Patent Application
20210004507
The present invention relates to a powder material evaluation apparatus, a powder material evaluation method, and a powder material evaluation program.
In the above technical field, patent literature I discloses a technique for a granular composite, as an accumulation of constituent particles, with an enhanced density.
Patent literature I: Japanese PCT National Publication No. 2016-535169
In the technique described in the above literature, however, since only enhancement of the density of the granular composite constituting a composition is used as the evaluation criterion of the granular composite, it is impossible to accurately evaluate a powder material as the raw material of a three-dimensional laminated and shaped object.
The present invention provides a technique of solving the above-described problem.
One example aspect of the present invention provides an evaluation apparatus of a powder material as a raw material of a three-dimensional laminated and shaped object, comprising:
a calculator that calculates, using powder constitution data concerning particles constituting the powder material, a volume of a closed space formed by the plurality of particles in the powder material; and
an evaluator that evaluates the powder material by comparing the calculated volume of the dosed space with a predetermined threshold.
Another example aspect of the present invention provides an evaluation method of a powder material as a raw material of a three-dimensional laminated and shaped object, comprising:
calculating, using powder constitution data concerning particles constituting the powder material, a volume of a closed space formed by the plurality of particles in the powder material; and
evaluating the powder material by comparing the calculated volume of the closed space with a predetermined threshold.
Still other example aspect of the present invention provides an evaluation program, of a powder material as a raw mat serial of a three-dimensional laminated and shaped object, for causing, a computer to execute a method, comprising:
calculating, using powder constitution data concerning particles constituting the powder material, a volume of a closed space formed by the plurality of particles in the powder material; and
evaluating the powder material by comparing the calculated volume of the closed space with a predetermined threshold.
According to the present invention, it is possible to accurately evaluate a powder material as the raw material of a three-dimensional laminated and shaped object.
Example embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that the relative arrangement of the components, the numerical expressions and numerical values set forth in these example embodiments do not limit the scope of the present invention unless it is specifically stated otherwise.
A powder material evaluation apparatus according to this example embodiment Will be described with reference to
A powder material as an evaluation target of the powder material evaluation apparatus 100 according to this example embodiment is not particularly limited as long as the powder material is a material as the raw material of a three-dimensional laminated and shaped object. Examples of the powder material can be a metal powder material, a ceramic powder material, and a plastic powder material. Examples of the metal powder material can be iron, titanium, copper, stainless steel, maraging steel, aluminum, cobalt, chromium, cobalt-chrome, nickel alloy, and inconel. Examples of the ceramic powder material can be glass fiber and gypsum. Examples of the plastic powder material can be nylon, polyamide, ABS resin, PLA resin, an epoxy-based resin, and an acrylic resin. The powder material as an evaluation target of the powder material evaluation apparatus 100 according to this example embodiment may be a material obtained by mixing the above-described powder materials appropriately.
A three-dimensional laminated and shaped object is manufactured using a powder material as the raw material. A shaping method adopted by a three-dimensional laminating and shaping apparatus used to manufacture a three-dimensional laminated and shaped object is not particularly limited. Examples of the shaping method adopted by the three-dimensional laminating and shaping apparatus can be a laser sintering method, fused deposition modeling, an optical shaping method, a direct metal laser sintering method, a laser fusion method, an electron beam melting method, direct metal lamination, and laser engineered net shaping.
As shown in
Using powder constitution data concerning particles constituting the powder material, the calculator 101 calculates the volume of the closed spaced formed by the plurality of particles in the powder material. The calculator 101 acquires the powder constitution data concerning the particles constituting the powder material as the raw material of a three-dimensional laminated and shaped object. The powder constitution data includes at least the particle sizes (μm) of the particles constituting the powder material, the particle size distribution (volume percentage (%)) of the particles, and position data of the particles. The position data of the particles are displayed in, for example, coordinate axes of (x, y, z).
The calculator 101 calculates the volume of the closed space formed by the plurality of particles using the powder constitution data concerning the particles constituting the powder material. Note that in the powder material, the closed space indicates an isolated three-dimensional space formed by the plurality of particles constituting the powder material.
