 2016
    Last edited: Apr 19, 2016
  2. Miasmictruth

    Miasmictruth Well-Known Member

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    I thought I read somewhere that the volcano should be run at 30mm/s or maybe I am crazy..
     
  3. R Design

    R Design Well-Known Member

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    Watch out "40mm3 / s" is a volume, "40mm cubed per second".

    That's the best expression of the max capacity of a hotend and I guess it represents the max amount of energy it can put into plastic to melt it (there'll be a tonne of variables like the plastic in question, the nozzle temperature etc. but that is the figure I was given for a volcano; 15mm3/s for a regular v6).
     
  4. Miasmictruth

    Miasmictruth Well-Known Member

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    Ahh gottcha.
     
  5. Miasmictruth

    Miasmictruth Well-Known Member

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    On a side note you also have a much bigger opening and meltzone so even if the extruder is pushing and a high speed the resistance will be much much less, I guess you have to take into account your nozzel size if you want to ramp up the speed of the extrusion for the test.
     
  6. Miasmictruth

    Miasmictruth Well-Known Member

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    @Alex9779 based on the gcode you sent me I would say keep it under F150 that should roughly be 50mm/s print speed with those print settings it looks like.

    Assuming my calculations have any merit.
     
  7. PsyVision

    PsyVision Moderator
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    @Alex9779 I'll see if I can run some tests tonight.
     
  8. Alex9779

    Alex9779 Moderator
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    I think so but I am not able to explain it ;) but I try :p

    I think actually what @R Design calculated shows the direction. Extrusion is a matter of volume per second.
    And depending on nozzle size and your feeder this is what is limited.
    But on the printer we set the speed for the moves and that for all axes. The value we can set per axis is the length of the move.
    So we really set the time for the move of all axes to move a given length. The individual speed is then the individual length divided by that time.
    So if we have a printer move at 2700mm/min = 45mm/s like in my example we first have to calculate the time of the longest move.
    Taking this piece:
    Code:
    G1 X147.656 Y79.274 F6000
    G1 X148.147 Y78.783 E0.0346 F2700
    dX = 0.491mm, dY = 0.491mm, dE = 0.0346mm
    So the time we need for the longest move is 0.491mm / 45mm/s = 0.01091111111s.
    And then we can calculate the actual E speed 0.0346mm / 0.01091111111s = 3.171mm/s = 190.26mm/min
    So at 45mm/s print speed, the layer height of I think I sliced this at 2.5mm and a nozzle of 0.4mm the extruder runs at 190mm/min at max... That is for infill. Outer perimeters are set to 60% I think so perimeters are at 115mm/min and when I take this for the calibration then I get nearly the values I wanna have constantly...

    Now it is all clear to me!!! Yeah!!! I got it!!!

    Hope you can follow? :)

    EDIT: took me an hour to write that post :D really!!!
     
    #68 Alex9779, Apr 19, 2016
    Last edited: Apr 19, 2016
  9. R Design

    R Design Well-Known Member

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    On reflection, there are perhaps two different areas where extrusion speed is important:

    1) during a printing movement: when melting plastic and laying it down;

    2) during retraction;

    In case (1) the limiting factor is how much plastic the hotend can melt, and that's related to (at least) the heat capacity of the plastic, the volume of the plastic passing through, the conductivity of the plastic, the design of the hotend and the power of it's heater. I've heard for the Volcano it's 40-45mm3/sec max.

    For 1.75mm diameter filament, this translates into a max filament speed through the extruder of about 16.5mm/s.


    In case 2, retraction, the maximum desirable speed is related to something else. I've heard people speak about "breaking the meltzone" meaning, I think, tugging so hard & fast that you break the continuous lump of molten plastic in the extruder and so are effectively drawing a vacuum and not retracting any more.

    That limit is going to be a feature of the plastic and of the hotend and the temperature. At this stage I know little about retraction but I have the impression the desirable number will be higher than the aforementioned maximum during extrusion.

    (Aside, given my regular extruder was slipping on XT at around 30mm3/2 extrusion volume rate, now I realise it must have been failing at the retraction speeds that were default in S3d. Hmmmm.... Could be a reason for the Titan? Or maybe I could tighten the idler?)
     
    #69 R Design, Apr 19, 2016
    Last edited: Apr 19, 2016
  10. Alex9779

    Alex9779 Moderator
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    So true...

    The important point I worked out is that the speed is for all axes in a move. That is the main point! And that the longest moves of an axis dictates how fast the other axes can move because at the end of that move all involved axes have to be at their target position.

    If you retract or in the calibration situation you move only E, so the speed directly set the speed the filament is extruded...
     
  11. PsyVision

    PsyVision Moderator
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    So, simplistically after all of this, everything is ok? What steps/mm are you using? :p
     
  12. Alex9779

    Alex9779 Moderator
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    LOL yes, everything is fine. My print last night, I told already, I printed with 10% less E steps which were actually 420 was pretty close to what I found is the optimum, 417.5. Which is ironically the value @Greg Holloway has set as stock value in his version of the Hybrid firmware...

    But dealing with it gave me a lot of insight into how movement and speed and stuff works...
     
  13. Miasmictruth

    Miasmictruth Well-Known Member

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    This thread reminds me of the XY motion thread we had going last week or so lol
     
  14. mike01hu

    mike01hu Well-Known Member

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    @Alex9779 , just a thought, is the motor missing/adding steps due to a faulty current setting?

    Forget this, I found all the rest of the thread, Doh! o_O
     
    #74 mike01hu, Apr 20, 2016
    Last edited: Apr 20, 2016
  15. Alex9779

    Alex9779 Moderator
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    The issue is solved... It is just that I used the extrusion script but the speed was too high, I was pushing the extruder to its limit at least for XT. So I wasn't getting reliable results.
     
  16. mike01hu

    mike01hu Well-Known Member

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    . . . but a fascinating thread leading to a greater insight on extrusion parameters. Worthy of a sticky!
     
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  17. Alex9779

    Alex9779 Moderator
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    Yeah I really pleased when I figured that out... I never thought about the connection between speed of the head an speed of the extrusion and all that stuff but now it is very clear to me...
     
  18. Kick2box

    Kick2box Well-Known Member

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    ...and nothing comparable to British humour!
     
  19. mike01hu

    mike01hu Well-Known Member

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    Sorry:rolleyes:
     
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  20. Alex9779

    Alex9779 Moderator
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