Extruder for a 3D printer with a variable material throughput

Abstract

Extruder (1) for a 3D printer, comprising at least one outer nozzle (2) and a conveying worm (3) for feeding liquid and/or plasticized starting material (4) into the interior chamber (21) of the outer nozzle (2), wherein an inner nozzle (5) is arranged in the interior chamber (21) of the outer nozzle (2), wherein the interior chamber (51) of the inner nozzle (5) is connected to the interior chamber (21) of the outer nozzle (2) via at least one duct (52, 52a, 52b) which is continuous for the starting material (4), and wherein the inner nozzle (5) is mounted such that it can be moved linearly along the longitudinal axis (2a) of the outer nozzle (2). A 3D printer (100) having the extruder (1) and means (8) for generating a relative movement between the extruder (1) and a construction surface (101), on which the object (102) to be manufactured is produced.

Claims

1. An extruder (1) for a 3D printer, the extruder comprising at least one outer nozzle (2) and a conveying screw (3) for feeding liquid and/or plasticized starting material (4) into an interior space (21) of the outer nozzle (2), characterized in that an inner nozzle (5) is arranged in the interior space (21) of the outer nozzle (2), wherein the inner nozzle (5) is mounted rotatably on the conveying screw (3) via a bearing element (6), wherein an interior space (51) of the inner nozzle (5) is connected to the interior space (21) of the outer nozzle (2) via at least one duct (52, 52a, 52b), wherein the at least one duct (52, 52a, 52b) allows the starting material (4) to pass from the interior space (21) of the outer nozzle (2) to the interior space (51) of the inner nozzle (5), wherein the inner nozzle (5) is mounted in a manner linearly movable along a longitudinal axis (2a) of the outer nozzle (2), wherein the outer nozzle has opposite front and rear ends spaced apart along the longitudinal axis, wherein the outer nozzle (2) has an outlet opening (23) at the front end and an inner surface (22) defining the interior space (21) of the outer nozzle (2), wherein a portion of the inner surface (22) of the outer nozzle (2) faces toward the rear end, wherein the inner nozzle (5) is movable along the longitudinal axis (2a) toward and away from a position in which an outer surface (53) of the inner nozzle (5) is brought into a sealing engagement (24a, 24b) with the portion of the inner surface (22) of the outer nozzle (2), and wherein the sealing engagement (24a, 24b) is configured to prevent direct passage of the starting material (4) from the interior space (21) of the outer nozzle (2) to the outlet opening (23) of the outer nozzle (2) and to allow indirect passage of the starting material (4) from the interior space (21) of the outer nozzle (2) to the outlet opening (23) of the outer nozzle (2) via the at least one duct (52, 52a, 52b), the interior space (51) of the inner nozzle (5) and an outlet opening (54) of the inner nozzle (5).

2. The extruder (1) as claimed in claim 1, characterized in that, with movement of the inner nozzle (5) along the longitudinal axis (2a) of the outer nozzle (2) in a direction toward the outlet opening (23) of the outer nozzle (2), the sealing engagement is firstly linear (24a) and, with further advancement of the inner nozzle (5), widens into an areal seal (24b).

3. The extruder (1) as claimed in claim 2, characterized in that, with the further advancement of the inner nozzle (5), the sealing engagement (24a) widens in the direction of said advancement.

4. The extruder (1) as claimed in claim 1, characterized in that a portion of the outer surface (53) of the inner nozzle (5) tapers toward the outlet opening (54) of the inner nozzle (5) at an angle , which differs from an angle at which the portion of the inner surface (22) of the outer nozzle (2) tapers toward the outlet opening (23) of the outer nozzle (2).

5. The extruder (1) as claimed in claim 1, characterized in that the conveying screw (3) is guided in a cylinder (7) which, at a first end (71), has a feeder (72) for the starting material (4) and, at a second end (73), opens out into the outer nozzle (2).

6. The extruder (1) as claimed in claim 5, characterized in that the cylinder (7) has at least one heater (74, 75, 76) for heating the starting material (4).

7. The extruder (1) as claimed in claim 5, characterized in that an outer diameter and/or a pitch of the conveying screw (3) vary/varies along a longitudinal axis (7a) of the cylinder (7).

8. A 3D printer (100) comprising at least one extruder (1) as claimed in claim 1, and means (8) for generating a relative movement between the extruder (1) and a construction surface (101) on which an object (102) to be produced is formed.

9. The 3D printer (100) as claimed in claim 8, characterized in that the means (8) is configured for displacing the construction surface (101) in at least three spatial directions.

