If the nozzle is clogging, or if it has old carbon deposits in it then it will feed in lumps and, as the carbon deposits loosen, you’ll get black blobs in the print.
- very slighly loosen the nozzle from the heat block.
- use the printer to heat the nozzle to 200 degrees
- using gloves, take the nozzle off, and using a large needle clean out any pla/abs from inside the nozzle.
You’ll find that, as the nozzle starts to cool any material in the nozzle will begin to solidify but just keep gently picking with a needle and it will come out. (Be careful not to damage the tip of the nozzle!).
If necessary, put the nozzle back on, re-heat it, take it back off and carry on clening out the inside.
Lastly, a little wire wool can be used to clean any burnt material from the outside of the nozzle and a freezer bag twist tie is the perfect size to poke through the nozzle to clean it out.
Once clean, put the nozzle back on and happy printing!