Coated powder particles for improved additively manufactured parts

Abstract

The present invention relates to a coated powder particle for improved additive manufacturing parts. The coated powder particle for additive manufacturing includes a base polymer layer formed of a base polymer material and a coating polymer layer formed of a coating polymer material. At least the coating polymer material is susceptible to dielectric heating in response to electromagnetic radiation, thereby promoting fusion between adjacent particles in the coated powder particle deposited during the additive manufacturing process. Specifically, when electromagnetic radiation is applied to at least one interface region between adjacent particles in the coated powder particle, the polymer coating layer melts to diffuse across the interface region, thereby preventing the formation of voids. The base polymer material and the coating polymer material may also have similar melting points and compatible solubility parameters to further promote fusion between particles.

Description

Technical Field

[0001] The present disclosure relates to additive manufacturing apparatus and methods, and in particular to powder-based additive manufacturing. The additive manufacturing processes disclosed herein can be used to produce parts including environmental control ducts, door panels, tools, jigs, fixtures, etc. Examples of the present disclosure can be used in a variety of potential applications, especially in the transportation industry, including, for example, aerospace, marine, automotive, and, for example, housings for auxiliary power units (APUs). Background Art

[0002] Depending on the performance requirements of the component and the availability of manufacturing equipment, various manufacturing techniques can be used to manufacture components and other components. Selective laser sintering (SLS) and selective laser melting (SLM) are powder-based additive manufacturing technologies that can be used to build components, in which layers of powder are maintained at an elevated temperature and selectively sintered or melted using a laser. Once a first build layer is formed, successive build layers are formed on top of the first build layer using a similar process until the desired three-dimensional object is completed. The powders used in these processes are typically formed of thermoplastics, polycarbonates, or other similarly constructed materials. Powder-based additive manufacturing, such as SLS and SLM, can introduce voids between powder particles within a build layer and between adjacent build layers formed during the process, resulting in reduced structural integrity of the object. Summary of the invention

[0003] According to one aspect of the present disclosure, a coated powder particle for an additive manufacturing process is provided. The coated powder particle comprises: a base polymer layer formed of a base polymer material having a first dielectric loss factor; and a coating polymer layer surrounding the base polymer layer and formed of a coating polymer material having a second dielectric loss factor, wherein the second dielectric loss factor of the coating polymer material is greater than the first dielectric loss factor of the base polymer material.

[0004] According to another aspect of the present disclosure, a method for manufacturing coated powder particles for an additive manufacturing process includes: advancing a plurality of powder particles through a chamber, each of the plurality of powder particles being formed of a base polymer material; applying a liquid coating to the exterior of each of the plurality of powder particles, the liquid coating being formed of a coating polymer material; and drying the liquid coating on the plurality of powder particles to form a plurality of coated powder particles. Each of the plurality of coated powder particles includes a base polymer layer formed of the powder particles and a coating polymer layer formed of the dried liquid coating.

[0005] According to another aspect of the present disclosure, a method for manufacturing an object by fusion powder manufacturing includes: forming coated powder particles by the following steps: advancing a plurality of powder particles through a chamber, each of the plurality of powder particles being formed of a base polymer material; applying a liquid coating to the exterior of each of the plurality of powder particles, the liquid coating being formed of a coating polymer material; and drying the liquid coating on the plurality of powder particles to form a plurality of coated powder particles, so that each of the plurality of coated powder particles includes a base polymer layer formed by the powder particles and a coating polymer layer formed by the dried liquid coating. The method also includes: depositing the coated powder particles into a first build layer on a substrate; heating a selected portion of the first build layer; depositing the coated powder particles into a second build layer above the first build layer on a substrate; heating a selected portion of the second build layer; and dielectrically heating at least the coating polymer layer of the coated powder particles in the selected portions of the first build layer and the second build layer using electromagnetic radiation, thereby fusing adjacent particles in the coated powder particles across an interface region.

