Method for manufacturing a three-dimensionally shaped object

Abstract

To provide a three-dimensional shape molded body capable of reducing the ratio of cutting cost occupied in the whole of production cost compared with the conventional one.SOLUTION: A method for producing a three-dimensional shape molded body comprises: a lamination molding step of producing a lamination molded body in which plural bond layers are laminated and integrated; and a processing step of removing excessive metal parts from the lamination molded body so as to be a three-dimensional shape molded body. In the lamination molding step, parts having relatively different strength are formed in at least a part of the bond layers to form a high strength part so as to be the three-dimensional molded body and a low strength part adjacent to the high strength part and having relatively low strength than the high strength part, and in the processing step, a part of the high strength part and the low strength part adjacent thereto are removed as excessive metal parts by processing.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for producing a three-dimensional shaped object from a raw material metal powder using a so-called 3D printer, and in particular to a method for producing a three-dimensional shaped object that facilitates cutting after modeling when producing a three-dimensional shaped object from a material that is difficult to cut, known as a difficult-to-cut material. [Background technology]

[0002] A three-dimensional shaped object is usually produced as follows. That is, first, in the additive manufacturing process, a layer of metal powder is irradiated with an energy beam at a predetermined location to melt and bond the metal powder at that location to form a bonding layer, and then a layer of metal powder is further coated on this bonding layer, and an energy beam is irradiated at a predetermined location to melt and bond the metal powder at that location and form a new bonding layer integrated with the lower bonding layer. This process is repeated to produce an additive manufactured object (hereinafter sometimes referred to as a laminated body) in which multiple bonding layers are laminated and integrated. Next, in the processing process, excess material on the surface of the additive manufactured object is removed to obtain a three-dimensional shaped object (hereinafter sometimes simply referred to as a molded object) with the desired dimensional accuracy and surface condition.

[0003] Patent Document 1 discloses an invention for manufacturing a mold by three-dimensional modeling technology, characterized in that a solidified layer is formed so that the surface area on which a force is applied to the three-dimensional shaped body due to contact with a fluid or solid object during use becomes a high-density area with a solidification density of 95 to 100%, the three-dimensional shaped body is used as a mold for the core side or cavity side, and cutting is performed on a part of the surface area where the core side and the cavity side come into contact when the mold is used. As a result, the invention of Patent Document 1 forms a high-density area only in necessary places on the mold and performs cutting on that part, thereby shortening the manufacturing time and reducing the manufacturing cost of the mold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5539347 [Patent Document 2] Patent No. 6504064 Summary of the Invention [Problem to be solved by the invention]

[0005] The manufacturing method of Patent Document 1 is an invention that assumes that a mold is manufactured by three-dimensional modeling. The surface area where the core side and the cavity side come into contact when the mold is used generally accounts for a relatively small proportion of the entire surface area of ​​a three-dimensionally shaped object. Therefore, when a mold is manufactured by three-dimensional modeling, the proportion of the cost of cutting a part of the surface area where the core side and the cavity side come into contact when the mold is used to the total manufacturing cost required for forming the high-density region and for the cutting process is considered to be relatively small for the mold.

[0006] In recent years, three-dimensional modeling technology is being applied not only to molds but also to the manufacture of many metal products and metal parts (hereinafter, collectively referred to as general components). It is sometimes required to manufacture general components using three-dimensional modeling technology by forming a high-density region in more or all of the surface region, rather than a part of the surface region, and by performing cutting on the high-density region, to give the desired dimensional accuracy and surface condition. In such cases, the proportion of the cost required for forming the high-density region and cutting the high-density region in the total manufacturing cost is considered to be higher than that in the case of mold manufacturing assumed in Patent Document 1, and the manufacturing method of Patent Document 1 cannot necessarily be said to be suitable as a means for shortening the manufacturing time and reducing the manufacturing cost of general components. In particular, when using a material with poor machinability called a difficult-to-cut material, the proportion of the cutting processing cost in the total manufacturing cost tends to be particularly high, so a manufacturing method that allows efficient cutting is required.

[0007] The method for manufacturing a metal member in Patent Document 2 is a method for manufacturing a metal member in which a predetermined region of a metal powder layer spread on a base is irradiated with a light beam to repeatedly form a selectively melted and solidified shaping layer, thereby forming a metal member having an overhang portion together with a support member supporting the overhang portion. The metal member has a hollow portion in the center and an overhang portion above the hollow portion. A solid support member is formed inside the hollow portion, a gap of 0.3 to 0.8 mm is provided over the substantially entire boundary surface between the overhang portion and the support member, an anchor film including a honeycomb structure is formed between the support member and the metal member below the hollow portion, and a recess is formed in the support member for separating and removing the support member from the metal member. This invention is said to make it possible to easily separate and remove the support member. However, this manufacturing method has a problem that, since there is a gap at the boundary surface between the overhang portion and the support member, when a large load is applied to the overhang portion due to processing, etc., the overhang portion is displaced, making it difficult to obtain high processing accuracy.

