Device and process for depowdering pre-sintered articles fabricated by selective binderjetting method

Abstract

A device (1) and process for depowdering pre-sintered articles (8) fabricated by selected binder jetting method which enables separation of the pre-sintered articles from the powder material, wherein the pre-sintered articles have been manufactured in a build box (15) using 3D printing technology comprising selective binder jetting onto the powder material. The device and process allow for depowdering of a large number of pre-sintered articles contained in a build box. This way of depowdering a large number of pre-sintered articles is important because depowdering of the pre-sintered articles is in practice one of the more time-consuming processes that represent a bottleneck in the fabrication of 3D printed articles. The device makes it possible to reduce a possibility of damage to pre-sintered articles during the depowdering process, as depowdering is gradual and controlled.

Description

[0001] DEVICE AND PROCESS FOR DEPOWDERING PRE-SINTERED ARTICLES FABRICATED BY SELECTIVE BINDERJETTING METHOD

[0002] The invention relates to a device and process for depowdering pre-sintered articles to enable separation of the pre-sintered articles from the powder material, wherein the presintered articles have been manufactured in a build box using 3D printing technology comprising selective binder jetting onto the powder material, which is in a liquid state during the jetting process and then solidifies, and where, after the jetting process has been completed, the pre-sintered articles are contained in the build box surrounded by the powder material.

[0003] 3D printing methods include selective binder jetting from printheads that allow simultaneous point jetting, or print tubes that allow simultaneous selective in-line jetting, onto successively deposited layers of a powder material containing, for example, metal, ceramics, glass, polymers, etc. Multiple successive depositions of powder material and binder jetting in several substantially horizontal planes make it possible to produce a three-dimensional article shape.

[0004] Said selective binder jetting achieves the desired shape of the pre-sintered article and, once the binder has solidified, the pre-sintered article retains its shape until sintering. Before sintering, the article needs to be separated from the powder material surrounding it and cleaned of powder material as much as possible. Sintering, which means heat treatment of the pre-sintered article, is necessary to give the article its final strength. During sintering, the powder material bound together by the solidified binder is thickened or fused by temperature to give the final strength of the article after cooling, while retaining the original shape defined by the selective binder deposition.

[0005] Typically, the pre-sintered article manufacturing stage is carried out in a build box, in which layers of powder material are deposited, on which layers binder is selectively jetted. The deposition of the powder material and binder jetting is repeated until the build box is filled with one or more pre-sintered articles which are completely surrounded by the powder material on which the binder has not been jetted. The 3D printing method described here has the advantage of being able to produce several pre-sintered articles at once in one build box. Pre-sintered articles in a build box are generally not attached to a base that would otherwise allow easier handling of the otherwise fragile pre-sintered article during cleaning. Therefore, the removal and cleaning of pre-sintered articles from the build box requires careful handling of the pre-sintered articles. In certain embodiments, during each deposition of a single layer of powder material, a sliding base of the build box is lowered by approximately the thickness of a single layer of powder material, thereby allowing the binder to be jetted, as a rule, in substantially the same plane, substantially at the level of the top opening of the build box.

[0006] In the context of this application, the term depowdering will be used meaningfully to refer to the separation of the pre-sintered articles from the powder material and the removal of the powder material from the surface of the pre-sintered articles to the maximum extent possible. It is desired that the excess powder material from depowdering is collected for re-use.

[0007] Known prior art discloses devices that allow manual or at least partially automatic depowdering. For example, US 2021 / 0046519 A1 discloses manners of extracting presintered articles out of a build box so that a variety of methods can be used for depowdering, including circulating air in a closed chamber, nozzles directing jets of air in a particular direction. Furthermore, the DPS 1000 from Digital Metal uses a thin and precise nozzle to depowder a pre-sintered article, using a jet of air in close proximity to the presintered article to depowder the pre-sintered article on the build plate in such a way that the nozzle is guided around the pre-sintered articles using the data previously used for selective binder jetting. This ensures that the nozzle does not touch the pre-sintered article during depowdering, which reduces the possibility of damaging the pre-sintered article.

[0008] DEVICE OF THE INVENTION

[0009] The device of the invention is a device for depowdering pre-sintered articles fabricated by the selective binder jetting method, which enables separation of the powder material from the pre-sintered articles manufactured in a build box using 3D printing technology comprising selective binder jetting onto the powder material, which is in a liquid state during the jetting process and then solidifies, and where, after the 3D printing process has been completed, the pre-sintered articles are contained in the build box surrounded by the powder material. The advantage of the device and process of the invention is that they provide an alternative solution to existing devices and, in particular, they allow for depowdering of a large number of pre-sintered articles contained in a build box. This way of depowdering a large number of pre-sintered articles is important because depowdering of the presintered articles is in practice one of the more time-consuming processes that represent a bottleneck in the fabrication of 3D printed articles. The device of the invention makes it possible to reduce a possibility of damage to pre-sintered articles during the depowdering process, as depowdering is gradual and controlled. The device of the invention further enables the depowdering process to be carried out automatically.

[0010] The device of the invention comprises a chamber and a depowdering box arranged inside the chamber. The depowdering box comprises a fluidising bed, side walls and at least one outlet opening. The fluidising bed comprises at least one fluidising element connected to a source of compressed gas over all or part of its upper surface.

[0011] In the following, the device and process of the invention will be described in more detail with reference to the figures, where embodiments are shown:

[0012] Figure 1 : Schematic representation of the basic device of the invention.

[0013] Figure 2: A first illustrated embodiment of the device of the invention, wherein a fluidising bed is configured as the build box base with fluidising elements and is connected by vertical sliding means.

[0014] Figures 3A and 3B: A second illustrated embodiment of the device of the invention, where the side walls of the depowdering box are configured as the side walls of a secondary box placed on top of the build box, and with the sliding of the separating plate shown.

