DE102021212754A1 - Method and device for producing at least two objects using powder bed-based additive manufacturing - Google Patents

Abstract

The invention relates to a method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing in at least two powder beds (5, 9) arranged one above the other, in which a first layered structure made of powdered material (3) is used as a first powder bed (5) is produced on a production level (6) and the connection of particles of the powdery material (3) of the first powder bed (5) is strengthened in some areas for the purpose of producing at least one first object (2), a separating element (13) comprising a plurality of openings (12). at least one support element (10) is placed, so that the separating element (13) at least partially overlays the first powder bed (5), a second layered structure made of powdered material (3) is produced as a second powder bed (9) on the separating element (13). and the connection of particles of the powdery material (3) of the second powder bed (9) is strengthened in some areas for the purpose of producing at least one second object (4), and powdery material (3) present between the production plane (6) and the separating element (13), which has not been solidified is at least partially removed, and non-solidified powdery material (3) above the separating element (13) falls through a plurality of openings (12) of the separating element (13). The invention also relates to a device (1) for producing at least two objects (2, 4) using the method according to the invention.

Description

The invention relates to a method for producing at least two objects by means of powder bed-based generative manufacturing in at least two powder beds arranged one above the other and a device for producing at least two objects using the method according to the invention.

In the production of objects or parts of objects using generative or additive manufacturing processes, the object to be produced is built up in layers from an amorphous or powdered material. In each layer, binder or thermal energy is introduced in certain areas for the purpose of solidification. Thereafter, the existing powdery material which has not been solidified is removed. This process is difficult because the objects move during this process and can damage each other accordingly. Furthermore, when removing the existing non-solidified powdery material, or when depowdering the objects, the objects can sink onto one another, as a result of which fragile areas or edges of the respective objects can be damaged by the collision between the objects. This danger is particularly present with automated depowdering. The automated de-powdering can be realized by automatically discharging the existing non-solidified powdery material. A manual individual removal of the individual items is possible, but this method is very inefficient and cost-intensive due to the high time and resource requirements.

In addition, a Computerized Numerical Control "CNC"-supported compressed air nozzle can be used to depowder approximately the respective upper halves of the objects. The items are then removed manually, rotated 180° and placed with the depowdered area in a printed template for the fixture. The other halves of the corresponding items are then de-powdered. However, this procedure is also associated with a great deal of effort.

1 illustrates one procedure according to the prior art. 1 shows a cross section through a device 1 for the production of several objects 2, 4, which is operated with a conventional method for the production of several objects 2, 4 by means of powder bed-based additive manufacturing. The objects 2, 4 are made from a powdery material 3 by means of the powder bed-based additive process. The objects 2, 4 are referred to here as first objects 2 and second objects 4. The second items 4 are printed at a higher level than the first items 2 such that the second items 4 are in the powder bed 5 above the first items 2 . A layered structure made of powdered material 3 as a powder bed 5 is produced on a production level 6 . The first objects 2 and the second objects 4 are printed by strengthening the local connection of particles of the powdery material 4 of the powder bed 5 .

As in 2 shown, after the first objects 2 and then the second objects 4 have been printed, the remaining powder material 3 is removed from the powder bed 5 which has not yet solidified. With the removal of the powdery material 3, the objects 2 and 4 generally sink. This can lead to collisions between the objects, as symbolized by the first object 2.

Accordingly, the second items 4 printed at a higher level than the first items 2 fall onto the manufacturing level 6 or collide with the first items 2 below the second items 4 . These collisions can lead to damage 8 to the objects 2, 4, in particular to the corners and edges of the objects 2, 4. The damage 8 is symbolized by the respective character. Accordingly, this process is associated with an increased reject rate.

It is therefore desirable to use the simplest possible means to ensure that a collision between the two objects 2, 4 or between the second objects 4 and the production plane 6 can essentially be ruled out.

The DE 10 2007 033 434 A1 discloses a method for producing three-dimensional components by means of a three-dimensional printing method, with an auxiliary structure also being formed when components are built up beyond an extension of the component or components. Furthermore, the invention relates to an auxiliary structure for components produced by means of three-dimensional printing methods, the auxiliary structure being built up with the component and extending beyond one dimension of the component or components.

The EP 3 427 868 A1 discloses an additively manufactured element having a support structure bonded to an article body. The connectors that connect the support structure to the article body are fused supports. The Document further discloses a method of removing the support structure from the article body while bypassing an electric current through the fused supports, thereby breaking the fused supports.

