Printhead for a 3D printer and method for operating a printhead

Abstract

The invention relates to a printhead (100) for a 3D printer (150), comprising a nozzle device (80) for dispensing a liquid phase (12) of at least one printable material (10). The invention is characterized in that the printhead (100) comprises an adapter device (50), wherein at least the nozzle device (80) and two extruders (110, 120) for providing the at least one printable material (10) are arranged on the adapter device (50). Furthermore, the invention relates to a method (200) for operating a printhead (100) according to the invention.

Description

The present invention relates to a printhead for a 3D printer and to a method of operating a printhead.Prior ArtA 3D printer for a variable viscosity material receives a solid phase of this material as a starting material, generates a liquid phase therefrom, and selectively applies this liquid phase to the sites associated with the object to be generated. Such a 3D printer comprises a print head in which the starting material is processed ready for printing. Furthermore, means are provided for generating a relative movement between the print head and the working surface on which the object is to be produced. In this case, either only the print head, only the working surface or else both the print head and the working surface can be moved.The printhead has a first operating state in which liquid material exits from it and a second operating state in which no liquid material exits from it. The second operating state is assumed, for example, when a different position on the work surface is approached and no material is to be discharged there on the way. A switch can be made between the two operating states of the print head, for example, by switching the advance of the solid starting material on or off.The most common is fused deposition modeling (FDM), in which a filament is melted from the starting material in an electrically heated extruder die and is applied layer by layer to a platform. In the form of such a filament, the starting material is very expensive.DE 10 2021 202649 A1 discloses a print head for a 3D printer, wherein a granulate is plasticized therein via a piston and a heated section. When the piston presses on the granulate, the granulate is compacted, thereby closing the nozzle of the print head. The nozzle can be closed, for example, by a closure valve or by positioning the print head on a plate in the construction space of the printer. It is also proposed that an already printed region of a component can be approached in order to close the nozzle.A disadvantage of these solutions is that, in the case of a closure valve on the print head, the installation space requirement around the nozzle becomes greater, which can possibly lead to collisions of the print head with the component. Further, the weight of the print head increases, thereby restraining the dynamics in printing. The positioning of the print head on a construction plate can lead, on the one hand, to wear on the nozzle, which reduces the print quality, and, on the other hand, the print head has to either move horizontally to the construction plate or be moved away from it in order to close the nozzle.The object of the invention is to provide a print head for a 3D printer and a method for operating a print head, which print head enable an optimized printing process, wherein high-quality melt is to be provided in reproducible quality.Disclosure of the InventionIn the context of the invention, a 3D printer having a print head and a method for operating a print head have been developed.The invention relates to a print head for a 3D printer, comprising a nozzle device for discharging a liquid phase of at least one printable material. According to the invention, the print head comprises an adapter device, wherein at least the nozzle device and two extruders for providing the at least one printable material are arranged on the adapter device.The print head according to the invention, comprising the nozzle device and two extruders on an adapter device or adapter plate of a print head for a 3D printer, advantageously enables a continuous printing process, since, for example, one extruder can carry out a filling process while the second extruder carries out the printing process through the nozzle device. Once the filling process of the first extruder is completed, it can continue the printing process through the die device. The printing process therefore no longer has to be interrupted, as a result of which process fluctuations can be reduced in an advantageous manner. In addition, the printing time for the component to be produced is shortened.In addition, a high availability of homogeneous melt is achieved, in particular when using plastic granules as starting material. The adapter device can also be called a valve block.In addition, both extruders can also be filled with different starting material, whereby the processing of two materials with a print head is advantageously made possible.In a further development of the invention, the adapter device has two channels, wherein the die device is connected to the first extruder via the first channel and the die device is connected to the second extruder via the second channel.In a preferred development of the invention, the die device comprises a valve for regulating the inflow of the liquid phase from the respective extruders to a die of the die device.The valve thereby enables selective switching between the two extruders, whereby the waiting time for the filling can be reduced or completely avoided when the same starting material is used. Furthermore, in the case of special print heads, the necessary travel path for closing the nozzle during the filling process is dispensed with.A virtually uninterrupted printing process advantageously allows the component quality to be improved. Both the optics are improved on the component by the continuous printing process and the layer adhesion increases. Interruptions during the lowering of the nozzle or during the stopping of the printing process are thus advantageously avoided.Furthermore, by using the valve, so-called additional nozzle closure regions in the construction chamber of the printer, the so-called fill position, can be dispensed with.In a development, the nozzle device comprises an actuator for controlling the valve. The valve controlled by the actuator can advantageously