Three-dimensional fabrication device

Abstract

A three-dimensional fabrication device (1) comprises a material holding part (3), an optical head (2), and a control unit (5). The control by the control unit (5) can be switched between a first rendering mode and a second rendering mode. In the first rendering mode, the scanning of a light beam is performed only one time for each position in a rendering region of a layer (92) to be rendered for which there is a rendering instruction in design data. In the second rendering mode, the scanning of the light beam is performed multiple times for each position in the rendering region in a state in which the amount of light applied to each position of the rendering region in each scan of the light beam is smaller than in the first rendering mode. This configuration makes it possible to precisely form a fabricated object.

Description

3D modeling device

[0001] The present invention relates to a three-dimensional modeling apparatus. [Reference to Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2023-148335, filed on September 13, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] In recent years, SLS (Selective Laser Sintering) three-dimensional modeling devices have been used, which irradiate a modeling material such as resin powder or metal powder with modulated laser light to melt the modeling material and then solidify it to create a three-dimensional model.

[0003] For example, in a powder bed type three-dimensional modeling apparatus, a thin layer of resin powder is spread on a build platform, and a laser beam is scanned over the resin powder layer using a galvanometer mirror or the like to melt the powdered resin in the area irradiated with the laser beam. This operation is then repeated to stack and solidify the molten resin powder, thereby creating a model. In a powder bed type three-dimensional modeling apparatus, the resin powder on the build platform is generally heated to a predetermined preheat temperature that is several degrees Celsius to several tens of degrees Celsius lower than the melting point of the resin powder, and the resin powder maintained at the preheat temperature is irradiated with a laser beam (JP 2021-509094 A (Document 1)).

[0004] In the resin powder layer on the build platform, the temperature of the laser beam irradiated area (i.e., the imaging area) rises, causing thermal diffusion to the non-imaging area surrounding the imaging area. Furthermore, the amount of laser beam light gradually changes near the boundary between the imaging area and the non-imaging area, so the amount of light at the edge of the non-imaging area is not zero. Therefore, in a narrow non-imaging area sandwiched between two imaging areas, the thermal diffusion from the imaging area and the amount of light at the edge of the imaging area can cause unintended melting of the resin powder, potentially reducing the dimensional accuracy of the molded object.

[0005] Furthermore, when new resin powder is supplied onto a layer of resin powder on which a pattern has been drawn (hereinafter also referred to as the "drawn layer") in the build platform, the temperature directly above the drawn area and surrounding areas of the drawn layer in the new resin powder layer may become higher than the predetermined preheat temperature. Therefore, when laser light is irradiated directly above the drawn area in the new resin powder layer, there is a risk of unintended melting of the resin powder around the irradiated area of ​​the laser light. In particular, as described above, there is a high possibility of unintended melting of the resin powder in the narrow non-drawn area sandwiched between two drawn areas.

[0006] An object of the present invention is to form a shaped object with high precision.

[0007] A first aspect of the present invention is a three-dimensional modeling apparatus comprising: a material holding unit including a stage for holding a powdered modeling material and a material supply unit for supplying the modeling material onto the stage; an optical head for scanning a light beam while modulating the modeling material held on the stage; and a control unit for controlling the material holding unit and the optical head based on design data of a model to repeatedly supply the modeling material onto the stage and scan the light beam on a target layer, which is a surface layer of the supplied modeling material, to melt the modeling material in an area irradiated with the light to draw a pattern. The control by the control unit is switchable between a first drawing mode in which the light beam scans only once for each position of a modeling area specified by the design data on the target layer; and a second drawing mode in which the light beam scans multiple times for each position of the modeling area, with a smaller amount of light imparted to each position of the modeling area per scan than in the first drawing mode.

[0008] According to the present invention, a shaped object can be formed with high precision.

[0009] Aspect 2 of the present invention is a three-dimensional printing apparatus according to aspect 1, wherein when a non-drawing area for which drawing is not instructed in the design data includes a narrow non-drawing area having a width equal to or less than a predetermined threshold, the control unit selects the second drawing mode.

[0010] Aspect 3 of the present invention is the three-dimensional modeling apparatus of Aspect 1 or 2, wherein the light intensity of the light beam in the second drawing mode is the same as the light intensity of the light beam in the first drawing mode, and the scanning speed of the light beam in the second drawing mode is greater than the scanning speed of the light beam in the first drawing mode.

[0011] A fourth aspect of the present invention is the three-dimensional modeling apparatus of the third aspect, wherein the number of scans of the light beam with respect to each position in the drawing area in the second drawing mode is two, and the scanning speed of the light beam in the second drawing mode is twice the scanning speed of the light beam in the first drawing mode.

[0012] Aspect 5 of the present invention is the three-dimensional modeling apparatus of Aspect 1 or 2, wherein the scanning speed of the light beam in the second drawing mode is the same as the scanning speed of the light beam in the first drawing mode, and the light intensity of the light beam in the second drawing mode is smaller than the light intensity of the light beam in the first drawing mode.

[0013] Aspect 6 of the present invention is the three-dimensional modeling apparatus of Aspect 1 or 2 (or any one of Aspects 1 to 5), wherein the number of scans of the light beam with respect to each position in the drawing area in the second drawing mode is two, and the amount of light imparted to each position in the drawing area in the first scan of the light beam in the second drawing mode is the same as the amount of light imparted to each position in the drawing area in the second scan of the light beam in the second drawing mode.

[0014] Aspect 7 of the present invention is the three-dimensional modeling apparatus of Aspect 1 or 2 (or any one of Aspects 1 to 5), wherein the number of scans of the light beam with respect to each position in the drawing area in the second drawing mode is 2. The amount of light imparted to each position in the drawing area in the first scan of the light beam in the second drawing mode is greater than the amount of light imparted to each position in the drawing area in the second scan of the light beam in the second drawing mode.

[0015] Aspect 8 of the present invention is the three-dimensional modeling apparatus of Aspect 1 or 2 (or any one of Aspects 1 to 7), in which the light beam is a multi-spot beam composed of a plurality of light spots linearly arranged in a predetermined arrangement direction, and the multi-spot beam is scanned in a predetermined scanning direction inclined with respect to the arrangement direction.

[0016] A ninth aspect of the present invention is the three-dimensional modeling apparatus of Aspect 1 or 2 (or any one of Aspects 1 to 8), further comprising a temperature measurement unit that measures a temperature distribution on an upper surface of the modeling material on the stage. The control unit adjusts the light intensity or scanning speed of the light beam in the second drawing mode based on the temperature distribution measured by the temperature measurement unit.

[0017] A tenth aspect of the present invention is the three-dimensional modeling apparatus according to the first or second aspect (or any one of the first to ninth aspects), wherein the modeling material is a resin material.

[0018] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings.

[0019] FIG. 1 is a diagram showing a configuration of a three-dimensional printing apparatus according to an embodiment; FIG. 2 is a diagram showing a configuration of a control unit; FIG. 3 is a block diagram showing functions of a control unit; FIG. 4 is a diagram showing a flow of forming a model; FIG. 5 is a perspective view of a model; FIG. 6 is a cross-sectional view of a model; FIG. 7 is a cross-sectional view of a model; FIG. 8 is a diagram showing a light intensity profile, etc. when drawing a pattern in a first drawing mode; FIG. 9 is a diagram showing a light intensity profile, etc. when drawing a pattern in a second drawing mode;

[0020] Fig. 1 is a diagram showing the configuration of a three-dimensional modeling apparatus 1 according to an embodiment of the present invention. The three-dimensional modeling apparatus 1 shown in Fig. 1 is a selective laser sintering (SLS) type three-dimensional modeling apparatus that irradiates a powdered modeling material with modulated laser light to melt the modeling material and then solidifies the material to perform three-dimensional modeling.

