Printing head for 3D printer

Abstract

The invention relates to a print head (10) for a 3D printer (1), comprising a feed zone (11) having a feed (12) for a starting material (21), the viscosity of which can be varied, a plasticizing zone (14) having a heating device (15) and an outlet (16) for a liquid phase (22) of the starting material (21), and a conveying device (30) for conveying the starting material (21) from the feed zone (11) to the plasticizing zone (14), the conveying device (30) comprises a piston (31) which can be guided into the feed zone (11), the piston (31) having a first piston section (5) which faces the plasticizing zone (14) and which has a guide surface (9) by means of which the piston (31) is guided in the recess (7) of the printing head (10), the piston (31) being secured against radial torsion in the recess (7) of the printing head (10).

Description

Technical Field

[0001] The present invention relates to a print head for a 3D printer. Background Art

[0002] A 3D printer for materials with variable viscosity uses a solid phase of the material as a starting material, creates a liquid phase from it, and selectively applies this liquid phase to the areas of the object to be created. This 3D printer includes a print head, in which the starting material is prepared for printing. Furthermore, a device is provided for generating relative movement between the print head and the work surface on which the object is to be formed. This can involve moving only the print head or the work surface, but it is also possible to move both the print head and the work surface.

[0003] The print head has a first operating state, in which liquid material is discharged from the print head, and a second operating state, in which no liquid material is discharged from the print head. For example, the print head is in the second operating state when approaching another location on the work surface without depositing material there en route. Switching between these two operating states of the print head can be accomplished, for example, by switching the feed of solid starting material on or off.

[0004] It is known from DE 10 2016 222 306 A1 to plasticize particles by means of a piston and a heated section. When the piston presses against the particles, the particles are compressed and conveyed to the plasticizing zone. Summary of the Invention

[0005] The object of the present invention is to provide a print head which absorbs the forces that occur and enables a stable printing process.

[0006] Within the scope of the present invention, a print head for a 3D printer has been developed. The print head comprises a feed zone with a feed for supplying a starting material whose viscosity can be varied, a plasticizing zone with a heating device and an outlet for the liquid phase of the starting material, and a conveying device for conveying granules from the feed zone into the plasticizing zone. The conveying device comprises a piston that can be introduced into the feed zone. Furthermore, the piston has a first piston section facing the plasticizing zone and having a guide surface by which the piston is guided in a groove of the print head. In particular, a feed for starting material in the form of granules can be provided. The starting material can be, in particular, a thermoplastic material.

[0007] According to the invention, the piston is secured against radial rotation in a recess in the print head.

[0008] In a preferred embodiment, the piston is secured against radial rotation by a positive connection of the first piston section to the recess of the print head.

[0009] This arrangement of the piston in the printhead's slot advantageously prevents the piston from getting stuck or tilting in the printhead's slot, thereby enabling virtually wear-free operation of the printhead. The present invention ensures that the piston is always optimally guided in the printhead's slot and does not deflect, tilt, or twist when engaging particles. This ensures continuous and long-lasting operation of the printhead.

[0010] The positive connection between the first piston section and the recess of the print head ensures that, in an electric actuator, in particular an electric motor, which generates a linear movement of the piston via a rotational movement, no rotation is transmitted to the first piston section. This advantageously prevents the piston or the first piston section from twisting in the recess of the print head.

[0011] The form-locking connection can be achieved by a symmetrical or asymmetrical shape of the cross section of the first piston section.

[0012] In a first embodiment, the first piston section and the notch of the print head have polygonal, particularly hexagonal, cross-sections. This polygonal, particularly hexagonal, cross-section effectively prevents the first piston section from tilting in the notch, as the multiple guide surfaces advantageously enable reliable guidance of the piston. This advantageously minimizes wear and extends the service life of the print head.