[0015] Figure 4: A third illustrated embodiment of the device of the invention, wherein the depowdering box is configured as a combination of a reversible build box and a covering fluidising bed - in the active position.

[0016] Figure 5: A fourth illustrated embodiment of the device of the invention, wherein the depowdering box is configured as a build box in which at least one outlet opening is configured as a lock opening.

[0017] As shown in Figure 1 , the device 1 of the invention comprises a chamber 2 and a depowdering box 3 arranged inside the chamber 2. The depowdering box 3 comprises side walls 4, a fluidising bed 5 and at least one outlet opening 6.

[0018] Prior to depowdering process, the depowdering box 3 contains powder material 7 and presintered articles 8 (at least one pre-sintered article 8).

[0019] The chamber 2 allows the desired atmosphere to be established and prevents the powder material 7 from escaping into the surroundings during the depowdering process. A further advantage of the use of the chamber 2 is that it allows the excess powder material 7 to be collected in several ways, for example by means of an additional filter system, and thus reused. A natural atmosphere may be present in the chamber 2 or, optionally, an inert atmosphere may be established in the chamber 2.

[0020] The fluidising bed 5 is provided over all or part of its upper surface with at least one fluidising element 9 connected to a compressed gas source 10. The fluidising element 9, by blowing air or gas into the powder material 7, causes fluidisation of this material in a fluidisation zone 11 extending approximately 2-3 cm upstream of the fluidising element 9, which means that the powder material 7, which is otherwise dry, composed of solid particles and static, acquires fluid-like dynamic properties. In general, the fluidising element 9 comprises a gas inlet compartment 12 and a permeable face 13 in contact with the powder material 7 during operation, through which the inlet gas exits into the powder material 7. The compartment serves to distribute the inlet gas evenly over the entire permeable face 13. The function of the fluidising element 9 is to fluidise the powder material 7 in the depowdering box 3 and to allow it to flow out through the outlet openings 6. The fluidising element 9 is preferably configured as a fluidising plate.

[0021] At least one outlet opening 6 is provided in the fluidisation zone 11, either in the side walls 4 adjacent to the fluidising bed 5 or between the upper surface of the fluidising bed 5 and the side walls 4, around all or part of the circumference (preferably all of it), or through the fluidising bed 5. The size of the outlet openings 6 is such as to pass the powder material 7 as unobstructed as possible, but not to pass the pre-sintered articles 8. The outlet openings 6 may be provided in various ways, for example in the form of slots, perforations, meshes, lock opening, etc.

[0022] In the context of the present application, terms referring in the singular or plural to particular elements of the invention, e.g. outlet openings 6, fluidising elements 9, permeable faces 13, should be understood as referring to one or more of the aforementioned elements, where reasonable.

[0023] The chamber 2 is provided with a collector 14 for the powder material 7 that is located below the outlet openings 6 so that, during depowdering, the powder material 7 falls by gravity into the collector 14 as it exits the depowdering box 3 through the outlet openings 6.

[0024] The basic fluidisation and depowdering process, when the depowdering box 3 with its contents is arranged in the chamber 2, comprises the following basic steps: a) blowing compressed gas through at least one fluidising element 9, wherein fluidisation of the powdered material 7 is initiated in the fluidisation zone 11 and the powder material 7 flows, inter alia, by gravity through at least one outlet opening 6, wherein the fluidisation zone 11 extends into the interior of the depowdering box 3 approximately 2-3 cm upstream of the fluidising element 9; b) gradual downward movement of the upper layers of the powder material 7 by gravity into the fluidisation zone 11 ; c) fluidising for a sufficient time that all or most of the powder material 7 is drained from the depowdering box 3, leaving the pre-sintered articles 8 on the fluidising bed 5 of the depowdering box 3.

[0025] FIRST ILLUSTRATED EMBODIMENT

[0026] In the first illustrated embodiment (Figure 2), the depowdering box 3 is configured as a combination of a secondary box 3' under which a build box 15 is arranged, wherein the side walls 4 of the depowdering box 3 are substantially the side walls 4' of the secondary box 3', and a fluidising bed 5 substantially configured as a base 17 of the build box 15 with fluidising elements 9, wherein the base 17 of the build box 15 is connected by vertical sliding means 16. The size of the secondary box 3' is preferably such that it can accommodate the entire contents of the build box 15. For example, build boxes 15, by virtue of the 3D printing process, often already comprise vertical sliding means 16 which allow the base 17 of the build box 15 to be lowered in a controlled manner during the printing process and allow the printing process to be carried out in substantially the same plane, substantially at the level of a top opening 18 of the build box 15. The base 17 of the build box 15 with the vertical sliding means 16 can therefore be used, without special adjustments or with appropriate minor adjustments, for controlled raising to achieve upward displacement of the contents into the secondary box 3'. After the contents of the build box 15 have been raised into the secondary box 3', the upper surface of the fluidising bed 5 is preferably located at the same height as, or above, the upper edge of side walls 19 of the build box 15, so that a step is not created between the outlet opening 6 and the fluidising bed 5, which would prevent the powder material 7 from flowing out through the outlet opening 6.

[0027] The outlet openings 6 are provided in the side walls 4' of the secondary box 3' just above the top surface of the fluidising bed 5 and / or are provided in the form of a gap between the top edge of the side walls 19 of the build box 15 or between the top surface of the fluidising bed 5 and the bottom edge of the side walls 4' of the secondary box 3'. Optionally, the size of the outlet openings 6 may be adjusted by raising or lowering the secondary box 3' relative to the fluidising bed 5, or by raising or lowering the fluidising bed 5 relative to the secondary box 3'.

