JP2003321704A - Lamination shaping method and lamination shaping apparatus used in the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lamination shaping method by which the necessary shaping accuracy can be secured and a sufficient strength can be imparted to a lamination shaped article. <P>SOLUTION: In the lamination shaping method, a shape is formed by repeatedly laminating a unit shaped layer having a prescribed shape which is formed by selectively irradiating a thin layer of a shape-forming material with laser light so as to cause selective bonding or hardening. In such a lamination shaping method, when the unit shaped layer is formed, a pattern to be irradiated with the laser light is divided into a high accuracy treatment section D and a high strength treatment section F, and a certain range along the contour L of the irradiation pattern is included in the high accuracy treatment section D. In the high accuracy treatment section D, the shape-forming material is irradiated with the laser light of a first irradiation level, and in the high strength treatment section F, the shape-forming material is irradiated with laser light of a second irradiation level higher than the first irradiation level. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a layered modeling method in which unit modeling layers are sequentially formed by laser irradiation and stacked to form a target modeled object, and a layered modeling apparatus used therefor.

[0002]

2. Description of the Related Art The additive manufacturing method is a method in which a large number of thin unit molding layers are laminated to perform molding, and has an excellent feature that any complicated shape can be easily modeled. It is used as a suitable method for manufacturing machine parts having various shapes, or for manufacturing a prototype for examining the suitability of a design shape for an industrial product having a high design property. When manufacturing machine parts and the like by the additive manufacturing method, a heat-fusible powder material based on a metal material is generally used as a forming material, and the following three steps including the additive manufacturing process are performed. Is normal.
In the first stage process, which is a layered manufacturing process, a primary intermediate body (layered product), which is also called a green part, is formed by a laser sintering process which is also called selective laser sintering (Selective Laser Sintering). FIG. 7 schematically shows one structural example of an apparatus used in laser sintering. The laser sintering device (lamination manufacturing device) is a mirror that controls irradiation of a sintering table piston 1, a powder material supply piston 2, a spreading roller 3, a laser 4 using a CO 2 laser, and a laser beam 5 from the laser 4. 6 and a lens system 7 for converging the beam of the laser light 5. The sintering table piston 1 and the powder material supply piston 2 are provided inside a chamber 8 whose temperature can be controlled.

The laser sintering work by such a laser sintering apparatus is performed as follows. First, the powder material supply piston 2 is raised by a predetermined height to measure the powder material 9 to be supplied to the sintering table piston 1, and the spreading roller 3 measures the measured amount of the powder material 9 by the sintering table piston 1. A thin layer having a thickness of, for example, about 100 μm is spread on the surface of The thin layer of this powder material is then irradiated with laser light. The irradiation of the laser light is performed in a predetermined pattern by controlling the mirror 6 with a control system (not shown). The irradiation pattern is a pattern corresponding to the shape of each slice surface obtained by virtually slicing the target product into a large number of layers. The data relating to the slice plane of the target product is usually obtained by computer processing the three-dimensional data (three-dimensional CAD data or X-ray CT data) of the target product.

When a thin layer of powder material is irradiated with laser light,
At the irradiation site, the powder material is thermally fused and sintered, whereby one unit modeling layer 1 having a laser light irradiation pattern, that is, a shape corresponding to the shape of one slice plane.
0 is formed. When the formation of one unit modeling layer 10 is completed, the sintering table piston 1 is lowered by the thickness thereof, and subsequently the same operation as above is repeated. By repeating this series of operations several times, the unit molding layers 10, 10, ... Are sequentially laminated, and if the number of lamination reaches a predetermined number, that is, the number of slices of the target product, the primary intermediate product (laminated molding) of the target product is obtained. can get. An example of the above laser sintering method is disclosed in, for example, Japanese Patent Publication No. 11-508322.