The calculator 101 calculates the volume of the closed space formed the plurality of particles constituting the powder material by executing a simulation. The simulation executed by the calculator 101 may be based on, for example, a method that reproduces a wall stress model using a discrete element method (to be referred to as “DEM” hereinafter) or the DEM and a signed distance function (to be referred to as “SDF” hereinafter) as a numerical simulation within an arbitrary wall surface shape.
The simulation executed by the calculator 101 may be based on DEM-CFD obtained by combining the DEM and computational fluid dynamics (to be referred to as “CFD” to hereinafter). Furthermore, in the simulation executed by the calculator 101, a friction coefficient obtained from the angle of repose (one of the physical property values of the powder particles) of the particles included in the powder material may be used for the discrete element method (DEM). The calculator 101 may also calculate the volume of the closed space formed by the plurality of particles constituting the powder material using, as the powder constitution data concerning the particles constituting the powder material, stereolithography data (STL data) obtained by X-ray CT. The calculator 101 sets an equal-interval orthogonal grid including the powder material. The calculator 101 evaluates the volume of the closed space using the number of grid points of the equal-interval orthogonal grid belonging to a cluster formed by the plurality of particles constituting the powder material.
The volume of the closed space calculated by the calculator 101 is output to the evaluator 102 to be compared with the predetermined threshold. The predetermined threshold indicates the volume of a closed space formed from the plurality of particles constituting the powder material. The evaluator 102 compares the volume of the closed space calculated by the calculator 101 with the predetermined threshold. The predetermined threshold is set in association with the quality of an already manufactured three-dimensional laminated and shaped object. The evaluator 102 obtains a comparison result by comparing the volume of the closed space calculated by the calculator 101 with the predetermined threshold. The evaluator 102 evaluates the powder material based on the comparison result.
As described above, the powder material evaluation apparatus 100 according to this example embodiment newly defines a closed space formed by the plurality of particles constituting the powder material, and calculates the volume of the closed space using the powder constitution data concerning the particles. Then, the powder material evaluation apparatus 100 according to this example embodiment can compare the calculated volume of the dosed space with the predetermined threshold, and evaluate the powder material as the raw material of the three-dimensional laminated and shaped object based on a comparison result.
A powder material evaluation apparatus 200 according to the second example embodiment of the present invention will be described next with reference to
The data acquirer 201 acquires powder constitution data concerning particles constituting a powder material. The data acquirer 201 outputs the powder constitution data to the calculator 202. The calculator 202 calculates the volume of a closed space formed by a plurality of particles constituting the powder material using the powder constitution data acquired from the data acquirer 201. The calculator 202 outputs the calculated volume of the closed space to the evaluator 203.
The threshold DB 204 stores a predetermined threshold. The predetermined threshold is based on each data of an already manufactured three-dimensional laminated and shaped object. The predetermined threshold stored in the threshold DB 204 is output to the evaluator 203. The calculator 202 compares the calculated volume of the closed space with the predetermined threshold output from the threshold DB 204. The calculator 202 outputs, as a comparison result, to the evaluator 203, a result of comparing the calculated volume of the closed space with the predetermined threshold output from the threshold DB 204. The evaluator 203 acquires the evaluation result of the powder material by determining the comparison result. The evaluator 203 outputs the evaluation result to the display unit 205. The display unit 205 displays the evaluation result of the powder material as an evaluation target.
The plurality of particles constituting the powder material have different shapes and particle sizes, and are randomly located in the powder material. The powder material has a predetermined particle size distribution (volume percentage (%)). Therefore, it is extremely difficult to calculate the volume of the closed space formed from the plurality of particles constituting the powder material. To cope with this, the powder material evaluation apparatus 200 according to this example embodiment includes the calculator 202 to readily calculate the volume of the closed space formed from the plurality of particles constituting the powder material.
In step S303, the calculator 202 assumes, as spheres, particles constituting the powder material and forming a closed space. The calculator 202 performs Delaunay division by setting the centers of the four spheres as base points (generatrices), thereby obtaining a tetrahedron.
In step S305, the calculator 202 calculates the volume of the tetrahedron. The calculator 202 calculates the volume of an overlapping portion of the tetrahedron and the spheres existing at the four vertices of the tetrahedron. The calculator 202 calculates, as the volume of the closed space, a volume obtained by subtracting the volume of the overlapping portion from the volume of the tetrahedron.