The present invention is based on the object of providing a method and a device for producing at least two objects by means of powder bed-based additive manufacturing, with which the production of a plurality of objects is made possible in an efficient and cost-effective manner with a low scrap rate.

The object is achieved according to the invention by a method for producing at least two objects by means of powder bed-based generative manufacturing according to claim 1 and by a device for producing at least two objects according to claim 7 . Advantageous embodiments of the method are shown in dependent claims 2-6. Advantageous embodiments of the device are shown in dependent claims 8-10.

A first aspect of the invention is a method for producing at least two objects by means of powder bed-based additive manufacturing in at least two powder beds arranged one above the other, in which in a first step a first layer structure made of powdered material is produced as a first powder bed on a production level, and the connection is produced in certain areas of particles of the pulverulent material of the first powder bed for the purpose of producing at least one first article. Then, in a second step, a separating element comprising a plurality of openings is placed on at least one support element, so that the separating element at least partially overlaps the first powder bed. In a third step, a second layered structure of powdered material is produced as a second powder bed on the separating element and the connection of particles of the powdered material of the second powder bed is strengthened in some areas for the purpose of producing at least one second object. In a fourth step, powdery material present between the production plane and the separating element that has not been solidified is at least partially removed, and unsolidified powdered material above the separating element falls through a plurality of openings of the separating element.

A powdery material within the meaning of the invention is a shapeless material, e.g. B. a powder or a bulk material, which is essentially composed of smaller particles, such as sand or a metal powder.

The material in powder form is discharged onto a production level by means of a material discharge unit. The manufacturing level is used to carry or support the deployed material. The production level can be a platform on which the first layer structure made of powdered material is produced as a first powder bed. Alternatively, the production level can be designed as a support element or as a container, such as a so-called job box, for example, in which the first layered structure made of powdered material is produced as a first powder bed.

By means of the method according to the invention, at least one first object is produced layer by layer on the production level from the first layered structure made of the powdery material.

Various additive manufacturing processes such as stereolithography, laser beam melting, laser sintering, electron beam melting, fused layer modeling and digital light processing can be used, which can process different powdered materials and are therefore also suitable for different applications.

A solidifying agent can be applied at least to the surface of the powdered material, so that the connection of particles of the powdered material of the first powder bed is strengthened in some areas for the purpose of producing at least one first object. It is not excluded that the solidifying agent partially penetrates into the powdery material.

A solidification agent can also be referred to as a binder in the context of powder bed-based generative manufacturing, in particular in the binder jetting process. It serves to connect the particles of the powdered material to one another in the area in which it is applied or introduced. The solidifying agent is applied to areas of the surface of the powdered material, namely areas where a portion or layer of the article is to be formed.

As an alternative or in addition to the solidification agent, thermal energy can be introduced in certain areas into the discharged amorphous material or into the surface of the powdered material by means of the material reinforcement unit. By means of the thermal energy, the powdered material can be partially melted or at least partially melted in the production plane, so that a section or a layer of the object to be produced can be penetrated subsequent solidification of the previously melted material is generated.

The manufacturing level, into which the solidification agent and/or thermal energy is introduced, is at a distance from the material reinforcement unit.

Furthermore, a separating element comprising a plurality of openings is placed on at least one support element, so that the separating element overlaps the first powder bed at least in regions. A second layered structure of powdered material is then produced as a second powder bed on the separating element and the connection of particles of the powdered material of the second powder bed is reinforced in some areas for the purpose of producing at least one second object.

The separating element can be designed as a support element or as a container on which the second layered structure made of powdered material is produced as a second powder bed.

Similar to the first layer structure made of powdered material on the manufacturing level, solidification agent and/or thermal energy is also introduced into the second layer structure made of powdered material above the separating element, the separating element being spaced from the material reinforcement unit. The separating element can also be a flat plane.

Accordingly, it is provided that in the method or printing process according to the invention, the objects are placed, for example, in a construction chamber in such a way that clearly separate layers of objects are created along the direction of gravity. After the first layer of objects has been produced in the printing process, the printing process is briefly interrupted to manually or automatically place a separator covering the entire production level or build platform on the first powder bed. This separator is then covered with powder again and the printing process can continue with the second layer of items.

