DE102021213790A1 - Process and device for the production of a component using additive manufacturing processes by building up in layers - Google Patents

Abstract

The invention relates to a method for producing a component (1) in an essentially powder-based additive manufacturing method by layered construction from at least a first powdered material (10), in which on a production level (3) first powdered material (10) and at least a second Material (20) is discharged, and in which the first material (10) is solidified at least in regions for the purpose of forming a component layer (12), and wherein at least one solidified component layer (12) is chemically and/or thermally treated in such a way that the second material (20) can be separated from the component layer (12) by conversion into a liquid or gaseous phase, and the second material (20) is separated from the component layer (12), so that after essentially complete removal of the second material (20) in a cavity (2) is formed in the first material (10). The invention also relates to a device (40) for carrying out the method according to the invention.

Description

The invention relates to a method for producing a component in an essentially powder-based additive manufacturing method by building it up in layers from at least one first material in powder form, and to a device for carrying out the method according to the invention.

Additive manufacturing processes for the production of components in 3D printing processes have now become economically relevant as series production processes due to the wide range of design options. Typically, this involves powder-based layer construction methods with selective solidification in a respective layer. In principle, this process can be used to produce components with very thin and complex channel structures inside the component. However, such constructions are limited by the fact that the powder must be completely removed from the channel structures before the final solidification of the green body produced in the 3D printing process without damaging it. The established depowdering methods, such as manual removal with brushes or the use of compressed air, reach their limits in winding and narrow channels.

The EP 3 660 085 A1 shows a method and compositions of materials for the production of support material in or for a 3D object, whereby the principle of energy pulse-induced transfer printing is used for the application of material. The method is particularly suitable for dental objects. For this purpose, the document proposes various materials with a specific composition, which can be applied using energy pulse-induced transfer printing in a 3D printing process.

The WO 2017/132267 A1 shows a 3D printing method with nozzle-based material discharge, whereby a support material is also used here in addition to the actual construction material of the object. The WO 2017/132267 A1 also proposes different materials or combinations of materials.

The present invention is based on the object of providing a method and a device for producing a component in an essentially powder-based additive manufacturing method by building up layers of at least one first powdery material, which enable simple and cost-effective production.

The object is achieved according to the invention by a method for producing a component in an essentially powder-based additive manufacturing method by layered construction from at least a first powdery material according to claim 1, and by a device for producing a component by means of the method according to claim 10. Advantageous embodiments of the method according to the invention are shown in the dependent claims 2-8.

A first aspect of the invention is a method for producing a component in an essentially powder-based additive manufacturing process by building it up in layers from at least a first material in powder form, in which the first material in powder form and at least one second material are applied on a production level, and in which the first Material for the purpose of forming a component layer is at least partially solidified. At least one solidified component layer is treated chemically and/or thermally in such a way that the second material can be separated from the component layer by being converted into a liquid or gaseous phase, and the second material is separated from the component layer, so that after essentially complete removal of the second material in the first material a cavity is formed.

The first powdery material may be a metal powder, a metal alloy powder, a plastic powder and/or a ceramic powder.

The first and the second material are applied in a first step. The first and the second material can be applied simultaneously, sequentially or alternately on the production level. The first and the second material are applied in such a way that a material layer with a material layer thickness, measured perpendicularly to the production plane, of at least 50 μm and at most 200 μm is produced.

Before creating a first material layer comprising the first and/or the second material, a digital model of the component to be produced is created in such a way that the component, and typically also the space immediately surrounding the component, is divided into virtual volume elements with typically but not necessarily rectangular Floor space is divided. Cuboid volume elements, in particular cubic ones, are customary. The height of a volume element perpendicular to the base corresponds typically, but not necessarily, to the material layer thickness of a material layer. Each virtual volume element is assigned the information as to whether first material or second material is to be applied to a partial area of the production plane that delimits the respective volume element, and whether the material in the respective volume element is solidified or remains unsolidified. In other words, it is determined for a respective virtual volume element whether it is a component in its later embodiment as a result of the manufacturing process, or whether it is a cavity, recess, component environment or a comparable free space.

