WO2019020865A1

WO2019020865A1 - Powder removal and recycling

Info

Publication number: WO2019020865A1
Application number: PCT/FI2018/050525
Authority: WO
Inventors: Pasi PIISPA; Sebastian MATHEWS; Hamid Roozbahani; Antti Salminen
Original assignee: Lappeenrannan Teknillinen Yliopisto
Priority date: 2017-07-24
Filing date: 2018-07-02
Publication date: 2019-01-31
Also published as: FI20175699A1

Abstract

A method wherein an object is formed by additive manufacturing in a building chamber, free powder is removed from the building chamber through a discharge channel, the removed free powder in conveyed to a recycling assembly being in flow connection with the discharge channel, and wherein the removed free powder is recycled by causing a powder flow from the recycling assembly to the building chamber. An apparatus and a building chamber are further included.

Description

POWDER REMOVAL AND RECYCLING

TECHNICAL FIELD

The present invention generally relates to additive manufacturing, also known as three-dimensional printing. The invention relates particularly, though not exclusively, to removing and recycling powder in additive manufacturing.

BACKGROUND ART

This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

Additive manufacturing (AM), also known as three-dimensional printing, is a flexible and fast technique for forming three-dimensional physical objects. Additive manufacturing is a computer-controlled process. The physical object is formed based on an electronic data source, such as a digital 3D model, or a computer aided design (CAD) file. The three-dimensional design is divided into layers by the computer. An additive manufacturing apparatus is then used to build the physical object layer by layer.

By additive manufacturing, three-dimensional objects can be formed from powder. Generally, powder is supplied into a building chamber, after which the powder is selectively joined together to form regions of solid material from powder, or a layer of solid material from powder. By repeating the supplying and selective joining steps, layers are added upon each other until a three-dimensional physical object of solid regions of joined powder is formed. Free powder, i.e. powder that was not selectively joined together, or exploited, to form the solid object, surrounds the formed solid object in the building chamber.

Once the solid object has been formed, said object has to be removed from the building chamber, and the object and preferably the building chamber need to be cleaned from the free powder. Conventionally, the free powder is removed from the building chamber and the outer surface of the object manually, for example with a brush or a handheld vacuum or blower. Removing the free powder from the building chamber with the manual methods requires first removing the chamber or portions of the chamber, such as the building platform, from the additive manufacturing apparatus.

US 2004/0084814 A1 discloses a more sophisticated powder removal method and a powder removal system for a three-dimensional object fabricator. US 2004/0084814 A1 improves the conventional solutions by providing a vacuum generator to remove unbound free powder from a building chamber. The free powder is removed from the building chamber into a storage chamber. A removable receptacle collecting the powder therein is removed from the storage chamber via a door and the powder is poured into a source chamber for reuse. An object of the present invention is to provide an improvement in handling free powder in additive manufacturing, or at least to provide a new technical alternative for existing technology.

SUMMARY

According to a first aspect of the invention there is provided a method comprising: forming an object by additive manufacturing in a building chamber;

removing free powder from the building chamber through a discharge channel; conveying the removed free powder to a recycling assembly being in flow connection with the discharge channel; and

recycling the removed free powder, said recycling comprising causing a powder flow from the recycling assembly to the building chamber. The powder flow from the recycling assembly to the building chamber need not be a continuous flow, but there may be stops and/or temporary storage and/or process steps on the way to the building chamber. In certain embodiments, recycling the removed free powder comprises defining from the removed free powder a recyclable portion.

In certain embodiments, defining from the removed free powder a recyclable portion is based on particle size. In certain embodiments, defining from the removed free powder a recyclable portion comprises passing the removed free powder to a through flow separator. In certain embodiments, defining from the removed free powder a recyclable portion comprises sieving the free powder. In certain embodiments, sieving the removed free powder comprises vibrating a sieve.

In certain embodiments, defining from the removed free powder a recyclable portion comprises separating from the removed free powder a waste portion. In certain embodiments the separating comprises sieving. In certain embodiments, separating from the removed free powder a waste portion comprises collecting the waste portion. In certain embodiments, separating from the removed free powder a waste portion comprises discarding the waste portion.

In certain embodiments, defining from the removed free powder a recyclable portion comprises feeding the removed free powder through an inlet, separating the recyclable portion from the waste portion, and conveying the recyclable portion through a first outlet, and conveying the waste portion through a second outlet.

In certain embodiments, recycling the removed free powder comprises forming at least a portion of an object by additive manufacturing with the removed free powder. In certain embodiments, recycling the removed free powder comprises combining removed free powder with unused powder before forming at least a portion of an object by additive manufacturing with the mixture of removed free powder and unused powder. In certain embodiments, recycling the removed free powder further comprises feeding removed free powder, or the mixture of removed free powder and unused powder, into the building chamber. In this context, unused powder refers to powder that has not been in a building chamber while an object has been formed by additive manufacturing in the building chamber. In this context free powder refers to powder that does not form a part of the object formed in the building chamber by additive manufacturing.

In certain embodiments, removing free powder from the building chamber comprises providing a gas flow into the building chamber through gas inlets.

In certain embodiments, removing free powder from the building chamber comprises controlling the gas flow through the gas inlets by more than one valve. In certain embodiments, controlling the gas flow through the gas inlets by more than one valve comprises separately controlling more than one group of gas inlets. Preferably, the gas inlets comprises, or form, four groups of gas inlets. In another preferred embodiment, the gas inlets form at least 5 groups of gas inlets, for example from 5 to 20 groups of gas inlets, or from 5 to 15 groups of gas inlets. In certain embodiments, the gas inlets form 12 groups of gas inlets. In certain embodiments, controlling the gas flow through the gas inlets by more than one valve comprises controlling the gas flow through each gas inlet by a respective valve. In certain embodiments, the incoming gas flow into the building chamber via a plurality of groups of gas inlets is controlled so that the gas flow via the inlets belonging to the same group is controlled by the group's own valve.

