Printhead for a 3D printer
Patent Information
- Application Number
- EP2023813618
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-19
- Filing Date
- 2023-11-24
- Publication Date
- 2025-10-29
AI Technical Summary
3D printer print heads face challenges in withstanding forces and maintaining a stable printing process due to rigid guidance and tolerance issues, leading to reduced service life and potential jamming.
A print head design featuring a piston with a guide surface that is 1.5 to 1.7 times the maximum axial extent of the opening area, secured against radial rotation, and a polygonal cross-sectional area to ensure optimal guidance and prevent tilting, along with a cutting edge to manage granules, enhancing wear-free operation.
The design optimizes piston guidance, extends service life, and enables continuous operation by preventing jamming and wear, ensuring stable and permanent printing performance.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] Title:
[0003] Print head for a 3D printer
[0004] The present invention relates to a print head for a 3D printer.
[0005] State of the art
[0006] A 3D printer for a material with variable viscosity receives a solid phase of this material as a starting material, creates a liquid phase from it, and selectively deposits this liquid phase at the locations corresponding to the object to be created. Such a 3D printer comprises a print head in which the starting material is prepared for printing. Furthermore, means are provided for generating relative movement between the print head and the work surface on which the object is to be created. This can involve moving either only the print head, only the work surface, or both the print head and the work surface.
[0007] The print head has a first operating state in which liquid material emerges from it, and a second operating state in which no liquid material emerges. The second operating state is assumed, for example, when a different position on the work surface is to be moved to and no material is to be deposited on the way there. The print head can switch between the two operating states, for example, by switching the propulsion of the solid starting material on or off. DE 10 2016 222 306 A1 discloses the plasticization of granules via a piston and a heated section. When the piston presses on the granules, they are compacted and conveyed to a plasticization zone.
[0008] From DE 10 2017 218 707 A1, it is known that a piston of a print head has a guide surface within a bore, which, with an axial extension of the guide surface of the piston, is between 1.1 and 1.3 times the maximum axial extension of an opening area of a feed of raw material. The application points out that a longer guide surface would reduce the service life of the piston, as it would be guided too rigidly, making it impossible to compensate for tolerances.
[0009] The invention is based on the object of providing a print head that can withstand the forces occurring and enables a stable printing process.
[0010] Disclosure of the invention
[0011] Within the scope of the invention, a print head for a 3D printer was developed. This print head comprises an intake zone with a feed for a starting material with variable viscosity, a plasticizing zone with a heater and an outlet opening for the liquid phase of the starting material, and a conveying device for conveying the granulate from the intake zone into the plasticizing zone, wherein the conveying device comprises a piston insertable into the intake zone. Furthermore, the piston has a first piston section facing the plasticizing zone with a guide surface through which the piston is guided in a recess of the print head. The guide surface is longer in its axial extent than a maximum axial extent of an opening area of the feed to the recess.
[0012] In particular, the feed can be provided for a starting material in the form of granules. The starting material can, in particular, be a thermoplastic material. According to the invention, the first piston section and the recess of the pressure head have a polygonal cross-sectional area, and the axial extent of the guide surface of the piston is between 1.5 and 1.7 times the maximum axial extent of the opening area.
[0013] A polygonal cross-sectional area, in particular the resulting angular shape of the cross-sectional area, ensures particularly favorable guidance of the piston in the recess of the print head.
[0014] The size of the feed opening to the recess is relevant for the amount of granulate fed from the feed into the print head recess, or into the print head feed zone. The projection of the piston guide surface from the feed opening advantageously ensures stable guidance of the piston in the recess. Surprisingly, it has been found that with a piston that is secured against radial rotation within the print head recess, a longer guide surface can be selected, which advantageously optimizes piston guidance and increases the piston's service life.
[0015] In a further development, the axial extension of the piston's guide surface is 1.6 times the maximum axial extension of the opening area. An axial extension of the piston's guide surface of 1.6 times the maximum axial extension of the opening area of the feed to the recess has proven particularly advantageous.
