Reported settings for M200 don't match those set?

  • Hi

    Using web control I set the filament diameter as follows:

    M200 D1.744

    and when I enter M200 for conformation the returned value is:

    Filament diameters for volumetric extrusion: 0.730 0.730 0.730 0.730 0.730 0.730

    What am I doing wrong? Do people commonly use volumetric extrusion?


  • I don't think you're doing anything wrong. Looking at the source code, it looks like this is a bug. I could be misunderstanding something about the code, but my limited math skills tells me line 1599 of [c]GCodes2.cpp[/c]:

    [c]reply.catf(" %.03f", (double)(2.0 * sqrtf(vef/PI)));[/c]

    …should be:

    [c]reply.catf(" %.03f", (double)sqrtf(4.0 / (vef * PI)));[/c]
    [c]reply.catf(" %.03f", (double)(2.0 * sqrtf(1.0 / (vef * PI))));[/c])

    to be the reverse of the line that calculates extrusion factor a few lines above it. This should mean volumetric extrusion works properly and that it's just formatting it in the wrong way when you do a M200.

  • administrators

    I confirm this is a bug, which affects the value reported by M200 but does not otherwise affect volumetric extrusion. It will be fixed in the 1.20 firmware release.

  • Great, glad it's just the response that's off.

    Is the volumetric extrusion and firmware retraction rarely used? I am trying to slowly progress towards a as well a calibrated machine as reasonably practical and as filament diameter checks are advised before prints (or at least on spool change) it seems a practical way of being able to prepare in advance.

    Is there a feature request already in the pipeline to ensure that when pressure advance and firmware retraction are used together the retraction doesn't exceed a specific value? Appears the E3D heads are sensitive to this and I am clutching at any available avenue to reduce stringing on a long bowden system!

    Any idea when the next bug fix release for the v0.6 compatible firmware is available? I do like the generation 2 systems but need to prove this system first before I can get the go ahead to take it out of action for the upgrade.


  • administrators

    I don't think many people use volumetric extrusion.

    I don't think it would be a good idea to limit total retraction, because it is unnecessary unless the extruder is skipping steps during extruding moves and it would cause over-extrusion. However, if you use large amounts of pressure advance, you should reduce retraction distance.

    Stringing is normally controlled by reducing printing temperature and/or by adjusting retraction speed and (if applicable) Z hop.

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