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 at least two extruders (110, 120) for providing the at least one printable material (10) and the nozzle device (80) with a valve (20) for controlling a volumetric flow rate of the liquid phase (12) from the respective extruders (110, 120) to a nozzle (8) of the nozzle device (80). 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.DE 10 2016 213439 A1 discloses a screw extruder with an adjustable nozzle, wherein the nozzle can change a volume flow from 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 at least two extruders for providing the at least one printable material and the nozzle device with a valve for regulating a volume flow of the liquid phase from the respective extruders to a nozzle of the nozzle device.The print head, comprising the die device and two extruders, 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 die 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.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.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. The valve for regulating the inflow of the liquid phase from the respective extruders to the die can be designed as a diverter. Furthermore, the regulation of the volume flow improves the discharge when the print head is moved on and off to the respective printing positions. It is advantageously avoided that aggregates or threads are formed at the beginning or end of a web.In a development, the print head comprises an adapter device having two channels, wherein the adapter device has two channels, wherein the nozzle device is connected to the first extruder via the first channel and the nozzle device is connected to the second extruder via the second channel. The adapter device can also be referred to as a valve block or adapter plate.In a development, the nozzle device has two nozzle bodies arranged concentrically one inside the other, wherein the inner nozzle body is arranged within a threaded sleeve in such a way that the inner nozzle body can be moved relative to the outer nozzle body by rotation of the threaded sleeve.In a further development, the nozzle device comprises an actuator for controlling the valve and the threaded sleeve. The valve can be controlled by the actuator and the threaded sleeve can be controlled by a driver of the actuator.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. Furthermore, the threaded sleeve controlled by the actuator ensures the relative movement of the inner nozzle body with respect to the outer nozzle body, as a result of which the nozzle cross section changes and the volume flow of the liquid phase or of the melt thereby changes.The threaded sleeve provides the stroke and rotation of the inner nozzle body.The valve can be rotatably mounted in the nozzle device and a through-flow opening can be produced between the channels of the adapter device, bores of the threaded sleeve and the nozzle by corresponding rotations of the valve and / or of the threaded sleeve. The valve thus advantageously serves for regulating the volume flow between the die device and the extruders.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.Furthermore, the valve can have 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. The horizontal through bore of the valve can have 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.Furthermore, the horizontal through bore can have 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 nozzle device has an outlet opening, the cross section of which can be variably adjusted for changing a volume flow of the liquid phase. The cross section of the outlet opening of the nozzle device, or the nozzle cross section, is changed by the relative movement of the inner nozzle body to the outer nozzle body in such a way that the volume flow of the liquid phase, or of a melt, changes. The two nozzle bodies arranged one inside the other thus achieve that the print head can print with different volume flow depending on the setting, whereby a further print head can be advantageously dispensed with if a plurality of nozzle diameters would be necessary during a print job or printing process. During printing with a large opening cross section of the outlet opening of the nozzle device, the printing process can be accelerated, in particular when regions of the component to be printed have to be filled. A nozzle change can be avoided by the nozzle device, whereby a reduction of the downtime by conversion is advantageously achieved. This shortens the printing process. In addition, the adjustment effort is reduced by a nozzle change of the print head. The component printed with the nozzle device of the print head can furthermore have better optics, since for example the outer contour of the component is printed by a smaller cross section of the outlet opening. A smaller cross section means a small nozzle diameter, or a smaller nozzle, respectively, whereby a high accuracy of printing is achieved. The larger cross section enables an increase in the material throughput and thus a faster filling of the component, whereby a faster filling of the component can be achieved with the same path position of the print head. Furthermore, by using the nozzle device, the component properties, such as strength, can be improved since a higher density can be achieved between the printed layers, or