Systems and methods for using a segmented scan pattern to build large single crystal objects

Abstract

Segmented scan patterns produce 3D printed metallic objects having large scale cubic crystal structures. A first patterned layer is produced by moving a melt pool in a first powder layer along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect. A second patterned layer is produced by moving the melt pool in a second powder layer along a second layer scan pattern that includes a second layer first section, a second layer second section, and a second layer first overlap where the second layer first section and the second layer second section intersect. The second layer first overlap overlies the first layer first section or the first layer second section. The second layer first overlap does not overlie the first layer first overlap.

Description

SYSTEMS AND METHODS FOR USING A SEGMENTED SCAN PATTERN TO BUILDLARGE SINGLE CRYSTAL OBJECTSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims the priority and benefit of U.S. provisional patent application no. 63 / 51 1 ,155, titled “SYSTEMS AND METHODS FOR USING A SEGMENTED SCAN PATTERN TO BUILD LARGE SINGLE CRYSTAL OBJECTS” filed on June 29, 2023. U.S. provisional patent application no. 63 / 511 ,155.TECHNICAL FIELD

[0002] The described aspects are generally related to additive manufacturing, 3D printing, selective laser melting (SLM) printing of 3D objects, and 3D printing of cubic materials. The aspects are also related to controlling melt pool shape and overlap to thereby form directional and single crystal microstructures in a 3D printed object.BACKGROUND

[0003] Objects can be printed by 3D printers using a variety of techniques such as stereolithography (SLA), selective laser melting (SLM), selective laser sintering (SLS), fused deposition modeling (FDM), direct metal printing (DMP), electron beam melting (EBM), directed energy deposition (DED), and laser bed powder fusion (LBPF). The field is developing rapidly with new techniques being developed and known techniques being refined. Many of the techniques operate by forming a patterned layer of material on a substrate and then forming additional layers over previously produced layers. Some techniques (e.g., DED, etc.) produce patterned layers by producing a melt pool and then adding material to the melt pool while moving the melt pool. Some techniques (e.g., SLM, EBPF, etc.) produce patterned layers by laying down a layer of powdered material and then producing the pattern layer of solid material by selectively melting the powdered material. The materials used for additive manufacturing are very often cubic materials. Cubic materialsare materials that form cubic crystal structures having <100> orientations.

[0004] Additive manufacturing is a technology that is merely decades old whereas classical processes are thousands of years old. For example, the bronze age began approximately 5000 years ago and the iron age began 3000 years ago. The classical processes are highly refined because they have been studied and improved for millennia. Systems and methods are needed for producing additively manufactured objects that meet or exceed the material properties exhibited by objects produced using classical processes.BRIEF SUMMARY

[0005] The following summary is provided to facilitate an understanding of some of the innovative features unique to the examples disclosed and is not intended to be a full description. A full appreciation of the various aspects of the examples can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

[0006] One aspect of the subject matter described in this disclosure can be implemented by a method. The method can include depositing a first powder layer. The method can further include producing a first patterned layer by moving a melt pool in the first powder layer along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect. The method may further include depositing a second powder layer on the first patterned layer, producing a second patterned layer by moving the melt pool in the second powder layer along a second layer scan pattern, depositing a third powder layer on the second patterned layer, and producing a third patterned layer by moving the melt pool in the third powder layer along a third layer scan pattern that includes a third layer first section, a third layer second section, and a third layer first overlap where the third layer first section and the third layer second section intersect. The third layer first overlap overlies the first layer first section or the first layer second section, and the third layer first overlap does not overlie the first layer first overlap.

[0007] Another aspect of the subject matter described in this disclosure can be implemented by a system. The system can include a powder feeder configured to produce a first powder layer and a second powder layer by depositing a powder on a powder bed, a beam source configured to produce a melt pool in the powder, and a beam scanner configured to produce a first patterned layer and a second patterned layer by moving the melt pool relative to the powder bed. The first patterned layer is produced by moving the melt pool in the first powder layer along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect, the second patterned layer is produced by moving the melt pool in the second powder layer along a second layer scan pattern that includes asecond layer first section, a second layer second section, and a second layer first overlap where the second layer first section and the second layer second section intersect, the second layer first overlap overlies the first layer first section or the first layer second section, and the second layer first overlap does not overlie the first layer first overlap.

