DE102021207771A1 - Method and device for joining green 3D printed components - Google Patents

Abstract

The invention relates to a method and a device (10) for joining green 3D printed components (20, 22). A method for joining green 3D printed components (20, 22) is provided. Two 3D printed component green parts (20, 22), which are made from the same starting materials, are aligned with one another, so that the respective connecting surfaces (24, 26) are essentially aligned opposite one another. An intermediate layer of abraded material is created by means of pressure and vibrations, which is then used for a sintered joining process.

Description

The invention relates to a method and a device for joining green 3D printed component parts.

Components, for example in the automotive industry, are increasingly being manufactured using so-called 3D printing processes such as the binder jetting process. The processing of powdered starting materials in combination with other starting materials, such as the appropriate binder, is already well known.

Methods are known in which the components have to be removed from a powder bed after the printing process in order to feed them to further processing steps. Today, this removal is often still done manually, with fragile components in particular being at risk because they are not yet sufficiently strong immediately after the printing process. This strength is only achieved later, for example during the so-called sintering process.

Before that, the freshly printed components have to be de-powdered. The removal of powder residues, in particular from internal structures of the component such as channels or the like, is still a challenge. Due to the fragility of the components in this state, the respective previously known technical possibilities are limited in their application. Since the excess powdery material is slightly compacted after the printing process itself and partly sticks to one another due to the curing process step, this powdery material is poorly flowable, especially in internal structures, and cannot simply trickle out.

For straight cavities in printed components, for example in the form of blind holes, appropriate compressed air lances can sometimes be used for powder removal. In the case of more complex, curved geometries, however, such depowdering measures using compressed air do not work, since the maximum usable pressure of the compressed air that can be used without damaging the component is not sufficient to release the trapped powdery material. A further increase in the pressure of the compressed air only leads to powdery material being released from printed component areas, which thus leads to irreversible damage to these areas or, in general, to the component. In addition, whirled up powdery material or powder in the channels can be accelerated by the compressed air onto the component areas, which accelerates the abrasive detachment of component material. It is therefore currently not readily possible to produce components with complex internal structures using the binder jetting method or generally by means of a 3D printing method, which in particular uses powdered materials.

Binder jetting processes are new additive manufacturing processes that are suitable, for example, for the production of metal components. Here, metallic starting powders are bonded in layers in component molds using suitable binders. The layers are applied by a round roller device, for example, which rotates on the one hand and performs a translational movement on the other in order to apply powdered material over the entire construction platform. A print head then applies a suitable binder. The resulting component is also referred to as a green part or green part and has limited strength, since it is initially only held together by the applied binder. Before the components prefabricated in this way can be removed from the powder bed, the binder must be thermally activated and hardened. This process is also known as the curing process. The binder is then burned out in a sintering process, for example in the form of a so-called sintering run, and the powder particles are sintered together to form their final component until the highest possible density is achieved.

In this context, production methods are already known which are conditionally suitable for producing fragile channel courses in printed components in such a way that a channel course that is as powder-free as possible can then be provided. For this purpose, chain-shaped objects are printed directly along the course of the channel, which are then subsequently pulled out again. During this process, loose powder residues are partially carried out with it. However, this method is unsuitable for variable channel cross sections. In addition, these chain-like objects are also fragile and can easily tear during this process, again making it difficult, if not impossible, to remove a broken chain-like object.

Another approach pursued today is to manufacture fragile components in several individual parts and then to bring them together. In ceramic construction, the first approaches are already known. Examples from the prior art are presented in more detail below.

That's from the pamphlet EP 1 816 112 A2 a method of forming a ceramic-to-ceramic connection as known. In particular, a method of joining at least two sintered bodies to form a composite structure is disclosed. The method includes the steps of: providing a bonding material between bonding surfaces of the first and second sintered bodies; applying a pressure from 1 kPa to less than 5 MPa to provide an assembly; heating the assembly to a conforming temperature sufficient to allow the bonding material to conform to the bonding surfaces; and further heating the assembly to a bonding temperature below a minimum sintering temperature of the first and second sintered bodies. The connecting material includes (an) organic component(s) and ceramic particles. The ceramic particles make up 40-75% by volume of the bonding material and comprise at least one element of the first and/or second sintered body. Composite structures made by the method are also disclosed.