In certain embodiments, the flow rate through the gas inlets is controlled by controlling the more than one valve. In certain embodiments, controlling the gas flow through the gas inlets by more than one valve comprises opening and closing the more than one valve. In certain embodiments, controlling the gas flow through the gas inlets by more than one valve comprises independently controlling each of the more than one valve. In certain embodiments, controlling the gas flow through the gas inlets by more than one valve comprises opening and closing the more than one valve independently of each other.

In certain embodiments, removing free powder from the building chamber comprises controlling the flow rate through the gas inlets. In certain embodiments, controlling the flow rate through the gas inlets comprises controlling a gas source. In certain embodiments, controlling the gas flow or the flow rate through the gas inlets comprises controlling the pressure of the gas from the gas source.

In certain embodiments, the removing free powder from the building chamber comprises providing a gas flow from a pressurized gas source, or a high-pressure gas source, into the building chamber through gas inlets. Gas flow from the pressurized gas source, or high-pressure gas source, into the building chamber through gas inlets may be provided via a gas inlet circuit in flow connection with the at least one gas source and the gas inlets. In certain embodiments the gas inlet circuit comprises conduits and valves and optionally a control unit configured to control the gas flow in the gas inlet circuit.

In certain embodiments, removing free powder from the building chamber comprises altering the gas flow in the building chamber. In certain embodiments, altering the gas flow in the building chamber comprises controlling the gas flow through the gas inlets. In certain embodiments, altering the gas flow in the building chamber controlling the gas inlets.

In certain embodiments, controlling the gas flow through the gas inlets comprises controlling each group of gas inlet independently from the other group(s) of gas inlets. Controlling each group of gas inlets independently from the other groups of gas inlets comprises stopping, starting, and/or adjusting (for example velocity or pressure) the gas flow through the gas inlets of a certain group of gas inlets without affecting the gas flow through the gas inlets of the other gas inlet group(s). Independently controlling each group of gas inlets allows altering (in magnitude and/or directions) the gas flow inside the building chamber during the powder removal step. Further, independently controlling each group of gas inlets allows directing gas flow towards a certain location(s) in the building chamber at a certain timepoint. Independently controlling each group of gas inlets enhances the powder removal effect, particularly from (open) cavities on the surface of the object formed in the building chamber.

In certain embodiments, the gas inlets are nozzles. In certain embodiments, the gas inlets prevent reverse flow. "Reverse flow" refers in this disclosure to flow (gas and/or powder flow) from the building chamber towards the gas source.

In certain embodiments, removing free powder from the building chamber comprises providing a suction from the building chamber through the discharge channel.

In certain embodiments, the method comprises providing the suction through a receptacle being in flow connection with the discharge channel. In certain embodiments, the receptacle is a chamber configured to collect the removed free powder from the building chamber. In certain embodiments, the receptacle comprises an outlet. In certain embodiments, removing free powder from the building chamber comprises changing the pressure inside the building chamber. In certain embodiments, changing the pressure inside the building chamber comprises opening and closing the flow connection between the discharge channel and the building chamber when a suction is provided from the building chamber through the discharge channel. In certain embodiments, method comprises repeating the opening and closing steps.

Opening the flow connection between the discharge channel and the building chamber when a suction is provided from the building chamber through the discharge channel creates a pressure drop inside the building chamber. The flow connection between the discharge channel and the building chamber when a suction is provided from the building chamber through the discharge channel may be kept open for various time periods. Repeating the opening and closing step creates temporary pressure drops inside the building chamber resulting in alterations in the gas and powder flow (directions and magnitude) inside the building chamber. In certain embodiments, the powder removal step comprises providing a gas flow into the building chamber while repeating the opening and closing steps, i.e. positive pressure gas flow is provided into the building chamber while a temporary pressure drop is created. The alterations in the flow in the building chamber and around the formed object enhances the powder removal effect, particularly from cavities in the surface of the formed object.

In certain embodiments, the method comprises first providing a gas flow into the building chamber through gas inlets; and then, without providing a gas flow into the building chamber through gas inlets, providing a suction from the building chamber through the discharge channel. The method optionally further comprises repeating the steps of first providing a gas flow into the building chamber through gas inlets; and then, without providing a gas flow into the building chamber through gas inlets, providing a suction from the building chamber through the discharge channel. In other words, in certain embodiments, the method comprises first providing a gas flow into the building chamber to dislodge and/or move free powder in the building chamber, then stopping the gas flow into the building chamber, and once the air flow into the building chamber has been stopped, providing a suction from the building chamber through the discharge channel to remove free powder from the building chamber. By providing the air flow and suction sequentially, free powder removal from for example cavities in the surface of the formed object can be improved. Optionally, the sequentially performed steps of providing a gas flow and providing a suction are repeated. Repeating said steps further enhances the removal of free powder to a degree that the formed object can be considered substantially free of free powder. In certain embodiments, the sequence is repeated if the amount of free powder is above a predetermined value. If the amount of free powder is at or below a predetermined value, enough free powder has been removed from the building chamber to take out the formed object from the building chamber. In certain embodiments, providing a gas flow into the building chamber through gas inlets and providing a suction from the building chamber through the discharge channel are controlled independently of each other.

In certain embodiments, recycling the removed free powder comprises conveying the removed free powder from a receptacle in flow connection with the discharge channel to the defining assembly. In certain embodiments, recycling the removed free powder comprises conveying the removed free powder from a receptacle in flow connection with the discharge channel to the defining assembly with a pump. In certain embodiments, recycling the removed free powder comprises conveying the removed free powder to the building chamber with a pump. In certain embodiments, recycling the removed free powder comprises feeding the removed free powder into the building chamber. In certain embodiments, recycling the removed free powder comprises mixing the removed free powder with unused powder, and feeding the mixture of removed free powder and unused powder into the building chamber.

In certain embodiments, the free powder is metal powder. In certain embodiments, the additive manufacturing comprises selective laser melting.

In certain embodiments, the additive manufacturing is powder bed fusion with selective laser melting.

In certain embodiments, the removed free powder is conveyed with a first powder pump and the recyclable portion with a second powder pump.

In certain embodiments, the method is automatic. In this context automatic means that powder is being conveyed with an apparatus without manually transferring the powder during the method of the first aspect. In this context, manually comprises steps performed with hand-held tools or operator driven vehicles.

