Material drying for additive manufacturing

Abstract

The invention relates to a method for the air-drying of solid, plasticisable material for use in a device for producing a three-dimensional object by means of additive manufacturing with material preparation and to a corresponding device for producing the three-dimensional object from solid, plasticisable material with at least one manufacturing unit. A heated gaseous substance is introduced via a cavity (10) of a double-wall material supply connector (5), which is arranged between a material store (2) for the solid material and a material intake zone (7) of a plasticising unit (1) for plasticising the solid material. The heated gaseous substance then exits the cavity (10) of the double wall (8, 9) of the material supply connector (5) close to the material intake zone (7) and rises through the material supply connector (5) to the material store, said gaseous substance flowing around the solid material.

Description

[0001] Material drying for additive manufacturing

[0002] Description

[0003] Reference to related applications

[0004] The present application relates to and claims the priority of German patent application 10 2023 135 002.1 , filed on December 13, 2023, the disclosure content of which is hereby expressly incorporated in its entirety into the subject matter of the present application.

[0005] Field of the invention

[0006] The present invention relates to a method with the features of claim 1 for air drying material for the additive manufacturing of three-dimensional objects, including a material preparation step. Furthermore, the invention relates to an apparatus for producing a three-dimensional object from solid, plasticizable material, including an air drying step, with the features of claim 8.

[0007] State of the art

[0008] In such a process, plastic granulate is fed from a material storage through a preferably laterally and / or vertically arranged material feed nozzle into a material feed zone of a plasticizing unit.

[0009] To prevent hydrolytic material damage during melting and air pockets in the discharged material, and to ensure reproducible component quality, the state of the art utilises dried and heated air to flush the plastic granulate in the material reservoir. However, material located in the material feed nozzle can absorb moisture from the environment during downtimes, as this area is not flushed by air. Depending on the material, this material is unusable for the process and must be removed from the system – either through multiple rinsing processes or by vacuuming out the nozzle due to poor accessibility. In both cases, the material can no longer be used for production. This is particularly important when the material hopper is small, as generally little material is needed for the respective application.This can quickly become very costly, especially when it comes to special materials, such as those suitable for medical applications.

[0010] A device for feeding a processing machine is known from WO 95 / 11121A1. It comprises a drying container from which the processing machine can be fed via a conveying line, a compressed air generator that generates the conveying medium required for conveying the material, a duct that feeds compressed air into the conveying line, and a return line that is connected to the drying container and can be connected to the intake port of the compressed air generator in a recirculation position. A transfer element that can be moved into at least two positions and has at least two connections is arranged on the intake port of the compressed air generator inside the device. The return line is connected to one connection, and ambient air for fresh air operation can be drawn in via the second connection.Inside the housing, space is provided at the intake port for the installation of an air dryer, which provides both the air volume required to dry the processing material and the air volume required to convey the dried processing material. This device is designed for an injection molding machine and is separate from the machine. It is connected to the injection molding machine via a hose and is used to dry the material. Material may remain in the hose after the end of an injection molding process, which absorbs moisture again between two injection molding processes.

[0011] DE 2020 17 106 213 U1 discloses a granulate dryer with a granulate container, which is made in particular of glass. It has a lower opening as a drying air inlet and granulate outlet, and an upper opening as a drying air outlet. A constant-flow stabilizer in the granulate container rests at least vertically, i.e., in the direction of gravity, on the granulate container or its lid, and in particular also horizontally on the inner surfaces of the granulate container. The granulate container is circumferentially surrounded by an outer container, the outer base of which has a vertical through-channel and a transverse opening from the vertical through-channel to the outer periphery of the outer container, wherein the lower opening of the granulate container ends in the vertical through-channel of the outer base.Through the transverse opening outside the outer floor, drying air flows downwards into the duct to the lower opening of the granulate container, and from there upwards within the container. The incoming drying air flows only through the lower opening of the granulate container.

[0012] Description of the invention

[0013] The invention is therefore based on the object of providing a method and a device by which undesirable material impairment up to the material feed zone is avoided as far as possible.