From the pamphlet DE 10 2011 089 260 A1 a method for producing a component by metal powder injection molding can also be seen as known. In particular, a method for producing a component by metal powder injection molding of metal powder mixed with a binder is disclosed, in which the individual components of the component are manufactured as separately formed green compacts and subsequently debound brown compact sections, which are assembled into a two-part or multi-part brown compact and sintered in the assembled state will. The brown compact sections shrink during the sintering process. It is provided that at least one of the brown compact sections to be connected goes through a pre-sintering process in which it experiences a first shrinkage, the at least one pre-sintered brown compact section and at least one further brown compact section are assembled into a two-part or multi-part brown compact, and the two-part or multi-part The brown compact then goes through a main sintering process, with the at least one pre-sintered brown compact section experiencing less shrinkage during the main sintering process than the at least one further brown compact section, as a result of which the at least one pre-sintered brown compact section and the at least one further brown compact section are firmly connected to one another.

In addition to the examples presented from the prior art, the first technical approaches are already known which deal with the possibility of essentially direct sinter joining. This method, which has not been extensively investigated and developed up to now, still has shortcomings in terms of the resulting strength, so that there is a certain need for new solution concepts. In particular, cost-effective processes that produce a strength of the resulting components that can be rated as sufficient are desirable.

The invention is now based on the object of producing a method for joining green 3D printed component parts which at least partially overcomes the disadvantages mentioned.

In a preferred embodiment of the invention, it is provided that a method for joining green 3D printed component parts is provided. Such a method comprises the following steps: providing two 3D printed component green parts, which are made from the same starting materials; Aligning the two green 3D printed parts with each other such that respective mating surfaces are substantially oppositely aligned.

In this embodiment, the method also comprises the following additional method steps: pressing the two green 3D printed components together and moving the green 3D printed components combined against one another, so that the respective connecting surfaces are rubbed against one another; using abraded materials from the respective bonding surfaces of the two green 3D printed parts to create a sintered bond of the two green 3D printed parts; Carrying out at least one sintering process, so that the two 3D printed component green bodies are connected to one another by means of at least one sinter joining process.

In this way, it is possible to produce a method for joining green 3D printed component parts that at least partially overcomes the aforementioned disadvantages.

The combined pressing of the components with a mutual movement means that the joining material is made available directly at the points where it is needed for the subsequent joining process. In addition, disturbing roughness peaks, which can be present locally on the connecting surfaces of the two 3D printed component green parts, are removed by this combination of pressure and friction. The abraded material is then used to create the sintered joint. Portions thereof can also be provided in the joining zone to bridge unwanted free spaces or gaps or the like. The combined process steps also ensure that this abraded material is reliably attached to the subsequent Sinter joining favorable position is moved or generally moved.

The combined pressing in connection with the movement against each other can be coordinated, for example, so that a certain intermediate layer height is achieved in a targeted manner. In other words, the process of rubbing the respective connecting surfaces together to create an intermediate layer is influenced in a targeted manner by means of the compression and its expression, so that a defined amount of rubbed-off material occurs.

Since the local roughness peaks are then removed and a defined amount of joining material is provided in the form of the abraded material, it is possible to achieve an optimal result in the subsequent sinter joining process, so that a strong and reliable connection of the 3D printed components is produced. The green compacts are thus not only sintered in the sintering process, but also connected to one another at the same time, with a specific and defined pretreatment of the connection surfaces being carried out due to the previous preparation steps within the presented method. Using the method presented, it is thus possible to produce components in two parts, with the sintering process inherent in the process being used to join the components.

In a further preferred embodiment of the invention, it is provided that a device for joining green 3D printed component parts is provided. Such an apparatus is adapted to practice the method according to any one of claims 1-9. The aforementioned advantages also apply to the device presented, insofar as they can be transferred.

