Additive manufacturing apparatus

An additive manufacturing apparatus in which a streak in a manufacturing direction is difficult to be made on the surface of a product manufactured object in a boundary region of projection regions of exposure images is provided. In this apparatus, a vessel holds a photosetting liquid resin material, a first projector makes a first exposure image incident from an incident surface and projects it into the resin material, a second projector makes a second exposure image, continuous with the first exposure image, incident from the incident surface and projects it into the resin material, and a controlling unit adjusts on a projection surface a boundary region between a first projection image obtained by projecting the first exposure image by the first projector and a second projection image obtained by projecting the second exposure image by the second projector.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an additive (three-dimensional) manufacturing apparatus which manufactures a three-dimensional manufactured (modeled) object by projecting an exposure image into a photosetting (photocurable) liquid resin material.

Description of the Related Art

In recent years, an additive manufacturing apparatus for manufacturing a three-dimensional manufactured object by laminating solidified layers formed by exposing a photosetting liquid resin material is being developed. In the additive manufacturing apparatus in which the solidified layer formed by exposing the surface layer of the resin material is moved downward and laminated, there is a problem that a manufacturing speed in a laminating direction is low (U.S. Patent Application Publication No. 2015/54198).

On the other hand, in U.S. Pat. No. 9,216,546, there is proposed an additive manufacturing apparatus which can manufacture at a relatively high speed a three-dimensional manufactured object by pulling up a solidified layer solidified by an exposure image while projecting the exposure image for solidifying a resin material into the resin material through a bottom surface of a vessel.

The additive manufacturing apparatus which projects the exposure image into the resin material comprises an image projecting unit (so-called a projector) for projecting the exposure image formed by an image forming element into the resin material by using a projection optical system. In the additive manufacturing apparatus like this, a range of the cross section perpendicular to a manufacturing direction of the product manufactured object is limited to an area where the exposure image can be projected by the projection optical system.

Here, if a projection magnification of the projection optical system is increased, the manufacturing area is also increased. However, in this case, since a pixel of the projection image is enlarged, manufacturing resolution of the product manufactured object is lowered. If it is attempted to enlarge the manufacturing area without increasing the projection magnification of the projection optical system, a large-sized and high-definition image forming element and a large-aperture projection optical system are required, so that a manufacturing cost of the additive manufacturing apparatus is increased.

In view of this, it has been proposed to arrange a plurality of image projecting units so as to face the bottom surface of the vessel, and to join respective projection regions of the image projecting units to secure a large manufacturing area. However, in a case where additive (three-dimensional) manufacture is performed using the plurality of image projecting units by dividing the exposure image of the product manufactured object, it turns out that, in a boundary region of the projection images of the adjacent image projecting units, a streak pattern and/or a slit are/is made in the manufacturing direction on the surface of the product manufactured object.

It is an object of the present invention to provide an additive manufacturing apparatus in which a streak pattern and/or a slit in a manufacturing direction are/is difficult to be made on the surface of a product manufactured object in a boundary region of projection regions of exposure images.

SUMMARY OF THE INVENTION

An additive manufacturing apparatus according to the present invention is characterized by comprising: a vessel configured to hold a photosetting liquid resin material and have an incident surface through which an exposure image for solidifying the resin material is incident into the resin material; a first image projecting unit configured to make a first exposure image incident from the incident surface and project the incident first exposure image into the resin material; a second image projecting unit configured to make a second exposure image, continuous with the first exposure image, incident from the incident surface and exposure the incident second exposure image into the resin material; a moving unit configured to move a manufacturing layer manufactured by solidifying the resin material by the first exposure image and the second exposure image, away from the incident surface; and a controlling unit configured to adjust a boundary region between a first projection image obtained by projecting the first exposure image into the resin material by the first image projecting unit and a second projection image obtained by projecting the second exposure image into the resin material by the second image projecting unit.

