Method for additive manufacturing of an object from powder layers

Abstract

A method of additively manufacturing an object from powder layers is disclosed, the method comprising the steps of: projecting an energy beam as a spot onto a surface of a powder layer (200); scanning the energy beam outwards along a longitudinal direction over a first region of the surface, the energy beam being oriented such that the spot travels in the first region in a path comprising first loops offset along the longitudinal direction, the spot travelling in each first loop in a first rotational direction (202); scanning the energy beam back along the longitudinal direction over a second region of the surface, the energy beam being oriented such that the spot travels in the second region in a path comprising second loops offset along the longitudinal direction, the spot travelling in each second loop in a second rotational direction opposite to the first rotational direction (204).

Description

Technical Field

[0001] The present invention relates to a method for additive manufacturing of an object from a powder layer and an apparatus suitable for performing the method. Background Technology

[0002] Additive manufacturing refers to the process of creating objects by melting layers of powder that are stacked on top of each other. These powder layers correspond to different cross-sections of the object to be manufactured.

[0003] To melt the powder layer, an energy source projects an energy beam in the form of a spot onto the surface of the powder layer, where melting occurs. The energy beam is then controlled to scan the surface, thereby spreading the melting across the entire surface of the powder layer.

[0004] Typically, the energy beam scans different regions of the surface along the longitudinal direction and alternately in outward and return directions.

[0005] Specifically, it was proposed to control the energy source so that the light spot does not travel in each region in a perfectly linear translation along the longitudinal direction, but rather in a movement that includes both translational movement along the longitudinal direction and oscillating movement (called "oscillation"). The oscillating movement specifically oscillates along the transverse direction to expand the molten pool.

[0006] Various oscillatory shifts have been proposed.

[0007] One of the various oscillating movements (often referred to as the "circular pattern") causes the light spot to follow a trajectory that includes loops that are offset from each other in the longitudinal direction.

[0008] Figure 1 The trajectory followed by the light spot during the execution of the method utilizing this circular pattern is shown. Figure 1 In the diagram, the vertical direction is horizontal, and the horizontal direction is vertical. The outward direction is from left to right, and the return direction is from right to left. Figure 1 Four consecutive loops are presented, located in four different regions. Two of the consecutive loops in the four regions travel outwards, and the other two travel in a returning direction, as indicated by the four dashed arrows. The light spot travels in each loop with a constant direction of rotation. The direction of rotation is the same for each of the four regions (and specifically for each loop). Therefore, two adjacent consecutive loops are connected end-to-end. Summary of the Invention

[0009] The purpose of this invention is to enable a more uniform distribution of energy provided by an energy beam to the powder layer during additive manufacturing without reducing manufacturing time.

[0010] Therefore, in a first aspect, a method for additively manufacturing an object from a powder layer is proposed, comprising the following steps:

[0011] - Projecting an energy beam as a spot onto the surface of the powder layer to melt the powder.

[0012] - An energy beam scans a first region of the surface along a longitudinal scanning direction and in an outward direction, and during the scanning of the first region, the energy beam is oriented such that the light spot travels in the first region along a trajectory comprising first loops offset relative to each other along the longitudinal scanning direction, the light spot traveling in each first loop along a first rotation direction.

[0013] - An energy beam scans a second region of the surface along a longitudinal scanning direction and in a return direction opposite to the outward direction. The second region is adjacent to the first region along a transverse scanning direction perpendicular to the longitudinal scanning direction. During scanning of the second region, the energy beam is oriented such that the light spot travels in the second region along a trajectory including a second loop offset from each other along the longitudinal scanning direction. The light spot travels in each second loop along a second rotation direction opposite to the first rotation direction.

[0014] The inventors noticed that, due to the asymmetrical shape of the loop the light spot travels through, more energy is deposited at the bottom of the loop than at its top. Therefore, when... Figure 1 As shown, when two adjacent continuous loops are connected end to end, the energy deposited on the powder layer varies greatly in the lateral direction: the energy is higher near the bottom of the facing loop and lower near the top of the facing loop.

