3D Systems Cube User Manual page 8

Reduce Voids in Printing
To reduce voids in your prints, empty all debris from the purge bins. In addition,
verify that no print material has collected around the jet wipers.
Glue
Using Cube Glue is always recommended for printing, especially for areas of the
print pad where INF prints. Ensure that glue is applied to the print pad in an area
that is larger than the base of your part.
PURGING PLA AND INF