Here, the powder material is heat-fusible, and the heat-fusible property includes an indirect type and a direct type. The indirect type is a type in which powder particles are coated with a binder and the binder exhibits a heat fusion property. on the other hand,
The direct type is a type that causes the powder particles themselves to exhibit heat fusion. As a typical example of the indirect type, there is one in which powder particles of a metal as a material of a target product are coated with a binder made of a synthetic resin or a binder made of a low melting point metal.

In the second step, the primary intermediate obtained in the first step is subjected to main sintering in a heating furnace. By undergoing the main sintering in the process of the second stage, a secondary intermediate body called brown parts is obtained. This secondary intermediate is a porous body having a high porosity. Therefore, the work of increasing the strength by filling the voids by infiltration of the infiltrant to obtain the final product is performed as the third step. If the base of the powder material is a metal, for example, bronze is used as the infiltrant.

The above is a typical example of the steps when the additive manufacturing method is used as a method for manufacturing practical products such as machine parts. In addition, the additive manufacturing method is also used to manufacture a prototype or the like for examining the suitability of a design. The layered modeling method in this case is also called an optical modeling method, and, for example, a modeling material in which a photosensitive resin that is cured by ultraviolet rays is liquefied is used. In this stereolithography method, layered modeling is performed by using a modeling apparatus having a structure in which a vertically movable movable table is provided in a tank filled with a liquid photosensitive resin. That is, a thin layer of the photosensitive resin liquid is generated on the table surface of the movable table in the tank filled with the liquid photosensitive resin, and the thin layer is irradiated with laser light in a predetermined pattern, so that the irradiation pattern is changed. The photosensitive resin is cured in a corresponding pattern to form one unit modeling layer. When the formation of one unit modeling layer is completed, the movable table is lowered by the thickness of the unit modeling layer to generate a thin layer for the next unit modeling layer on the formed unit modeling layer and similarly irradiate the laser beam. And the next unit modeling layer is formed. After that, generation of a thin layer by lowering the movable table and formation of a unit modeling layer by irradiating it with a laser beam are repeated a predetermined number of times to obtain a desired modeled object.

[0008]

In the additive manufacturing process (laser sintering process) for manufacturing the above mechanical parts, etc., when a thin layer of powder material is irradiated with laser light, the irradiation spot is mainly focused. Then, a certain range is heat-fused and sintered. Assuming that the curing range centered on this irradiation spot by heat fusion is called "sintering unit",
This sintering unit has a size corresponding to the irradiation amount of laser light (normally expressed as the irradiation energy amount per unit area). That is, the sintering unit becomes large when the irradiation amount of the laser beam is large, and becomes small when the irradiation amount is small. The surface accuracy of the primary intermediate body is determined according to the size of the sintering unit, and the modeling accuracy of the final product is determined accordingly. From this, it is understood that, in the layered manufacturing by laser sintering, the irradiation amount of the laser light with which the powder material is irradiated is extremely important for the modeling accuracy of the product.

Conventionally, the irradiation amount of laser light has been suppressed below a certain level in order to secure the modeling accuracy. For example, when a powder material obtained by coating powder particles of stainless steel with a synthetic resin binder having a heat fusion temperature of about 200 ° C. is used as the powder material, about 0.7 J / mm 2 is the upper limit,
The irradiation amount is usually about 0.2 to 0.7 J / mm 2.

As described above, the primary intermediate in the conventional additive manufacturing method (additive manufacturing object) obtained by irradiating the laser beam with a reduced irradiation amount in order to ensure the accuracy of modeling is a so-called partial fusion of powder particles due to thermal fusion. It was in a state in which it was mechanically bonded and was very brittle. Therefore, even a slight impact will cause damage, and since careful handling is required from the laser sintering process to the main sintering process, the work efficiency is significantly reduced, and even with the utmost caution. The fact is that the occurrence of breakage is unavoidable and the yield is often 30% or less.