[0006] The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The novel features which are believed to be characteristic of the illustrative embodiments are set forth in the appended claims. However, the illustrative embodiments and the preferred mode of use, further objects and advantages thereof will be best understood by reference to the following detailed description of illustrative examples of the disclosure when read in conjunction with the accompanying drawings, in which:

[0008] Figure 1 is a schematic diagram of an apparatus for converting powder particles into coated powder particles.

[0009] Figure 2 is an illustration of an exemplary coated powder particle formed according to a method of making a coated powder particle.

[0010] Figures 3 to 7 An example of a method of forming an object using coated powder particles according to the present invention is shown. DETAILED DESCRIPTION

[0011] The following detailed description is directed to powder-based additive manufacturing techniques, such as selective laser sintering (SLS) or selective laser melting (SLM). Examples disclosed herein include coated powder particles for use in such processes, methods for forming coated powder particles, and methods for building objects using coated powder particles in additive manufacturing processes. The coated powder particles include particles having a base polymer layer formed of a base polymer material, the base polymer layer being surrounded by a coating polymer layer formed of a coating polymer material. The coated powder particles are susceptible to selective heating, such as dielectric heating using electromagnetic radiation, to increase the strength of the constructed object.

[0012] definition

[0013] "Fused Filament Fabrication" (FFF) is an additive manufacturing technology used to build up layers to form products and, for example, three-dimensional products, prototypes or models. The process can be quickly used for rapid prototyping and manufacturing to build up molten material layer by layer to produce models, products or similar objects.

[0014] As used herein, the term "filament" refers to a feedstock having an elongated, thread-like shape used in an additive manufacturing process.

[0015] The term "powder coating" or "powder coated" or similar terms herein refers to a type of coating that is applied, for example, as a dry powder, and is typically applied electrostatically and then cured via heat, electromagnetic radiation such as microwaves, or other curing sources. The powder may be a thermoplastic, a thermosetting polymer, or other similar polymer or material.

[0016] As used herein, the phrases "selective laser sintering" or "selective laser melting" refer to an additive manufacturing process that uses a laser to sinter powdered material, the laser is pointed into space, and the 3D model is used as a pattern to bond the material together to create a solid structure. Typically, the powdered material is nylon, polyamide, or a similar material.

[0017] Reference is made to the accompanying drawings which form a part hereof and which show by way of illustration, detailed description or example. In all drawings, like reference numerals represent like elements.

[0018] Now turning to the attached figure, Figure 1 An apparatus 2 for converting powder particles 4 into coating powder particles 6 is shown, which can be used in an additive manufacturing process to build an object with improved structural integrity. Specifically, the apparatus 2 includes a coating chamber 8 having a sidewall 10 and a base 12. A perforation 14 is formed in the base 12 to allow air from a compressed air source 16 to enter the coating chamber 8. A nozzle 18 is disposed within the coating chamber 8 and is fluidly coupled to a coating supply 20.

[0019] In operation, powder particles 4 are placed at the bottom of coating chamber 8. Pressurized air source 16 is operated to generate airflow 22 that blows powder particles 4 through coating chamber 8. Simultaneously, coating supply source 20 is operated to spray coating 24 from nozzle 18 and throughout coating chamber 8, thereby coating powder particles 4 with coating 24. In some examples, positively or negatively charged ions may also be dispersed from nozzle 18 to facilitate coating of powder particles 4 with coating 24. Coating 24 may be supplied in a liquid phase and subsequently dried and hardened on powder particles 4. Ultimately, apparatus 2 produces coated powder particles 6 having base polymer layer 26 and coating polymer layer 28, as shown in FIG. Figure 2 Best shown in .

[0020] The materials used to form the base polymer layer 26 and the coating polymer layer 28 of the coated powder particles 6 allow for selective heating during the powder particle-based additive manufacturing process, thereby promoting interlayer chain diffusion and bonding, so that the resulting built object has improved structural integrity. As discussed in more detail below, the materials used for the base polymer layer 26 and the coating polymer layer 28 can be selected based on relative responsiveness to dielectric heating and the proximity of melting points and solubility parameters.