DESCRIPTION OF THE EMBODIMENTS

As illustrated inFIG. 1, in Embodiment 1, a manufacturing area of 500 mm×500 mm is secured by using 5 projectors×5 projectors. Then, a boundary region of adjacent projection regions is photographed by a camera130, and an overlap of the projection regions in the boundary region is mechanically adjusted based on a photographed image.

FIG. 1is an explanatory diagram for describing a constitution of an additive manufacturing apparatus according to Embodiment 1.FIG. 2is an explanatory diagram for describing a constitution of a projector. As illustrated inFIG. 1, an additive manufacturing apparatus100projects an exposure image into a resin material in a vessel11by using 5×5 projectors20, thereby manufacturing a product manufactured object30which is as an example of an additive manufacture.

As illustrated inFIG. 2, the vessel11serving as an example of a vessel holds a photosetting liquid resin material10, and has an incident surface through which the exposure image is incident into the resin material. The vessel11has a transmitting portion11awhich is an opening for projecting the exposure image into the vessel. A transmitting member12is attached to the transmitting portion11ato hold the photosetting liquid resin material10so as not to leak.

A pull-up member13and a pull-up device17, which are examples of a moving unit, move a manufacturing layer manufactured by solidifying the resin material by projectors20aand20baway from an incident surface12a. The pull-up member13is pulled upward at an arbitrarily set speed or an arbitrarily set pitch and time interval by the pull-up device17operated by a pulse motor and a ball screw. The pull-up member13is made by a material that the cured resin material10can be attached to and separated from, and has a surface shape from which the resin material can easily be separated.

The projector20projects an exposure image RG formed on the surface of an image forming element23into the resin material10in the vessel11. The exposure image RG is formed at an image forming position28. The projector20a, which is an example of a first image projecting unit, makes a first exposure image (RGa:FIG. 6) incident from the incident surface12aand projects the incident image into the resin material. The projector20bis an example of a second image projecting unit, makes a second exposure image (RGb:FIG. 6), which is continuous with the first exposure image, incident from the incident surface12a, and projects the incident image into the resin material10. As described later, the projector20acan move in a plane, adjust a projection magnification and adjust a focal position, by an individual remote operation.

The image forming element23forms the exposure image which is illuminated by a light source21being an example of an illuminating unit. The light source21generates ultraviolet rays by an ultraviolet LED (light-emitting diode) and illuminates the image forming element23with the generated ultraviolet rays. A projection optical system25projects the exposure image formed by the image forming element23into the resin material10through the incident surface12a.

The image forming element23is a light modulating element for forming an image corresponding to image data on its surface. The image forming element23is formed by arranging minute movable mirrors corresponding to respective pixels in a lattice pattern, and outputs a reflected image of illumination light by the light source21. The image forming element23adopts a DMD (digital mirror device) element of DLP9000™ from Texas Instruments Incorporated, in consideration of high efficiency of utilization of ultraviolet light.

The projection optical system25projects a binary image formed on the surface of the image forming element23so as to be imaged at the image forming position28which is a conjugate position with the exposure image RG on a projection optical path of the exposure image. A projection magnification of the projection optical system25is 10 times, and this system magnifies and displays one pixel of 7.6 μm square formed on the image forming element23to a pixel of 76 μm square projected on the projection image.

A mirror of each pixel of the image forming element23may be simply turned ON/OFF in synchronization with switching of the exposure image RG. However, a brightness gradation (intensity modulation amount) may be set for each pixel constituting the exposure image. The image forming element23can turn ON/OFF (change a reflection angle) of the mirror of each pixel 250 times per second within the range of a duty ratio of 0% to 100%. It is also possible to output halftone (gray scale) of the pixel by individually setting the duty ratio of ON to the mirror of each pixel.

The transmitting member12is a fluororesin material which has a property of transmitting oxygen and ultraviolet light and has a substantially transparent appearance with a thickness of 2 mm. More specifically, Teflon™ AF 2400 from DuPont-Mitsui Fluoroproducts Co., Ltd. is used, and a transmissivity of the light source21to ultraviolet light is 88%.

