Fabricated object having a fine non-planar structure in material extrusion additive manufacturing and method for manufacturing the same

Abstract

This technology improves interlayer fragility in extruded additive manufacturing products without requiring major changes to the entire toolpath or specialized hardware. [Solution] In material extrusion additive manufacturing, the process involves temporarily raising the Z coordinate of the nozzle by 30% to 100% of the layering pitch on the upper surface of the layer formed in the normal layering process to discretely form multiple protrusions, and then covering them with the next planar layer. This process is repeated. The additional material supplied by the protrusion formation locally fills interlayer voids and forms densified regions, and the interlayer bending strength is improved by approximately 58% due to the combined effect of bulk recovery and crack propagation suppression.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a shaped object formed by Material Extrusion Additive Manufacturing (hereinafter referred to as "MEX"), and a shaped object obtained by the manufacturing method. More specifically, in MEX, fine protrusions are discretely formed at the interface of adjacent layers and coated with the next layer to improve the bending strength between layers, and to a shaped object in which a local densification region is formed at the layer interface by the method.

Background Art

[0002] MEX is an additive manufacturing method that forms a three-dimensional shaped object by heating and melting a filament of a thermoplastic material and depositing it layer by layer while extruding it from a nozzle. Due to the wide range of material selection, low equipment cost, and high design freedom, MEX is not only used for prototyping, but its application is also expanding to the manufacture of final products including load-bearing components such as prosthetics and orthotics (see Non-Patent Document 1 and Non-Patent Document 2).

[0003] However, there is mechanical anisotropy in MEX shaped objects, where the strength in the stacking direction (hereinafter referred to as the "Z direction") is significantly lower than the strength in the in-plane direction. This interlayer vulnerability is a fundamental bottleneck in the safety and reliability of load-bearing components.

[0004] Conventionally, the interlayer strength of MEX shaped objects has mainly been explained by the mutual diffusion of polymer molecular chains and the degree of entanglement formation (crack healing theory) (see Non-Patent Document 3). Based on this theoretical framework, material chemistry techniques such as optimization of nozzle temperature and control of ambient temperature (see Non-Patent Document 1), and material design of filaments (for example, an approach to adjust the fluidity of the sheath component of a core-shell structure filament (see Non-Patent Document 4)) have been pursued.

[0005] On the other hand, recent research has reported that the dominant factor in the mechanical anisotropy of MEX fabricated objects is not the incomplete diffusion of polymer molecular chains as previously thought, but rather microscopic geometric defects resulting from the cross-sectional shape of the linear material (hereinafter referred to as "bead") deposited when the filament is extruded from the nozzle's extrusion hole, namely voids and grooves formed between layers (see Non-Patent Documents 5 and 6). Specifically, after extrusion, the bead exhibits a roughly elliptical cross-section, and continuous triangular voids are inevitably formed between adjacent beads and between upper and lower layers (see Figure 1). These voids reduce the effective cross-sectional area for load transfer and, because the voids are continuous in the in-plane direction, function as a preferential crack propagation path, significantly reducing the apparent interlayer strength.

[0006] Based on this understanding of geometric defects, several approaches have been proposed to "restore bulk properties by changing the geometry of the process." For example, there is an approach to uniformly eliminate voids between beads by increasing the extrusion width (see Non-Patent Document 7), an approach to eliminate voids by changing the entire toolpath to a continuous Z-direction zigzag (non-planar path) (see Non-Patent Document 8), a two-stage Z-pinning approach in which voids across multiple layers are intentionally aligned before being filled with a pin-structured material (see Non-Patent Document 9), and void elimination by stitch patterns (see Non-Patent Document 10).

