DE102020117177A1 - Three-dimensional screen printing process, a component that can be manufactured with it and a screen printing mask - Google Patents

Abstract

The invention relates to a three-dimensional screen printing method for producing a green part (20) from printing material (11) for a powder-metallurgical component (30), the printing material (11) having a proportion of powder, in particular metal powder or ceramic powder, and binder or consisting of these materials , characterized in that the green part (20) is deformed after production at temperatures between 30 and 100 ° C.

Description

The present disclosure relates to a three-dimensional screen printing method with the features of claim 1, a component that can be produced therewith with the features of claim 17 and a screen printing mask with the features of claim 21.

The production of green parts by means of screen printing is known in principle. So describes the DE 10 2015 216 491 A1 the production of abradable seals by means of a three-dimensional screen printing as part of a powder metallurgical process. It is particularly about the production of a green part with hollow structures and vertical wall structures, such as honeycomb structures.

Abrasive seals in turbo machines, for example in aircraft or gas turbines, are subject to special requirements. If a rotor encounters a labyrinth seal, it should not lubricate, break or generate high temperatures when rubbed in, which would put stress on the rotating component.

The green part as the starting point of the powder metallurgical process is built up in layers by screen printing. Since the layers are comparatively thin, such a process is also known as a 2.5-D screen printing process.

In the case of screen printing, flat layers are used, so that after the layer-by-layer printing is completed, there is a green part with flat outer contours (e.g. in the form of a cuboid rubbing seal). Inside the green part, the vertical wall structures are arranged, e.g. in the form of honeycombs.

If such a green part is to be deformed e.g. by a curvature, cracks or defects in the green part can occur, since the walls of the green part and / or the vertical wall structures are deformed by the curvature. There is tension on the outer radius of the curve, which can lead to cracks. The material is compressed at the inner radius of the curvature.

There is therefore the task of specifying an efficient method for producing a green part - and thus a component.

According to a first aspect, a three-dimensional screen printing method having the features of claim 1 is provided.

The green part is produced by the three-dimensional screen printing process from printing material as part of a powder metallurgical process, the printing material having a portion of powder, in particular ceramic or metal powder, and binder or consisting of these materials. From the green part, a component is finally produced using the powder metallurgical process, which can be used as a liner in a gas turbine engine, for example.

A green part is produced from printing material for a powder-metallurgical component and the green part is deformed after production at temperatures between 30 and 100 ° C, since the component should also be designed to be correspondingly deformed. In particular, the temperature can be constant.

For efficient deformation, the deformation takes place by means of a molded part, the deformation time in particular being in the range between 1 and 30 seconds.

The deformation can take place around at least one axis of curvature. Depending on the position and number of the axes of curvature, more complex shaped green parts can be produced. In particular, the green part can be deformed around two axes. In particular, the green part can be deformed in such a way that a depression or a bulge is produced. In any case, the deformation in the green part - as described above - is absorbed by the wave-shaped structures.

Accordingly, a deformation can cause stretching and / or compression in the green part, which is compensated for at least by parts of the undulating structure of the green part by adjusting the wavelength.

In one embodiment, the undeformed green part is essentially cuboid (especially with regard to the outer shape) and the deformation of the green part comprises a bend around an axis of curvature, the axis of curvature lying in a plane that is parallel or inclined to a side surface of the green part.

In one embodiment of the method, binder removal and sintering, in particular under vacuum, are carried out after the deformation.

In one embodiment, a nickel-containing metal powder, in particular a CoNiCrAlY powder, is used as the metal powder.

In a further embodiment, a screen printing mask with a screen printing structure can be used, the screen printing mask having openings for pressing through the printing material and the openings being partially wave-shaped, so that the green part has at least partially a three-dimensional wave-shaped structure and / or wave-shaped edges. The wave-like structure lies inside the component and basically replaces known structures, such as honeycomb structures with straight walls. In particular, honeycomb structures with corrugated walls can also be used. As an alternative or in addition, the edges of the component are also designed to be wave-shaped.

