RU2835266C1 - Apparatus for layer-by-layer synthesis of three-dimensional articles from powder materials and overflow well for this apparatus - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: invention relates to powder metallurgy, in particular to devices for layer-by-layer synthesis of complex three-dimensional articles from powder materials, and can be used to make articles by selective laser melting (SLM) technology from metal powder materials or by selective laser sintering (SLS) technology from polymer powder materials. Apparatus for layer-by-layer synthesis of three-dimensional articles from powder materials includes a sealed working chamber, a laser radiation source, a structure well with a structure plate, a powder supply device, an application unit and an overflow well in the lower part of the working chamber. Overflow well comprises a header with an opening, a movable platform and a replaceable tank. Manifold contains a shut-off valve connected to the hole. Replaceable container contains a sealing valve and is made with possibility of being suspended from the movable platform. Movable platform is located between shutoff valve and sealing valve and is made with possibility of detachable connection with shutoff valve.

EFFECT: due to improved tightness of connection of removable tank and overflow well header, reduced powder losses during overflow well cleaning and increased quality of synthesized products.

10 cl, 6 dwg

Description

The group of inventions relates to devices for layer-by-layer synthesis of complex three-dimensional products from powder materials, in particular, it can be used for devices operating using selective laser melting (SLM) technology to create products from metallic powder materials or devices operating using selective laser sintering (SLS) technology to create products from polymer powder materials.

A method for the layer-by-layer synthesis of three-dimensional articles is known (see US Patent No. US4863538A, class B27N 3/00, 1986 ) using selective laser sintering of polymer powder. This method includes the following steps: applying a first portion of powder to the surface of a substrate; scanning a target with a directed energy beam over the surface of the substrate; sintering a first layer of the first portion of powder corresponding to a first region of the cross-section of the part by controlling the beam when the beam target is within the boundaries defined by said first region of the cross-section; applying a second portion of powder to the first sintered layer; scanning with a directed energy beam over the first sintered layer; sintering a second layer of a second powder portion corresponding to a second portion of the cross-section of the part by activating a beam when the target of the beam is within the boundaries defined by said second portion of the cross-section, wherein the first and second layers are joined during sintering of said second layer; and applying successive portions of powder to the previous sintered layers and sintering a layer of each subsequent part to obtain an article comprising a plurality of sintered layers.

A method for the layer-by-layer synthesis of three-dimensional articles is known (see German patent No. DE19649865C1, class B23K26/34, 1996 ) using selective laser melting of metal powder. In this method, the synthesis of three-dimensional articles is carried out by layer-by-layer build-up from a powdered metal material, in which several layers of powder are applied one after another, with each layer of powder heated to the melting temperature by a laser beam in a given region, which corresponds to the cross-section of the three-dimensional article being manufactured, as a result of which this layer of powder is attached to the underlying layer. The energy of the laser beam is selected in such a way that the powder of the metal material at the point of impact of the laser beam completely melts over the entire thickness of the layer, while the laser beam scans a given area of the layer of powder of the material in several tracks, in such a way that each subsequent track of the laser beam partially overlaps the previous track, while an atmosphere of protective gas is maintained above the zone of interaction of the laser beam with the powder of the metal material.

A device for implementing the described methods of layer-by-layer synthesis is known (see German patent No. DE102010020416A1, class B23K26/34, 2011 ). The device comprises: an application unit that applies powder material in the form of a layer; a build well containing a build platform that can move in the vertical direction and supports the synthesized article; a laser radiation source; a device for deflecting and focusing the laser beam; a dosing well including a piston for transporting powder upward and an overflow well. The device operates as follows: the application unit is moved along the work table and a powder layer of a given thickness is applied, wherein the powder is taken from the dosing well, and excess powder material enters the overflow well by further movement of the application unit. After this, the area corresponding to the cross-section of the synthesized product is irradiated with a laser beam, the powder material melts and then hardens in this area. Then the build platform is lowered and a new layer of powder is applied. To dose the powder, the piston of the dosing well rises upward, pushing out the required volume of powder for applying the next layer. The synthesis of the object is thus performed layer by layer. After the process is completed, the product is removed and subjected to subsequent processing and/or, if necessary, quality control.