[0008] The object of the present invention is to provide a method for manufacturing a three-dimensional shaped object that is suitable when high-density areas are formed over more or all of the surface area rather than just a portion of the surface area by three-dimensional modeling, and that imparts the desired dimensional accuracy and surface condition by performing cutting on the high-density area, and that can reduce the proportion of cutting costs in the overall manufacturing cost compared to conventional methods, particularly when manufacturing a three-dimensional shaped object made of a difficult-to-cut material. [Means for solving the problem]

[0009] The present invention has been made in view of the above-mentioned problems. That is, the method for producing a three-dimensional shaped object of the present invention includes an additive manufacturing step of irradiating a predetermined portion of a powder layer with an energy beam to melt and bond the metal powder at the portion to form a bonding layer, coating the bonding layer with a layer of metal powder, irradiating the predetermined portion with an energy beam to melt and bond the metal powder at the portion and forming a new bonding layer integrated with the lower bonding layer, and repeating the above steps to produce an additive manufacturing object in which a plurality of bonding layers are laminated and integrated, and a processing step of removing excess parts from the additive manufacturing object to obtain a three-dimensional shaped object, in which in the additive manufacturing step, a portion having a relatively different strength is formed in at least a portion of the bonding layer to form a high-strength portion that becomes the three-dimensional shaped object, and a low-strength portion adjacent to the high-strength portion that is relatively lower in strength than the high-strength portion, and in the processing step, a portion of the high-strength portion and the low-strength portion adjacent thereto are removed by processing as the excess part. In addition, the terms "high strength" and "low strength" used herein refer to the relative relationship of strength.

[0010] In the method for manufacturing a three-dimensional shaped object of the present invention, it is preferable that the additively shaped object has a support portion, which supports a portion corresponding to the three-dimensional shaped object and has a strength relatively lower than that of the high-strength portion, and that the support portion is removed after the processing step.

[0011] In the method for manufacturing a three-dimensional shaped object of the present invention, the layered shaped object can be fixed using the support part in the processing step.

[0012] In the method for manufacturing a three-dimensionally shaped object of the present invention, it is preferable that a hardness ratio of the low strength portion to the high strength portion is 0.9 or less.

[0013] In the method for producing a three-dimensionally shaped object of the present invention, the metal powder may be a metal powder made of a Ni-based alloy.

[0014] In the method for manufacturing a three-dimensionally shaped object of the present invention, the low-strength layer and the high-strength layer can be formed by changing the energy density of the energy beam. Effect of the Invention

[0015] According to the present invention, there is provided a method for manufacturing a three-dimensional shaped object, in which high-density areas are formed in more or all of the surface area rather than just a portion of the surface area by three-dimensional modeling, and the high-density areas are then cut to impart the desired dimensional accuracy and surface condition.In particular, when manufacturing a three-dimensional shaped object made of a difficult-to-cut material, a method for manufacturing a three-dimensional shaped object can be provided that can reduce the proportion of cutting costs in the overall manufacturing cost compared to conventional methods. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram showing a portion of a cross section of a laminate produced based on three-dimensional data of the laminate in an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a part of a cross section of a laminate in which distortion has occurred in an embodiment of the present invention. [Diagram 3] 3 is a diagram showing a shaped body obtained after removing excess material from the laminate of FIG. 2. FIG. [Figure 4] FIG. 13 is a diagram showing a part of a cross section of a laminate produced based on three-dimensional data of the laminate in a conventional embodiment. [Diagram 5] FIG. 13 is a diagram showing a part of a cross section of a laminate in which distortion occurs in a conventional embodiment. [Figure 6] 6 is a diagram showing a shaped body obtained after removing excess material from the laminate of FIG. 5. FIG. [Figure 7] FIG. 2 is a three-view diagram of the layered object after the layered manufacturing process of Example 1, represented by trigonometry. [Figure 8] FIG. 8 is a cross-sectional view of FIG. [Figure 9] FIG. 2 is a three-view diagram, expressed by trigonometry, of the layered object after the processing step (drilling holes) of Example 1. [Figure 10]FIG. 2 is a three-view diagram, expressed by trigonometry, of the layered object after the processing step (reamer processing) of Example 1. [Figure 11] FIG. 1 is a three-view diagram, expressed by trigonometry, of the layered object after the processing step (removal of the base plate) of Example 1. [Figure 12] FIG. 2 is a three-view diagram, expressed by trigonometry, of the layered object after the processing step (support removal) of Example 1. [Figure 13] FIG. 13 is a diagram showing a cross section of a thin-walled, three-dimensionally curved layered object after the layered modeling process of Example 2. [Figure 14] FIG. 13 is a diagram illustrating a cross section of an additive manufacturing body after a processing step in Example 2. [Figure 15] FIG. 13 is a diagram showing a cross section of the layered object after the processing step (plate removal) of Example 2. [Figure 16] FIG. 11 is a three-view diagram showing a T-shaped additive manufacturing object in which two cylindrical members are integrated together after the additive manufacturing process of Example 3. [Figure 17] FIG. 11 is a three-view drawing showing a T-shaped layered object in which two cylindrical members are integrated after the processing step (removal of the base plate) of Example 3. [Figure 18] FIG. 11 is a three-view drawing illustrating a T-shaped additive manufacturing object in which two cylindrical members are integrated together after the processing step (processing) of Example 3. [Figure 19] FIG. 11 is a three-view drawing illustrating a T-shaped additive manufacturing object in which two cylindrical members are integrated together after the processing step (support removal) of Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] One of the factors that increases the proportion of cutting processing costs in the overall manufacturing cost is distortion of the laminate due to residual thermal stress caused by the additive manufacturing process or the subsequent heat treatment process. Figure 4 shows a part of a cross section including the outer surface of a laminate produced based on three-dimensional data of the laminate. The lamination direction of the bonding layer is from bottom to top in the figure. However, distortion is not reflected in this laminate. In Figure 4, a part of the cross section including the outer surface of the laminate is surrounded by a dashed line indicating that only the outer surface, which is the laminate surface 1a, the upper surface 1d, the lower surface 1e, and a part of the cross section are shown. In a processing process after the additive manufacturing process or the subsequent heat treatment process, the excess part 1B surrounded by points A, B, C, and D is removed from the laminate 1 by cutting processing or the like, and a molded body 1A with the processed surface 1c as the outer surface instead of the laminate surface 1a is obtained.