[0013] In another embodiment, the first piston section and the notch of the print head have a partially circular, particularly semicircular, cross section. In another embodiment, the first piston section and the notch of the print head have a circular segment-shaped cross section. The partially circular, particularly semicircular, or circular segment-shaped cross section each effectively prevents the first piston section from tilting in the notch, as the at least one guide surface advantageously enables reliable guidance of the piston. This advantageously minimizes wear and extends the service life of the print head.

[0014] In a further development, the axial extension of the guide surface of the piston is 1.5 to 1.7 times the maximum axial extension of the feed section to the opening surface of the slot.

[0015] The size of the opening of the feed section to the slot is related to the amount of particles supplied from the feed section into the slot of the print head or into the feed area of ​​the print head.

[0016] The projection of the guide surface of the piston relative to the opening surface of the feed section advantageously results in a stable guidance of the piston in the slot.

[0017] It has surprisingly been found that the use of a piston secured against radial rotation in a recess in the print head allows the selection of a longer guide surface, thereby advantageously optimizing the piston guidance and increasing the service life of the piston.

[0018] It has proven to be particularly advantageous if the axial extension of the guide surface of the piston is 1.6 times the maximum axial extension of the feed section to the opening surface of the slot.

[0019] In one embodiment, the first piston section has a cutting edge on the opening surface of the feed section for shearing the starting material. The cutting edge shears off particles, particularly granular bodies, located within the opening surface of the feed section. This advantageously prevents the first piston section from becoming clogged with particles, but rather shears them off. This prevents the first piston section from tilting. The cutting edge can be formed from a hardened material or a separate cutting edge, particularly a carbide cutting edge. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further measures for improving the invention are presented in more detail below together with the description of preferred exemplary embodiments of the invention based on the drawings.

[0021] The accompanying drawings show:

[0022] Figure 1 : A print head according to the present invention;

[0023] Figure 2 : Cross-sectional view of the print head;

[0024] Figure 3 : A cross-sectional view of a first embodiment of a print head;

[0025] Figure 4 : A cross-sectional view of a second embodiment of a print head;

[0026] Figure 5 : A cross-sectional view of another embodiment of a print head. DETAILED DESCRIPTION

[0027] Figure 1 A print head 10 according to the present invention is shown. The print head 10 for a 3D printer 1 comprises a feed zone 11 having a feed 12 for starting materials 20, 21 whose viscosity can be varied; a plasticizing zone 14 having a heating device 15 and an outlet 16 for a liquid phase 22 of the starting material 21; and a conveying device 30 for conveying the starting material 21 from the feed zone 11 into the plasticizing zone 14. The conveying device 30 comprises a piston 31 that can be introduced into the feed zone 11. The piston 31 has a first piston section 5 facing the plasticizing zone 14 and a guide surface 9, via which the piston 31 is guided in the recess 7 of the print head 10. According to the present invention, the piston 31 is secured against radial rotation in the recess 7 of the print head 10, in particular by a positive-locking connection between the first piston section 5 and the recess 7 of the print head 10.

[0028] The print head 10 also includes a housing 19 in which a piston 31 is guided. The piston 31 consists of a first piston section 5 and a second piston section 6. The first piston section 5 is guided in a central recess 7 of the housing 19, sealingly relative to the starting materials 20, 21. This prevents the solid phase 21 of the starting material 20 from escaping and presses it from the feed zone 11 into the compression zone 11a, where it forms a boundary layer 11b with the liquid phase 22 of the starting material 20. The second piston section 6 is located above the first piston section 5 and is moved in a vertical direction 38, for example, by the spindle of a motor (not shown). An electric motor is preferably used. As the piston 31 moves toward the outlet 16 of the print head 10, the liquid phase 22 of the starting material 20 is discharged from the outlet 16. Figure 1 It is just possible to realize the instantaneous shooting when the print head 10 is in the printable state. In this state, the working volume 17 in the central slot 7 in the housing 19 of the print head 10 is relatively small.