A device is known for implementing a method of layer-by-layer synthesis by selective laser melting with a different method of dosing powder material (see German patent No. DE202023102863U1, class C04B35/622, 2023 ). The dosing device comprises: a powder buffer storage for loading into an application mechanism for repeated formation of a layer of powder raw material during synthesis and a dosing mechanism installed below the buffer storage and consisting of a housing containing a slot at the top for receiving powder and a slot at the bottom for feeding powder into the application mechanism, as well as a feed drum with longitudinal grooves capable of rotating inside the housing of the dosing mechanism, unloading a portion of powder in a volume equal to the volume of the said grooves of the feed roller. Otherwise, this device operates similarly to the previous one. The application mechanism applies a layer of powder to the build platform, and excess powder is discharged into an overflow well installed at the end of the stroke of the application mechanism. The build platform is then lowered and the process is repeated until the product is fully built.

A device is known for implementing a method of layer-by-layer synthesis by selective laser melting, where the application of a layer of powder material is performed in two directions, with each movement of the application mechanism, which makes it possible to increase the productivity of the synthesis process (see EU Patent No. EP4237179A1, class B22F12/50, 2023 ). In this case, the device contains two buffer storages with drum dispensers installed at the bottom of these storages so that a portion of the powder material is dosed into the application mechanism in both extreme positions, which makes it possible to eliminate idle strokes of the application mechanism and increase productivity. At the same time, such a dosing method requires the installation of two overflow wells for dumping excess powder in both extreme positions of the application mechanism.

A device for applying a layer of powder material is also known, which can be used in devices for layer-by-layer synthesis by the selective laser melting method, which allows for double-sided application of a layer of powder material in the presence of one buffer storage (see EU Patent No. EP2818305B1, class B29C64/153, 2013 ). The device is designed as follows: the body has two cavities for receiving powder, wherein said cavities are connected in the upper part of the device and have different discharge openings in the lower part of the device. The device is equipped with a slide valve, which can move, opening either one or the second discharge opening. When using said device in a device for layer-by-layer synthesis, the dosing mechanism unloads a portion of powder into both cavities of the application device, wherein the slide valve opens only one discharge opening. When the layer application is complete, the slide valve moves, opening the second discharge hole and closing the first, unloading a portion of powder into the working area, the device makes a reverse move, reapplying a layer of powder. The use of this device in a layer-by-layer synthesis device also requires the presence of two overflow wells for dumping excess powder.

The considered devices for layer-by-layer synthesis have significant disadvantages, namely, the great difficulty in cleaning the overflow well, due to the fact that the said well has a non-removable design, which reduces the productivity when cleaning the working area of the device and worsens the properties of the manufactured products, due to the ingress of used powder into the working area.

Various devices are known for layer-by-layer synthesis with easier cleaning of the overflow well from used powder.

The article describes a device for layer-by-layer synthesis of products, comprising a build well, inside of which there is a build platform with the possibility of reciprocating motion, a dosing well, inside of which there is a piston with the possibility of reciprocating motion, an application device, an optical system and an overflow well, which also has a piston with the possibility of reciprocating motion (see Laser Additive Technologies in Mechanical Engineering: a textbook / Grigoryants A.G., Shiganov I.N., Misyurov A.I., Tretyakov R.S.; ed. Grigoryants A.G. - M .: Publishing house of Bauman Moscow State Technical University, 2018. - 278 p. ). The device operates as follows: the application device takes the powder from the dosing well and transports the powder over the area of the working zone, applying a layer of the required thickness to the construction platform, while the excess powder is dumped into the overflow well. The optical system directs the laser beam, fusing or sintering the powder in the required areas, after which the next layer is applied, for which the piston of the dosing well moves upward by an amount determined by the required layer thickness, and the piston of the overflow well, on the contrary, moves downward, increasing the useful volume for receiving a new portion of powder. Upon completion of the process, the operator has the ability to gradually raise the piston of the overflow well and clean it using auxiliary devices, such as a vacuum cleaner.

The specified device facilitates cleaning of the overflow well, but has significant drawbacks, namely low cleaning performance and the need to use third-party equipment.

A device is known in which a build well, a dosing well and an overflow well are combined by a common frame in a single housing (see US Patent No. US11559940B2, class B29C64/259, 2023 ). The said device can be used in devices for layer-by-layer synthesis, and its design is such that it can be removed from the device for layer-by-layer synthesis entirely without disassembly upon completion of the synthesis process.

