WO2026012941A1

WO2026012941A1 - Methods and arrangements for controlling fusion parameters in electron beam additive manufacturing

Info

Publication number: WO2026012941A1
Application number: PCT/EP2025/069191
Authority: WO
Inventors: Arun Ramanathan BALACHANDRAMURTHI; Ulf Ackelid
Original assignee: Freemelt AB
Current assignee: Freemelt AB
Priority date: 2024-07-12
Filing date: 2025-07-04
Publication date: 2026-01-15
Anticipated expiration: 2027-01-12
Also published as: SE2450809A1

Abstract

The present invention relates to additive manufacturing arrangements and methods for additive manufacturing by selective fusion of layers of a three-dimensional product from a powder bed (240) comprising successively formed powder layers. An electron source (210) is configured to deliver an electron beam (220) towards a top surface (260) of the powder bed (240). A top surface (260) of the powder bed (240) is exposed for the electron beam (220) to melt the metal powder to form a melt pool, wherein the electron beam (220) is moved to different heating positions at said powder bed (240). The electron beam (220) is controlled and manipulated in accordance with a beam adjustment sequence within a predetermined duration, wherein the beam adjustment sequence includes different sequence steps each associated with a set of beam parameters.

Description

METHODS AND ARRANGEMENTS FOR CONTROLLING FUSION PARAMETERS IN ELECTRON BEAM ADDITIVE MANUFACTURING

TECHNICAL FIELD

The present disclosure relates generally to arrangements and methods for additive manufacturing for successively forming a three-dimensional product from a powder bed comprising at least one powder layer by means of powder bed fusion.

BACKGROUND

Additive manufacturing using electron beam powder bed fusion for producing three- dimensional objects, for example using a metal powder, is gaining more and more interest. During the fusion process, the melting properties of the powder bed are very dependent of build geometry and therefore it has become increasingly important to accurately control the melting properties and the process.

When melting a powder layer point-by-point, spot-by-spot or pixel-by-pixel, the electron beam is programmed to move rapidly or jump rapidly between pixels, and to stay for a short time in each pixel until the powder layer has melted locally. The electron beam stays at each pixel during a dwell time, the time the beam spot resides in each pixel. The dwell time is typically in the range from microseconds to milliseconds in Electron Beam Powder Bed Fusion. The beam spot in Electron Beam Powder Bed Fusion typically has a near-circular shape in the XY-direction and a near-Gaussian intensity distribution. Parameters such as beam power and spot size are constant throughout the dwell time duration, and when the pixel is fully melted, the beam does not return to this pixel again within the same powder layer melting sequence. In most cases, the electron beam melts each pixel only once per powder layer.

However, there are some phenomena observed in electron beam powder bed fusion that may produce negative effects on the melting process and the resulting material properties of built components. For example, insufficient sintering during preheating, which may increase the risk of smoke events and spattering which is small glowing droplets or particles that are spattered from the melt pool due to electrostatic forces and/or vapor pressure in the melt pool. Furthermore, two other potential problems are excessive metal vaporization due to extremely high temperature in the center of the melt pool and too rapid cooling during solidification of the melt pool, freezing a crystal structure far from thermal equilibrium, and increasing the risk of residual stress and cracking.

Hence, there is still a need in the art for improved devices and methods for additive manufacturing for successively forming a three-dimensional product from a powder bed comprising at least one powder layer by means of powder bed fusion.

SUMMARY

The above described problems are addressed by the claimed additive manufacturing arrangement and method for successively forming layers of a three-dimensional product from a powder bed comprising at least one powder layer by means of powder bed fusion. In the improved arrangements and methods for additive manufacturing according to the present invention, some or all of the above-mentioned problems are solved or alleviated.

According to the present invention, the electron beam is shaped and deflected by a number of coils electron source in the electron gun column. By using fast coils, it is possible to manipulate the electron beam spot on a time scale shorter than the dwell time. It is also possible to let the electron beam visit the same pixel twice or several times within a short time span, performing different tasks at each visit, such as pixel preheating, pixel melting and pixel post-heating. The dwell time may also be different at each visit. For example, the dwell time may be shorter the second and/or third visit than the first, or it may successively be shorter at each visit. Alternatively, the dwell time may be longer the second and/or third visit, may successively be longer at each visit. Further, the dwell time be alternating between longer and shorter length between different visits. Thereby, the quality of the manufactured objects can be improved, and manufacturing of more complex 3-D objects is enabled.