[0008] Yet another aspect of the subject matter described in this disclosure can be implemented by a system. The system can include a deposition means for producing a plurality of powder layers by depositing a powder, and a patterning means for producing a plurality of patterned layers by moving a melt pool through the powder. A first one of the patterned layers is produced by moving the melt pool in a first one of the powder layers along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect. A second one of the patterned layers is produced by moving the melt pool in a second one of the powder layers along a second layer scan pattern. A third one of the patterned layers is produced by moving the melt pool in a third powder layer along a third layer scan pattern that includes a third layer first section, a third layer second section, and a third layer first overlap where the third layer first section and the third layer second section intersect. The second one of the patterned layers is over the first one of the patterned layers and under the third one of the patterned layers, and the third layer first overlap does not overlie the first layer first overlap.

[0009] In some implementations of the methods and devices, the first layer scan pattern includes a plurality of first layer sections and includes a plurality of first layer overlaps where one of the first layer sections intersects another one of the first layer sections, the third layer scan pattern includes a plurality of third layer sections and includes a plurality of third layer overlaps where one of the third layer sections intersects another one of the third layer sections, the third layer sections overlie the first layer sections, and none of the third layer overlaps overlie any of the first layer overlaps. In some implementations of the methods and devices, growth of stray grains in the first layer first overlap is discouraged by moving the melt pool through the first layer overlap twice. In some implementations of the methods and devices, the first layer first section includes a first scan line segment, and the melt pool extends through an entire length of the first scan line segment after the melt pool is movedalong the first scan line segment. In some implementations of the methods and devices, the first layer first section includes a first scan line segment and a second scan line segment, the melt pool extends through an entire length of the first scan line segment after the melt pool is moved along the first scan line segment, the melt pool is moved along the second scan line segment immediately after the melt pool is moved along the first scan line segment, and the melt pool does not extend through the entire length of the first scan line segment after the melt pool is moved along the second scan line segment.

[0010] In some implementations of the methods and devices, the first layer first section includes a first scan line segment and a second scan line segment, the melt pool extends through an entire length of the first scan line segment after the melt pool is moved along the first scan line segment, the melt pool is moved along the second scan line segment immediately after the melt pool is moved along the first scan line segment, the melt pool does not extend through the entire length of the first scan line segment after the melt pool is moved along the second scan line segment, and the melt pool extends from the second scan line segment into the first scan line segment due to lateral heating. In some implementations of the methods and devices, a plurality of lengths of a plurality of scan line segments is used to set a beam power of an energy beam that produces the melt pool. In some implementations of the methods and devices, a map associates a plurality of scan line lengths with a plurality of beam power values, and a plurality of lengths of a plurality scan line segments is used to set a beam power of an energy beam that produces the melt pool in accordance with the map. In some implementations of the methods and devices, a beam power while scanning a first scan line segment does not equal the beam power while scanning a second scan line segment because the first scan line segment and the second scan line segment have different lengths.

[0011] In some implementations of the methods and devices, the first layer first section includes a plurality of scan line segments having a plurality of lengths, and the lengths of the scan line segments are used to set a scan speed of an energy beam that produces the melt pool. In some implementations of the methods and devices, the scan speed has a first speed value while scanning a first one of the scan line segments, the scan speed has a second speed value while scanning a second one of the scan line segments, and the first speedvalue does not equal the second speed value because the first one of the scan line segments and the second one of the scan line segments have different lengths. In some implementations of the methods and devices, a map associates a plurality of scan line lengths with a plurality of scan speed values, the first layer first section includes a plurality of scan line segments having a plurality of lengths, and the lengths of the scan line segments are used to set a scan speed in accordance with the map. In some implementations of the methods and devices, an energy beam is scanned to thereby move the melt pool, the energy beam has a scan speed and a beam power, a series of melt pool images show a melt pool shape, and the scan speed or the beam power are adaptively controlled to obtain the melt pool shape that is a desired melt pool shape.