Such a green part can, for example, be curved, i.e. deformed, around one or more axes without expansion cracks occurring. In stretched areas, the wave-like structures are drawn further apart. The shafts are pushed together in compressed areas. This can also be described as the “accordion effect”. This means that green parts, and ultimately components with complex shapes, can be manufactured efficiently.

In one embodiment, the wave-like structure has the shape of a honeycomb or a rhombus. For example, honeycomb structures or diamond structures known per se can have at least partially wave-shaped walls.

The screen printing structure can have a plurality of wave-shaped openings which are arranged at least partially parallel to one another, which are in particular the same distance from one another and / or which are at least partly arranged in phase with one another. A wave-shaped opening means here that at least a section of the opening is made wave-shaped. Such an embodiment can then have a very regular pattern, in which the resulting green part has equidistant, wave-shaped structures or, for example, diamond structures with wave-shaped walls. In principle, however, it is possible for the wave-like structures to have a non-uniform structure. The above-described stretchability and compressibility can also be achieved if there are wave-shaped structures over part of the green part, which can also differ from one another in terms of shape.

In a further embodiment, the wave-shaped openings of the screen printing structure have a constant wavelength over their longitudinal extension, the wavelength in particular being greater than 50 μm and less than 5000 μm. By using several wave-shaped structures of this type, a functionally similar structure can be achieved, the known honeycomb structures. If the openings of the screen printing structures have these dimensions, the dimensions of the green part and ultimately the powder metallurgical component are also in this area.

The width of at least one wave-shaped opening in the screen printing mask can also be greater than 50 μm and less than 5000 μm, so that comparatively thin-walled wave-shaped structures can be produced in the green part.

In a further embodiment, at least one wave-shaped structure of the green part has a height in the vertical direction between 1 and 20 mm, in particular between 2 and 10 mm, in particular 5 mm.

At least one wave-shaped opening of the screen printing mask and at least one wave-shaped structure of the green part can also have at least partially a sinusoidal shape in the horizontal section. In this context, a waveform is to be understood more generally than a mathematically exact sinusoidal shape. For example, the wave-like structures can have straight sections without losing their wave-like character.

The object is also achieved by a component that can be produced with at least one of the embodiments of the three-dimensional screen printing process. Such a component has at least one wave-shaped structure. If the component is deformed during the manufacturing process, or possibly also during operation, the wave-shaped structure can specifically absorb expansions and / or compressions, so that cracks or material compressions are avoided or at least minimized. One possible area of application is a sealing surface, in particular in a rub seal in a turbo machine or as part of a rub seal for a turbo machine. A rub seal can be designed as a labyrinth seal.

In one embodiment, the component is at least partially shell-shaped or conical. Such components can preferably be used to line ducts. For example, the radius of curvature can be between 50 mm and 2000 mm, in particular between 100 and 200 mm.

The object is also achieved by a screen printing mask which is suitable for use in at least one of the screen printing processes according to the claims 1 until 14th is established and trained.

For those skilled in the art it is understandable that a A feature or parameter described in relation to any of the above aspects can be applied to any other aspect, provided they are not mutually exclusive. Furthermore, any feature or parameter described here can be applied to any aspect and / or combined with any other feature or parameter described here, insofar as they are compatible not mutually exclusive.

• 1 eine schematische Darstellung eines grundsätzlich bekannten dreidimensionalen Siebdruckverfahrens, mit dem ein Grünteil hergestellt wird;
• 1A eine schematische Darstellung einer Verformung des Grünteils;
• 1B eine schematische Darstellung einer Entbinderung und eines Sinterns des Grünteils;
• 1C eine schematische Darstellung des verformten Bauteils;
• 2 eine schematische Draufsicht auf eine Ausführungsform einer ebenen Siebdruckmaske zur Herstellung eines Grünteils;
• 3 eine schematische Draufsicht auf eine Ausführungsform eines verformten Grünteils, hergestellt mit einer Siebdruckmaske gemäß 2;
• 3A eine schematische Draufsicht auf eine Abwandlung der Ausführungsform des Grünteils gemäß 3;
• 4 eine schematische Seitenansicht eines um eine Achse verformten Grünteils;
• 4A eine schematische, dreidimensionale Ansicht einer Ausführungsform eines verformten Grünteils;