A powder bed position is defined as coordinates in the powder bed surface plane, it is a point or pixel having (x,y)-coordinates in the powder bed plane. Further, during the fusion process a powder layer is melted pixel-by-pixel where the electron beam is moved between pixels and stays for a period at each pixel, for example, until the powder layer has melted locally, i.e. at the point where the electron beam spot is directed. The electron beam spot delivers energy to pixels on the powder bed surface according to a predetermined pattern and according to electron beam parameters, which according to the present invention can be adjusted and/or varied during a certain dwell time. The electron beam parameters may include:

Beam shape, Beam Power,

Spot Size (effective diameter of the beam spot),

Spot centre (centre coordinates for the pixel of the beam spot)

Dwell Time. i.e. the duration of energy deliverance of the beam spot at a pixel, may also be adjusted or varied but may be maintained during a fusion process. Further, the dwell time may be adjusted between different pixels, between different beam patterns or beam adjustment sequences. Dwell Time is typically in the range from microseconds to milliseconds.

According to one aspect of the present invention, there is provided an additive manufacturing arrangement comprising an additive manufacturing apparatus for additive manufacturing by selective fusion of layers of a three-dimensional product from a powder bed comprising successively formed powder layers, the apparatus comprising: a powder feeding device configured to form successive powder layers, an electron source configured to deliver an electron beam towards a top surface of the powder bed, wherein the electron beam is used in the selective fusion of each layer of the three-dimensional product, wherein the electron beam is moved to different heating positions at said powder bed, an electron beam controller is arranged to control and manipulate said electron beam in accordance with a beam adjustment sequence including at least two beam spot states within a predetermined duration, wherein said predetermined duration is the dwell time of the electron beam, the dwell time being the duration of energy deliverance of the beam spot at a pixel, wherein said at least two beam spot states comprising a focused state and a defocused state. In the focused state, the beam spot diameter has a first value and in the defocused state the beam spot diameter has a second value, wherein the first value is smaller than the second value. Preferably, this change of beam spot diameter is executed within the dwell time. This can reduce the risk of smoke, spatter and excessive evaporation from the melt pool.

The present invention is based on the insight that the electron source and electron beam can be manipulated within the dwell time, i.e. within a time cycle or time scale shorter than the dwell time. Alternatively, the electron beam may for example visit the same pixel twice or several times within a short time span, performing different tasks at each visit, such as pixel preheating, pixel melting and pixel post-heating, at, for example, different dwell times, or the same dwell time. Thereby, it is possible to reduce or even remove phenomena observed in electron beam powder bed fusion that may have negative effects such insufficient sintering during preheating, which may increase the risk of smoke events, spatter (fireworks) - small glowing droplets or particles that are spattered from the melt pool due to electrostatic forces and/or vapor pressure in the melt pool, and excessive metal vaporization due to extremely high temperature in the centre of the melt pool. In addition, it is possible to minimize risk for too rapid cooling during solidification of the melt pool, which entails freezing a crystal structure far from thermal equilibrium, and increasing the risk of residual stress and cracking

According to a further aspect of the present invention, there is provided an additive manufacturing arrangement comprising an additive manufacturing apparatus for additive manufacturing by selective fusion of layers of a three-dimensional product from a powder bed comprising successively formed powder layers. The apparatus comprises a powder feeding device configured to form successive powder layers. Further, an electron source is configured to deliver an electron beam towards the top surface of the powder bed, wherein the electron beam is used in the selective fusion of each layer of the three-dimensional product. The electron source is configured to move the electron beam to different heating positions at the powder bed. An electron beam controller is arranged to control and manipulate the electron beam in accordance with a beam adjustment sequence within a predetermined time period or duration, wherein said predetermined time period or duration is the dwell time of the electron beam, the dwell time being the duration of energy deliverance of the beam spot at a pixel, wherein the beam adjustment sequence includes different sequence steps each associated with a set of beam parameters.