[0028] Of course, before starting the basic fluidisation and depowdering process, the build box 15 must be moved under the secondary box 3' located in the chamber 2. The manipulation of the build box 15 is carried out in known ways by means of manipulation means, such as a forklift truck, a crane, a conveyor belt, a (robotic) manipulator, etc., which serve, for example, to move the build box 15. If the build box 15, when placed under the secondary box 3', is located outside the chamber 2, e.g. under the chamber 2, it must be ensured that the interior of the build box 15 is in an airtight contact with the chamber 2, e.g. by the use of fasteners and gaskets.

[0029] Preferably, an individual fluidising element 9 is secured to the base 17 of the build box 15 by means of fastening means, e.g. screws, which provide a strong and tight connection between the fluidising element 9 and the base 17 of the build box 15. Preferably, a gasket is used between the fluidising element 9 and the base 17 of the build box 15 to prevent leakage of the compressed gas.

[0030] The fluidisation and depowdering process according to the first illustrated embodiment comprises the following pre-steps:

[0031] 1. Positioning of the build box 15 and / or the secondary box 3' so that the build box 15 is located below the secondary box 3' located in the chamber 2, ensuring an air-tight contact of the interior of the build box 15 with the chamber 2.

[0032] 2. The base 17 of the build box 15 with the fluidising elements 9, which is also the fluidising bed 5 of the depowdering box 3 or secondary box 3', is raised by means of the vertical sliding means 16 to the top of the side walls 19 of the build box 15 in order to move the contents (powder material 7 and pre-sintered articles 8) from the build box 15 upwards into the secondary box 3', whereby the depowdering device 1 is formed.

[0033] The outlet openings 6 are preferably provided in the form of a gap between the top edge of the side walls 19 of the build box 15 or between the fluidising bed 5 and the bottom edge of the side walls 4' of the secondary box 3'. The outlet openings 6 may be formed at the same time as pre-step 2 or after pre-step 2. The advantage of forming the outlet openings 6 after pre-step 2 is that the contents are prevented from leaking in pre-step 2, i.e. when the contents are moved upwards into the secondary box 3'.

[0034] The basic fluidisation and depowdering process is then carried out following the basic steps a. to c.

[0035] One of the advantages of the first illustrated embodiment is that it allows for the simultaneous depowdering of larger quantities of powder material 7 from a larger number of pre-sintered articles 8, as well as its simplicity, as it allows for the use of a minimally modified build box 15, which is commonly used in 3D printing. A further advantage is that the build box 15 does not need to be moved into the chamber 2 in case it is located close to the chamber 2, e.g. underneath the chamber 2, which makes it easier to manipulate the build box 15.

[0036] SECOND ILLUSTRATED EMBODIMENT

[0037] In the second illustrated embodiment (Figures 3A and 3B), the depowdering box 3 is configured as a combination of a secondary box 3' that is adequately placed above the build box 15, wherein the side walls 4 of the depowdering box 3 are substantially the side walls 4' of the secondary box 3', and a fluidising segment 5' that during the depowdering and fluidisation process forms the fluidising bed 5 of the depowdering box 3, wherein the fluidising segment 5' is arranged inside the chamber 2 separately from the build box 15. The size of the secondary box 3' is such that it can accommodate at least a portion of the contents of the build box 15, preferably one horizontal layer of pre-sintered articles 8 in the powder material 7. During the 3D printing process, an appropriate spacing of approximately 20 mm is ensured between the individual horizontal layers of pre-sintered articles 8 in the build box 15.

[0038] As shown in Figure 3B, the outlet openings 6 are provided in the form of a gap between the top surface of the fluidising segment 5' and the bottom edge of the side walls 4' of the secondary box 3, or are provided in the side walls 4' of the secondary box 3' closely above the upper surface of the fluidising segment 5'. In an alternative embodiment (not shown in the figures), the outlet openings 6 are provided as through holes in the fluidising segment 5' or a combination of all of the above forms of outlet openings 6. The collector 14 for the powder material 7 is located below the outlet openings 6 so that, during depowdering, the powder material 7 falls by gravity into the collector 14 as it exits the depowdering box 3 through the outlet openings 6.

[0039] The build box 15 comprises a sliding base 17 which can be raised and lowered in a controlled manner by means of vertical sliding means 16, whereby the raising of the sliding base 17 displaces at least part of the contents of the build box 15 upwards into the secondary box 3'. The build boxes 15, by virtue of the 3D printing process, often already contain vertical sliding means 16 for a controlled raising and lowering of the sliding base 17, as described above, which, without special adjustments or with appropriate minor adjustments, allow controlled raising to meet the needs of the process of the invention, namely to achieve the displacement of at least part of the contents into the secondary box 3'. The height of a respective controlled raising of the sliding base 17 of the build box 15 is set to allow at least one or more complete horizontal layers of pre-sintered articles 8 to be moved into the depowdering box 3 or the secondary box 3', respectively.

[0040] The device 1 according to the second illustrated embodiment further comprises a dividing plate 20 and a dividing slot 21. When one or more horizontal layers of pre-sintered articles 8 are displaced upwards from the build box 15 into the secondary box 3', the dividing plate 20 is substantially horizontally inserted between the top of the build box 15 and the bottom edge of the secondary box 3' from its starting position in the dividing slot 21 provided for this purpose between the upper edge of the build box 15 and the bottom edge of the secondary box 3'. The dividing plate 20 is inserted into the powder material 7 in the area of the gap between the individual horizontal layers of the pre-sintered articles 8 between the contents that remain in the build box 15 and the contents displaced upwards into the secondary box 3', so the contents get divided. This spacing is achieved during 3D printing by so many single layers, preferably a few 100, of the intermediate layers of the filled powder material 7, on which the binder for the fabrication of the pre-sintered articles 8 is not jetted, that there is sufficient space to allow for the insertion of the dividing plate 20. The edge of the dividing plate 20 penetrating the powder material 7 is preferably sharpened to facilitate its penetration into the powder material 7.

