Patent ID: 8268210

Claim:
Method for injection moulding of a moulded part ( 1 ), which has at least two different sections ( 2 , 3 ) being different in the outer diameter (D 1 , D 2 ), wherein a void ( 4 ) is produced in the inner of the moulded part ( 1 ) by causing a projectile ( 5 ) in the direction of a longitudinal axis (L) of the moulded part ( 1 ) through the still molten injection mouldable material in a direction of flow (F), whereto a pressurized fluid is exerted in the void ( 4 ) in the direction of flow (F) behind the projectile ( 5 ) which moves the projectile ( 5 ) into the direction of flow (F), characterized in that a projectile ( 5 ) is used which comprises at least one elastic or plastic section ( 6 ), which section ( 6 ) is delimited by a space ( 7 ) in which the pressurized fluid can enter when causing the projectile ( 5 ) to move, wherein the volume (V) of the space ( 7 ) and for this reason the effective outer diameter (d 1 , d 2 ) of the projectile ( 5 ) can be changed in dependency of the fluid pressure (p), wherein the pressure (p) of the pressurized fluid and/or the pressure in the melt or a process factor being dependent from the pressures is controlled or feed-back controlled in such a manner that the space ( 7 ) and for this reason the effective outer diameter (d 1 , d 2 ) of the projectile ( 5 ) is enlarged and/or reduced in such a way that the effective outer diameter (d 1 , d 2 ) of the projectile ( 5 ) has a predetermined value at least in sections along the feeding path (x) in the direction of flow (F).