DE102018200361A1 - Method and device for dissolving and / or removing powder agglomeration - Google Patents

Abstract

A method for dissolving and / or removing at least one powder agglomeration (14) from a product (12) obtained by additive manufacturing and / or casting, comprising at least the following method steps: a) at least partially wetting the product (12) with a chemically active medium (4), b) at least partially dissolving and / or removing the at least one powder agglomeration (14) with the chemically active medium (4).

Description

State of the art

It is known to produce three-dimensional products by additive manufacturing. For this purpose, for example, in selective laser beam melting (SLM) or electron beam melting (EBM) a powder layer is provided and locally selectively melted with a laser or electron beam. As a result of the melting, the particles of the powder combine with one another, so that the material of the product is formed from the powder. Subsequently, this process is repeated for further layers of the powder, so that the product to be produced is obtained in layers. Such a manufacturing method is for example from the Scriptures US 7,285,234 B2 known. In such processes, the powder not melted by the laser beam is usually removed so that only the product remains, or the powder which will later (after further processing steps) form the product.

To remove the unmelted powder, it is regularly necessary to dissolve sintering necks between individual unmelted powder particles in order to be able to remove the unmelted powder. In the US 7,285,234 B2 the use of a coated powder for the production of three-dimensional products is proposed, wherein the coating can be dissolved with an organic solvent.

Disclosure of the invention

Here, a particularly advantageous method and a particularly advantageous device for dissolving and / or removing at least one powder agglomeration from a product obtained by additive manufacturing and / or casting are presented. The dependent claims specify particularly advantageous developments of the method and the device.

1. a) zumindest teilweises Benetzen des Produkts mit einem chemisch aktiven Medium,
2. b) zumindest teilweises Auflösen und/oder Entfernen der mindestens einen Pulveragglomeration mit dem chemischen aktiven Medium.

The process for dissolving and / or removing at least one powder agglomeration (of a product obtained by additive manufacturing and / or casting, comprises at least the following process steps:

1. a) at least partially wetting the product with a chemically active medium,
2. b) at least partially dissolving and / or removing the at least one powder agglomeration with the chemically active medium.

Components which are manufactured using additive manufacturing processes regularly have a rough surface on which powder deposits or powder deposits can occur. According to the prior art, the components are blasted regularly to remove such powder deposits or powder deposits. For blasting, in particular a powder may be used which contains the same constituents as the powder used as starting material. It is only partially possible to expose internal contours such that there are removed agglomerated particles of the powder used as starting material. This is due in particular to the fact that such internal contours with rays are difficult or impossible to reach. In order to exploit the advantages of additive processes (in particular the freedom of form of complex geometries), there is the necessity of being able to demultivate internal channels as well. This is made possible by the method described here.

Three-dimensional products are also to be produced by casting processes, for the casting of which casting molds produced by three-dimensional additive manufacturing and / or sintering are used. Of such molds, particulate matter may deposit on the product produced by casting operations. Such deposits are similar to remove powder residues in additive manufacturing. Again, it is often difficult to achieve internal contours.

In the context of the method described here, in particular, electron beam melting is considered additive manufacturing. However, the method described can also be applied to any other method of additive manufacturing in which, starting from a powder, a three-dimensional product is obtained.

As already stated, additive agglomeration can leave behind powder agglomerations, in particular on internal edges and / or in channels of the product. Powder agglomerations are to be understood here as meaning interconnected particles which do not form part of the product to be produced and which are to be removed after the production of the product or at the end of the production of the product. Powder agglomerations can consist of a few particles or even of a large number of particles. In particular, the powder agglomerations may be associated with the product to be produced. The connection between the particles of a powder agglomeration with one another and optionally with particles which form the product to be produced are weaker than the connections between the particles which form the product to be produced. In particular, powder agglomerations of particles of the product to be produced can be distinguished. It is also possible that links between the particles of the product and compounds between particles of unwanted powder agglomeration differ in that the compounds of the product consist of a main material of the powder and the compounds of the powder agglomerations of a material of a coating on the powder.

Powder agglomerations may particularly occur when a powder used in additive manufacturing is sintered. In particular, the powder may be sintered after the powder has been provided as a layer and before, for example, locally selectively acting on the powder with a laser. In particular, sintering can be carried out for each powder layer provided. By sintering the powder, the stability of the powder and in particular the powder layers can be increased. By sintering, the particles of the powder can be connected to one another via sintered connections (which can also be referred to as sintering necks). It is believed that a sintering bond between particles is weaker than a compound obtained in additive manufacturing by, for example, reflowing by means of a laser. In particular, particles of powder agglomeration can be connected to one another by sintering compounds and / or with particles of the product to be produced. Sintered powder and particles joined by melting differed in particular in the stability of the connection between the individual particles. With the sintered powder, the individual particles only hold together through the sintered connections, often with a very small diameter. On the other hand, particles connected by melting are regularly connected to one another via a larger connecting surface. In particular, the particles may be connected to each other in such a way that the individual particles are no longer recognizable as such. The individual particles are instead fused into a single body.