[0014] This object is achieved by a method according to the features of patent claim 1. This method is for air-drying solid, plasticizable material for use in a device for producing a three-dimensional object from solid and plasticizable material by means of additive manufacturing with material preparation. The device comprises at least one additive manufacturing unit with:

[0015] - at least one plasticising unit, designed to plasticise the solid material for discharge by a discharge unit,

[0016] - at least one material storage unit upstream of the plasticising unit,

[0017] - a material feed nozzle connected to the material reservoir, the first end of which is operatively connected to the material reservoir and the second end of which is operatively connected to a material feed zone of the plasticising unit,

[0018] - whereby the material storage and the material feed nozzle are filled with the solid material.

[0019] The material feed nozzle has an inner and outer wall with a cavity in between. According to the method, a source of a heated gaseous substance is connected to the cavity. The heated gaseous substance is introduced into the cavity of the material feed nozzle at a location remote from the material feed zone, with the heated gaseous substance being transported to the material feed zone. The heated gaseous substance transported to the material feed zone is then guided from the material feed zone through the material feed nozzle to the material reservoir, with the heated gaseous substance flowing around the solid material. This advantageously ensures that the material, which is usually in the form of granules and is located in the material feed nozzle, is dried and / or prepared for processing.This prevents hydrolytic and / or oxidative material damage during melting, as well as air and / or moisture inclusions in the discharged material, ensuring reproducible component quality. The external flow around the material feed nozzle already influences the material feed nozzle. In particular, the material in the material feed nozzle is advantageously flowed around from the material feed zone, possibly all the way to the material reservoir.

[0020] Furthermore, the object is achieved by a device according to the features of claim 8. The material feed nozzle of the device has an inner and outer wall with a cavity therebetween, which is connected to a source of a heated gaseous substance at a location remote from the material feed zone. The device is configured to introduce the heated gaseous substance at this location and transport it within the cavity to the material feed zone, and to guide it from the material feed zone through the material feed nozzle to the material reservoir, with the heated gaseous substance flowing around the solid material.

[0021] The device also advantageously ensures that the material, which is usually in the form of granules and located in the material feed nozzle, is dried and / or prepared for processing. This prevents hydrolytic and / or oxidative material damage during melting, as well as air and / or moisture inclusions in the discharged material, ensuring reproducible component quality.

[0022] Advantageous further developments are the subject of the dependent patent claims.

[0023] Preferably, at least dried air and / or nitrogen is introduced as the heated gaseous substance. Advantageously, hydrogen (moisture) is extracted from the raw material / granulate by the heated air / nitrogen, and oxygen is extracted from the (ambient) air by the heated nitrogen. Preferably, the point remote from the material feed zone is the first end of the material feed nozzle, with the heated gaseous substance being transported along the material feed nozzle to the material feed zone. This advantageously allows the entire material feed nozzle to be heated in an energetically favorable manner.

[0024] In a preferred embodiment, the cavity is closed at the first end of the material feed nozzle and open at the second end of the material feed nozzle toward the material intake zone, with the heated gaseous substance being guided countercurrently along the material feed nozzle to the material intake zone. This advantageously allows the heated gaseous substance to effectively flow through the entire material intake nozzle.

[0025] Preferably, in a further embodiment of the method which advantageously ensures reproducible component quality, a temperature of the heated gaseous substance and / or a duration of drying is individually controlled.

[0026] Preferably, in another embodiment of the method which advantageously ensures reproducible component quality, a quantity of the heated gaseous substance is adjusted depending on a size of the material feed hopper and a material throughput.

[0027] It is also preferable that a volume flow and / or a temperature of the heated gaseous substance is advantageously adjusted as protection against over-drying of the solid material.

[0028] The heated gaseous substance preferably contains dried air and / or nitrogen. Advantageously, hydrogen (moisture) is removed from the raw material / granulate by the heated air / nitrogen, and oxygen is removed from the (ambient) air by the heated nitrogen.

[0029] Preferably, the first end of the material feed nozzle is located at the point remote from the material feed zone, thereby advantageously utilizing the entire length of the material feed nozzle for heating. Preferably, the cavity is closed at the first end of the material feed nozzle and open at the second end of the material feed nozzle toward the material feed zone, advantageously allowing the heated gaseous substance to be introduced into the area of ​​the material feed zone in a targeted manner, thereby keeping as much of the material in the material feed as possible in a dry state.