Embodiments will now be described by way of example with reference to the figures; in the figures show:

• 1 a schematic representation of a basically known three-dimensional screen printing process with which a green part is produced;
• 1A a schematic representation of a deformation of the green part;
• 1B a schematic representation of a debinding and a sintering of the green part;
• 1C a schematic representation of the deformed component;
• 2 a schematic plan view of an embodiment of a flat screen printing mask for producing a green part;
• 3 a schematic plan view of an embodiment of a deformed green part, produced with a screen printing mask according to FIG 2 ;
• 3A a schematic plan view of a modification of the embodiment of the green part according to 3 ;
• 4th a schematic side view of a green part deformed about an axis;
• 4A a schematic, three-dimensional view of an embodiment of a deformed green part;

Before, in the following, embodiments of a screen printing process with thermal deformation of a green part produced with it 20th are described, the basic procedure for three-dimensional screen printing is based on 1 shown. This is on a green part 20th (please refer 3 , 3A , 4th , 4A) Reference is made, which is produced in the context of a powder metallurgical process of a rub seal (labyrinth seal) for aircraft engines. In principle, however, other green parts can also be produced with the embodiments shown here.

First is printing material 11th - here for the production of the green part 20th a mixture of metal powder and binder - with the help of a squeegee 12th in the direction of the arrow over the screen printing mask 10 striped.

The screen printing mask 10 has a large number of openings 13th through which the substrate 11th is pressed. In the sectional view according to 1 are seven openings 13th to recognize through which the printing material 11th is pressed.

Below the screen printing mask 10 A layer forms with each push through 14th from the print material 11th out. The individual layers are symbolically represented here by boxes.

In the representation of the 1 are already two full shifts 14th been made, the third layer 14th is currently being manufactured. By shifting the screen printing mask vertically 10 upwards, there is gradually a vertical structure - the green part 20th - produced by screen printing. This process is thus an additive manufacturing process.

In the 1A is shown schematically that after making one from layers 14th built-up green part 20th this is deformed under thermal action. In the example shown here, the deformation temperature is between 30 and 100 ° C. Here the deformation is done by means of a molded part 26th executed, ie the green part 20th is around an axis of curvature 25th with constant radius of curvature R. bent so that a bowl-shaped green part 20th arises. In alternative embodiments, a concave shape can also be used as a molded part 26th be used, or no conical deformation will be made. The deformation time can in particular be between 1 and 30 seconds.

This is followed by debinding and sintering of the green part 20th in an oven 27 ( 1B) . After completing this step, the finished component is in place 30th before, ie a curved shell-like component 30th . Several of these curved components 30th can be assembled to form a ring-shaped abradable seal by brazing, for example. The component produced can thus 30th also be part of a part composed of several parts.

The three-dimensional screen printing embodiments discussed here relate in particular to the production of sealing surfaces as components 30th as used in turbo machines (ie rotary machines). Such abradable seals 30th are e.g. used as a liner 30th used in air ducts of a gas turbine engine of an aircraft. Together with sealing lips (e.g. on discs) they form labyrinth seals.

As mentioned at the beginning, it is known to form these abradable seals with honeycomb structures, the open ends of the honeycombs pointing towards the rotors. For example, if a honeycomb structure is formed in a rectangular Abrasive seal is arranged, a deformation, for example a uniaxial curvature of the abradable seal, leads to stresses in the honeycomb component.

The material is in the area of the largest radius of curvature R. stretched so far in some places that there is not enough material; cracks occur that are undesirable. On the opposite side (i.e. area of smallest radius of curvature R. ) occurs when the green part is bent 20th to compress the material, so that undesired material deformations exist.