[0007] However, each of the above conventional technologies has the following problems. Firstly, the approaches described in Non-Patent Documents 7, 8, and 10 all require extensive modifications to the entire toolpath. As a result, they essentially cannot utilize the output of existing slicer software, limiting their application to thin-walled sections and complex curved surfaces. Secondly, the Z-pinning approach described in Non-Patent Document 9 requires a two-step process in which voids are pre-aligned and formed across multiple layers before being filled with material. Therefore, the process is complex and difficult to apply locally. Thirdly, it has been reported that the approach of uniformly increasing the amount of material to eliminate voids has a trade-off in that when the extrusion ratio exceeds a predetermined threshold, the excess material becomes a new source of stress concentration, which actually degrades the mechanical properties (see Non-Patent Literature 11). [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Gao, X. et al., "Fused filament fabrication of polymer materials: A review of interlayer bond," Additive Manufacturing, Vol.37, Art. no. 101658 (2021), DOI:10.1016 / j.addma.2020.101658 [Non-Patent Document 2] Atallah, H. et al., "The current state of 3D-printed prostheses clinical outcomes: A systematic review," Journal of Functional Biomaterials, Vol.16, No.10, Art. no. 370 (2025), DOI:10.3390 / jfb16100370 [Non-Patent Document 3] Wool, RP and O'Connor, KM, "A theory of crack healing in polymers," Journal of Applied Physics, Vol.52, No.10 (1981), pp.5953-5963, DOI:10.1063 / 1.328526 [Non-Patent Document 4] Orimo, A., "Improvement of layer adhesion in MEX printout by filament design," Conference on 4D and Functional Fabrication 2022 (2022), p.OP-21

Direct Environment 5

Outdoor Configuration 6

Direct Environment 7

Outdoor Tools 8

Outdoor Tools9

Outdoor Tools 10

Outdoor Content11

[0009] As described above, the main cause of interlayer fragility in MEX fabricated objects is the presence of interlayer voids resulting from the cross-sectional shape of the bead, and the formation of crack propagation paths due to the continuity of these voids in the in-plane direction. Existing solutions all have challenges, such as large-scale changes to the entire toolpath, complex two-stage processes, or trade-offs associated with uniformly increasing the amount of material.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a manufacturing method that improves interlayer bending strength by disrupting the in-plane continuity of interlayer voids with minimal local intervention while basically maintaining the existing planar layer structure, and a manufactured product obtained by this method. [Means for solving the problem]

[0011] In order to solve the above problems, the material extrusion lamination modeling method of the present invention includes: (a) a normal lamination step of melting and extruding a filament of a thermoplastic material to form a planar layer on a modeling base or on the upper surface of a layer already deposited, at a predetermined lamination pitch; (b) on the upper surface of the layer formed in the normal lamination step, during or after the formation of the layer, extruding the material while temporarily raising the Z coordinate of the nozzle by 30% or more and 100% or less of the lamination pitch, and forming a plurality of protrusions discretely in the in-plane direction of the layer, having a height of 30% or more and 100% or less of the lamination pitch; (c) on the layer on which the protrusions are formed, forming the next planar layer at a position where the Z coordinate of the nozzle is raised by the same value as the Z coordinate increment in the normal lamination step before the protrusion formation step, and depositing the next layer so as to enclose the protrusions; and (d) repeating the steps (a) to (c) in the lamination direction of the modeled object. Each protrusion in the protrusion formation step (b) is arranged so as to locally break the in-plane continuity of continuous voids existing within the same interlayer interface.

[0012] Further, the modeled object of the present invention is a modeled object in which a plurality of planar layers made of a thermoplastic material are deposited in the lamination direction at a predetermined lamination pitch. At the interface of at least a pair of adjacent layers, a plurality of densification regions where the voids between beads are locally filled exist discretely in the in-plane direction of the interface. The distance between each of the densification regions and an adjacent densification region in the in-plane direction is 1 to 20 times the width of the beads used for forming the layer. In the non-densification region between the densification regions, the voids between the beads continuously exist in the in-plane direction. Due to the existence of the densification regions, the in-plane continuity of the voids is locally interrupted.

Advantages of the Invention

[0013] According to the present invention, the following effects can be obtained.

[0014] First, the additional material supplied in the protrusion formation step locally fills the interlayer voids, increasing the effective load transfer cross-sectional area and partially restoring the mechanical properties of the region to those of the bulk material (hereinafter referred to as the "bulk recovery effect"). In the examples described below, the estimated filling rate calculated using the technical data sheet density of 1.17 g / cm3 (conforming to ISO 1183) of the material used as the theoretical density was approximately 88% for the shaped object manufactured by the method of the present invention (hereinafter referred to as the "Z pattern") and approximately 80% for the shaped object without protrusions (hereinafter referred to as the "S pattern").