Also, the method described can be used in the production of three-dimensional products by casting. Powder agglomerations during casting are in particular components of a casting into consideration, which have been deposited on the product produced. In the following, the method will be described in particular with reference to additive manufacturing. The particular advantages and design features of the method described below and above for additive manufacturing are applicable and transferable to production by casting methods (in particular casting methods in which a mold produced by sintering is used as the casting mold), and vice versa.

After the preparation of the product or at the end of the production of the product, the powder agglomerations are preferably dissolved and / or removed. By dissolving a powder agglomeration, it is to be understood that at least part of the compounds between the particles of a powder agglomeration is broken up. Removal of powder agglomeration means that the powder agglomeration is separated from the product produced. The described method is directed to the dissolution and / or removal of powder agglomerations. In this case, the method described can be regarded as part of an additive manufacturing process or a casting process. In particular, the method described can be carried out as a last method step of a method for additive manufacturing or a casting method, in which prior to carrying out the described method, the product is prepared and exposed so far that powder agglomerations are to be removed in particular from internal contours. However, the method described can also be carried out as a separate method after completion of the additive manufacturing or the casting process. Thus, in particular, the additive manufacturing or the casting process can be performed at a first location and / or by a first user, while the described method is performed at a second location and / or by a second user.

Powder agglomerations may be dissolved and / or removed by the described method through a chemically active medium. As a chemically active medium is any medium that is suitable to dissolve compounds between particles of a powder agglomeration with each other and / or particles of powder agglomeration to the product to be produced. In particular, the chemically active medium is an inorganic acid, preferably a mineral acid, for example a 96% sulfuric acid or a 50% sulfuric acid, or the chemically active medium is in particular an oxidizing agent, for example hydrogen peroxide. In the additive production with sintered powder, the chemically active medium is particularly suitable for dissolving sintered connections between particles. The chemically active medium can penetrate into the interstices between the particles interconnected via sintered compounds. This results in a particularly large contact area between the chemically active medium and the sintered compounds. As a result, the sintered compounds can be resolved particularly well. It can also contribute to the fact that sintered material is often very porous and / or has an open structure, so that the chemically active medium can flow between the individual particles and directly dissolve the sintered compounds.

The method described can be applied in particular to a large number of products at the same time. In particular, it is possible to speak of a batch process. All products of a construction process can be freed together from sintered powder.

In step a) of the process described, the product is at least partially wetted with a chemically active medium.

By wetting the product with the chemically active medium, it is to be understood that a surface of the product is brought into contact with the chemical active medium at least in the region of the powder agglomeration to be dissolved and / or removed. It can be wetted the entire surface of the product. It may also happen that powder agglomerations are to be dissolved and / or removed only in a part of the product, for example if the product has an inner edge and / or a channel. In particular, in such a case, the described method can also be carried out limited to this part of the product by wetting only this part of the product with the chemically active medium. In particular, the product can be wetted by immersing the product (completely or partially) in the chemically active medium.

In step b) of the described method, the at least one powder agglomeration with the chemically active medium is at least partially removed and / or dissolved.

The powder agglomeration can already be resolved and / or removed solely by contact of the chemically active medium with the powder agglomeration. Insofar, the implementation of step b) may amount to exposing the product or the powder agglomeration over a sufficiently long time to the chemically active medium.

In a preferred embodiment of the method, an ultrasound treatment of the product takes place after step b) and / or during at least part of step b).

Due to the ultrasonic treatment, the powder agglomeration can be dissolved and / or removed particularly efficiently. This may be due in particular to the fact that a compound to be separated is mechanically weakened by vibrations of the particles and / or of the product. Such a weakened compound can be more easily attacked by the chemically active medium.

For ultrasonic treatment, an ultrasound source can be arranged such that ultrasound is coupled into the product, the powder and / or the chemically active medium.

Ultrasound affects the product or powder as low frequency, low amplitude vibration.

The ultrasound treatment is preferably carried out at a time when the product is (still) wetted with the chemically active medium. In particular, the ultrasound treatment takes place at least during the entire duration of step b). Alternatively, however, the ultrasound treatment can also be carried out after the chemically active medium (in particular after step b)) has been removed. Also, for example, take place alternately ultrasonic treatment and wetting of the product with the chemically active medium.