In addition, it is necessary to keep the irradiation amount of the laser light below a certain level in relation to the modeling accuracy, and therefore it becomes impossible to give sufficient strength to the modeled object. The same applies when manufacturing. That is, in the stereolithography method, when the irradiation amount of the laser light is increased, the influence of scattered light on the outer edge of the laser light irradiation pattern becomes large. When the scattered light causes the curing of the photosensitive resin to the outside of the irradiation pattern of the laser light,
The molding accuracy will be impaired. Therefore, it is necessary to suppress the irradiation amount of laser light to a certain level or less, and as a result, it becomes impossible to give sufficient strength to the layered product.

The present invention has been made against the background of the conventional circumstances as described above, and a layered manufacturing method capable of ensuring a required modeling accuracy and imparting sufficient strength to a layered modeled product. It is intended to be provided.

[0013]

To achieve the above object, according to the present invention, a thin layer of a molding material is selectively irradiated with laser light to cause selective bonding and curing. The formation of a unit modeling layer having a shape corresponding to the selective irradiation pattern is sequentially repeated, and in the layered modeling method in which modeling is performed while stacking the unit modeling layers of this repeated formation, in forming the unit modeling layer, the laser beam The irradiation pattern is divided into a high-precision processing section and a high-intensity processing section, and the high-precision processing section includes a certain range along the contour of the irradiation pattern, and with respect to the high-intensity processing section. Is characterized in that the high-precision processing unit is irradiated with laser light at a larger irradiation amount than the irradiation amount of laser light.

Further, in the present invention, in the additive manufacturing method as described above, the irradiation intensity of the laser beam is changed so that the irradiation amount of the laser beam for each of the high-precision processing section and the high-intensity processing section is made different.

Further, in the present invention, in the additive manufacturing method as described above, after uniformly irradiating the whole of the irradiation pattern of the laser light with the predetermined irradiation amount, only the high-intensity processing portion has the predetermined irradiation amount. By further irradiating the high-precision processing section and the high-intensity processing section with each other, the irradiation amount of the laser light is made different.

Further, in the present invention, with respect to the additive manufacturing apparatus used in the additive manufacturing method as described above, the control system thereof is provided with irradiation intensity setting means for setting the irradiation intensity for each of the high precision processing section and the high intensity processing section. I am trying.

Further, in the present invention, in the additive manufacturing apparatus used in the additive manufacturing method as described above, an irradiation spot diameter adjusting means for adjusting the irradiation spot diameter of the laser beam is provided in the control system.

Further, in the present invention, regarding the additive manufacturing apparatus used in the additive manufacturing method as described above, under the control of the control system, the entire irradiation pattern of the laser light is uniformly irradiated with the laser light at a predetermined irradiation amount. The whole irradiation process and the high-intensity processing part irradiation process of further irradiating the high-intensity processing part with laser light at a predetermined irradiation amount after the whole irradiation process are performed for each formation of the unit modeling layer. Are

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to the embodiments of the present invention. FIG. 1 schematically shows the configuration of the additive manufacturing apparatus used in the first embodiment of the present invention. This additive manufacturing apparatus is basically the same as the conventional additive manufacturing apparatus (laser sintering apparatus) described above, and a control system 11 for controlling the irradiation of the laser beam is controlled by a mirror based on a predetermined irradiation pattern. The difference lies in that an irradiation pattern setting means 12 for controlling 6 is provided, and in addition, an irradiation intensity setting means 13 and an irradiation spot diameter adjusting means 14 are provided.

In the description of the first embodiment, it is assumed that a product having a sectional shape as shown in FIG. 2, that is, a rectangular parallelepiped practical product M having a bent square tube-shaped hollow portion P is laminated and manufactured as a target product. The law shall be implemented. If this target product is designed by, for example, a three-dimensional CAD system, the target product is sliced into a number of layers from the three-dimensional CAD data, and shape data regarding each slice plane S as shown in FIG. create. Based on this data, the irradiation pattern setting means 12 of the control system 11 controls the mirror 6 in the layered manufacturing apparatus of FIG. 1 so that the laser beam is applied to the thin layer of the powder material in a pattern according to the shape of the slice surface. Irradiation is performed to form one unit modeling layer having a shape corresponding to the shape of one slice surface.
When the formation of one unit modeling layer is completed, the sintering table piston 1 is lowered by the thickness thereof. After that, by repeating such a process in sequence, the unit modeling layers are laminated up to a predetermined number of layers to form a primary intermediate (laminated model) of the target product. The thus-obtained primary intermediate is subjected to main sintering to become a secondary intermediate, and the final intermediate product is completed by subjecting this secondary intermediate to infiltration treatment.