In certain embodiments, the method comprises keeping the top of the building chamber closed while removing free powder from the building chamber. In certain embodiments, the method comprises keeping the top of the building chamber open while forming an object by additive manufacturing in the building chamber.

In certain embodiments, the method comprises lowering a building platform while forming the object by additive manufacturing. The lowering may be stepwise lowering. The lowering may be continuous lowering. In certain embodiments, the method comprises lowering the building platform before removing free powder from the building chamber. In certain embodiments, the discharge channel is attached to a side wall of the building chamber, preferably to a lower portion of a side wall of the building chamber. In such embodiments, the powder removal step can only be performed when the building platform is in a lower position, i.e. when the building platform is below the building chamber side opening or mouth of the discharge channel.

In certain embodiments, the discharge channel is positioned at a level that is lower than the level of each building chamber gas inlet. In certain example embodiments, the lowering of the building platform reveals the mouth of the discharge channel. In certain embodiments, the building chamber is vertically divided into a three dimensional printing portion and a powder removal portion below the three dimensional printing portion. In certain embodiments, the free powder is recycled to a building chamber separate from the building chamber from which the free powder originated.

According to a second aspect of the invention there is provided an apparatus comprising:

a building chamber for additive manufacturing;

a discharge channel in flow connection with the building chamber;

a recycling assembly in flow connection with the discharge channel;

and means for causing a flow from the recycling assembly to the building chamber for recycling the removed free powder.

In certain embodiments, the recycling assembly comprises a defining assembly configured to define from the removed free powder a recyclable portion. In certain embodiments, the defining assembly is configured to define from the free powder a recyclable portion based on particle size. In certain embodiments, the defining assembly comprises a flow through separator. In certain embodiments, the through flow separator is a sieve. In certain embodiments, the defining assembly comprises at least one motor configured to move at least a portion of the defining assembly. In certain embodiments, the defining assembly comprises at least one motor configured to vibrate at least a portion of the defining assembly. In certain embodiments, the at least a portion of the defining assembly is the flow through separator.

In certain embodiments, the defining assembly comprises an inlet for removed free powder, and a first outlet configured to convey the recyclable portion, and a second outlet configured to convey the waste portion. In certain embodiments, the first outlet is formed by a flow through separator. In certain embodiments, the defining assembly comprises means for removing from the defining assembly the waste portion. In certain embodiments, the means for removing from the defining assembly the waste portion comprises an outlet. In certain embodiments, the means for removing from the defining assembly the waste portion comprises a conduit.

In certain embodiments, the recycling assembly comprises a pump positioned above the defining assembly, the pump being configured to convey the removed free powder to the defining assembly. In certain embodiments, the apparatus comprises a receptacle configured to receive the recyclable portion. In certain embodiments, receptacle configured to receive the recyclable portion is positioned below the defining assembly. In certain embodiments, the apparatus comprises a receptacle configured to receive the waste portion.

In certain embodiments, the building chamber comprises gas inlets. In certain embodiments, the diameters of the gas inlets are no more than 5 mm. In certain embodiments, the diameters of the gas inlets are from 1 mm to 4 mm, preferably from 2 mm to 3 mm. Small diameters of the air inlets provides a high-speed (high- velocity) gas flow into the building chamber through the gas inlets.

In certain embodiments, the apparatus comprises more than one valve configured to control the gas flow through the gas inlets. In certain embodiments, the more than one valve is configured to separately control more than one group of gas inlets. Preferably, the apparatus comprises four groups of nozzles. In certain embodiments, each gas inlet is configured to be controlled by a respective valve. In certain embodiments, the more than valve is configured to be controlled independently from the other valve or valves. In certain embodiments, the more than one valve is configured to control the flow rate through the gas inlets.

In certain embodiments, the gas inlets are arranged on at least one wall of the building chamber. In certain embodiments, the gas inlets are arranged on one, two, three, four, five, or six walls of the building chamber. In certain embodiments, each wall on which nozzles are arranged forms a group of gas inlets. In certain other embodiments, each wall on which nozzles are arranged comprises two groups of gas inlets. In certain embodiments, the walls of the building chamber comprises the building platform and the top of the building chamber.

In certain embodiments, the gas inlets are in connection with at least one gas source. In certain embodiments, the gas source is a pressurized air source or high- pressure gas source. In certain embodiments, the gas of the gas source has a pressure above the atmospheric pressure. In an embodiment, gas entering and exiting the gas inlets has a pressure above the atmospheric pressure. In an embodiment, the inlet pressure of the gas inlet circuit is selected from the range from 5 to 10 bars, preferably from 7 to 9 bars. In a preferred embodiment, the inlet pressure of the gas inlet circuit is about 8 bars. The inlet pressure of the gas inlet circuit is the pressure at which the gas enters the gas inlet circuit, or the pressure at which the gas exits the gas source. In certain embodiments, the gas source is a nitrogen source. In certain embodiments, the apparatus comprises at least one valve configured to control the pressure of the gas from the gas source.

In certain embodiments, the gas inlets are configured to prevent reverse flow. "Reverse flow" refers in this disclosure to flow (gas and/or powder flow) from the building chamber towards the gas source. In certain embodiments, the gas inlets are configured to allow a flow only in the direction from the gas source and into the building chamber. Preventing reverse flow protects the gas source and the gas inlet circuit from contamination, such as powder contamination. This prevents, for example, used powder from entering the building chamber along with gas flow for removing free powder, which prevents powder contamination from deteriorating the powder removal effect. Further, the need of maintenance and cleanse of the gas inlet circuit is reduced.

In certain embodiments, the gas inlets are nozzles. In certain embodiments the inner diameter of the nozzles, i.e. the diameter of the space through which gas travels inside the nozzles, decreases towards the outlet end of the nozzles. In other words, the space through which gas travels inside the nozzles has a cone-like shape (or more specifically, said space has the shape of an open ended truncated cone), where gas from the gas source enters the nozzle from the wider end and exits through the narrower end. This structure of the nozzles provides a high-speed (high- velocity) gas flow into the building chamber through the nozzles.