[0015] The direction of travel of the loop is changed between the first and second regions, so that consecutive first loops and consecutive second loops no longer resemble... Figure 1 Instead of being connected end-to-end, the first loop is oriented in the same direction along the lateral direction. Therefore, the bottom of the first loop is close to the top of the second loop, or vice versa, which reduces energy variation along the lateral direction. This is why energy deposition is more uniform.

[0016] Furthermore, scanning the first region outward and the second region in the return direction allows for rapid scanning of both regions. This is why the improved uniformity provided by the method according to the first aspect does not affect its execution speed.

[0017] The method according to the first aspect may have the following optional features, which may be considered individually or in combination where such combination is technically feasible.

[0018] Preferably, at least two loops in the first loop and / or at least two loops in the second loop intersect.

[0019] Preferably, at least two loops in the first loop and / or at least two loops in the second loop have the same size.

[0020] Preferably, the continuous second loop is a certain distance away from the continuous first loop in the lateral scanning direction.

[0021] Preferably, at least one of the loops extends within an amplitude between 100 micrometers and 2 millimeters, measured along the transverse scanning direction.

[0022] Preferably, the energy beam oscillates along the transverse scanning direction at a frequency of at least 1 kHz.

[0023] Preferably, the energy beam is a laser beam or an electron beam.

[0024] In a second aspect, an apparatus for additively manufacturing objects from powder layers is also proposed, the apparatus comprising an energy source configured as follows:

[0025] - Projecting an energy beam as a spot onto the surface of the powder layer to melt the powder.

[0026] - Control the energy beam to scan a first region of the surface along a longitudinal scanning direction and in an outward direction, and during the scanning of the first region, direct the energy beam such that the light spot travels in the first region along a trajectory comprising first loops offset relative to each other along the longitudinal scanning direction, the light spot traveling in each first loop along a first rotation direction.

[0027] - Control the energy beam to scan a second region of the surface along the longitudinal scanning direction and in a return direction opposite to the outward direction. The second region is adjacent to the first region along a transverse scanning direction perpendicular to the longitudinal scanning direction. During scanning the second region, the energy beam is oriented such that the light spots travel in the second region along a trajectory including second loops offset from each other along the longitudinal scanning direction. The energy beam travels in each second loop along a second rotation direction opposite to the first rotation direction. Attached Figure Description

[0028] Other features, objects, and advantages of the present invention will become apparent from the following description, which is illustrative and non-limiting in nature and should be read in conjunction with the accompanying drawings, in which:

[0029] Figure 1 (As already discussed) This shows the trajectory followed by the light spot obtained by projecting an energy beam onto a surface using existing techniques.

[0030] Figure 2 This is a schematic diagram of the additive manufacturing apparatus in the first embodiment.

[0031] Figure 3 yes Figure 2 The above is a perspective view of the additive manufacturing apparatus.

[0032] Figure 4 This is a perspective view of the additive manufacturing apparatus in the second embodiment.

[0033] Figure 5 This is a flowchart of the steps of the additive manufacturing method in the first embodiment.

[0034] Figure 6 Shown in about Figure 4 The trajectory followed by the light spot obtained by the energy beam being projected onto the surface during the execution of the method.

[0035] In all the accompanying drawings, similar elements have the same reference numerals. Detailed Implementation

[0036] Additive manufacturing equipment

[0037] refer to Figure 2 and Figure 3 The additive manufacturing apparatus includes an energy source 1 and a support member 140 according to the first embodiment.

[0038] The support member 140 has a free surface (which is generally flat) extending in two directions: a longitudinal direction and a transverse direction perpendicular to the longitudinal direction. In the following text, by convention, X represents the longitudinal direction and Y represents the transverse direction.

[0039] The free surface of the support 140 functions as a support surface 140 for the powder layer 150 or multiple powder layers 150 stacked on top of each other.

[0040] Generally, the energy source 1 is adapted to project an energy beam toward the support 140. When the powder layer 150 is deposited on the support 140, the energy beam is projected onto the upper surface of the powder layer 150 in the form of a light spot.