[0041] The pre-sintered articles 8 in the powder material 7 must not be in the same plane as the dividing slots 21 during the penetration of the dividing plate 20, so that the dividing plate 20 does not hit a pre-sintered article 8 and damage it, or does not stop and prevent the depowdering process from continuing. The vertical sliding means 16 optionally comprise a control drive to achieve controlled raising of the sliding base 17. The appropriate raising height of the sliding base 17 can be determined in a variety of known ways, for example from the electronic data required for the 3D printing software, which includes information on the spacing between the layers of the pre-sintered articles 8 and the thickness of the layer of the pre-sintered articles 8. The raising height can be achieved by manual or automatic control of the vertical sliding means 16.

[0042] When the dividing plate 20 is below the secondary box 3', i.e. after its insertion between the build box 15 and the secondary box 3', and during the transfer of the secondary box 3' above the fluidising segment 5', the dividing plate 20 acts as a temporary base of the secondary box 3', preventing the contents, or part of the contents, of the secondary box 3' from escaping during the transfer of the secondary box 3' above the fluidising segment 5'. When the secondary box 3', the temporary base of which is formed by the dividing plate 20, is placed above the fluidising segment 5' in the chamber 2, the dividing plate 20 is withdrawn. Preferably, the dividing plate 20 returns to its starting position awaiting the next cycle. The secondary box 3', which contains a portion of the contents, is located above the fluidising segment 5' in the chamber 2 after the dividing plate 20 has been withdrawn. A slot-shaped outlet opening 6 is provided between the bottom edge of the side walls 4' of the secondary box 3' and the upper edge of the fluidising segment 5', or the outlet opening 6 is provided as a through opening in the fluidising segment 5'. Preferably, the mere sliding of the dividing plate 20 from beneath the secondary box 3', when it is located above the fluidising segment 5', creates an outlet opening 6, the height of which is substantially equal to the thickness of the dividing plate 20. If needed, the size of the outlet opening 6 may be adjusted by raising or lowering the secondary box 3' relative to the fluidising segment 5', or by raising or lowering the fluidising segment 5' relative to the secondary box 3'. Once an outlet opening 6 of the appropriate size has been created, the basic fluidisation and depowdering process is carried out.

[0043] The described movements of the dividing plate 20 are carried out by sliding means of the dividing plate 20 in known ways. In one of the embodiments, the secondary box 3' abuts on the dividing plate 20 during the movement of the secondary box 3' with its contents above the build box 15 and above the fluidising segment 5'.

[0044] After completion of the basic fluidisation and depowdering process, the pre-sintered articles 8 remain on the fluidising segment 5'. The secondary box 3' withdraws to make the pre-sintered articles 8 accessible for further use and the secondary box 3' is ready for a subsequent cycle to receive at least part of the remaining contents of the build box 15, i.e. to be placed above the build box 15 in a subsequent cycle.

[0045] In the next cycle, when the secondary box 3' is arranged above the build box 15, the sliding base 17 of the build box 15 is raised again to the next specified height, thereby pushing a certain portion of the residual contents of the build box 15 into the secondary box 3'. This is followed by a division of the contents by means of the dividing plate 20 as described above, transfer of the secondary box 3' above the fluidising segment 5', followed again by the basic fluidisation and depowdering process.

[0046] Optionally, two or more secondary boxes 3' may be used which cyclically receive a portion of the contents of the build box 15, allowing certain steps of the process to be paralleled, such as simultaneously raising the contents of the build box 15 into the secondary box 3' and performing the basic fluidisation and depowdering process above the fluidising segment 5'. Immediately after the secondary box 3' has been transferred above the build box 15 above the fluidising segment 5', an additional secondary box 3' may be placed above the build box 15 to receive at least a portion of the remaining contents of the build box 15. Optionally, several fluidising segments 5' may be used, above which individual secondary boxes 3' with their contents are transferred, allowing simultaneous fluidisation and depowdering of different portions of the contents, and thus faster overall depowdering of the contents of the build box 15. Optionally, several dividing plates 20 may also be used to allow the processes described above to be carried out in parallel.

[0047] The described movements of the secondary box 3' are carried out by sliding means of the secondary box 3' in known ways. In one of the embodiments, the sliding means of the secondary box 3' and the sliding means of the dividing plate 20 are integrated.

[0048] The correct positioning of the secondary box 3' after it has been moved above the fluidising segment 5' or the build box 15 is carried out in known ways, e.g. by insertion into grooves or on attachments located on the surface in the chamber 2 or on the build box 15, on which the secondary box 3' is currently to be positioned.

[0049] The fluidisation and depowdering process according to the second illustrated embodiment comprises the following pre-steps:

[0050] 1. Positioning of the secondary box 3' and / or the build box 15 so that the secondary box 3' is located above the build box 15.

[0051] 2. The sliding base 17 of the build box 15 is raised to a certain height by means of the vertical sliding means 16, whereby a certain portion of the contents, with at least one horizontal layer of pre-sintered articles 8, is moved from the build box 15 upwards into the secondary box 3'. The sliding height is determined in such a way that in the plane along which the dividing plate 20 is to be inserted there are no pre-sintered articles 8 which could get damaged by the insertion of the dividing plate 20 or which could prevent the insertion of the dividing plate 20.

[0052] 3. The dividing plate 20 is inserted between the contents that remain in the build box 15 and the contents displaced into the secondary box 3' into the dedicated dividing slot 21.

[0053] 4. The secondary box 3', together with the dividing plate 20 forming the temporary base of the secondary box 3', is moved above the fluidising segment 5' in the chamber 2.

[0054] 5. The dividing plate 20 withdraws from beneath the secondary box 3' and preferably returns to its initial position to allow further separation of at least portion of the contents remaining in the build box 15 and await the re-execution of pre-step 3 in the next cycle, whereby the depowdering device is formed.