In certain embodiments, the apparatus comprises a vacuum source configured to provide a suction from the building chamber through the discharge channel. In certain embodiments, the vacuum source is configured to provide the suction through a receptacle being in flow connection with the discharge channel. In certain embodiments, the discharge channel is attached to an inlet of the receptacle.

In certain embodiments, the receptacle being in flow connection with the discharge channel is configured to receive the removed free powder. In certain embodiments, the receptacle comprises an outlet in connection with the recycling assembly. In certain embodiments, the receptacle comprises an outlet in connection with a vacuum source or a pump. In certain embodiments, the receptacle being in flow connection with the discharge channel is positioned between the discharge channel and the vacuum source. In certain embodiments, the apparatus comprises a valve configured to open and close the flow connection between the discharge channel and the building chamber. In certain embodiments, the means for causing a powder flow from the recycling assembly to the building chamber comprises a pump and a conduit. In certain embodiments, the pump is in connection with a vacuum source. In certain embodiments, the recycling assembly to the building chamber comprises a suction device and a conduit.

In certain embodiments, the apparatus comprises one powder pump. In certain embodiments, the powder pump is in connection with an external vacuum source. In certain embodiments, the vacuum source of the powder pump is a separate vacuum source in connection with the powder pump. In certain embodiments, the powder pump comprises a powder receptacle.

In certain embodiments, the top of the building chamber is openable and closable. In certain embodiments, the top of the building chamber comprises a lid, the lid being configured to be opened and closed. In certain embodiments, the building chamber comprises a door for removing the formed object. In certain embodiment, the door is arranged in a sidewall of the building chamber. In certain embodiments, the door is arranged to be lifted and lowered, i.e. to be openable and closable in the vertical direction. In certain embodiments, the building chamber comprises a building platform. In certain embodiments, the discharge channel is attached to the building platform. In certain embodiments the building platform is configured to be movable in the vertical direction.

In certain embodiments, the discharge channel is (fixedly) attached to a side wall of the building chamber. In certain embodiments, the discharge channel is attached to a side wall comprising gas inlets, i.e. at least a portion of the gas inlets and the discharge channel are arranged in the same wall of the building chamber.

In certain embodiments, the air inlets are arranged in a certain portion of the building chamber wall(s). Preferably, the air inlets are arranged in the upper portion of the building chamber, i.e. in the upper portion of the side walls and/or top of the building chamber. In certain embodiments, the discharge channel is attached to the building chamber below the portion comprising the gas inlets, preferably to a side wall of the building chamber.

In certain embodiments, the apparatus comprises at least one sensor configured to monitor the amount of free powder in the building chamber.

In certain embodiments, the apparatus comprises a control unit configured to control the apparatus to perform the method of the first aspect. In certain embodiments, the control unit is configured to control the gas flow through the gas inlets and/or the suction through the discharge channel to perform the powder removal step of the method of the first aspect. In certain embodiments, the control unit is configured to control the more than one valves to provide gas flow into the building chamber through nozzles to desired locations in the building chamber at a desired pressure and velocity. In certain example embodiments, the control unit comprises at least one processor and program code executable by the at least one processor.

According to a third aspect of the invention there is provided a building chamber for the method of the first aspect of the invention. The present inventors have developed a method and apparatus for removing free powder from a building chamber for additive manufacturing, and for recycling free powder in additive manufacturing. The current invention allows removing free powder from the building chamber and recycling the free powder without manually performed steps, i.e. automatic removal and recycling of free powder in additive manufacturing.

The removing or recycling of the free powder can be performed without detaching any parts of the apparatus. Further, the free powder can be removed from the outer surface of the object, including cavities having an opening in its outer surface, without having to remove the object from the building chamber. With the current invention free powder can be removed and recycled without exposing the operator of the apparatus or the surroundings to free powder. Without limiting the scope and interpretation of the patent claims, certain technical effects of one or more of the example embodiments disclosed herein are listed in the following. A technical effect is providing a gas flow from various directions to the building chamber, and controlling and altering said gas flow for efficient removal of free powder. Another technical effect is providing swirls in the building chamber for efficient removal of free powder by altering the pressure inside the building chamber. Another technical effect is separating from the removed free powder a waste portion that is not desirable for reuse in additive manufacturing. A further technical effect is that substantially all free powder may be removed from the surface of the formed object and/or the building chamber without vibrating the building chamber or any part thereof, such as the building platform.

Different non-binding example aspects and embodiments of the present invention have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in implementations of the present invention. Some embodiments may be presented only with reference to certain example aspects of the invention. It should be appreciated that corresponding embodiments may apply to other example aspects as well.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments of the invention will be described with reference to the accompanying drawings, in which: Fig. 1 shows a simplified picture of an apparatus according to an embodiment of the invention;

Fig. 2 shows a simplified picture of a building chamber according to an embodiment of the invention;

Fig. 3 shows a block diagram of a method according to an embodiment of the invention.

DETAILED DESCRIPTION In the following description, like reference signs denote like elements or steps.

Fig. 1 shows a simplified picture of an apparatus 100 according to an embodiment of the invention. The apparatus comprises a building chamber 200 for additive manufacturing, a discharge channel 120 in flow connection with the building chamber 200, a recycling assembly in flow connection with the discharge channel 120, and means for causing a powder flow from the recycling assembly to the building chamber 200. In the embodiment of Fig. 1 , the discharge channel comprises a valve 130 configured to open and close the flow connection between the discharge channel 120 and the building chamber 200.

In the embodiment shown in Fig. 1 the flow connection between the discharge channel 120 and the recycling assembly comprises a first receptacle 1 10. The first receptacle 1 10 of the embodiment of Fig. 1 is attached to the discharge channel via an inlet of the first receptacle 1 10. The first receptacle 1 10 of the embodiment of Fig. 1 comprises two outlets; one outlet being connected to a vacuum source 190 via a conduit or suction line, and the other outlet being attached to the recycling assembly. The vacuum source 190 is configured to create a suction from the building chamber 200 through the discharge channel 120 and through the first receptacle 1 10. The first receptacle 1 10 is configured to receive the removed free powder from the building chamber 200 through the discharge channel 120.