As will be shown in the following, the honeycombs should be formed by differently shaped vertical structures in the component 30th replaced or expanded.

Since rub seals are used in a gas turbine engine, e.g. to line the air ducts, this problem is of practical relevance.

In the 2 is an example of an embodiment of a screen printing mask 10 shown in a plan view, for the production of a green part 20th and ultimately a corresponding component 30th is used. The green part should 20th (please refer 3 ) be deformable without significant cracking.

In the embodiment of the screen printing mask 10 according to 2 the tearing and upsetting of the material is avoided by the vertical structures 21 (please refer 3 ) in the green part 20th be formed wave-shaped.

The screen printing mask that has just been formed can be used for this purpose 10 in one embodiment openings 13th with a wavy structure 1 on, the multiple, parallel shaft openings 1' , 1" having. If now metal powder and binder as printing material 11th (please refer 1 ) through the shaft openings 1' , 1' is pressed, a wave-shaped material layer is created 14th who have favourited part of the green part 20th will (see 3 ).

A further material layer can then be created by moving it upwards 14th onto the wave-like structure previously created 21 of the green part 20th be applied. This creates a wave-like structure in the direction of the plane of the drawing 21 as a vertical wall structure. The behavior of the wave-like structure created in this way 21 of the green part 20th Deformations will be described below.

In the illustrated embodiment of the screen printing mask 10 are the undulating openings 1' , 1" formed as uniform, approximately sinusoidal waveforms, each one width A. exhibit. The wavy openings 1' , 1" are formed at the same distance from one another and are in phase, that is, the wave crests and troughs each lie on a straight line when viewed from above. Also the two longer edges of the screen printing mask 10 - in 2 above and below - have a wavy structure.

For typical applications, the width is A. of the undulating openings 1' , 1" between 50 and 200 µm, ie the wall thickness of the vertical, wave-shaped structures 21 in the green part 20th are also in this area.

The wavelength L1 of the undulating openings 1' , 1" is around 2000 µm, so that the wavelength of the wave-like structures 21 of the green part 20th lie in this area.

In alternative embodiments of the screen printing mask 10 are the openings 1' , 1" only partially wave-shaped. For example, the openings can be on the side edges of the screen printing mask 13th each be straight and wave-shaped structures only in the middle 1' , 1" are present. That would be the resulting green part 20th also a wavy structure 21 have, but is undulating only in one or more partial areas, as exemplified in 3A is shown. The waveform can at least partially also deviate from a pure sinusoidal shape and, for example, have linear or otherwise curved sections.

It is also not mandatory that the undulating openings 1' , 1" all in phase; the openings 1' , 1" can also be out of phase with one another.

Furthermore, it is also not essential that the wave-shaped openings 1' , 1" all the same width A. exhibit. There can also be green parts 20th are made of vertical, wavy structures 21 with different wall thicknesses.

In any case, it is important to have the screen printed mask 10 at least partially a wave-shaped screen printing structure 1 with openings 1' , 1" , 13th for pushing through the print material 11th has, so that the green part produced therewith 20th at least partially (in sections) a three-dimensional wave-shaped structure 21 having.

Such a green part 20th is in 3 shown in a plan view, the green part 20th was deformed as the resulting component 30th - not shown here as part of an abradable seal - is also curved.

The wavy structure 21 is in the example 2 , 3 , 3A essentially elongated. But it is also possible that the wave-shaped structure 21 a honeycomb structure or a diamond structure is embossed. This means that the walls of the honeycombs or the rhombuses have at least partially wave-shaped sections, ie the openings in the screen printing mask have at least partly wave-shaped structures. Such a honeycomb or diamond structure can also make use of the concertina effect described above when the structure is bent or compressed.

In the 4th Fig. 3 is a side view of this green part 20th shown in which the green part 20th around an axis of curvature 25th was curved, as is the case in the powder metallurgical manufacturing process (see 1A) is performed. Further possible deformations will be discussed later.