[0018] The reason why the laminate 1 requires a predetermined amount of excess pad portion 1B will be explained. Although the distortion is not reflected in the laminate in FIG. 4, the laminate 1 may actually have distortion after the additive manufacturing process or the subsequent heat treatment process. FIG. 5 shows a part of the cross section of the laminate in which distortion has occurred. However, for ease of explanation, it is assumed that the distortion occurs only on the laminate surface 1a, and not on the upper surface 1d and the lower surface 1e. It is known that the laminate is distorted due to residual thermal stress generated in the additive manufacturing process or the subsequent heat treatment process. The distortion is not uniform, and depending on the part of the molded body, it becomes a positive distortion or a negative distortion with respect to the design dimensions. As a result, as shown in FIG. 5, a laminate surface 1a' that does not match the shape of the original laminate surface 1a is formed, and excess pad portion 1B' (points A', B, C, D') that does not match the cross-sectional shape (points A, B, C, D) of the original excess pad portion 1B is formed. The excess pad portion 1B' in Figure 5 maintains approximately the same cross-sectional area as the excess pad portion 1B in Figure 4, but has a positive distortion in the length on the upper surface 1d side from AB to A'-B, and a negative distortion in the length on the lower surface 1e side from CD to C-D'.

[0019] The excess material 1B' is removed from the laminate 1 by cutting to obtain a shaped body (general component) 1A (Fig. 6). The purpose of providing the excess material 1B' is to ensure a processing allowance for imparting the desired dimensional accuracy and surface condition to the shaped body 1A by removing it. When the excess material 1B' is removed, the laminated surface 1a' is lost, and the processed surface 1c that appears in its place becomes the new outer peripheral surface, making it possible to impart the desired dimensional accuracy and surface condition to the shaped body 1A.

[0020] In order for the machining surface 1c to be completely formed without any chipping, a sufficient thickness of the excess pad portion 1B' must be secured. The thickness of the excess pad portion is the length measured from a specified point on the machining surface 1c to the lamination surface 1a' in the perpendicular direction. In particular, the excess pad must cover the machining surface 1c even on the lower surface 1e side where the maximum negative distortion occurs and the excess pad portion 1B' is the thinnest. There is variation in the phenomenon in which a metal body affected by heat is distorted, and the location and amount of distortion are not necessarily the same even when comparing metal bodies of the same material, shape, and size. Therefore, it is necessary to make the thickness of the excess pad portion (length CD (length AB)) in the design sufficiently thick so that a certain thickness (length CD') of excess pad is secured on the machining surface 1c even in the area where a large negative distortion occurs. On the other hand, in the area where a large positive distortion occurs, the thickness of the excess pad portion becomes length A'B, which creates the problem of being too thick. If the thickness of the excess metal portion (length CD (length AB)) is determined in this manner, the volume of the excess metal portion 1B' will be large as a result, and more time and cost will be required to remove it by cutting.

[0021] Near net shaping is a method for minimizing the volume of excess material as much as possible to reduce the number of steps required for cutting. Near net shaping is a technique for determining the design dimensions of a laminate so as to minimize excess material, taking into account the location and amount of distortion that are determined in advance by simulation or actual measurement. This technique is effective for laminates that are relatively small or have a simple shape, but is not necessarily effective for laminates that are relatively large or have a complex shape.

[0022] The present invention has been made in view of the above-mentioned problems. That is, the manufacturing method of the three-dimensional shaped object of the present invention includes an additive manufacturing process in which a layer of powder is irradiated with an energy beam at a predetermined location to melt and bond the metal powder at the location to form a bonding layer, a layer of metal powder is coated on the bonding layer, and an energy beam is irradiated at a predetermined location to melt and bond the metal powder at the location and form a new bonding layer integrated with the lower bonding layer, and the above steps are repeated to produce an additive manufacturing object in which a plurality of bonding layers are laminated and integrated, and a processing process in which an excess part is removed from the additive manufacturing object to obtain a three-dimensional shaped object, and in the additive manufacturing process, a part having a relatively different strength is formed in at least a part of the bonding layer to form a high-strength part that becomes the three-dimensional shaped object, and a low-strength part adjacent to the high-strength part that is relatively lower in strength than the high-strength part is formed, and in the processing process, a part of the high-strength part and the low-strength part adjacent thereto are removed by processing as the excess part. Hereinafter, the manufacturing method of the three-dimensional shaped object of the present invention will be described with reference to Figs. 1 to 3.

[0023] [Additive manufacturing process] In the additive manufacturing process, an additive manufacturing object is produced from raw powder based on three-dimensional data using a three-dimensional modeling machine. More specifically, a bonding layer is formed by irradiating a predetermined portion of a powder layer with an energy beam to melt and bond the metal powder at that portion, and a layer of metal powder is coated on the bonding layer, and an energy beam is irradiated to a predetermined portion to melt and bond the metal powder at that portion and form a new bonding layer integrated with the lower bonding layer. This is repeated to produce an additive manufacturing object in which multiple bonding layers are laminated and integrated. In the additive manufacturing process, a high-strength portion that becomes a three-dimensional shape object and a low-strength portion adjacent to the high-strength portion and having a strength relatively lower than that of the high-strength portion are formed by forming portions of at least a portion of the bonding layer that are relatively different in strength.