In certain other embodiments, the flow connection between the discharge channel 120 and the recycling assembly is formed without a receptacle. The flow connection between the discharge channel 120 and the recycling assembly can for example comprise a conduit, or the discharge channel 120 can be directly attached to the recycling assembly.

The recycling assembly of the embodiment shown in Fig. 1 comprises a conduit attached to an outlet of the first receptacle 1 10, the other end of said conduit being attached to a first powder pump 140. The first powder pump 140 of the recycling assembly of the embodiment of Fig. 1 is configured to convey removed free powder from the first receptacle 1 10, through the conduit attaching the recycling assembly to the first receptacle 1 10, to a defining assembly 150. The removed free powder may be streamlined from the first vacuum pump 140 into the defining assembly 150. The defining assembly 150 is configured to define from the removed free powder a recyclable portion.

In certain embodiments, the defining assembly 150 comprises a flow through separator. Depending on the implementation, the defining assembly 150 can comprise more than one flow through separator. The more than one flow through separator may have different separation criteria. In certain embodiments, the more than one flow through separators are arranged on top of each other, optionally a distance from each other.

In certain embodiments, the flow through separator is a sieve or a screen. In certain embodiments, the flow through separator is configured to pass through particles smaller than 100 μιτι, preferably smaller than 50 μιτι, most preferably smaller than 40 μιτι.

The flow through separator can be configured to be detachable and, optionally, re- attachable. The flow through separator may be changed, for example during maintenance of the apparatus 100.

In certain embodiments, the defining assembly 150 is configured to separate the removed free powder into a recyclable portion and a waste portion. The waste portion may consist of particles that have been attached to each other. The attaching of powder particles to each other may have been caused by softening, melting, phase transition, bonding fluid, bonding material, or a combination thereof.

In certain embodiments, the defining unit 150 comprises an inlet for the removed free powder, a fist outlet for the recyclable portion, and a second outlet for the waste portion. The first outlet of the defining unit 150 may be attached to an inlet of a second receptacle 160. In the embodiment of Fig. 1 , the outlet configured to remove the waste portion from the defining assembly 150 is arranged in a sidewall of the defining assembly 150. In the embodiment of Fig. 1 , the defining assembly 150 is arranged above a second receptacle 160 configured to receive the recyclable portion. In the embodiment of Fig. 1 , the second receptacle forms a part of the recycling assembly. The recyclable portion may be guided to the second receptacle 160 by gravity, through at least one conduit, or a combination thereof. In certain embodiments, the free powder is pumped into the second receptacle 160.

In the embodiment of Fig. 1 , the second receptacle 160 comprises an outlet connected to a second powder 180 pump through a conduit. The second powder pump 180 is configured to convey the recyclable portion from the second receptacle 160 to the building chamber 200 through the conduit connecting the second receptacle 160 to the second powder pump 180. In the embodiment of Fig. 1 , said conduit and the second powder pump form a part of the recycling assembly. In the embodiment shown in Fig. 1 , the second powder pump 180 is arranged over the building chamber 200.

In certain other embodiments, the apparatus 100 is provided without a second receptacle 160. For example, an outlet of the defining assembly 150 can be attached to a conduit connected to the second powder pump 180.

The recycling assembly of the embodiment of Fig. 1 further comprises a third receptacle 170 configured to receive the waste portion from the defining assembly 150. The waste portion may be guided to the third receptacle 170 by a conduit, gravity, or a combination thereof. In certain embodiments, an inlet of the third receptacle 170 is connected to the defining assembly by a conduit attached to the defining assembly. Optionally, the waste portion is directly discarded.

In the embodiment shown in Fig. 1 , the apparatus 100 comprises one vacuum source 190. In addition to being connected to the first receptacle 1 10, the vacuum source is also connected to the first powder pump 140 and the second powder pump 180 with conduits or suction lines. The vacuum source 190 may be configured to enhance the suction of the first powder pump 140. Optionally, the vacuum source 190 can be configured to create a suction in the first powder pump 140. Further, the vacuum source may be configured to enhance the suction of the second powder pump 180, or configured to create a suction in the second powder pump 180. In certain embodiments, the conduit or conduits, or suction line or lines, connected to the vacuum source 190 comprises a respective valve configured to control the suction in said conduit or conduits, or suction line or lines.

The apparatus 100 is sealed so that, substantially, powder cannot escape from the apparatus 100 during operation of the apparatus 100. In certain embodiments, the apparatus 100 is sealed with rubber seals, or at least a part of the apparatus 100 is sealed with rubber seals.

In certain embodiments, the apparatus 100 comprises means for controlling the powder flow from the second powder pump 180 to the building chamber 200.

In certain embodiments, means for controlling the powder flow comprises a powder feeder. The powder feeder may be arranged in the building chamber 200, or outside the building chamber 200. In certain embodiments, the second powder pump 180 is directly connected to the powder feeder.

In certain embodiments, the defining assembly 150 comprises an ultrasonic vibrating unit. The ultrasonic unit vibrating unit may be configured vibrate the defining assembly 150, or at least a portion of the defining assembly 150. An ultrasonic unit can increase the separating capacity of the defining assembly 150, and facilitate the cleaning or maintenance of the defining assembly 150.

In certain embodiments, the defining assembly 150 comprises at least one motor configured to move the defining assembly 150, or at least a portion of it. The motor may be configured to vibrate the defining assembly 150, or at least a portion of it. The at least a portion of the defining assembly 150 may be the flow through separator. Preferably, the defining unit comprises two motors. In certain embodiments, the defining assembly 150 comprises bellows or springs configured to allow movement or vibration of the defining assembly, or at least a portion of it. In certain embodiments, the first powder pump 140, or the second powder pump 180, or both powder pumps 140, 180, comprises a butterfly valve configured to discharge powder from the pump. The butterfly valve may be controlled by gravity. In certain embodiments, the butterfly valve comprises a sleeve configured to facilitate tight packing of powder in the powder pump or pumps 140, 180. Further, the sleeve may be configured to enable clean flow of powder from the powder pump or pumps 140, 180, especially at gravitational discharge of powder from the pump or pumps 140, 180. In certain embodiments, the sleeve comprises polymer, preferably rubber.

