Nozzle cleaning

Question

A few minutes after finishing a print job, the filament is solidified in the nozzle and the nozzle-throat. When I start another print job a while later, the filament is not sufficiently melted and the nozzle is obstructed. Do I need to clean the nozzle after every print job ? or is there a practical method to overcome this difficulty ?

Answer 1

To start a print, the printer has first get up to print temperature, re-melting the plastic in the nozzle and hotend. To get better results, it is usually a very good idea to "prime" the nozzle to make sure we have nicely melted plastic in the nozzle and pushed out the old. Some priming methods have been discussed here.

Answer 2

I had this issue until I started doing the following:

1. If you are going to print subsequent jobs (one after the other), then ensure you keep the extruder end at print temperature while you are preparing the next job. For me on my Anet A8, I'd just tell the printer to preheat for PLA (or directly set a temp for the filament being used). This keeps the heat up in the hot end and should allow you to start printing right away when everything is ready. Please note, this will usually cause the nozzle to ooze a little bit of filament as it sits. Just ensure you swipe it clean before you actually start the next print to alleviate and stringing issues when you press the "GO" button. As an alternative, you could attach a line at the end of your print which would send the G-code to keep the printer up to temperature instead of cooling off after a print is finished. If you do this, though, you have to ensure you actually do allow it to shut down when you aren't printing so as to not waste resources.
2. If you are not going to print subsequent jobs, pull the filament out of the extruder. On my Anet A8, right after the print has finished, but before things start cooling, I will press the spring loaded part of the extruder head (the part which captures the filament against the extruder gear), then push the filament into the extruder and quickly out. This usually ensures you don't leave a lot of filament languishing in the extruder head and will make it easier to load the filament the next time you want to print.