be adjusted in such a way that the valve can switch the volume flow from the extruder back and forth to the die device.In a further development, the valve for regulating the inflow of the liquid phase from the respective extruders to the die is designed as a diverter.In a further development, the valve is rotatably mounted in the nozzle device and a through-flow opening can be produced between the channels of the adapter device and the nozzle by corresponding rotation of the valve.The valve thus advantageously serves for regulating the volume flow between the die device and the extruders.In a further development, the size of the flow opening for changing a volume flow of the liquid phase can be variably adjusted by rotating the valve.The adjustment of the valve, in particular the variable adjustment, enables a uniform volume flow from one extruder to the other to the die, whereby an uninterrupted transition of the two melts is advantageously achieved.The volume flow can be controlled exactly at any time, whereby an exact process control can be achieved in an advantageous manner by the actual volume corresponding to the desired volume.Achieving a uniform volume flow leads to improved component properties, in particular in the Z direction of the component.In a further development, the valve has a horizontal through bore and a vertical opening, wherein a connection between the channels of the adapter device and the nozzle can be produced by the horizontal through bore and the vertical opening of the valve.In an advantageous development, the horizontal through bore of the valve has the same diameter as the channels in the adapter device. Because the channels in the adapter device, the so-called melt channels and the through bore of the valve, the so-called inflow channel, have the same diameter, dead volumes, among other things also through undercuts, can be advantageously avoided.In a further development, the horizontal through bore has a chamfer on the outer side of the valve.The chamfer on the outer side of the valve ensures an improved pressure equalization of the melt streams of the extruders when the valve is switched between the two channels of the adapter device. In addition, shear forces in the melt which arise during a change in cross section or during the closing of the respective channel are advantageously avoided.In a development, the extruders each comprise an actuator device for controlling a piston, one or more heating elements for converting the printable material from a solid phase into a liquid phase, and a device for fastening the extruders to the adapter device.In a further development, a kidney piece is arranged in each case between the extruders and the respective channels of the adapter device, wherein the kidney piece is of disk-shaped design and has vertical through-openings.In a further development, the adapter device comprises recesses for heating elements for tempering the liquid phase.Furthermore, in a development, the adapter device comprises pressure sensors and / or temperature sensors.The quality of the melt can be controlled by the pressure sensors and / or temperature sensors and, if appropriate, regulated via the heating elements and / or the actuation of the extruders, whereby the quality of the melt and thus also that of the component is advantageously ensured.The invention further relates to a method for operating the print head according to the invention, the method comprising:The control of the valve in such a way that the printing process is carried out by the first extruder, or the control of the valve in such a way that the printing process is carried out by the second extruder, or the control of the valve in such a way that the printing process is carried out by both extruders, or the control of the valve in such a way that the printing process is interrupted.Further measures which improve the invention are described in more detail below together with the description of the preferred exemplary embodiments of the invention on the basis of figures.BRIEF DESCRIPTION OF THE DRAWINGThe following are shown: FIG. 1 is a view of a printhead of a 3D printer according to the present invention; FIG. 2 is another view of the printhead of the present invention; FIG. 3 shows a view of an adapter device with a nozzle device; FIG. 4 is a cross-sectional view of the adapter device with two extruders; FIG. 5 is a cross-sectional view of the adapter device; FIG. 6 shows a cross-sectional view of the adapter device with the nozzle device; FIG. 7 shows a cross-sectional view of the adapter device with a valve in a first position; FIG. 8 shows a cross-sectional view of the adapter device with the valve in a second position; FIG. 9 shows a sectional view of the adapter device with the valve in a third position, and FIG. 10 shows a sectional view of the adapter device with the valve in a fourth position.Exemplary EmbodimentsFIGS. 1 and 2 show views of a print head 100 according to the invention for a 3D printer 150 comprising a nozzle device 80 for discharging a liquid phase 12 or a melt of at least one printable material 10, wherein the print head 100 comprises an adapter device 50, wherein at least the nozzle device 80 and two extruders 110, 120 for providing the at least one printable material 10 are arranged on the adapter device 50.To fill the print head 100 with printable material 10, the extruders 110, 120 are each filled via a feed device 9. The feed device 9 is funnel-shaped, wherein the material 10, which is preferably a granulate, is introduced from above into an opening of the feed device 2.An actuator 6 for controlling the nozzle device 80 is arranged at the upper end of the nozzle device 80, and a nozzle 8 of the print head 100 is arranged at the lower end of the nozzle device 80. The actuator 6 does not have a feed function. The discharge of melt 12 is directly ensured by extruders 110, 120, which directly control the material discharge at die 8 by the feed of the respective pistons (see FIG. 4 ).FIG. 3 shows a view of the adapter device 50 with the nozzle device 80 of the print head 100, wherein the nozzle device 80 is inserted in a receptacle 90 of the adapter device 50 and the adapter device 50 comprises further receptacles 91, 92 for the two extruders 110, 120 of the print head 100.FIG. 4 shows a cross-sectional view of the adapter device 50 with two extruders 110, 120, wherein the extruders 110, 120 each comprise: an