[0016] In a further development, the piston is secured against radial rotation within the recess of the print head, wherein the piston is secured against radial rotation by a positive connection of the first piston section to the recess of the print head.
[0017] Such an arrangement of the piston in the print head recess advantageously prevents jamming and tilting of the piston in the print head recess, enabling virtually wear-free operation of the print head. The invention ensures that the piston is always optimally guided in the print head recess and does not deflect, tilt, or twist when it hits the granulate. This enables continuous and long-lasting operation of the print head.
[0018] The positive connection of the first piston section with the recess of the print head ensures that no rotation is transmitted to the first piston section in electrically driven actuators, especially electric motors, which generate a linear movement of the piston through a rotational movement. This advantageously prevents the piston, or the first piston section, from twisting in the recess of the print head.
[0019] The positive connection can be achieved by symmetrical or asymmetrical shapes of the cross-sectional area of the first piston section.
[0020] In a preferred embodiment, the first piston portion and the recess of the print head have a hexagonal cross-sectional area.
[0021] The hexagonal cross-sectional area represents an effective design measure against jamming of the first piston section in the recess, as it advantageously ensures secure guidance of the piston through multiple guide planes. This advantageously minimizes wear and extends the service life of the print head.
[0022] In a further development, the first piston section has a cutting edge for shearing off the starting material at the opening surface of the feed. The cutting edge cuts through granules, in particular granulate grains, that lie within the opening surface of the feed. This advantageously ensures that the first piston section is not blocked by the granules, but rather cuts through them. Potential jamming of the first piston section is thus avoided. The cutting edge can be formed from hardened material or a separate cutting edge, in particular a hard metal cutting edge. Further measures improving the invention are described in more detail below, together with the description of the preferred embodiments of the invention, with reference to the figures.
[0023] Examples of implementation
[0024] They show:
[0025] Fig. 1 shows a print head according to the invention;
[0026] Fig. 2 the print head in a sectional drawing;
[0027] Fig. 3 shows a first embodiment of the print head in a sectional drawing;
[0028] Fig. 4 shows a second embodiment of the print head in a sectional drawing and
[0029] Fig. 5 shows another embodiment of the print head in a sectional drawing.
[0030] Fig. 1 shows a print head 10 according to the invention. The print head 10 for a 3D printer 1 comprises an infeed zone 11 with a feed 12 for a starting material 20, 21 with variable viscosity, a plasticizing zone 14 with a heater 15 and an outlet opening 16 for the liquid phase 22 of the starting material 21, and a conveying device 30 for conveying the starting material 21 from the infeed zone 11 into the plasticizing zone 14, wherein the conveying device 30 comprises a piston 31 insertable into the infeed zone 11. The piston 31 has a first piston section 5 facing the plasticizing zone 14 and having a guide surface 9 through which the piston 31 is guided in a recess 7 of the print head 10. The piston 31 is secured against radial rotation within the recess 7 of the print head 10, in particular by a positive connection of the first piston section 5 with the recess 7 of the print head 10.
[0031] The print head 10 further comprises a housing 19 with the piston 31 guided therein. The piston 31 consists of the first piston section 5 and a second piston section 6. The first piston section 5 is guided in the central recess 7 of the housing 19 in a sealing manner with respect to the starting material 20, 21. It prevents the solid phase 21 of the starting material 20 from escaping and presses this solid phase 21 from the feed zone 11 into the compression zone 11a, where a boundary layer 11b to the liquid phase 22 of the starting material 20 forms. The second piston section 6 lies above the first piston section 5 and is moved in the vertical direction 38, for example, via a spindle of a motor (not shown). Electric motors are preferably used. When the piston 31 moves toward the outlet opening 16 of the print head 10, the liquid phase 22 of the starting material 20 is ejected from the outlet opening 16. Fig.Figure 1 is a snapshot of the state in which exactly this is possible, i.e., the print head 10 is ready to print. In this state, the working volume 17 within the central recess 7 in the housing 19 of the print head 10 is comparatively small.