10. The 3D printer (100) as claimed in claim 8, characterized in that the means (8) comprise a robot (81) for moving the extruder (1) in at least four axes.

11. The 3D printer (100) as claimed in claim 8, characterized in that, with movement of the inner nozzle (5) along the longitudinal axis (2a) of the outer nozzle (2) in a direction toward the outlet opening (23) of the outer nozzle (2), the sealing engagement is firstly linear (24a) and, with further advancement of the inner nozzle (5), widens into an areal seal (24b).

12. The 3D printer (100) as claimed in claim 11, characterized in that, with the further advancement of the inner nozzle (5), the sealing engagement (24a) widens in the direction of said advancement.

13. The 3D printer (100) as claimed in claim 8, characterized in that a portion of the outer surface (53) of the inner nozzle (5) tapers toward the outlet opening (54) of the inner nozzle (5) at an angle , which differs from an angle at which the portion of the inner surface (22) of the outer nozzle (2) tapers toward the outlet opening (23) of the outer nozzle (2).

14. The 3D printer (100) as claimed in claim 8, characterized in that the conveying screw (3) is guided in a cylinder (7) which, at a first end (71), has a feeder (72) for the starting material (4) and, at a second end (73), opens out into the outer nozzle (2).

15. The 3D printer (100) as claimed in claim 14, characterized in that the cylinder (7) has at least one heater (74, 75, 76) for heating the starting material (4).

16. The 3D printer (100) as claimed in claim 14, characterized in that an outer diameter and/or a pitch of the conveying screw (3) vary/varies along a longitudinal axis (7a) of the cylinder (7).

17. The extruder (1) as claimed in claim 1, wherein the outlet opening (54) of the inner nozzle (5) is in the interior space (21) of the outer nozzle (2) when the inner nozzle is brought into contact with the portion of the inner surface (22) of the outer nozzle (2).

18. The extruder (1) as claimed in claim 4, wherein the angle is less than the angle .

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further measures which improve the invention will be presented more specifically below together with the description of the preferred exemplary embodiments of the invention on the basis of figures.

Exemplary Embodiments

(2) In the figures:

(3) FIG. 1 shows a detail illustration of the inner nozzle within the outer nozzle;

(4) FIG. 2 shows an exemplary embodiment of the complete extruder;

(5) FIG. 3 shows an exemplary embodiment of a 3D printer with the extruder according to the invention.

DETAILED DESCRIPTION

(6) FIG. 1 shows one part of the extruder 1 in a sectional drawing. The extruder 1 comprises an outer nozzle 2 and an inner nozzle 5. The inner nozzle 5 is situated in the interior space 21 of the outer nozzle 2. The inner nozzle 5 is mounted rotatably on the conveying screw 3 via a bearing 6, said conveying screw being guided in a cylinder 7 and, when rotating about its own axis, which is identical to the longitudinal axis 7a of the cylinder 7, conveying liquid starting material 4 into the interior space 21 of the outer nozzle 2. The left-hand end 73 of the cylinder 7 opens out into the outer nozzle 2.

(7) If the conveying screw 3 is moved along the longitudinal axis 7a of the cylinder 7, which is identical to the longitudinal axis 2a of the outer nozzle 2, then the inner nozzle 5 is moved along therewith. In the situation shown in FIG. 1, the inner nozzle 5 is situated at its left-hand stop. When the inner nozzle 5 was moved to the left, firstly the edge 24a on the outer periphery 53 of the inner nozzle 5 made contact with the inner periphery 22 of the outer nozzle 2 and brought about a first, linear seal between the outer periphery 53 of the inner nozzle 5 and the inner periphery 22 of the outer nozzle 2. Further movement of the inner nozzle 5 to the left resulted in said linear seal 24a being expanded into an areal seal 24b in the direction toward the outlet opening 54. This was effected by virtue of the fact that the outer periphery 53 of the inner nozzle 5 tapers at an angle which is more acute than the angle at which the inner periphery 22 of the outer nozzle 2 tapers.

(8) The areal seal 24b prevents the direct passage of starting material 4 from the interior space 21 of the outer nozzle 2 to the outlet opening 23 of the outer nozzle 2. The passage through the ducts 52a and 52b into the interior space 51 of the inner nozzle 5 remains as the only way out for the liquid starting material 4 subjected to pressure by the conveying screw 3. The starting material 4 finally emerges from the inner nozzle 5, and passes to the object 102 to be produced, through the outlet opening 54.