Up to this point, the process is the same as the conventional additive manufacturing method for manufacturing practical products. In the present invention, when the unit modeling layer is formed, the inside of the irradiation pattern of the laser light is divided into a high-intensity processing part and a high-precision processing part, and the irradiation amount of the laser light is made different for these two parts.
That is, regarding the high-strength processing portion, the strength is emphasized, and the irradiation with the laser beam at the second irradiation level, which is a larger irradiation amount than that used in the conventional laser sintering process (lamination manufacturing), is sufficient. Sufficient strength, that is, the primary intermediate obtained in the laser sintering process can be provided with sufficient strength to facilitate its handling. On the other hand, with respect to the high-precision processing unit, the modeling precision is emphasized, and sufficient modeling precision is ensured by irradiating the laser beam at the first irradiation amount level, which is an irradiation amount smaller than the irradiation amount for the high-strength processing unit. . The first dose level with emphasis on modeling accuracy uses a powder material in which metal powder particles are coated with a synthetic resin binder having a heat fusion temperature of about 200 ° C., as in the conventional laser sintering method. In some cases, it is usually about 0.2 to 0.7 J / mm 2. On the other hand, the intensity-focused second dose level is set to be at least twice the first dose level, and more preferably at least five times.

In order to make the irradiation amount of the laser beam different between the high-intensity processing section and the high-accuracy processing section as described above, in the present embodiment, the irradiation of the high-accuracy processing section and the irradiation of the high-intensity processing section are performed. The setting of the irradiation intensity of laser light is changed. The irradiation intensity setting means 13 changes the setting. One method of setting the irradiation intensity by the irradiation intensity setting means 13 is to control the operating state of the laser 4 by controlling the operating current. In addition to this, for example, a beam diameter adjusting means (not shown) is provided in the optical path of the laser light 5, and the beam diameter adjusting means is controlled by the irradiation intensity setting means 13 to adjust the beam diameter of the laser light 5. A method of setting the irradiation intensity is also possible.

As described above, the high-intensity processing section is irradiated with laser light at an irradiation intensity that is 2 to 5 times or more the irradiation intensity of the high-precision processing section. Irradiation with such a strong laser beam may cause the powder material to be scattered by rapid heating. Therefore, when irradiating the high-intensity processing section, laser light 5
It is preferable to increase the diameter of the irradiation spot to reduce the rapidity of heating. In order to increase the irradiation spot diameter of the laser light 5, the irradiation spot diameter adjusting means 14 controls the lens system 7 to weaken the degree of convergence of the laser light 5 on the irradiation surface (the thin layer surface of the powder material). That is, normally, the focus of the lens system 7 is adjusted to the irradiation surface, but the focus is blurred with respect to the irradiation surface.

Here, in the case of performing additive manufacturing with the additive manufacturing apparatus of FIG. 1, a predetermined environmental temperature is set inside the chamber 8 and laser light irradiation is performed. The environmental temperature is usually about 100 ° C. when the heat fusion temperature of the powder material is about 200 ° C.

FIG. 4 shows an example of a division pattern of the high intensity processing section F and the high precision processing section D in the laser beam irradiation pattern. Such a division pattern is usually incorporated in advance in the laser light irradiation pattern. As can be seen from the example in the figure, there is one important condition for dividing the high-strength processing section and the high-precision processing section. That is, since there is a portion that directly affects the modeling accuracy in the laser light irradiation pattern, this portion must be included in the high precision processing section. The part that directly affects the modeling accuracy is a region within a certain range along the contour L of the laser light irradiation pattern (this is also the contour of the unit modeling layer). That is, in a certain range of the region along the contour of the laser beam irradiation pattern, the size of the above-mentioned sintering unit directly affects the surface accuracy of the unit modeling layer, and the surface accuracy defines the modeling accuracy. That is. A certain range along the contour of the laser beam irradiation pattern, that is, a range to be included in the high-precision processing unit correlates with the general size of the sintering unit. Specifically, it corresponds to a range of at least about 200 μm from the contour L.