[0024] FIG. 1 shows a part of a cross section including the outer periphery of a laminate produced based on three-dimensional data of the laminate. The lamination direction of the bonding layer is from bottom to top in the figure. However, distortion is not reflected in this laminate. In FIG. 1, a part of the cross section including the outer periphery of the laminate is surrounded by a dashed line indicating that only the outer periphery, which is the lamination surface 1a, the upper surface 1d, the lower surface 1e, and a part of the cross section are shown. In the processing step after the additive manufacturing process or the subsequent heat treatment process, the excess part 1B surrounded by points A, B, C, and D is removed from the laminate 1 by cutting or the like, and a molded body 1A with the processed surface 1c as the outer periphery instead of the laminate surface 1a is obtained. As already mentioned, the laminate 1 requires the excess part 1B of sufficient design thickness (length AB (CD)) because distortion occurs. The excess part 1B is the high-strength excess part 1B on the processed surface 1c side. H and low-strength excess part 1B on the lamination surface 1a side L The two are in contact with each other at the strength interface 1f. The strength interface 1f is formed between the lamination surface 1a and the processing surface 1c, but does not coincide with the lamination surface 1a or the processing surface 1c. High-strength excess pad portion 1B H is a relatively hard high strength part, and the low strength excess part 1B is L consists of low-strength parts with relatively low hardness. In the present invention, hardness is used to evaluate strength, and high-hardness parts are called high-strength parts and low-hardness parts are called low-strength parts. The shaped body 1A can have a structure in which it is entirely made of high-strength parts, or a structure in which at least the processed surface 1c and its neighboring parts are made of high-strength parts and the other parts (interior) are made of low-strength parts, combining high-strength parts and low-strength parts. The outer periphery of the bonding layer that constitutes the surface of the laminate (low-strength excess part 1B L ) is the low strength part, and the bonding layer (high strength excess part 1B) except for the outer periphery is H The low-strength portion and the high-strength portion can be integrally formed from the same raw powder by changing the molding conditions.

[0025] To produce a laminate having a high-strength part with high hardness and a low-strength part with low hardness from the same material, it is necessary to change the output, scanning speed, scanning interval, etc. of the energy beam irradiated to the metal powder layer, and to adjust the energy density (J / mm2) supplied to the metal powder layer in each of the high-strength layer and the low-strength layer of the bonding layer. 3 ) can be adjusted. To form a high-strength layer, the energy density can be increased, and to form a low-strength layer, the energy density can be decreased. In particular, it is preferable to adjust the energy density by making the scanning speed variable. By irradiating the energy beam at a high scanning speed, the energy density is reduced, making it possible to form a low-strength layer and complete the additive manufacturing in a shorter time. As described above, at least a part of the bonding layer can be formed to consist of a high-strength layer and a low-strength layer. That is, it is possible to form a portion having different strength in a layer perpendicular to the stacking direction (in-plane direction). [Laminated body after the additive manufacturing process]

[0026] FIG. 2 shows a part of the cross section of the laminated body where distortion has occurred. However, for ease of explanation, it is assumed that distortion occurs only on the lamination surface 1a, and not on the upper surface 1d or the lower surface 1e. As shown in FIG. 2, a lamination surface 1a' that does not match the shape of the original lamination surface 1a is formed, and an excess pad portion 1B' (points A', B, C, D') that does not match the cross-sectional shape (points A, B, C, D) of the original excess pad portion 1B is formed. The excess pad portion 1B' in FIG. 2 has a positive distortion in the length on the upper surface 1d side from AB to A'-B while maintaining approximately the same cross-sectional area as the excess pad portion 1B in FIG. 1, and a negative distortion in the length on the lower surface 1e side from CD to C-D'. The excess pad portion 1B' is a high-strength excess pad portion 1B' on the processed surface 1c side. H and the low-strength excess portion 1B' on the lamination surface 1a' side. L The two are in contact with each other at a strength interface 1f'. The strength interface 1f' is formed between the lamination surface 1a' and the processing surface 1c, but does not coincide with the lamination surface 1a' or the processing surface 1c.

[0027] In order to completely form the machined surface 1c without any chipping, the excess pad 1B' must be thick enough. In particular, the high-strength excess pad 1B' must be secured on the machined surface 1c even on the lower surface 1e side where the maximum negative distortion occurs and the excess pad 1B' is the thinnest. H and low strength excess part 1B' L must overlap. [Processing process]

[0028] In the processing step, excess material portion 1B' is removed from the layered product 1 to produce a three-dimensional shaped product 1A (Fig. 3). In the processing step, a part of the high strength portion and the adjacent low strength portion are removed as excess material portion by processing. More specifically, the depth to which the excess material portion is removed from the surface of the layered product is made greater than the depth of the low strength portion. When removing excess material portion 1B', first, low-strength excess material portion 1B' on the outer periphery of layered product 1 is removed. L The low strength excess part 1B' is removed by cutting. L is high strength excess part 1B' H Even if the material is the same as that of the high-strength excess part 1B', it is laminated to have a lower hardness. H The machinability is improved compared to the high strength excess material portion 1B'. H When the excess pad portion 1B' is removed by cutting, the layered surface 1a' is lost, and the processed surface 1c that appears in its place becomes a new outer peripheral surface, and the desired dimensional accuracy and surface condition can be imparted to the shaped body 1A. L The higher the ratio of the excess pad 1B', the easier it is to cut and remove the excess pad 1B'. However, even on the lower surface 1e side where the maximum negative strain occurs and the excess pad 1B' is the thinnest, a certain thickness of high-strength excess pad 1B' remains on the processed surface 1c. H Therefore, low strength excess part 1B' L It is not preferable to make the ratio too high.