[0030] In a preferred embodiment, the cavity is arranged and configured such that the heated gaseous substance is guided countercurrently along the material feed nozzle to the material intake zone. This allows the material feed nozzle to be heated advantageously and in an energy-efficient manner to support the drying process.

[0031] Preferably, in an embodiment of the device which advantageously meets the space requirements of the device, the material feed nozzle is connected laterally or vertically to the material feed zone of the plasticizing unit.

[0032] The features listed individually in the patent claims can be combined with one another in a technologically meaningful manner and can be supplemented by explanatory facts from the description and by details from the figures, whereby further embodiments of the invention are shown.

[0033] Short description of the characters

[0034] The invention will now be explained in more detail using an exemplary embodiment. Fig. 1 shows a schematic view of the structure of an apparatus for producing a three-dimensional object by additive manufacturing,

[0035] Fig. 2 is a sectional view of a material feed nozzle according to the invention,

[0036] Fig. 3 shows a device according to the invention for air drying solid material in sectional view,

[0037] Fig. 4 shows a material storage unit with a material feed hopper to a plasticizing unit according to the prior art.

[0038] Detailed description of preferred embodiments

[0039] The invention will now be explained in more detail by way of example with reference to the accompanying drawings. However, the embodiments are only examples and are not intended to limit the inventive concept to a specific arrangement. Before describing the invention in detail, it should be pointed out that it is not limited to the specific components of the device and the specific method steps, since these components and methods can vary. The terms used herein are intended to describe particular embodiments only and are not used in a limiting sense. Furthermore, when the singular or indefinite article is used in the description or claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0040] Figure 4 depicts a material reservoir 2 with a material feed hopper 3 and a material feed nozzle 5 connected thereto, with, in the exemplary embodiment, a lateral material feed to the plasticizing unit according to the prior art. It can be seen that only the material in the material reservoir 2 and the material feed hopper 3 is flowed through by the heated and dried air flowing in via a first coupling piece 11.

[0041] The term "material" or "solid, plasticized material" is to be understood broadly and includes, in particular but not exclusively, plastics, silicone, or other thermoplastic and / or elastomeric materials, such as ceramic, metallic, and / or powdered materials, as well as paper, cellulose, starch, cork, etc., as well as mixtures of such plasticizable materials. Recycled materials can also be used.

[0042] Fig. 1 shows schematically the structure of a device for producing a three-dimensional object 16 by means of additive manufacturing such as an additive manufacturing unit.

[0043] Solid material is fed to a material storage unit 2 via a feed unit, which in the exemplary embodiment is designed as a hopper. From there, the material is fed to a plasticizing unit 1, in which it is plasticized and fed, for example, by a conveyor screw, to a discharge unit 15. From there, it is fed, for example, via a discharge nozzle into a construction space

[0044] 13 to produce an object 16 which is placed on a slide

[0045] 14 is manufactured. The material can be discharged dropwise and / or strandwise. Fig. 3 shows a section of such a device for producing a three-dimensional object 16 from solid, plasticized material by means of additive manufacturing in the region of the material feed zone. It has material preparation with at least one additive manufacturing unit. The material preparation can take place continuously and / or discontinuously. The additive manufacturing unit has at least one discharge unit 15 for the plasticized material and at least one plasticizing unit 1 arranged upstream of this for plasticizing the solid material. The discharge unit 15 can discharge the material continuously and / or discontinuously.Upstream of the plasticizing unit 1 is a material reservoir 2, which may, for example, have a material feed hopper 3 arranged on an underside of the material reservoir 2 or integrated into the underside of the material reservoir 2. Connected to the material reservoir 2 is a material feed nozzle 5 as shown in Fig. 2, the first end of which is operatively connected to the material reservoir 2 and the second end 6 of which is operatively connected to a material intake zone 7 of the plasticizing unit 1. However, the material feed nozzle 5 can be arranged in any desired manner. For example, lateral and / or top-mounted material feeds are also possible.

[0046] In the exemplary embodiment, the material feed hopper 3 can be connected directly to a first end 4 of the material feed nozzle 5 and indirectly via a second end 6 of the material feed nozzle 5 to the material intake zone 7 of the plasticizing unit 1. The material reservoir 2 and the material feed nozzle 5, as well as possibly also the material feed hopper 3, are designed to be filled with the solid material.