(9) The position, shown in FIG. 1, of the inner nozzle 5, in which position said inner nozzle bears fixedly, due to friction, against the inner periphery 22 of the outer nozzle 2, is the extrusion position, in which only the small outlet opening 54 of the inner nozzle 5 is relevant. Said outlet opening 54 may have for example a diameter of between 0.2 mm and 0.4 mm, preferably 0.3 mm. In said position, the size of the outlet opening 23 of the outer nozzle 2 is unimportant for the application of the starting material 4 to the object 102 to be produced.

(10) If the inner nozzle 5 is moved together with the conveying screw 3 to the right, then the seal 24a, 24b between the outer periphery 53 of the inner nozzle 5 and the inner periphery 22 of the outer nozzle 2 is broken. In the interior space 21 of the outer nozzle 2, the starting material 4 can then pass directly to the outlet opening 23 of the outer nozzle 2, without passing through the ducts 52a, 52b and the interior space 51 of the inner nozzle 5 beforehand. The latter path is as before open to the starting material 4. However, since the direct path to the outlet opening 23 of the outer nozzle 2 has a significantly larger cross section, most of the starting material 4 will take this path. Accordingly, the significantly larger outlet opening 23 is relevant for the application of material to the object 102 to be produced. Said position is the middle position of the inner nozzle 5.

(11) If the inner nozzle 5 is moved even further to the right and, at the same time, the rotation of the conveying screw 3 stopped, then no more starting material 4 is pressed through the outlet openings 23 and 54. Instead, the starting material 4 which is still present in the region of the outlet opening 23 is drawn back into the outer nozzle 2. This is the retracted position of the inner nozzle 5. In said position, the extruder can be displaced for example to another location of an extended object 102 to be produced in order, there, to apply further starting material 4.

(12) It should be mentioned in this context that a mere partial blockage of the central region of the outlet opening 23 of the outer nozzle 2 with a plug which is able to be displaced linearly along the axis 2a does not have the effect that the extruder 1 adds relatively fine structures from the starting material 4 to the object 102 to be produced. Although such a blockage would narrow the passage through the outlet opening 23 to an annular gap, beyond said annular gap, the starting material 4 coming from different angular positions of the annular gap would, on account of its viscosity, again combine to form a mass which again has the size of the outlet opening 23.

(13) FIG. 2 shows a partially sectional total view of the extruder 1, in which the details, shown in FIG. 1, of the nozzles 2 and 5 are suppressed. The cylinder 7, whose second end 73 opens out into the outer nozzle 2, is supplied with the starting material 4 in granular form at its first end 71 via a hopper 72. Along the longitudinal axis 7a of the cylinder 7, both the outer diameter and the pitch of the conveying screw 3 vary. This, in combination with the three thermostatically regulated heating elements 74, 75 and 76, has the effect that the starting material 4 is gradually plasticized before it enters the outer nozzle 2.

(14) The conveying screw 3 is driven via a servo motor 9. The servo motor 9 not only sets the conveying screw 3 in rotation, but also drives its linear movement along the longitudinal axis 7a of the cylinder 7. Accordingly, it is also possible by way of this servo motor 9 to set whether the starting material is to emerge from the large outlet opening 23 of the outer nozzle 2 or from the small outlet opening 54 of the inner nozzle 5.

(15) FIG. 3 illustrates the integration of the extruder 1 according to the invention into a 3D printer 100 for the production of spatially extended objects 102 on a construction surface 101. The relative movement between the extruder 1 and the object 102 to be produced is provided by an industrial robot 81 which is movable about six axes A to F in the directions illustrated in each case by arrows.

(16) In one embodiment, the 3D printer 100 has the extruder 1, wherein, in addition to the extruder itself, means 8 for generating a relative movement between the extruder 1 and a construction surface 101 on which the object 102 to be produced is formed are also provided.

(17) In this way, the extruder 1 not only acquires a large radius of action, but is in particular also able to add to the object 102 to be produced starting material 4 from any desired angles. If in the example shown in FIG. 3, additional material is to be added to the object 102 for example at the point 102a depicted by way of example, then the application from the angle shown in FIG. 3 is more advantageous than the application vertically from above, since the point 102a is situated on an overhang.

(18) In this context, the advancement of the starting material 4 via a conveying screw 3 is in turn more advantageous than the advancement as a solid filament practiced in the case of most conventional 3D printers. In particular, the pressure build-up in the extruder 1 is more independent of location, and a fill of granules as starting material 4 is able to be handled more easily than a filament to be unrolled.