[0021] The above-mentioned modeling material is, for example, resin, metal, engineering plastic, or ceramic. The modeling material may contain multiple types of materials. In this embodiment, the modeling material is a powdered resin material. The resin material is a modeling material containing resin as the main component, and may also contain materials other than resin. The materials other than resin are, for example, materials (carbon particles, etc.) that have a relatively high absorptivity for the wavelength of the above-mentioned laser light.

[0022] The three-dimensional modeling apparatus 1 includes an optical head 2, a material holding unit 3, a temperature measuring unit 4, and a control unit 5. The material holding unit 3 is disposed below the optical head 2 and holds a powdered modeling material 91. In FIG. 1 , the material holding unit 3 is shown in vertical cross section, with the modeling material 91 indicated by parallel diagonal lines. The optical head 2 modulates and scans a laser beam (i.e., a light beam) over the modeling material 91 held by the material holding unit 3. The light irradiated from the optical head 2 onto the modeling material 91 is, for example, a multi-spot beam (i.e., a multi-spot line beam) composed of multiple light spots linearly arranged in a predetermined arrangement direction. The temperature measuring unit 4 measures the temperature of the modeling material 91 held in the material holding unit 3. The control unit 5 controls the optical head 2, the material holding unit 3, and the temperature measuring unit 4.

[0023] The material holding unit 3 includes a shaping unit 31 and a material supply unit 32. The shaping unit 31 includes a first cylinder 33 and a first piston 34. The first cylinder 33 is a cylindrical member extending in the vertical direction. The internal space of the first cylinder 33 has, for example, a substantially rectangular shape in a plan view. The first piston 34 is a member housed in the internal space of the first cylinder 33. The first piston 34 is movable in the vertical direction in the internal space of the first cylinder 33. The first piston 34 includes a substantially flat stage 341 that is substantially perpendicular to the vertical direction, and a support 342 that supports the stage 341 from below. The shape of the stage 341 in a plan view is substantially the same as the shape of the internal space of the first cylinder 33 in a plan view.

[0024] In the modeling unit 31, a three-dimensional space surrounded by the inner surface of the first cylinder 33 and the upper surface of the stage 341 serves as a modeling space 30 where three-dimensional modeling is performed. In the modeling space 30, a powdered modeling material 91 is held on the stage 341. In other words, the three-dimensional modeling device 1 is a powder bed type three-dimensional modeling device.

[0025] The modeling unit 31 includes a heater 38 that heats the modeling material 91 on the stage 341. The heater 38 applies energy substantially uniformly to the modeling material 91 on the stage 341, thereby raising the temperature of the modeling material 91 to a temperature below its melting point and maintaining that temperature. In the example shown in FIG. 1 , the heater 38 includes a first heater 381 and a second heater 382. The first heater 381 is a substantially flat electric heater provided above the stage 341. The first heater 381 is, for example, built into the stage 341 and is provided over substantially the entire surface of the stage 341 in a plan view. The second heater 382 is a halogen lamp that is disposed above the stage 341 at a distance and irradiates light toward the stage 341. The configuration, arrangement, etc. of the heater 38 are not limited to those described above and may be modified in various ways.

[0026] The material supply unit 32 includes a second cylinder 35, a second piston 36, and a squeegee 37. The second cylinder 35 is a cylindrical member extending in the vertical direction, and is disposed adjacent to the side of the first cylinder 33. The shape of the internal space of the second cylinder 35 in a plan view is, for example, approximately rectangular. The second piston 36 is a member housed in the internal space of the second cylinder 35. The second piston 36 is movable in the vertical direction within the internal space of the second cylinder 35. The shape of the second piston 36 in a plan view is approximately the same as the internal space of the second cylinder 35.

[0027] In the material supply unit 32, a three-dimensional space surrounded by the inner surface of the second cylinder 35 and the upper surface of the second piston 36 serves as a storage space for storing the molding material 91 to be supplied to the molding unit 31. The squeegee 37 is a rod-shaped (e.g., substantially cylindrical) or plate-shaped member that extends horizontally across the upper opening of the second cylinder 35. The squeegee 37 is movable horizontally along the upper end surface of the second cylinder 35.

[0028] In the material holding unit 3, when the modeling material 91 is supplied onto the stage 341, the first piston 34 of the modeling unit 31 descends a predetermined distance. As a result, the upper surface of the modeling material 91 on the stage 341 is positioned below the upper end surface of the first cylinder 33. Meanwhile, in the material supply unit 32, the second piston 36 rises a predetermined distance, and the modeling material 91 in the second cylinder 35 is lifted upward. Then, the squeegee 37 moves from above the second cylinder 35 to above the first cylinder 33, and the modeling material 91 protruding above the upper end surface of the second cylinder 35 is supplied into the modeling space 30 of the modeling unit 31. The upper surface of the modeling material 91 held in the modeling space 30 is positioned at approximately the same height as the upper end surface of the first cylinder 33.

[0029] The optical head 2 includes a laser light source 21, an illumination optical system 221, an optical modulator 222, a first projection optical system 223, a scanning unit 23, and a second projection optical system 224. The laser light source 21 emits laser light. The laser light source 21 is, for example, a fiber laser light source. The type of the laser light source 21 may be changed in various ways. The wavelength of the laser light emitted from the laser light source 21 is set appropriately according to the type of the modeling material 91, etc.

[0030] The illumination optical system 221, the optical modulator 222, and the first projection optical system 223 modulate the laser light emitted from the laser light source 21 into a modulated beam and guide it to the scanning unit 23. The second projection optical system 224 guides the multi-spot beam from the scanning unit 23 to the modeling material 91 on the stage 341. The illumination optical system 221, the first projection optical system 223, and the second projection optical system 224 each include a plurality of optical elements such as lenses.

[0031] The illumination optical system 221, for example, shapes the laser light from the laser light source 21 into a substantially rectangular shaped beam that is long in one direction (hereinafter referred to as the "long axis direction") and guides the beam to the optical modulator 222. In other words, the cross-sectional shape of the shaped beam is a substantially rectangular shape that is long in the long axis direction and short in the short axis direction perpendicular to the long axis direction. The long axis direction and the short axis direction are directions perpendicular to the traveling direction of the shaped beam (i.e., the optical axis direction). Furthermore, the cross-sectional shape of the shaped beam is the shape of the shaped beam on a plane perpendicular to the traveling direction of the shaped beam. The cross-sectional shape of the shaped beam can also be considered to be a substantially linear shape extending in the long axis direction.

[0032] The optical modulator 222 modulates the shaped beam from the illumination optical system 221 into a modulated beam and guides the modulated beam to the first projection optical system 223. For example, an LPLV (Linear Planar Light Valve), which is a type of PLV (Planar Light Valve), is used as the optical modulator 222. The modulated beam is a multi-spot beam composed of multiple light spots arranged linearly in the major axis direction. The gradation of each light spot of the multi-spot beam can be adjusted (i.e., the light intensity of the emitted light can be adjusted).

[0033] The optical modulator 222 does not necessarily have to be an LPLV, but may have other structures. Furthermore, the light irradiated from the optical head 2 to the modeling material 91 is not limited to the multi-spot line beam described above, and may be variously modified. For example, the optical head 2 may irradiate the modeling material 91 with a light beam consisting of a single light spot.