[0021] With respect to responsiveness to dielectric heating, the materials used in the coating powder particles 6 can be selected so that the coating polymer layer 28 is more susceptible to heating in response to electromagnetic radiation than the base polymer layer 26. A property known as the dielectric loss factor (also known as the dissipation factor, and represented by the symbol tan δ) quantifies the ability of a material to dissipate applied electromagnetic energy in the form of heat. A material with a higher dielectric loss factor will heat up more in response to an applied electromagnetic field than a material with a lower dielectric loss factor. In order to focus the heating on the outer surface of the coating powder particles 6, the coating polymer layer 28 is formed of a coating polymer material having a higher dielectric loss factor than the base polymer material used for the base polymer layer 26. In some examples, the tan δ value of the coating polymer material is at least about 50 times the tan δ value of the base polymer material. Additionally or alternatively, the base polymer material has a tan δ value of less than .05, and the coating polymer material may have a tan δ greater than .05.

[0022] The coating powder particles 6 can also use materials for the base polymer layer 26 and the coating polymer layer 28 with similar melting points, which improves the strength of the built object formed by the building layer of the coating powder particles 6 deposited during the additive manufacturing process. As described above, the coating polymer material has a higher dielectric loss factor, so it directly generates heat in response to the application of electromagnetic energy. The base polymer material can be selected so that it has a melting point close to the melting point of the coating polymer material, so that heating the coating polymer layer 28 by electromagnetic energy will then heat at least the outer part of the base polymer layer 26. This indirect heating of the base polymer layer 26 causes the base polymer layer 26 to remain in a softened and / or molten state for a long period of time, thereby promoting the increased diffusion and bonding between the adjacent beads of the coating filament 10 after the adjacent particles in the coating powder particles 6 are deposited on the substrate. The melting points of the base polymer material and the coating polymer material preferably allow the formation of solid and liquid forms. In some examples, the base polymer material has a first melting point, the coating polymer material has a second melting point, and the difference between the first melting point of the base polymer material and the second melting point of the coating polymer material is within 20 degrees Celsius. It has been found that materials with melting points within about 20 degrees Celsius, or about 18 degrees Celsius, or about 15 degrees Celsius generate sufficient heat to prolong the molten state of the base polymer layer 26, thereby promoting diffusion and bonding between the deposited and heated coating powder particles 6 during additive manufacturing.

[0023] The materials selected for base polymer layer 26 and coating polymer layer 28 may also have compatible solubility parameters, further facilitating bonding between adjacent particles in coating powder particles 6 when used in an additive manufacturing process. For example, the coating polymer material may be immiscible with the base polymer material to prevent phase separation and facilitate fusion of base polymer layers of adjacent particles during additive manufacturing. In some examples, the base polymer material has a first solubility parameter, the coating polymer material has a second solubility parameter, and the difference between the second solubility parameter and the first solubility parameter is within about 10 J / cc. 0.5 It has been found that the solubility parameters are within about 10 J / cc of each other. 0.5 , or about 8J / cc 0.5 , or about 5J / cc 0.5 The materials within advantageously promote mixing when heated during the additive manufacturing process.

[0024] Taking the above factors into consideration, suitable base polymer materials include polyethylene, polyethylene terephthalate, polypropylene, polyamide, polyetheretherketone, polyphenylene sulfide, polyetherimide, polystyrene, acrylonitrile / butadiene / styrene, polyacrylate, polyacrylonitrile, polycarbonate or any mixture thereof.

