A heating tube is an essential component of a 3D printer's hot end. It is responsible for heating the printer's nozzle to the appropriate temperature for melting and extruding the printing material (usually plastic filaments like ABS or PLA).
The heating tube is made of a resistive wire, such as nichrome or Kanthal, that is wound around a ceramic or metal core. When an electric current flows through the wire, it generates heat, which is transferred to the nozzle. The temperature of the heating tube is controlled by the printer's controller board, which regulates the amount of electrical current flowing through the wire.
In summary, the heating tube is an important part of a 3D printer's hot end that helps to melt and extrude the printing material.