In certain embodiments, the first powder pump or pumps 140, 180, comprise means for monitoring the powder in the pump or pumps 140, 180. The means for monitoring may comprise a sensor. The sensor may be configured to monitor the amount of powder. The amount of powder can for example be monitored by monitoring the height of powder inside the pump or pumps 140, 180. The sensor may further be configured to monitor how compactly packed the powder is inside the pump or pumps 140, 180. The holding capacity of the pump or pumps 140, 180 of apparatus 100 may be selected based on the desired scale of the apparatus 100. In certain embodiments, the holding capacity of the pump or pumps 140, 180 ranges from 1 dm³ to 100 dm³, preferably from 1 dm³ to 50 dm³, and more preferably from 5 to 10 dm³. In certain embodiments, each pump of apparatus 100 is individually controlled. Optionally, the pumps can be controlled in groups of pumps or collectively. In certain embodiments, the pump or pumps 140, 180 of apparatus 100 are vacuum based. Dropping powder from the pump or pumps 140, 180 may require breaking a vacuum in the pump or pumps 140, 180. In certain embodiments, the interior of the pump or pumps 140, 180 is at least partially coated. The coating may be formed for example by electroplating. In certain embodiments, the apparatus 100 comprises at least one air breather configured to protect sensitive parts of the apparatus 100 from contamination. The contamination may be powder contamination. In certain embodiments, the air breather may be configured to protect the vacuum source 190. The air breather may protect the vacuum source 190 from contaminations from at least one powder receptacle, and function as a filter between powder and the vacuum source 190. In certain embodiments, an air valve is attached on the side of the at least one air breather. In certain embodiments, an air filter is configured to prevent free powder to flow into the vacuum source 190. The suction created by the vacuum source 190 may be created through the air filter.

In certain embodiments, the apparatus 100 comprises more than one vacuum source. The apparatus 100 may comprise two, three, or more vacuum sources. In certain embodiments, the first powder pump 140, the first receptacle 1 10 and the second powder pump 180 are each connected to a respective vacuum source. The vacuum source 190 may be mounted on a plate to facilitate maintenance of the vacuum source 190.

In certain embodiment, the apparatus 100 comprises at least one loader single receiver (LSR) controller. The at least one LSR controller may be comprised by a powder pump or pumps 140, 180. In certain embodiments, the at least one LSR controller is configured to integrate the vacuum source 190 and the first powder pump 140, the second powder pump 180, or both powder pumps 140, 180. A LSR controller is a safe and robust controller. A LSR controller is able to handle multiple applications and configurations. In certain embodiments, the at least one LSR controller comprises a screen configured to indicate information to an operator. Such information may be power, warning alarms, failure alarms, status of the LSR controller, such as load status or emptying status. In certain embodiments, the LSR controller is configured to transfer a signal when powder starts to fill the powder pump or pumps 140, 180 and an outlet valve of the pump is not open. In certain embodiments, the LSR controller comprises a switch configured to switch between different modes of operation. Such modes of operation may be single central receiver, gravity discharge, and fill to level. The switch may be for example an internal switch, or a rotational switch.

In certain embodiment, the receptacle or receptacles 1 10, 160, 170 of apparatus 100 have an at least partially coated surface, preferably an at least partially coated inner surface. The coating of the inner surface may comprise paint, lacquer, polymer, metal, oxide, or any combination thereof. The coating of the inner surface is configured to prevent powder from sticking on the inner surface of the receptacle. In certain embodiments, the receptacle or receptacles 1 10, 160, 170 of apparatus 100 are cylindrical or rectangular. The apparatus 100 may comprise receptacles of different shape, size, or both. The volume of the receptacles may be selected based on the desired scale of the apparatus 100. In certain embodiments, the volume of the receptacle or receptacles 1 10, 160, 170 ranges from 1 to 1000 I, preferably from 200 to 500 I, more preferably from 150 to 400 I, most preferably from 300 to 350 I. In certain embodiments, the third receptacle 170 has a smaller volume than the first receptacle 1 10, or than the second receptacle 160.

In certain embodiments, the receptacle or receptacles 1 10, 160, 170 comprise a welded top cap, a welded bottom cap, or both. In certain embodiments the welded top cap comprises a inlet port, and optionally an outlet port. The inlet port and the outlet port may be connected or attached, for example, to a vacuum source, a pump, a conduit, or to the building chamber 200.

Fig. 2 shows a simplified picture of a building chamber 200 according to an embodiment of the invention. The building chamber of Fig. 2 comprises gas inlets

220 configured to provide a gas flow to the building chamber 200. Fig. 2 further shows a discharge channel 170 in flow connection with the building chamber 200.

In the embodiment of Fig. 2, the discharge channel 170 is attached the building platform 240 being configured to be movable in the vertical direction. Further, Fig. 2 shows an object 210 being formed by additive manufacturing, the object standing on the building platform 240. In Fig. 2, the dots inside the building chamber 200 denote free powder. In certain embodiments, the air inlets comprise means for preventing reversed flow, i.e. gas flow from the building chamber 200 through the gas inlets 220. The means for preventing reversed flow may comprise check valves, or non-return valves. In certain embodiment, the apparatus 100 comprises at least one valve configured to control the gas flow to the building chamber 200 through the air inlets 220. In certain embodiments, the more than one valve is configured to separately control more than one group of gas inlets 220. Each group of gas inlets may be controlled by a respective valve. The more than one group of gas inlets may be formed by one gas inlet, or a plurality of gas inlets. The number of nozzles forming each of the more than one groups of gas inlets may be the same in each group, or may vary between groups. In certain embodiments, the more than one group of gas inlets is formed by 2-20 nozzles, preferably by 2-15 nozzles, more preferably by 2-10 nozzles, and even more preferably by 2-5 nozzles. In certain embodiments, the more than one group of gas inlets is formed by 4 nozzles. In certain embodiments, each of the more than one group of gas inlets is formed by 4 nozzles. In certain embodiments, the gas inlets 220 comprise, or form, at least two groups of gas inlets 220. Preferably, the gas inlets 220 comprise 1 to 500 groups of gas inlets 220, more preferable 2 to 50 groups of gas inlets 220, even more preferably 6 to 20 groups of gas inlets, further preferably 12 groups of gas inlets, and most preferably 4 groups of gas inlets. In certain embodiments, a respective valve is configured to control the gas flow through each gas inlet 220 individually. In an example embodiment, the apparatus 100 comprises 48 gas inlets optionally forming 12 groups of gas inlets. In certain embodiments, the valves comprise at least one valve unit configured to simultaneously control more than one gas inlets 220. The valve unit comprises a manifold.