[0015] Second, by discretely interrupting the continuity of the in-plane continuous voids in the densification region, the preferential propagation path of cracks is blocked (hereinafter referred to as the "crack propagation suppression effect"). Since the ratio of the flexural strength of the Z pattern to that of the S pattern remains approximately 1.43 (a 43% difference) (p < 0.001) even after normalization by apparent density, it is confirmed that the increase in the amount of material alone cannot explain all of the strength improvement, and the mechanical effect due to the interruption of void continuity contributes independently. That is, in normal lamination, continuous voids function as notches and cracks propagate along the voids with low energy, whereas in the present invention, the densification region discretely interrupts the continuity of these notches, so that cracks need to bypass or penetrate the bulk fusion region, increasing the energy absorption until failure.

[0016] Third, the method of the present invention can be implemented by simply adding local Z coordinate change commands and extrusion amount commands in the control program of the shaping device represented by G code while basically maintaining the normal planar lamination process. Therefore, it can be directly implemented on a general-purpose MEX method additive manufacturing device without requiring special nozzles, hardware modification, or redesign of the entire tool path.

[0017] Fourth, since the material supply is discrete and selective, the generation of stress concentration sources caused by excess materials reported in the approach of uniformly increasing the amount of material (see Non-Patent Document 11) is avoided.

[0018] Fifth, because the protrusions can be selectively placed at any interlayer interface within the fabricated object, it is possible to apply them locally only to areas where strength is required. [Brief explanation of the drawing]

[0019] [Figure 1] A schematic perspective view showing a conventional bead structure in material extrusion additive manufacturing. [Figure 2] Figure 1 is a perspective view including a horizontal cross-section along line AA, showing the in-plane continuity of the grooves and the distribution of voids between layers. [Figure 3] Figure 1 is a perspective view including a longitudinal section along the BB line, showing the in-plane continuity of the groove and the distribution of voids between layers. [Figure 4] This is a schematic perspective view showing the bead structure and protrusions of the molded object according to the present invention, and is shown in the state before the coating process to clearly show the arrangement of the protrusions. [Figure 5] Figure 4 is a perspective view including a horizontal cross-section along line AA, showing the disruption of the in-plane continuity of the grooves due to the densification region and the local filling of voids between layers. [Figure 6] Figure 4 is a perspective view including a longitudinal section along the BB line, showing the disruption of the in-plane continuity of the groove due to the densification region and the local filling of voids between layers. [Figure 7] A side view showing the nozzle movement path and design parameters in a projection formation process according to one embodiment of the present invention. [Figure 8] A side view showing the relationship between the protrusion formation path and the covering path in an alternating symmetrical pattern arrangement of protrusions according to one embodiment of the present invention. [Figure 9] The load-displacement curves from the three-point bending test in the example show representative test results for the Z pattern (with protrusions) and the S pattern (without protrusions). [Figure 10] This is a micrograph of the fracture surface observed from the side after a bending test of the Z-pattern (with protrusions) in the example, showing a step structure where the fracture surface transitions to the adjacent interlaminar interface. [Modes for carrying out the invention]

[0020] The embodiments of the present invention will be described in detail below with reference to the drawings. Note that the following embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these embodiments.

[0021] In this specification, the following terms are used with the meanings set forth below. "Layer pitch" refers to the vertical distance between the top surfaces of adjacent layers in the stacking direction. It is synonymous with "layer height" in slicer software. A "bead" is a linear body formed when a thermoplastic filament is melt-extruded from the nozzle's extrusion hole and deposited on the build plate or on top of an existing layer. The cross-sectional shape of the bead depends on the extrusion and layering conditions, but it is typically approximately elliptical. "Bead width in the in-plane direction" refers to the maximum in-plane dimension of a single bead in a non-densified region sufficiently far from the densified region, when observing a cross-section of the fabricated object along the layering direction (hereinafter referred to as the "layered cross-section"). A "protrusion" refers to a localized raised area that protrudes upward from the top surface of a layer during or immediately after the fabrication of that layer by extruding the material while temporarily raising the Z-coordinate of the nozzle by less than or equal to the layer thickness. Protrusions may be deformed or remelted from their original shape due to the heat and pressure during the layering of the upper layer in the coating process. A "densification region" refers to a region that has a higher filling rate than the surrounding area as a result of additional material supplied during the protrusion formation process locally filling voids between beads. A densification region is defined as a region where voids are filled by the supply of additional material, regardless of whether the protrusions retain their shape after the coating process. "In-plane direction" refers to the direction perpendicular to the stacking direction, that is, the direction along the main surface of each layer. A "void" in MEX fabrication refers to an air gap formed between adjacent beads or between adjacent layers. "Bulk recovery" refers to the process where the voids are locally filled by the supply of additional material, causing the mechanical properties of that region to approach those of bulk material (a homogeneous molded product without voids). "Extrusion amount" refers to the command value for the filament extrusion amount in the control program of the 3D printer.