The use of the specified device facilitates the removal of the synthesized product, as well as the cleaning of the overflow well from the used powder, but has significant disadvantages:

1. The device is bulky, as it contains three wells at once, which forces the use of special lifting devices for its removal, which reduces the cleaning performance.

2. The overflow well in the device has a non-detachable design without moving parts, which also makes cleaning difficult.

3. When unloading, unused powder in the overflow well is exposed to air, which can degrade its quality or, in the case of metal powder, increase the risk of fire.

A device is known for the layer-by-layer synthesis of products by the selective laser melting method, which is the closest analogue of the installation and contains a frame and a laser radiation system located in it, including a scanning device, a laser emitter and a laser emitter fiber, a building module including a work table, a sealed working chamber installed on top of the work table, a building well and a dosing well with powder, a layer application system, an overflow well for excess applied powder and a control unit (see Russian Federation Patent for Invention No. 2801360 C1, class B23K26/342, 2023 ). In this device, the overflow well consists of two parts: a collector installed directly under the work table and a replaceable container, which is the closest analogue of the device of a removable container of the collector and is installed on the frame and connected to the collector by means of a flexible sealed connection, for example, a hose or a bellows, and the replaceable container has a shut-off valve in its composition. The device operates as follows: the process of layer-by-layer synthesis is carried out similarly to the devices described earlier, after which the operator closes the shut-off valve and disconnects the replaceable container with unused powder.

The advantages of this device are the convenience of cleaning the replaceable container separately from the layer-by-layer synthesis device, storage of unused powder under a protective atmosphere, and an increase in productivity due to the ability to install a replacement container without waiting for the previous one to be cleaned. However, it has disadvantages:

1. If the replaceable container overflows, some of the powder will remain in the hose, which will result in it spilling and being disposed of when the container is disconnected.

2. The replaceable container requires precise installation, as well as precise selection of the hose length for connection to the manifold to create a reliable hermetic connection. In case of frequent use, the degree of hermeticity may deteriorate due to the impossibility of precise installation of the replaceable container on the frame by the operator, which leads to an increase in the oxygen concentration in the working chamber of the device and deterioration in the quality of the synthesized products.

The technical problem of the group of inventions is the creation of an installation for the layer-by-layer synthesis of three-dimensional products from powder materials with a removable container for the overflow well collector, devoid of the disadvantages of the closest analogue.

The technical result of the group of inventions is a reduction in powder losses during cleaning of the overflow well and an increase in the quality of the synthesized products due to an improvement in the tightness of the connection of the removable container and the overflow well collector.

The essence of the claimed invention is that in an installation for layer-by-layer synthesis of three-dimensional articles from powder materials, comprising a sealed working chamber; a laser radiation source; a build well with a build plate; a powder feed device; an application unit; an overflow well in the lower part of the working chamber; the overflow well contains a manifold with an opening, a movable platform and a replaceable container; wherein the manifold contains a shut-off valve connected to the opening; the replaceable container contains a sealing valve and is designed with the possibility of being suspended from the movable platform; the movable platform is located between the shut-off valve and the sealing valve and is designed with the possibility of a detachable connection with the shut-off valve.

The essence of the claimed invention also consists in the fact that the overflow well, containing a collector with an opening, contains a movable platform and a replaceable container; the collector contains a shut-off valve connected to the opening; the replaceable container contains a sealing valve and is designed with the possibility of being suspended from the movable platform; the movable platform is located between the shut-off valve and the sealing valve and is designed with the possibility of a detachable connection with the shut-off valve.

The essence is explained as follows.

The specified technical result is ensured by the fact that the device for layer-by-layer synthesis is equipped with an overflow well consisting of a collector and a replaceable container, wherein the collector is equipped with a movable platform capable of performing reciprocating movements, for example, using a screw-nut transmission, on which a replaceable container is installed and pressed against the collector due to the movement of the platform, rigidly fixing the replaceable container in space, and also creating a reliable hermetic connection and reducing powder losses during cleaning, due to the absence of a long flexible connection. The collector may have the ability to install several replaceable containers. Depending on the method of dosing the powder, the device for layer-by-layer synthesis can be equipped with one or two overflow wells of the specified design.