[0041] Energy source 1 specifically includes a generating device 110 configured to generate an energy beam. For example, generating device 110 is a laser source; thus, the generated energy beam is a laser beam containing photons, or in other words, a light beam. Alternatively, generating device 110 is of the electron beam melting (EBM) type, i.e., a type suitable for generating electron beams. In the following, the case of a laser beam is used without limitation.

[0042] The energy source 1 further includes a focusing device suitable for adjusting the focusing of the beam. Thus, the focusing device is able to change the size of the spot of the energy beam projected onto the upper surface of the powder layer 150 deposited on the support 140.

[0043] For example, the focusing device includes a focusing element 1102 and a focusing lens 1101, the focusing lens 1101 being translatable relative to the focusing element parallel to the optical axis of the lens. The focusing lens 1101 is arranged downstream of the energy beam generating device 110. In the following text, the terms "upstream" and "downstream" implicitly refer to the direction of propagation of the energy beam in the optical path from the generating device 110 to the support member 140.

[0044] The focusing device includes an actuator for moving the focusing lens 1101 relative to the focusing element 1102.

[0045] The energy source 1 further includes a scanning device 130, which is adapted to orient the energy beam such that the light spot projected by the energy beam can move relative to the support 140 on the surface of the powder layer 150 in both longitudinal and transverse directions.

[0046] The scanning device 130 is located downstream of the focusing device.

[0047] For example, the scanning device 130 includes a first scanning mirror 131 and a second scanning mirror 132. The first scanning mirror 131 is rotatably movable relative to the support 140 about a first rotation axis 133, and the second scanning mirror 132 is rotatably movable relative to the support 140 about a second rotation axis 134, which is different from the first rotation axis. For example, the first rotation axis 133 is in the longitudinal direction, while the second rotation axis 134 is in the transverse direction. One of the two scanning mirrors 131 and 132 is arranged downstream of the other scanning mirror, such that the energy beam from the generating device 110 is reflected sequentially by the two scanning mirrors before being redirected toward the support 140.

[0048] Alternatively, the scanning device 130 includes a single scanning mirror that is rotatably movable relative to the support 140 about a first rotation axis 133 and a second rotation axis 134. In this case, the single scanning mirror is arranged such that the energy beam from the generating device 110 is reflected by the scanning mirror before being redirected toward the support 140.

[0049] The scanning device 130 also includes at least one actuator (one actuator for each scanning mirror). The function of each actuator is to rotate the scanning mirror within a scanning angle range.

[0050] For example, the scanning angle is ranged to allow the light spot to cover the entire surface of the powder layer 150, or at least a large portion of the surface.

[0051] For a given configuration of the scanning apparatus, the central axis of the energy beam emitted from the generating device 110 intercepts the surface of the support member 140 at a specific point. Therefore, there is a mathematical relationship between the coordinates (x, y) of this point and the angular positions of the scanning mirrors 131 and 132.

[0052] Specifically, the scanning device 130 is configured to cause the light spot projected onto the surface of the powder layer 150 to move alternately along the longitudinal scanning direction, in an outward direction and in a return direction opposite to the outward direction, the selection of the longitudinal scanning direction being independent of the longitudinal and transverse directions of the support member 140.

[0053] In a first embodiment, the energy source 1 further includes an oscillation device 120 adapted to cause oscillation of an energy beam emitted from the generating device 110 and thus also cause oscillation of a spot of light projected along at least one oscillation direction onto the surface of a powder layer 150 deposited on the support 140.

[0054] For example, the oscillation device 120 includes an oscillation mirror that is rotatably movable relative to the support 140 about two different oscillation axes 122, 123.

[0055] The oscillation device 120 further includes an actuator adapted to cause the oscillating mirror to oscillate at a given fixed or variable frequency.

[0056] The actuator of the oscillation device 120 is configured to cause the oscillating mirrors to oscillate around two oscillation axes 122 and 123 within a range of two oscillation angles smaller than the scanning angle, within which each scanning mirror 131 and 132 is rotatably movable about axes 133 and 134. The range of oscillation angles used by the oscillation device 120 is suitable for causing the projected light spot to oscillate with an amplitude between 100 micrometers and 2 millimeters.