The digital model is transmitted to a first control device of a dispensing device for dispensing the first and second material and to a second control device of a solidification device of a device for producing a component in an essentially powder-based additive manufacturing process by building up layers of at least one first material in powder form.

The production level is divided into ideal sub-areas. A patch is typically, but not necessarily, the base of a volume element. A first or a second material is assigned to each patch of each manufacturing level. Typically, but not necessarily, the patches are rectangular, particularly square. The first and the second material are applied in such a way that a volume element filled with the first or second material extends perpendicularly to the production plane for each partial area. In this case, volume elements that are filled with the first material and are solidified after removal of unsolidified powder and removal of the second material are volume elements of a green component or, after final solidification of the green component in a debinding and/or sintering process of the component. In contrast, volume elements that are filled with the second material are cavities in the green component or the component after the second material has been removed.

In particular in areas in which partial surfaces to which the first material is applied and partial surfaces to which the second material is applied are arranged next to one another, it cannot be ruled out that the first and second material will partially mix.

A cavity within the meaning of the invention can be either a cavity, in particular a channel-like cavity, extending into the component or through the component. A cavity can also be a recess in or on the component surface or a cavity, the cavity having an opening to the outside of the component through which the second material can be removed from the cavity.

The solidification of the first powdered material takes place in particular in a second step by introducing energy, in particular by means of laser radiation, into the first material and/or by introducing or applying a binder into and/or onto the first material. It is not excluded according to the invention that, in particular in the edge region of the first material, the second material is also at least partially consolidated. A hardened component layer is produced by the hardening.

The steps of applying the first and second material and of producing a solidified component layer are typically carried out several times in succession, so that the component to be produced or its green component is produced in layers from component layers that build on one another.

At least one solidified component layer, but in particular a component section comprising several component layers or all component layers of the component together, are treated chemically and/or thermally. A thermal treatment is to be understood as any treatment in which thermal energy is supplied to the component layer, in particular to the second material in the component layer. In particular, a thermal treatment can bring about combustion, vaporization, evaporation or sublimation of the second material. A chemical treatment is to be understood as meaning any treatment in which at least the second material is materially converted, wherein a material conversion is also to be understood as meaning the change in the physical state of the second material. The conversion of the second material into a solution is also a chemical treatment within the meaning of the invention. A chemical and a thermal treatment can be carried out alternatively, simultaneously or sequentially, and multiple times.

The chemical and/or thermal treatment converts the second material into a liquid or gaseous phase. In contrast, the first material, at least the solidified first material, remains essentially in the solid phase during and after the chemical and/or thermal treatment, so that the second material can be separated from the component layer due to a phase difference between the first and the second material.

The second material can be removed from the component layer by gravity and/or by centrifugal force. Likewise, the removal of the second material from the component layer can be driven by a pressure difference.

The chemical and/or thermal treatment and the removal of the second material can NEN take place substantially simultaneously in a specific embodiment. It is also possible that a solidification of the first material, in particular a debinding and/or the sintering of the first material, additionally takes place at the same time.

In addition to the second material, unsolidified first material in powder form is essentially completely removed from the component layer at the same time and/or chronologically before and/or chronologically afterwards.

After essentially complete removal or removal of the second material, a cavity in the first material remains in the device layer.

If the first material has not yet fully hardened due to the previous hardening, i.e. a so-called green component is present, this is fed to a further hardening step, in particular a further debinding and/or sintering process, to produce the finally hardened component.

In one embodiment of the method according to the invention, the second material is applied in powder form.

The average particle size of the second material can be smaller than the average particle size of the first material. In particular, the average particle size of the second material is no more than half the average particle size of the first material. In a particular embodiment, the average particle size of the second material is no more than one-third the average particle size of the first material. Alternatively, the average particle size of the second material corresponds to the average particle size of the first material.