[0029] exist Figure 1 In the embodiment shown, the solid phase 21 of the initial material 20 is supplied via the hopper 12 and, once the piston 31 is pulled back behind the feed zone 11, the solid phase 21 falls into the feed zone 11 of the print head 10. The initial material 20 is preferably granules. In order to allow the granules to fall, only the solid phase 21 of the initial material is allowed to be present in the feed zone 11. In particular, this solid phase 21 must not melt or stick. Therefore, the feed zone 11 is cooled from the outside by a cooling device 13. The cooling device 13 includes active cooling 13a with a cooling medium and passive cooling 13b with cooling ribs. This helps to keep the temperature TS in the feed zone below the temperature TP at which the solid phase 21 of the initial material 20 is plasticized.

[0030] Furthermore, an air blowing nozzle (not shown) may be arranged at the feed section 12, preferably in the vicinity of the opening surface 8 from the feed section 12 to the slot 7. The air blowing nozzle causes the particles that have not completely fallen into the feed area 11 to be blown into the feed area 11 or blown from the area of ​​the opening surface 8 toward the hopper 12 by the air blown in under pressure, so that the piston 31 can close the opening surface 8 without any problems.

[0031] The solid phase 21 of the starting material 20 is heated in the plasticizing zone 14 by means of the heating device 15 and thereby converted into a liquid phase 22 which can be discharged from the outlet 16 when subjected to pressure.

[0032] exist Figure 1 The right side of FIG. 1 schematically shows the temperature T along the axis 19 b of the housing 19 .

[0033] Figure 2The print head 10 according to the invention is shown in a sectional view in a vertical section through the print head 10. The piston 31 has a first piston section 5 facing the plasticizing zone 14 and having a guide surface 9, via which the piston 31 is guided in the recess 7 of the print head 10 or the housing 19.

[0034] The axial extension l2 of the guide surface 9 is greater than the maximum axial extension l1 of the feed section 12 to the opening surface 8 of the slot 7. The opening surface 8 from the feed section 12 to the slot 7 is designed so that the supplied particles 21 can be optimally supplied into the slot or feed area 11. The axial extension l2 of the guide surface 9 of the piston 31 is preferably 1.5 to 1.7 times, in particular 1.6 times, the maximum axial extension l1 of the opening surface 8.

[0035] Furthermore, the first piston section 5 has distances d1, d4. The piston 31 shown with correspondingly dimensioned guide surfaces 9 prevents tilting of the piston 31 in the notch 7 and reduces the penetration of deformed particles into the gap between the guide surface 9 and the notch 7.

[0036] The piston 31 further comprises a second piston section 6 , whose piston diameter d2 is smaller than the horizontal distance d1 of the first piston section 5 , wherein the horizontal distance may be the horizontal distance d1 , the horizontal diagonal d4 or the horizontal diameter d1 of the first piston section 5 .

[0037] Figure 3 The sectional view shows a horizontal section through the piston 31 of the first exemplary embodiment, wherein the piston 31 is secured against radial rotation in the recess 7 of the print head 10. The piston 31 is secured against radial rotation by a positive connection between the first piston section 5 and the recess 7 of the print head 10.

[0038] In this embodiment, the first piston section 5 and the recess 7 of the print head 10 have a polygonal, in particular hexagonal, cross section.

[0039] The first piston section 5 forms a flat surface 3 on its side facing the opening surface 8, and the maximum horizontal diameter d3 of the opening surface 8 is smaller than the horizontal distance d4 of the first piston section 5. The horizontal distance d4 is the diagonal distance between two opposite sides 18 of the polygonal base of the first piston section 5.

[0040] Furthermore, a second piston section 6 is shown, whose piston diameter d2 is smaller than the horizontal distance d1 of the first piston section 5 , wherein the horizontal distance d1 of the first piston section 5 is the distance between parallel opposite surfaces 2 of the first piston section 5 .

[0041] Figure 4A sectional view shows a horizontal section through a piston 31 of a second exemplary embodiment, wherein the piston 31 is secured against radial rotation in the recess 7 of the print head 10. The piston 31 is secured against radial rotation by a positive-locking connection between the first piston section 5 and the recess 7 of the print head 10. In this embodiment, the first piston section 5 and the recess 7 of the print head 10 have a polygonal, in particular hexagonal, cross-section.

