FEASIBILITY STUDY ON IMPROVEMENT OF ORBIT DETERMINATION ACCURACY OF SELENE BY IMPROVEMENT OF LUNAR GRAVITY MODEL DURING ITS OPERATION

An extruder for extrusion manufacturing a rod of hard metal or ceramic with at least one helical inner bore. A plasticized mass of hard metal or ceramic is simultaneously forced through a die and twisted. Either the mass is twisted uniformly over the cross-section of the billet by a spinner immersed in the mass or the spinner is rotated by the mass. The mass emerges either subject to torsion or entirely or mostly without torsion from a smooth downstream channel through the die. A filament-shaped material extends or is injected into the mass to produce the inner bore or bores.