In step S307, the evaluator 203 compares the volume of the closed space calculated by the calculator 202 in step S305 with the predetermined threshold stored in the threshold DB 204. The predetermined threshold stored in the threshold DB 204 is set in association with the quality of an already manufactured three-dimensional laminated and shaped object under a given condition.
The evaluator 203 outputs a comparison result by comparing the volume of the closed space calculated by the calculator 202 with the predetermined threshold stored in the threshold DB 204.
The predetermined threshold stored in the threshold DB 204 may be set to include a plurality of thresholds. If the predetermined threshold is set to include the plurality of thresholds, the plurality of thresholds are set in association with the qualities of a plurality of already manufactured three-dimensional laminated and shaped objects.
A method executed by the evaluator 203 to acquire a comparison result is not particularly limited. A ratio or difference between the volume of the closed space calculated by the calculator 202 and the predetermined threshold stored in the threshold DB 204 may be obtained to acquire a comparison result.
In step S309, the evaluator 203 evaluates the powder material by determining the comparison result. The evaluator 203 has an evaluation criterion to determine the comparison result obtained in step S307. The evaluator 203 determines the comparison result by collating the comparison result with the evaluation criterion. Based on the comparison result, the evaluator 203 estimates the quality of a three-dimensional laminated and shaped object to be manufactured from the powder material as an evaluation target, thereby evaluating the powder material.
As described above, in the processing procedure of the powder material evaluation apparatus 200, the volume of the closed space formed from the plurality of particles is calculated based on the powder constitution data, and is compared with the predetermined threshold, thereby evaluating the powder material.
As shown in
In each of the powder materials (represented by powders 1 to 5), closed spaces with predetermined volumes each formed from a plurality of particles are distributed at a predetermined volume ratio (volume percentage) with respect to the whole volume (total amount) of the closed space formed from the particles constituting the powder material. In each of the powder materials (represented by powders 1 to 5), the ratio (%) of the volume of each closed space formed from the plurality of particles constituting the powder material to the whole volume (total amount) of the dosed space formed from the particles constituting the powder material is as follows. The ratio is 0.17 for powder 1, 0.27 for powder 2, 0.18 for powder 3, 1.23 for powder 4, or 0.91 for powder 5.
A powder material with the powder material ID 801 of 0001 is constituted, from panicles of a metal titanium powder material. The average particle size of the particles of the powder material is 40 μm. The dosed space void diameter formed by the plurality of particles constituting the powder material is 35 μm. The ratio of the volume of the closed space formed from the plurality of particles constituting the powder material to the whole volume (total amount) of the space formed from the particles constituting the powder material is 0.10 (%).
The ratio of the volume of a void existing in a three-dimensional laminated and shaped object manufactured using the above powder material to the whole volume of the three-dimensional laminated and shaped object is 0.05 (%). The quality of the three-dimensional laminated and shaped object is high.
As described above, the predetermined threshold stored in the threshold DE 204 is set in association with the quality of the already manufactured three-dimensional laminated and shaped object under a given condition. The evaluator 203 acquires a comparison result by comparing the volume of the closed space calculated by the calculator 202 with the predetermined threshold. Furthermore, the evaluator 203 evaluates the powder material by determining the comparison result.
The powder material evaluation apparatus according to this example embodiment evaluates the powder material by determining the comparison result acquired by comparing the volume of the closed space calculated by the calculator 202 with the predetermined threshold. As described above, the technical feature of the powder material evaluation apparatus according to this example embodiment is that the volume of the closed space is calculated by newly defining a closed space formed by particles of the powder material.
A method of forming a closed space by a plurality of particles constituting a powder material and the influence of the existence of the dosed space on a three-dimensional laminated and shaped object will be described below.
In the powder material, closed spaces exist independent of each other, and are formed when a plurality of particles 901 constituting the powder material contact each other.
As shown in
A gas existing in the system of the powder material 900 is trapped in each of these closed spaces. The gas trapped in each closed space is emitted outside the closed space only by a buoyant force (three-dimensional force). Thus, it takes time for the gas trapped in each dosed space to be emitted within the system of the powder material 900. As a result, the gas trapped in each closed space is hardly emitted outside the system of the powder material 900.