Further preferred configurations of the invention result from the remaining features mentioned in the dependent claims.

In a further preferred embodiment of the invention, it is provided that the green 3D printed component parts are the result of a binder jet printing process, in particular a binder jet printing process for the production of metal components.

The method presented can be used to advantage for the 3D printed component green bodies mentioned, since it can be seamlessly integrated into the specified manufacturing process. 3D printed component green bodies, which are the result of a binder jetting printing process, are usually finally treated in a sintering process, so that the process sequence can be easily expanded here according to the method presented in order to produce corresponding composites or assembled 3D printed components. The method has proven to be particularly advantageous for the production of metal components, since the connecting surfaces made of the appropriate mix of starting materials are particularly suitable for carrying out the combination of pressurization and friction for the desired result. It is thus possible to produce binder jet components with complex inner structures without powder and to connect them tightly and mechanically stable in the sinter joining process. There is therefore no need for complex joint seam geometries, which, for example, lead to initial strength through a geometry that matches one another. Also, no additional sintered solder, such as a special brazing paste, is required. In addition, the method presented can thus be advantageously integrated into the operating sequence that is intended anyway, since the final sintering process would be necessary in any case in order to produce the final components. It is also conceivable that other components can also be added in this way, for example to produce particularly large components. For this purpose, the method presented is used more often, so that the respective components are connected to one another.

In a further preferred embodiment of the invention, it is also provided that the two green 3D printed component parts are pressed together with a contact pressure of 1000 kPa to 10 MPa. The aforementioned advantages lead to particularly good results within this interval, with a respective adaptation to particularly pronounced connecting surfaces being conceivable.

In addition, in a further preferred embodiment of the invention, it is provided that the 3D printed component green compacts are moved towards one another by means of at least one vibration device. A particularly gentle mutual movement can be achieved by means of such a vibration device, so that the risk of damage to the green 3D printed component can be minimized. Although it is possible in this way to adequately compensate for local roughness peaks or the like, with the abraded material being used in an optimal quantity for an advantageous subsequent sintered joint.

Furthermore, in a further preferred embodiment of the invention, it is provided that a vibration frequency of the at least one vibration device is set in a user-defined manner. Depending on the vibration frequency and the pressing force of the components against each other, a different intermediate layer height can be created. It is thus it is even better possible to carry out the procedure of rubbing against one another to produce an intermediate layer in order to produce a very good sintered joint.

Furthermore, in a further preferred embodiment of the invention, it is provided that vibrations of the at least one vibration device are essentially introduced into respective edge regions of the green 3D printed component. In particular, those areas are to be regarded as edge areas which correspondingly delimit the respective component to the outside. An introduction of the vibrations in the relative vicinity of the respective connecting surfaces or even just one connecting surface is conceivable. However, it is also conceivable that the vibrations are introduced at an edge region of an external geometry of the component that is spaced apart from the respective connecting surface, so that the movement impulses required for the abrasion of the production material then affect the location of the event, i.e. the mutual movement of the connecting surfaces, through the component reach through. In this way, it is possible to obtain edge layer powder or abraded material in these areas from the components to produce an intermediate powder layer by abrasion processes due to pressure and vibrations.

Another preferred embodiment of the invention also provides for additional external material to be provided between the connecting surfaces of the two green 3D printed components, which is used to produce a sintered joint between the two green 3D printed components.

Such additional external material can be applied to the connecting surfaces, for example by means of a squeegee device, so that a sufficiently dense and mechanically stable joint is produced in the actual joining step during sintering. If, due to the properties of the green compacts, the abraded materials are to be assessed as insufficient in advance, this can help in this way. Such an additional external material is also advantageous because it promotes the abrasion of local roughness peaks, so that a particularly good joint is achieved. In addition, parts of the additional external material are introduced into porous openings, so that an additional advantageous preparation step for the subsequent sintering is achieved here.