[0025] Suitable coating polymer materials include polyvinyl alcohol, polyvinylidene fluoride, polyurethane, polyamideimide, polyamide, polyvinyl chloride, acrylic acid, cellulose esters, or mixtures thereof. Other examples of suitable coating polymer materials include materials and solvents with high dielectric loss factors containing -OH, -NH, C=O, -N=O functional groups. Other examples of suitable coating polymer materials include polyacrylonitrile (tan δ=.1 at 60 Hz), polyethylene glycol, or mixtures thereof. In some examples, the coating polymer material is particularly responsive to electromagnetic energy in a specific frequency range, such as microwave energy in the GHz range.

[0026] Table 1 compares the coating polymer material of polyvinyl alcohol and the base polymer material of Ultem TM Dielectric loss factor, melting point and solubility parameters of a specific example of 1010 (polyetherimide):

[0027] Table 1

[0028]

[0029] In this example, Ultem TM 1010 (polyetherimide) as the base polymer material and using polyvinyl alcohol as the coating polymer material is advantageous because polyvinyl alcohol has a relatively TM The high dielectric loss factor of 1010 (tan δ = 0.001 in the MHz-GHz frequency range), the 14 degree Celsius difference in the melting points of the two materials, and the close solubility parameters indicate compatibility.

[0030] In addition to chemical properties, the base polymer layer 26 and the coating polymer layer 28 may also have physical properties that indicate suitability for promoting fusion, bonding, and mixing. For example, the base polymer layer 26 may have a diameter in the range of about 0.01 to about 0.5 mm, or in the range of about 0.05 to about 0.4 mm, or in the range of about 0.1 to about 0.3 mm. The coating polymer layer 28 may have a thickness in the range of about 1 micron to about 50 microns, or in the range of about 5 microns to about 25 microns, or in the range of about 10 microns to about 20 microns.

[0031] Also described is the use of conventional powder particle-based additive manufacturing techniques to form an object. The object is formed by depositing a first build layer of uncoated powder particles on a substrate. Selected particles of the first build layer of uncoated powder particles are melted or sintered using a laser. Next, a second build layer of uncoated powder particles is deposited on top of the first build layer and selectively melted or sintered. In the embodiment shown, a third build layer of uncoated powder particles is deposited on top of the first and second build layers and selectively melted or sintered. Due to the properties of conventional uncoated powder particles, each build layer is at least partially consolidated before the subsequent build layer is deposited, resulting in voids between adjacent particles in the uncoated powder particles. These voids weaken the object.

[0032] Figures 3 to 7 An example of a method of forming an object 90 using coated powder particles 6 according to the present invention is shown. Figure 3 As best shown in FIG. 1 , the method begins by depositing a first build layer 102 of coating powder particles 6 on a substrate 104. Each of the coating powder particles 6 includes a core formed by a base polymer layer 26 surrounded by a coating polymer layer 28. The coating powder particles 6 may be formed using Figure 1 The device 2 may be formed, or may be formed by different devices and / or methods. Figure 4 As shown, laser 106 is used to melt or sinter selected particles of coating powder particles 6 in first build layer 102 . Figure 5 1 shows selected particles 108 of the coating powder particles 6 of the first building layer 102 after melting or sintering. Figure 6 As shown, the method continues by depositing a second build layer 110 of coating powder particles 6 on top of the first build layer 102 and melting or sintering selected particles of the coating powder particles 6 to form an object 90 having three dimensions.

[0033] like Figure 6 As further shown, the method includes directing electromagnetic radiation 120 toward the object 90 to promote diffusion and bonding between adjacent particles in the coating powder particles 6. Because at least the coating polymer material responds to dielectric heating, it will melt to fill any gaps between adjacent particles in the coating powder particles 6. The electromagnetic radiation 120 is provided by a heating source 122, which is controlled to direct the electromagnetic radiation 120 to a selected area of ​​the object 90 or the entire object 90. The duration of applying the electromagnetic radiation 120 can also be controlled to strengthen one or more local areas of the object 90, or the entire object 90. In addition, in one example, the electromagnetic radiation 120 can be a microwave having a frequency in the range between 300 MHz and 300 GHz. In this example, the coating polymer material has a high dielectric loss factor and is susceptible to microwave radiation and, therefore, dielectric heating.