the layers, since the fill density is improved. Further, a print head having the nozzle device is made compact, whereby weight reduction of the print head can be achieved.In a further development, in a first operating state of the print head, the outlet opening of the nozzle device is formed by a nozzle opening of the inner nozzle body. This achieves a small nozzle diameter, as a result of which it is possible to print into fine outer contours which advantageously have improved optics.In a further development, in further operating states of the print head, the outlet opening of the nozzle device is formed by an opening cross section, wherein this results from the relative movement of the inner nozzle body to the outer nozzle body. This achieves a variable nozzle diameter, whereby wider contours can be printed if necessary, or regions of the component can be filled. As a result, the printing process can be advantageously accelerated. Furthermore, the outer nozzle body can have a recess on its inner wall and the inner nozzle body has a lateral opening at the level of the recess of the outer nozzle body.The extruders can each comprise an actuator device for controlling a piston, one or more heating elements for converting the printable material from a solid phase to a liquid phase, and a device for fastening the extruders to the adapter device. A kidney piece can be arranged between the extruders and the respective channels of the adapter device, wherein the kidney piece is disk-shaped and has vertical through-openings.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 may include: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 is a cross-sectional view of the nozzle device; FIG. 8 is a view of the nozzle device; FIG. 9 shows a sectional view in a side view of the nozzle device in a first operating state; FIG. 10 shows a cross-sectional view in a plan view of the nozzle device in a first operating state; FIG. 11 is a cross-sectional view in a side view of the nozzle device in a second operating state; FIG. 12 shows a cross-sectional view in a plan view of the nozzle device in a second operating state; FIG. 13 shows a cross-sectional view of the adapter device with a valve in a first position; FIG. 14 shows a cross-sectional view of the adapter device with the valve in a second position; FIG. 15 shows a sectional view of the adapter device with the valve in a third position, and FIG. 16 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 disk-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 diverter, wherein the valve 20 is rotatably mounted in the nozzle device 80 and a throughflow opening 22 can be produced between the channels 51, 52 of the adapter device 50, bores 74, 75 of the threaded sleeve 26 and the nozzle 8 by means of corresponding rotations of the valve 20 and / or of the threaded sleeve 26. 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, the bore 75 of the threaded sleeve 26 and the nozzle 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.FIG. 7 shows a cross-sectional view of the nozzle device 80, wherein the nozzle device 80 is suitable for discharging the liquid phase 12, wherein the nozzle device 80 has an outlet opening 8, the cross section of which can be variably adjusted for changing a volume flow of the liquid phase 12. The nozzle device 80 has two nozzle bodies 61, 62 arranged concentrically one inside the other, wherein the inner nozzle body 61 is arranged within the threaded sleeve 26 in such a way that the inner nozzle body 61 is movable relative to the outer nozzle body 62 by rotation of the threaded sleeve 26. The cross section of the outlet opening 8 of the nozzle device 80, or the nozzle cross section, is changed by the relative movement of the inner nozzle body 61 with respect to the outer nozzle body 62, in such a way that the volume flow of the liquid phase 12, or of a melt, changes. The two nozzle bodies 61, 62 arranged one inside the other thus achieve that the print head 100 can print with different volume flow depending on the setting. The melt 12 is supplied via the flow opening 22. The melt 12 fed in can be pressed into the die device 80 via the extruders 110, 120. The threaded sleeve 26 can be actuated by the actuator 6 of the nozzle device 80. A transmission device 85 driven by the actuator 6 between the actuator 6 and the threaded sleeve 26 ensures a lifting and rotational movement of the inner nozzle body 61 relative to the outer nozzle body 62, The entry of liquid melt 12 upward in the direction of the actuator 6 is ensured by an actuator cooling 7.The actuator 6 and the threaded sleeve 26 produce a lifting mechanism which ensures that the inner nozzle body 61 is lifted during the printing process with a short interruption of the mass discharge. This leads to an interruption because the threaded sleeve 26 is rotated and thus the valve 20 or the shunt is also rotated by 180° and because the valve 20 is rotated by 180° beyond a stop and thus also the threaded sleeve 26 and thus the outlet openings of the two channels 51, 52 or melt channels are closed for a short time.FIG. 8 shows a view of the nozzle device 80 of the print head 100, wherein a driver 73 is arranged below the actuator 6 on the transmission device 85 of the actuator 6, via which driver the threaded sleeve 26 can be actuated. The driver 73 is