[0042] The first piston section 5 has parallel flat surfaces 2 . Furthermore, the edge 18 of the piston section 5 is centered relative to the opening surface 8 , and the maximum horizontal diameter d3 of the opening surface 8 is smaller than the horizontal distance d1 between the parallel flat surfaces 2 of the first piston section 5 .

[0043] In a third exemplary embodiment (not shown), the first piston section 5 and the recess 7 of the print head 10 have a partially circular, in particular semicircular, cross section.

[0044] In a fourth exemplary embodiment (not shown), the first piston section 5 and the recess 7 of the print head 10 have a circular segment-shaped cross section. In this case, the circular segment describes a partial surface of a circular surface that is bounded by a circular arc and a chord.

[0045] Figure 5 A sectional view of another embodiment of a print head 10 is shown in a vertical section through the print head 10, wherein the first piston section 5 has a cutting edge 4 on the opening face 8 of the feed 12 for shearing off the starting material 21 in granular form. The cutting edge 4 is made of hardened material and, in the embodiment shown here, has a separate cutting tool, in particular a diverter plate.

[0046] Here too, the piston 31 has a first piston section 5 facing the plasticizing zone 14 and having a guide surface 9 , via which the piston 31 is guided in the recess 7 of the print head 10 or the housing 19 .

[0047] The opening surface 8 of the feed 12 to the slot 7 is designed such that the supplied particles 21 can be optimally fed into the slot or into the feed zone 11 .

[0048] Furthermore, the first piston section 5 has distances d1, d4. The piston 31 shown with a correspondingly dimensioned guide surface 9 prevents tilting of the piston 31 in the notch 7 and reduces the penetration of deformed particles into the gap between the guide surface 9 and the notch 7.

[0049] The piston 31 further comprises a second piston section 6 , the piston diameter d2 of which is smaller than the distances d1 , d4 of the first piston section 5 .

[0050] The print head 10 can be integrated into any 3D printer.

Claims

1. A print head (10) for a 3D printer (1), comprising: a feed zone (11) having a feed (12) for a starting material (21) whose viscosity can be varied, a plasticizing zone (14) having a heating device (15) and an outlet (16) for the liquid phase (22) of the starting material (21), and A conveying device (30) for conveying the starting material (21) from the feed zone (11) into the plasticizing zone (14), wherein the conveying device (30) comprises a piston (31) which can be introduced into the feed zone (11), wherein the piston (31) has a first piston section (5) facing the plasticizing zone (14), wherein the first piston section has a guide surface (9) by which the piston (31) is guided in the groove (7) of the print head (10), It is characterized by: The piston (31) is secured against radial twisting in a slot (7) of the print head (10).

2. The print head (10) according to claim 1, It is characterized by: The piston (31) is secured against radial rotation by a positive connection between the first piston section (5) and the recess (7) of the print head (10).

3. A print head (10) according to any one of the preceding claims, It is characterized by: The first piston section (5) and the recess (7) of the print head (10) have a polygonal, in particular hexagonal, cross section.

4. The print head (10) according to claim 1 or 2, It is characterized by: The first piston section (5) and the recess (7) of the print head (10) have a partially circular, in particular a semicircular, cross section.

5. The print head (10) according to claim 1 or 2, It is characterized by: The first piston section (5) and the slot (7) of the print head (10) have a circular segment-shaped cross section.

6. The print head (10) according to any one of the preceding claims, It is characterized by: The axial extension (l2) of the guide surface (9) of the piston (31) is 1.5 to 1.7 times the maximum axial extension (l1) from the feed portion (12) to the opening surface (8) of the slot (7).

7. A print head (10) according to any one of the preceding claims, It is characterized by: The first piston section (5) has a cutting edge (4) for shearing the starting material (21) at an opening surface (8) of the feed portion (12).

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