[0029] The larger the product, the greater the distortion of the laminate and the larger the volume of the excess material. The increase in excess material leads to increased cutting costs and reduced productivity. This is particularly noticeable for laminates made of Ni-based alloys such as NCF718 (JIS) alloy and MAT21 (MAT21 is a registered trademark of Hitachi Metals, Ltd.), which are considered difficult to cut.

[0030] NCF718, a precipitation-strengthened alloy, is characterized by excellent tensile strength, fatigue strength, creep strength, and rupture strength at a maximum temperature of 700°C, and is widely used as an aerospace structural material for high-temperature applications such as jet engine disk materials and rocket engines. Generally, NCF718 is considered to be an alloy that is difficult to cut because of its high high-temperature strength and low thermal conductivity.

[0031] MAT21 is an excellent environmentally resistant nickel-based alloy, and its representative composition is Ni-19Cr-19Mo-1.8Ta (mass%). MAT21 is a new corrosion-resistant alloy that exhibits high corrosion resistance in a variety of environments, making it applicable to multipurpose / multi-reaction plants, pharmaceutical manufacturing plants with small corrosion tolerances, and semiconductor manufacturing equipment, as well as having excellent corrosion resistance against sulfuric acid dew-point corrosion that occurs in flue gas desulfurization equipment, etc.

[0032] (Reference example 1) An additive manufacturing body (hereinafter sometimes referred to as a laminate) consisting of a high-strength portion was produced, processed, and evaluated as follows. [Raw material powder] The raw material for the three-dimensional shaped object was NCF718 alloy powder produced by gas atomization. The particle size distribution of this alloy powder was D10 = 19.0 μm, D50 = 31.6 μm, and D90 = 51.5 μm. D10, D50, and D90 are the particle sizes at 10%, 50%, and 90% of the sample volume, respectively, on the volume cumulative distribution curve from the small particle size side.

[0033] [Additive manufacturing process] Using a three-dimensional modeling machine, EOS M290, a rectangular laminate consisting of a high-strength portion and measuring 50 mm in length, 50 mm in width, and 30 mm in height was fabricated from the above raw material powder based on three-dimensional data.

[0034] The additive manufacturing conditions for the high-strength parts were as follows: Laser type: Yb-fiber Laser output: 350 (W) Scanning speed: 1300 (mm / s) Scanning interval: 0.11 (mm) Laser beam diameter: 0.1 (mm) Energy density: 61.2 (J / mm 3 ) Molding temperature...80(℃) Metal powder layer thickness: 40 (μm)

[0035] [Processing process] The excess material was removed from the surface of the laminate obtained in the additive manufacturing process by cutting under the following conditions.

[0036] The conditions for cutting the excess material were as follows: Tool type: 2-blade end mill, diameter 10 (mm) Tool material: Carbide + coating Feed per tooth: 0.05 (mm / t) Cutting depth: 10 (mm) Cutting width: 0.2 (mm) Cutting speed...40(m / min)

[0037] [evaluation] After cutting 10,000 mm, the cutting resistance of the tool and the average width of the rake face wear, where the rake face of the tool was gouged away, were measured and taken as the cutting resistance and the amount of tool wear, respectively.

[0038] (Reference example 2) A laminate consisting of low strength parts was produced, processed and evaluated as follows. [Raw material powder] The same materials as in Reference Example 1 were used.

[0039] [Additive manufacturing process] The additive manufacturing conditions for the low-strength parts were scanning speed 3100 (mm / s) and energy density 25.7 (J / mm 3 A similar laminate was produced under the same additive manufacturing conditions as in Reference Example 1, except that

[0040] [Processing process] The excess material was removed from the surface of the laminate under the same cutting conditions as in Reference Example 1 to obtain a similar shaped body.

[0041] [evaluation] After cutting 10,000 mm, the cutting resistance and the amount of tool wear were measured in the same manner as in Reference Example 1.

[0042] (Reference example 3) A laminate consisting of low strength parts was produced, processed and evaluated as follows. [Raw material powder] The same materials as in Reference Example 1 were used.

[0043] [Additive manufacturing process] The additive manufacturing conditions for the low-strength parts were scanning speed 3700 (mm / s) and energy density 21.5 (J / mm 3 A similar laminate was produced under the same additive manufacturing conditions as in Reference Example 1, except that

[0044] [Processing process] The excess material was removed from the surface of the laminate under the same cutting conditions as in Reference Example 1 to obtain a similar shaped body.

[0045] [evaluation] After cutting 10,000 mm, the cutting resistance and the amount of tool wear were measured in the same manner as in Reference Example 1.

[0046] (Reference example 4) A laminate consisting of low strength parts was produced, processed and evaluated as follows. [Raw material powder] The same materials as in Reference Example 1 were used.

[0047] [Additive manufacturing process] The additive manufacturing conditions for the low-strength parts were scanning speed 4600 (mm / s) and energy density 17.3 (J / mm 3 A similar laminate was produced under the same additive manufacturing conditions as in Reference Example 1, except that

[0048] [Processing process] The excess material was removed from the surface of the laminate under the same cutting conditions as in Reference Example 1 to obtain a similar shaped body.

[0049] [evaluation] After cutting 10,000 mm, the cutting resistance and the amount of tool wear were measured in the same manner as in Reference Example 1.