[0055] If the outlet openings 6 are not provided as through openings in the fluidising segment 5', the outlet openings 6 are formed during or after pre-step 4 or in pre-step 5. In one embodiment, the outlet opening 6 is provided in the form of a slot around most of the circumference by offsetting the dividing plate 20 from beneath the secondary box 3'. In this case, the height of the slot is substantially equal to the thickness of the dividing plate 20. Optionally, the outlet openings 6 may be formed, reduced or enlarged by raising or lowering the secondary box 3' or the fluidising segment 5', respectively.

[0056] The basic fluidisation and depowdering process is then carried out following the basic steps a. to c. After the completion of the basic fluidisation and depowdering process, the secondary box 3' withdraws from the fluidising segment 5' and moves above the build box 15, leaving the pre-sintered articles 8 remaining on the fluidising segment 5' accessible for further use.

[0057] The fluidisation and depowdering process is carried out in cycles until the build box 15 is emptied or all the pre-sintered articles 8 have been separated from the powder material 7, whereby pre-step 2 of the next cycle is preferably carried out immediately after the secondary box 3' has been moved above the build box 15.

[0058] If more than one secondary box 3' is available, the next cycle's pre-step 2 can be carried out at any time after the current cycle's pre-step 4 has been performed, i.e. when there is a clear space above the build box 15 to arrange a further secondary box 3'.

[0059] The advantage of the second illustrated embodiment is that it allows for the depowdering of individual horizontal layers of pre-sintered articles 8, which further prevents possible damage to the pre-sintered articles 8 during the depowdering process itself. This allows printing of a larger number of horizontal layers of pre-sintered articles 8 in the build box 15 without the pre-sintered articles 8 being damaged in the depowdering process due to the stacking of the pre-sintered articles 8 from one horizontal layer on top of the pre-sintered articles 8 from the lower horizontal layers. For example, a further advantage with respect to the first illustrated embodiment is that there is no need to modify the build box 15. THIRD ILLUSTRATED EMBODIMENT

[0060] In the third illustrated embodiment (Figure 4), the depowdering box 3 is configured as a combination of a build box 15 and a cover fluidising bed 5" which, in the active position, forms the fluidising bed 5 of the depowdering box 3, wherein the build box 15 is connected to turning means 22 for positioning the build box 15 from the initial position to the active position in which the basic fluidisation and depowdering process is carried out.

[0061] The build box 15 is in the same orientation both in the initial position and during 3D printing. By means of the turning means 22, the build box 15 is turned about a substantially horizontal axis from the initial position to the active position by a rotation angle of at least 90 degrees, preferably 180 degrees. The side walls 4 of the depowdering box 3 are configured as side walls 19 of the build box 15 facing the active position. In some embodiments, the final rotation angle of 180 degrees is increased or decreased by 10 to 20 degrees to facilitate or direct the outflow of the powder material 7 through the outlet openings 6.

[0062] The turning means 22 are configured as a support 23 of the build box 15 with a turning mechanism 24, the support 23 allowing the build box 15 to be connected to the turning means 22, and the turning mechanism 24, e.g. a motor with a shaft, allowing the support 23 to rotate in a controlled manner. When connected to the turning means 22, the build box 15 is in the initial position and the turning means 22 allow the build box 15 to be turned from the initial position to the active position and vice versa.

[0063] The fluidising bed 5 is configured as the cover fluidising bed 5". Before the build box 15 is turned to the active position, preferably in the start position, the cover fluidising bed 5" is positioned over the top opening 18 of the build box 15 and secured with respect to the build box 15. When the cover fluidising bed 5" is positioned over the top opening 18 of the build box 15, the permeable faces 13 of the fluidising elements 9 in the cover fluidising bed 5" are oriented towards the contents of the build box 15.

[0064] In the case that the build box 15 comprises a sliding base 17, i.e. when the base 17 of the build box 15 is connected to the vertical sliding means 16, these and / or the sliding base 17 are optionally secured to the turning means 22 prior to the basic fluidisation and depowdering process by means of fastening means, in order to prevent unwanted lowering of the sliding base 17 during the basic fluidisation and depowdering process, thereby preventing possible damage to the pre-sintered articles 8.

[0065] Once the build box 15 is connected to the turning means 22 in the chamber 2 via the support 23, the cover fluidising bed 5" is then positioned over the top opening 18 of the build box 15 and secured with respect to the build box 15. The build box 15 is then turned from the initial position to the active position. In the active position, the cover fluidising bed 5" is located below the build box 15, wherein the contents of the build box 15 come in contact with the permeable face 13 of the fluidising elements 9 of the cover fluidising bed 5".

[0066] As shown in Figure 4, the outlet openings 6 are provided between the edges of the side walls 19 of the build box 15 and the surface of the cover fluidising bed 5" facing the contents of the build box 15. The outlet openings 6 may be formed during the step of positioning the cover fluidising bed 5" over the build box 15 or may be formed after the build box 15 has been turned to the active position, but in any case, before the basic fluidisation and depowdering process has been carried out. The outlet openings 6 are preferably provided in the form of a slot with a gap between the surface of the cover fluidising bed 5" facing the contents of the build box 15 and the edge of the side walls 19 of the build box 15 in the active position.

[0067] The fastening of the cover fluidising bed 5" with respect to the build box 15 may be made by means of fasteners, e.g. screws, wherein the size of an outlet opening 6 is adjusted, e.g. by tightening or loosening the screws. It is also possible to use automatic grippers, such as pneumatic, electric or hydraulic cylinders, mechanical locks, etc., where the outlet opening 6 is provided, for example, by means of mechanical spacers. The automatic grippers may also allow lowering the cover fluidising bed 5" on which the pre-sintered articles 8 are located after the basic fluidisation and depowdering process has been completed, thus allowing access to and removal of the pre-sintered articles 8. If the presintered articles 8 were to remain on the cover fluidising base 5" when the build box 15 is turned back to its original position, they could be damaged.

