Sometimes during a print an object will come loose from the build plate, usually resulting in the print being ruined.
The first layer of the print needs to stick to the build plate. Preparing the build plate properly, to be sticky so that that first layer adheres, can aid in avoiding this occurrence.
It is also important that the initial layer print at the correct height above the build plate: just a little “squished” so that it adheres, not too high so that it doesn’t adhere, nor too low so that it is overly “squished” or dragged by the print nozzle.
If the printer has just been turned on and heated up, it is also important that the extruder is consistently emitted melted plastic during the entire first layer, rather than “burping” and failing to emit melted filament at spots in the first layer. This does not tend to be a problem with the Polar3D printer – but if you do encounter a problem consistently extruding melted filament when the printer first begins extruding, consider printing a few skirt loops to establish a smooth flow of filament, before printing the actual object. (The Polar Cloud’s predefined slicing profiles typically in fact generate a bit of a skirt by default, see Figure 15.19; such a skirt may be useful for the first print with a new roll of filament, but is less likely to be necessary for subsequent prints.)
And printing at the proper temperature for your filament is important for adhesion.
Some objects, however, will need extra assistance for adhesion. In those cases, printing a brim or raft may aid in keeping the object in place.
For many objects, printing involves non-extrusion moves of the print head, as well as extrusion moves. When the extruder nozzle resumes extruding filament after a gap, if the previously printed material had, perhaps, a messy, “curled up” edge, the extruder may bump the edge of that previously printed material; in the worst case, this may even knock the object loose of the build plate. Good, firm adhesion to the build plate, as already discussed, will help avoid this becoming a problem; but see also the discussion of configuring filament retraction and print head Z hop in Section 16.1, to reduce the potential for the extruder to encounter smeared or curled up edges of previously extruded material.