In most prints, you will have two or
more solid layers on the top and bottom
with your infill sandwiched between
them. Figure 18 shows the progression
of the print as the printing takes place.
The Slicer software will have a field for
defining the number of top solid layers
and bottom solid layers. A solid 40 mm
x 5 mm cylinder is shown in Figure 19.
Both the top and bottom solid layer
counts have been set to zero. The
perimeters have been set to one. These
settings are typical for printing thin bracelets, tank treads,
or even calibration objects.
A skirt is a perimeter that surrounds the main object. It
is used to give the extruder a chance to get its flow
regulated before starting the actual object. The slicer
software will allow you to set the number of loops
(perimeters) and the distance from the main object.
When a skirt is set to a distance of 0 mm away from
the printed object, it is often called a brim (Figure 21). A
brim is used to help the main object stick to the bed, and
help with curling of the edges. Typically, a brim is only one
layer thick to ensure it is easy to remove from the main
object. While both Slic3r and Creator let you print skirts,
Slic3r lets you print separate skirts and brims. You also have
the option to set the height of the skirt. A high skirt can
shield the main object from drafts while printing. The Afinia
software does not support skirts in any form. It does have a
sequence at the start of the print that cleans the nozzle.
A raft is used to help with bed adhesion and warping.
In addition, they are often used to compensate for a build
platform that is not perfectly flat or slightly out of level. The
problem with creating rafts is that the raft may be difficult
to remove from the bottom of the print.
The Slic3r software gives you little control over the size
of the raft; this can result in a raft that is impossible to
remove from the main object. Creator gives you the most
control over the raft. The raft shown in Figure 22 was
printed with Creator. The Afinia software only gives you the
option of raft or no raft. To date, the best performing rafts
I have printed have come from the Afinia.
While the current batch of filament-based 3D printers
are remarkable in their ability to create accurate prints, they
can't defy the laws of physics. Take the object in Figure 23;
this object has overhangs that you cannot extrude without
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