The ultrasonic treatment is used, for example, for mechanical solutions of powder or powder agglomerations, which are already partially solved by the use of the chemically active medium. In addition, the ultrasound treatment also serves to transport the chemically active medium to the powder to be dissolved or to the powder agglomerations to be dissolved. Within interspaces of the powder act (due to the small channel cross-sections between the powder particles) on the chemically active medium strong capillary forces that severely limit the transport of the powder. However, this transport can be greatly improved by ultrasound.

• b) und/oder während zumindest eines Teils von Schritt b) der folgende Verfahrensschritt durchgeführt:
• c) Entfernen der gemäß Schritt b) zumindest teilweise gelösten mindestens einen Pulveragglomeration aus dem Produkt durch Spülen.

In a further preferred embodiment of the method is after step

• b) and / or during at least part of step b) the following method step is carried out:
• c) removing the at least partially dissolved according to step b) at least one powder agglomeration of the product by rinsing.

Rinsing may impart a powder agglomeration force which may contribute to the removal and / or dissolution of powder agglomeration.

In a further preferred embodiment of the method, a directed flushing jet with a predeterminable minimum pressure is used for flushing in step c).

The purge jet can be formed with any flowable medium. Preferably, the purge jet is formed with a liquid medium. The purge jet can be generated for example with a pump.

In a further preferred embodiment of the method, the rinsing in step c) takes place at a pressure of at least 50 bar.

In a further preferred embodiment of the method, the purge jet used in step c) comprises at least the chemically active medium used according to step b).

The powder agglomerations may be dissolved by the chemically active medium and / or released from the product. This detached particles can move through the chemically active medium. It may happen that such particles settle on the surface of the product and form a new powder agglomeration there. By flushing with the chemically active medium, in particular, a flow can be generated in the chemically active medium, by means of which such deposition can be prevented.

In a further preferred embodiment of the method, the rinsing in step c) is discontinuous.

In this embodiment, in particular, the pump can be operated in the pulse method. For example, it is possible to rinse for a short time and then leave the medium to rest. In the resting phases in particular sintered compounds can be better achieved by the chemically active medium. In particular, in the resting phase with ultrasound, a circulation of the chemically active medium can be effected on the powder.

In a further preferred embodiment of the method, in sections of step c), in which the rinsing is interrupted, an ultrasound treatment of the product takes place.

The described rinsing and the described ultrasound treatment can each be carried out individually or in combination (simultaneously, partially overlapping or successively). Both the rinsing and the ultrasound treatment result in a combination of mechanical disruption, for example of sintered compounds, with additional chemically active weakening by the chemically active medium.

As a further aspect, an apparatus for dissolving and / or removing at least one powder agglomeration of a product obtained by additive manufacturing and / or casting is presented, wherein the apparatus comprises at least one flushing element, via which the product can be acted upon with a flushing jet.

The particular advantages and design features of the method described above are applicable to the device described and transferable, and vice versa. The flushing element is preferably designed and set up for step c) of the described method.

In a preferred embodiment, the device further comprises at least one ultrasonic element for the ultrasonic action on the product.

The ultrasound element is preferably designed and set up for the ultrasound treatment after step b) and / or during at least part of step b) of the method described.

• 1: eine erste schematische Darstellung eines Verfahrens zum Auflösen und/oder Entfernen von mindestens einer Pulveragglomeration von einem durch additive Fertigung und/oder Guss erhaltenen Produkt,
• 2: eine zweite schematische Darstellung eines Teils des Verfahrens aus 1,
• 3: eine dritte schematische Darstellung eines Teils des Verfahrens aus den 1 und 2,
• 4: eine vierte schematische Darstellung eines Teils des Verfahrens aus den 1 bis 3, und
• 5: eine schematische Darstellung einer Vorrichtung zur Durchführung des Verfahrens aus den 1 bis 4.

Further details of the invention and embodiments, to which the invention is not limited, will be explained in more detail with reference to the drawings. Show it:

• 1 FIG. 1 shows a first schematic representation of a method for dissolving and / or removing at least one powder agglomeration of a product obtained by additive manufacturing and / or casting, FIG.
• 2 : a second schematic representation of a part of the method 1 .
• 3 FIG. 3 is a third schematic representation of part of the method of FIGS 1 and 2 .
• 4 FIG. 4 is a fourth schematic representation of part of the method of FIGS 1 to 3 , and
• 5 : a schematic representation of an apparatus for performing the method of the 1 to 4 ,

1. a) zumindest teilweises Benetzen des Produkts 12 mit einem chemisch aktiven Medium 4,
2. b) zumindest teilweises Auflösen und/oder Entfernen der mindestens einen Pulveragglomeration 14 mit dem chemischen aktiven Medium 4.