In embodiments of the present invention, the electron beam controller is arranged to control and manipulate the electron beam in accordance with the beam adjustment sequence while maintaining the electron beam in a certain heating position at the powder bed.

In embodiment of the present invention, the electron beam controller is arranged to control and manipulate said electron beam in accordance with the beam adjustment sequence while maintaining the electron beam in a certain heating position at the powder bed, and wherein the set of beam parameters of each sequence step includes a beam shape and/or a beam spot centre, wherein beam shape and/or beam spot centre is adjusted in each sequence step in the beam adjustment sequence.

According to embodiments of the present invention, the electron beam controller is arranged to control and manipulate the electron beam to influence heating at a selected pixel of a heating position. In embodiments of the present invention, the electron source comprises at least one coil configured to manipulate the electron beam by shaping and deflecting the electron beam upon control instructions from the electron beam controller according to the beam adjustment sequence.

According to embodiments of the present invention, the electron beam controller is arranged to control the electron source to manipulate the electron beam by adapting at least one electron beam parameter and/or a heating position pattern according to the beam adjustment sequence.

According to an aspect of the present invention, there is provided a method for additive manufacturing by selective fusion of layers of a three-dimensional product from a powder bed comprising successively formed powder layers, comprising the steps of: exposing a top surface of the powder bed for the electron beam to melt the metal powder to form a melt pool, wherein the electron beam is moved to different heating positions at the powder bed; controlling and manipulating the electron beam in accordance with a beam adjustment sequence within a predetermined time period, the beam adjustment sequence including different sequence steps each associated with a set of beam parameters.

According to embodiments of the present invention, controlling and manipulating the electron beam in accordance with the beam adjustment sequence while maintaining the electron beam in a certain heating position at the powder bed.

According to embodiments of the present invention, controlling and manipulating the electron beam in accordance with the beam adjustment sequence while maintaining the electron beam in a certain heating position at the powder bed, and wherein said set of beam parameters of each sequence step includes a beam shape and/or a beam spot centre, wherein beam shape and/or beam spot centre is adjusted in each sequence step in the beam adjustment sequence.

According to embodiments of the present invention, controlling and manipulating the electron beam to influence heating at a selected pixel of a heating position. According to embodiments of the present invention, the electron beam is manipulated by shaping and deflecting the electron beam based on control instructions from the electron beam controller according to the beam adjustment sequence.

According to embodiments of the present invention, the electron source is controlled to manipulate the electron beam by adapting at least one electron beam parameter and/or a heating position pattern according to said beam adjustment sequence.

The scope of the invention is defined by the claims which are incorporated into this section by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically illustrates an additive manufacturing arrangement for successively forming a three-dimensional product from a powder bed comprising at least one powder layer by means of powder bed fusion, in accordance with one or more embodiments described herein.

Figs. 2a - 2d schematically illustrate beam adjustment sequences in accordance with the present invention.

Fig. 3 illustrates steps of embodiments of a method in accordance with the present invention.

Figs. 4a - 4b schematically illustrate heating patterns in accordance with the present invention.

Fig. 5 illustrates steps of embodiments of a method in accordance with the present invention.

Fig. 6 illustrates steps of embodiments of a method in accordance with the present invention.

Fig. 7a - 7c illustrate further beam adjustment sequences in accordance with the present invention. Embodiments of the present disclosure and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

Additive manufacturing and 3D-printing refer to the process of manufacturing objects from 3D model data by joining powder materials layer upon layer. Powder bed fusion means additive manufacturing or 3D-printing where objects are built up in a powder bed. Thin layers of powder are repeatedly spread by a powder distributing member over a powder bed and fused by a beam from an energy source to a predetermined geometry for each layer. The powder bed is preferably lowered one nominal layer thickness (e.g. 0,020-0,100 mm) before distribution of the next powder layer. The energy source can be, for example, a laser or an electron gun. Upon finishing a powder bed fusion process, the fused object will be embedded in powder. The powder is removed after completion of the build.