The green part 20th has straight outer edges on both side edges 22nd on. The two opposite long sides are wave-shaped. The wavy structure 21 in the green part 20th is in the vertical direction (ie out of the plane of the drawing) between 1 and 20 mm, in particular between 2 and 10 mm, high compared to the base.

By deforming the green part 20th (in 3 a curvature out of the plane of the drawing) is the longitudinal extension of the green part 20th has become smaller than the length of the flat screen printing mask 10 . This leads to the wavy structures 21 with this curvature at the vertically upper end (ie in the area of the smaller radius of curvature R. ) the wavy structure 21 be shortened. The wavelength L2 of the wavy structures 21 is then smaller than the wavelength L1 of the undulating openings 1' , 1' the screen printing mask 10 (please refer 2 ).

At the bottom that is not visible here (ie the area with the largest radius of curvature R. ) of the vertical, wavy structure 21 the green part is stretched 20th , ie the wavelength there becomes longer than the wavelength L1 of the undulating openings 1' , 1" the screen printing mask 10 .

The wavy structure 21 With this type of deformation, the green part is so resilient that there are no cracks and compression, or these effects are at least minimized.

When the wavy structure 21 is stretched, the wavelength of the structure is simply longer, because there is enough material in the green part 20th exists to follow this deformation. At the points where there is a compression, the wavelength is shortened accordingly.

This could also be called the “accordion effect”. This means that - especially without changing the composition of the printing material 11th - solely with structural-geometric measures of damage to the green part 20th be prevented.

As described above, this became the green part 20th produced by a three-dimensional screen printing process, with the green part 20th was built up in layers. In the embodiment of the screen printing process shown so far, the same printing material is used over the entire process 11th used. The layers 14th that make up the wavy structures 21 of the green part 20th each have the same composition of metal powder and binder (and possibly other substances such as water). However, this does not necessarily have to be the case. In alternative embodiments, it can be for different layers 14th , different printing material 11th can be used. This can be used, for example, to create a wave-like structure 21 whose properties change along the height. In this way, more brittle material can be printed on the top (ie the last layer) than on the lower layers.

In 4th Fig. 3 is a schematic side view of a green part 20th shown around an axis of curvature 25th deformed, ie curved, is. The radius of curvature R. is in the 4th shown. The axis of curvature 25th lies in one plane E. that are parallel to one of the unshaped side compartments 22nd of the green part 20th located. This is the green part 20th Curved cup-shaped and has the same radius of curvature everywhere R. on. From the cuboid green part 20th becomes a bowl-shaped green part 20th , which corresponds to a part of a circular cylinder wall.

The deformation of the green part 21 but can also be done in other ways. For example, if you tilt the axis of curvature 25th relative to the plane E. , so causes a curvature of the green part 20th around this axis of curvature standing obliquely in space 25th the production of a conically shaped green part 20th , and thus also a component 30th . This is schematically shown in 4A shown, which is a conically shaped green part 20th with wavy structures 21 and wavy edges 22nd indicates.

In principle, the green part is also possible 20th more complex to deform by adding more than one axis of curvature 25th is used. Also can the green part 20th have the shape of a trough or an elevation, each of which can be deformed soot-free and free of compression, since it has wave-like structures 21 exhibit.

List of reference symbols

1

wavy screen printing structure

1 ', 1 "

wave-shaped openings of the screen printing structure

10

Screen printing mask

11th

Printing material

12th

Squeegee

13th

Opening in screen printing mask

14th

manufactured layer

20th

screen printed green part

21

undulating structure in green

22nd

Edge of the green part

25th

Axis of curvature

26th

Molded part

27

Vacuum chamber

30th

Component

A.

Width of undulating openings in screen printing mask

E.

Plane in which the axis of curvature lies

L1

Wavelength in the undeformed state

L2

Wavelength in the deformed state

R.

