Living in the edge ...



  • Hi,

    I would like to know what are the limits of the printer, mainly in two aspects:

    • The minimum layer height that I can print (according to what I read, it depends a lot on the material)
      and
    • The maximum speed that I can print.

    How can I find out?
    How do I transform the extrusion speed into printing speed? Through the DWC, I can manually extrude at a certain speed, and increase that speed, until I notice that I lose steps ... but once I know that speed, for example 20 mm / s, how I transform that extrusion speed into printing speed?

    Thank you



  • Minimum layer heights:

    • The Duet will attempt to give you the layer height as found in the print files from your slicer. If you set your slicer to do 0.05mm layer heights, it will get to as close as it can to that.
    • I have read that going below 0.08mm on PLA can cause issues or print more difficult, but have not tried it.
    • Nozzle diameters are also important when trying to print low layer heights. Typically a nozzle can do 1/4 to 3/4 of the nozzle diameter as layer height (allows enough squeeze to lay it down), which means if you want to attempt going below 0.1mm layer heights, you need a 0.2mm nozzle.
    • Hardware may also be a limiting factor. Microsteps are not always very accurate and the actual layer height might be a rounded value close to what you set, but not exactly what you wanted (difference should be quite small, but at low layer heights, it can be enough to affect the print).

    Maximum speeds:
    This is very much printer dependent, but usually the limiting factors:

    • Quality of the final print. The faster you print, the lower the quality will be. Artifacts like ringing are more pronounced at higher speeds.
    • Printer's melting chamber in the nozzle. Each extruder have a limit for how fast new filament can be molten. Depending on the molten chamber size, this limit can temporarily be exceeded without issue. When it is exceeded for too long, you get underextrusion (typically this happens on large areas where the printer achieves maximum speed for a long time before slowing down). As an example a Chinese MK10 extruder can melt 4.8mm^3 of filament per second. At 0.2mm layer height and a standard 0.4mm nozzle, this gives us a maximum sustained speed of 60mm/s as a theoretical maximum. Doing lower layer heights, can give you faster sustained speeds.
    • Printer head: Direct Drive extruders are typically quite heavy. Bowden extruders are typically light. With a light head, you can easier get to a greater maximum speed since it takes less power to accelerate and deceleration can happen slightly later.
    • Printer construction. If you want the head to move at massive speeds, the printer needs to handle the forces applied to it - requiring a very ridged structure.

    Now, as you mentioned, DWC have the option to increase both Extrusion Speed (this is how much filament is pushed into the extruder) and Printing Speed (how much X Y and Z as well as E is increased). It should be noted that Printing Speed also adjust the rate of Extrusion to match the speed of movement for the lines being printed. By increasing the Printing Speed, DWC can show you what speeds are achieved and you can enter it into your slicer - newly sliced files will then use the new speeds (they either take a value in mm/s or mm/min - simply multiply or divide by 60 to change between the 2).

    Using extruders like the MoarStruder or E3D Volcano (which features massive molten chambers), one can achieve quite fast printing speeds at large layer heights.



  • @jacotheron thanks, great explanation



  • @jacotheron

    After re reading your post.... i have no clear how I transform the extrusion speed into printing speed. Some tips?

    Edit.... some interesting information....

    3D Print speed calculator



  • @peirof said in Living in the edge ...:

    3D Print speed calculator

    It would help to know what your melt rate is in cubic mm. Then you can use an excel sheet to solve for speed.

    0_1539326203908_b668e44c-38cb-4a23-8e95-d8fe4c4dd9a6-image.png

    I don't know what hotend you are using, but the E3D V6 can do about 13-15mm^3/s. I think that's probably a safe place to start testing. While printing solid infill you should be able to tell if it's printing well or not. Increasing the temp to the max rated for the material you have loaded can help sustain the high speeds.

    Slic3r even has a volumetric speed limit so you could set the speed to 0 for automatic, and then it will try and print as fast as your volumetric rate will allow.



  • No worries. What I meant above is that the latest DWC indicates travel/printing speeds achieved (both the requested and what it reached). If yours have it, you can simply check in your slicer to see what speed unit it uses, and then update it to the new value (which may have to be multiplied by 60 to get a mm/min value, if your slicer uses mm/min).

    Alternatively you can calculate it as <currentspeed>*<printspeed-adjustment>/100 = <new-print-speed>
    <currentspeed> - what you have now, for example 60mm/s
    <printspeed-adjustment> - the percentage at which you got good and reliable extrusion, for example 125%
    100 - we divide by 100 here to rather get 1.25 for the adjustment
    <new-print-speed> - your result, for example we get 75mm/s, using the above example values



  • @peirof I run the risk of seeming to be spamming these forums but this is relevant to this thread and might be of interest to you https://somei3deas.wordpress.com/2018/10/14/real-3d-printing-at-high-speeds-and-even-higher-melt-rates-with-a-large-nozzle/ and the video that goes with it here https://www.youtube.com/watch?v=rUV5IZxfAxU



  • @deckingman

    Thanks for links.... Very interesting info.


 

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