[0057] The scanning device 130 and the oscillation device 120 are configured to cooperate such that the light spot can move on the surface of the powder layer 150 deposited on the support 140 with a movement including a translational movement caused by the scanning device 130 and an oscillating movement caused by the oscillation device 120. In other words, the oscillating movement modulates the translational movement caused by the scanning device 130.

[0058] The oscillation device 120 is arranged upstream of the scanning device 130. In other words, the energy beam from the generating device 110 is reflected by the oscillating mirror before reaching the scanning device 130.

[0059] For example, the oscillation device 120 is arranged downstream of the focusing device.

[0060] For example, the laser source 110, the modulation device 120, and the scanning device 130 are arranged such that the surface melting rate (that is, the surface area of ​​the powder layer 150 covered by the laser spot per unit time) is greater than 1000 cm⁻¹. 2 / min, for example, greater than 2000cm 2 / min, for example, greater than 4000cm 2 / min, for example, less than 15000cm 2 / min, for example, less than 10000cm 2 / min, for example, 6000cm 2 On the order of / min.

[0061] For example, the modulation device 120 and the scanning device 130 are configured such that the moving speed of the light spot is between 0.5 and 10 m / s, for example, between 1 and 5 m / s, for example, equal to 1 or 2 m / s.

[0062] The energy source 1 further includes a control unit (not shown) configured to control the focusing device, the scanning device 130, and the oscillation device 120. This control unit is specifically configured to control the corresponding actuators of these different devices.

[0063] The control unit may include or be connected to a memory storing a table of pre-calculated values ​​of focusing parameters for different coordinate pairs (x, y) in a plane of the free surface of the support 140. Therefore, when the light spot is centered at a point at coordinates (x, y) on the surface of the support, the control unit is configured to control the focusing device using the focusing parameter values ​​associated with that coordinate pair from the table of pre-calculated values.

[0064] Figure 4 A second embodiment of the energy source 1 is shown. The second embodiment differs from the first embodiment in that it does not include the oscillation device 120. On the other hand, in the second embodiment, the scanning device 130 is configured (in itself) such that the light spot can move on the surface of the powder layer 150 deposited on the support 140 with a movement including translational movement caused by the scanning device 130 and oscillating movement (which, if present in the second embodiment, is caused by the oscillation device 120). This is achieved by oscillating one or more scanning mirrors.

[0065] Additive manufacturing methods

[0066] refer to Figure 4 The additive manufacturing method using the above-mentioned apparatus includes the following steps.

[0067] At least one powder layer 150 is deposited on the support 140, such as Figure 1As shown. The powder layer 150 has free surfaces extending along the longitudinal and transverse directions of the support 140.

[0068] For example, the particle size of the powder particles is between 10 and 100 μm, for example, between 20 and 60 μm, for example, equal to 40 μm.

[0069] For example, the material of each powder layer 150 has a strength between 0.5 and 10 J / mm. 2 Flux between, for example, between 1 and 5 J / mm 2 Between, for example, equal to 2J / mm 2 .

[0070] The material of powder layer 150 or each powder layer 150 may include titanium and / or aluminum and / or chromium-nickel-iron alloy and / or stainless steel and / or maraging steel.

[0071] The generating device 110 is activated to emit an energy beam. Before the energy beam is projected as a spot onto the free surface of the powder layer 150, it passes through a focusing device, an oscillating device 120 (if the energy source 1 is present), and a scanning device 130 (step 200). As a result, the powder layer 150 is heated at the spot to the point that its particles melt.

[0072] In addition, the focusing device adjusts the focusing of the energy beam to reduce the size of the light spot, thereby making the energy transmitted by the energy beam more concentrated.

[0073] The scanning device 130 directs the energy beam such that the light spot translates outward along the longitudinal scanning direction within a first region of the surface. This translational movement... Figure 6 The dashed arrow in the middle indicates (step 202).

[0074] During step 202, the scanning device 130 or the oscillation device 120 oscillates the energy beam, such that the translational movement is modulated by the oscillating movement. This oscillating movement includes a transverse oscillation component along a transverse scanning direction perpendicular to the longitudinal scanning direction and a longitudinal oscillation component along the longitudinal scanning direction. In other words, this oscillating movement causes the light spot to oscillate on the surface of the powder layer 150 not only along the transverse scanning direction but also along the longitudinal scanning direction.