[0012] In some implementations of the methods and devices, the first layer includes a first scan line segment and a second scan line segment parallel to the first scan line segment, the melt pool extends through an entire length of a first line segment after the melt pool is moved along the first scan line segment, the melt pool is moved along the second scan line segment immediately after the melt pool is moved along the first scan line segment, the melt pool does not extend through the entire length of the first line segment after the melt pool is moved along the second scan line segment, and the melt pool extends from the second scan line segment into the first line segment due to lateral heating. In some implementations of the methods and devices, a plurality of lengths of a plurality of scan line segments is used to set a power of the beam source or a scan speed of the melt pool. In some implementations of the methods and devices, the third layer first overlap overlies the first layer first section or the first layer second section. In some implementations of the methods and devices, growth of stray grains is discouraged by moving the melt pool through the first layer overlap twice.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the examples and, together with the detailed description, serve to explain the examples disclosed herein.

[0014] FIG. 1 is a high-level conceptual figure of a SLM style 3D printer, according to some aspects.

[0015] FIG. 2 is a high level conceptual diagram that illustrates a scan pattern and a melt pool, according to some aspects.

[0016] FIG. 3 is a high level conceptual diagram that illustrates a segmented scan pattern, according to some aspects.

[0017] FIG. 4 is a high level conceptual diagram that illustrates moving a melt pool along a segmented scan pattern, according to some aspects.

[0018] FIG. 5 is a high level conceptual diagram that illustrates overlaps in one layer that do not overlie overlaps in another layer, according to some aspects.

[0019] FIG. 6 is a high level conceptual diagram that illustrates a control system controlling the beam scanner and the beam source, according to some aspects.

[0020] FIG. 7 is a high level conceptual diagram that illustrates a map that associates different scan line lengths with different beam powers or scan speeds, according to some aspects.

[0021] FIG. 8 is a high level conceptual diagram that illustrates adaptively controlling the scan speed or the beam power to obtain a melt pool shape that is a desired melt pool shape, according to some aspects.DETAILED DESCRIPTION

[0022] The particular values and configurations discussed in the following non-limiting examples can be varied and are cited merely to illustrate one or more examples and are not intended to limit the scope thereof.

[0023] Examples will now be described more fully hereinafter with reference to the accompanying drawings. The examples disclosed herein may be instantiated in different forms and should not be construed as limiting the claims; rather, these examples are provided so that this disclosure will be thorough, complete, and will fully convey the scope of the claims to those skilled in the art. Like numbers refer to like elements throughout. A device configured to produce a result may produce that result when the device is in operation.

[0024] The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise" or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.

[0025] Throughout the specification and claims, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, the phrase “in one example” as used herein does not necessarily refer to the same example and the phrase “in another example” as used herein does not necessarily refer to a different example. It is intended that claimed subject matter include combinations of aspects of the examples.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

[0027] It will be understood that the examples described herein are illustrative and not limiting. The aspects may be employed in various examples without departing from the scope of the claims. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of the claims.

[0028] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The use of the term “or” in the claims implicitly includes “and” unless explicitly indicated otherwise. Throughout this application, the term “about” indicates that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

[0029] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0030] The term “or combinations thereof” as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof” is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

[0031] The systems and methods disclosed and claimed herein can be made andexecuted without undue experimentation in light of the present disclosure. While the systems and methods have been described in terms of examples, it will be apparent to those of skill in the art that variations may be applied to the systems and methods and in the steps or in the sequence of steps of the methods described herein without departing from the concept, spirit, and scope of the claims. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the claims.

