Slic3r
Ideally, we would want to ll all of that yellow area by placing the
extrusions closed to each other. However, it’s very unlikely that the second
extrusion will ll the space below the previous one, so there would still be
a little void. The ideal overlap would be something like:
0 < overlap factor * void area < void area with overlap
factor ranging from 0 to 1. Overlap factor represents how much void
remains between the extrusions. It’s dicult to estimate this amount,
since it probably depends also on viscosity of plastic, extrusion speed and
temperature. In the past, several values were tried for overlap factor, but
some users were still reporting too sparse paths. A value of 1 is currently
being used to guarantee that the error (which is always present) is fully on
the side of abundant extrusion rather than lacking material.
Path spacing is thus:
spacing = extrusion width - layer height * (1 - PI/4)
Sane defaults
Slic3r allows users to dene extrusion width manually for each kind of
extrusion (perimeters, inll, support material etc.) but will calculate
sane defaults if no custom values are entered. For the outermost loop of
perimeters (aka external perimeters) Slic3r will default to a thin extrusion
width, equal to
nozzle diameter * 1.05.
This is considered the thinnest safe extrusion width. A thin extrusion
width provides better accuracy to the object shape and minimizes the ow
errors caused by irregular lament.
Extrusion width for other things is calculated by getting the cross-
sectional area of the congured nozzle diameter and then calculating the
extrusion width produced by extruding that amount of material. In
other words, by matching ow speed and head speed. The purpose of
this logic is to nd the “native” ow that minimizes side forces during
extrusion. Such calculated extrusion with is capped to max value equal to:
nozzle diameter * 1.7, except for internal sparse inll where the full
native ow is used.
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