The gas trapped in each closed space is held intact in the system of the powder material 900 without being emitted outside the system of the powder material 900 in manufacturing steps of a three-dimensional laminated and shaped object. After completion of all the manufacturing steps of the three-dimensional laminated and shaped object, the gas trapped in each closed space remains intact in the three-dimensional laminated and shaped object.
Finally, a void in which the gas trapped in each closed space exists is formed in the three-dimensional laminated and shaped object. In each void existing in the three-dimensional laminated and shaped object, there is no raw material of the three-dimensional laminated and shaped object. Therefore, each void existing in the three-dimensional laminated and shaped object degrades the physical properties of the manufactured three-dimensional laminated and shaped object, resulting in a decrease in quality of the three-dimensional laminated and shaped object.
On the other hand, in the powder material 900, there also exists a space (to be referred to as an “open space” hereinafter) formed by the plurality of particles 901 and communicating with the outside of the system of the powder material 900. In the powder material 900, a surface tension acting on a fluid formed when particles with particles sins of about 100 μm of the powder material dissolve is 1,000 times or larger than the gravity acting on the fluid. Thus, a gas existing in the open space is readily emitted outside the system of the powder material 900 by a one-dimensional force. Finally, in the powder material 900, the gas existing in the open space does not remain in the powder material 900. As described above, the open space formed by the plurality of particles 901 constituting the powder material 900 does not become a void existing in the manufactured three-dimensional laminated and shaped object. That is, the open space formed by the plurality of particles 901 constituting the powder material does not influence degradation in quality of the three-dimensional laminated and shaped object.
The volume of the open space and the volume of each closed space formed by the plurality of particles 901 constituting the powder material have a predetermined relationship. In the powder material 900, the volume of the open space formed by the plurality of particles 901 is obtained by subtracting the volumes of the closed spaces from the volume of the entire space formed by the plurality of particles 901.
The powder material is constituted from a plurality of powder material particles 1001. For example, in an upper left portion in the state 1000a, particles 1011 and 1012 of the powder material are located from above to below. The particles 1011 and 1012 contact each other via particles 1013 and 1014. These four particles form a closed space 1015. The powder material includes a plurality of closed spaces such as the closed space 1015 and a closed space 1016 each formed from the plurality of particles.
Next, if the powder material in die state 1000a is irradiated with a laser beam or the like by the three-dimensional laminating and shaping apparatus, the particles constituting the powder material dissolve, thereby shifting to the state 1000b. The state 1000b includes a plurality of closed spaces such as a closed space 1025 formed from particles 1021, 1022, 1023, and 1024.
If the powder material in the state 1000b is irradiated with a laser beam or the like by the three-dimensional laminating and shaping apparatus, the particles constituting the powder material dissolve, thereby shifting to the state 1000c. The powder material in the state 1000c includes closed spaces 1031, 1032, 1033, 1034, and 1035.
Finally, if the powder material in the state 1000c is irradiated with a laser beam or the like by the three-dimensional laminating and shaping apparatus, the particles of the powder material dissolve, thereby shifting to the state 1000d, in the state 1000d, the powder material is cooled and solidified, thereby obtaining a three-dimensional laminated and shaped object as a final product.
There exist closed spaces 1041, 1042, 1043, 1044, and 1045 in the manufactured three-dimensional laminated and shaped object. In each of these closed spaces, a gas that cannot be emitted outside the system of the powder material remains intact. As a result, voids exist in the manufactured three-dimensional laminated and shaped object. The quality of the manufactured three-dimensional laminated and shaped object is not high.
As described above, the powder material evaluation apparatus according to this example embodiment newly defines a closed space formed from the plurality of particles constituting the powder material in the powder material, and calculates the volume of the closed space. Furthermore, the powder material evaluation apparatus according to this example embodiment acquires a comparison result by comparing the volume of the closed space with the predetermined threshold, and determines the comparison result, thereby evaluating the powder material.
The powder material evaluation apparatus 200 according to this example embodiment includes the display unit 205 for displaying the evaluation result of the powder material.