[0032] FIG. 1 is a high-level conceptual figure of an example of a SLM style 3D printer 100, according to some aspects. A powder feeder may be configured to produce powder layers in a powder bed. In the example, a powder feeder 110 deposits powder 1 12 to produce a powder layer 105 in a powder bed 108. The powder layer that is deposited first, the initial layer, can lie directly on the powder bed or on a substrate that may be placed in the powder bed before the powder layers are deposited. A beam source may be configured to produce a melt pool by producing an energy beam that melts some of the powder thereby producing the melt pool. A beam scanner may be configured to produce patterned layers by moving the melt pool. In the example, a beam scanner 101 can move a beam source 102 or steer an energy beam 1 1 1 that is produced by the beam source 102. The energy beam may be a laser beam, an electron beam, etc. The energy beam 111 produces a melt pool 104 where the energy beam 1 1 1 melts some of the powder in the powder bed 108. The melt pool 104 has a melt pool depth 103. The melt pool depth 103 is illustrated as being large enough to also melt some of the patterned layer 106 directly underneath the powder layer 105. In some implementations the melt pool can extend down through numerous underlying layers. The beam scanner moves the melt pool 104 in a path through the topmost powder layer to selectively melt some of the powder and thereby produce a patterned layer. The powder layer that is deposited first becomes the bottom patterned layer 107. A 3D object is printed by iteratively depositing powder layers and using the energy beam to melt patterns into the powder layers, thereby producing patterned layers.

[0033] FIG. 2 is a high level conceptual diagram that illustrates a scan pattern and a melt pool, according to some aspects. A powder layer 201 has been deposited and is ready to be patterned by moving the melt pool along a scan pattern 206. The scan pattern has a first scan line 207, a second scan line 208, etc. FIG. 2 shows the initial scan line of the scan pattern 206 as the first scan line although any of the scan lines may be referred to as a firstscan line or second scan line. The scan pattern 206 illustrated in FIG. 2 is a bidirectional scan pattern in which the scan direction is changed by 180 degrees from one scan line to the next. A melt pool can be produced by moving the energy beam (e.g., laser beam, electron beam, etc.) along the scan pattern. The energy beam fully melts the material in an area of the layer to produce a fully melted melt pool area 202. The material cools rapidly and crystal grains or dendrites grow in the melt pool as the melt pools cools. The partially melted melt pool area 203 is the portion of the melt pool in which crystal grains or dendrites are growing. The melt pool 104 may thereby include a fully melted melt pool area and a partially melted melt pool area. A patterned area 204 is an area where the melt pool has solidified. A patterned layer 205 is produced by moving the melt pool along the scan pattern 206 and allowing the melt pool to solidify. The figures herein, as seen in FIG. 2, illustrate the fully melted melt pool area 202 as a black area and illustrate the partially melted melt pool area 203 as a gray area.

[0034] FIG. 3 is a high level conceptual diagram that illustrates a segmented scan pattern 301 , according to some aspects. A segmented scan pattern may have two or more sections and one or more overlaps. An overlap is the area where one section intersects another section. The scan pattern 301 illustrated in FIG. 3 is a unidirectional scan pattern in which the scan direction is the same from one scan line segment to the next. The scan pattern 301 includes a first section 302 and a second section 303. The non-limiting example shown in FIG. 3 illustrates the second section 303 being scanned after the first section 302. In practice, either section may be scanned first. Furthermore, one of the sections is not required to be scanned immediately after the other section as is shown in FIG. 3. The first overlap 304 is that area where the first section 302 and the second section 303 intersect. The melt pool will be moved through the first overlap 304 when moving along the first section 302 of the scan pattern and will also be moved through the first overlap 304 when moving along the second section 303 of the scan pattern. As such, the material in the first overlap 304 may be fully melted twice by the energy beam. The melt pool is moved through the first overlap twice to discourage the growth of stray grains where the first section and the second section intersect. An example of stray grains may be dendrites that grow from the end of a scan line segment in a direction that is parallel to the direction of the scan line. Melting the overlap area a second time can discourage the growth of such stray grains.

