The Energon Transfer Device was a piece of Decepticon technology that was created specifically for the Insecticon Army where it would draw upon the materials the Insecticons devoured and convert them into Energon cubes.
It appeared as a series of glass cylinders where the Transformer would enter and two tubes would descend, connecting to the structure of the mechanoid whereupon it would draw energy into a central pipe connecting all the cylinders to a larger machine further in the base where the energy would be compressed into Energon cube format.
Generation One Cartoon
Megatron used this device on the Insecticon Army in order to convert the material they ate into energon. Only a few small cubes were given to the Insecticons which Megatron claimed to be because of the costly process of the transfer device but this was simply a lie in order to maximise the Decepticon stores of energy.