The present disclosure relates generally to arrangements and methods for additive manufacturing for successively forming a three-dimensional product from a powder bed comprising at least one powder layer by means of powder bed fusion. Embodiments of the disclosed solution are presented in more detail in connection with the figures.

Figure 1 schematically illustrates an additive manufacturing arrangement 100 for successively forming layers of a three-dimensional product in which the present invention can be implemented. The arrangement 100 comprises an additive manufacturing apparatus 200, for additive manufacturing by selective fusion of a three-dimensional product from a powder bed comprising at least one powder layer 240 by means of powder bed fusion, in accordance with one or more embodiments described herein. Electron beam powder bed fusion normally takes place in vacuum, and the electron beam may operate in several process steps: it may preheat the powder layers to a semi-sintered state, fuse the powder by melting the powder in the powder layers, and add additional heat to the powder bed to maintain a predetermined temperature of the powder bed throughout the build. These process steps are preferably carried out under computer control to achieve predetermined quality requirements of the manufactured objects. In an electron beam powder bed fusion process, such as an additive manufacturing process for metal parts, the powder bed is normally also preheated for semi-sintering of the powder to reduce the risk for later levitation of charged powder and to increase the electrical conduction in the powder bed for increased transportation of electrons from the powder bed. The schematically illustrated additive manufacturing apparatus 200 comprises an electron beam source 210 and a powder bed 240, arranged in a build chamber 280. The build chamber can be a vacuum chamber, typical of E-PBF. The powder bed 240 may e.g. be formed by metal powder being distributed from a powder container 230 using a recoater mechanism 290. The powder bed 240 may comprise powder of any kind, such as e.g. powder composed of pure metal, metal alloys, intermetallics, metal matrix composite, ceramic powder, a mix of metal powder and ceramic powder, glass, graphite, diamond, composites, polymers, nanomaterials, and/or ionic compounds or any powder mixture thereof. The powder can also be a mixture of metal-based powder and insulating or semiconducting powder. The metal powder in the powder bed 240 is exposed to an electron beam 220 from the beam source 210. During the exposure to the electron beam 220, the metal powder is melted to form a melt pool.

In embodiments, the build chamber 280 and the powder container 230 are separated with a partitioning wall 235. The partitioning wall 235 is provided with a shutter mechanism 238 arranged to swiftly open and close, for example, when the recoater mechanism 290 moves back and forth to deliver metal powder into the built chamber 280. Thereby, an efficient delivery mechanism of metal powder is enabled at the same time as good vacuum conditions in the build chamber 280 can be preserved and maintained.

The electron emitter, when radiated with the laser beam, emits an electron beam into a charged particle channel of an anode. When the electron beam source is used for electron beam powder bed fusion, the electron beam 220 is directed onto a powder bed 240. The electron beam source 210 schematically shown in figure 2 is thus adapted to direct an electron beam 220 generated by a back heated charged particle emitter of a cathode onto the powder bed 240 via an anode and thereby fuse a three-dimensional product by fusing layer by layer of the powder in the powder bed 240 using the electron beam 220. In embodiments, the laser is a CO2 laser. In operation, a high voltage in the range of, for example 60 kV is applied over the cathode and the anode in a per se known manner.

The top layer 260 and the powder bed 240 are preferably formed by powder being distributed from a powder tank 230 using a recoater mechanism 290. The recoater mechanism may e.g. be in the form of a powder layer distributing member or recoater 290, which may e.g. be a linear actuator for distributing powder at the powder bed 240. The additive manufacturing arrangement 200 may also comprise a spillover bin 275, where spillover powder may be collected. A powder bed position is defined as coordinates in the powder bed surface plane, it is a point or pixel having (x,y)-coordinates in the powder bed plane. Further, during the fusion process a powder layer is melted pixel-by-pixel where the electron beam is moved between pixels and stays for a period, the dwell time, in each pixel, for example, until the powder layer has melted locally, i.e. at the point where the electron beam spot is directed. The electron beam spot delivers energy to pixels on the powder bed surface according to a predetermined pattern and according to electron beam parameters, which according to the present invention can be adjusted and/or varied during a certain dwell time. The electron beam parameters include:

Beam shape, Beam Power, Spot Size (effective diameter of the beam spot), Spot centre (centre coordinates for the pixel of the beam spot)

A dwell time, i.e. the duration of energy deliverance of the beam spot at a pixel, may also be adjusted or varied but may be maintained during a fusion process. Dwell Time is typically in the range from microseconds to milliseconds.