[0050] [Table 1]

[0051] [Reference example results] The results are shown in Table 1. Both the cutting resistance and the tool wear amount of the laminate made of the high strength part obtained in Reference Example 1 were large, and the proportion of the cutting processing cost in the total manufacturing cost was large. As a result of suppressing both the cutting resistance and the tool wear amount, especially the tool wear amount, for the laminate made of the low strength part obtained in Reference Examples 2 and 3, the proportion of the cutting processing cost in the total manufacturing cost could be reduced compared to Reference Example 1. As a result of suppressing both the cutting resistance and the tool wear amount of the laminate made of the low strength part obtained in Reference Example 4, the proportion of the cutting processing cost in the total manufacturing cost could be further reduced compared to Reference Example 1. The density ratio and hardness ratio of the low strength part to the high strength part were also measured in each reference example. The hardness was expressed as Rockwell hardness HRB. It was found that the reduction in the density ratio and hardness ratio of the low strength part increased as the energy density for forming the bond layer was reduced by adjusting the energy beam irradiation conditions, and the cutting resistance and tool wear amount tended to decrease. From the results of Reference Examples 2 to 4, it was found that the effect of further reducing the proportion of cutting processing costs in the total manufacturing costs can be obtained by preferably setting the hardness ratio of the low strength portion to the high strength portion to 0.9 or less, and more preferably setting the hardness ratio to 0.6 or less. On the other hand, from the viewpoint of forming a sound layered product, it is preferable to set the hardness ratio of the low strength portion to the high strength portion to 0.2 or more in order to sufficiently ensure fusion bonding between the metal powders in the low strength portion and / or integration between the bonding layers.

[0052] Example 1 A laminate consisting of a high strength portion and a low strength portion was produced and processed as follows. [Three-dimensional shaped object] In this example, a metal member having a horizontal T-shape, simulating a mechanical part, and having a highly accurate hole was produced (FIGS. 7 to 12). [Raw material powder] The same materials as in Reference Example 1 were used.

[0053] [Additive manufacturing process] FIG. 7 is a three-sided view of the laminated body after the additive manufacturing process, expressed by trigonometry. The additive manufacturing process starts on the base plate 50, and the bonding layers are repeatedly formed in a direction perpendicular to the base plate, and ends when the pre-designed additive manufacturing body 100 is produced. Specifically, a bonding layer is formed by irradiating a predetermined portion of the powder layer with an energy beam to melt and bond the metal powder at that portion, and a layer of metal powder is coated on the bonding layer, and an energy beam is irradiated to a predetermined portion to melt and bond the metal powder at that portion and form a new bonding layer integrated with the lower bonding layer. This is repeated to produce an additive manufacturing body in which multiple bonding layers are laminated and integrated. In the additive manufacturing process, a high-strength portion that becomes a three-dimensional shape molded body and a low-strength portion adjacent to the high-strength portion that is relatively weaker than the high-strength portion are formed by forming a portion with a relatively different strength in at least a portion of the bonding layer. The T-shaped shape is a structure in which the standing portion 10 rising from the base plate and the overhang portion 20 supported by the standing portion 10 are integrated. In a later process, a hole with a vertical central axis is provided in the overhang portion, but in the additive manufacturing process, a hole formation portion 30 with a diameter slightly smaller than the diameter of the hole is formed. Since the overhang portion is formed on the powder layer, the support is unstable, making it difficult to mold with high precision. To solve this problem, a support 40 is formed under the overhang portion. The support supports the overhang portion 20, which is the portion corresponding to the three-dimensional shaped object. The support is a low-strength portion that is relatively weaker than the standing portion 10 and the overhang portion 20, which are high-strength portions, but has sufficient strength to suppress the displacement of the overhang portion 20 during processing. The support 40 supports the overhang portion, which is the portion corresponding to the three-dimensional shaped object, making it possible to mold the overhang portion with high precision. The support is removed after the processing process.

[0054] 8 shows a plan view of the laminate (bonding layer) in the middle of being molded. At the position AA, the bonding layer 101 is formed to consist of a high-strength layer that constitutes the standing portion 10 and a low-strength layer that constitutes the support 40, and at the position BB, the bonding layer 101 is formed to consist of a high-strength layer that constitutes the standing portion 10 and the overhang portion 20 and a low-strength layer that constitutes the hole forming portion 30. The standing portion and the overhang portion are high-strength portions formed by laminating high-strength layers, and the support and the hole forming portion are low-strength portions formed by laminating low-strength layers.

[0055] A laminate was produced under the same additive manufacturing conditions as in Reference Example 1, except that the energy beam scanning speed and energy density for forming the high-strength layer (part) / low-strength layer (part) were as follows. Scanning speed: 1300 (mm / s) / 4600 (mm / s) Energy density: 61.2 (J / mm 3 ) / 17.3(J / mm 3 )

[0056] [Processing process] In the processing step, a hole was formed in the overhanging part of the laminate by machining, and then the support (low strength part) was removed to obtain a three-dimensional shaped object. First, a pilot hole 31 with a diameter slightly smaller than the diameter of the final hole was drilled in the hole forming part of the overhanging part (FIG. 9). The pilot hole was formed through the overhanging part and halfway through the support. The hole forming part (low strength part) 30 was left around the pilot hole. One of the important points for realizing high-precision hole processing is that the amount of deformation of the overhanging part during pilot hole processing is small. In this embodiment, since the support is structured to support the overhanging part from below, the overhanging part is less likely to deform during pilot hole processing, and high-precision pilot holes can be formed. Although the support in this embodiment has a structure in which low-strength layers are laminated, it has a structure in which voids are uniformly distributed, and therefore has higher rigidity than supports consisting of an assembly of thin plates, rods, or needles that are often seen in conventional supports. This is also one of the reasons why the overhanging part is less likely to deform during pilot hole processing. In particular, a large processing load is applied to the drill in a laminate made of a difficult-to-cut material, but since there is a support and the hole formation portion is formed of a low-strength portion, the processing load is suppressed and the dimensional accuracy of the pilot hole is improved. Next, the pilot hole is reamed to completely remove the remaining low-strength portion, which is the excess material, and a part of the overhang portion, which is the high-strength portion, is removed as the excess material (FIG. 10). A hole 32 having a highly accurate diameter, straightness, and surface roughness could be formed in the overhang portion. The reason why a highly accurate hole could be formed is because the pilot hole is highly accurate and the reaming process itself has high processing accuracy for the same reason as the pilot hole processing. Next, the laminate and the base plate were separated (FIG. 11). Finally, the support was removed from the laminate to obtain a three-dimensional shaped object 200 (FIG. 12). Since the support is formed of a low-strength portion, processing and removal are relatively easy. Note that the low-strength portion of the hole formation portion and the low-strength portion of the support do not necessarily have to have the same density or hardness.