[0068] The chamber 2 is provided with a collector 14 for the powder material 7 that is located below the outlet openings 6 when the depowdering box 3 is in the active position.

[0069] Once the build box 15 is in the active position the basic fluidisation and depowdering process is carried out. After the basic fluidisation and depowdering process has completed, the pre-sintered articles 8 remain on the cover fluidising bed 5".

[0070] Of course, the build box 15 must be moved to the chamber 2 before the fluidisation process. This is carried out in known ways by manipulation means.

[0071] The fluidisation and depowdering process according to the third illustrated embodiment comprises the following pre-steps:

[0072] 1. Placing the build box 15 with the contents into the chamber 2 in the initial position, i.e. fixing to the turning means 22.

[0073] 2. Placing the cover fluidising bed 5" over the top opening 18 of the build box 15 and securing with respect to the build box 15 such that the permeable faces 13 of the fluidising elements 9 in the cover fluidising bed 5" are oriented towards the contents of the build box 15.

[0074] 3. The build box 15 together with the secured cover fluidising bed 5” is turned to the active position so that the cover fluidising bed 5" is located below the build box 15, wherein the contents of the build box 15 come in contact with the permeable face 13 of the fluidising elements 9 of the cover fluidising bed 5", whereby the depowdering device is formed.

[0075] The outlet openings 6 are preferably provided in the form of a gap between the top surface of the cover fluidising bed 5" and the bottom edge of the side walls 19 of the build box 15 with respect to the active position of the build box 15. The outlet openings 6 may be formed at the same time as pre-step 2 or after pre-step 3. The advantage of forming the outlet openings 6 after pre-step 3 is that the contents are prevented from leaking in pre-step 3, i.e. when the build box 15 is turned from the initial position to the active position.

[0076] The basic fluidisation and depowdering process is then carried out following the basic steps a. to c. After the basic fluidisation and depowdering process has been carried out, the pre-sintered articles 8 are removed from the cover fluidising bed 5" and the build box 15 is return to its original position.

[0077] For example, the advantage of this illustrated embodiment with respect to the first illustrated embodiment is that there is no need to modify the build box 15. FOURTH ILLUSTRATED EMBODIMENT

[0078] In the fourth illustrated embodiment (Figure 5), the depowdering box 3 is configured as a build box 15 such that the side walls 19 of the build box 15 form the side walls 4 of the depowdering box 3 and the fluidising bed 5 of the depowdering box 3 is substantially configured as a base 17 of the build box 15 with the fluidising elements 9.

[0079] The outlet openings 6 are provided in the side walls 19 of the build box 15 just above the top surface of the fluidising bed 5 or are provided in the form of an outlet gap between the top surface of the fluidising bed 5 and the bottom edge of the side walls 19 of the build box 15. The outlet openings 6 are provided with means 25 for the controlled opening and closing of the outlet openings 6, e.g. flap, plug, covers, valves, etc. The controlled opening and closing of outlet openings 6 can be done manually, e.g. by removing a plug or opening a flap, or automatically, e.g. by using electromagnetic, pneumatic, hydraulic valves. The outlet openings 6 can also be opened during the positioning of the build box 15 in the chamber 2, e.g. by means of a lifting lever, which ensures that the outlet opening 6 is already open during the positioning of the build box 15 into the chamber 2.

[0080] The chamber 2 is provided with a collector 14 for the powder material 7 that is located below the outlet openings 6.

[0081] During 3D printing, or before the build box 15 is positioned into the chamber 2, the outlets 6 of the build box 15 are closed. After 3D printing is completed, the build box 15, with the contents and the closed outlet openings 6, is transferred into the chamber 2 by means of manipulation means. Before the basic fluidisation and depowdering process is carried out, the outlet openings 6 must be opened to allow the powder material 7 to drain.

[0082] The fluidisation and depowdering process according to the fourth illustrated embodiment comprises the following pre-steps:

[0083] 1. Positioning the build box 15, with the contents and the closed outlet openings 6, into the chamber 2.

[0084] 2. Opening the outlet openings 6, whereby the depowdering device is formed.

[0085] The basic fluidisation and depowdering process is then carried out following the basic steps a. to c.

[0086] The advantage of the fourth illustrated embodiment is its simplicity and robustness, as there is no need for additional manipulation means or special mechanisms. This also makes the whole process easy.

Claims

CLAIMS1. A device (1) for depowdering pre-sintered articles (8) fabricated by the selective binder jetting method, wherein the pre-sintered articles (8) are manufactured in a build box (15) using 3D printing technology comprising selective binder jetting onto a powder material (7), characterized by comprising a depowdering box (3) located in a chamber(2) under inert or natural atmosphere, the depowdering box (3) comprising a fluidising bed (5), side walls (4) and at least one outlet opening (6), wherein the fluidising bed(5) comprises at least one fluidising element (9) connected to a source (10) of compressed gas over all or part of its upper surface, wherein at least one outlet opening (6) is provided in the fluidisation zone (11), either in the side walls (4) adjacent to the fluidising bed (5) and / or between the upper surface of the fluidising bed (5) and the side walls (4), around all or part of the circumference, and / or through the fluidising bed (5), wherein the size of the outlet openings (6) is such as to pass the powder material (7) as unobstructed as possible, but not to pass the pre-sintered articles (8).

2. The device (1) for depowdering according to claim 1 , characterized by comprising a collector (14) for the powder material (7), which is located below the outlet openings(6), wherein, during depowdering, the powder material (7) falls by gravity through the outlet openings (6) into the collector (14).

3. The depowdering device (1) according to claims 1 or 2, characterized in that the fluidising element (9) is configured as a fluidising plate.

