Method and apparatus for the additive manufacture of a product

1 . A method for the additive manufacture of a product, wherein a melt is discharged via a 3D print nozzle and the melt is deposited in the form of a melt filament in order to build the product on a print table, wherein the 3D print nozzle and/or the print table are moved in space in accordance with a computer program which is specific for the product,

wherein the melt is produced by an extruder which is in fluid connection with a needle shut-off nozzle, wherein a first pressure is measured by a first pressure sensor located between the extruder and the needle shut-off nozzle and sent to a controller,

wherein the melt is directed to the 3D print nozzle via the needle shut-off nozzle having a housing and a nozzle needle which can be displaced therein, wherein a second pressure is measured by a second pressure sensor located between an outlet opening of the housing and an inlet of the 3D print nozzle and sent to the controller,

wherein, while carrying out a printing procedure, the nozzle needle is moved between a closed position, in which the nozzle needle bears against the outlet opening of the housing which is in fluid communication with the 3D print nozzle and which closes said outlet opening, and an open position, in which the nozzle needle is at a distance from the outlet opening of the housing which can be specified,

wherein, for the additive manufacture of the product, a volumetric flow of melt being discharged from the 3D print nozzle is specified by a shape of an outlet opening of the 3D print nozzle and therefore of a geometry of the melt filament to be deposited on the one hand and the speed of movement of the 3D print nozzle and/or of the print table on the other hand,

wherein the nozzle needle is moved between the closed position and the open position while carrying out the printing procedure in a manner such that during the additive manufacture of the product, the specified volumetric flow of melt being discharged from the 3D print nozzle is maintained,

wherein a control curve which is a function of the geometry of the 3D print nozzle, of the shape of the outlet opening of the 3D print nozzle and therefore of the geometry of the melt filament to be deposited, is stored in the controller and this control curve is used during the additive manufacture of the product,

wherein a channel cross section between conically configured surfaces of the nozzle needle and housing is varied in accordance with the control curve, and

wherein the volumetric flow of melt is regulated via the varied channel cross section and a comparison between the first pressure and the second pressure.

2 . The method as claimed in claim 1 ,

wherein the nozzle needle has a needle tip which tapers conically at least in sections, in that for this purpose, the front end of the housing is appropriately conical in configuration in a manner such that the needle tip and the front end of the housing are in close contact against one another in the closed position of the needle shut-off nozzle and the throughput of melt is interrupted, and in that by moving the nozzle needle, the channel cross section is varied in accordance with the specified volumetric flow.

3 . The method as claimed in claim 1 ,

wherein prior to carrying out dry runs in which the 3D print nozzle and/or the print table are moved without depositing a melt filament, the nozzle needle is initially retracted and subsequently moved into the closed position.

4 . The method as claimed in claim 1 ,

wherein the fluid connection employed is a pipe or a tube.

5 . The method as claimed in claim 2 ,

wherein a melt pump is provided between the extruder and the needle shut-off nozzle.

6 . The method as claimed in claim 1 ,

wherein the relative velocity between the 3D print nozzle and the print table is employed in order to regulate the volumetric flow.