[0034] Because the coating polymer material has a higher dielectric loss factor and the base polymer material has a lower dielectric loss factor, the frequency of the electromagnetic radiation can be selected so that only the coating polymer layer 28 melts directly in response to the electromagnetic radiation. In addition, the base polymer material can have a melting point close to the melting point of the coating polymer material so that the base polymer layer 26 at least partially melts in response to the heating of the coating polymer layer 28. Thus, the coating polymer layer 28 will melt directly and the base polymer layer 26 will melt indirectly in response to the electromagnetic radiation 120. In other examples, the electromagnetic radiation 120 can directly heat both the coating polymer layer 28 and the base polymer layer 26. In either case, the melted portions of the base polymer layer 26 in adjacent particles can fuse together, thereby preventing the formation of voids between adjacent particles and promoting the structural integrity of the constructed object.

[0035] In examples where the coating polymer material and the base polymer material have compatible solubility parameters (see non-limiting examples in Table 1), melting of both the coating polymer layer 28 and the base polymer layer 26 produces a homogeneous mixture so that no phase separation occurs when the melted layers subsequently cool and harden.

[0036] Figure 7 The final object 90 is shown wherein all unmelted or unsintered particles of the coating powder particles 6 are removed from the substrate 104. The resulting object 90 has no voids between particles or build layers.

[0037] In addition, the present disclosure includes implementations or embodiments according to the following clauses:

[0038] 1. A coated powder particle 6 for use in an additive manufacturing process, the coated powder particle 6 comprising:

[0039] a base polymer layer 26 formed of a base polymer material having a first dielectric loss factor; and

[0040] A coating polymer layer 28 surrounds the base polymer layer 26 and is formed of a coating polymer material having a second dielectric loss factor, wherein the second dielectric loss factor of the coating polymer material is greater than the first dielectric loss factor of the base polymer material.

[0041] 2. The coated powder particle 6 of clause 1, wherein the base polymer material has a first melting point, the coating polymer material has a second melting point, and the difference between the first melting point and the second melting point is within about 20 degrees Celsius.

[0042] 3. The coated powder particle 6 of clause 2, wherein the base polymer material has a first solubility parameter, the coating polymer material has a second solubility parameter, and the difference between the second solubility parameter and the first solubility parameter is about 10 J / cc 0.5 Inside.

[0043] 4. The coated powder particle 6 of clause 1, wherein the base polymer material has a first solubility parameter, the coating polymer material has a second solubility parameter, and the difference between the second solubility parameter and the first solubility parameter is about 10 J / cc 0.5 Inside.

[0044] 5. The coated powder particle 6 of any one of clauses 1 to 4, wherein the base polymer material comprises polyetherimide and the coating polymer material comprises polyvinyl alcohol.

[0045] 6. The coated powder particle 6 of any of clauses 1 to 5, wherein the base polymer layer 26 has a diameter of about 0.1 to about 5 millimeters, and the coating polymer layer 28 has a thickness of about 1 to about 1,000 microns.

[0046] 7. A method of manufacturing coated powder particles 6 for use in an additive manufacturing process, the method comprising:

[0047] advancing a plurality of powder particles 4 through a chamber 8, each of the plurality of powder particles 4 being formed of a base polymer material;

[0048] applying a liquid coating 24 formed of a coating polymer material to the exterior of each of the plurality of powder particles 4; and

[0049] drying the liquid coating 24 on the plurality of powder particles 4 to form a plurality of coated powder particles 6;

[0050] Each of the plurality of coating powder particles 6 includes a base polymer layer 26 formed by the powder particles 4 and a coating polymer layer 28 formed by the dried liquid coating 24 .

[0051] 8. The method of clause 7, wherein advancing the plurality of powder particles 4 through the chamber 8 comprises providing the chamber 8 with perforations 14 and directing pressurized air through the perforations 14 to form an airflow 22 through the chamber 8.