The transmitting member12transmits oxygen in the air and forms an oxygen-rich atmosphere at the interface with the resin material10, thereby preventing a radical polymerization reaction due to ultraviolet rays of the resin material10. Thus, a thin liquid layer (so-called a dead zone)31of the resin material10is formed between the product manufactured object30and the transmitting member12, and the product manufactured object30is pulled upward without attachment to the transmitting member12.

That is, the resin material10which is used in Embodiment 1 is the resin material which undergoes the radical polymerization reaction by ultraviolet light and solidifies, and which prevents from undergoing the radical polymerization reaction in an oxygen-rich environment. For example, a photosetting polyurethane, a photosetting epoxy resin, a photosetting urethane, a photosetting silicone rubber or the like is used.

A controlling unit110is a computer which holds, in a RAM (random access memory)112, a processing program and data recorded in a ROM (read-only memory)113, and performs calculation and process necessary for a CPU (central processing unit)111. The controlling unit110is an additive manufacturing controller which operates the additive manufacturing apparatus100by executing a manufacturing process program generated by an external computer122.

The controlling unit110continuously or intermittently pulls up by the pull-up device17the pull-up member13at a speed linked to a reproduction speed of a moving image, while outputting to the image forming element23the moving image obtained by arranging images of the respective layers of the product manufactured object30in time series. Thus, the product manufactured object30of which the upper end is fixed to the pull-up member13is three-dimensionally manufactured so as to grow upward.

FIG. 3is a flowchart for describing creation of a manufacturing process program. As illustrated inFIG. 2, an external computer121inputs design data of the product manufactured object30to the controlling unit110, and instructs the controlling unit110to start, interrupt and the like of the manufacture of the product manufactured object30. The controlling unit110has installed software for automatically creating a manufacturing program of the product manufactured object30based on the design data of the product manufactured object30.

As illustrated inFIG. 3, the CPU111obtains the design data (CAD (computer-aided design) data) of the product manufactured object30from the external computer121(S11). Based on the design data of the product manufactured object30, the CPU111sets a manufacturing region of the product manufactured object30per predetermined height, and divides it into manufacturing regions of the respective projectors20(S12).

The CPU111sets an exposure image of the photosetting resin material for each manufacturing region of each projector20per predetermined height (S13). The CPU111sets a switching interval (i.e., moving image reproducing speed) of the exposure image of the image forming element23and a pull-up plan of the pull-up member13by the pull-up device17(S14). The CPU111combines the switching plan of the exposure image of the image forming element23and the pull-up plan of the pull-up member13with each other to create the manufacturing process program of the product manufactured object30, and stores the created program in the RAM112(S15). The manufacturing process program and attached data are transmitted to the external computer121and stored in a recording medium.

Incidentally, the process of dividing the projection image according to the projection region (TR:FIG. 6) for each projector20may be performed by the external computer121.

As illustrated inFIG. 2, the projector20projects the exposure image formed by the image forming element23into the resin material10by the projection optical system25. In a case where the number of the projectors20is one, an area of the cross section perpendicular to the manufacturing direction of the product manufactured object30is a manufacturing area that the projection optical system25can project the exposure image.

As the projection magnification of the projection optical system25increases, the manufacturing area increases. However, in this case, since the pixel of the projection image increases, manufacturing resolution of the product manufactured object30decreases. In order to enlarge the manufacturing area without increasing the projection magnification of the projection optical system25, a large-sized high-definition image forming element23and a large-aperture projection optical system25corresponding to the large manufacturing area are required, thereby greatly increasing a manufacturing cost of the additive manufacturing apparatus100.

Therefore, in the additive manufacturing apparatus100, as illustrated inFIG. 1, the 25 projectors20of 5 units×5 units are arranged in a lattice shape so as to face the bottom surface of the vessel11, and the 25 projection regions are joined together in a lattice shape, thereby securing the large manufacturing area. However, when the 25-divided exposure images are simply projected by the 25 projectors20to perform the additive manufacture, a streak pattern and/or a slit in the manufacturing direction are/is made (manufactured) at the position of the product manufactured object30corresponding to the boundary region of the divided projection images.