In a further embodiment of the method according to the invention, the second material is applied in the liquid phase, the viscosity of the second material during application typically but not necessarily being higher than the viscosity of water at standard conditions. The fact that the material is applied in the liquid phase does not necessarily mean that the second material is a liquid. It can also be mixed with a liquid or dissolved in a liquid.

Furthermore, it is possible for the second material to be applied as a gel, with a gel being a disperse system with a solid component, in the pores of which a liquid and/or a gas can be present.

There is also the possibility that the second material is applied as a dimensionally stable strand of material or, in particular, as an extruded filament on the production level. In particular, the second material, tracing the shape of the channel-like cavity to be formed, can be applied before the first powdery material, so that remaining partial areas of the production level that are not covered with material strands or filaments are then filled with the first material.

In a further embodiment of the method according to the invention, the second material is at least partially an organic material which can be converted into a gaseous phase by a chemical reaction when thermal energy is applied.

In other words, the second material comprises a proportion of organic material, which can typically be converted into a gaseous phase by a combustion reaction, the change in volume and/or pressure of the second material associated with the combustion reaction simultaneously resulting in a substantially complete removal of the second material the hardened component layer.

In a special embodiment, the proportion of organic material in the second material is more than 50% by mass, in particular more than 80% by mass, particularly in particular more than 95% by mass. In a further special embodiment, the organic material is essentially carbon, in particular soot.

In addition, in other embodiments of the method there is also the possibility that the second material is a water-based or a latex-based material.

• - wenigstens eine pyrogene und/oder gefällte Kieselsäure, welche durch Erwärmung in die gasförmige Phase überführbar ist,
• - wenigstens eine natürliche, das heißt auf einem pflanzlichen Rohstoff basierende, Stärke,
• - wenigstens ein Salz einer Stearinsäure,
• - wenigstens eine Glucose,
• - wenigstens eine Lactose,
• - wenigstens einen duroplastischen Kunststoff,
• - wenigstens ein Polyamid,
• - wenigstens ein Epoxidharz,
• - wenigstens ein carboxygruppenhaltiges Polyester,
• - wenigstens ein hydroxygruppenhaltiges Polyester,
• - wenigstens eine Gelatine,
• - wenigstens ein Casein,
• - wenigstens ein Wachs,
• - wenigstens ein Fett,
• - Rizinusöl,
• - wenigstens ein Polyvinylalkohol und/oder
• - wenigstens ein Buten-Diol-Vinylalkohol-Copolymer.

For example, in specific embodiments, the second material may include:

• - at least one pyrogenic and/or precipitated silica which can be converted into the gaseous phase by heating,
• - at least one natural starch, i.e. based on a vegetable raw material,
• - at least one salt of a stearic acid,
• - at least one glucose,
• - at least one lactose,
• - at least one thermosetting plastic,
• - at least one polyamide,
• - at least one epoxy resin,
• - at least one carboxy-containing polyester,
• - at least one hydroxyl-containing polyester,
• - at least one gelatine,
• - at least one casein,
• - at least one wax,
• - at least one fat,
• - castor oil,
• - at least one polyvinyl alcohol and/or
• - at least one butene-diol-vinyl alcohol copolymer.

Waxes, fats and gelatine in particular enable a cavity, in particular a channel-like cavity, to be reproduced particularly precisely in the component to be produced by the application of the second material.

In particular, powders of carbon, carbon black, starch, salt of a stearic acid, lactose and glucose can be used in very small particle sizes, which contributes to particularly accurate tracing of a cavity.

Carbon powder and soot also have the advantage that the temperature of the adjoining first material is locally increased by an exothermic combustion reaction when the second material is converted into the gaseous phase, which leads to debinding and sintering of the first material, especially in the edge area of the cavity to be produced. contributes.

