Image Courtesy of Lulzbot
Many issues with the printer can be prevented by ensuring that regular maintenance and cleaning are being performed.
Probe fail, clean nozzle (or some variation) is a common error message that occurs when the nozzle is unable to make contact with one or more washers during auto-leveling at the beginning of a print. Possible causes include dirty washers or the nozzle has built-up filament on the tip, preventing an electrical connection. To resolve this issue, see the Weekly Maintenance tab for wiping the nozzle, cleaning the washers, and checking the wiping pads.
If the nozzle and washers are not the cause of this issue, the next possible issue is that the X-Axis is not level. Use the option in the command tab to have the X-axis automatically level itself, then try starting the print again.
If the first layer of the print is either starting too close to the bed (layer will look very thin and squished) or too high from the bed (may not be adhering to bed at all) you will want to stop the print immediately.
Often, simply restarting the print will fix the issue as it gives the printer a chance to try auto-leveling the Z-axis.
If restarting does not fix the issue, try using the Weekly Maintenance tab on how to wipe the nozzle, clean the washers, and check the wiping pads as, similar to the Probe Fail error, any of those could also be causing the issue.
If that does not fix the issue, try cleaning the printing surface and checking its condition as described in the Weekly Maintenance tab. If the filament is not sticking, it could be from a buildup on the printing surface or from damage.
Image courtesy of LulzBot
This LulzBot troubleshooting post explains more about dealing with issues caused by the printing surface.
If the issue is still occurring, you will need to try changing the Z-offset setting. To do this, follow the instructions from LulzBot here or here.
If the printer is not extruding at the start of a print, first double check the material settings to ensure that it matches the filament loaded into the printer. It is also a good idea to reset the profile to default in case another person has changed temperature settings on the profile and that is causing the issue. See the Problems in Cura section for more information.
As described here, one cause of the printer not extruding at the beginning of a print is that filament has leaked out and there is a void. It is also possible that, during the auto-leveling, filament has slipped partially out of the tool head. To fix this, heat up the hot end to extrusion temperatures and try re-feeding the filament into the hot end and extruding until it is coming out normally.
Also, make sure to check the hobbed bolt when you are having extrusion issues to see if the filament is being ground away. See the Routine Maintenance section for how to clean the hobbed bolt. If the hobbed bolt is clogged with filament, or if the screw on the idler retainer is not tight enough, it will have difficulty pulling the filament into the hot end.
If the steps above do not resolve the issue, it may be jammed. If using PLA, try heating the nozzle to 230 degrees (in case there is any ABS/PETG left in the hot end causing the issue) and purging the printer. You can also try these steps from LulzBot. If you are unable to clear the clog this way, the toolhead may need to be taken apart. Please contact Sarah Holland (sholland@ppld.org, x6611) if you would like assistance with this.
More information on resolving filament jams can be found here.
Warping:
Photo courtesy of Simplify 3D
Warping occurs on prints because plastic, especially ABS, shrinks as it cools. For more details check out this page from Simplify 3D. This is especially noticeable for larger prints. The TAZ Workhorse guide recommends that "turning on Brim in Cura will help increase the surface area of the print, improving part adhesion. If the corners of the part still lift, clean the [printing] surface with IPA/ Isopropyl Alcohol and sand the surface with fine grit sandpaper." See the Weekly Maintenance tab for more info on maintaining the printing surface.
Print coming off bed during printing:
A similar issue is prints coming unstuck from the printing surface completely during printing as seen in the photo below.
This is more common when trying to print multiple pieces or tall, narrow objects. Like warping, maintaining the printing surface and using a brim or raft during printing may help prevent this from occurring.
For more information, read this tutorial from LulzBot on how to maximize bed adhesion.
Probably the most common cause of a bad-looking print (layer shifting, delamination, etc.) is that filament has gotten tangled. When you're putting filament away, make sure to wrap it snugly and lock it into place with the holes on the outside of the spool. Encourage patrons to do the same.
Image courtesy of Matter Hackers
Visit this post from Matter Hackers to learn more about how tangles are formed and how to prevent and fix them.
Another thing to check is the movement of the the three axes to make sure that all parts are moving smoothly. Check screws, motors, belts, and rods to make sure none of those parts need maintenance. View the Maintenance sections for more information.
Simplify3D and RepRap both have great guides for troubleshooting other causes of poor print quality.