In addition, the first objects arranged in a first layer and the second objects arranged in a second layer located above the first layer can be sorted according to the size or the weight of the objects to be printed. That is, the items with a large size and/or weight can be sorted as the first layer of items to be printed, while the items with a smaller size and/or weight than the first items are sorted as the second layer of items can. The second layer of objects is then printed over the first layer of objects on the separator.

The size and shape of the openings of the separator can be the same or different. However, the sizes and shapes as well as the arrangement of the openings of the separator are such that the second objects to be printed on the separator cannot fall through the respective openings and/or cannot partially penetrate the respective openings. This ensures that the printed second layer of items will not be damaged.

Subsequently, powdery material present between the production level and the separating element that has not been solidified is at least partially removed, with non-solidified powdery material falling above the separating element through a plurality of openings in the separating element.

This method makes it possible, when discharging the powdered material downwards, e.g. B. in the automatic de-powdering to collect the respective printed objects on the separator. This prevents the objects from falling on top of each other in an uncontrolled manner, so that damage to the components is avoided.

However, the separating element can be supported on the corresponding support elements, so that the separating element does not sink onto the objects lying underneath. This creates a stack of carrier elements, each of which has a layer of objects on it. The objects can then be removed and finally de-powdered.

The method according to the invention offers the advantages that the use of separating elements in the printing process for fixing objects enables an improvement in automation, that the printed objects can be removed from the powder bed without damage and that the handling of the objects can be improved.

According to one embodiment of the method, it is provided that binder is applied to at least one area of powdered material and the binder is heated to harden the binder. Accordingly, the method is carried out as an additive manufacturing method, in particular for metallic objects. This type of process is also known as binder jetting.

In this method, the metallic powdery material is bonded in a shape of an article layer by layer with the aid of a binder. The object created in this way can also be referred to as a green part and is characterized by limited strength, since it is only held together by the binder applied. Before the objects can be removed from the powder bed, the binder should be thermally activated and hardened. This process is also known as the curing process. The final strength is achieved by a final sintering process.

According to a further embodiment of the method, the support element can be produced from the powdered material of the first powder bed by the additive method. In particular, it is provided that support elements are also printed in the corners of the build chamber, optionally also along the edges. In other words, the support elements are also objects from the first layer of objects that are printed using the generative method, with the separating element being placed or placed on the support elements printed by the method. This is advantageous since in this way an efficient approach for the provision of a carrier for the separating element is realized and no separate supporting element to be integrated in the printing process is required. As a result, the method can be carried out cost-effectively.

Alternatively, it is provided that the support element is set up as a separate body on the production level. This means that the support element is a body or object that is not produced in the course of the generative process or the generative manufacturing process in the first powder bed, but is placed on the production level as a finished object. The support element can include a horizontal latching element onto which the separating element is placed. The support element can be erected before, at the same time or after the generative printing process on the production level.

According to a further embodiment of the method, it is provided that the height of the support element is greater than the height of a largest first object, the height being measured perpendicularly to the production plane. This ensures that a smallest distance between the separating element and the production plane to be measured perpendicularly to the production plane is greater than the height of the largest first object. In particular in the event that the support element is produced by the generative process from the powdered material of the first powder bed, it is provided that the support element has the greatest height in the respective layer.

According to a further embodiment of the method, a plurality of separating elements are arranged in different levels above the production level. Between the separating elements and on the uppermost separating element, objects are produced in the respective powder beds by means of additive manufacturing, with unsolidified powdered material of a respective powder bed above it falling through the openings of the respective separating element between these powder beds after removal of unsolidified powdered material from a respective powder bed. In other words, after the fourth step of the method, the method has the further steps that a further separating element comprising a plurality of openings is placed on at least one support element, so that the further separating element at least partially overlays the powder bed present under the further separating element. Thereafter, a further layered structure of powdered material is produced as a further powder bed on the further separating element, with the connection of particles of the powdered material being strengthened in some areas for the purpose of producing at least one further object. Subsequently, a powdery material that is present directly below the further separating element and has not been solidified is at least partially removed, with non-solidified powdery material above the further separating element falling through a plurality of openings in the further separating element. This makes it possible to insert several separating elements in order to produce objects generatively in more than two layers.

