DE102021108342A1 - Device for a selective, laser-assisted beam melting process - Google Patents

Abstract

Device (1) for a selective, laser-assisted beam melting process for the layered production of a workpiece (5), in which the material to be processed is applied in powder form in a thin layer (26, 27) to a building board (10) and locally by means of a laser beam (4). completely remelted and, after solidification, forms a solid layer (26, 27), after which the building board (10) is then lowered by at least the amount of one layer thickness and new powder (6) is applied to the building board (10), the bottom side of the The top side (18) of the building board (10) facing the workpiece (5) consists of a laser-melting-resistant layer which forms a clawing structure (17) for fixing the bottom side (29) of the workpiece (5) on the building board (10).

Description

The invention relates to a device for a selective, laser-assisted beam melting process according to the preamble of patent claim 1.

A preferred application of a laser-assisted beam melting process is in laser melting or laser sintering of a powder material, as is the subject of our patent application DE 10 2019 105 223 A1 is.

The relevant disclosure should be encompassed by the disclosure of the present invention description.

A generic device for a selective, laser-assisted beam melting process is, for example, the subject of DE 10 2018 112 381 A1 , in which the material to be processed is applied in powder form in a thin layer on a building board and the powdered material is locally completely remelted layer by layer by means of laser radiation and forms a solid layer of material after it has solidified.

The building board is then lowered by the amount of one layer thickness and powder is applied again. This cycle is repeated until all layers have been remelted. The finished component is cleaned of excess powder, processed as required or used immediately.

The layer thicknesses that are typical for the structure of the component are between 15 and 50 micrometers for all materials.

In order to avoid contamination of the material with oxygen, the process takes place in a protective gas atmosphere with argon or nitrogen.

However, it is felt to be a disadvantage that in the selective, layered production of workpieces, support structures have to be used that fix the workpiece on the building board in order to avoid unwanted movement of the workpiece during the laser melting process.

Such support structures are necessary for thin-walled components in order to avoid any distortion caused by the heat generated by the process in the finished component.

Such support or application structures have the additional function of fixing the printed workpiece (component) on the building board during the process, especially during the wiping process, so that the workpiece cannot be displaced by the wiper, which applies individual layers of metal.

Support structures are generally there to create a connection between the printed component and the construction platform.

These support structures have to be removed after the 3D printing is complete, which makes the workpieces more expensive, especially in a series.

Furthermore, the use of support structures in places in the workpiece with a higher carbon content counteracts distortion of the workpiece.

When the print is complete and the residual powder has been removed from the print space, the build plate is removed along with the printed workpiece and the support structures. The support structure is then removed from the building board in a very complex separation process (by wire EDM, cutting, sawing, milling, lasering, etc.). In order to make the building board printable again for the next print job, it has to be sanded flat. In any case, post-processing of the building board is necessary after the separation process to ensure absolute evenness.

The invention is therefore based on the DE 10 2018 112 389 A1 , the task of developing a device for a selective, laser-assisted beam melting process in such a way that supporting structures can be largely avoided and that a particularly simple removal of the finished workpiece from the building board is possible without substantial post-processing of the building board.

The invention is characterized by the technical teaching of claim 1 in order to solve the task at hand.

The advantage of the technical teaching according to the invention is the simple removal of the printed component from the printer installation space without the time-consuming separation of the support structure and the workpiece and construction board.

A particular advantage of the technical teaching, according to claim 1, is that the support structures can be omitted at least partially or even completely if a clawing structure is provided on the upper side of the building board in the direction of the bottom side of the workpiece adhering thereto.

In a preferred embodiment of this technical idea, it is preferred if at least the upper side of the building board is formed from a layer that is resistant to laser melting, preferably from a ceramic plate, in the upper side of which the clawing structure is arranged. The use of a ceramic plate has the advantage of a particularly melt-resistant and smooth surface. The term "ceramic" includes a variety of inorganic non-metallic materials that can be roughly divided into the types of earthenware, earthenware, stoneware, porcelain and special masses. In common parlance, ceramics also serve as a generic term for the shaped and fired products that are used as components or tools.

A distinction is made between clay ceramics and glass ceramics. In this description, technical ceramics play an important role, which also includes composite ceramics. According to a preferred embodiment, the ceramic plate according to the invention consists of a technical ceramic, in particular a composite ceramic.

In another embodiment, however, a glass ceramic plate can also be used, as is customary in the case of hotplates in electric stoves. This includes glass ceramics that have high permeability to thermal radiation, low thermal conductivity and high thermal shock resistance due to the low coefficient of expansion. They have a smooth, non-porous surface. According to the invention, during the production of such a glass-ceramic plate, the clawing structure is engraved into the previously smooth surface.

When using a composite ceramic material, a heat-permeable ceramic layer that is not too thick is applied to the building board. The layer thicknesses are preferably in the range between 2-30 mm. This layer or plate is provided with tiny holes, which can be as small as 1.5 mm to 0.05 mm in diameter.

In another embodiment, it can be provided that the (natural) pores created during firing of a coated clay body form the claw structure according to the invention.