[0034] The scanning unit 23 reflects the modulated beam (i.e., the multi-spot beam) from the first projection optical system 223 and scans it on the building material 91 in the building space 30 of the material holding unit 3 via the second projection optical system 224. The scanning unit 23 includes, for example, a relay lens 231 and a galvanometer scanner 232. The galvanometer scanner 232 is a scanning mechanism including a galvanometer mirror 233 and a galvanometer motor (not shown). In the scanning unit 23, the galvanometer motor rotates the galvanometer mirror 233, thereby changing the traveling direction of the multi-spot beam reflected by the galvanometer mirror 233. As a result, the multi-spot beam irradiated onto the building material 91 is scanned in a scanning direction inclined with respect to the major axis direction of the multi-spot beam (i.e., the arrangement direction of the multiple light spots). The scanning direction is, for example, a direction perpendicular to the major axis direction on the top surface of the building material 91.

[0035] In the example shown in Fig. 1, the left-right direction in the figure is the scanning direction parallel to the stage 341. The direction perpendicular to the plane of Fig. 1 is the width direction (i.e., the arrangement direction of multiple light spots in the multi-spot beam) perpendicular to the scanning direction and parallel to the stage 341. Note that the scanning unit 23 does not necessarily need to include a galvano scanner and may have another structure.

[0036] The temperature measurement unit 4 measures the temperature distribution on the upper surface of the modeling material 91 on the stage 341. The temperature measurement unit 4 is, for example, an infrared thermography camera capable of capturing an image of substantially the entire upper surface of the modeling material 91 on the stage 341. The measurement results (for example, captured images) by the temperature measurement unit 4 are sent to the control unit 5.

[0037] 2 is a diagram showing the configuration of the control unit 5. The control unit 5 has the configuration of a typical computer system including a CPU 51, a ROM 52, a RAM 53, a fixed disk 54, a display 55, an input unit 56, a reading device 57, a communication unit 58, and a bus 50. The CPU 51 performs various arithmetic processing. The ROM 52 stores basic programs. The RAM 53 stores various information. The fixed disk 54 stores information. The display 55 is a display unit that displays various information such as images. The input unit 56 includes a keyboard 56a and a mouse 56b that accept input from an operator.

[0038] The reading device 57 reads information from a computer-readable recording medium 511 such as an optical disk, a magnetic disk, a magneto-optical disk, or a memory card. The display 55, the keyboard 56a, the mouse 56b, and the reading device 57 are connected to the bus 50 via an interface I / F. The communication unit 58 transmits and receives signals to and from components of the 3D printing apparatus 1 other than the control unit 5, as well as external devices. The bus 50 is a signal circuit that connects the CPU 51, ROM 52, RAM 53, fixed disk 54, display 55, input unit 56, reading device 57, and communication unit 58.

[0039] In the control unit 5, the program 512 is read in advance from the recording medium 511 via the reading device 57 and stored on the fixed disk 54. The program 512 may be stored on the fixed disk 54 via a network. The CPU 51 functions as a calculation unit that executes calculation processing using the RAM 53 and the fixed disk 54 in accordance with the program 512. Other components that function as a calculation unit other than the CPU 51 may be employed.

[0040] FIG. 3 is a diagram showing a functional configuration realized by the control unit 5 executing arithmetic processing and the like in accordance with the program 512. This functional configuration includes a storage unit 501, a scanning control unit 502, an intensity control unit 503, and a mode switching unit 504. All or part of these functions may be realized by dedicated electrical circuits. These functions may also be realized by multiple computers. Of the functional configuration shown in FIG. 3, the scanning control unit 502, the intensity control unit 503, and the mode switching unit 504 are realized by a CPU 51, a ROM 52, a RAM 53, a fixed disk 54, and their peripheral components. Furthermore, the storage unit 501 is mainly realized by the RAM 53 and the fixed disk 54.

[0041] The memory unit 501 stores various information such as design data of a three-dimensional object to be formed by the 3D printing apparatus 1. The scan control unit 502 adjusts the scanning speed of the multi-spot beam on the printing material 91 by controlling the galvanometer scanner 232 of the scanning unit 23, etc. The intensity control unit 503 adjusts the light intensity of the multi-spot beam irradiated onto the printing material 91 by controlling the laser light source 21, etc. The light intensity refers to the light energy irradiated per unit area per unit time on the printing material 91. The mode switching unit 504 switches the drawing mode of the 3D printing apparatus 1.

[0042] Next, an example of the flow of forming a model in the 3D printing apparatus 1 will be described with reference to FIG. 4 . In the 3D printing apparatus 1, first, design data of a 3D model to be formed is stored in the storage unit 501 of the control unit 5 (step S11). The design data is a collection of data representing cross sections of the model sliced ​​at predetermined thicknesses in the vertical direction (hereinafter also referred to as "cross-sectional data"). The cross-sectional data represents the shape of a portion corresponding to one layer when the model is divided into multiple layers stacked in the vertical direction. The control unit 5 may also perform predetermined corrections to the design data.

[0043] Next, the control unit 5 controls the material holding unit 3 to supply the powdered modeling material 91 onto the stage 341 (step S12). The modeling material 91 on the stage 341 is preheated by the heater 38 and maintained at a temperature lower than the melting point of the modeling material 91 and higher than the crystallization point (i.e., crystallization temperature) of the modeling material 91. For example, if a resin powder with a melting point of 185°C and a crystallization point of 150°C is used as the modeling material 91, the temperature of the modeling material 91 on the stage 341 is maintained at a temperature higher than 150°C and lower than 185°C (e.g., approximately 173°C). As a result, the modeling material 91 on the stage 341 remains in a powdered state without melting. Furthermore, the molten modeling material 91 on the stage 341 remains in a molten state without solidifying.

[0044] Then, the optical head 2 is controlled by the control unit 5, whereby the multi-spot beam is modulated using the design data (i.e., drawing data) and scanned in the scanning direction on the surface layer (hereinafter also referred to as the “drawing target layer 92”) of the modeling material 91 supplied onto the stage 341. As a result, the temperature of the modeling material 91 in the region of the modeling target layer 92 irradiated with the light rises to a modeling temperature equal to or higher than the melting point (e.g., approximately 220°C), melting the modeling material 91 in that region, and a pattern (i.e., a pattern formed by the molten modeling material 91) is drawn on the modeling target layer 92 (step S13).

[0045] The pattern writing in step S13 is performed by, for example, multi-pass writing, in which scanning of the multi-spot beam in the scanning direction and step movement in the width direction (i.e., the sub-scanning direction) are repeated to complete writing on the entire writing target layer 92. Note that the pattern writing may also be performed by single-pass writing, in which writing on the entire writing target layer 92 is completed by scanning the multi-spot beam once in the scanning direction.

[0046] In the imaging target layer 92, heat diffuses from the molten modeling material 91 in the region irradiated with light to the modeling material 91 surrounding the region. As a result, the temperature of the modeling material 91 in the region irradiated with light drops, but because the temperature of the modeling material 91 in the imaging target layer 92 is maintained at a temperature higher than the crystallization point by the heater 38, the modeling material 91 in the region is maintained in a molten state.

[0047] When the drawing of the pattern on the drawing target layer 92 is completed, it is confirmed whether or not the formation of the object is completed (step S14). If the formation of the object is not completed, the process returns to step S12, and a new drawing target layer 92 is formed by supplying new modeling material 91 onto the layer of modeling material 91 on which the pattern is drawn on the stage 341 (step S12). Then, the multi-spot beam is scanned over the new drawing target layer 92, and a pattern is drawn using the molten modeling material 91 (step S13).

