Post-treatment process for increasing the hot strength of a formed part made of particulate material and binder, 3D printing arrangement and formed part

Abstract

A post-treatment process for increasing the hot strength of a formed part (100) made of particulate material and binder is disclosed, wherein the formed part (100) is formed a part manufactured by 3D printing (S72) and after its manufacture is heated (S30) using a heating device (40), and the heated formed part (100) is exposed (S50) to an atmosphere enriched with gaseous water generated by supplying water.

Claims

1-19. (canceled)

20. A 3D printing process comprising the steps of: (a) producing a formed part (100) from a particulate material and a binder within a bed of the particulate material in which the particulate material is loose; (b) removing the formed part (100) from the bed; (c) heating the formed part (100) using a heating device (40); (d) supplying external water to generate an atmosphere enriched with gaseous water; (e) exposing the heated formed part (100) during step (c) to the atmosphere enriched with gaseous water; wherein the hot strength of the formed part (100) is increased during step (e).

21. The process of claim 20 wherein the formed part (100) is a casting core or a casting mold or a casting mold section.

22. The process of claim 20 wherein the binder comprises a water glass.

23. The process of claim 20 wherein the particulate material is selected from the group consisting of quartz sand particles, alumina sand particles, aluminum silicate sand particles, zircon sand particles, olivine sand particles, silicate sand particles, chromite sand particles and combinations thereof.

24. The process of claim 20 wherein step (a) comprises three-dimensional printing the formed part (100).

25. The process of claim 20 wherein step (a) includes hardening the binder using a microwave device.

26. The process of claim 20 further comprising a step of hardening the binder using a microwave device prior to step (b).

27. The process of claim 20 wherein the hot strength of the formed part (100) is increased by at least 30% as a result of step (e).

28. The process of claim 20 wherein during step (e) at least a portion of the formed part (100) is infiltrated by the gaseous water and as a result of the infiltration the hot strength in at least said portion is increased by modifying the binder in said portion.

29. The process of claim 28 wherein the portion comprises a rim zone (102) of the formed part (100) having a depth of at least 250 m.

30. The process of claim 20 wherein the heating device (40) is selected from the group consisting of a continuous furnace, a convection furnace, a convector, a hot air furnace, and combinations thereof.

31. The process of claim 20 wherein step (e) is performed in a heating space (42) of the heating device (40).

32. The process of claim 20 wherein during step (e) the formed part (100) is exposed for a predetermined period of at least 30 seconds to the atmosphere enriched with gaseous water.

33. The process of claim 20 wherein during step (c) at least a portion of the formed part (100) is heated to a temperature of greater than or equal to 150 C.

34. The process of claim 20 wherein the atmosphere enriched with gaseous water has a content of gaseous water which is greater than or equal to 50 g/m.sup.3.

35. The process of claim 20 further comprising a step of casting metal into the formed part (100) after step (e).

36. A device comprising: a 3D printer (20); a heating device (40) having a heating space (42) configured to accommodate a formed part (100) manufactured by means of the 3D printer (20); and a water supply device (44) configured to supply external water to the heating space (42); wherein the heating device (40) is adapted to create a gaseous water enriched atmosphere in the heating space (42) from the external water.

37. The device of claim 36 further comprising a controller (60) configured to drive the water supply device (44) to supply the external water to the heating space (42) for a predetermined period of time.

Description

[0037] Exemplary but non-restrictive embodiments of the present invention are shown in the Figures and are explained in more detail below.

[0038] FIG. 1 illustrates a post-treatment process for increasing the hot strength of a formed part made of particulate material and binder according to a first embodiment of the invention.

[0039] FIG. 2 illustrates a post-treatment process for increasing the hot strength of a formed part made of particulate material and binder according to a second embodiment of the invention.

[0040] FIG. 3 illustrates a post-treatment process for increasing the hot strength of a formed part made of particulate material and binder according to a third embodiment of the invention.

[0041] FIG. 4 illustrates a post-treatment process for increasing the hot strength of a formed part made of particulate material and binder according to a fourth embodiment of the invention.

[0042] FIG. 5 illustrates a post-treatment process for increasing the hot strength of a formed part made of particulate material and binder in combination with a process/step of casting metal according to a fifth embodiment of the invention.

[0043] FIG. 6 illustrates a simplified, schematic view of a 3D printing arrangement according to a sixth embodiment of the invention.

[0044] FIG. 7 illustrates a simplified schematic view of a formed part according to a seventh embodiment of the invention.

[0045] In the following detailed description, reference is made to the attached Figures which form part thereof and in which specific embodiments are shown for illustration, in accordance with which the invention may be carried out.

[0046] It shall be understood that other embodiments may be used and that structural or logical changes may be made without departing from the scope of protection of the present invention. It shall be understood that the features of the various exemplary embodiments and aspects described herein may be combined unless specifically stated otherwise. The following detailed description should therefore not be construed in a restrictive sense, and the scope of protection of the present invention is defined by the attached claims.