[0032] In the embodiment shown in Fig. 1, the solid phase 21 of the starting material 20 is fed via a hopper 12 and trickles into the feed zone 11 in the print head 10 as soon as the piston 31 is retracted behind this feed zone 11. The starting material 20 is preferably a granulate. To enable this trickling, only the solid phase 21 of the starting material may be present in the feed zone 11. In particular, this solid phase 21 must not melt and stick together. Therefore, the feed zone 11 is cooled from the outside via coolants 13. The coolants 13 comprise an active cooling system 13a with a cooling medium and a passive cooling system 13b with cooling fins. This helps ensure that the temperature TS in the feed zone remains below the temperature TP at which the solid phase 21 of the starting material 20 plasticizes.Furthermore, an air injection nozzle (not shown) can be arranged on the feed 12, which is preferably arranged near an opening surface 8 of the feed 12 to the recess 7. The air injection nozzle ensures that, by means of air blown in under pressure, the granulate that has not completely trickled into the intake zone 11 is either blown into the intake zone 11 or blown up the hopper 12 from the area of the opening surface 8, so that the piston 31 can easily close the opening surface 8.
[0033] The solid phase 21 of the starting material 20 is heated in the plasticizing zone 14 by means of the heater 15 and is thereby converted into the liquid phase 22, which can exit from the outlet opening 16 when pressure is applied.
[0034] The course of the temperature T along the axis 19b of the housing 19 is sketched on the right in Fig. 1.
[0035] Fig. 2 shows the print head 10 according to the invention in a sectional drawing of a vertical section through the print head 10. The piston 31 has a first piston section 5 facing the plasticizing zone 14 with a guide surface 9 through which the piston 31 is guided in a recess 7 of the print head 10 or the housing 19, wherein the guide surface 9 is longer in its axial extent b than a maximum axial extent k of an opening area 8 of the feed 12 to the recess 7.
[0036] According to the invention, the first piston section 5 and the recess 7 of the print head 10 have a polygonal cross-sectional area and the axial extension b of the guide surface 9 of the piston 31 is between 1.5 and 1.7 times, in particular 1.6 times, the maximum axial extension b of the opening area 8.
[0037] The opening area 8 of the feed 12 to the recess 7 is designed such that the supplied granulate 21 can be optimally fed into the recess or into the feed zone 11.
[0038] Furthermore, the first piston section 5 has a distance d1, d4. The illustrated piston 31 with the correspondingly dimensioned guide surface 9 prevents the piston 31 from tilting in the recess 7 and reduces the penetration of the deformed granulate into the gap between the guide surface 9 and the recess 7.
[0039] The piston 31 further comprises the second piston section 6, the piston diameter d2 of which is smaller than a horizontal distance di of the first piston section 5, which can be a horizontal distance di, a horizontal diagonal d4 or a horizontal diameter di of the first piston section 5.
[0040] Fig. 3 shows a sectional drawing of a horizontal section of the piston 31 of a first embodiment, wherein the piston 31 is secured against radial rotation within the recess 7 of the print head 10. The piston 31 is secured against radial rotation by a positive connection of the first piston section 5 to the recess 7 of the print head 10.
[0041] In this embodiment, the first piston section 5 and the recess 7 of the print head 10 have a polygonal, in particular hexagonal, cross-sectional area.
[0042] The first piston section 5 forms a flat surface 3 on its side facing the opening surface 8, and a maximum horizontal diameter d of the opening surface 8 is smaller than a horizontal distance d4 of the first piston section 5. The horizontal distance d4 is the distance of a diagonal between two opposite edges 18 of the polygonal base surface of the first piston section 5.
[0043] Furthermore, the second piston section 6 is shown, the piston diameter da of which is smaller than a horizontal distance di of the first piston section 5, wherein the horizontal distance di of the first piston section 5 is the distance between the parallel opposite surfaces 2 of the first piston section 5.