The claimed group of inventions is illustrated by figures 1-6, which show:

- Fig. 1 - design of the installation with a dosing method from a dosing well;

- Fig. 2 - design of an overflow well with two removable tanks;

- Fig. 3 - shape of the movable platform;

- Fig. 4 - design of the installation with a dosing method using one drum dosing unit and one-sided powder application;

- Fig. 5 - design of the installation with a dosing method using one drum dosing unit and double-sided powder application;

- Fig. 6 - design of the installation with a dosing method using two drum dosing units.

In figures 1-6 positions are shown:

1 - working chamber;

2 - laser radiation source;

3 - optical fiber;

4 - scanning device;

5 - transparent window;

6 - construction well;

7 - construction plate;

8 - product;

9 - dosing well;

10 - piston;

11 - powder;

12 - collector;

13 - replaceable container;

14 - excess powder;

15 - movable platform;

16 - application unit;

17 - squeegee;

18 - shut-off valve;

19 - sealing valve;

20 - support flange;

21 - bolt;

22 - powder buffer storage;

23 - dosing device body;

24 - drum;

25 - mine;

26 - drum dispenser;

27, 28 - cavity;

29, 30 - gate valve;

31 - overflow well;

32 - additional overflow well;

33 - additional powder buffer storage;

34 - additional drum dispenser;

35 - additional shaft;

36, 37 - open cavity;

38 - extreme position of the application unit.

The claimed installation includes (Fig. 1) a frame (not shown conditionally), on which a sealed working chamber 1 is installed, a laser radiation source 2 , optically connected, for example, by means of an optical fiber 3 , with a scanning device 4 , intended for directing and focusing the laser beam. The laser beam has the ability to enter the working chamber 1 through a transparent window 5 , installed in the upper part of the working chamber 1. In the lower part of the working chamber 1 , a build well 6 is installed, inside which a build plate 7 with the possibility of reciprocating movement is installed, on which the synthesis of the product 8 takes place; a dosing well 9 , inside which a piston 10 is installed with the possibility of reciprocating movement, intended for storing and dosing powder 11 during the application of a layer; and also an overflow well intended for collecting excess powder, consisting of a collector 12 and one or more replaceable containers 13 , into which excess powder 14 falls, wherein the replaceable containers 13 are installed on movable platforms 15 , having the ability to perform reciprocating movements to create a hermetic connection with the collector 12. An application unit 16 is also installed inside the working chamber 1 , having the ability to move along the working surface and intended for applying the first and subsequent layers to the build plate 7. The application device contains a squeegee 17 , directly forming a powder layer of a given thickness.

The overflow well may have one or more replaceable containers.13. Below is a more detailed description of the variant with two replaceable tanks (Fig. 2). The overflow well includes a collector12, which divides the volume of excess powder into two parts, at the bottom of which two shut-off valves are installed18for sealing the working chamber1when cleaning the overflow well. The specified valves18have support flanges20,into the holes of which bolts are inserted21, on which movable platforms are suspended15. Replaceable containers13also include sealing valves19for sealing powder inside replaceable containers13when removed from the layer-by-layer synthesis unit. Sealing valves19have flanges that allow the containers to be suspended from movable platforms15. In Fig. 2 the right replaceable container13is in its original state, and between the flange of its sealing valve19and a support flange20cut-off valves18collector12there is a guaranteed gapz, and the left is a replaceable container13is in the working position in which the flange of its sealing valve19pressed against the support flange20cut-off valves18collector. For better sealing of the specified connection, sealing elements can be used, such as gaskets or cords made of elastic materials (not shown).

The movable platform 15 of the collector has a shape with an open groove for the convenience of installing removable containers (Fig. 3).