According to the present invention, an electron beam controller 250 is arranged to control and manipulate the electron beam 220 in accordance with a predetermined pattern within a predetermined period. In embodiments of the present invention, at least one coil 255 is configured to manipulate the electron beam 220 by shaping and deflecting the electron beam 220 upon receiving control instructions from the electron beam controller 250. The control instructions from the electron beam controller 250 may be based on user input via, for example, a graphical user interface and user input devices (not shown), and/or via information from different sensor or detecting devices arranged in or at the additive manufacturing apparatus 200 such as temperature sensors, radiation sensors, light sensors etc.

With reference now to Figs. 2a - 2d, different manipulation patterns are discussed.

In Fig. 2a, the beam shape is constant during the dwell time but the beam spot 261 is moved in circular pattern around a centre pixel during a predetermined duration, for example, the dwell time. Hence, a round spot shape that rotates around an off-centre point within the dwell time at a certain heating position. This could e.g. help to reduce overheating in the pixel centre 265. The at least one coil 255 is controlled to deflect the electron beam 220 forming six different circular beam spots during the dwell time in a circulating pattern, which may be clockwise or counterclockwise. The electron beam 220 may be moved continuously in this circular pattern, one or more lapse, during the dwell time. In this case, the beam adjustment sequence comprises six sequence steps, each including a beam deflection in order to move or rotate the beam spot around an off-centre point while maintaining the beam shape.

Fig. 2b shows a pattern where the beam shape is adjusted or manipulated during the dwell time but with the same pixel centre. The beam spot 266 has an elliptical shape that changes eccentricity within the dwell time duration. In this case, the at least one coil 255 is controlled to shape the electron beam 220 forming beam spots with changing eccentricity in each sequence step or continuously. The beam adjustment sequence includes five sequence steps, where the beam spot goes from being circular to different elliptical shapes having the same spot centre. As understood, the sequence order may go from larger elliptical to smaller elliptical to circular or vice versa, or from elliptical in one direction to elliptical in another direction in an alternating manner.

Fig. 2c illustrates a pattern where the beam spot 267 is rotated during dwell time, in this case an elliptical spot shape that rotates within the dwell time duration at a certain heating position. The at least one coil 255 is controlled to deflect the electron beam 220 forming three different circular beam spots during the dwell time in a circulating pattern, which may be clockwise or counterclockwise. In this case, the beam adjustment sequence comprises three sequence steps (or a multiple of three depending on, for example, the duration of dwell time and ability of the coils to adjust the electron beam), each including a beam deflection in order to move or rotate the beam spot around an off-centre point while maintaining the beam shape. It should be stressed that this pattern also can be executed in a continuous way.

Fig. 2d shows again a pattern where beam shape is constant during the dwell time and the beam spot 268 is moved in circular pattern around a centre pixel 269, a round spot shape that rotates around an off-centre point within the dwell time duration. The direction of rotation may be clockwise or counterclockwise and changes of size can proceed in any direction, i.e. from larger to smaller or vice versa. The at least one coil 255 is controlled to deflect the electron beam 220 forming four different circular beam spots during the dwell time in a circulating pattern, which may be clockwise or counterclockwise. In this case, the beam adjustment sequence comprises four sequence steps, each including a beam deflection in order to move or rotate the beam spot around an off-centre point while maintaining the beam shape. As understood by a skilled person, the beam shape can also be changed continuously. As understood, a beam adjustment sequence may comprise any number of sequence steps, and any combination of beam parameters. For example, changing between a focused state of the beam spot and a defocused state of the beam spot within the dwell time (the diameter of the beam spot is varied between a first value in the focused state and a second value in the defocused state, where the first value is smaller than the second value), movement of the spot centre in different directions, clock-wise or counter clock-wise, an adjustment of size and/or shape may be executed in different orders, from smaller to bigger, from circular to elliptical or vice versa.