actuator device 111, 121 (see below. FIG. 2 ) for controlling a piston 112, 122, one or more heating elements 60 for converting the printable material 10 from a solid phase 10 into a liquid phase 12, and a device 116, 126 for fastening the extruders 110, 120 to the adapter device 50.The adapter device 50 comprises recesses 55, 56 for the heating elements 60 for tempering the liquid phase 12.A kidney piece 117, 127 is arranged in each case between the extruders 110, 120 and the respective channels 51, 52 of the adapter device 50, wherein the kidney piece 117, 127 is of disc-shaped design and has vertical through-openings 118, 128. The liquid phase 12 or the melt 12 is pressed and mixed by the kidney piece 117, 127 by applying a stroke movement of the piston 112, 122, whereby a homogeneous melt is produced. The melt 12 is then forced through the channels 51, 52 to the nozzle device 80. Both extruders 110, 120 have a common die 8 as a result of this design. the respective extruder 110, 120 projects with the respective kidney piece 117, 127 directly into the adapter device 50, and the kidney piece 117, 127 directly adjoins the channels 51, 52 or melt channels.FIG. 5 shows a cross-sectional view of the adapter device 50 with the nozzle device 80 in a plan view and FIG. 6 shows a cross-sectional view of the adapter device 50 with the nozzle device 80 in a side view. The adapter device 50 has two channels 51, 52, wherein the die device 80 is connected to the first extruder 110 via the first channel 51 and the die device 80 is connected to the second extruder 120 via the second channel 52.The nozzle device 80 comprises a valve 20 for regulating the inflow of the liquid phase 12 from the respective extruders 110, 120 to the nozzle 8 of the nozzle device 80. Furthermore, the nozzle device 80 comprises the actuator 6 for controlling the valve 20. The valve 20 for regulating the inflow of the liquid phase 12 from the respective extruders 110, 120 to the nozzle 8 is designed as a switch, wherein the valve 20 is rotatably mounted in the nozzle device 80 and a flow opening 22 between the channels 51, 52 and the nozzle 8 can be produced by corresponding rotation of the valve 20. Outside the valve 20 a threaded sleeve 26 is arranged, which can be rotated via the actuator 6. In the embodiment or switching position shown in FIG. 5, the valve 20 is set in such a way that a throughflow opening 22 is formed between the channel 52 of the second extruder 120 and the die 8. The valve 20 has a horizontal through-bore 23 and a vertical opening 24, wherein a connection between the channels 51, 52 of the adapter device 50 and the nozzle 8 can be established through the horizontal through-bore 23 and the vertical opening 24 of the valve 20.In the embodiment shown here, the horizontal through bore 23 of the valve 20 has the same diameter as the channels 51, 52 in the adapter device 50. The horizontal through bore 23 also has a chamfer 25 on the outer side of the valve 20.The size of the flow opening 22 for changing a volume flow of the liquid phase 12 can be variably adjusted by rotating the valve 20, wherein the flow opening 22 can be varied by arranging the opening cross section of the horizontal through bore 23 of the valve 20 offset to the opening cross section of the respective channel 51, 52. The through-flow opening 22 changes in this case.Furthermore, the adapter device 50 comprises pressure sensors 70 and / or temperature sensors 71. In order to ensure the quality of the melt 12 and thus also of the component to be finished, the temperature and the pressure in the adapter device 50 are regulated. For this purpose, in the embodiment of the adapter device 50 shown in FIG. 5, four heating elements 60 are mounted. Two of these are parallel to the channels 51, 52, or melt channels, and two are parallel to the valve 20, or to the switch. The temperature is measured by temperature sensors 71 on the adapter device 50 and in the vicinity of the nozzle 8.The pressure is measured at the melt channels 51, 52 by pressure sensors 70, respectively.FIGS. 7 to 10 show positions of the valve 20 of the nozzle device 80 in various method steps of a method 200 for operating the print head 100.FIG. 7 shows a cross-sectional view of the adapter device 50 with the valve 20 in a first position, wherein the actuation 210 of the valve 20 takes place in such a way that the printing process is carried out by the first extruder 110. The first channel 51 is open and the second channel 52 is closed. Here, only the valve 20, or the switch, is controlled to the corresponding position.FIG. 8 shows a cross-sectional view of the adapter device 50 with the valve 20 in a second position, wherein the actuation 220 of the valve 20 takes place in such a way that the printing process is carried out by the second extruder 120. The first channel 51 is closed and the second channel 52 is open. Here, only the valve 20, or the switch, is controlled to the corresponding position.FIG. 9 shows a cross-sectional view of the adapter device 50 with the valve 20 in a third position, wherein the actuation 230 of the valve 20 takes place in such a way that the printing process is carried out by both extruders 110, 120. The first channel 51 is open and the second channel 52 is open. The pressure through both extruders 110, 120 is possible, thereby allowing pressure equalization and providing for an uninterrupted change between extruders 110, 120. Here, only the valve 20, or the switch, is controlled to the corresponding position. In order that better pressure compensation takes place in this position during the changeover at the valve 20 or the switch between the extruders 110, 120 and in addition no shear forces arise in the melt 12 during a change in cross section or during the closing of the respective channel 51, 52, the horizontal through bore 23 is (see above. FIG. 5 ) is provided with a chamfer 25 on the outer side of the valve 20.FIG. 10 shows a cross-sectional view of the adapter device 50 with the valve 20 in a fourth position, wherein the activation 240 of the valve 20 takes place in such a way that the printing process is interrupted. The first channel 51 is closed and the second channel 52 is closed, thereby interrupting the printing process. Here, the threaded sleeve 26 is additionally rotated, in which the valve 20 or the diverter is arranged concentrically.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2021 202649 A1