Radius of curvature

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed 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

• DE 102015216491 A1 [0002]

Claims (21)

Three-dimensional screen printing process for producing a green part (20) from printing material (11) for a powder-metallurgical component (30), wherein the printing material (11) has a portion of powder, in particular metal powder or ceramic powder, and binder or consists of these materials, characterized in that that the green part (20) is deformed at temperatures between 30 and 100 ° C after production. Three-dimensional screen printing process according to Claim 1 , characterized in that the temperature remains constant during the deformation. Three-dimensional screen printing process according to Claim 1 or 2 , characterized in that the deformation takes place by means of a molded part (26), in particular in the range between 1 and 30 seconds. Three-dimensional screen printing method according to at least one of the preceding claims, characterized in that the deformation takes place around at least one axis of curvature (25). Three-dimensional screen printing process at least one of the preceding claims, characterized in that the green part (20) is deformed about two axes, in particular that the green part (20) is deformed in such a way that a depression or a bulge is produced. Three-dimensional screen printing method according to at least one of the preceding claims, characterized in that the undeformed green part (20) is essentially cuboid and the deformation of the green part (20) comprises a bend around an axis of curvature (25), the axis of curvature (25) in a Plane lies parallel or inclined to a side surface of the green part (20). Three-dimensional screen printing process according to at least one of the preceding claims, characterized in that, after the deformation, binder removal and sintering, in particular under vacuum, are carried out. Three-dimensional screen printing process according to at least one of the preceding claims, characterized in that a nickel-containing metal powder, in particular a CoNiCrAlY powder, is used as the metal powder. Three-dimensional screen printing method according to at least one of the preceding claims, characterized in that a screen printing mask (10) has a screen printing structure (1) with openings (1 ', 1 ", 13) for pressing through the printing material (11), the openings (1', 1 ') are partially wave-shaped, so that the green part (20) at least partly has a three-dimensional wave-shaped structure (21) and / or wave-shaped edges (22). Three-dimensional screen printing process according to Claim 9 , characterized in that the wave-shaped structure (21) has the shape of a honeycomb or a rhombus. Three-dimensional screen printing process Claim 9 or 10 , characterized in that the screen printing structure (1) has a plurality of wave-shaped openings (1 ', 1 ") which are at least partially arranged parallel to one another, which are in particular the same distance from one another and / or which are at least partly arranged in phase with one another are. Three-dimensional screen printing process according to at least one of the Claims 9 until 11th , characterized in that at least one wave-shaped opening (1 ', 1 ") of the screen printing structure (1) has a constant wavelength (L1) over its longitudinal extent, the wavelength (L1) being in particular greater than 50 µm and smaller than 5000 µm. Three-dimensional screen printing process according to at least one of the Claims 9 until 12th , characterized in that the width (A) of at least one undulating opening (1 ', 1') is greater than 50 µm and smaller than 5000 µm. Three-dimensional screen printing process according to at least one of the Claims 9 until 13th , characterized in that at least one wave-shaped structure (21) of the green part (20) is between 1 and 20 mm, in particular between 2 and 10 mm, in particular 5 mm high. Three-dimensional screen printing process according to at least one of the Claims 9 until 14th , characterized in that at least one wave-shaped opening (1 ', 1 ") of the screen printing mask (10) and at least one wave-shaped structure (21) of the green part (20) in horizontal section at least partially have a sinusoidal shape. Three-dimensional screen printing process according to at least one of the Claims 9 until 15th , characterized in that the deformation causes an elongation and / or compression of at least parts of the undulating structure (21) of the green part (20), which is compensated for by adjusting the wavelength (L2). Component, producible with a method according to at least one of Claims 1 until 16 . Component (30) after Claim 17 , characterized in that this is designed as a sealing surface, in particular as a rub seal, in a turbo machine or as part of a rub seal for a turbo machine. Component after Claim 17 or 18th , characterized in that the component (30) is at least partially shell-shaped or conical. Component (30) according to at least one of the Claims 17 until 19th , characterized in that a radius of curvature (R) of the component (30) is between 50 mm and 2000 mm, in particular between 100 and 200 mm. Screen printing mask (10) for use in at least one of the screen printing processes according to FIGS Claims 1 until 16 .

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