[0022] The manufacturing method of the present invention includes the following steps (a) to (d). (a) Normal layering process: A thermoplastic filament is heated and melted and extruded from a nozzle to form planar layers at a predetermined layer pitch on the build plate or on top of already deposited layers. The Z coordinate of the nozzle is raised by one layer pitch relative to the Z coordinate of the previous layer. This process is the same as normal MEX printing. (b) Protrusion formation process: On the upper surface of the layer formed in the normal lamination process, the material is extruded while temporarily raising the Z coordinate of the nozzle by 30% to 100% of the lamination pitch during or after the formation of the layer, thereby forming multiple discrete protrusions in the in-plane direction of the layer. The extrusion amount is calculated based on the law of conservation of volume by dividing the width of the nozzle discharge hole × the height of the protrusion × the distance traveled by the cross-sectional area of ​​the filament. The protrusion formation process (b) may be carried out in any of the following embodiments. In the first embodiment, the Z coordinate of the nozzle is temporarily raised to form protrusions during the continuous extrusion of the bead in the normal lamination process (a), and then the Z coordinate is lowered to the height of the normal lamination process (a) to continue normal lamination. That is, the normal lamination process (a) and the protrusion formation process (b) are executed as a single continuous nozzle movement path. In this embodiment, since the protrusions can be formed without interrupting the extrusion of the bead, thermal continuity between the protrusions and the surrounding bead is ensured, and the integrity within the layer is high. In the second embodiment, after a layer is formed by the usual lamination process (a), the nozzle is moved to a predetermined position on the upper surface of the layer to form a protrusion. In this embodiment, the position of the protrusion can be determined after the layer is formed, thus offering high design flexibility. In the embodiment described later, the first embodiment was adopted. (c) Coating process: A planar layer is formed on top of the layer on which the protrusions have been formed. At this time, the Z coordinate of the nozzle is set to a value obtained by adding one layer pitch to the Z coordinate set in the normal lamination process (a) immediately preceding the protrusion formation process (b). In other words, regardless of the presence of protrusions, the Z coordinate is set to the same height as in normal lamination. The extrusion amount (E value) and moving speed (F value) in the coating process are the same values ​​as in the normal lamination process (a). Since the additional material has already been supplied in the protrusion formation process (b), no adjustment of the extrusion amount is made in the coating process. (d) Repeating process: Steps (a) to (c) above are repeated a desired number of times in the layering direction of the molded object.

[0023] The molded object obtained by the above manufacturing method has the following structural characteristics. The structure consists of multiple planar layers made of thermoplastic material, deposited in the stacking direction at a predetermined stacking pitch. At the interface of at least one pair of adjacent layers, there are multiple discrete densification regions in the in-plane direction where voids between beads are locally filled. Voids between beads are continuously present in the in-plane direction in the non-densification regions between the densification regions, and the in-plane continuity of the voids is locally interrupted by the presence of the densification regions. The densification region includes cases where the protrusions formed during the protrusion formation process remain intact, where they are remelted and integrated due to the heat during lamination of the upper layer, and where they are plastically deformed due to the pressure and heat during lamination of the upper layer. In all cases, the structural characteristic common to all is that the additional material locally fills the voids between the beads and disrupts the continuity of the voids.

[0024] The above manufacturing method is implemented by the control program of the 3D printer. Specifically, it is based on the control program of a 3D printer for normal additive manufacturing generated by standard slicer software, and is realized by adding a Z-coordinate change command (G1 Z command) and an extrusion amount command (E value) corresponding to the protrusion formation process (b) at predetermined locations. The control program of the 3D printer for the coating process (c) is the same as the control program of the 3D printer for the normal additive manufacturing process (a), so no additional changes are required. [Examples]

[0025] The following describes a specific embodiment of the present invention. Polylactic acid (PLA) filament (PolyLite PLA, manufactured by Polymaker, with a diameter of 1.75 mm) was used as the material. A Creality Ender-3 Neo (MEX desktop 3D printer, with a nozzle diameter of 0.4 mm) was used as the 3D printer. The printing conditions were a nozzle temperature of 200°C, a bed temperature of 60°C, a layer thickness of 0.3 mm, a room temperature of 22 to 26°C, and a humidity of 40 to 60% RH.