1 shows a schematic representation of a method for dissolving and / or removing at least one powder agglomeration 14 from a product obtained through additive manufacturing and / or casting 12 , The method will be described using the reference numerals of the following figures. The method comprises the following method steps:

1. a) at least partial wetting of the product 12 with a chemically active medium 4 .
2. b) at least partial dissolution and / or removal of the at least one powder agglomeration 14 with the chemical active medium 4 ,

• c) Entfernen der gemäß Schritt b) zumindest teilweise gelösten mindestens einen Pulveragglomeration 14 aus dem Produkt 12 durch Spülen.

Optionally, after step b) and / or during at least part of step b), the following step (represented by dashed lines) is carried out:

• c) removing the at least partially dissolved according to step b) at least one powder agglomeration 14 from the product 12 by rinsing.

2 shows a powder 2 with a plurality of particles 3 that have sintered connections 8th together to a powder agglomeration 14 are connected. The sintered connections 8th can through the chemically active medium 4 according to the method 1 be attacked and thereby solved.

3 shows a product 12 with a channel 13 in which there is a powder agglomeration to be removed 14 located. The product 12 is in 3 as well as in the following explained 4 shown only as an example. The product shown here 12 can be a section of a complex product or a complex assembly. In 3 It is shown that a purge jet 10 is used, a mechanical force in the form of a high purging pressure (as a directed beam) on the powder agglomeration 14 exercise the powder agglomeration 14 to dissolve and / or remove.

The chemically active medium 4 can with pressure (especially greater than 50 bar) in openings of the product 12 (as in the present example in the channel 13 ), whereby the chemical components of the sintered powder 2 attacked and / or disbanded. This can cause a mechanical force on the sintered connections 8th be exercised and the sintered connections 8th through the chemically active medium 4 be weakened. In that regard, the method described can be considered as a hybrid method, because the powder agglomeration 14 by a mechanical force and / or chemically dissolved and / or removed. Constant flushing of an internal contour can release dissolved powder 2 from the openings of the product 12 be rinsed and the powder to be removed 2 with fresh chemically active medium 4 be supplied.

In 4 is the product 12 with the channel 13 , the powder agglomeration 14 and the chemically active medium 4 out 3 shown. In the example of 4 an ultrasound treatment with an ultrasound element takes place 11 through which the powder agglomeration 14 is weakened.

This in 3 shown rinsing and the in 4 Ultrasonic treatment shown can be carried out individually or in combination (simultaneously, partially overlapping or sequentially).

5 shows a device 1 for dissolving and / or removing at least one (in the 2 to 4 shown) powder agglomeration 14 from a product obtained through additive manufacturing and / or casting 12 , The product 12 is in the example shown in a process chamber 5 by exposure to a laser beam 7 a laser 6 from a powder 2 obtained by additive manufacturing. The device 1 includes a flushing element 9 , about that with a purge jet 10 from the chemically active medium 4 on the product 12 can be acted upon. In addition, the device includes 1 an ultrasonic element 11 for the ultrasonic effect on the product 12 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• US 7285234 B2 [0001, 0002]

Claims (10)

Method for dissolving and / or removing at least one powder agglomeration (14) from a product (12) obtained by additive manufacturing and / or casting, comprising at least the following method steps: a) at least partially wetting the product (12) with a chemically active medium (4), b) at least partially dissolving and / or removing the at least one powder agglomeration (14) with the chemically active medium (4). Method according to Claim 1 wherein, after step b) and / or during at least part of step b), an ultrasound treatment of the product (12) takes place. Method according to one of the preceding claims, wherein after step b) and / or during at least part of step b) the following method step is carried out: c) removing the at least partially dissolved according to step b) at least one powder agglomeration (14) from the product (12) by rinsing. Method according to Claim 3 , wherein in step c) a directed rinsing jet (10) is used with a predetermined minimum pressure for rinsing. Method according to Claim 3 or 4 wherein the rinsing in step c) takes place at a pressure of at least 50 bar. Method according to one of Claims 3 or 4 in which the rinsing jet (10) used in step c) comprises at least the chemically active medium (4) used according to step b). Method according to one of Claims 3 to 6 wherein the rinsing in step c) is discontinuous. Method according to Claim 7 , wherein in sections of step c), in which the rinsing is interrupted, an ultrasonic treatment of the product (12) takes place. Device (1) for dissolving and / or removing at least one powder agglomeration (14) from a product (12) obtained by additive manufacturing and / or casting, wherein the device (1) comprises at least one scavenging element (9) via which one Purge jet (10) on the product (12) can be acted upon. Device (1) according to Claim 9 , further comprising at least one ultrasonic element (11) for the ultrasonic action on the product (12).

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