[0075] When energy source 1 conforms to the first embodiment, the oscillation movement is caused by the oscillation device 120. When energy source 1 conforms to the second embodiment, the oscillation movement is caused by the scanning device 130.

[0076] The two oscillating components preferably oscillate at the same frequency. If the two components are sinusoidal, the oscillation can be elliptical.

[0077] Due to the oscillating component and the outward translational movement, in the first region, the light spot follows a trajectory that includes a continuous first loop that is offset from each other along the longitudinal scanning direction.

[0078] Each loop has nodes that serve as points through which the light spot passes twice. Furthermore, each loop comprises an upstream section, a hairpin-shaped middle section, and a downstream section. The light spot travels through the various sections of the loop in the following order: upstream section, nodes, hairpin-shaped middle section, nodes (again), and finally the downstream section. This downstream section connects to the upstream section of the next loop. While traveling through the loop, the light spot always rotates around the center point of the loop in the same direction of rotation (referred to as the first rotation direction).

[0079] Each loop includes a bottom formed by its upstream portion, downstream portion, and nodes. Each loop also includes a top formed by its intermediate portion. Due to the asymmetry of the shape, the amount of energy deposited by the energy beam at the bottom of the loop (especially near the nodes) is greater than the amount of energy deposited at the top of the loop.

[0080] exist Figure 5 In the image, the vertical scanning direction is horizontal, the outward direction is from left to right, and the first rotation direction is counterclockwise. Therefore, it can be seen that the bottom edges of each element in the first loop are located below the top edge of the first loop.

[0081] If the two components of the oscillating motion have the same amplitude, the oscillating motion becomes circular. Therefore, each first loop has a more circular form.

[0082] Preferably, at least one first loop extends within a height between 100 micrometers and 2 millimeters (measured along the lateral scanning direction). This height corresponds to the amplitude of the lateral component of the oscillating movement.

[0083] Furthermore, preferably, the scanning device 130 (in the second embodiment of energy source 1) or the oscillation device 120 (in the first embodiment of energy source 1) causes the light spot to oscillate in the lateral direction at a frequency of at least 1 kHz. When the energy beam is a laser beam, this frequency is typically between 1 kHz and 10 kHz, or when the energy beam is an electron beam, this frequency is typically between 1 kHz and 100 kHz.

[0084] All the first ring routes travel along the first rotation direction of the light spot.

[0085] Preferably, all the first loops have the same dimensions (the same height between their bottom and top, measured in the lateral direction, and / or the same width, measured in the longitudinal direction).

[0086] The first loop intersects with at least two other loops, meaning that the current first loop crosses the previous loop at at least two intersection points. Preferably, all first loops intersect in pairs.

[0087] The continuous first loop extends a certain length along the longitudinal scanning direction and a certain width along the transverse scanning direction.

[0088] Then, the scanning device 130 directs the energy beam such that the light spot moves along the lateral scanning direction (e.g., translation) so that the light spot reaches the second region adjacent to the first region (e.g., in the second region). Figure 5 In the case shown, above the first region.

[0089] Then, the scanning device 130 directs the energy beam so that the light spot moves in the second region along the longitudinal scanning direction (but in the return direction opposite to the outward direction) (step 204).

[0090] During step 204, the scanning device 130 or the oscillation device 120 oscillates the energy beam, such that the translational movement is modulated by the oscillation movement, so that in the second region, the light spot follows a trajectory comprising a continuous second loop offset from each other along the longitudinal scanning direction. At this time, all the first loops travel along the second rotational direction of the light spot.

[0091] Regarding step 202, when energy source 1 conforms to the first embodiment, the oscillating movement is caused by the oscillation device 120; or, when energy source 1 conforms to the second embodiment, the oscillating movement is caused by the scanning device 130. The second rotation direction is opposite to the first rotation direction. The change in the direction of loop travel is typically obtained by utilizing oscillation parameters used to oscillate the energy beam.