Turning now to Fig. 3, embodiments of a method for additive manufacturing in accordance with the present invention will be discussed. The method is preferably used in an additive manufacturing apparatus 200 for additive manufacturing by selective fusion of a three- dimensional from a powder bed containing a metal powder which is exposed to an electron beam such as an electron beam as described above with reference to Fig. 1. The additive manufacturing apparatus 200 comprises an electron beam source 210 and a powder bed 240, arranged in a build chamber 280. The build chamber can be a vacuum chamber, typical of E-PBF. The powder bed 240 may e.g. be formed by metal powder being distributed from a powder container 230 using a recoater mechanism 290. The powder bed 240 may comprise powder of any kind, such as e.g. powder composed of pure metal, metal alloys, intermetallics, metal matrix composite, ceramic powder, a mix of metal powder and ceramic powder, glass, graphite, diamond, composites, polymers, nanomaterials, and/or ionic compounds or any powder mixture thereof. The powder can also be a mixture of metalbased powder and insulating or semiconducting powder. The powder in the powder bed 240 is exposed to an electron beam 220 from the beam source 210. During the exposure to the electron beam 220, the powder is melted to form a melt pool.

The method 300 may comprise:

Step 310: Initiating an additive manufacturing process to manufacture an object.

Step 320: forming a top surface 260 of the powder bed 240 by distributing the metal powder from the powder container 230 using a recoater mechanism 290.

Step 330: Exposing the top surface 260 of the powder bed 240 for the electron beam 220 to melt the metal powder to form a melt pool at a first heating position according to a heating position pattern.

Step 340: At the first heating position, controlling and manipulating the electron beam 220 in accordance with a beam adjustment sequence using an electron beam controller 250, for example, any of the beam adjustment sequences described above with reference to Figs. 2a - 2d, within a predetermined duration or period, preferably the dwell time. In embodiments, this is executed using at least one beam shaping coil and/or beam deflection coil.

Step 350: Repeating step 330 and 340 for subsequent heating positions according to the heating position pattern.

However, it should be noted that the beam adjustment sequence not necessary is the same for each heating position. It may be alternating sequences between a first sequence and a second sequence for every other heating position. For example, a first beam adjustment sequence may be used for every heating position.

Turning now to Fig. 4a-4b, Fig. 5 and 6, embodiments of a further method for additive manufacturing in accordance with the present invention will be discussed. The method is preferable used in an additive manufacturing apparatus 200 for additive manufacturing by selective fusion of a three-dimensional from a powder bed containing a metal powder which is exposed to an electron beam such as a laser beam or an electron beam as described above with reference to Fig. 1. According to this embodiment of the present invention, a recently melted and solidified pixel or heating position is reheated after a short time, typically after a few dwell times while the pixel is still hotter than its surroundings. The purpose of the reheating can be to slow down the pixel cooling rate to reduce the risk of internal stress and cracking. This illustrated in Fig. 4a, where a pixel P1 on the top surface 260 is first heated during the predetermined dwell time, and then pixel P2 and P3 according to the heating pattern during the predetermined dwell time. In this case, the electron beam is directed back to pixel P1 after two dwell times (i.e. heating at P2 and P3), Thus, the electron beam revisits pixel P1 and reheats it. This pattern is repeated during the fusion process. Of course, fewer or more dwell times may elapse before revisiting an already heated pixel. At the revisit, the beam parameters may be adjusted to a revisit beam parameter set, which may include for example heating during a shorter or longer dwell than the initial dwell time and/or at a lower or higher beam power and/or using a different beam shape.

The method 500 according to embodiments of the present invention may comprise: Step 510: Initiating an additive manufacturing process to manufacture an object. Step 520: forming a top surface 260 of the powder bed 240 by distributing the metal powder from the powder container 230 using a recoater mechanism 290.