Furthermore, in a further preferred embodiment of the invention, it is provided that the additional external material comprises the starting materials of the green 3D printed component.

For example, it is conceivable that the additional external material consists exclusively of the starting materials of the green 3D printed component in the same mixing ratio.

The joining result to be achieved can be achieved particularly advantageously in this way.

Finally, another preferred embodiment of the invention provides that the additional external material comprises the starting materials of the green 3D printed component, with an average powder particle size of the additional external material being smaller than an average powder particle size of the starting materials of the green 3D printed component. The aforementioned advantages can thus be achieved even better.

The method presented can be used, for example, for all binder jetting geometries with slightly complex internal hollow structures. The process presented can be used in any manufacturing branch of technology in which binder jetting is used accordingly.

Unless stated otherwise in the individual case, the various embodiments of the invention mentioned in this application can advantageously be combined with one another.

• 1 schematisch ein Ablaufdiagramm eines Verfahrens zum Fügen von 3D-Druckbauteil-Grünlingen;
• 2 schematisch eine Vorrichtung zum Fügen von 3D-Druckbauteil-Grünlingen;
• 3 schematisch eine grafische Darstellung eines Sinterfügeverfahrens gemäß dem Stand der Technik;
• 4 schematisch eine grafische Darstellung eines Sinterfügeverfahrens unter Einbeziehung des vorgestellten Verfahrens zum Fügen von 3D-Druckbauteil-Grünlingen.

The invention is explained below in exemplary embodiments with reference to the associated drawings. Show it:

• 1 schematically a flowchart of a method for joining 3D printed component green parts;
• 2 schematically a device for joining 3D printed component green parts;
• 3 schematically a graphical representation of a sinter joining method according to the prior art;
• 4 schematically a graphic representation of a sinter joining process including the presented method for joining 3D printed component green parts.

1 FIG. 1 schematically shows a flow chart 100 of a method for joining green 3D printed component parts. In a first method step 110, two 3D printed component green bodies are provided, which are made from the same starting materials. In a second method step 120, the two 3D printed component green bodies are aligned with one another, so that respective connecting surfaces are essentially aligned opposite one another. In a third method step 130 the two green 3D printing components are pressed together and the green 3D printing components are moved against each other in combination, so that the respective connecting surfaces are rubbed against each other. In a fourth method step 140, materials abraded from the respective connecting surfaces of the two green 3D printed components are used to produce a sintered joint connection of the two green 3D printed components. In a fifth method step 150, at least one sintering process is carried out, so that the two green 3D printed component parts are connected to one another by means of at least one sintered joining process.

2 shows schematically a device 10 for joining green 3D printed component parts. The apparatus 10 is adapted to practice the method according to any one of claims 1-9.

3 shows a schematic representation of a sinter joining method according to the prior art. In relation to the image plane, a sequence of individual snapshots 12, 14, 16, 18 during the course of the method is shown schematically, the block arrows 19 shown clarifying the course of the method. In the first snapshot 12, two 3D printed component green bodies 20, 22 are shown, with respective connecting surfaces 24, 26 of the respective 3D printed component green bodies 20, 22 being aligned with one another. Local roughness peaks 28 are shown on both connecting surfaces 24, 26. These local roughness peaks 28 result in poor initial contact when the two 3D printed component green bodies 20, 22 are moved towards one another in accordance with the directional arrow 30 shown, so that the two connecting surfaces 24, 26 come into contact. In the third snapshot 16, the sintering process of this assembly group consisting of the two 3D printed component green parts 20, 22 is shown. Even during and after the sintering process, the poor initial contact, which occurs due to the existing roughness, cannot be compensated for, resulting in a poor joining result. This poor joining result is shown in the fourth snapshot 18, with the gaps 32 that appear being shown schematically. A real result is shown below the snapshots 12, 14, 16, 18 in the form of a photo section view 34, with an auxiliary scale of 100 μm being shown integrated, so that the dimensions of the gaps shown are made clearer.