[0035] FIG. 4 is a high level conceptual diagram that illustrates moving a melt pool along a segmented scan pattern, according to some aspects. The scan pattern has a first section 401 , a second section 402, and a third section 403. In the non-limiting example of FIG. 4, the melt pool is scanned through the first section 401 , then through the second section 402, and then through the third section 403. The powder layer 400 is not yet patterned in sections through which the melt pool has not moved. The melt pool is seen to extend through the entire length of each line segment after the melt pool is moved along that line segment. It is important that the melt pool melts each entire line segment because melting the entire line segment promotes the growth of a large crystalline structure. Here, the issue is that the melt pool cools rapidly, which limits the length of the melt pool. It is segmenting the scan pattern that results in sections wherein the melt pool extends along entire line segments, thereby promoting the growth of large crystal structures. It can also be seen that each section has numerous scan line segments. The melt pool can be moved along a first line segment and then immediately moved along a second line segment that is next to the first line segment. The melt pool extends through the entire length of the first line segment after the melt pool is moved along the first scan line segment, but that portion of the melt pool is rapidly solidifying and may be completely solidified before the melt pool is moved completely along the second line segment. As such, the melt pool may not extend through the entire length of the first line segment after the melt pool is moved along the second scan line segment. However, as seen in FIG. 4, the melt pool may extend from the second line segment into the first line segment due to lateral heating. Lateral heating occurs when the heat of the melt pool moves laterally into material near the melt pool. Melting the previously scanned line or keeping it in a molten state is important because it promotes the growth of crystal structures from one scanned line segment into the next scanned line segment. The required lateral heating is another limit on scan line length because the previously scanned line segment must still be hot in order to be maintained in a molten state or sufficiently melted by lateral heating.

[0036] A first overlap 406 is where the first section 401 and the second section 402 intersect. A second overlap 407 is where the second section 402 and the third section 403 intersect. As discussed above, the material in the overlaps is melted twice by the energybeam. As such, crystal structures growing in the first section that is patterned can grow into the second section that is patterned. A patterned layer 405 remains after the melt pool has been completely moved along all the line segments of all the sections and the layer allowed to completely solidify.

[0037] FIG. 5 is a high level conceptual diagram that illustrates overlaps in one layer that do not overlie overlaps in another layer, according to some aspects. Objects can be 3D printed by repeatedly depositing powder layers and producing patterned layers from the powder layers. The powder layers may be deposited on a substrate or on previously produced patterned layers. The powder layer 400 illustrated in FIG. 4 may be the first powder layer. The first powder layer may be the initial powder layer or a subsequent powder layer. The segmented scan pattern illustrated in FIG. 4 may be an example of the first layer scan pattern such that the first layer scan pattern includes a first layer first section 401 , a first layer second section 402, a first layer third section 403, a first layer first overlap 406, and a first layer second overlap 407. Moving the melt pool along the first layer scan pattern may produce the first patterned layer. A second patterned layer 507 can be produced directly on the first patterned layer 405. The second layer scan pattern can be seen to be orthogonal to the first layer scan pattern. Furthermore, the second layer scan pattern is not segmented because each of the scan lines of the second layer scan pattern is less than a threshold value. The threshold value is a value that allows the melt pool to extend the entire length of the scan line and for lateral heating into the previously scanned line to promote the growth of crystalline structures from the previous scan line into the melt pool.

[0038] A third patterned layer 508 can be produced directly on the second patterned layer 507. The third layer scan pattern can be seen to be parallel to the first layer scan pattern and orthogonal to the second layer scan pattern. Experimentation has shown that large crystals can be produced by rotating the scan patterns from one layer to another as shown in FIG. 5. The third layer scan pattern can be seen to be a segmented scan pattern having a first section, a second section, and a third section. Moving the melt pool along the third layer first section results in the third patterned layer first section 51 1 . In the example of FIG. 5, Moving the melt pool along the third layer second section results in the third patterned layer second section 510. Moving the melt pool along the third layer third section results in the thirdpatterned layer third section 509. The third layer first overlap is where the third layer first section and the third layer second section intersect. The third patterned layer first overlap 513 is located where the melt pool moved through the third layer first overlap. The third layer second overlap is where the third layer second section and the third layer third section intersect. The third patterned layer second overlap 512 is located where the melt pool moved through the third layer second overlap.