[0057] Example 2 A laminate consisting of a high strength portion and low and high strength portions was produced and processed as follows. [Three-dimensional shaped object] In this example, a metal member having a thin wall and a three-dimensional curved surface shape like a turbine blade was produced. Cross-sectional views of the metal member are shown in Figs. 13 to 15. [Raw material powder] The same materials as in Reference Example 1 were used.

[0058] [Additive manufacturing process] 13 is a diagram showing a cross section of a thin-walled, three-dimensionally curved additive object after the additive manufacturing process. The additive manufacturing process starts from the base plate, and bonding layers are repeatedly formed in the direction perpendicular to the base plate, and ends when the predesigned additive manufacturing object 300 is produced. Specifically, a layer of powder is irradiated with an energy beam at a predetermined location to melt and bond the metal powder at that location to form a bonding layer, and a layer of metal powder is coated on this bonding layer, and an energy beam is irradiated at a predetermined location to melt and bond the metal powder at that location and form a new bonding layer integrated with the lower bonding layer. This process is repeated to produce an additive manufacturing body in which multiple bonding layers are laminated and integrated. In the additive manufacturing process, each bonding layer is formed so that the inside is a high-strength layer and the adjacent outer periphery is a low-strength layer in the planar direction of each bonding layer, and the additive manufacturing body 300 is formed so as to have a high-strength part 60 made of a high-strength layer and a low-strength part 70 made of a low-strength layer.

[0059] The conditions for producing the layered object were the same as in Example 1.

[0060] [Processing process] In the processing step, the laminated body was fixed at one end, and the low-strength portion 70 forming the outer periphery of the laminated body 300 was processed and removed as excess material while moving a rotating end mill in three axial directions, to cut out a three-dimensional curved shape. All low-strength portions on the outer periphery of the laminated body and the surface of the high-strength portion 60 inside the laminated body were cut and removed slightly (FIG. 14), and finally the base plate 50 was removed to obtain a thin-walled metal member 400 having a three-dimensional curved shape (FIG. 15). In general, laminated bodies made of difficult-to-cut materials are subjected to a large processing load on the end mill, and in addition, when the laminated body is thin and fixed at one end, the laminated body is likely to escape from the end mill, especially at the tip part far from the fixed part, making high-precision processing difficult. In contrast, in this embodiment, the outer periphery of the laminated body was formed from a low-strength portion, so the processing load on the end mill was relatively small, and the laminated body was unlikely to escape from the end mill even at the tip part far from the fixed part, making high-precision processing possible.

[0061] Example 3 A laminate consisting of a high strength portion and low and high strength portions was produced and processed as follows. [Three-dimensional shaped object] In this example, a metal member was produced in which two cylindrical members were integrated to form a T shape, and one of the cylindrical members had highly accurate outer dimensions (FIGS. 16 to 19). [Raw material powder] The same materials as in Reference Example 1 were used.

[0062] [Additive manufacturing process] FIG. 16 is a three-sided view showing a T-shaped additively manufactured body in which two cylindrical members are integrated after the additive manufacturing process. The additive manufacturing process starts on the base plate 50, and repeatedly forms bonding layers in a direction perpendicular to the base plate, and ends when the pre-designed additively manufactured body 500 is manufactured. Specifically, a bonding layer is formed by irradiating a predetermined portion of the powder layer with an energy beam to melt and bond the metal powder at that portion, and a layer of metal powder is coated on the bonding layer, and an energy beam is irradiated at a predetermined portion to melt and bond the metal powder at that portion and form a new bonding layer integrated with the lower bonding layer. The additively manufactured body 500 in which multiple bonding layers are laminated and integrated is manufactured. In the additive manufacturing process, the bonding layers were formed using three formation methods. The first is a formation method of the support 110 ((a) of FIG. 16), in which each bonding layer is formed only from a low-strength layer. The second is a method for forming the large cylindrical member 80 and a part of the small cylindrical member 90 (FIG. 16(b)), in which each bonding layer is formed only from a high-strength layer. The third is a method for forming the connection between the support and the large cylindrical member (FIG. 16(c)) and the remainder (tip) of the small cylindrical member (FIG. 16(d)), in which each bonding layer is formed so that the inside of the bonding layer in the planar direction is a high-strength layer and the adjacent outer periphery is a low-strength layer. In the additive manufacturing process, the additive manufacturing body is formed so that it is composed of a high-strength part made of a high-strength layer and a low-strength part made of a low-strength layer. The support supports the entire part corresponding to the three-dimensional shape body. In this embodiment, the amount of overhang of the large cylindrical member 80 from the support 110 is relatively small, so the large cylindrical member 80 was molded soundly.

[0063] The conditions for producing the layered object were the same as in Example 1.