disposed within a recess 76 of the threaded sleeve 26 and is free to rotate within the recess 76. As soon as the driver 76 abuts a side surface 77 of the recess 76, a force acts on the threaded sleeve 26 and it rotates along in the direction of rotation of the driver 73. Between the driver 73 and the nozzle 8 there are arranged the bores 74, 75 of the threaded sleeve 26. The actuator 6 rotates the driver 73 clockwise or counter-clockwise. Since the valve 20, not shown here, is directly connected to the driver 73, the latter is rotated directly as well. The change and regulation of the volume flow in the channels 51, 52 takes place only in the intermediate space of the recess 76 of the threaded sleeve 26, wherein the recess 76 defines the adjustment range. This ensures that the threaded sleeve 26 does not move within this adjustment range and as a result no flow change is caused at the nozzle 8.FIGS. 9 to 12 show operating states of the nozzle device 80 which can be produced by a rotation of the threaded sleeve 26.FIG. 9 shows a cross-sectional view in a side view of the nozzle device 80 in a first operating state and FIG. 10 shows a cross-sectional view in a plan view. The outer nozzle body 62 has a recess 65 on its inner wall 87 and the inner nozzle body 61 has a lateral opening 63 at the level of the recess 65 of the outer nozzle body 62. In the first operating state of the print head 100 shown here, the lateral opening 63 of the inner nozzle body 61 is closed by the inner wall 87 of the outer nozzle body 62, so that the outlet opening 8 of the nozzle device 80 is formed by a nozzle opening 81 of the inner nozzle body 61. This achieves a small nozzle diameter of the nozzle device 80. The melt 12 is forced through a channel 86 arranged in the inner nozzle body 61 to the nozzle opening 81 of the inner nozzle body 61. The small cross section means a small nozzle diameter 81, or a smaller nozzle, respectively, thereby achieving high accuracy of printing. In this operating state, a seal is achieved between the two nozzle bodies 61, 62 by the outer surface or lateral surface 68 of the inner nozzle body 61 with respect to the outer nozzle body 62 in the region of the outlet opening 8.FIG. 11 is a cross-sectional view in a side view of the nozzle device 80 in a second operating state, and FIG. 12 is a plan view. In the operating state shown here, the outlet opening 8 of the nozzle device 80 is formed by an opening cross section 82, which results from the relative movement of the inner nozzle body 61 with respect to the outer nozzle body 62. The transmission device 85 driven by the actuator 6 between the actuator 6 and the threaded sleeve 26 provided in this operating state a lifting and rotational movement of the inner nozzle body 61 relative to the outer nozzle body 62, the inner nozzle body 61 was rotated by 180° and the simultaneous lifting movement upwards provides a gap 66 between the inner nozzle body 61 and the outer nozzle body 62, In the second operating state of the print head 100 shown here, the lateral opening 63 of the inner nozzle body 61 is aligned with the recess 65 of the outer nozzle body 62, whereby a connection is established between the opening 63 and the recess 65. The outlet opening 8 of the nozzle device 80 is thus formed by a nozzle opening 82, which is formed by the gap 66 formed between the inner nozzle body 61 and the outer nozzle body 62. Depending on the rotation and stroke of the inner nozzle body 61 by the threaded sleeve 26, a variable nozzle diameter 8 can be achieved, wherein the lateral opening 63 of the inner nozzle body 61 is either closed and sealed or kept free by the inner wall 87 of the outer nozzle body 62, depending on the position. This is controlled by the stroke and additional rotation of the inner nozzle body 61 via the threaded sleeve 26. As the inner nozzle body 61 is raised, the melt 12 exits through the nozzle opening 82 formed by the gap 66 due to the lower resistance, rather than exiting through the narrower nozzle opening 81 of the inner nozzle body 61. Thereafter, the melt 12 fills the recess 65 and flows around the tip of the inner nozzle body 61 and fills the gap 66 completely, so that the melt 12 can be discharged through the nozzle opening 82. In addition, the volume flow or mass flow of the melt 12 can be controlled as a result, depending on the position in which the opening 63 of the inner nozzle body 61 is in relation to the cutout 65 of the outer nozzle body 62.FIGS. 13 to 16 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. 