How to clean a hot clog in the head of an FDM type 3D printer

How to clean a hot clog in the head of an FDM type 3D printer

Residues are inevitable for FDM 3D printers for several reasons: small amounts of plastic are scorched by the overheated hot end, causing them to accumulate inside the nozzle; contamination from foreign bodies inside the wire after it has been produced; dust that has fallen on the surface of the wire reel is scorched and accumulates; trash is accidentally discarded into the hot end, etc. As a result FDM 3D printers often suffer from under-extrusion: for no apparent reason, but the extruder is unable to extrude enough material. If the extruder is pushing the wire at this time and the reel is spinning freely, there is only one possible cause: a blockage in the hot end.

Hot blockage: a phenomenon in which the gas flows in a tube of equal cross-section and is heated, starting with an increase in flow rate and no change in flow rate. When the heat is applied to a certain value or more, the flow rate drops and the flow rate remains at the critical speed. Print nozzle blockage (out of the filament is not smooth) as a normal phenomenon, the so-called hot end is the heating part of the 3D printing nozzle, this part is heated through the supplies will melt and squeeze out. Above the gold nozzle is the heated aluminium block, which connects the heating and temperature measurement lines. Inside the nozzle and the heated aluminium block is a PTFE tube (Teflon tube) with a melting point of 327°C, which guides the material in the direction of the nozzle. It is also important to note that the heating wire is the wire that heats the hot end of the 3D printhead and is connected to the heated aluminium block. In many cases, if you find that there is a problem with the heating of the 3D printhead, for example, if the printhead temperature is too low, resulting in a blockage of the material, it is likely that the heating cable is the cause of the problem. In addition to the heating cable, there is also a temperature measurement cable connected to the heated aluminium block. This is used to detect the heating temperature of the print head and to prevent carbonisation of the consumables caused by high print head temperatures. As with the heating cable, if you find that the temperature is abnormal when heating, it is possible that there is a problem with the temperature measurement cable.

So how do you clean up the print residue caused by the blockage?
The cold drawing technique is actually quite easy to operate. Insert a piece of wire and heat the extruder to allow the wire to extrude some from the nozzle (if it does clog it may not be able to) or heat it to operating temperature. The 3D printer is then switched off. Usually when the hot end is at operating temperature, the wire is free to be pulled out. When it cools completely, the wire will solidify and cannot be pulled out. The trick is to wait until the temperature is slightly below the solidification level and quickly pull the wire out, which should be mostly solid at this point. As the wire solidifies, it is possible to catch residue that is scattered in the hot end. It may also be found to be contaminated with a black substance or even have some visible debris. There will be more inside the solid wire. Cut off this contaminated section and repeat the process. It may take a few minutes to heat and cool the hot end, but this is much easier than other methods. Repeat as many times as necessary and the wire will eventually be pulled out very clean, which means that the end of the wire is clean.