15.1.1 Printer not extruding at start of print

1.

When the extrusion is initially missing or skimpy/sketchy/patchy, but later settles into good extrusion, it may be that there wasn’t enough melted plastic initially in the extruder (particularly likely if you are resuming printing after a pause where melted plastic oozed out of the extruder). Try starting your print with a skirt (which is the default for Polar Cloud supplied slicing profiles). (Or, on a Polar3D printer, you could use the local web interface’s “Manual Printer Controls” screen’s “Extrude 1mm” button a few times shortly before beginning your print, to check on and ensure a good flow of melted plastic once the actual print is started.) If you must pause the printer during the print of an object, consider how long a time you’ll have the printer paused (and the viscosity/drippiness of the filament you’re using), and then use “PAUSE” vs. “COLD PAUSE”, as appropriate; see Section 10.4.2.

Another issue that can cause patchy or erratic extrusion of the first layer is a build plate print bed that is not level. As discussed in item 2, having the extruder nozzle “too close” to the build plate print bed can prevent proper extrusion. But if the print bed is not properly leveled, then the extruder may be too close to the build plate to extrude during only some portions of the first layer, resulting in a patchy first layer with portions missing. Note that such a patchy first layer will tend to have a number of bad consequences later in the print, such as the object warping, or coming loose of the build plate. So check your printer’s calibration to ensure that the print bed is quite well leveled.

2.

When the first layer or two does not print, but then extrusion begins successfully once the print head is higher above the print bed, then you may need to adjust your printer’s z height calibration: the extruder may be starting too close to the print bed (so that for the first layer or two there is not enough room for the plastic to extrude).

3.

If no (or almost no) extrusion occurs, especially if you earlier noticed flakes of filament on the print bed, or can tell that the filament is loose (not gripped) in the extruder, or even see a stripped section on your filament, it may be that the drive gear in the print head has stripped the filament so that the drive gear is no longer biting into the filament to push it down through the extruder. Especially if you can tell that the extruder motor is spinning the drive gear (although the filament just isn’t getting pulled into the print head and then extruded), this may be the issue. You will likely need to unload the filament, snip off any stripped section, and reload the filament. However, you should also consider some steps to try to avoid having the filament get stripped again.

• Check your “Retraction” settings (under “PRINT SETTINGS”, “ADVANCED”), especially “Amount” and “Speed”: trying to retract too much filament, or perform the retraction too quickly, can lead to filament stripping. Note that some types of filament (e.g., “soft” PLA) are also less tolerant of retraction.
• Consider increasing the extruder “Temperature” a bit (perhaps 5° or so), so that the plastic melts and flows more easily.
• Try decreasing the speed of printing, so that the extruder drive gear does not need to move filament as quickly. “Print Speed” (under “PRINT SETTINGS”, “BASIC”) is the main extrusion speed control, but other specialized speed settings for particular other parts of the print (“Infill Speed”, raft “Base Speed” and “Surface Speed”, etc.) may also be relevant.

4.

If no extrusion is occurring, even after several layers, your filament may not be well loaded. Check your printer’s instructions for loading filament, and if your printer has a manual extrusion feature, check that manually extruding a bit of filament is working; for instance, for a Polar3D printer, see the Polar3D Printer Guide, Section 4.1.1 regarding loading filament, and Section 3.1.2 discussing the local web interface’s “Extrude 1mm” button.

5.

Finally, if no plastic comes out of the extruder after you’ve checked the above issues, it is likely that your extruder is clogged (melted plastic has puddled, and now solidified inside the extruder). See your printer manufacturer’s instructions for clearing a clogged extruder.