[0092] exist Figure 5 In the second loop, the return direction is from right to left, and the second rotation direction of the light spot is clockwise. Therefore, the bottoms of each loop are located below the top of the same second loop, just as in the case of the first loop discussed above. Consequently, the energy transferred from the energy beam to the powder layer 150 is distributed more evenly across the combination of the first and second regions.

[0093] Preferably, at least one second loop extends within a height between 100 micrometers and 2 millimeters (measured along the lateral scanning direction). This height corresponds to the amplitude of the lateral component of the oscillating movement.

[0094] Furthermore, preferably, the energy source 1 causes the light spot to oscillate in the second region along the lateral scanning direction at a frequency of at least 1 kHz. When the energy beam is a laser beam, this frequency is typically between 1 kHz and 10 kHz, or when the energy beam is an electron beam, this frequency is typically between 1 kHz and 100 kHz.

[0095] Preferably, all second loops have the same dimensions (the same height between their bottom and top, measured along the lateral scanning direction, and / or the same width, measured along the longitudinal scanning direction).

[0096] At least two loops of the second ring road intersect. Preferably, all second ring roads intersect in pairs.

[0097] The second consecutive loop is a certain distance from the first consecutive loop (e.g.) Figure 5 (As shown). Alternatively, at least one second loop passes through the first loop.

[0098] The above steps (especially steps 202 and 204) are repeated alternately, thereby covering more areas that are adjacent to each other along the lateral scanning direction. Figure 5 (The four regions are represented).

Claims

1. A method for additively manufacturing an object from a powder layer, comprising the following steps: • An energy beam is projected onto the surface of the powder layer in the form of a light spot to melt the powder (200). • An energy beam scans a first region of the surface along a longitudinal scanning direction and in an outward direction, and during the scanning of the first region, the energy beam is directed such that the light spot travels in the first region along a trajectory comprising a first loop offset relative to each other along the longitudinal scanning direction, the light spot traveling in each first loop along a first rotation direction (202). • An energy beam scans a second region of the surface along a longitudinal scanning direction and in a return direction opposite to the outward direction. The second region is adjacent to the first region along a transverse scanning direction perpendicular to the longitudinal scanning direction. During scanning the second region, the energy beam is oriented such that the light spot travels in the second region along a trajectory including a second loop offset from each other along the longitudinal scanning direction. The light spot travels in each second loop along a second rotation direction opposite to the first rotation direction (204).

2. The method according to the preceding claim, wherein, At least two loops in the first ring road and / or at least two loops in the second ring road intersect.

3. The method according to any one of the preceding claims, wherein, At least two loops in the first loop and / or at least two loops in the second loop have the same dimensions.

4. The method according to claim 1, wherein, The second loop is a certain distance from the first loop in the lateral scanning direction.

5. The method according to claim 1, wherein, At least one of the loops extends within an amplitude between 100 micrometers and 2 millimeters, measured along the transverse scanning direction.

6. The method according to claim 1, wherein, The energy beam oscillates along the transverse scanning direction at a frequency of at least 1 kHz.

7. The method according to claim 1, wherein, The energy beam is either a laser beam or an electron beam.

8. An apparatus for additively manufacturing an object from a powder layer, the apparatus comprising an energy source configured to project an energy beam in the form of a light spot onto the surface of the powder layer to melt the powder, the energy source including a control unit configured to: • The energy beam is controlled to scan a first region of the surface along a longitudinal scanning direction and in an outward direction, and during the scanning of the first region, the energy beam is oriented such that the light spot travels in the first region along a trajectory comprising first loops offset relative to each other along the longitudinal scanning direction, the light spot traveling in each first loop along a first rotation direction. • Control the energy beam to scan a second region of the surface along the longitudinal scanning direction and in a return direction opposite to the outward direction. The second region is adjacent to the first region along a transverse scanning direction perpendicular to the longitudinal scanning direction. During scanning the second region, the energy beam is oriented such that the light spots travel in the second region along a trajectory including second loops offset from each other along the longitudinal scanning direction. The energy beam travels in each second loop along a second rotation direction opposite to the first rotation direction.

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