4. The depowdering device (1) according to claims 1 or 2, characterized in that the depowdering box (3) is configured as a combination of a secondary box (3') under which a build box (15) is arranged, wherein the side walls (4) of the depowdering box(3) substantially form the side walls (4') of the secondary box (3'), and a fluidising bed (5) substantially configured as a base (17) of the build box (15) with fluidising elements (9), wherein the base (17) of the build box is connected by vertical sliding means (16) that allow a controlled raising of the fluidising bed (5) and thus the pre-sintered articles (8) in the powder material (7) in the secondary box (3').

5. The depowdering device (1) according to claim 4, characterized in that the upper surface of the fluidising bed (5), after the pre-sintered articles (8) in the powdermaterial (7) have been raised from the build box (15) into the secondary box (3'), is located at the same height as, or above, the upper edge of side walls (19) of the build box (15), so that a step is not created between the outlet opening (6) and the fluidising bed (5), which would prevent the powder material (7) from flowing out through the outlet opening (6).

6. The depowdering device (1) according to claims 5 and 6, characterized in that the outlet openings (6) are provided in the side walls (4') of the secondary box (3') just above the top surface of the fluidising bed (5) after it has been raised or are provided in the form of a gap between the top edge of the side walls (19) of the build box (15) or between the top surface of the fluidising bed (5) and the bottom edge of the side walls (4') of the secondary box (3').

7. The depowdering device (1) according to claims 5 to 7, characterized in that the size of the outlet openings (6) is adjusted by raising or lowering the secondary box (3') relative to the fluidising bed (5), or by raising or lowering the fluidising bed (5) relative to the secondary box (3').

8. The depowdering device (1) according to claims 5 to 8, characterized in that the build box (15), when placed under the secondary box (3'), is located inside or below the chamber (2), wherein an airtight contact of the interior of the build box (15) with the chamber (2) is ensured.

9. The depowdering device (1) according to claims 1 or 2, characterized in that the depowdering box (3) is configured as a combination of a secondary box (3') adapted to receive at least one horizontal layer of pre-sintered articles (8) in the powder material (7) from the build box (15) arranged under the secondary box (3'), wherein the side walls (4) of the depowdering box (3) are substantially the side walls (4') of the secondary box (3'), and a fluidising segment (5') that forms the fluidising bed (5) of the depowdering box (3), wherein the fluidising segment (5') is arranged inside the chamber (2) separately from the build box (15), the build box (15) comprising a sliding base (17) to displace part of the contents of the build box (15) upwards to the secondary box (3'), the secondary box (3') being adapted to move above the build box (15) above the fluidising segment (5') and to be positioned above the fluidising segment (5'), wherein the device (1) comprises a dividing plate (20) adapted to dividepart of the contents of the build box (15) from the remaining contents of the build box (15) and to form a temporary base of the secondary box (3'), such that, after part of the contents of the build box (15) has been displaced upwards into the secondary box (3'), the dividing plate (20) is substantially horizontally inserted between the top of the build box (15) and the bottom edge of the secondary box (3') from its starting position in a dividing slot (21) provided for this purpose between the upper edge of the build box (15) and the bottom edge of the secondary box (3'), and once the secondary box (3') is displaced and arranged above the fluidising segment (5') in the chamber (2), the dividing plate (20) withdraws.

10. The depowdering device (1) according to claim 9, characterized in that the outlet openings (6) are provided in the side walls (4') of the secondary box (3') just above the top surface of the fluidising segment (5') or are provided in the form of a gap between the top edge of the fluidising segment (5') and the bottom edge of the side walls (4') of the secondary box (3').

11. The depowdering device (1) according to claim 9, characterized in that mere sliding of the dividing plate (20) creates an outlet opening (6), the height of which is substantially equal to the thickness of the dividing plate (20).

12. The depowdering device (1) according to claim 9, characterized in that the outlet openings (6) are configured as through openings in the fluidising segment (5').

13. The depowdering device (1) according to claims 1 or 2, characterized in that the depowdering box (3) is configured as a combination of the build box (15) and a cover fluidising bed (5") which in the active position forms the fluidising bed (5) of the depowdering box (3), and the cover fluidising bed (5") is arranged over a top opening (18) of the build box (15) and secured with fastening means to the build box (15) such that the permeable faces (13) of the fluidising elements (9) in the cover fluidising bed (5") are oriented towards the contents of the build box (15), wherein the build box (15) is connected with turning means (22) adapted to turn the build box (15) about a substantially horizontal axis by a rotation angle of at least 90 degrees and to displace the build box (15) from the initial position to the active position, wherein the initial position of the build box (15) is the position during 3D printing, while the active position of the build box (15) is the position during depowdering, the side walls (4) of the depowdering box (3) being provided as side walls (19) of the build box (15) facing theactive position.

14. The depowdering device (1) according to claim 13, characterized in that the build box (15) is turned about a substantially horizontal axis from the initial position to the active position by 180 degrees.

15. The depowdering device (1) according to claims 13 and 14, characterized in that the turning means (22) are configured as a support (23) with a turning mechanism (24), wherein the build box (15) is connected with the turning means (22) via the support (23) and the turning mechanism (24) is adapted for a controlled rotation of the support (23), wherewith the turning of the build box (15) from the initial position to the active position and vice versa is enabled.

16. The depowdering device (1) according to claims 13 to 15, characterized in that, if the build box (15) is provided with the sliding base (17), the device (1) further comprises fastening means for fastening the sliding base (17), which prevents an undesired lowering of the sliding base (17) during depowdering.

17. The depowdering device (1) according to claims 13 to 16, characterized in that the outlet openings (6 ) are provided in the form of a slot with a gap between the edge of the side walls (19) of the build box (15) and the surface of the cover fluidising bed (5") facing the contents of the build box (15), wherein the height of the slot is adequately adapted during the positioning of the cover fluidising bed (5") over the build box (15) or after the build box (15) has been turned to the active position.

