If the problem is with infill in walls, if the wall is thinner than ((2*number of perimeters)+1)*extrusion thickness, then it must be an exact multiple of the extrusion thickness otherwise it cannot be filled and will end up as a hollow wall. You can also end up with hollows if the size of the area to be filled is less than the distance between the infill lines (usually (100/infill percentage)*extrusion width). The extrusion thickness is usually automatically set by the slicing application, but most slicers allow a manual over-ride. The automatic setting will usually be the same or slightly thicker than the nozzle diameter that has been set.
Otherwise the problem will be in either the STL or the slicing application. If the same STL fills OK with a higher infill percentage and it does not have either of the issues detailed above, then it is probably a bug in the slicing application. You could try changing the infill pattern if the slicer has such a feature, or try a different version of the slicer, or use a different slicing application. Slic3r and Cura are both free applications. If you are using Slic3r, try a different version (even if older than the version you are using), because Slic3r seems to have various different bugs in each version.
One other thing to try is to rotate the part in the slicing application by 30, 45 or 90 degrees so it is made in a different orientation on the build plate.
Dave
Edited 1 time(s). Last edit at 11/17/2014 07:14AM by dmould.
