Slic3r
Backlash
Backlash is a mechanical defect of one or more axes that basically reduces
the amount of actual motion whenever a motor inverts its spinning direction.
It’s generally caused by loose belts. On printers with a moving bed, its axis
(usually Y) is more subject to backlash because of inertia. So, if you get
dierent dimension errors in X and Y, that’s caused by backlash. You’ll
need to tighten your belts.
Flow Math
The above causes do not depend on Slic3r and, when possible, they need
to be xed before attempting any software solution.
That said, the ow math used in Slic3r plays a good role in making
correct dimensions, since it tries to guess what the shape of the extruded
material will be and how thick the extrusion will result on the horizontal
plane given an amount of material. Being an approximation, it carries an
error. The usual way to deal with these issues involves tuning the Extrusion
Multiplier setting in order to increase/reduce the amount of plastic, thus
making extrusions more or less thick. But this will also aect solid surfaces,
so it’s not the ideal solution.
For more exact dimensions you need to check the External Perimeters
First option. Printing external perimeters rst will prevent the shift caused
by extrudate overlap. On the other hand, printing internal perimeters rst
hides seams better, so it’s your take.
A new XY Size Compensation option was also introduced that allows to
grow/shrink object shapes in order to compensate for the measured error.
Supposing your holes are smaller by 0.1mm, you can just enter -0.05 in
this option to get them compensated (negative sign means shrink inwards).
This is not recommended.
Z Wobble
Undulations in the walls of a print may be due to wobble in the Z axis.
A thorough analysis of the potential causes is given by whosawhatsis
22
in
his article “Taxonomy of Z axis artifacts in extrusion-based 3d printing”
23
,
22
http://goo.gl/iOYoK
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http://goo.gl/ci9Gz
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