Before the start of the synthesis process, empty replaceable containers 13 of the overflow well are installed in the device. The replaceable containers 13 are suspended on movable platforms 15 . Then, by rotating the bolts 21, the platforms 15 move upward, hermetically pressing the replaceable containers 13 to the collector 12 . The required volume of powder is loaded into the dosing well 9 , after which the device is ready for operation. The working cycle begins with filling the working chamber 1 with an inert gas, after which the synthesis process begins. The piston 16 of the dosing well 9 moves upward, feeding the volume of powder necessary to form a layer of the desired thickness, then the application unit 16 , moving along the working area, applies the first layer of powder to the building plate 7 using a squeegee 17 . Excess powder is transported into the replaceable containers 13 of the overflow well. After this, the laser beam formed in the source 2 and directed by the scanning device 4 through the window 5 processes the powder located on the build plate 7 in the zone corresponding to the cross-section of the synthesized product. Upon completion of the layer processing, the build plate 7 moves to a position lower than the initial one by one or more movements by an amount equal to the layer thickness, the piston 10 of the dosing well 9 moves higher, feeding the next volume of powder for applying a new layer and the synthesis process is repeated. Upon completion of the synthesis process, the shut-off valves 18 of the overflow well are closed, by rotating the bolts 21 of the platform 15 they move downwards. Then the replaceable containers 13 are removed from the device for recycling or sifting the accumulated powder for further use.

In case of overflow of replaceable containers 13 , some of the powder will remain in collector 12. The remaining powder can be removed when installing replaceable containers 13 , the remaining powder will fall under the action of force into the replaceable containers when the shut-off valves 18 are opened.

It is also permissible to replace the containers 13 during the synthesis process, since the collector 12 is capable of accumulating a certain volume of powder. For this purpose, the overflow well can be equipped with sensors that determine the critical volume of powder in the collector 12. In this case, the volume of the overflow well can be made smaller than that required for the synthesis of the product at the maximum stroke of the construction platform.

The required volume of the overflow well, which does not require cleaning during the synthesis process, can be determined using the following formula:

- volume of the overflow well;

- volume of the construction well.

The claimed installation can be implemented in a design with a drum powder dispenser (Fig. 4). In this case, the dosing well is not installed, and the powder 11 is dosed from a powder buffer storage 22 installed on the dosing device, which in turn is installed on the working chamber 1. The dosing device includes a housing 23 , inside which there is a drum 24 with grooves with the ability to rotate around its axis. A shaft 25 located inside the working chamber 1 is connected to the dosing device. The housing 23 has two slots - an upper one connected to the buffer storage 22 , and a lower one connected to the shaft 25. The application unit is located inside the working chamber 1 and is similar in design to that considered earlier. At the bottom of the chamber, a construction well 6 with a construction plate 7 and an overflow well having a design similar to that considered earlier are installed.

The installation operates as follows. When rotating, the doser drum 24 transports a dose of powder from the buffer storage 22 to the body's discharge slit, the powder rolls down the shaft 25 under the action of gravity and falls in front of the application device. The application device moves and applies the specified volume of powder to the construction plate. Excess powder is discharged into the overflow well. Otherwise, the installation operates similarly to the previously considered variant.

Equipping with a drum dispenser allows to reduce the application time, which increases the productivity of work, and also to reduce the unevenness of the powder properties, which occurs in the dosing well due to the pressure of the upper layers of powder on the lower ones.

The claimed installation can be implemented in a design with a drum powder dispenser and double-sided application of the layer (Fig. 5). In this case, dosing is also performed by a drum dispenser 26 from a buffer storage 22 through a shaft 25 , and the application unit 16 has in its design two cavities 27 , 28 , which are connected from above the application unit 16 , wherein each cavity has a slide valve 29 , 30 , which, when opened, allow the corresponding cavities to be emptied. The device also has a construction well 6 with a construction plate 7 , an overflow well 31 and, in addition to it, a second additional overflow well 32 , installed on the opposite side from the construction well 6. Both overflow wells have a design similar to that considered earlier.

The installation operates as follows. The drum dispenser 26 unloads a portion of powder from the buffer storage 22 through the shaft 25 into the application unit 16 , where the unloaded dose of powder is divided into two equal parts, each of which enters cavities 27 and 28 , respectively. In the initial position, the slide gate 30 of the cavity 28 opens, for example, by means of a separate drive, and the powder from the said cavity enters the working surface. The application unit 16 moves along the working surface, applying a layer of powder to the building plate 7 and dumping excess powder into the first overflow well 31. Then, the process of processing the powder layer with laser radiation and lowering the building plate 7 by an amount equal to the thickness of the layer occurs. The slide gate 29 of the cavity 27 of the application unit 16 opens, for example, by means of a separate drive, and the powder stored in the said cavity enters the working surface. The application unit 16 moves to the initial position, repeatedly applying a layer to the construction plate 7 , while the excess powder is discharged into the second additional overflow well 32. After this, the next layer of the product is processed, after which the process is repeated. Otherwise, the installation operates similarly to the previously considered version.