[0048] As described above, in the pattern drawn in step S13, the modeling material 91 is maintained in a molten state, and in the pattern drawn in the previous step S13, the modeling material 91 is also maintained in a molten state. In this way, in the three-dimensional modeling apparatus 1, the modeling material 91 in a molten state is layered, and therefore, when solidified, a model having a high bonding strength in the layering direction (i.e., the vertical direction) is formed.

[0049] In the three-dimensional modeling apparatus 1, steps S12 to S13 are repeated until the formation of the model is completed. While steps S12 to S13 are being repeated, the heater 38 continues to heat the modeling material 91, and when the repetition of steps S12 to S13 is completed, the heater 38 also stops heating the modeling material 91. As a result, the modeling material 91, which has been maintained in a molten state in the above-described pattern, cools to below its crystallization point and solidifies, and a three-dimensional model is formed from the solidified modeling material 91.

[0050] Next, switching of the drawing mode in the 3D printing apparatus 1 will be described. In the 3D printing apparatus 1, the mode switching unit 504 of the control unit 5 can switch the drawing mode of the pattern drawing (i.e., scanning) performed in the above-mentioned step S13 between a first drawing mode and a second drawing mode. The first drawing mode is a so-called normal drawing mode, and can simplify the drawing operation of the 3D printing apparatus 1 in step S13 compared to the second drawing mode. On the other hand, the second drawing mode is a so-called high-precision drawing mode. In the second drawing mode, the drawing operation of the 3D printing apparatus 1 is more complicated compared to the first drawing mode, but the precision of the formed object can be improved. Below, the first drawing mode will be described first, and then the second drawing mode will be described.

[0051] In drawing a pattern in the first drawing mode, as described above, the multi-spot beam irradiated onto the modeling material 91 at a predetermined light intensity (hereinafter also referred to as the "first light intensity") is scanned over the modeling material 91 at a predetermined scanning speed (hereinafter also referred to as the "first scanning speed"). At this time, the irradiated area of ​​the multi-spot beam passes through each position on the upper surface of the modeling material 91 only once, thereby completing the drawing of the pattern. In other words, the light from the optical head 2 is not irradiated again onto the area of ​​the modeling target layer 92 of the modeling material 91 that has been irradiated with light and melted.

[0052] 5 is a perspective view showing a model 81 to be formed by the 3D printing device 1. The model 81 has a substantially rectangular parallelepiped shape, and a first groove 811 and a second groove 812 are provided on the top surface of the model 81. The first groove 811 and the second groove 812 are substantially linear grooves extending parallel to the scanning direction, and are provided over the entire length of the model 81 in the scanning direction. The depths of the first groove 811 and the second groove 812 are the same and are smaller than the height of the model 81. The size of the first groove 811 in the width direction is smaller than the size of the second groove 812 in the width direction.

[0053] Fig. 6 is a diagram showing a cross section 813 of the object 81 taken at the position VI-VI in Fig. 5. Fig. 7 is a diagram showing a cross section 814 of the object 81 taken at the position VII-VII in Fig. 5. The cross-sectional data corresponding to the cross sections 813 and 814 are included in the design data described above. In the cross section 813, the entire rectangular area corresponding to the object 81 is a drawing area 815 for which drawing is instructed in the design data. In Fig. 6, the drawing area 815 is indicated by parallel diagonal lines.

[0054] In cross section 814, of the rectangular regions directly above drawing region 815 in cross section 813, the rectangular band-shaped regions corresponding to first groove 811 and second groove 812, respectively, are non-drawing regions 816 and 817, for which drawing is not instructed in the design data. Furthermore, the rectangular regions to the left of non-drawing region 816, the rectangular region between non-drawing region 816 and non-drawing region 817, and the rectangular region to the right of non-drawing region 817 are drawing regions 815a, 815b, and 815c, for which drawing is instructed in the design data. In Figure 7, drawing regions 815a, 815b, and 815c are indicated by parallel diagonal lines.

[0055] In the example shown in FIG. 7 , the size in the width direction (i.e., the left-right direction in the figure) of the non-drawing region 816 corresponding to the first groove 811 is equal to or smaller than a predetermined threshold (hereinafter also referred to as the "narrow threshold"). Furthermore, the size in the width direction of the non-drawing region 817 corresponding to the second groove 812 is larger than the narrow threshold. In the following description, the non-drawing region 816 is also referred to as the "narrow non-drawing region 816." That is, in the example shown in FIG. 7 , the non-drawing regions 816 and 817 include the narrow non-drawing region 816.

[0056] FIG. 8 is a diagram showing a light intensity profile when a pattern corresponding to a cross section 814 is drawn in the first drawing mode. The diagram marked with (a) in FIG. 8 (hereinafter also referred to as FIG. 8(a)) is a diagram showing a pattern on the design data (i.e., a design pattern) in the cross section 814. FIG. 8(b) is a graph showing a light intensity profile of the multi-spot beam irradiated onto the drawing target layer 92. In FIG. 8(b), the horizontal axis indicates the width direction, and the vertical axis indicates the light intensity. The light intensity refers to the total amount of light energy irradiated to one position on the modeling material 91 in one scan of the optical head 2.

[0057] Fig. 8(c) is a diagram showing the temperature distribution in the drawing target layer 92 irradiated with the multi-spot beams having the light intensity profile shown in Fig. 8(b). The horizontal axis in Fig. 8(c) indicates the width direction, and the vertical axis indicates the temperature of the modeling material 91 in the drawing target layer 92. Fig. 8(d) is a diagram showing the actually drawn pattern (i.e., the drawing pattern) in the cross section 814.

[0058] In Fig. 8(b), the regions marked with reference numerals 711a, 711b, and 711c are ON regions where the spots of the multi-spot beam are turned on. Furthermore, the regions marked with reference numerals 712 and 713 are OFF regions where the spots of the multi-spot beam are turned off. In the ON regions 711a, 711b, and 711c, the multi-spot beam is scanned, and the temperature of the modeling material 91 in the drawing target layer 92 rises to a modeling temperature (e.g., 220°C) that is higher than the melting point of the modeling material 91 (e.g., 185°C), as shown by the solid line in Fig. 8(c).

[0059] As shown in Figure 8(b), the light intensity distribution in the ON region 711a is a substantially rectangular distribution. Furthermore, outside the widthwise ends of the ON region 711a, the light intensity does not suddenly become zero, but gradually decreases with increasing distance from the ON region 711a. In the following description, the light intensity generated outside the widthwise ends of the ON region 711a due to the light in the light spot of the ON region 711a is also referred to as the "edge light intensity." The same is true for the ON regions 711b and 711c.

[0060] In the OFF region 713 corresponding to the non-imaging region 817, which is relatively large in width, the light intensity at both ends in the width direction is slightly increased by the light intensity at the ends of the adjacent ON regions 711b and 711c. Furthermore, heat diffusion from the ON regions 711b and 711c also occurs in the OFF region 713. Therefore, as shown by the solid line in FIG. 8C , the temperature of the modeling material 91 in the OFF region 713 is slightly higher than the preheating temperature (e.g., 173°C).

[0061] On the other hand, in the OFF region 712 corresponding to the narrow non-drawing region 816 having a small width, as shown in FIG. 8B, the light intensity at the ends of the adjacent ON regions 711a and 711b is accumulated, resulting in a greater light intensity than in the OFF region 713 corresponding to the non-drawing region 817. Furthermore, the heat diffused from the ON regions 711a and 711b also overlaps in the OFF region 712. Therefore, as shown by the solid line in FIG. 8C, the temperature of the modeling material 91 in the OFF region 712 is higher than the temperature of the modeling material 91 in the OFF region 713.