[0026] The design parameters for the protrusions are as follows (see Figure 7). In the protrusion formation process, the horizontal movement distance was set to 1.00 mm when the nozzle's Z-coordinate was raised by 0.2 mm (corresponding to 67% of the layer pitch of 0.3 mm). As the nozzle descended, it partially compressed the preceding extruded material, resulting in an in-plane length of approximately 0.4 mm (approximately equivalent to the nozzle diameter) of the protrusion remaining on the upper surface of the layer. In-plane width of the projection: Approximately 0.4 mm (roughly equivalent to the nozzle diameter) Spacing of projections: The horizontal displacement distance between adjacent projections at normal height was set to 1.00 mm to 1.70 mm (see Figure 7). The protrusions were arranged in an alternating symmetrical pattern at each adjacent interlayer interface in the thickness direction (see Figure 8). The control specimen (S pattern) was generated by removing only the protrusion formation command from the control program structure of the same 3D printer.

[0027] A randomized block design was adopted, and one Z-pattern and one S-pattern were fabricated in each of the 30 blocks on the same day, resulting in a total of 60 test specimens. A three-point bending test (support span 64 mm, test speed 2 mm / min) was performed in accordance with JIS K 7171.

[0028] The results of the bending test are shown below. Bending strength of Z pattern: 44.80 ± 1.52 MPa (n=30) Bending strength of S pattern: 28.43 ± 1.08 MPa (n=30) Improvement rate: +57.6% (p<0.001, 95% confidence interval: 15.8 to 16.9 MPa) The modulus of elasticity was approximately 17% higher for the Z pattern than for the S pattern, and the maximum displacement (deformability) was approximately 39% higher (see Figure 9). This improvement in deformability is particularly important for the safety of load-bearing components. In conventional lamination, continuous voids function as notches, making it prone to brittle fracture due to rapid crack propagation after reaching the maximum load. In this invention, the disruption of void continuity by densification regions alleviates stress concentration, and the material absorbs energy through plastic deformation before fracture.

[0029] The apparent density of the Z pattern was 1.028 g / cm³, and the apparent density of the S pattern was 0.935 g / cm³. Even after normalizing the bending strength by apparent density, the strength ratio of the Z pattern to the S pattern remained at approximately 1.43 (p<0.001). A significant positive correlation between mass and bending strength was observed only within the Z pattern group (r=0.69, p<0.001).

[0030] In fracture surface observation of the Z-pattern, a phenomenon was observed where the fracture surface transitioned to an adjacent interlayer interface midway along the width direction (see Figure 10). The transition location corresponded to the design position of the protrusions in the control program of the 3D printer, and whitening was observed around the transition area. No systematic transition was observed in the fracture surface of the S-pattern.

[0031] Although PLA was used in the above examples, the present invention is not limited to PLA. The mechanism of the present invention is based not on the chemical properties of the material, but on the geometric properties inherent to the MEX fabrication process. Therefore, similar effects can be reasonably expected for ABS, PETG, polyamide, polycarbonate, and their fiber-reinforced composite materials. However, it is desirable to adjust the optimal protrusion parameters according to the properties of each material.

[0032] The protrusion height can be changed within a range of 30% to 100% of the lamination pitch, preferably between 50% and 80%. If the protrusion height is less than 30% of the lamination pitch, the amount of local void filling at the protrusion will be insufficient, making it difficult to effectively disrupt the continuity of voids in the in-plane direction. On the other hand, if the protrusion height exceeds 100% of the lamination pitch, interference between the nozzle and the protrusion will be significant in the subsequent coating process, potentially making it difficult to form a uniform coating layer. Similar effects can be expected in the range of lamination pitch from 0.1 to 0.5 mm and nozzle diameter from 0.2 to 1.0 mm. The arrangement pattern of the protrusions is not limited to alternating symmetry; repeating the same pattern, random arrangement, or localized concentrated arrangement are also included within the scope of the present invention. [Industrial applicability]

[0033] The present invention is applicable to any object formed by MEX, and is particularly suitable for the manufacture of load-bearing components such as prosthetics, orthotics, and industrial jigs that require strength in the layering direction. Since the present invention can be implemented by only localizing the control program of the 3D printer, it can be introduced without changing the existing MEX 3D printer infrastructure. [Explanation of symbols]