[0047] Within the scope of this description, terms such as connected, joined and coupled may be used to describe both a direct and an indirect connection and a direct or indirect coupling.

[0048] In the Figures, identical or similar elements shall be provided with identical reference signs where appropriate.

[0049] As shown in FIGS. 1-5, in a post-treatment process for increasing the hot strength (hereinafter also referred to as process for increasing the hot strength) of a formed part 100 made of particulate material and binder, in accordance with the various embodiments of the invention, the formed part 100 produced by 3D printing is heated after its manufacture using a heating device 40 (step S30) and the heated formed part 100 is exposed to an atmosphere enriched with gaseous water generated by supplying water (step S50). The various embodiments of the invention thus indicate processes for the treatment and post-treatment, respectively, of manufactured formed parts 100.

[0050] The formed part 100 may be a formed part for casting, for example a casting core or a casting mold or a casting mold section. The particulate material from which the formed part 100 is made may contain sand particles. The sand particles may be selected from the group consisting of quartz sand particles, alumina sand particles, aluminum silicate sand particles, zircon sand particles, olivine sand particles, silicate sand particles, chromite sand particles and combinations thereof. The binder from which the formed part 100 is made may, for example, comprise water glass respectively silicate, for example sodium water glass respectively sodium silicate. The binder may bond or glue the particles of the particulate material and may thus hold them together.

[0051] The formed part 100 is a formed part 100 manufactured by 3D printing (see step S72 in FIGS. 2 to 4). For example, the formed part 100 may be a formed part 100 manufactured by binder jetting. The formed part 100 may, for example, be manufactured by means of a process described in patent applications DE 10 2014 112 447 and DE 10 2009 056 687, the disclosure content of which is incorporated herein by this reference. In this respect, for example, water glass may be applied or printed onto a layer of the unsolidified particulate material by means of a print head of a 3D printer.

[0052] After its manufacture by 3D printing, the formed part 100 may be embedded in a bulk material made of loose particulate material, which, for example, is received/accommodated in a building box together with the formed part 100, and may be unpacked from the bulk material before feeding the formed part 100 to the heating device 40 (see step S90 in FIGS. 3 and 4). Optionally, a hardening of the binder may be carried out before unpacking the formed part 100 (see step S110 in FIG. 4). Hardening may, for example, be carried out using a microwave device. Alternatively or in addition, repeated hardening, for example thermal hardening, may be carried out during the manufacture of the formed part 100.

[0053] According to the various embodiments of the invention, the heated formed part 100 may be exposed to gaseous water in the atmosphere enriched with gaseous water in such a way that the formed part 100 is infiltrated by the gaseous water in at least one portion thereof and the hot strength in at least that portion is increased as a result of the infiltration, for example by modifying the binder in that portion, for example by changing the polymer configuration of the binder. The portion may comprise a rim zone 102 of the formed part 100 (see FIG. 7), for example a rim zone 102 with a depth of at least 250 m.

[0054] The heating device 40 used in the process may be any suitable heating device, e.g. a continuous furnace, a convection furnace, a convector, a hot air furnace or combinations thereof. The heated formed part 100 may, for example, be exposed to the atmosphere enriched with gaseous water in the heating device 40, for example by supplying (liquid and/or gaseous) water to a heating space 42 of the heating device 40 in which the formed part 100 is received/accommodated/is to be received/accommodated. For example, the heated formed part 100 may be exposed to the atmosphere enriched with gaseous water in the heating device 40 by supplying or placing an open container containing liquid water in the heating space 42. Alternatively or in addition, the heated formed part 100 may be exposed to the atmosphere enriched with gaseous water in the heating device 40 by feeding liquid water into the heating space 42 by means of a suitable device, e.g. an injection nozzle.

[0055] In the process, the formed part 100 or at least a portion thereof may, for example, be heated to a temperature of at least 150 C., and the heated formed part 100 may be exposed in the process, for example for a predetermined period of time (for example, at least 30 seconds) to the atmosphere enriched with gaseous water generated by supplying water, having, for example, a gaseous water content of greater than or equal to 50 g/m.sup.3.

[0056] According to various embodiments of the invention, the hot strength of the treated formed part 100 may be increased by at least 30% as compared to the original hot strength (i.e. as compared to the hot strength of the untreated formed part).

[0057] The process described above for increasing the hot strength may be followed by a process/step of casting metal, for example aluminum or an alloy thereof, using the formed part 100 (see step S130 in FIG. 5).

[0058] As shown in FIG. 6, a 3D printing arrangement according to embodiments of the invention comprises a 3D printer 20 and a heating device 40 having a heating space 42 configured to receive/accommodate a formed part 100 manufactured by means of the 3D printer 20 and a water supply device 44 configured to supply gaseous water to the heating space 42. The 3D printer 20 may, for example, be configured as described in patent applications DE 10 2014 112 447 and DE 10 2009 056 687, the disclosure content of which is incorporated herein by this reference, and may include, for example, a building box with a building platform, a coating device and a print head. The heating device 40 may be configured as described above. The water supply device 44 may, for example, comprise an injection nozzle 46 which may, for example, be configured to supply gaseous and/or liquid water to the heating space 42.