This design of the application unit allows for double-sided powder application, which increases the productivity of the synthesis process by reducing the time it takes to apply the layer.

The required volume of each overflow well in this case can be determined using the following formula:

- volume of the overflow well;

- volume of the construction well.

The claimed installation can be made with a different design of double-sided application (Fig. 6). In this case, a second additional buffer storage 33 is installed on the working chamber 1 in addition to the first powder buffer storage 22 , wherein each buffer storage is equipped with a drum dispenser 26 , 34 and a shaft for feeding powder into the working chamber 25 , 35 , and the application unit 16 has two open cavities 36 , 37 that are not connected to each other. A construction well 6 with a construction plate 7 and two overflow wells 31 , 32 of the previously considered design are also installed in the device.

The installation operates as follows. At the start of the device operation, the application unit 16 is in the initial position. The dispenser 26 unloads a portion of powder from the first buffer storage 22 through the shaft 25 and the open cavity of the application unit 36 onto the working surface. The application unit 16 moves to the extreme position 38 , applying a layer of powder onto the build plate 7 , dumping excess powder into the overflow well 31. Then the process of processing the powder layer with laser radiation and the subsequent lowering of the build plate 7 downwards by an amount equal to the thickness of the layer occurs. At the next stage, the additional drum dispenser 34 unloads the powder from the second additional buffer storage 33 through the additional shaft 35 and the open cavity 37 onto the working surface. The application unit 16 moves to its original position, applying a new layer of powder and dumping the excess into the second additional overflow well 32 , after which the powder is processed on the construction platform and the process is repeated.

The addition of a second buffer storage allows for dual-sided application with increased powder storage capacity.

Claims (24)

1. An installation for the layer-by-layer synthesis of three-dimensional products from powder materials, containing: sealed working chamber; laser radiation source; construction well with construction slab; powder feed device; application unit; overflow well in the lower part of the working chamber, characterized in that the overflow well contains a collector with an opening, a movable platform and a replaceable container, while the manifold contains a shut-off valve connected to the opening; the replaceable container contains a sealing valve and is designed to be suspended from a movable platform; the movable platform is located between the shut-off valve and the sealing valve and is designed with the possibility of detachable connection with the shut-off valve. 2. The installation according to item 1, characterized in that the movable platform is made in the shape of a horseshoe. 3. The installation according to item 1, characterized in that the overflow well contains an additional movable platform and an additional replaceable container, wherein the collector contains an additional opening equipped with a shut-off valve, and the additional replaceable container is designed with the possibility of being suspended from an additional movable platform designed with the possibility of a detachable connection with the shut-off valve of the additional opening. 4. The installation according to item 1, characterized in that the powder feed device is made in the form of a dosing well with a piston. 5. The installation according to item 1, characterized in that the powder feed device is made in the form of a drum dispenser with a shaft. 6. The installation according to item 5, characterized in that it contains an additional overflow well, and the application unit contains two cavities, each of which is equipped with a gate valve. 7. The installation according to item 5, characterized in that it contains an additional overflow well and an additional powder feed device made in the form of a drum dispenser with a shaft, wherein the application unit contains two open cavities. 8. An overflow well of a plant for the layer-by-layer synthesis of three-dimensional products from powder materials, comprising a collector with an opening, characterized in that it comprises a movable platform and a replaceable container, wherein the manifold contains a shut-off valve connected to the opening; the replaceable container contains a sealing valve and is designed to be suspended from a movable platform; the movable platform is located between the shut-off valve and the sealing valve and is designed with the possibility of detachable connection with the shut-off valve. 9. An overflow well according to item 8, characterized in that the movable platform is made in the shape of a horseshoe. 10. An overflow well according to item 8, characterized in that it contains an additional movable platform and an additional replaceable container, the collector contains an additional opening equipped with a shut-off valve, wherein the additional replaceable container is designed with the possibility of being suspended from an additional movable platform designed with the possibility of a detachable connection with the shut-off valve of the additional opening.