It is also possible that when the second material is removed by means of an evaporation and/or a solution process, a local cooling of the first material is brought about.

In particular, the second material meets the requirements that are placed on the food safety of materials.

Alternatively or additionally, the second material is soluble in a liquid, in particular in water, so that it can be converted from a solid to a liquid phase for the purpose of removing it from the component layer.

In a particular embodiment, the first and the second material are selected such that where the first and second material are applied directly next to one another, a reaction of the first and second material can take place, in particular during the chemical and/or thermal treatment, whereby in the transition area between the cavity of the component and the first material, the cavity wall is sealed and/or the component strength is increased compared to the solidified first material.

In a further embodiment of the method according to the invention, the second material is a binder for strengthening the first material.

In particular, the second material is essentially the same material that is applied to the first material or introduced into the first material to solidify the first material.

The advantage of this embodiment is that the second material during the debinding and / or sintering process for the final solidification of the first material, through which the finally solidified component is produced from the component green body, in which the gas phase is transferred and removed, whereby the number the required process step is reduced.

In a further embodiment of the method according to the invention, the second material is arranged in relation to the first material in such a way that a channel-like cavity is formed in the first material after the removal of the second material.

In other words, the second material is applied where a cavity is to be formed in the green component or in the finally solidified component, which cavity extends through the component or at least into the component. In particular, the channel-like cavity is essentially completely delimited by the first material along its main extent.

In a special embodiment, the smallest clear height and/or the smallest clear width of the channel-like cavity is less than 5 mm, in particular less than 2 mm.

In a further embodiment of the method according to the invention, the channel-like cavity is formed in such a way that its course deviates from a shortest ideal linear connection between a channel start and a channel end.

In other words, the channel-like cavity has at least one change of direction, in particular at least two changes of direction, along its course through the component or into the component. In this case, the change in direction does not have to be formed within a component layer, i.e. not parallel to the production plane, but can also be in one for production be formed in the vertical plane within the component.

In a further embodiment of the method according to the invention, the first material and the second material are applied together on the production level by means of a material carrier on which the first material and the second material are prefabricated in relation to one another. Alternatively, the first material and/or the second material is/are applied by means of at least one nozzle on the production level.

Another alternative is to use a coater, in particular a trickle coater, for applying the material. A trickle coater is to be understood as meaning a sieve application mechanism in which powder falls through a sieve onto the production level as a result of being stimulated to oscillate. The different application types and application devices can be combined in any way.

In other words, in the variant mentioned first, the first and the second material are transferred jointly from a material carrier to the production level. The first and the second material are arranged on the material carrier in a plan view of the material-carrying side of the material carrier as a mirror image of the desired arrangement of the materials in relation to one another on the production level in the material layer thickness of the component layer to be produced.

In a particular embodiment, the material carrier is a roller that can be rolled over or on the production level, with the prefabricated first and second material being detached from the material carrier during the rolling on the production level.

In the second alternative, the application to the production level takes place by means of nozzles, it being possible for the first and/or second material to be applied at the same time or at a time interval from one another. The first and/or the second material can be applied using the same nozzle. However, separate nozzles can also be used for different materials.

A method for dispensing by means of at least one nozzle can be combined for dispensing by means of a material carrier.

In a further embodiment of the method according to the invention, the chemical and/or thermal treatment is carried out at least once before the formation of a last component layer of the component.

In other words, the removal of the second material takes place for the first time in the course of the layered construction of the component after a first section of the component comprising a plurality of solidified component layers has been produced. In particular, the second material is removed several times during the layered construction of the component.

In particular, the removal of the second material from a component section can be combined with an intermediate powder bed temperature control and/or an intermediate hardening or an intermediate hardening of the first material.

Alternatively, the second material is removed only once, namely after the last component layer has been solidified.

In a further embodiment of the method according to the invention, the at least one component layer is heated during the chemical and/or thermal treatment to a temperature which is lower than the melting point of the first material.