4 shows a schematic representation of a sinter joining method including the presented method for joining green 3D printed components 20, 22. Again, the respective green 3D printed components 20, 22 are shown. The respective connecting surfaces 24, 26 of the respective 3D printed component green bodies 20, 22 are again shown aligned with one another. In a separate processing step 36, a force is introduced into the green 3D printed component parts 20, 22 lying against one another according to the force direction arrow 38 shown. It is conceivable that forces are introduced both from above and from below (relative to the image plane), so that the 3D printed component green bodies 20, 22 are pressed together. At the same time, vibrations are introduced into the 3D printed component green bodies 20, 22 by means of a vibration device that is not shown in detail. A vibration double arrow 40 that is shown illustrates this fact. In this way, the roughness peaks 28, which can also be called local asperites, are destroyed and an intermediate layer is formed from the abraded material. For example, this intermediate layer can consist of particles that have been detached from the edge areas. An intermediate powder layer is thus produced by abrasion of the 3D printed component green bodies 20, 22 by means of pressure and vibration. Then the sintering process takes place. The result is a very good joining result 42. The method presented can also be described as sinter joining with an intermediate layer produced by vibration abrasion from component edge areas.

Reference List

10

contraption

12

first snapshot

14

second snapshot

16

third snapshot

18

fourth snapshot

19

block arrow

20

first 3D printed component green part

22

second 3D printed component green body

24

first interface

26

second interface

28

roughness peak

30

directional arrow

32

gap

34

photo cut view

36

processing process step

38

force direction arrow

40

vibrating double arrow

42

joining result

100

process flow diagram

110

first step in the process

120

second process step

130

third step

140

fourth step

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1816112 A2 [0009]
• DE 102011089260 A1 [0010]

Claims (10)

Method for joining green 3D printed components (20, 22), comprising the following steps: • providing (110) two green 3D printed components (20, 22), which are made of the same starting materials; • Alignment (120) of the two 3D printed component green bodies (20, 22) to one another, so that respective connecting surfaces (24, 26) are aligned essentially opposite one another, characterized in that the method comprises the following further method steps: • Compressing (130) the two green 3D printed parts (20, 22) and combined movement of the green 3D printed parts (20, 22) towards each other so that the respective connecting surfaces (24, 26) are rubbed against each other; • Using (140) abraded materials from the respective connecting surfaces (24, 26) of the two green 3D printed components (20, 22) to produce a sintered joint connection of the two green 3D printed components (20, 22); • Carrying out (150) at least one sintering process, so that the two green 3D printed component parts (20, 22) are connected to one another by means of at least one sintered joining process. procedure after claim 1 , wherein the 3D printed component green bodies (20, 22) are the result of a binder jet printing process, in particular a binder jet printing process for the production of metal components. Method according to one of the preceding claims, wherein the pressing together of the two 3D printed component green bodies (20, 22) is carried out with a contact pressure of 1000 kPa to 10 MPa. Method according to one of the preceding claims, wherein the 3D printed component green compacts (20, 22) are moved towards one another by means of at least one vibration device. procedure after claim 4 , wherein a vibration frequency of the at least one vibration device is set in a user-defined manner. Procedure according to any of the previous ones Claims 4 until 5 , wherein vibrations of the at least one vibration device are introduced essentially into respective edge regions of the green 3D printed component (20, 22). Method according to one of the preceding claims, wherein external material is additionally provided between the connecting surfaces (24, 26) of the two 3D printed component green bodies (20, 22) which is used to produce a sintered joint of the two 3D printed component green bodies (20, 22 ) is used. procedure after claim 7 , wherein the additional external material comprises the raw materials of the 3D printed component green bodies (20, 22). Procedure according to any of the previous ones Claims 7 until 8th , wherein the additional external material comprises the starting materials of the green 3D printed parts (20, 22), wherein an average powder particle size of the additional external material is smaller than an average powder particle size of the starting materials of the green 3D printed parts (20, 22). Device (10) for joining 3D printed component green parts (20, 22), characterized in that the device (10) is designed, the method according to one of Claims 1 until 9 exercise.

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