Step 530: Exposing the top surface 260 of the powder bed 240 for the electron beam 220 to melt the metal powder to form a melt pool at subsequent heating positions according to a heating position pattern. This exposing step may apply a beam adjustment sequence as described above in connection with for example Fig. 2a - 2d and/or Fig. 3. Step 540: Revisiting a previous heating position and exposing the top surface 260 of the powder bed 240 for the electron beam 220 according to the heating position pattern using a revisit beam parameter set.

Step 550: Repeating step 530 and 540 for subsequent heating positions according to the heating position pattern.

According to another embodiment of the present invention, a pixel is preheated shortly before it is melted, typically a few dwell times before so that the pixel is still hotter than its surroundings when melting takes place. This can help to reduce spatter from the melt pool and also reduce the risk of smoke. With reference to Fig. 4b, this illustrated. The electron beam is directed first to position P1 , and the electron beam is manipulated to use preheat beam parameter, which may include a shorter heating time than the dwell time and/or a lower beam power. Then, positions P2, P3 and P4 are successively preheated before the electron beam is directed again to position P1 and the melting process starts. Thereafter, the electron beam preheats P5, P6 and P7, and returns to P2 for melting process. In an alternative embodiment of the method, the electron beam may preheat P1 , wait for a few dwell times, and then start melting process at P1. In yet another embodiment of the method, the electron beam is directed first to position P1 , and the electron beam is manipulated to use preheat beam parameters, which may include a shorter heating time than the dwell time and/or a lower beam power. Then, positions P2 and P3 are successively preheated before the electron beam is directed again to position P1 and the melting process starts. Thereafter, the electron beam preheats P4 and P5, and returns to P2 for melting process.

The method 600 according to embodiments of the present invention may comprise: Step 610: Initiating an additive manufacturing process to manufacture an object. Step 620: forming a top surface 260 of the powder bed 240 by distributing the metal powder from the powder container 230 using a recoater mechanism 290.

Step 630: Exposing the top surface 260 of the powder bed 240 for the electron beam 220 to preheat the metal powder to form a melt pool at heating positions according to a heating position pattern.

Step 640: Exposing the top surface 260 of the powder bed 240 for the electron beam 220 to melt the metal powder to form a melt pool at preheated heating positions according to a heating position pattern.

With reference now to Figs. 7a - 7c, further manipulation patterns will be discussed. In Fig. 7a, the beam shape is varied or changed during the dwell time, i.e. during the duration of energy deliverance of the beam spot at one pixel, from a first defocused state DS to a second focused state FS. In other words, the beam shape is adjusted between two different states at each pixel according to a beam adjustment sequence. In Fig. 7b, the beam shape is changed or varied from the focused state FS to the defocused state DS during the dwell time, i.e. during the duration of energy deliverance of the beam spot at one pixel. In other words, the beam shape is adjusted between two different states at each pixel according to a beam adjustment sequence. In Fig. 7c, the beam shape is changed or varied from the defocused state DS to the focused state FS during the dwell time, i.e. during the duration of energy deliverance of the beam spot at one pixel. In other words, the beam shape is adjusted between two different states at each pixel according to a beam adjustment sequence.

The foregoing disclosure is not intended to limit the present invention to the precise forms or particular fields of use disclosed. It is contemplated that various alternate embodiments and/or modifications to the present invention, whether explicitly described or implied herein, are possible in light of the disclosure. Accordingly, the scope of the invention is defined only by the claims.

Claims

1. Additive manufacturing arrangement (100) comprising an additive manufacturing apparatus (200) for additive manufacturing by selective fusion of layers of a three- dimensional product from a powder bed (240) comprising successively formed powder layers, the apparatus (200) comprising: a powder feeding device (290) configured to form consecutive powder layers; an electron source (210) configured to deliver an electron beam (220) towards a top surface (260) of the powder bed (240), wherein the electron beam (220) is used in the selective fusion of each layer of the three-dimensional product, wherein the electron beam (220) is moved to different heating positions at said powder bed (240), and an electron beam controller (250) arranged to control and manipulate said electron beam (220) in accordance with a beam adjustment sequence within a predetermined duration wherein said predetermined duration is the dwell time of the electron beam (210), the dwell time being the duration of energy deliverance of the beam spot at a pixel, said beam adjustment sequence including different sequence steps each associated with a set of beam parameters.