[0034] 10 Bead, 11 Void, 12 Groove, 13 Protrusion, 14 Densification region, 20 Protrusion formation path, 21 Covering path, 30 Z-pattern, 31 S-pattern, 40 Transition course of fracture surface

Claims

1. A material extrusion additive manufacturing method comprising (a) melting and extruding a filament of a thermoplastic material. Remove and place on the build plate or on the top surface of an already deposited layer at a predetermined layer pitch. (b) A normal lamination process to form a layer, and (b) on the layer formed by the normal lamination process On the surface, the Z coordinate of the nozzle is temporarily raised by 30% to 100% of the stacking pitch. The material is extruded while being processed, and protrusions having a height of 30% to 100% of the lamination pitch are formed. (c) A step of forming multiple protrusions discretely in the in-plane direction of the layer, and (c) the protrusions formed On top of the layer, the Z coordinate of the nozzle is the Z coordinate increment of the normal lamination process prior to the protrusion formation process. The next planar layer is formed at a position raised by the same value as the previous layer, and the next layer is the projection (d) A coating step in which the material is deposited so as to enclose the material The process includes a step that is repeated in the stacking direction, and each protrusion in the protrusion formation step (b) is the same This locally disrupts the in-plane continuity of continuous voids within the interlayer interface. A material extrusion additive manufacturing method characterized by the arrangement of materials.

2. The height of the protrusion is characterized by being 50% or more and 80% or less of the stacking pitch. The material extrusion additive manufacturing method described in 1.

3. In the aforementioned protrusion formation step (b), at a plurality of adjacent interlayer interfaces in the thickness direction of the fabricated object The projections are formed such that their arrangement in the in-plane direction forms an alternating symmetrical pattern. A material extrusion additive manufacturing method according to claim 1 or claim 2, characterized by the above.

4. The projection formation step (b) is the continuous extrusion of the bead in the normal lamination step (a). During the process, the material was extruded while temporarily increasing the Z-coordinate of the nozzle to form a protrusion. Then, the Z coordinate of the nozzle is lowered to the height of the normal lamination process (a) This is carried out by continuing step (a), and the normal lamination step (a) and the protrusion formation step (b) is characterized in that it is performed as a single continuous nozzle movement path. A material extrusion additive manufacturing method according to claim 1 or 2.

5. The projection formation step (b) and the coating step (c) are the same as the normal lamination step (a). The control program for the device describes the projection forming step (b) as the normal product The control program of the molding device for layering process (a) includes a Z-coordinate change command corresponding to the formation of protrusions. This is achieved by adding an extrusion amount command, as described in item 1 or by The material extrusion additive manufacturing method described in item 2.

6. In the aforementioned protrusion formation step (b), the amount of extrusion of each protrusion is determined based on the volume conservation law, and the nozzle It is calculated by dividing the product of the width of the ejection hole, the height of the protrusion, and the travel distance by the cross-sectional area of ​​the filament. The method described in claim 1 or 2, characterized in that it is set as the amount of material to be extruded. A material extrusion additive manufacturing method.

7. The aforementioned projection formation step (b) is performed after the layer has been formed by the conventional lamination step (a), This is done by moving the lubricant to a predetermined position on the upper surface of the layer to form a protrusion. A material extrusion additive manufacturing method according to claim 1 or 2, characterized by the features described above.

8. A fabricated object comprising a plurality of planar layers made of a thermoplastic material deposited in the stacking direction at a predetermined stacking pitch, wherein at least one pair of adjacent layers have a plurality of discrete densification regions where voids between beads are locally filled, located at the interface of the interface, wherein the distance between each of the densification regions and adjacent densification regions in the in-plane direction is between 1 and 20 times the in-plane width of a single bead constituting the layer, and voids between beads are continuously present in the in-plane direction in the non-densification regions between the densification regions, and the in-plane continuity of the voids is locally interrupted by the presence of the densification regions.

9. The molded product according to claim 8, characterized in that the thermoplastic material is at least one selected from the group consisting of polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate-glycol modified material, polyamide, polycarbonate, and fiber-reinforced composite materials thereof.

10. The molded object according to any one of claims 8 to 9, characterized in that the molded object is a prosthesis, orthosis, or a component thereof that supports the load of the human body.

Images