Provision can also be made for a glass ceramic plate or a composite ceramic plate to be provided with pore-like recesses on the surface either before its hardening process or also subsequently--after its completion.

Printing is now started on the building board, which is enclosed under a protective gas atmosphere and is coated or covered with the ceramic layer. The layer thicknesses normally vary between 20 and 150 µm. The first two to three layers, depending on the layer thickness set, are the necessary connecting layer between the workpiece to be manufactured later and the ceramic plate. The small holes, as described above, are used to claw the lasered powder into the ceramic layer. Depending on the print job, there are different hole spacings, hole diameters and hole depths. Once the print job has been completed and the residual powder has been removed, the workpiece can also be removed from the build space without great effort. With the right configuration, no sanding or other post-processing of the build plate is necessary and you can start a new print immediately.

Accordingly, in a first embodiment, the clawing structure according to the invention consists of a multiplicity of half-open recesses in the laser-melting-resistant layer, which is preferably formed from a ceramic plate.

However, it is not necessary for the solution that the laser-melting-resistant layer is formed from a ceramic plate, because in other embodiments it can be provided that the laser-melting-resistant layer is formed from a perforated plastic or glass plate (e.g. the glass ceramic plate mentioned above), the upper side of which forms the claw structure .

The basic prerequisite for such a clawing structure is therefore the arrangement of a laser-melting-resistant layer on the upper side of the building board, with a ceramic plate, a glass plate or a laser-melting-resistant plastic plate being used as a preferred exemplary embodiment.

It is also possible to provide a multi-layer construction of laser-melt-resistant layers on the building board, with the clawing structure preferably being formed from a lattice-like hole structure.

Such a hole structure can consist of arbitrarily shaped, preferably cylindrical, blind holes or also as through-holes penetrating the laser-melt-resistant layer.

Instead of the arrangement of cylindrical blind holes or through-holes, conical holes or hemispherical or quarter-spherical profile holes can also be used, which can also be used either as blind holes or as through holes ments are arranged in the laser melt-resistant layer.

In another embodiment of the invention, it can be provided that the clawing structure consists solely of a pore structure of the laser-melt-resistant layer or is present in combination with the above-mentioned lattice-like hole structure.

It is of particular advantage that the clawing structure is located below the surface of the building board in contact with the workpiece, so that the finished workpiece can be easily removed from the - otherwise smooth - building board without a mechanical separation process between the bottom side of the workpiece and the - otherwise flat - surface of the building board must take place.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.

All of the information and features disclosed in the documents, including the abstract, in particular the three-dimensional configuration shown in the drawings, could be claimed as being essential to the invention, insofar as they are new compared to the prior art, either individually or in combination. The use of the terms "essential" or "in accordance with the invention" or "essential to the invention" is subjective and does not imply that the features so named must necessarily form part of one or more patent claims.

In the following, the invention is explained in more detail with reference to drawings showing only one embodiment. Further features and advantages of the invention that are essential to the invention emerge from the drawings and their description.

• 1: Schematisierte Darstellung einer Vorrichtung für ein selektives, lasergestütztes Strahlschmelzverfahren.
• 2: Die perspektivische Ansicht einer Bauplatte, die in 1 verwendet wird.
• 3: Schnitt durch die obere Schicht der Bauplatte nach 2 mit der Anordnung eines Sacklochs.
• 4: Eine gegenüber 3 abgewandelte Ausführungsform.
• 5: Eine gegenüber 3 und 4 weitere abgewandelte Ausführungsform.
• 6: Schematisiert im Schnitt die Darstellung der Verkrallungsstruktur zwischen der Bodenseite des Werkstücks und der Oberseite der Bauplatte.

Show it:

• 1 : Schematic representation of a device for a selective, laser-assisted beam melting process.
• 2 : The perspective view of a build plate used in 1 is used.
• 3 : Section through the top layer of the build plate 2 with the arrangement of a blind hole.
• 4 : One opposite 3 modified embodiment.
• 5 : One opposite 3 and 4 further modified embodiment.
• 6 : Schematic representation of the clawing structure between the bottom side of the workpiece and the top side of the building board in section.

In 1 is a schematic representation of a beam melting device 1, in which a laser 3 is arranged in a closed chamber 2 in a protective gas atmosphere, which laser 3 melts a powder bed 30 in layers with its laser beam 4, which is arranged on a building plate 10 that can be raised and lowered in order to to melt a workpiece 5 arranged on the building board 10 in layers.

For this purpose, the powder is layered onto the powder bed 30 from the powder supply 6 with the aid of a wiper 7 moved in the direction of the arrow 9 .

The laser beam 4 thus forms a melting surface 8 which is melted on in layers and which, after solidification, forms the profiled workpiece 5 .

In the exemplary embodiment shown, the upper side of the building board 10 is covered with a ceramic plate 18, the upper side of which carries the claw structure 17 according to the invention.

Excess powder from the powder bed 30 is conveyed by the wiper 7 in the direction of the arrow 9 as residual powder 16 into the powder container 15 .