[0064] [Processing process] Generally, if a curved surface is gripped during processing of a workpiece, the workpiece is not stable. In addition, in a laminate, the surface as-formed is rougher than the processed surface, and the gripping force of the laminate tends to be low. In the processing step of this embodiment, the base plate was first removed from the entire laminate (Fig. 17). Next, the support was slightly surface-ground to reduce the surface roughness, and then the support was gripped. When attempting to grip a large cylindrical member, the curved surface must be gripped, making the laminate unstable, but if a support having at least a pair of parallel surfaces such as a rectangular parallelepiped is used, the laminate can be gripped strongly. Next, the low-strength portion 120 at the tip of the small cylindrical member was entirely processed and removed as an excess portion, and the high-strength portion below it was processed and removed slightly as an excess portion, giving the tip of the small cylindrical member a highly accurate outer dimension (Fig. 18). When removing the low-strength portion 120, if a part of the adjacent small cylindrical member (high-strength portion) 90 is also removed, a slight step will be created. Line 91 of small cylindrical member 90 in Figure 18 indicates this step. Finally, the support was removed to obtain metal member 600 consisting of a high-strength portion (Figure 19). In general, a laminate consisting of a difficult-to-cut material places a large processing load on the cutting tool, and at processing points far from the gripping point of the laminate, the laminate is prone to slip away from the cutting tool, making high-precision processing difficult. In contrast, in this embodiment, the support for the laminate was left and used as a gripping member, so the laminate could be strongly fixed, and because the processing portion was formed from a low-strength portion, the processing load on the cutting tool was relatively small, and the laminate was unlikely to slip away from the cutting tool even at processing points far from the gripping point, making high-precision processing possible. [Industrial Applicability]

[0065] The present invention relates to a method for producing three-dimensionally shaped objects from a raw material metal powder using a so-called 3D printer, and is particularly useful as a manufacturing method for three-dimensionally shaped objects made of difficult-to-cut materials that are difficult to cut, which facilitates cutting of the layered object after modeling, reduces the proportion of cutting costs in total manufacturing costs compared to conventional methods, and provides high processing accuracy. [Explanation of symbols]

[0066] 1. Layered object, laminate 1A Three-dimensional shaped object, object (high strength part) 1B Extra flesh part 1B' Extra flesh part 1a Laminated surface 1a' Laminated surface 1c Machining surface 1d top surface 1e Bottom side 1f strength interface 1f' strength interface 1B H High strength surplus part (high strength part) 1B' H High strength surplus part (high strength part) 1B L Low strength surplus part (low strength part) 1B' L Low strength surplus part (low strength part) 10 Standing section (high strength section) 20 Overhang section (high strength section) 30 Hole forming part (low strength part) 31 Pilot hole 32 holes 40 Support (low strength part) 50 Base plate 60 High strength section 70 Low strength section 80 Large cylindrical member 90 Small cylindrical member 100 Additive Manufacturing 101 Bonding layer 110 Support 120 Low strength section 200 Three-dimensional shaped object 300 Additive Manufacturing 400 Metallic parts 500 Additive Manufacturing 600 Metallic parts

Claims

1. an additive manufacturing process in which an energy beam is irradiated to a predetermined location of the powder layer to melt and bond the metal powder at that location to form a bonding layer, a layer of metal powder is coated on the bonding layer, and an energy beam is irradiated to a predetermined location to melt and bond the metal powder at that location and form a new bonding layer integrated with the underlying bonding layer, and the process is repeated to produce an additive manufacturing object in which multiple bonding layers are stacked and integrated; and a processing step of removing excess material from the layered object to obtain a three-dimensional shaped object, In the additive manufacturing process, a high-strength portion that becomes the three-dimensional shaped object and a low-strength portion that is adjacent to the high-strength portion and has a strength relatively lower than that of the high-strength portion are formed by forming a portion having a relatively different strength in at least a part of the bonding layer, In the processing step, a part of the high strength portion and the low strength portion adjacent thereto are removed by processing as the excess material portion; the additively manufactured body has a support portion having a strength relatively lower than that of the high-strength portion, the support portion supporting a portion corresponding to the three-dimensional shaped body, and the support portion being removed after the processing step.

2. The method for manufacturing a three-dimensionally shaped object according to claim 1 , wherein in the processing step, the layered object is fixed using the support part.

3. The method for manufacturing a three-dimensionally shaped object according to claim 1 or 2, wherein a hardness ratio of the low strength portion to the high strength portion is 0.9 or less.

4. 4. The method for manufacturing a three-dimensionally shaped object according to claim 1, wherein the metal powder is made of a Ni-based alloy.

5. an additive manufacturing process in which an energy beam is irradiated to a predetermined location of the powder layer to melt and bond the metal powder at that location to form a bonding layer, a layer of metal powder is coated on the bonding layer, and an energy beam is irradiated to a predetermined location to melt and bond the metal powder at that location and form a new bonding layer integrated with the underlying bonding layer, and the process is repeated to produce an additive manufacturing object in which multiple bonding layers are stacked and integrated; and a processing step of removing excess material from the layered object to obtain a three-dimensional shaped object, In the additive manufacturing process, a high-strength portion that becomes the three-dimensional shaped object and a low-strength portion that is adjacent to the high-strength portion and has a strength relatively lower than that of the high-strength portion are formed by forming a portion having a relatively different strength in at least a part of the bonding layer, In the processing step, a part of the high strength portion and the low strength portion adjacent thereto are removed by processing as the excess material portion; a low-strength portion and a high-strength portion being formed by changing an energy density of the energy beam;

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