18. The depowdering device (1) according to claims 1 or 2, characterized in that the depowdering box (3) is configured as a build box (15) such that the side walls (19) of the build box (15) form the side walls (4) of the depowdering box (3) and the fluidising bed (5) of the depowdering box (3) is substantially configured as a base (17) of the build box (15) with the fluidising elements (9), the outlet openings (6) being provided with means (25) for the controlled opening and closing of the outlet openings (6).

19. The depowdering device (1) according to claim 18, characterized in that the outlet openings (6) are provided in the side walls (19) of the build box (15) just above the top surface of the fluidising bed (5) or are provided in the form of a gap between the top surface of the fluidising bed (5) and the bottom edge of the side walls (19) of the buildbox (15).

20. The depowdering device (1) according to claims 18 or 19, characterized in that the outlet openings (6) are closed prior to the build box (15) is placed into the chamber (2) and the outlet openings (6) are open after the build box (15) has been transferred into the chamber (2) and before depowdering in order to enable drainage of the powder material (7).

21. Depowdering process using the depowdering device (1) according to any of claims 1 to 20, characterized by including the basic fluidisation and depowdering process that comprises the following steps: d) blowing compressed gas through at least one fluidising element (9) of the depowdering box (3) with the contents including the pre-sintered articles (8) and the powder material (7), wherein fluidisation of the powdered material (7) is initiated in the fluidisation zone (11) and the powder material (7) flows, inter alia, by gravity through at least one outlet opening (6), wherein the fluidisation zone (11) extends into the interior of the depowdering box (3) approximately 2-3 cm upstream of the fluidising element (9); e) gradual downward movement of the upper layers of the powder material (7) by gravity into the fluidisation zone (11); f) fluidising for a sufficient time that all or most of the powder material (7) is drained from the depowdering box (3), leaving the pre-sintered articles (8) on the fluidising bed (5) of the depowdering box (3).

22. The process according to claim 21, characterized in that the process includes the following pre-steps:1.) positioning of the build box (15) and / or the secondary box (3') so that the build box (15) is located below the secondary box (3') located in the chamber (2), ensuring an air-tight contact of the interior of the build box (15) with the chamber (2);2.) raising the base (17) of the build box (15) with the fluidising elements (9), which is also the fluidising bed (5) of the depowdering box (3) or secondary box (3'), by means of the vertical sliding means (16) to the top of the side walls (19) of the build box (15) in order to move the contents from the build box (15) upwards into the secondary box (3'), whereby the depowdering device (1) according to claims 4 to 8 is formed.

23. The process according to claim 22, characterized in that at least one outlet opening (6) is provided between the top edge of the side walls (19) of the build box (15) or between the fluidising bed (5) and the bottom edge of the side walls (4') of the secondary box (3'), the outlet openings (6) being formed at the same time as pre-step 2 or after pre-step 2.

24. The process according to claim 21, characterized in that the process includes the following pre-steps:1.) positioning the secondary box (3') and / or the build box (15) so that the secondary box (3') is located above the build box (15);2.) raising the sliding base (17) of the build box (15) to a certain height by means of the vertical sliding means (16), whereby a certain portion of the contents including at least one horizontal layer of pre-sintered articles (8) is moved from the build box (15) upwards into the secondary box (3'), the sliding height being determined in such a way that in the plane along which the dividing plate (20) is to be inserted there are no pre-sintered articles (8);3.) inserting the dividing plate (20) between the contents that remain in the build box (15) and the contents displaced into the secondary box (3') into the dedicated dividing slot (21);4.) displacing the secondary box (3') together with the dividing plate (20) forming the temporary base of the secondary box (3') above the fluidising segment (5') in the chamber (2);5.) withdrawing the dividing plate (20) from beneath the secondary box (3') and in its initial position where it awaits the re-execution of pre-step 3 in the next cycle, whereby the depowdering device (1) according to claims 9 to 12 is formed.

25. The process according to claim 24, characterized in that the outlet openings (6) are formed during or after pre-step 4 or in pre-step 5.

26. The process according to claim 24, characterized in that the outlet opening (6) is provided in the form of a slot around most of the circumference by offsetting the dividing plate (20) from beneath the secondary box (3').

27. The process according to claims 25 or 26, characterized in that the outlet openings (6) can be reduced or enlarged by raising or lowering the secondary box (3') or thefluidising segment (5'), respectively.

28. The process according to claims 23 to 27, characterized in that after the completion of the basic fluidisation and depowdering process, the secondary box (3') withdraws from the fluidising segment (5') and moves above the build box (15).

29. The process according to claims 23 to 28, characterized by being carried out in cycles until the build box (15) is emptied, whereby pre-step 2 of the next cycle is preferably carried out immediately after the secondary box (3') has been moved above the build box (15).

30. The process according to claim 21, characterized in that the process includes the following pre-steps:1.) placing the build box (15) with the contents into the chamber (2) in the initial position, i.e. fixing to the turning means (22);2.) placing the cover fluidising bed (5") over the top opening (18) of the build box (15) and securing to the build box (15) such that the permeable faces (13) of the fluidising elements (9) in the cover fluidising bed (5") are oriented towards the contents of the build box (15);3.) turning the build box (15) together with the secured cover fluidising bed (5") to the active position so that the cover fluidising bed (5") is located below the build box (15), wherein the contents of the build box (15) come in contact with the permeable face (13) of the fluidising elements (9) of the cover fluidising bed (5"), whereby the depowdering device (1) according to claims 13 to 17 is formed.

31. The process according to claim 30, characterized in that the outlet openings (6) are formed during the step of positioning the cover fluidising bed (5") over the build box (15) or are formed after the build box (15) has been turned to the active position.

32. The process according to claim 21, characterized in that the process includes the following pre-steps:1.) positioning the build box (15), with the contents and the closed outlet openings (6), into the chamber (2);2.) opening the outlet openings (6), whereby the depowdering device (1) according to claims 18 to 20 is formed.

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