[0047] The material feed nozzle 5 has an inner wall 8 and an outer wall 9 with a cavity 10 therebetween. The cavity preferably completely surrounds the material feed nozzle like a cylindrical shell.

[0048] According to the method, a source of a heated gaseous substance (not shown in the drawing) is connected to the cavity 10 via a coupling piece 11. Heated gaseous substance is introduced into the cavity 10 between the inner wall 8 and the outer wall 9 of the material feed nozzle 5 at a location remote from the material intake zone 7, with the heated gaseous substance being transported to the material intake zone 7. From there, this heated gaseous substance is guided from the material intake zone 7 through the material feed nozzle 5 to the material reservoir 2, with the heated gaseous substance flowing around the solid material. The heated gaseous substance flows in the direction of arrow 12 through the coupling piece into the cavity 10 and through the cavity to the material intake zone and back through the material feed nozzle 5 to the material reservoir 2.The heated gaseous substance can flow through the entire material storage 2 and then flow out into the open, for example through an opening at the top, which may be provided with a filter, and thus transport the moisture away from the material storage.

[0049] The heated gaseous substance can contain dried air and / or nitrogen. Advantageously, hydrogen (moisture) is removed from the raw material / granulate by the heated air / nitrogen, and oxygen is removed from the (ambient) air by the heated nitrogen. During the process, heated nitrogen can be introduced, for example, and heated air can be introduced for process preparation. This largely prevents oxidative or hydrolytic material degradation before or during the process. The simultaneous introduction of both substances is also possible.

[0050] Preferably, the point remote from the material feed zone 7 is the first end 4 of the material feed nozzle 5, wherein the heated gaseous substance is transported along the material feed nozzle 5 to the material feed zone 7. The material feed nozzle 5 can thus be heated by the gaseous substance along its entire length.

[0051] In a preferred embodiment, the cavity 10 is closed at the first end 4 of the material feed nozzle 5 and open at the second end 6 of the material feed nozzle 5 in the direction of the material feed zone 7, wherein the heated gaseous substance is guided in the countercurrent principle along the material feed nozzle 5 to the material feed zone 7.

[0052] Preferably, the coupling piece 11 is connected to the cavity and the source of the heated gaseous substance, wherein the device is configured to introduce heated gaseous substance into the cavity 10 between the inner 8 and outer 9 walls of the material feed nozzle 5 when the material reservoir 2, material feed hopper 3, and material feed nozzle 5 are filled with the solid material. The heated gaseous substance is transported to the material intake zone 7 and, in the exemplary embodiment, rises through the material feed nozzle 5 to the material reservoir 2, flowing around the solid material. Other geometric arrangements are possible.

[0053] In order to meet the space requirements of the device, the material feed nozzle 5 is advantageously connected laterally or vertically to the material feed zone 7 of the plasticizing unit 1.

[0054] In an embodiment that takes into account the amount of material required for the application, the size of the material feed hopper 3 is advantageously adjustable.

[0055] In order to advantageously ensure a reproducible component quality in the plastic granulate, the heated gaseous substance can be further tempered and / or dried by means of a dryer integrated into the device.

[0056] For the same purpose, the heated gaseous substance can be introduced at a pressure between 6 and 10 bar via a compressed gas connection connected to the dryer.

[0057] By adjusting the amount of heated gaseous substance depending on the size of the material feed hopper 3 and the material throughput through the process, it is also ensured that a reproducible component quality is achieved.

[0058] Reproducible component quality can also be ensured by adjusting the volume flow and / or the temperature of the heated gaseous substance to protect against over-drying of the solid material, or by individually controlling the temperature of the heated gaseous substance and / or the drying time.

[0059] It goes without saying that this description is susceptible to various modifications, changes, and adaptations within the scope of equivalents to the appended claims.