[0044] Fig. 4 shows a sectional drawing of a horizontal section of the piston 31 of a second embodiment, wherein the piston 31 is secured against radial rotation within the recess 7 of the print head 10. The piston 31 is secured against radial rotation by a positive connection of the first piston section 5 to the recess 7 of the print head 10.
[0045] In this embodiment, the first piston section 5 and the recess 7 of the print head 10 have a polygonal, in particular hexagonal, cross-sectional area.
[0046] The first piston section 5 has mutually parallel flat surfaces 2. Furthermore, an edge 18 of the piston section 5 is aligned centrally with the opening surface 8, and the maximum horizontal diameter da of the opening surface 8 is smaller than the horizontal distance di between the parallel flat surfaces 2 of the first piston section 5.
[0047] Fig. 5 shows a further embodiment of the print head 10 in a sectional drawing of a vertical section through the print head 10, wherein the first piston section 5 has a cutting edge 4 for shearing off the starting material 21 in granular form at the opening surface 8 of the feed 12. The cutting edge 4 is formed from a hardened material and, in the form shown here, has a separate cutting tool, in particular a reversible plate.
[0048] Here too, the piston 31 has the first piston section 5 facing the plasticizing zone 14 with the guide surface 9, through which the piston 31 is guided in the recess 7 of the print head 10 or the housing 19.
[0049] The opening area 8 of the feed 12 to the recess 7 is designed such that the supplied granulate 21 can be optimally fed into the recess or into the feed zone 11.
[0050] Furthermore, the first piston section 5 has the distance di , d4.
[0051] The illustrated piston 31 with the correspondingly dimensioned guide surface 9 prevents the piston 31 from tilting in the recess 7 and reduces the penetration of the deformed granulate into the gap between the guide surface 9 and the recess 7. The piston 31 further comprises the second piston section 6, whose piston diameter d2 is smaller than the distance di, d4 of the first piston section 5. The print head 10 can be integrated into any 3D printer.
Claims
Claims 1. Print head (10) for a 3D printer (1), comprising an intake zone (11) with a feed (12) for a starting material (21) with a variable viscosity, a plasticizing zone (14) with a heater (15) and an outlet opening (16) for the liquid phase (22) of the starting material (21), and a conveying device (30) for conveying the starting material (21) from the intake zone (11) into the plasticizing zone (14), wherein the conveying device (30) comprises a piston (31) insertable into the intake zone (11), wherein the piston (31) has a first piston section (5) facing the plasticizing zone (14) with a guide surface (9) through which the piston (31) is guided in a recess (7) of the print head (10), wherein the guide surface (9) in its axial extent (b) is longer than a maximum axial extension (k) of an opening area (8) of the feed (12) to the recess (7), characterized in thatthat the first piston section (5) and the recess (7) of the pressure head (10) have a polygonal cross-sectional area and the axial extension (b) of the guide surface (9) of the piston (31) is between 1.5 and 1.7 times the maximum axial extension (b) of the opening surface (8).
2. Print head (10) according to claim 1, characterized in that the axial extension (b) of the guide surface (9) of the piston (31) is 1.6 times the maximum axial extension (b) of the opening surface (8).
3. Print head (10) according to one of the preceding claims, characterized in that the piston (31) is secured against radial rotation within the recess (7) of the print head (10).
4. Print head (10) according to claim 3, characterized in that the piston (31) is secured against radial rotation by a positive connection of the first piston section (5) with the recess (7) of the print head (10).
5. Print head (10) according to one of the preceding claims, characterized in that the first piston section (5) and the recess (7) of the print head (10) have a hexagonal cross-sectional area.
6. Print head (10) according to one of the preceding claims, characterized in that the first piston section (5) has a cutting edge (4) for shearing off the starting material (21) at the opening surface (8) of the feed (12).