[0062] Subsequently, due to thermal diffusion from the ON regions 711a, 711b, and 711c over time, the temperature of the modeling material 91 in the ON regions 711a, 711b, and 711c decreases, while the temperature of the modeling material 91 in the OFF regions 712 and 713 increases, as shown by the two-dot chain lines in FIG. 8(c). The state shown by the two-dot chain lines in FIG. 8(c) represents the temperature approximately 0.3 to 0.5 seconds after the end of irradiation of the ON regions 711a, 711b, and 711c with the multi-spot beam. As a result, the temperature of the modeling material 91 in the OFF region 712 becomes higher than its melting point (e.g., 185°C), which may result in unintended melting of the modeling material 91 in the OFF region 712.

[0063] 8D, if the forming material 91 melts in the OFF region 712, in the actual drawing pattern, the narrow non-drawing region 816 disappears between the drawing regions 815a and 815b, or the width of the narrow non-drawing region 816 becomes smaller than the design value. Note that, because the temperature of the forming material 91 in the OFF region 713 does not rise to its melting point, the forming material 91 does not melt in the OFF region 713. Therefore, the non-drawing region 817 exists between the drawing regions 815b and 815c.

[0064] As described above, in drawing using the first drawing mode, if the pattern includes a narrow non-drawing region 816, there is a possibility that the drawing accuracy of the narrow non-drawing region 816 will decrease. The possibility of this decrease in drawing accuracy is the same whether the width of the non-drawing region is small in the scanning direction or in the vertical direction.

[0065] Therefore, in the three-dimensional modeling apparatus 1, when a pattern includes a narrow non-drawing region 816, pattern drawing is performed in the second drawing mode instead of the first drawing mode. As described above, in the first drawing mode, scanning with the multi-spot beam is performed only once for each position in the drawing regions 815a to 815c. On the other hand, in the second drawing mode, scanning with the multi-spot beam is performed multiple times for each position in the drawing regions 815a to 815c. In the second drawing mode, the amount of light applied to each position in the drawing regions 815a to 815c in one scanning with the multi-spot beam is smaller than the amount of light applied to each position in the drawing regions 815a to 815c in the first drawing mode.

[0066] For example, in the second drawing mode, the light amount applied to each position in the drawing regions 815a to 815c in one scan of the multi-spot beam (hereinafter also referred to as the "light amount per scan") is set to approximately half that in the first drawing mode, and the multi-spot beam scans each position in the drawing regions 815a to 815c twice. Specifically, in the second drawing mode, the light intensity of the light beam irradiated onto the drawing regions 815a to 815c is set to the same as that in the first drawing mode, and the scanning speed of the multi-spot beam is set to approximately twice that in the first drawing mode, thereby setting the light amount per scan to approximately half that in the first drawing mode.

[0067] The following describes the pattern drawing in the first drawing mode and the second drawing mode in the 3D modeling apparatus 1, with reference to FIG. 9 and other figures. In the 3D modeling apparatus 1, the mode switching unit 504 checks (step S21) whether or not there are any narrow non-drawing regions in the design data stored in the storage unit 501 in step S11 (see FIG. 4). Specifically, each non-drawing region is extracted from the design data, and the minimum widths of each non-drawing region in the scanning direction, width direction, and vertical direction are compared with the narrow thresholds described above to check whether or not there are any non-drawing regions with widths equal to or smaller than the narrow thresholds (i.e., narrow non-drawing regions). Note that the narrow thresholds in the scanning direction, width direction, and vertical direction may be the same or different.

[0068] If the design data does not include a narrow non-drawing region, the mode switching unit 504 selects the first drawing mode as the drawing mode (step S22), and the object 81 is formed ( FIG. 4 : steps S12 to S14). In step S13 in the first drawing mode, as described above, scanning with the multi-spot beam of the first light intensity is performed only once at the first scanning speed for each position in the drawing region.

[0069] On the other hand, if the design data includes a narrow non-image-forming region, the mode switching unit 504 selects the second image-forming mode (step S23), and the model 81 is formed ( FIG. 4 : steps S12 to S14). In step S13 in the second image-forming mode, as described above, the multi-spot beam scans each position in the image-forming region twice. The light intensity of the multi-spot beam irradiated onto the modeling material 91 in the second image-forming mode (hereinafter also referred to as the "second light intensity") is the same as the first light intensity. Furthermore, the scanning speed of the multi-spot beam in the second image-forming mode (hereinafter also referred to as the "second scanning speed") is approximately twice the first scanning speed.

[0070] FIG. 10 is a diagram showing a light intensity profile and the like when drawing a pattern corresponding to the cross section 814 in the second drawing mode. FIGS. 10( a) to 10(d) correspond to FIGS. 8(a) to 8(d), respectively, for the first drawing mode. FIG. 10(a) is a diagram showing a design pattern in the cross section 814. FIG. 10(b) is a graph showing a light intensity profile of the multi-spot beam irradiated onto the drawing target layer 92 in the first of two scans of the multi-spot beam in the second drawing mode. As described above, the second light intensity is the same as the first light intensity, and the second scanning speed is approximately twice the first scanning speed. Therefore, the amount of light imparted to each of the ON regions 711a, 711b, and 711c in FIG. 10(b) is approximately half the amount of light imparted to each of the ON regions 711a, 711b, and 711c in FIG. 8(b).

[0071] Fig. 10(c) is a diagram showing a temperature distribution in the imaging target layer 92 scanned once with the multi-spot beam using the light intensity profile shown in Fig. 10(b). In the ON regions 711a, 711b, and 711c, a single scanning with the multi-spot beam causes the temperature of the modeling material 91 in the imaging target layer 92 to rise to a modeling temperature (e.g., 200°C) higher than the melting point (e.g., 185°C) of the modeling material 91, as shown by the solid line in Fig. 10(c). The modeling temperature (e.g., 200°C) in the second imaging mode is lower than the above-mentioned modeling temperature (e.g., 220°C) in the first imaging mode.

[0072] In the OFF regions 712 and 713, the temperature of the modeling material 91 rises above the preheating temperature (e.g., 173° C.) as shown by the solid line in FIG. 10C due to the influence of the light intensity at the edges of the adjacent ON regions 711 a, 711 b, and 711 c and thermal diffusion from the ON regions 711 a, 711 b, and 711 c, as in the case of the first drawing mode. Furthermore, in the OFF region 712 corresponding to the narrow non-drawing region 816, which is small in the width direction, the temperature of the modeling material 91 becomes higher than that of the OFF region 713 corresponding to the non-drawing region 817, which is relatively large in the width direction.

[0073] Thereafter, due to thermal diffusion from the ON regions 711a, 711b, and 711c over time, the temperature of the modeling material 91 in the ON regions 711a, 711b, and 711c decreases, while the temperature of the modeling material 91 in the OFF regions 712 and 713 increases, as shown by the two-dot chain lines in Fig. 10(c). The state shown by the two-dot chain lines in Fig. 10(c) represents the temperature approximately 0.3 to 0.5 seconds after the end of irradiation of the ON regions 711a, 711b, and 711c with the multi-spot beams.

[0074] In the second drawing mode, as described above, the amount of light applied to each of the ON regions 711a, 711b, and 711c is approximately half that of the first drawing mode, and the modeling temperature (e.g., 200°C) in the ON regions 711a, 711b, and 711c is lower than the modeling temperature (e.g., 220°C) in the first drawing mode. Therefore, in the second drawing mode, the temperature rise of the modeling material 91 in the OFF regions 712 and 713 (i.e., the difference between the solid line and the two-dot chain line in FIG. 10C ) is also smaller than in the first drawing mode. As a result, even in the OFF region 712 corresponding to the narrow non-drawing region 816, the temperature of the modeling material 91 is lower than its melting point (e.g., 185°C), preventing unintended melting of the modeling material 91 in the OFF region 712.