[0052] 9 . The method of clause 8 , wherein applying the liquid coating 24 to the exterior of each of the plurality of powder particles 4 comprises spraying the liquid coating 24 from a nozzle 18 disposed in the chamber 8 .

[0053] 10. The method of any one of clauses 7 to 9, wherein:

[0054] The base polymer material has a first dielectric loss factor;

[0055] The coated polymer material has a second dielectric loss factor; and

[0056] The second dielectric loss factor of the coating polymer material is greater than the first dielectric loss factor of the base polymer material.

[0057] 11. The method of any one of clauses 7 to 10, wherein:

[0058] The base polymer material has a first melting point;

[0059] The coating polymer material has a second melting point; and

[0060] The difference between the first melting point and the second melting point is within about 20 degrees Celsius.

[0061] 12. The method of any one of clauses 7 to 11, wherein:

[0062] The base polymer material has a first solubility parameter;

[0063] The coating polymer material has a second solubility parameter; and

[0064] The difference between the second solubility parameter and the first solubility parameter is about 10 J / cc 0.5 Inside.

[0065] 13. The method of any one of clauses 7 to 12, wherein the base polymer material comprises polyetherimide and the coating polymer material comprises polyvinyl alcohol.

[0066] 14. The method of any of clauses 7 to 13, wherein the base polymer layer 26 has a diameter of about 0.1 to about 5 millimeters and the coating polymer layer 28 has a thickness of about 1 to about 1,000 microns.

[0067] 15. A method of manufacturing an object 90 by fusion powder manufacturing, the method comprising:

[0068] The coated powder particles 6 are formed by the following steps:

[0069] advancing a plurality of powder particles 4 through a chamber 8, each of the plurality of powder particles 4 being formed of a base polymer material;

[0070] applying a liquid coating 24 formed of a coating polymer material to the exterior of each of the plurality of powder particles 4; and

[0071] drying the liquid coating 24 on the plurality of powder particles 4 to form a plurality of coated powder particles 6;

[0072] Each of the plurality of coating powder particles 6 includes a base polymer layer 26 formed by the powder particles 4 and a coating polymer layer 28 formed by the dried liquid coating 24;

[0073] depositing the coating powder particles 6 into a first building layer 102 on a substrate 104;

[0074] heating selected portions of the first build-up layer 102;

[0075] Depositing the coating powder particles 6 on the substrate 104 into a second building layer 110 above the first building layer 102;

[0076] heating selected portions of the second build-up layer 110; and

[0077] At least the coating polymer layer of the coating powder particles 6 in the selected portions of the first build layer 102 and the second build layer 110 is dielectrically heated using electromagnetic radiation 120 to fuse adjacent ones of the coating powder particles 6 across an interface region.

[0078] 16. The method of clause 15, wherein:

[0079] The base polymer material has a first dielectric loss factor;

[0080] The coated polymer material has a second dielectric loss factor; and

[0081] The second dielectric loss factor of the coating polymer material is greater than the first dielectric loss factor of the base polymer material.

[0082] 17. The method of clause 15 or 16, wherein:

[0083] The base polymer material has a first melting point;

[0084] The coating polymer material has a second melting point; and

[0085] The difference between the first melting point and the second melting point is within about 20 degrees Celsius.

[0086] 18. The method of any one of clauses 15 to 17, wherein:

[0087] The base polymer material has a first solubility parameter;

[0088] The coating polymer material has a second solubility parameter; and

[0089] The difference between the second solubility parameter and the first solubility parameter is about 10 J / cc 0.5 Inside.

[0090] 19. The method of any of clauses 15 to 18, wherein the base polymer material comprises polyetherimide and the coating polymer material comprises polyvinyl alcohol.

[0091] 20. The method of any of clauses 15 to 19, wherein dielectrically heating at least the coated polymer layer of the coated powder particles in the selected portions of the first and second build layers comprises applying the electromagnetic radiation 120 in a microwave frequency range.