[0039] As can be seen in FIG. 5, the overlaps in the third patterned layer do not overlie the overlaps in the first patterned layer. More specifically, the third patterned layer first overlap 513 overlies the first patterned layer 405 but does not overlie the first patterned layer first overlap 406 and does not overlie the first patterned layer second overlap 407. Furthermore, the third patterned layer second overlap 512 overlies the first patterned layer 405 but does not overlie the first patterned layer first overlap 406 and does not overlie the first patterned layer second overlap 407. It is important that none of the overlaps in one layer overlie any of the overlaps in the closest underlying layer (the previous layer), or in many previous layers, in order to encourage the growth of large crystalline structures through the layers. A previous layer may be any of the patterned layers under the topmost layer. The patterned sections that are not in an overlap are more likely to have higher quality crystalline structures than the patterned sections that are in an overlap. As such, the higher quality crystalline structures are more likely to grow from an underlying layer into the overlaps of the topmost layer.

[0040] FIG. 6 is a high level conceptual diagram that illustrates a control system 601 controlling the beam scanner and the beam source, according to some aspects. The control system can be a computer running software for controlling a 3D printer. The computer, while running the control system software, can send control signals to the beam scanner 101 , the beam source 102, and to other components of a 3D printer. Those practiced in the art have long and extensive experience with running control system software on a computer that controls a 3D printer. The control system can store a scan pattern 602. The scan pattern 602 can include a first layer scan pattern 603, a second layer scan pattern 61 1 , a last layer scan pattern 612, and other layer scan patterns. The layer scan patterns can include sections. For example, the first layer scan pattern 603 is shown including a first layer first section 604, a first layer second section 609, a first layer last section 610, and may include many other firstlayer sections. The sections can include pathing data associated with scan speeds and beam powers. For example, the first layer first section 604 is shown including a table that has rows that each include an x coordinate 605, a y coordinate 606, a scan speed value 607, and a beam power value 608. The control system 601 may read a table row and then command the beam scanner 101 and the beam source 102 to set the energy beam to the beam power indicated by the beam power value 608 and to move the melt pool at the scan speed indicated by the scan speed value 607 from its current location to the position indicated by the x coordinate 605 and the y coordinate 606.

[0041] FIG. 7 is a high level conceptual diagram that illustrates a map 701 that associates different scan line lengths with different beam powers or scan speeds, according to some aspects. The amount of energy deposited by the beam into a volume of the material being patterned depends on the beam power and how long the beam touches the volume of material. Here, the energy beam is scanned along the scan pattern to thereby move the melt pool. As such, the amount of energy deposited into a volume depends on the scan speed and the beam power. As discussed above, it is desirable for the melt pool to extend completely through an entire scan line or line segment and it is desirable for lateral heating to melt into the previous scan line. It is also desirable for the melt pool to extend slightly into the previous layer directly underneath the topmost layer. The amount of energy deposited is limited because too much energy simply melts the object being produced, melts too large of a volume thereby reducing print resolution, etc. The beam power 704, the scan speed 703, or both may therefore be a function of scan length 702. The scan length is the length of a line segment in a section or a scan line in a scan pattern. For example, the melt pool moves along entire scan lines while patterning the second patterned layer 507 illustrated in FIG. 5. The melt pool moves along scan line segments while patterning the first patterned layer 405 and the third patterned layer illustrated in FIG. 5. The scan length to scan speed and scan power map 701 may be used to determine the values in the scan pattern 602 shown in FIG. 6. Alternatively, the map 701 may be used to set the beam power and scan speed during a printing operation. In an example, the energy beam produces the melt pool in accordance with the map when a first one of the line segments has a first length 705 that may be looked up in the map 701 to determine a first beam power value 707 and a first scan speed value 708. In another example, the map does not contain an entry for the length and the first beampower value 707 and the first scan speed value 708 are calculated via interpolation. The beam source may be set to the first beam power value 707 while the melt pool is moved along the first one of the line segments. The scan speed of the beam scanner may be set to the first scan speed value 708 while the melt pool is moved along the first one of the line segments. A second one of the line segments may have a second length 706. The beam power or the scan speed used for the second one of the line segments may not equal those used for the first one of the line segments because the first one of the line segments and second one of the line segments have different lengths. The line segments have different lengths when the first length 705 does not equal the second length 706. As such, the second length 706 may be looked up in or calculated from (e.g., via interpolation) the map 701 to determine a second beam power value 709 and a second scan speed value 710. The beam source may be set to the second beam power value 709 while the melt pool is moved along the second one of the line segments. The scan speed of the beam scanner may be set to the second scan speed value 710 while the melt pool is moved along the second one of the line segments. Some implementations may use a single scan speed and vary the beam power. Some implementations may use a single beam power and vary the scan speed. Some implementations may vary the scan speed and the beam power.