[0075] In the second drawing mode, after the first scanning of the multi-spot beam over the entire drawing target layer 92 of the modeling material 91 is completed, the second scanning of the multi-spot beam is performed. The time from the start of the first scanning of the multi-spot beam to the end of the scanning is, for example, several tens of seconds. Therefore, at the start of the second scanning of the multi-spot beam, the temperature of the drawing target layer 92 is generally lower than that shown in FIG. 10( c) and is close to the preheating temperature (e.g., 173°C). Furthermore, the second light intensity and second scanning speed are the same in the second scanning of the multi-spot beam as in the first scanning. Therefore, the amount of light imparted to each position of the drawing regions 815a to 815c in the second scanning is the same as the amount of light imparted to each position of the drawing regions 815a to 815c in the first scanning (see FIG. 10( b)). As a result, the temperature distribution of the drawing target layer 92 after the second scanning of the multi-spot beam is substantially the same as that shown in FIG. 10( c).

[0076] Therefore, in the second scan, as in the first scan, the temperature of the modeling material 91 is below the melting point (e.g., 185°C) in both the OFF region 712 corresponding to the narrow non-drawing region 816 and the OFF region 713 corresponding to the non-drawing region 817, preventing unintended melting of the modeling material 91. Therefore, as shown in Fig. 10(d), the narrow non-drawing region 816 exists between the drawing region 815a and the drawing region 815b, and the non-drawing region 817 exists between the drawing region 815b and the drawing region 815c. In other words, in the second drawing mode, the model 81 can be formed with high accuracy.

[0077] In the second drawing mode, the time required for the multi-spot beam to traverse the drawing target layer 92 once in the scanning direction is approximately half that of the first drawing mode, and the number of scans is twice that of the first drawing mode. Furthermore, the interval between the above-mentioned single traverse (hereinafter also referred to as "one pass movement") and the next single pass movement is very short. Therefore, the time required for pattern drawing on one drawing target layer 92 in the second drawing mode is approximately the same as the time required for pattern drawing on one drawing target layer 92 in the first drawing mode.

[0078] Experiments have confirmed that the strength of the model 81 formed in the second drawing mode is comparable to or even higher than that in the first drawing mode. As described above, in the drawing regions 815a-815c of the drawing target layer 92, the modeling material 91 irradiated with the multi-spot beams melts and its fluidity increases, and the voids present between the particles of the modeling material 91 are filled with the molten modeling material 91. However, while the fluidity of the modeling material 91 is high at temperatures above a predetermined temperature (e.g., its melting point), it is not very high below that temperature, even if it remains in a molten state. Furthermore, as described above, the temperature of the modeling material 91 melted by irradiation with the multi-spot beams drops relatively quickly. Therefore, the removal of the voids progresses significantly within a short time (e.g., 0.5 to 1 second) after irradiation with the multi-spot beams, but does not progress significantly thereafter. In the second drawing mode, when drawing a pattern on the drawing target layer 92, there are two time periods during which the removal of the voids progresses significantly, and therefore it is believed that the strength of the object 81 is higher than in the first drawing mode, in which such time period exists only once.

[0079] In the second drawing mode, other control different from the above example may be performed. For example, in the above example, the second light intensity and the second scanning speed are the same in the first and second scanning of the multi-spot beam in the second drawing mode, and the amount of light applied to each position in the drawing regions 815a to 815c is also the same, but this is not limiting.

[0080] In a first example of the other control, the amount of light imparted to each position in the drawing regions 815a-815c during the first scan is controlled to be greater than the amount of light imparted to each position in the drawing regions 815a-815c during the second scan. Specifically, for example, the second scanning speed during the first scan and the second scanning speed during the second scan are set to be the same, and the second light intensity during the first scan is set to be greater than the second light intensity during the second scan. The second light intensity during the first scan is set to, for example, 1.2 times the first light intensity during the first drawing mode, and the second light intensity during the second scan is set to, for example, 0.8 times the first light intensity. Furthermore, the second scanning speed during the first and second scans is, similar to the above, approximately twice the first scanning speed during the first drawing mode.

[0081] In this case, the amount of light imparted to each position in the drawing regions 815a-815c during the first scan in the second drawing mode is approximately 0.6 times the amount of light imparted to each position in the drawing regions 815a-815c in the first drawing mode. Furthermore, the amount of light imparted to each position in the drawing regions 815a-815c during the second scan in the second drawing mode is approximately 0.4 times the amount of light imparted to each position in the drawing regions 815a-815c in the first drawing mode. In this first example of other control, the total amount of light imparted to each position in the drawing regions 815a-815c in the second drawing mode (i.e., the sum of the amounts of light imparted over the two scans) is approximately the same as the amount of light imparted to each position in the drawing regions 815a-815c in the first drawing mode, but may be different.

[0082] In the second drawing mode, even if the light intensity applied to each position of the drawing regions 815a to 815c differs between the first and second scans, the object 81 can be formed with high precision, substantially similar to when the light intensity is the same between the first and second scans. Furthermore, as described above, by making the light intensity in the second scan smaller than that in the first scan, the temperature rise of the modeling material 91 due to the second scan of the multi-spot beam is smaller than that due to the first scan. Therefore, even if the second scan is performed after the first scan and before the temperature of the target layer 92 has sufficiently decreased, melting of the modeling material 91 in the narrow non-drawing region 816 during the second scan can be effectively prevented.

[0083] In a second example of the other control, the second scanning speed during the first and second scans in the second drawing mode is set to the same as the first scanning speed in the first drawing mode, and the second light intensity during the first and second scans in the second drawing mode is set to approximately half the first light intensity in the first drawing mode. In this case, the multi-spot beam scans the drawing target layer 92 twice with a light intensity profile substantially similar to the example shown in FIG. 10( b). As a result, unintended melting of the modeling material 91 is prevented even in the OFF region 712 corresponding to the narrow non-drawing region 816, substantially similar to the example shown in FIG. 10( d ).

[0084] In the second example of this other control, the multi-spot beam is scanned twice at each position in the drawing regions 815a-815c at a second scanning speed that is the same as the first scanning speed. Therefore, the total irradiation time of the light beam on each position in the drawing regions 815a-815c in the second drawing mode (i.e., the sum of the irradiation times of the light beam in the two scannings) is approximately twice the irradiation time of the light beam on each position in the drawing regions 815a-815c in the first drawing mode. Therefore, in the second drawing mode, the fluidity of the modeling material 91 is maintained at a high level for a longer period of time than in the first drawing mode, and as a result, the strength of the model 81 is higher than in the first drawing mode.

[0085] In a second example of this other control, the total amount of light applied to each position in the drawing areas 815a to 815c in the second drawing mode (i.e., the sum of the amount of light applied in two scans) is approximately the same as the amount of light applied to each position in the drawing areas 815a to 815c in the first drawing mode, but may be different.