[0059] The 3D printing arrangement may further include a controller 60 configured to control the water supply device 44 to supply water to the heating space 42 for a predetermined period of time. The controller 60 may, for example, be coupled to the injection nozzle 46 of the supply device 44 to control the same, for example to control an open state and a closed state of the injection nozzle 46. The controller 60 may, for example, be arranged to control the temperature in the heating space 42. In the heating space 42, a temperature sensor 80 may, for example, be arranged which is coupled to the controller 60 and which is configured to determine the temperature in the heating space 42. For example, a humidity sensor 82 may be arranged in the heating space 42, which is coupled to the controller 60 and which is configured to determine the content of gaseous water (and the absolute air humidity, respectively) in the heating space 42.

Test Example

[0060] In the following, a test example from a series of tests carried out by the applicant to verify the invention is illustrated.

[0061] Table 1 shows the relative hot strengths of different test specimens. All test specimens were manufactured from the same material (with the exception that test specimens 1, 3 and 4 did not contain any hot strength enhancing additive) with the same manufacturing process and treated with the same post-treatment (if applicable). For this purpose, the test specimens were manufactured by means of binder jetting using quartz sand as particulate material and sodium silicate as binder (printed as an aqueous solution), and had a dimension of 172 mm22.4 mm8 mm (HDT test bar, HDT: Hot Deformation Test). After the test specimens had been manufactured by 3D printing, the test specimens were unpacked and then immediately subjected to a process according to the invention for increasing the hot strength (except for test specimens 1 and 2). A separate hardening was not carried out.

[0062] As shown by Table 1, no additive for enhancing hot strength was added to the first test specimen and the test specimen was not treated with the process according to the invention. An additive to improve hot strength was added to the second test specimen, and the test specimen was not treated with the process according to the invention. No hot strength additive for enhancing hot strength was added to the third and fourth test specimens and the test specimens were treated with the process according to the invention. An additive to improve hot strength was added to the fifth and sixth test specimens, and the test specimens were treated with the process according to the invention. The fourth test specimen is a reproduction of the third test specimen, and the sixth test specimen is a reproduction of the fifth test specimen.

[0063] The hot strength was determined using the HOT-FLEX, Hot Deformation Tester of BENETLAB. In order to determine the hot strength, the test specimen was clamped in the test device, a distance meter with test weight (mass: 26.02 g) was placed on the test specimen, the test specimen was heated from below by means of a gas flame (temperature: approx. 1,200 C.; on the test device, a fuel gas flow of 510.sup.8 L/h and an air flow of 13 L/h may, for example, be set) and the deflection of the test specimen was measured over time. From the elapsed time until a given deflection downwards (e.g. of 2 mm) was reached, the relative hot strengths below were determined. The relative hot strength of the first test specimen was set to 1. The relative hot strengths of the other test specimens were determined by dividing the elapsed time of a corresponding test specimen by that of test specimen 1. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Test Treatment of Relative specimen Additive.sup.1 test specimen.sup.2 hot strength 1 1.0 2 + 1.5 3 + 2.1 4 + 2.1 5 + + 2.0 6 + + 2.2 .sup.10.5% by mass of a powder additive was added to the sand to increase the hot strength. .sup.2A convection furnace was heated to 260-280 C.; then liquid water was injected into the furnace (about 100 ml); then the test specimen was introduced into the furnace and left in the furnace for 20 minutes, with liquid water being injected at regular intervals.

[0064] A comparison of the first test specimen with the third and fourth test specimens shows that the process according to the invention is able to increase the hot strength of a treated formed part 100, to which no additive is added to increase the hot strength, by more than 100% compared to the original hot strength of the formed part 100. A comparison of the second test specimen with the fifth and sixth test specimens shows that the process according to the invention is able to increase the hot strength of a treated formed part 100, to which an additive is added to increase the hot strength, by approximately 40% compared to the original hot strength of the formed part 100. This means that the process according to the invention is also able to increase the hot strength of formed parts 100 to which an additive is added to increase the hot strength.

[0065] The comparison of the third and fourth test specimens with the fifth and sixth test specimens also shows that in the present examples the addition of an additive can be omitted, if the process according to the invention is used.

[0066] The previous description of specific exemplary embodiments of the present invention was presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the disclosed precise forms, and it is self-evident that many modifications and variations are possible in the light of the above teaching. The exemplary embodiments have been selected and described to explain certain principles of the invention and its practical application in order to enable a person skilled in the art to manufacture and apply various exemplary embodiments of the present invention as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the claims attached hereto and their equivalents.