[0092] It should be understood that the drawings are not necessarily drawn to scale and that the disclosed examples are sometimes shown schematically. It should also be understood that the following detailed description is merely exemplary in nature and is not intended to limit the application and use of the present disclosure. Therefore, although the present disclosure is depicted and described as certain illustrative examples for ease of explanation, it will be understood that it can be implemented in various other types of examples and in various other systems and environments.

Claims

1. A coated powder particle (6) for use in an additive manufacturing process, the coated powder particle (6) comprising: a base polymer layer (26), the base polymer layer being formed of a base polymer material having a first dielectric loss factor; as well as a coating polymer layer (28) surrounding the base polymer layer (26) and formed of a coating polymer material having a second dielectric loss factor, wherein the second dielectric loss factor of the coating polymer material is greater than the first dielectric loss factor of the base polymer material, Wherein, the base polymer material comprises polyetherimide, and the coating polymer material comprises polyvinyl alcohol.

2. The coated powder particle (6) according to claim 1, wherein: The base polymer material has a first melting point, the coating polymer material has a second melting point, and the difference between the first melting point and the second melting point is within 20 degrees Celsius.

3. The coated powder particle (6) according to claim 1 or 2, wherein: The base polymer material has a first solubility parameter, the coating polymer material has a second solubility parameter, and the difference between the second solubility parameter and the first solubility parameter is within 10 J / cc 0.5 Inside.

4. A method of producing coated powder particles (6) for use in an additive manufacturing process, the method comprising: advancing a plurality of powder particles (4) through a chamber (8), each of the plurality of powder particles (4) being formed of a base polymer material having a first dielectric loss factor; applying a liquid coating (24) to the exterior of each of the plurality of powder particles (4), the liquid coating (24) being formed of a coating polymer material having a second dielectric loss factor, wherein the second dielectric loss factor of the coating polymer material is greater than the first dielectric loss factor of the base polymer material; and Drying the liquid coating (24) on the plurality of powder particles (4) to form a plurality of coated powder particles (6); Each of the plurality of coating powder particles (6) comprises a base polymer layer (26) formed by the powder particles (4) and a coating polymer layer (28) formed by the dried liquid coating (24). Wherein, the base polymer material comprises polyetherimide, and the coating polymer material comprises polyvinyl alcohol.

5. The method according to claim 4, wherein: Advancing the plurality of powder particles (4) through the chamber (8) includes providing the chamber (8) with perforations (14) and directing pressurized air through the perforations (14) to form an airflow (22) through the chamber (8).

6. The method according to claim 4 or 5, wherein: Applying the liquid coating (24) to the exterior of each of the plurality of powder particles (4) includes spraying the liquid coating (24) from a nozzle (18) disposed in the chamber (8).

7. The method according to claim 4 or 5, wherein: The base polymer layer (26) has a diameter of 0.1 to 5 millimeters, and the coating polymer layer (28) has a thickness of 1 to 1,000 micrometers.

8. A method of manufacturing an object (90) by fusion powder manufacturing, the method comprising: Forming coated powder particles (6) by the method according to any one of claims 4 to 7; depositing the coating powder particles (6) into a first build layer (102) on a substrate (104); heating selected portions of the first build layer (102); Depositing the coating powder particles (6) on the substrate (104) into a second building layer (110) above the first building layer (102); heating selected portions of the second build layer (110); as well as At least the coating polymer layer of the coated powder particles (6) in the selected portions of the first build layer (102) and the second build layer (110) is dielectrically heated using electromagnetic radiation (120) to fuse adjacent ones of the coated powder particles (6) across an interface region.

9. The method according to claim 8, wherein: Dielectrically heating at least the coated polymer layer of the coated powder particles (6) in the selected portions of the first and second build layers comprises applying the electromagnetic radiation (120) in a microwave frequency range.

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