Reported settings for M200 don't match those set?

DocTrucker

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:

M200
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?

Thanks.

tomasf

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]
(or
[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.

dc42

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.

DocTrucker

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.

Thanks.

dc42

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.