[0042] FIG. 8 is a high level conceptual diagram that illustrates adaptively controlling the scan speed or the beam power to obtain a melt pool shape that is a desired melt pool shape, according to some aspects. An imager 809 may image a melt pool 104 and produce melt pool images 806 that are images of the melt pool. The imager 809 can be a video camera operating in the visible light range (visible to humans), operating in an infrared light range, etc. The melt pool images 806 can be a time series of melt pool images such as one image every tenth of a second, 30th of second, etc. The melt pool images 806 can be received by an image analyzer 804 that determines the melt pool shape 802. A melt pool comparator 803 can compare the melt pool shape 802 to a desired melt pool shape 801 . For example, the desired melt pool shape may extend the entire length of the most recent scan line or scan line segment and the melt pool may extend half way (laterally) into the previous scan line or scan line segment. Differences between the observed and the desired melt pool shapes may indicate that the beam power be increased, the beam power be decreased, the scan speed by increased, the scan speed by decreased, etc. A parameter adjuster 805 can produce abeam power adjustment 807 that is sent to the beam source 102 or a scan speed adjustment 808 that is sent to beam scanner 101 . The beam power adjustment 807 and the scan speed adjustment 808 can cause the melt pool 104 to have the desired melt pool shape.

Claims

CLAIMSWhat is claimed is:

1. A method comprising: depositing a first powder layer; producing a first patterned layer by moving a melt pool in the first powder layer along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect; depositing a second powder layer on the first patterned layer; producing a second patterned layer by moving the melt pool in the second powder layer along a second layer scan pattern; depositing a third powder layer on the second patterned layer; and producing a third patterned layer by moving the melt pool in the third powder layer along a third layer scan pattern that includes a third layer first section, a third layer second section, and a third layer first overlap where the third layer first section and the third layer second section intersect, wherein: the third layer first overlap overlies the first layer first section or the first layer second section; and the third layer first overlap does not overlie the first layer first overlap.

2. The method of claim 1 , wherein: the first layer scan pattern includes a plurality of first layer sections and includes a plurality of first layer overlaps where one of the first layer sections intersects another one of the first layer sections; the third layer scan pattern includes a plurality of third layer sections and includes a plurality of third layer overlaps where one of the third layer sections intersects another one of the third layer sections; the third layer sections overlie the first layer sections; and none of the third layer overlaps overlie any of the first layer overlaps.

3. The method of claim 1 , wherein growth of stray grains in the first layer first overlap is discouraged by moving the melt pool through the first layer overlap twice.

4. The method of claim 1 , wherein: the first layer first section includes a first scan line segment; and the melt pool extends through an entire length of the first scan line segment after the melt pool is moved along the first scan line segment.

5. The method of claim 1 , wherein: the first layer first section includes a first scan line segment and a second scan line segment; the melt pool extends through an entire length of the first scan line segment after the melt pool is moved along the first scan line segment; the melt pool is moved along the second scan line segment immediately after the melt pool is moved along the first scan line segment; and the melt pool does not extend through the entire length of the first scan line segment after the melt pool is moved along the second scan line segment.

6. The method of claim 1 , wherein: the first layer first section includes a first scan line segment and a second scan line segment; the melt pool extends through an entire length of the first scan line segment after the melt pool is moved along the first scan line segment; the melt pool is moved along the second scan line segment immediately after the melt pool is moved along the first scan line segment; the melt pool does not extend through the entire length of the first scan line segment after the melt pool is moved along the second scan line segment; and the melt pool extends from the second scan line segment into the first scan line segment due to lateral heating.