A second aspect of the invention is a device for producing at least two objects using the method according to the invention for producing at least two objects by means of powder bed-based additive manufacturing, comprising a material output unit for producing a first layer structure made of powdered material as a first powder bed on a production level, a material reinforcement unit for strengthening the regional connection of particles of the powdery material of the first powder bed for the purpose of producing at least one first object, and a separating element comprising a plurality of openings for laying on a support element, the separating element being designed for regionally superimposing the first powder bed. The material output unit is designed to produce a second layered structure of powdered material as a second powder bed on the separating element, and the material reinforcement unit is designed to reinforce the regional connection of particles of the powdered material Material of the second powder bed for the purpose of producing at least one second object. The separating element is designed in such a way that non-solidified powdered material above the separating element can fall through a plurality of openings in the separating element when powdered material present between the production plane and the separating element has been removed. Furthermore, the device can have a material removal unit, which is designed to at least partially remove powdery material that is present between the production plane and the separating element and that has not been solidified. Furthermore, the material removal unit can also be designed to at least partially remove powdery material that is present between two separating elements and has not been solidified.

According to one embodiment of the device, it is provided that the device comprises a binder dispensing unit, which is designed to apply binder to at least one area of the powdery material, and comprises a heating unit, which is designed to heat the binder to harden the binder.

As a result, the powdered material, in particular a metallic powdered material, can be bound in layers in the form of an object with the aid of a binder.

Before the objects can be removed from the powder bed, the binder must be thermally activated and cured. This process is carried out by a heating unit.

The separating element can be made of steel and have a thickness of at least 5 mm. This gives the divider a solid shape, even when loaded with the heavy weight of the printed items.

According to a further embodiment, the support element can be a body produced by the method from the powdery material of the first powder bed. This is advantageous because it provides an efficient approach to providing a support for the separator and eliminates the need for a separate support member.

The invention is explained below with reference to the exemplary embodiment illustrated in the accompanying drawings.

• 1: Einen Querschnitt durch eine Vorrichtung zur Herstellung von mehreren Gegenständen gemäß dem Stand der Technik,
• 2: Einen Querschnitt durch die Vorrichtung aus 1, wobei das nicht verfestigte pulverförmige Material entfernt wurde;
• 3: Einen Querschnitt durch eine Vorrichtung zur Herstellung von mehreren Gegenständen, betrieben nach dem erfindungsgemäßen Verfahren zur Herstellung von mindestens zwei Gegenständen mittels pulverbettbasierter generativer Fertigung; und
• 4: Einen Querschnitt durch die Vorrichtung aus 3, wobei das nicht verfestigte pulverförmige Material entfernt wurde.

Show it

• 1 : A cross section through a device for the production of several objects according to the prior art,
• 2 : A cross section through the device 1 with the unsolidified powdery material removed;
• 3 : A cross section through a device for the production of several objects, operated according to the method according to the invention for the production of at least two objects by means of powder bed-based additive manufacturing; and
• 4 : A cross section through the device 3 , with the unsolidified powdery material removed.

1 and 2 show the state of the art and has already been explained at the beginning.

3 shows the device 1 according to the invention for the generative production of objects 2, 4, operated according to the method according to the invention for the production of objects 2, 4 by means of powder bed-based generative production in at least two powder beds 5, 9 arranged one above the other.

In the 3 Device 1 shown shows, analogously to that in 1 Device shown has a production level 6 and first objects 2 and second objects 4, which were produced from powdered material 3. A first layered structure made of powdered material 3 as a first powder bed 5 has been produced on the production level 6 , with the connection of particles of the powdered material 3 of the first powder bed 5 being strengthened in some areas for the purpose of producing a plurality of first objects 2 .

In addition to 1 it is shown here that two support elements 10 were produced from the powdered material 3 of the first powder bed 5 by the additive process. The support elements 10 are printed along the edges 11 of the fabrication plane 6 and on the fabrication plane 6 . It can be seen that the height of the respective support element 10 is greater than the height of the largest first object 2, the height being measured perpendicularly to the production plane 6.

A separating element 13 comprising a plurality of openings 12 is placed on the support elements 10 so that the separating element 10 overlays the first powder bed 5 at least in regions. Since the separating element 13 is placed on the supporting elements 10, a smallest distance between the separating element and the production plane to be measured perpendicular to the production plane is greater than the height of the largest first object, the height being measured perpendicular to the production plane.

A second layered structure of powdered material 3 as a second powder bed 9 is produced on the separating element 13, with the connection of particles of the powdered material 3 of the second powder bed 9 being reinforced in some areas for the purpose of producing a plurality of second objects 4.

