The hotend can not be removed properly because it is dirty, or it is dirty and needs to be cleaned.
Why we recommend that you clean the outside of the hotend regularly：
In the printing process, the hotend of the internal heat melting polymers have a certain degree of viscosity, a small portion of which will be adhered to the outside of the hotend, becoming residues. After a period of normal working of the printer, the accumulation of these residues into a large number of repeated heating for a long time will gradually decompose, from chewing gum-like to tar-like, until completely carbonised. This reduces the disassembly efficiency of the hotend with the quick release design because of the adhesion, and may even make it difficult to disassemble because it is firmly adhered and wrapped. Therefore, it is recommended that the outside of the hotend be cleaned regularly to ensure that the quick release design remains effective.
Cut the filament and heat the hotend to 250°C;
Remove the front cover of the tool head, take off the silicone sock of the hotend, use pliers to open the latch and remove the hotend;
Fold the prepared wood fibre paper towel over and over again, and while the hotend is still warm, rub the paper towel over and over again until it is shiny and clean.
Use a folded wood fibre paper towel to wipe the heat-conducting surface of the heated floor base.
If the process cannot be completed in one go, the safety protection of the heating base can be deactivated using "Settings - Maintenance - Maintenance Mode", which allows the heating base to be heating up without the hotend being loaded.
Place the hotend back in to heat to temperature and repeat steps 3~4 again until cleaning is complete.
Wait for the hotend and heating base to cool down to room temperature (about 5min after setting the temperature) and put back the hotend to complete this cleaning.