7. The method of claim 1 , wherein a plurality of lengths of a plurality of scan line segments is used to set a beam power of an energy beam that produces the melt pool.

8. The method of claim 1 , wherein: a map associates a plurality of scan line lengths with a plurality of beam power values; and a plurality of lengths of a plurality scan line segments is used to set a beam power of an energy beam that produces the melt pool in accordance with the map.

9. The method of claim 1 , wherein a beam power while scanning a first scan line segment does not equal the beam power while scanning a second scan line segment because the first scan line segment and the second scan line segment have different lengths.

10. The method of claim 1 , wherein: the first layer first section includes a plurality of scan line segments having a plurality of lengths; and the lengths of the scan line segments are used to set a scan speed of an energy beam that produces the melt pool.11 . The method of claim 10, wherein: the scan speed has a first speed value while scanning a first one of the scan line segments; the scan speed has a second speed value while scanning a second one of the scan line segments; and the first speed value does not equal the second speed value because the first one of the scan line segments and the second one of the scan line segments have different lengths.

12. The method of claim 1 , wherein: a map associates a plurality of scan line lengths with a plurality of scan speed values; the first layer first section includes a plurality of scan line segments having a plurality of lengths; andthe lengths of the scan line segments are used to set a scan speed in accordance with the map.

13. The method of claim 1 , wherein: an energy beam is scanned to thereby move the melt pool; the energy beam has a scan speed and a beam power; a series of melt pool images show a melt pool shape; and the scan speed or the beam power are adaptively controlled to obtain the melt pool shape that is a desired melt pool shape.

14. A system comprising: a powder feeder configured to produce a first powder layer and a second powder layer by depositing a powder on a powder bed; a beam source configured to produce a melt pool in the powder; and a beam scanner configured to produce a first patterned layer and a second patterned layer by moving the melt pool relative to the powder bed, wherein: the first patterned layer is produced by moving the melt pool in the first powder layer along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect; the second patterned layer is produced by moving the melt pool in the second powder layer along a second layer scan pattern that includes a second layer first section, a second layer second section, and a second layer first overlap where the second layer first section and the second layer second section intersect; the second layer first overlap overlies the first layer first section or the first layer second section; and the second layer first overlap does not overlie the first layer first overlap.

15. The system of claim 14, wherein growth of stray grains is discouraged by moving the melt pool through the first layer overlap twice.

16. The system of claim 14, wherein: the first layer includes a first scan line segment and a second scan line segment parallel to the first scan line segment; the melt pool extends through an entire length of a first line segment after the melt pool is moved along the first scan line segment; the melt pool is moved along the second scan line segment immediately after the melt pool is moved along the first scan line segment; the melt pool does not extend through the entire length of the first line segment after the melt pool is moved along the second scan line segment; and the melt pool extends from the second scan line segment into the first line segment due to lateral heating.

17. The system of claim 14, wherein a plurality of lengths of a plurality of scan line segments is used to set a power of the beam source or a scan speed of the melt pool.

18. A system comprising: a deposition means for producing a plurality of powder layers by depositing a powder; and a patterning means for producing a plurality of patterned layers by moving a melt pool through the powder; wherein: a first one of the patterned layers is produced by moving the melt pool in a first one of the powder layers along a first layer scan pattern that includes a first layer first section, a first layer second section, and a first layer first overlap where the first layer first section and the first layer second section intersect; a second one of the patterned layers is produced by moving the melt pool in a second one of the powder layers along a second layer scan pattern; a third one of the patterned layers is produced by moving the melt pool in a third powder layer along a third layer scan pattern that includes a third layer first section, a third layer second section, and a third layer first overlap where the third layer first section and the third layer second section intersect;the second one of the patterned layers is over the first one of the patterned layers and under the third one of the patterned layers; and the third layer first overlap does not overlie the first layer first overlap.

19. The system of claim 18, wherein the third layer first overlap overlies the first layer first section or the first layer second section.

20. The system of claim 18, wherein growth of stray grains is discouraged by moving the melt pool through the first layer overlap twice.

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