Slic3r
Figure 2.65: Bridging lament shape.
If you reduce the material ow you’ll get smaller circles to some extent,
until the plastic viscosity decides it’s time to break your bridge because of
too much tension. If, on the contrary, you extrude too much material, the
shape of the extruded lament won’t change (still equal to nozzle diameter)
but you’ll get a loose bridge.
Let’s start from a denition:
Extrusion Width is the thickness of a single lament extruded either in
free air or above a surface. It’s not the distance of two adjacent
paths since some overlap will be generally applied in order to get
better bonding.
Bridges: the easy case
As said above, there’s only one correct ow rate for bridging: the one that
doesn’t make your bridge sag or break. Extrusions are round and their
diameter is equal to the nozzle diameter. Parallel paths will be positioned
so that they are tangent, thus the spacing between one path and its neighbor
is equal to nozzle diameter as well. (In case of bridges, we want no overlap
because it has proven to drag the existing paths.)
The required material volume for a path of unitary length is calculated
accordingly to the cylindric shape, thus with a circular cross-sectional area:
E = (nozzle_diameter/2)\textasciicircum{2} * Pi
Extruding on top of a surface
In this case the problem is: what shape will our extrusion get? We know
it will get squashed horizontally, but will it have a rectangular or oval
shape? What’s the maximum extrusion width we can get with a given
nozzle diameter before plastic starts curling at the sides?
Slic3r assumes that the cross-sectional shape of an extrusion is a
rectangle with semicircular ends. So the relationship between desired
extrusion width and volume to extrude is the following:
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