As described above, a region within a certain range along the contour of the laser beam irradiation pattern is required to be included in the high precision processing section. However, the high precision processing set only along the contour of the laser beam irradiation pattern is performed. It is preferable that the range of parts is minimized. In other words, the strength near the surface of the primary intermediate has a great influence on the problem that the primary intermediate obtained in the laser sintering process is easily damaged. Therefore, it is a more preferable condition to increase the strength in the vicinity of the surface by minimizing the range of the high precision processing unit set along the contour of the laser light irradiation pattern.

Here, in the example of FIG. 4, the high-intensity processing section F and the high-precision processing section D are divided into a grid pattern, and the high-precision processing section is also applied to a portion other than a certain range along the contour of the laser beam irradiation pattern. Included in. That is, in this example, the high-precision processing section is made as wide as possible, and the high-strength processing section is kept within the minimum necessary range, that is, the minimum necessary range for providing the primary intermediate with sufficient strength for ensuring ease of handling. I am trying. As described above, the form in which the high-strength processing portion is minimized is one of the forms possible in the present invention. This form is adopted when importance is attached to the processing efficiency in the laser sintering process. When the high-strength processing section is to be minimized to a necessary minimum, various patterns can be used to distinguish the high-strength processing section and the high-precision processing section. In addition to the grid pattern as shown in FIG. A typical pattern is a circular pattern or a spoke pattern. These patterns can be generalized as patterns in which high-precision processing units are used as a matrix and high-strength processing units are skeletally set in the matrix.

Another possible form of the invention is to set the high-strength processing section as wide as possible, contrary to the form described above. FIG. 5 shows an example of a division pattern of the high-intensity processing unit F and the high-precision processing unit D in such a form. In this way, when setting the high-strength treatment part as wide as possible, the role of laser sintering is enhanced, and the high-strength treatment part is irradiated with laser light at an irradiation intensity that can achieve the same degree of sintering as the main sintering. Irradiate. By doing so, it is possible to improve the processing efficiency in the main sintering process that follows the laser sintering process.

Next, a second embodiment of the present invention will be described.
In the second embodiment, the additive manufacturing apparatus shown in FIG. 6 is used.
This additive manufacturing apparatus is basically the same as the additive manufacturing apparatus in the first embodiment. However, the control system 21 is different from that of the first embodiment in that a laser beam irradiation processing procedure setting unit 22 is provided in addition to the irradiation pattern setting unit 12. In the present embodiment, under the control of the laser light irradiation processing procedure setting unit 22, the laser light irradiation is performed in two steps for each unit modeling layer, so that the laser light for each of the high-precision processing unit and the high-intensity processing unit is irradiated. The irradiation dose is different. Specifically, first, a whole irradiation process of uniformly irradiating the entire laser light irradiation pattern with a predetermined irradiation amount of laser light is performed. The irradiation amount in this overall irradiation processing is the same as the irradiation amount in the high precision processing unit in the first embodiment. Then, following the overall irradiation process, a high-intensity processing unit irradiation process is performed in which only the high-intensity processing unit is further irradiated with laser light at a predetermined irradiation amount. The irradiation amount in this high-intensity processing unit irradiation process is 2 to 5 of the irradiation amount in the whole irradiation process when the total with the irradiation amount in the whole irradiation process.
The irradiation dose should be double or more. In this way, when the laser light irradiation is performed in two stages, it is not necessary to cause a situation in which the powder material is scattered in the high-intensity processing portion with a large irradiation amount, and thus the focus of the laser light is blurred. There is no need to control. Since other processing contents regarding the additive manufacturing are the same as those in the first embodiment, the description thereof will be omitted.