This first temperature is lower than the melting temperature, so that the second material is only converted into the liquid or gaseous phase by means of the first temperature, but not sintering or partial melting of the first material. This first temperature is also higher than the ambient temperature of the component during its layered construction. In the case of a soluble second material, heating to the first temperature can serve to accelerate the dissolving process. In a special embodiment, the first temperature is also higher than the melting and/or boiling temperature of the second material, in particular if the second material is selected in such a way that it can be converted into a gaseous or liquid phase for the purpose of removal from the solid phase, or is to be converted from a liquid phase into a gaseous phase.

After the second material is removed, the consolidated structural layer is heated to a second temperature greater than the first temperature, the second temperature being selected to remove binder from the structural layer for final consolidation and/or sintering of the particles of the first material is effected.

In an alternative embodiment, in particular if the second material is a binder, especially in particular if the second material is the binder that is used to strengthen the first material, the component layer is only heated to a temperature, namely essentially the Tem temperature of debinding and/or sintering of the first material.

A second aspect of the invention is a device for producing a component in an essentially powder-based additive manufacturing process by building up layers of at least a first material in powder form by means of the method according to the invention, comprising a dispensing device for dispensing at least a first material in powder form and at least a second material on a production level , as well as comprising a solidification device for solidifying the first material for the purpose of forming a solidified component layer, and also comprising a treatment device for the chemical and/or thermal treatment of at least one component layer for the purpose of converting the second material into a liquid and/or gaseous phase.

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

• 1: eine schematische Darstellung einer Vorrichtung zur Durchführung einer Ausführungsform des erfindungsgemäßen Verfahrens in einer Draufsicht und
• 2: ein mit dem erfindungsgemäßen Verfahren hergestelltes Bauteil zu zwei verschiedenen Zeitpunkten während der Durchführung des erfindungsgemäßen Verfahrens.

Show it

• 1 : a schematic representation of a device for carrying out an embodiment of the method according to the invention in a plan view and
• 2 : A component produced using the method according to the invention at two different points in time during the implementation of the method according to the invention.

1 shows a schematic representation of a device 40 for carrying out an embodiment of the method according to the invention in a plan view. A point in time between the solidification of a component layer 12 of the three components 1 to be produced here simultaneously and the application of a next layer of material is shown. According to the illustration on the left, the manufacturing plane 3, which is divided into imaginary sub-areas 30 and extends in the x, y-direction, can be seen. The components 1 are built up in layers starting from a base plate 4 .

According to the illustration, an application device 9 can be seen schematically on the right, which has a material supply 11 for the first material 10 and a material supply 21 for the second material 20 . The provision of material 11, 21 can also be located outside of the device 40. Furthermore, the application device 9 has a material carrier 5 which is designed here as a roller which can be rotated about the axis of the shaft 6 . The surface of the material carrier 5 is divided into partial areas 30 in the same way as the production level 3. The first material 10 and the second material 20 can be prefabricated on the surface of the material carrier 5, starting from a digital model for the respective next material layer to be produced . If the material carrier 5 is equipped accordingly, it is moved in a displacement movement 7 over the production level 3 and unrolled on it. In this way, in this special embodiment of the method, first material 10 and second material 20 can be applied to production level 3 at the same time. Subsequently, the hardening of the first material 10 (not shown here) takes place. In this way, a plurality of component layers 12 are produced in the z-direction, building on one another.

What is not shown here is that the entire powder bed with all its material layers 12 was previously generated as a digital model, which consists of individual volume elements to which information was assigned as to whether the respective volume element should be formed with first material 10 or second material 20. and whether or not the respective volume element is solidified. This digital model was transferred to the application device 9 .

