User's Manual Part 2

Glossary 275
ence Teachers Association, the American Association for
the Advan cem ent of Science, the National Research Coun-
cil, and the nonpr ofi t or ga n i zat i on Achieve. For details, see
http://www.nextgenscience.org.
over-extrusion
When the extr u d er outputs a surplus of plastic, over-ex-
trusion results. Over and under-extrusion are caused by a
mismatch between the slicer’s expectations and reality: the
slicer expects that when a millimeter of raw filament i s fed
into the extruder, a specific volume V
e
of plastic will then
be extrud e d — output by the extruder. When the actual
volume of plastic output, V
a
,exceedsV
e
,over-extrusionre-
sults; when V
a
is less than V
e
,under-extrusionresults.
There are a number of causes of such a mismatch of plastic
extruded, but it generally is the result of the input fila-
ment diameter not matching what the slicer expected, or
the steps per mm for the extruder being incorrect. By care-
fully measuring your filament diameter, and then checking
that that value is properly entered in the slicer – for a
Polar3D printer, this means properly entered under the ob-
ject’s “PRINT SETTINGS”,“ADVANCED”, “Filament”, “Diameter”
–youcangenerallypreventover-andunder-extrusionfrom
occurring. (But note that poor quality filament whose di-
ameter varies can cause intermittent over-extrusion and
under-extrusion.) 241, See also filament, sli cer & under-
extrusion