Each of the above embodiments is an example of manufacturing a practical product using a heat-fusible powder material as a modeling material. The present invention is not limited to these examples,
The present invention can be applied to the case where a prototype or the like is manufactured by the above-described stereolithography method, and it is possible to realize both the molding precision and the strength in the stereolithography method.

[0031]

As described above, according to the present invention, when forming a unit modeling layer by laser sintering, the irradiation pattern of laser light is divided into a high-precision processing part and a high-strength processing part, and the laser is applied at both parts. The irradiation amount of light is made different. As a result, it becomes possible to secure the required modeling accuracy and also secure sufficient strength, for example, the strength necessary to give the laminated product obtained by additive manufacturing the easiness of handling, and the usefulness of the additive manufacturing method. Can be further enhanced.

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a configuration of a layered modeling apparatus in a first embodiment.

FIG. 2 is a diagram showing an example of the shape of a target product.

FIG. 3 is a diagram showing a slice surface obtained by virtually slicing the product of FIG.

FIG. 4 is a diagram showing an example of a division pattern of a high-precision processing unit and a high-strength processing unit.

FIG. 5 is a diagram showing another example of a division pattern of a high-precision processing unit and a high-strength processing unit.

FIG. 6 is a diagram schematically showing a configuration of a layered modeling apparatus according to a second embodiment.

FIG. 7 is a diagram schematically showing a configuration example of a laser sintering device.

[Explanation of symbols]

5 laser light 9 Powder materials (modeling materials) 10 unit modeling layer 11 Control system 13 Irradiation intensity setting means 14 Irradiation spot diameter adjustment means D High-precision processing unit F High strength processing section L irradiation pattern outline M product S slice plane

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Claims (6)

[Claims] 1. A unit modeling layer having a shape corresponding to a selective irradiation pattern of laser light, which is formed by selectively irradiating a thin layer of a molding material with laser light to cause selective bonding and curing. In the layered manufacturing method in which the formation of the unit modeling layers is repeated by sequentially repeating the formation of the unit modeling layers, the high-precision processing section and the high-strength processing section are formed in the irradiation pattern of the laser beam when the unit modeling layers are formed. And, the high-precision processing unit shall include a certain range along the contour of the irradiation pattern, and for the high-intensity processing unit, from the irradiation amount of the laser light to the high-precision processing unit. The additive manufacturing method is characterized in that the laser light is irradiated with a large irradiation amount. 2. The additive manufacturing method according to claim 1, wherein the irradiation amount of the laser light is changed so that the irradiation amount of the laser light for each of the high-precision processing portion and the high-intensity processing portion is made different. 3. After uniformly irradiating the whole of the irradiation pattern of the laser light with the laser light at a predetermined irradiation amount, the high intensity processing section is further irradiated with the laser light at a predetermined irradiation amount, The additive manufacturing method according to claim 1, wherein the high-precision processing section and the high-intensity processing section are made to have different irradiation amounts of laser light. 4. An additive manufacturing apparatus for use in the additive manufacturing method according to claim 2, further comprising a control system, wherein the control system includes irradiation intensity for each of the high-accuracy processing unit and the high-intensity processing unit. An additive manufacturing apparatus provided with an irradiation intensity setting means for setting. 5. The additive manufacturing apparatus according to claim 4, wherein an irradiation spot diameter adjusting means for adjusting an irradiation spot diameter of the laser beam is provided in the control system. 6. An additive manufacturing apparatus for use in the additive manufacturing method according to claim 3, further comprising a control system, and under the control of the control system, a predetermined amount is provided in the entire irradiation pattern of the laser light. The whole irradiation process that uniformly irradiates the laser light with the irradiation amount of, and the high-intensity processing unit irradiation process that further irradiates the high-intensity processing unit with the predetermined irradiation amount only after the whole irradiation process A layered modeling apparatus that is configured to form each modeling layer.