[0086] In the second drawing mode illustrated in FIG. 10 , the second light intensity and / or the second scanning speed of the multi-spot beam may be adjusted based on the temperature distribution on the upper surface of the modeling material 91 (i.e., the temperature distribution of the modeling target layer 92) measured by the temperature measurement unit 4. For example, if the temperature distribution is measured before the first scan in the second drawing mode and the temperature of the modeling material 91 is higher than a predetermined temperature, the intensity control unit 503 controls the laser light source 21 and other components to adjust the second light intensity in the first scan to be slightly lower. In this case, instead of or in addition to adjusting the second light intensity, the scan control unit 502 may control the scanning unit 23 and other components to adjust the second scanning speed in the first scan to be slightly higher. Furthermore, if the temperature of the modeling material 91 is lower than a predetermined temperature, the second light intensity in the first scan may be adjusted to be slightly higher and / or the second scanning speed in the first scan may be adjusted to be slightly lower. The same applies to the second scan in the second drawing mode. The same applies to drawing in the first drawing mode, and also to the first and second examples of other control described above.

[0087] In the second drawing mode, the shape of the OFF region 712 of the light intensity profile shown in Fig. 10(b) may be corrected to resemble the OFF region 718 shown in Fig. 11(b). In the example shown in Fig. 11(b), the boundaries between the ON regions 717a and 717b corresponding to the drawing regions 815a and 815b and the OFF region 718 are tapered on both sides of the width of the OFF region 718 corresponding to the narrow non-drawing region 816. Specifically, the light intensity at the end of the ON region 717a closer to the OFF region 718 gradually decreases as the ON region 717a approaches the OFF region 718. Similarly, the light intensity at the end of the ON region 717b closer to the OFF region 718 gradually decreases as the ON region 717b approaches the OFF region 718. The width of the OFF region 718 (i.e., the width of the region in FIG. 11B where the light amount does not fluctuate significantly near 0) is approximately the same as the width of the OFF region 712 shown in FIG. 10B (i.e., the width of the narrow non-writing region 816 in the design pattern). Note that the width of the OFF region 718 may be larger or smaller than the width of the OFF region 712.

[0088] This suppresses the irradiation of the light beam to a region of the imaging regions 815a and 815b that is close to the narrow non-imaging region 816 (hereinafter also referred to as the "narrow-portion-adjacent region"). In other words, the amount of light per unit area imparted to the narrow-portion-adjacent region is reduced compared to the amount of light per unit area imparted to a region of the imaging regions 815a and 815b excluding the narrow-portion-adjacent region. As a result, in the OFF region 718 corresponding to the narrow non-imaging region 816, the accumulation of the amount of light at the ends of the ON regions 717a and 717b adjacent to both sides in the width direction is suppressed. Furthermore, overlapping of heat diffused from the ON regions 717a and 717b in the OFF region 718 is also suppressed.

[0089] Therefore, as shown by the solid line in Fig. 11(c), the temperature of the modeling material 91 in the OFF region 718 rises somewhat above the preheating temperature (e.g., 173°C). However, even after thermal diffusion from the ON regions 717a and 717b occurs over time, the temperature does not rise to the melting point of the modeling material 91 (e.g., 185°C) as shown by the two-dot chain line. Furthermore, the temperature of the modeling material 91 in the OFF region 718 shown by the two-dot chain line in Fig. 11(c) is lower than the temperature of the modeling material 91 in the OFF region 712 shown by the two-dot chain line in Fig. 10(c). Therefore, unintended melting of the modeling material 91 in the OFF region 718 is effectively prevented.

[0090] The correction of the light intensity profile shown in Figure 11 (b) is achieved, for example, by making the light intensity of the light spots corresponding to the narrow portion adjacent regions of the drawing regions 815a and 815b, among the multiple light spots of the multi-spot beam, smaller than the light intensity of the light spots corresponding to regions other than the narrow portion adjacent regions of the drawing regions 815a and 815b.

[0091] In the three-dimensional modeling apparatus 1, the number of scans of the multi-spot beam on each position in the drawing regions 815a to 815c in the second drawing mode may be any number of times, and is not limited to two. Even if the number of scans is three or more, substantially similar to the above example in which the number of scans is two, if the second light intensity in the second drawing mode is the same as the first light intensity in the first drawing mode, the second scanning speed in the second drawing mode is controlled to be greater than the first scanning speed in the first drawing mode. Furthermore, if the second scanning speed in the second drawing mode is the same as the first scanning speed in the first drawing mode, the second light intensity in the second drawing mode is controlled to be smaller than the first light intensity in the first drawing mode.

[0092] As described above, the three-dimensional modeling apparatus 1 includes the material holding unit 3, the optical head 2, and the control unit 5. The material holding unit 3 includes a stage 341 that holds a powdered modeling material 91, and a material supply unit 32 that supplies the modeling material 91 onto the stage 341. The optical head 2 modulates and scans the modeling material 91 held on the stage 341. The control unit 5 controls the material holding unit 3 and the optical head 2 based on design data of the model 81, thereby supplying the modeling material 91 onto the stage 341, scanning the light beam over the drawing target layer 92, which is the surface layer of the supplied modeling material 91, and melting the modeling material 91 in the area irradiated with the light to draw a pattern.

[0093] The control by the control unit 5 can be switched between a first drawing mode and a second drawing mode. In the first drawing mode, the light beam is scanned only once at each position of the drawing regions 815a to 815c designated for drawing by the design data on the drawing target layer 92. In the second drawing mode, the light beam is scanned multiple times at each position of the drawing regions 815a to 815c, with the amount of light applied to each position of the drawing regions 815a to 815c per scan being smaller than in the first drawing mode.

[0094] As described above, by performing pattern drawing in the second drawing mode, the three-dimensional printing device 1 can prevent unintended melting of the modeling material 91 in the non-drawing regions 816 and 817 where drawing is not instructed in the design data. As a result, the model 81 can be formed with high precision. The strength of the model 81 can also be increased. On the other hand, by performing pattern drawing in the first drawing mode, the drawing operation of the three-dimensional printing device 1 can be simplified.

[0095] As described above, in the three-dimensional printing apparatus 1, when the non-drawing regions 816, 817 for which drawing is not instructed in the design data include a narrow non-drawing region 816 having a width equal to or smaller than a predetermined threshold (i.e., narrow threshold), it is preferable that the second drawing mode be selected by the control unit 5. As a result, when the design data includes the narrow non-drawing region 816, the second drawing mode is automatically selected, and the model 81 can be formed with high precision.

[0096] As described above, it is preferable that the light intensity of the light beam in the second drawing mode (i.e., the second light intensity) is the same as the light intensity of the light beam in the first drawing mode (i.e., the first light intensity), and that the scanning speed of the light beam in the second drawing mode (i.e., the second scanning speed) is greater than the scanning speed of the light beam in the first drawing mode (i.e., the first scanning speed). This makes it possible to accurately form the object 81 in the second drawing mode while making the time required to draw a pattern on one drawing target layer 92 (hereinafter also referred to as the "layer drawing time") approximately the same as the layer drawing time in the first drawing mode. Furthermore, even if the layer drawing time in the second drawing mode is longer than the layer drawing time in the first drawing mode, the amount of increase can be suppressed. That is, the object 81 can be accurately and quickly formed in the second drawing mode.

[0097] More preferably, in the second drawing mode, the number of times the light beam scans each position in the drawing regions 815a to 815c is two, and the scanning speed of the light beam in the second drawing mode (i.e., the second scanning speed) is twice the scanning speed of the light beam in the first drawing mode (i.e., the first scanning speed). This makes it possible to easily achieve the second drawing mode with a realistic device configuration without requiring excessive performance from the scanning unit 23, etc.