As in 1 As can be seen, the second material 20 is arranged in relation to the first material 10 in such a way that the second material 20 forms channel-like cavities 2, some of which undergo at least one change of direction and thus deviate from the shortest ideal connection between a channel start 22 and a channel end 23 . to the in 1 At the point in time of the manufacturing process shown, the cavities 2 in the component layer 12 are completely filled with the second material 20 .

2 shows a component 1 produced using the method according to the invention at two different points in time during the implementation of the method according to the invention. As shown on the left, state A before the chemical and/or thermal treatment can be seen, and as shown on the right, state B after the chemical and/or thermal treatment can be seen.

In state A, the cavities 2 , which here extend in a channel-like manner perpendicularly to the plane of representation, are completely filled with second material 20 within the component 1 made from the solidified first material 10 or its green component. The component 1 is now subjected to a chemical and/or thermal treatment 8 and thereby transferred from state A to state B. During the chemical and/or thermal treatment 8, the second material 20 is converted into the liquid or gaseous phase, so that it can be separated from the first material 10 and the cavities 2 become free.

Reference List

1

component

2

channel-like cavity

3

manufacturing level

4

base plate

5

material carrier

6

Wave

7

traversing movement

8th

chemical and/or thermal treatment

9

application device

10

first material

11

Provision of material first material

12

component layer

20

second material

21

Provision of material second material

22

channel beginning

23

channel end

30

face

40

contraption

A

Condition before chemical and/or thermal treatment

B

Condition after chemical and/or thermal treatment

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

• EP 3660085 A1 [0003]
• WO 2017/132267 A1 [0004]

Claims (10)

Method for producing a component (1) in an essentially powder-based additive manufacturing method by layered construction from at least one first powdered material (10), in which on a production level (3) first powdered material (10) and at least one second material (20) is applied, and in which the first material (10) is solidified at least in regions in order to form a component layer (12), and wherein at least one solidified component layer (12) is chemically and/or thermally treated in such a way that the second material (20) through Conversion into a liquid or gaseous phase can be separated from the device layer (12), and the second material (20) is separated from the device layer (12), so that after substantially complete removal of the second material (20) in the first material ( 10) a cavity (2) is formed. procedure after claim 1 , characterized in that the second material (20) is applied in powder form. Method according to one of the preceding claims, characterized in that the second material (20) is at least partially an organic material which can be converted into a gaseous phase by chemical reaction when thermal energy (8) is applied. Method according to one of the preceding claims, characterized in that the second material (20) is a binder for strengthening the first material (10). Method according to one of the preceding claims, characterized in that the second material (20) is arranged in relation to the first material (10) in such a way that after removal of the second material (20) in the first material (20) a channel-like cavity (2 ) is trained. procedure after claim 5 , characterized in that the channel-like cavity (2) is formed in such a way that its course deviates from a shortest ideal linear connection between a channel start (22) and a channel end (23). Method according to one of the preceding claims, characterized in that the first material (10) and the second material (20) are prefabricated by means of a material carrier (5) on which the first material (10) and the second material (20) are prefabricated in relation to one another are applied together on the production level (3), or that the first material (10) and/or the second material (20) is applied by means of at least one nozzle on the production level (3). Method according to one of the preceding claims, characterized in that the chemical and/or thermal treatment (8) is carried out at least once before the formation of a last component layer (12) of the component (1). Method according to one of the preceding claims, characterized in that the at least one component layer (12) is heated during the chemical and/or thermal treatment (8) to a temperature which is lower than the melting temperature of the first material (10). Device (40) for producing a component (1) in an essentially powder-based additive manufacturing method by layered construction from at least a first powdery material (10) by means of a method according to one of Claims 1 - 9 , comprising a discharge device (9) for discharging at least a first powdery material (10) and at least one second material (20) on a production level (3), and comprising a solidification device for solidifying the first material (10) for the purpose of forming a solidified component layer (12) , and also further comprising a treatment device for chemical and / or thermal treatment (8) of at least one component layer (12) for the purpose of converting the second material (20) in a liquid and / or gaseous phase.

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