ahmetcemturan/SFACT — Issue #22: "lash" plugin only works correctly for rectangular geometries
Author: sanktnelson
Created: 2012-02-27 13:32:11+00:00
State: open

After a bit of tinkering with my new felixprinter I finally figured out that the lash plugin contains a "thinko". The way it compensates for backlash is strictly speaking only correct for rectangular pieces, i.e. with all perimeters aligned to the X and Y axis.
Way to reproduce: make a rectangular piece and rotate it slightly, i.e. alpha=5 or 10 degrees. printing this with backlash in the axis will leave pieces of wall after the corners that are parallel to the axis for a length of backlash/sin(alpha). This could be removed by reversing the extruder movement along the relevant axis for the backlash distance _at the corner_.

What the lash plugin does instead is trying to compensate for the backlash _during the path to the corner_, which results in the corner points being in the right place, but the line in between is only correct if it is parallel to one of the axis. On most prints and printers with edges mostly parallel to the axis and backlash 0.1mm or less this is barely noticeable, I only noticed because I have a bit of a vibration issue in my x-axis and can only use it somewhat loosened until that is fixed. Nevertheless, fixing the plugin to do the right thing in every case would improve the quality on any printer that uses this plugin.

I'll gladly provide test pieces or test updated code, but I haven't understood the plugin code yet.