[0060] 1 plasticizing unit

[0061] 2 material storage

[0062] 3 material feed hoppers

[0063] 4 first end of 5

[0064] 5 material feed nozzles

[0065] 6 second end of 5

[0066] 7 Material feed zone

[0067] 8 inner wall

[0068] 9 outer wall

[0069] 10 Cavity of the material feed nozzle

[0070] 11 Coupling piece

[0071] 12 Arrow (flowing gaseous substance)

[0072] 13 Installation space

[0073] 14 slides

[0074] 15 discharge unit

[0075] 16 Item

Claims

Patent claims 1. A method for air drying solid, plasticizable material for use in a device for producing a three-dimensional object (16) by means of additive manufacturing with a material preparation, wherein the device has at least one additive manufacturing unit with: - at least one plasticising unit (1) arranged to plasticise the solid material for discharge by a discharge unit (15), - at least one material storage device (2) arranged upstream of the plasticising unit (1), - a material feed nozzle (5) connected to the material reservoir (2), the first end of which is operatively connected to the material reservoir (2) and the second end (6) of which is operatively connected to a material feed zone (7) of the plasticising unit (1), - wherein the material reservoir (2) and the material feed nozzle (5) are filled with the solid material, characterized in that the material feed nozzle (5) has an inner wall (8) and an outer wall (9) with a cavity (10) therebetween, the method comprising: - connecting a source of a heated gaseous substance to the cavity (10), - introducing the heated gaseous substance into the cavity (10) of the material feed nozzle (5) at a location remote from the material feed zone (7), whereby the heated gaseous substance is transported to the material feed zone (7), - guiding the heated gaseous substance from the material feed zone (7) through the material feed nozzle (5) to the material storage (2), wherein the heated gaseous substance flows around the solid material.

2. Method according to claim 1, characterized in that at least dried air and / or nitrogen is introduced as the heated gaseous substance.

3. Method according to claim 1 or 2, characterized in that the point remote from the material feed zone (7) is the first end (4) of the material feed nozzle (5), wherein the heated gaseous substance is transported along the material feed nozzle (5) to the material feed zone (7).

4. Method according to one of the preceding claims, characterized in that the cavity (10) is closed at the first end (4) of the material feed nozzle (5) and is open at the second end (6) of the material feed nozzle (5) in the direction of the material feed zone (7), wherein the heated gaseous substance is guided in the countercurrent principle along the material feed nozzle (5) to the material feed zone (7).

5. Method according to one of the preceding claims, characterized in that a temperature of the heated gaseous substance and / or a duration of drying is individually controlled.

6. Method according to one of the preceding claims, characterized in that a quantity of the heated gaseous substance is adjusted depending on a size of the material feed hopper (3) and a material throughput.

7. Method according to one of the preceding claims, characterized in that for use as over-drying protection, a volume flow and / or a temperature of the heated gaseous substance is adjusted.

8. Device for producing a three-dimensional object (16) from solid, plasticizable material by means of additive manufacturing with a material preparation, wherein the device has at least one additive manufacturing unit, with - at least one plasticising unit (1) arranged to plasticise the solid material for discharge by a discharge unit (15), - at least one material storage device (2) arranged upstream of the plasticising unit (1), - a material feed nozzle (5) connected to the material reservoir (2), the first end of which is operatively connected to the material reservoir (2) and the second end (6) of which is operatively connected to a material feed zone (7) of the plasticising unit (1), - wherein the material reservoir (2) and the material feed nozzle (5) are designed to be filled with the solid material, characterized in that the material feed nozzle (5) has an inner wall (8) and an outer wall (9) with a cavity (10) therebetween, which is connected to a source of a heated gaseous substance at a location remote from the material intake zone (7), and that the device is designed to introduce the heated gaseous substance into the cavity (10) at the location and to transport it in the cavity (10) to the material feed zone (7) and to guide it from the material feed zone (7) through the material feed nozzle (5) to the material reservoir (2), wherein the heated gaseous substance flows around the solid material.

9. Device according to claim 8, characterized in that the heated gaseous substance contains dried air and / or nitrogen.

10. Device according to claim 8 or 9, characterized in that the point remote from the material feed zone (7) is the first end (4) of the material feed nozzle (5).

11. Device according to one of claims 8 to 10, characterized in that the cavity (10) is closed at the first end (4) of the material feed nozzle (5) and is open at the second end (6) of the material feed nozzle (5) in the direction of the material feed zone (7).

12. Device according to one of claims 8 to 11, characterized in that the cavity (10) is arranged and configured such that the heated gaseous substance is guided in the countercurrent principle along the material feed nozzle (5) to the material feed zone (7).

13. Device according to one of claims 8 to 12, characterized in that the material feed nozzle (5) is connected laterally and / or vertically to the material feed zone (7) of the plasticizing unit (1).

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