[0098] As described above, it is also preferable that the scanning speed of the light beam in the second drawing mode (i.e., the second scanning speed) is the same as the scanning speed of the light beam in the first drawing mode (i.e., the first scanning speed), and that the light intensity of the light beam in the second drawing mode (i.e., the second light intensity) is smaller than the light intensity of the light beam in the first drawing mode (i.e., the first light intensity). This makes it possible to form the object 81 with high accuracy in the second drawing mode while further increasing the strength of the object 81.

[0099] As described above, in the second drawing mode, the light beam scans each position in the drawing regions 815a-815c twice, and the amount of light imparted to each position in the drawing regions 815a-815c during the first light beam scan in the second drawing mode is preferably the same as the amount of light imparted to each position in the drawing regions 815a-815c during the second light beam scan in the second drawing mode. This improves uniformity of temperature changes and the like in the modeling material 91 during the first and second light beam scans in the second drawing mode. Furthermore, by making the second light intensity and second scanning speed the same during the first and second light beam scans in the second drawing mode, control of the optical head 2 in the second drawing mode can be simplified.

[0100] As described above, the number of times the light beam scans each position in the drawing regions 815a to 815c in the second drawing mode is two, and it is also preferable that the amount of light imparted to each position in the drawing regions 815a to 815c in the first scanning of the light beam in the second drawing mode is greater than the amount of light imparted to each position in the drawing regions 815a to 815c in the second scanning of the light beam in the second drawing mode. As a result, the amount of light imparted to the narrow non-drawing region 816, whose temperature has been raised by the first scanning, in the second scanning is reduced compared to the first scanning. As a result, unintended melting of the modeling material in the narrow non-drawing region 816 can be further suppressed.

[0101] As described above, the light beam is a multi-spot beam composed of a plurality of light spots linearly arranged in a predetermined arrangement direction, and the multi-spot beam is preferably scanned in a predetermined scanning direction inclined with respect to the arrangement direction. This reduces the time required to draw a pattern on the drawing target layer 92. Furthermore, as described above, the three-dimensional printing apparatus 1 can accurately form the model 81 even when the design data includes a narrow non-drawing region. Therefore, the three-dimensional printing apparatus 1 is particularly suitable for drawing using a multi-spot line beam, in which the light beam may be irradiated simultaneously onto drawing regions on both sides of a narrow non-drawing region.

[0102] As described above, the three-dimensional modeling apparatus 1 preferably further includes a temperature measurement unit 4 that measures the temperature distribution on the upper surface of the modeling material 91 on the stage 341. Furthermore, the control unit 5 preferably adjusts the light intensity or scanning speed of the light beam in the second drawing mode (i.e., the second light intensity or the second scanning speed) based on the temperature distribution measured by the temperature measurement unit 4. This allows the model 81 to be formed with even greater precision, as described above.

[0103] As described above, it is preferable that the modeling material 91 is a resin material. As described above, the three-dimensional modeling apparatus 1 can accurately form the modeling material 91 even when the heat in the image-drawing region does not dissipate quickly and the temperature of the non-image-drawing region is relatively likely to rise. Therefore, the three-dimensional modeling apparatus 1 is particularly suitable for three-dimensional modeling using a resin material, which has lower heat dissipation properties than a metal material.

[0104] The above-described three-dimensional modeling apparatus 1 can be modified in various ways.

[0105] For example, it is not necessary to adjust the second light intensity and the second scanning speed based on the temperature distribution of the drawing target layer 92 measured by the temperature measurement unit 4. In this case, the temperature measurement unit 4 may be omitted.

[0106] In each multi-spot beam scan in the second drawing mode, both the second light intensity and the second scanning speed may be changed from the first light intensity and the first scanning speed in the first drawing mode. Also, in the second drawing mode, among multiple multi-spot beam scans, both the second light intensity and the second scanning speed in one scan may be different from the second light intensity and the second scanning speed in the other scans.

[0107] The switching between the first drawing mode and the second drawing mode does not necessarily have to be performed automatically by the control unit 5, but the first drawing mode or the second drawing mode may be selected by the operator making a predetermined input via the input unit 56 or the like.

[0108] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0109] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention.

[0110] REFERENCE SIGNS LIST 1 Three-dimensional modeling device 2 Optical head 3 Material holding unit 4 Temperature measurement unit 5 Control unit 32 Material supply unit 81 Modeled object 91 Modeling material 92 Layer to be imaged 341 Stage 815, 815a, 815b, 815c Imaged area 816 (narrow) non-imaged area 817 Non-imaged area

Claims

1. A three-dimensional modeling device comprising: a material holding unit having a stage for holding a powdered modeling material and a material supply unit for supplying the modeling material onto the stage; an optical head for scanning a light beam while modulating the modeling material held on the stage; and a control unit for controlling the material holding unit and the optical head based on design data for a model, thereby supplying the modeling material onto the stage, and scanning the light beam on a drawing target layer, which is the surface layer of the supplied modeling material, to melt the modeling material in the area irradiated with the light and draw a pattern, repeatedly, wherein the control by the control unit is switchable between a first drawing mode in which the light beam is scanned only once for each position of a drawing area instructed to be drawn by the design data on the drawing target layer, and a second drawing mode in which the light beam is scanned multiple times for each position of the drawing area, with the amount of light applied to each position of the drawing area in one scan of the light beam being smaller than in the first drawing mode.

2. A three-dimensional printing device as described in claim 1, wherein the control unit selects the second drawing mode when a non-drawing area for which drawing is not instructed in the design data includes a narrow non-drawing area having a width equal to or less than a predetermined threshold value.

3. A three-dimensional modeling device as described in claim 1 or 2, wherein the light intensity of the light beam in the second drawing mode is the same as the light intensity of the light beam in the first drawing mode, and the scanning speed of the light beam in the second drawing mode is faster than the scanning speed of the light beam in the first drawing mode.

4. A three-dimensional modeling device as described in claim 3, wherein the number of scans of the light beam for each position in the drawing area in the second drawing mode is two, and the scanning speed of the light beam in the second drawing mode is twice the scanning speed of the light beam in the first drawing mode.

5. A three-dimensional modeling device according to claim 1 or 2, wherein the scanning speed of the light beam in the second drawing mode is the same as the scanning speed of the light beam in the first drawing mode, and the light intensity of the light beam in the second drawing mode is smaller than the light intensity of the light beam in the first drawing mode.

6. A three-dimensional modeling device as described in claim 1 or 2, wherein the number of scans of the light beam to each position of the drawing area in the second drawing mode is two, and the amount of light imparted to each position of the drawing area in the first scan of the light beam in the second drawing mode is the same as the amount of light imparted to each position of the drawing area in the second scan of the light beam in the second drawing mode.

7. A three-dimensional modeling device as described in claim 1 or 2, wherein the number of scans of the light beam to each position of the drawing area in the second drawing mode is two, and the amount of light imparted to each position of the drawing area by the first scan of the light beam in the second drawing mode is greater than the amount of light imparted to each position of the drawing area by the second scan of the light beam in the second drawing mode.

8. A three-dimensional modeling apparatus according to claim 1 or 2, wherein the light beam is a multi-spot beam composed of a plurality of light spots arranged in a line in a predetermined arrangement direction, and the multi-spot beam is scanned in a predetermined scanning direction that is inclined with respect to the arrangement direction.

9. A three-dimensional modeling apparatus as described in claim 1 or 2, further comprising a temperature measuring unit that measures a temperature distribution on the upper surface of the modeling material on the stage, and the control unit adjusts the light intensity or scanning speed of the light beam in the second drawing mode based on the temperature distribution measured by the temperature measuring unit.

10. A three-dimensional modeling apparatus according to claim 1 or 2, wherein the modeling material is a resin material.

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