2. Additive manufacturing arrangement (100) according to claim 1, wherein said electron beam controller (250) is arranged to control and manipulate said electron beam (220) in accordance with a beam adjustment sequence including at least two states within a predetermined duration, wherein said at least two states comprising a focused state and a defocused state.

3. Additive manufacturing arrangement (100) according to claim 1, wherein said electron beam controller (250) is arranged to control and manipulate said electron beam (220) in accordance with said beam adjustment sequence while maintaining the electron beam (220) in a certain heating position at said powder bed (240).

4. Additive manufacturing arrangement (100) according to claim 1 , wherein said electron beam controller (250) is arranged to control and manipulate said electron beam (220) in accordance with said beam adjustment sequence while maintaining the electron beam (220) in a certain heating position at said powder bed (240), and wherein said set of beam parameters of each sequence step includes a beam shape and/or a beam spot centre, wherein beam shape and/or beam spot centre is adjusted in each sequence step in said beam adjustment sequence.

5. Additive manufacturing arrangement (100) according to claim 1 , wherein said electron beam controller (250) is arranged to control and manipulate said electron beam (220) to influence heating at a selected pixel of a heating position.

6. Additive manufacturing arrangement (100) according to claim 1, wherein said electron source (210) comprises at least one coil (255) configured to manipulate said electron beam (220) by shaping and deflecting said electron beam (220) upon control instructions from said electron beam controller (250) according to said beam adjustment sequence.

7. Additive manufacturing arrangement (100) according to claim 1, wherein said electron beam controller (250) is arranged to control and manipulate said electron beam (220) by adapting at least one electron beam parameter and/or a heating position pattern according to said beam adjustment sequence.

8. Additive manufacturing arrangement (100) according to claim 1, wherein said electron beam parameters comprises: beam power, beam shape, beam spot centre and spot size.

9. Method for additive manufacturing by selective fusion of layers of a three-dimensional product from a powder bed (240) comprising successively formed powder layers, comprising the steps of: exposing a top surface (260) of the powder bed (240) for the electron beam (220) to melt the metal powder to form a melt pool, wherein the electron beam (220) is moved to different heating positions at said powder bed (240); controlling and manipulating said electron beam (220) in accordance with a beam adjustment sequence within a predetermined duration, wherein said predetermined duration is the dwell time of the electron beam (210), the dwell time being the duration of energy deliverance of the beam spot at a pixel, said beam adjustment sequence including different sequence steps each associated with a set of beam parameters.

10. Method additive manufacturing according to claim 10, controlling and manipulating said electron beam (220) in accordance with a beam adjustment sequence including at least two states within a predetermined duration, wherein said at least two states comprising a focused state and a defocused state.

11. Method for additive manufacturing according to claim 10, further comprising controlling and manipulating said electron beam (220) in accordance with said beam adjustment sequence while maintaining the electron beam (220) in a certain heating position at said powder bed (240).

12. Method for additive manufacturing according to claim 10, further comprising controlling and manipulating said electron beam (220) in accordance with said beam adjustment sequence while maintaining the electron beam (220) in a certain heating position at said powder bed (240), and wherein said set of beam parameters of each sequence step includes a beam shape and/or a beam spot centre, wherein beam shape and/or beam spot centre is adjusted in each sequence step in said beam adjustment sequence.

13. Method for additive manufacturing according to claim 10, further comprising controlling and manipulating said electron beam (220) to influence heating at a selected pixel of a heating position.

14. Method for additive manufacturing according to claim 10, further comprising controlling and manipulating said electron beam (220) by shaping and deflecting said electron beam (220) based on control instructions from an electron beam controller (250) according to said beam adjustment sequence.

15. Method for additive manufacturing according to claim 10, further comprising controlling and manipulating said electron beam (220) by adapting at least one electron beam parameter and/or a heating position pattern according to said beam adjustment sequence.

16. Method for additive manufacturing according to claim 10, wherein said electron beam parameters comprises: beam power, beam shape, beam spot centre and spot size.