[0005]

Claims

Print head (100) for a 3D printer (150), comprising a nozzle device (80) for discharging a liquid phase (12) of at least one printable material (10), characterized in that the print head (100) comprises an adapter device (50), wherein at least the nozzle device (80) and two extruders (110, 120) for providing the at least one printable material (10) are arranged on the adapter device (50).Print head (100) according to Claim 1, characterized in that the adapter device (50) has two ducts (51, 52), the die device (80) being connected to the first extruder (110) via the first duct (51), and the die device (80) being connected to the second extruder (120) via the second duct (52).Print head (100) according to one of the preceding claims, characterized in that the nozzle device (80) comprises a valve (20) for regulating the inflow of the liquid phase (12) from the respective extruders (110, 120) to a nozzle (8) of the nozzle device (80).Print head (100) according to one of the preceding claims, characterized in that the nozzle device (80) comprises an actuator (6) for controlling the valve (20).Print head (100) according to one of the preceding claims, characterized in that the valve (20) for regulating the inflow of the liquid phase (12) from the respective extruders (110, 120) to the nozzle (8) is designed as a diverter.Print head (100) according to one of the preceding claims, characterized in that the valve (20) is mounted rotatably in the nozzle device (80) and a throughflow opening (22) between the channels (51, 52) and the nozzle (8) can be produced by corresponding rotation of the valve (20).The print head (100) according to any one of the preceding claims, characterized in that the size of the flow opening (22) for changing a volume flow of the liquid phase (12) can be variably adjusted by rotating the valve (20).Print head (100) according to one of the preceding claims, characterized in that the valve (20) has a horizontal through-bore (23) and a vertical opening (24).Print head (100) according to one of the preceding claims, characterized in that a connection between the channels (51, 52) of the adapter device (50) and the nozzle (8) can be produced by the horizontal through-bore (23) and the vertical opening (24) of the valve (20).The print head (100) according to any one of the preceding claims, characterized in that the horizontal through bore (23) of the valve (20) has the same diameter as the channels (51, 52) in the adapter device (50).Print head (100) according to one of the preceding claims, characterized in that the horizontal through bore (23) has a chamfer (25) on the outer side of the valve (20).Print head (100) according to one of the preceding claims, characterized in that the extruders (110, 120) each comprise: an actuator device (111, 121) for controlling a piston (112, 122), one or more heating elements (60) for converting the printable material (10) from a solid phase (10) into a liquid phase (12), and a device (116, 126) for fastening the extruders (110, 120) to the adapter device (50).Print head (100) according to one of the preceding claims, characterized in that a respective kidney piece (117, 127) is arranged between the extruders (110, 120) and the respective channels (51, 52) of the adapter device (50), wherein the kidney piece (117, 127) is disc-shaped and has vertical through-openings (118, 128).Print head (100) according to one of the preceding claims, characterized in that the adapter device (50) comprises recesses (55, 56) for heating elements (60) for tempering the liquid phase (12).Print head (100) according to one of the preceding claims, characterized in that the adapter device (50) comprises pressure sensors (70) and / or temperature sensors (71).Method (200) for operating a print head (100) according to one of the preceding claims, characterized in that the method comprises: controlling (210) the valve (20) that the printing process is carried out by the first extruder (110), or controlling (220) the valve (20) that the printing process is carried out by the second extruder (120), or controlling (230) the valve (20) that the printing process is carried out by both extruders (110, 120), or controlling (240) the valve (20) that the printing process is interrupted.

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