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, wherein the valve 20 is rotatably mounted in the nozzle device 80 and, by means of corresponding rotations of the valve 20 and / or of the threaded sleeve 26, the throughflow opening 22 can be produced between the channels 51, 52 of the adapter device 50, the bores 74, 75 of the threaded sleeve 26 and the nozzle 8, which is not illustrated here. The actuator 6 rotates the threaded sleeve 26 via the driver 73 and the valve 20 directly via the transmission device 85, The change and regulation of the volume flow in the channels 51, 52 takes place only in the region in which the valve 20 is directly controlled.FIG. 13 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 passage 51 is open via the first bore 74 of the threaded sleeve 26 and the position of the valve 20 and the second passage 52 is closed. In the basic position of the threaded sleeve 26, both bores 74, 75 are aligned with the channels 51, 52. Here, only the valve 20, or the switch, is controlled to the corresponding position. In this position, the melt 12 is guided via the channel 51 through the bore 74 of the threaded sleeve 26 through the flow opening 22 of the valve 20 to the die 8, wherein a maximum volume flow of the melt 12 from the first extruder 110 is possible. Here, the valve 20 is turned in such a way that only one channel 51 is opened. For regulating the volume flow, the valve 20 can be rotated in such a way that the flow opening 22 with the channel 51 is moved in each case over the common opening 22, as a result of which the cross section of the opening 22 can become smaller or larger.FIG. 14 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 opened via the second bore 75 of the threaded sleeve 26 and the position of the valve 20. In the basic position of the threaded sleeve 26, both bores 74, 75 are aligned with the channels 51, 52. Here, only the valve 20, or the switch, is controlled to the corresponding position.In this position, the melt 12 is guided via the channel 52 through the bore 75 of the threaded sleeve 26 through the flow opening 22 of the valve 20 to the die 8, wherein a maximum volume flow of the melt 12 from the second extruder 120 is possible. Here, the valve 20 is turned in such a way that only one channel 52 is opened. For regulating the volume flow, the valve 20 can be rotated in such a way that the flow opening 22 with the channel 52 is moved in each case over the common opening 22, as a result of which the cross section of the opening 22 can become smaller or larger.FIG. 15 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, for example, by both extruders 110, 120. In the basic position of the threaded sleeve 26, both bores 74, 75 are aligned with the channels 51, 52. 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. If this position is approached in order to change from one extruder 110, 120 to the other, a pressure equalization takes place when the two extruders 110, 120 are adjusted. In this case, for the purpose of refining an extruder 110, 120, the axial path movement of the print head 100 is stopped and the valve switches into the central position shown here, as a result of which both ducts 51, 52 are connected to one another and both extruder systems can thus be set to a print. Subsequently, printing is continued with the respectively filled extruder 110, 120.FIG. 16 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. The bores 74, 75 of the threaded sleeve 26 are aligned offset with respect to the channels 51, 52.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] DE 10 2016 213439 A1

[0006]

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 at least two extruders (110, 120) for providing the at least one printable material (10) and the nozzle device (80) comprises a valve (20) for regulating a volume flow of the liquid phase (12) from the respective extruders (110, 120) to a nozzle (8) of the nozzle device (80).The print head (100) according to claim 1, characterized in that the print head (100) comprises an adapter device (50) having two channels (51, 52), wherein the nozzle device (80) is connected to the first extruder (110) via the first channel (51) and the nozzle device (80) is connected to the second extruder (120) via the second channel (52).Print head (100) according to one of the preceding claims, characterized in that the nozzle device (80) has two nozzle bodies (61, 62) arranged concentrically one inside the other, wherein the inner nozzle body (61) is arranged within a threaded sleeve (26) in such a way that the inner nozzle body (61) is movable relative to the outer nozzle body (62) by rotation of the threaded sleeve (26).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) and the threaded sleeve (26).Print head (100) according to one of the preceding claims, characterized in that the valve (20) can be actuated by the actuator (6) and the threaded sleeve (26) can be actuated by a driver (73) of the actuator (6).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) of the adapter device (50), bores (74, 75) of the threaded sleeve (26) and the nozzle (8) can be produced by corresponding rotations of the valve (20) and / or of the threaded sleeve (26).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 nozzle device (80) has an outlet opening (8), the cross section of which can be variably adjusted for changing a volume flow of the liquid phase (12).Print head (100) according to one of the preceding claims, characterized in that, in a first operating state of the print head (100), the outlet opening (8) of the nozzle device (80) is formed by a nozzle opening (81) of the inner nozzle body (61).Print head (100) according to one of the preceding claims, characterized in that, in further operating states of the print head (100), the outlet opening (8) of the nozzle device (80) is formed by an opening cross section (82) which results from the relative movement of the inner nozzle body (61) with respect to the outer nozzle body (62).Method (200) for operating a print head (100) according to one of the preceding claims.

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