In certain embodiments, the gas inlets 220 are arranged on at least one wall of the building chamber 200. The gas inlets 220 may be arranged on one, two, three, four, five, or six walls of the building chamber 200. In certain embodiments, the walls of the building chamber 200 comprises the building platform 240 and the top of the building chamber 200. In certain embodiments, the number of the gas inlets 220 ranges from 1 to 500, preferably from 10 to 200, more preferably from 20 to 100, most preferably from 40 to 50. in certain embodiments, the gas inlets are in connection with at least one gas source. The gas source may be for example a pressurized air source, or a nitrogen source. The apparatus 100 may comprise means for controlling the pressure of the gas from the gas source. Such means may be for example a valve.

In certain embodiments, the gas inlets 220 are nozzles.

In the embodiment shown in Fig. 2, powder is provided to the building chamber 200 through the top of the building chamber 200. In certain embodiments, the top of the building chamber comprises an inlet or an opening. The inlet or opening in the top of the building chamber can be openable and closable. In certain embodiments, the building chamber 200 comprises a lid configured to open and close the top of the building chamber. In certain embodiments, the lid is a sealing plate. In certain embodiments, the apparatus 100 comprises pneumatic cylinders configured to move the sealing plate. In certain embodiments, the sealing plate is arranged to be movable on rails, roller blocks, or a combination thereof.

In certain embodiments, the building chamber 200 comprises a door for removing the formed object 210. In certain embodiments, the door is arranged in a sidewall of the building chamber 200. In certain embodiments, the door is configured to be openable and closable by moving the door in the vertical direction, i.e. by. lifting and lowering the door.

In certain embodiments, the building chamber 200 comprises a mid-reservoir configured to receive the recyclable portion from the recycling assembly. In certain embodiments, the mid-reservoir is further configured to receive unused powder. The mid-reservoir may comprise a feeding roller. The feeding roller may comprise at least one groove configured to scoop powder from the mid-reservoir to a powder spreading table. In certain embodiments, the feeding roller is arranged to be rotatable. The feeding of powder from the mid-reservoir to the powder spreading table with the feeding roller can be controlled by controlling the number of revolutions and the revolution speed of the feeding roller. In certain embodiments, the feeding roller comprises a drive. The drive may be for example a semi rotary drive. In certain embodiments, the feeding roller comprises an actuator.

In certain embodiments, the powder is metal. The powder in this context refers to unused powder, free powder, removed free powder, the recyclable and the waste portion. In certain embodiments, the powder comprises or is stainless steel. The stainless steel may be 316 stainless steel. In certain embodiments, the average particle size of the powder may be less than 100 μιτι, preferably from 10 to 50 μιτι and more preferably from 20 to 40 μιτι. In certain other embodiments, the powder may be a mixture of fine particles and coarse particles.

In certain embodiments, the apparatus 100 comprises a scanner head configured to perform the additive manufacturing. The scanner head can be controlled vertically and horizontally. In certain embodiments, the scanner head is arranged above the object 210 in the building chamber 200.

Fig. 3 shows a block diagram of a method according to an embodiment of the invention. In step 310, an object 210 is formed by additive manufacturing in a building chamber 200. In a second step 320, free powder is removed from the building chamber 200 through a discharge channel 120. In a third step 330, the removed free powder is conveyed to a recycling assembly being in flow connection with the discharge channel 120. In a fourth step 340, the removed free powder is recycled, said recycling comprising causing a powder flow from the recycling assembly to or towards the building chamber 200.

In certain embodiments, recycling the removed free powder comprises defining from the removed free powder a recyclable portion. The defining from the removed free powder a recyclable portion may be based on particle size. In certain embodiments, defining from the removed free powder a recyclable portion comprises passing the removed free powder through a through flow separator. In certain embodiments, defining from the removed free powder a recyclable portion comprises sieving the removed free powder. The defining from the removed free powder a recyclable portion may comprise vibrating the defining unit 150, or a portion of it. In certain embodiments, defining from the free powder a recyclable portion comprises separating from the free powder a waste portion.

In certain embodiments, defining from the free powder a recyclable portion comprises feeding free powder through an inlet, separating the recyclable portion from the waste portion, and conveying the recyclable portion through a first outlet, and conveying the waste portion through a second outlet. The separating may comprise passing the free powder to a flow through separator, or sieving the removed free powder.

In certain embodiments, the method comprises collecting the waste portion. In certain other embodiments, the method comprises directly discarding the waste portion.

In certain embodiments, recycling 340 the removed free powder comprises conveying the removed free powder from the first receptacle 1 10 to the defining assembly 150. In certain embodiments, recycling 340 the removed free powder comprises conveying the removed free powder to the building chamber 200 with a second powder pump 180. In certain embodiments, recycling 340 the removed free powder comprises feeding the removed free powder into the building chamber 200. In certain embodiments, recycling the removed free 340 powder comprises mixing the removed free powder with unused powder and feeding the mixture of removed free powder and unused powder into the building chamber 200.

In certain embodiments, removing 320 free powder from the building chamber 200 comprises providing a gas flow into the building chamber 200 through gas inlets 220. In certain embodiments, removing 320 free powder from the building chamber 200 comprises controlling the gas flow through the gas inlets 220 by more than one valve. Controlling the gas flow through the gas inlets 220 by more than one valve may comprise separately controlling more than one group of gas inlets 220. Controlling the gas flow through the gas inlets 220 by more than one valve may comprise opening and closing the more than one valve. In certain embodiments, controlling the gas flow through the gas inlets 220 by more than one valve comprises independently controlling each of the more than one valves. In certain embodiments, removing 320 free powder from the building chamber 200 comprises controlling the flow rate through the gas inlets 220. Controlling the flow rate through the gas inlets 220 may comprise controlling the gas source. Controlling the gas flow or the flow rate through the gas inlets 220 may comprise controlling the pressure of the gas from the gas source.