A powder material evaluation apparatus according to the third example embodiment will be described next with reference to
As shown in
Particles constituting a powder material as the raw material of a three-dimensional laminated and shaped object have different particle sizes, and are randomly located in the powder material. It is, therefore, extremely difficult to determine whether a space formed by the particles constituting the powder material is a closed space in the powder material. To cope with this, the powder material evaluation apparatus 1200 according to this example embodiment includes the closed space determiner 1201 to determine whether a space formed from the plurality of particles constituting the powder material is a closed space.
Similar to the above-described example embodiment, the closed space determiner 1201 assumes, as spheres, the particles constituting the powder material, and performs Delaunay division by setting the centers of the spheres as base points, thereby obtaining a tetrahedron 1300. The closed space determiner 1201 considers an inscribed sphere 1301 inscribed in the tetrahedron 1300. Furthermore, the closed space determiner 1201 calculates the volume of a space formed by the plurality of particles constituting the powder material, and considers a virtual sphere 1302 whose volume is equal to that of the space.
Next, the closed space determiner 1201 places, at a barycenter 1303 of the tetrahedron 1300, the center of the inscribed sphere 1301 inscribed in the tetrahedron 1300 and the center of the virtual sphere 1302 whose volume is equal to that of the space formed by the plurality of particles constituting the powder material.
In addition, the closed space determiner 1201 compares the size of the inscribed sphere 1301 with that of the virtual sphere 1302. The closed space determiner 1201 determines whether the virtual sphere 1302 whose volume is equal to that of the space formed by the plurality of particles is smaller than the inscribed sphere 1301 inscribed in the tetrahedron 1300. Comparison between the size of the virtual sphere 1302 and that of the inscribed sphere 1301 is implemented by comparing a radius 1321 of the virtual sphere 1302 with a radius 1311 of the inscribed sphere 1301.
If the virtual sphere 1302 whose volume is equal to that of the space formed by the plurality of particles is smaller than the inscribed sphere 1301 inscribed in the tetrahedron 1300, the closed space determiner 1201 determines the space as a closed space. On the other hand, if the virtual sphere 1302 whose volume is equal to that of the space formed by the plurality of particles is larger than the inscribed sphere 1301 inscribed in the tetrahedron 1300, the closed space determiner 1201 determines the space as an open space. If the closed space determiner 1201 determines that the space formed by the plurality of particles is a closed space, it outputs a determination result of “presence of closed space” to the calculator 202. Based on the determination result of “presence of closed space”, the calculator 202 determines that the space formed from the plurality of particles constituting the powder material is a closed space, and calculates the volume of the closed space, similar to the above-described example embodiment. The evaluator 203 evaluates the powder material, similar to the above-described example embodiment.
As described above, the closed space determiner 1201 sets an inscribed sphere inscribed in a tetrahedron obtained by assuming, as spheres, particles constituting a powder material and performing Delaunay division using the centers of the spheres as base points. Then, the closed space determiner 1201 determines whether the space is a closed space by comparing the volume of the inscribed sphere with that of a virtual sphere whose volume is equal to that of the space formed from the particles constituting the powder material. That is, the powder material evaluation apparatus according to this example embodiment further includes the closed space determiner capable of determining whether the space formed from the particles contained in the powder material is a closed space, thereby making it possible to evaluate the powder material accurately and quickly.
While the invention has been particularly shown and described with reference to example embodiments thereof, the invention is not limited to these example embodiments. It will be understood by those of ordinary skill in the an that various chances in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims. A system or apparatus including any combination of the individual features included in the respective example embodiments may be incorporated in the scope of the present invention.
The present invention is applicable to a system including a plurality of devices or a single apparatus. The present invention is also applicable even when an information processing program for implementing the functions of example embodiments is supplied to the system or apparatus directly or from a remote site. Hence, the present invention also incorporates the program installed in a computer to implement the functions or the present invention by the computer, a medium storing the program, and a WWW (World Wide Web) server that causes a user to download the program. Especially, the present invention incorporates at least a non-transitory computer readable medium storing a program that causes a computer to execute processing steps included in the above-described example embodiments.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/009108 | 3/8/2018 | WO | 00 |