New powder is made available from the powder supply 6 by raising the lifting device 13 in the direction of the arrow 14 .

The building board 10 is gradually lowered in the direction of the arrow 12 with the aid of the lifting device 11 in order to prepare the workpiece 5 to be melted layer by layer.

the 2 FIG. 1 shows, as a preferred exemplary embodiment, a building board 10 which is covered on its upper side with a ceramic plate 18 on which the claw structure 17 is applied.

In the exemplary embodiment shown, the clawing structure 17 consists of a perforated structure 19 forming a grid 20, the perforated structure 19 optionally consisting of the in 3 blind holes 21 shown can consist or from the 4 shown cone holes 24 or in 5 illustrated hemispherical or quarter-spherical profile holes 25.

The diameter 31 of the respective holes 21, 24, 25 should be about half the size of the hole depth 23 in relation to the panel thickness 22.

In the profiling and the dimensioning of the holes 21, 24, 25, the ease of demolding the workpiece from the claw structure 17 is in the foreground, which means that the hole walls of the holes 21 to 25 can also be conically open to the outside.

Instead of forming blind holes 21, 24, 25, through-holes can also be provided in the ceramic plate 18.

As indicated in the general description, a ceramic plate 18 is preferred for its laser melt resistant property.

Instead of such a ceramic plate, however, other laser melt-resistant materials can be used, such as. B. a glass ceramic plate or a suitable laser melt-resistant plastic plate.

The holes or recesses 21, 24, 25 to be made, which form the hole structures 19 with the grid 20, can be introduced into the surface of the ceramic plate 18 with a laser beam or a plasma jet or mechanically by the kinetic energy of bombardment bodies (sandblasting).

It is also possible to introduce the clawing structure 17 in the ceramic plate 18 during the manufacture of the ceramic plate 18 before it hardens, if this still consists of an unfired clay material and only receives its laser-melting-resistant surface after the firing process.

the 6 shows that the clawing structure is formed from a layered structure 26 of the material layers of the powder bed 30, so that there is a melt-resistant and unbreakable transition to the bottom side 29 of the workpiece 5 built up in the layered structure 27.

The bottom side 29 of the workpiece 5 can thus be easily removed from the upper side 28, which is smooth per se, without the need for costly post-processing of the surface of the building board 10 and the removal of otherwise necessary support structures.

Reference List

1

beam melting device

2

chamber

3

laser

4

laser beam

5

workpiece

6

powder supply

7

wiper

8th

melting surface

9

arrow direction

10

build plate

11

lifting device (centre)

12

arrow direction

13

lifting device (right)

14

arrow direction

15

powder container

16

residual powder

17

claw structure

18

ceramic plate

19

hole structure

20

grid

21

blind hole

22

plate thickness

23

hole depth

24

cone hole

25

profile hole

26

Layer structure (inside)

27

Layer structure (top)

28

Top (of 18)

29

bottom side (of 5)

30

powder bed

31

diameter

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

• DE 102019105223 A1 [0002]
• DE 102018112381 A1 [0004]
• DE 102018112389 A1 [0015]

Claims (10)

Device (1) for a selective, laser-assisted beam melting process for the layered production of a workpiece (5), in which the material to be processed is applied in powder form in a thin layer (26, 27) to a building board (10) and locally by means of a laser beam (4). completely remelted and forms a solid layer (26, 27) after solidification, after which the building board (10) is then lowered by at least the amount of one layer thickness and new powder (6) is applied to the building board (10), characterized in that the the top side (18) of the building board (10) facing the bottom side of the workpiece (5) consists of a layer which is resistant to laser melting and which forms a clawing structure (17) for fixing the bottom side (29) of the workpiece (5) on the building board (10). device after claim 1 , characterized in that the laser-melting-resistant layer is formed from a ceramic plate (18), in the upper side of which the clawing structure (17) is arranged. device after claim 1 or 2 , characterized in that the clawing structure (17) consists of a grid-like hole structure (19). device after claim 3 , characterized in that the hole structure (19) consists of a large number of semi-open recesses (21, 24, 25) in the laser-melting-resistant layer, forming a lattice network (20). device after claim 4 , characterized in that the semi-open recess consists of a blind hole (21) or a conical hole (24) or a hemispherical or quarter-spherical profile hole (25). Device according to one of Claims 1 until 5 , characterized in that the claw structure (17) consists of a pore structure of the laser melt-resistant layer. Device according to one of Claims 1 until 5 , characterized in that the half-open recesses (21, 24, 25) are designed as blind openings. Device according to one of Claims 1 until 7 , characterized in that the diameter of the half-open recesses (21, 24, 25) is in the range between 1.5 and 0.05 mm and that the depth of the recess corresponds to approximately twice the diameter. Device according to one of Claims 1 until 8th , characterized in that the layer resistant to laser melting is formed from a perforated plastic or glass plate, the upper side (28) of which forms the claw structure (17). Device according to one of Claims 1 until 9 , characterized in that the clawing structure (17) is located below the—otherwise smooth—upper side (28) of the laser-melting-resistant layer.

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