In certain embodiments, removing 320 free powder from the building chamber 200 comprises altering the gas flow in the building chamber 200 by controlling the gas flow through the gas inlets 220. In certain embodiments, removing 320 free powder from the building chamber 200 comprises providing a suction from the building chamber 200 through the discharge channel 120. In certain embodiments, removing 320 free powder 320 from the building chamber 200 comprises providing the suction through a receptacle 1 10 being in flow connection with the discharge channel 120.

In certain embodiments, removing 320 free powder from the building chamber 220 comprises changing the pressure inside the building chamber 200. In certain embodiments, changing the pressure inside the building chamber 200 comprises opening and closing the flow connection between the discharge channel and the building chamber when a suction is provided from the building chamber 200 through the discharge channel 120. The opening and closing steps may be repeated. In certain embodiments, changing the pressure inside the building chamber 200 comprises pulsatively repeating the opening and closing steps, i.e. repeatedly opening and closing for short durations of time the connection between the discharge channel and the building chamber. In certain embodiments, the repeated, rapid opening and closing of the flow connection between the building chamber 200 and the discharge channel 120, when a suction is provided from the building chamber 200 through the discharge channel 120, creates swirls efficiently removing powder from the surface of the formed object 210.

In an example embodiment, the pressure in the first receptacle 1 10 in flow connection with the discharge channel 120 is 0.5 bar, and when the flow connection between the discharge channel 120 and the building chamber 200 is closed, the pressure inside the building chamber 200 is 2 bars. In said example embodiment, a temporary pressure drop is created by opening the flow connection between the discharge channel 120 and the building chamber 200 for a few milliseconds, such as from 1 to 100 milliseconds, preferably from 5 to 20 milliseconds, then closing said flow connection. Directly after the temporary pressure drop in the building chamber 200 (i.e. when the flow connection has been opened and then closed) gas inside the building chamber 200 expands due to the increase in pressure (compared to the temporary pressure drop). Said expansion of gas removes, or dislodges, free powder from the surface of the formed object 210. Optionally, said steps may be repeated to further remove, or dislodge, free powder from the surface of the formed object 210.

The method may comprise keeping the top of the building chamber 200 closed while removing 320 free powder from the building chamber, and keeping the top of the building chamber open while forming an object 310 by additive manufacturing in the building chamber 200. The method may comprise lowering the building platform 240 while forming 310 an object by additive manufacturing in the building chamber 200. The lowering may be stepwise lowering, or continuous lowering. In certain embodiments, the method comprises lowering the building platform 240 before removing 320 free powder from the building chamber 200.

In certain embodiments, removing 320 free powder is performed without removing or transferring the formed object 210 from the building chamber 200. In certain embodiments, removing 320 free powder is based on altering the gas flow in the building chamber 200 together with altering the pressure in the building chamber 200. In certain embodiments, the method is automatic.

In certain embodiments, the additive manufacturing comprises selective laser melting. In certain embodiments, the additive manufacturing is powder bed fusion with selective laser melting.

In certain embodiments, removing 320 free powder from the outer surface of the object 210 and from the building chamber 200 is based on creating a gas flow in the building chamber 200 through gas inlets 220, and creating a pressure difference in the building chamber by opening and closing the flow connection between the building chamber 200 and the discharge channel 120 when a suction is provided from the building chamber 200 through the discharge channel 120. In certain embodiments, controlling the gas inlets 220 in groups of gas inlets 220, or individually, controls and alters the gas flow in the building chamber 200. In certain embodiments, removing 320 free powder from the building chamber and from the outer surface of the formed object comprises creating different kinds of airflow in the building chamber 200

Various embodiments have been presented. It should be appreciated that in this document, words comprise, include and contain are each used as open-ended expressions with no intended exclusivity.

The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments of the invention a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention.

Furthermore, some of the features of the afore-disclosed embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.

Claims

Claims:

1 . A method comprising:

forming an object by additive manufacturing in a building chamber;

recycling the removed free powder, said recycling comprising causing a powder flow from the recycling assembly to the building chamber.

2. The method of claim 1 , wherein recycling the removed free powder comprises defining from the removed free powder a recyclable portion.

3. The method of claim 1 or 2, wherein removing free powder from the building chamber comprises providing a gas flow into the building chamber through gas inlets.

4. The method of any preceding claim, wherein removing free powder from the building chamber comprises providing a suction from the building chamber through the discharge channel.

5. The method of any preceding claim, wherein removing free powder from the building chamber comprises controlling the gas flow through the gas inlets by more than one valve.

6. The method of claim 5, wherein controlling the gas flow through the gas inlets by more than one valve comprises separately controlling more than one group of gas inlets.

7. The method of any preceding claim, wherein removing free powder from the building chamber comprises changing the pressure inside the building chamber.

8. The method of claim 7, wherein changing the pressure inside the building chamber comprises opening and closing the flow connection between the discharge channel and the building chamber when a suction is provided from the building chamber through the discharge channel.

9. The method of claim 8, comprising repeating the opening and closing steps.

10. An apparatus comprising:

a building chamber for additive manufacturing;

a discharge channel in flow connection with the building chamber;

a recycling assembly in flow connection with the discharge channel;

and means for causing a powder flow from the recycling assembly to the building chamber for recycling the removed free powder.

1 1 .The apparatus of claim 10, wherein the recycling assembly comprises a defining assembly configured to define from the removed free powder a recyclable portion

12. The apparatus of any of claim 10 or 1 1 , wherein the building chamber

comprises gas inlets.

13. The apparatus of any of claims 10 to 12, comprising a vacuum source configured to provide a suction from the building chamber through the discharge channel.

14. The apparatus of any of claims 10 to 13, comprising more than one valve configured to control gas flow through the gas inlets.

15. The apparatus of claim 14, wherein the more than one valve is configured to separately control more than one group of gas inlets.

16. The apparatus of any of claims 10 to 15, comprising a valve configured to open and close the flow connection between the discharge channel and the building chamber.

17. A building chamber for the method of claims 1 to 15.