4 shows that between the production level 6 and the separating element 13 existing powdery material 5 from the 3 that was not solidified was removed. Furthermore, in 4 shown that on the separating element 13 existing powdery material 5 from the 3 that was not solidified was removed. This removal of pulverulent material 3 from the area above the separating element 13 took place in that unbound pulverulent material 3 fell through the openings 12 of the separating element 13 .

However, the sizes and shapes as well as the arrangement of the openings 12 of the separating element 13 are such that the second objects 4 do not fall onto the separating element 13 through the respective openings 12 or do not partially penetrate the respective openings 12 .

Reference List

1

contraption

2

first item

3

Powdered material

4

second item

5

First powder bed

6

manufacturing level

8th

damage

9

Second powder bed

10

support element

11

Edge of the crafting plane

12

opening

13

separator

QUOTES INCLUDED IN DESCRIPTION

This list of 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 102007033434 A1 [0008]
• EP 3427868 A1 [0009]

Claims (10)

Method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing in at least two powder beds (5, 9) arranged one above the other, in which: I. A first layered structure made of powdered material (3) is produced as a first powder bed (5) on a production level (6) and the bonding of particles of the powdered material (3) of the first powder bed (5) in certain areas for the purpose of producing at least one first object (2) is reinforced; II. a separating element (13) comprising a plurality of openings (12) is placed on at least one support element (10), so that the separating element (13) overlays the first powder bed (5) at least in regions; III. a second layer structure made of powdered material (3) is produced as a second powder bed (9) on the separating element (13) and the bonding of particles of the powdered material (3) of the second powder bed (9) in certain areas for the purpose of producing at least one second object (4 ) is reinforced; and IV. Powdered material (3) present between the production level (6) and the separating element (13) that has not been solidified is at least partially removed, and non-solidified powdered material (3) above the separating element (13) through a plurality of openings (12 ) of the separating element (13) falls. Method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing claim 1 , characterized in that binder is applied to at least one area of powdered material and the binder is heated to harden the binder. Method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing claim 1 or 2 , characterized in that the support element (10) is produced by the additive process from the powdery material (3) of the first powder bed (5). Method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing claim 1 or 2 , characterized in that the supporting element (10) is set up as a separate body on the production level (6). Method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing according to one of the preceding claims, characterized in that the height of the support element (10) is greater than the height of the largest first object (2), the height being vertical to the production plane (6) is to be measured. Method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing according to one of the preceding claims, characterized in that a plurality of separating elements (13) are arranged in different levels above the production level (6) and between the separating elements (13) and objects are produced on the uppermost separating element in respective powder beds (9) by means of additive manufacturing, after removal of unsolidified powdery material (3) of a respective powder bed (9), unsolidified powdery material (3) of a respective powder bed located above it through the openings (12 ) of the respective separating element falls between these powder beds. Device (1) for producing at least two objects (2, 4) by a method for producing at least two objects (2, 4) by means of powder bed-based additive manufacturing according to one of Claims 1 until 6 , comprising: a material output unit for producing a first layer structure of powdered material (3) as a first powder bed (5) on a manufacturing level; a material strengthening unit for strengthening the regional connection of particles of the powdery material (3) of the first powder bed (5) for the purpose of producing at least one first object (2); and a separating element (13) comprising a plurality of openings (12) for placing on a support element (10), the separating element (13) being designed to overlap the first powder bed (5) in certain areas, and the material output unit for producing a second layered structure made of powdered Material (3) is formed as a second powder bed (9) on the separating element (13), and wherein the material strengthening unit for strengthening the regional connection of particles of the powdery material (3) of the second powder bed (9) for the purpose of producing at least one second object ( 4) is formed, wherein the separating element (13) is formed in such a way that non-solidified powdery material (3) above the separating element (13) can fall through a plurality of openings (12) of the separating element (13) when between the production level (6) and powdery material (13) present in the separating element (13) has been removed. Device (1) for producing at least two objects (2, 4). claim 7 , characterized in that the device (1) comprises a binder dispensing unit adapted to apply binder to at least a portion of the powdery material (3) and a heating unit adapted to heat the binder to harden the binder. Device (1) for producing at least two objects (2, 4). Claims 7 or 8th , characterized in that the separating element (13) is made of steel and has a thickness of at least 5 mm. Device (1) for producing at least two objects (2, 4). Claims 7 until 9 , characterized in that the supporting element (10) is a body produced by the method from the powdery material (3) of the first powder bed (5).

Images