Therefore, in Embodiment 1, the boundary region of the divided projection images is photographed by the camera130, and the position adjustment of the individual image forming element23is performed based on the photographed image. Thus, the boundary region of the adjacent projection images obtained by projecting the divided exposure images is adjusted to reduce a shift (deviation) between the pixels of the adjacent projection images.

That is, if an enlargement magnification of the projection optical system25is increased in order to form the large product manufactured object30, the resolution of the manufactured object inevitably decreases. Therefore, in order to form the large-sized and high-resolution product manufactured object30, it is necessary to use the plurality of projection optical systems25and to join the respective projection images together for the manufacture. However, when the manufacture is performed by joining together the respective projection images of the plurality of projection optical systems25, there is a case where the projection images are not smoothly connected due to a shift of the projection image at the boundary between the adjacent projection images, a difference in an exposure amount, or the like. In a case where the projection images are not smoothly connected, steps, streaks, slits or the like which are not present in the design data (three-dimensional structure data) of the product manufactured object30are made in the portion of the product manufactured object30corresponding to the boundary of the projection images, so that shape accuracy decreases. Therefore, in order to make a joint of the projection image TG on the projection surface TM (=manufacturing surface) invisible, it is necessary to correct the positional shift between the adjacent projection images and make a light amount distribution uniform.

In case of projecting the individual exposure image RG obtained by dividing the whole exposure image by the plurality of projectors20, when there is a positional shift of an image pattern on the boundary between adjacent projection images TG, three causes, i.e., (1) the position to which the image is to be projected is shifted, (2) a difference in magnification of the image occurs, and (3) the image itself is distorted, are conceivable. In Embodiment 1, it aims to reduce the cause (1) the shift of the position to which the image is to be projected. Accordingly, the cause (2) the difference in magnification of the image and the cause (3) the distortion of the image itself will be described later.

As illustrated inFIG. 6with reference toFIG. 2, the camera130, which is an example of an image information obtaining unit, is provided between the adjacent projection optical systems25to obtain a photographed image of a boundary region KR of the projection image TG. In Embodiment 1, a positional shift amount of the exposure image RG for each projector20is measured based on the photographed image obtained by the camera130. In Embodiment 1, a positioning image IG, which is an example of a positioning mark provided outside the manufacturing region of a projection surface TM, is used during actual exposure. The positioning image IG projected onto the interface between the resin material10and the transmitting member12is photographed and imaged by the camera130, thereby obtaining imaging data. The transmitting member12is a window into which the projection image from the projection optical system25is incident, and which has a refractive index different from that of the resin material (monomer material)10in the vessel11.

FIGS. 4A to 4Care explanatory diagrams for describing an aligning mechanism of the image forming element23. More specifically,FIG. 4Ais the side view,FIG. 4Bis the plan view andFIG. 4Cis the front view of the aligning mechanism. As illustrated inFIGS. 4A to 4C, an image displaying unit40movably holds the image forming element23by actuators41to48and51to53using piezoelectric elements, inside a box-shaped casing40fEach of the actuators41to48and51to53expands and contracts in accordance with an applied DC (direct current) voltage.

The actuators41to48, which are examples of an adjusting unit, are capable of adjusting the position of the image forming element23in a plane intersecting the projection optical axis of the exposure image. The controlling unit110can adjust a relative position in the boundary region KR between the two adjacent projection images TG, by controlling the actuators41to48. The actuators41,42,43and44can move the image forming element23in a Y direction by properly combining the expansions and the contractions of the respective actuators. Besides, the actuators45,46,47and48can move the image forming element23in an X direction by properly combining the expansions and the contractions of the respective actuators. Besides, the actuators41,42,43,44,45,46,47and48can perform angle adjustment by rotating the image forming element23in an XZ plane by properly combining the expansions and the contractions of the respective actuators.

The actuators51,52and53can move the image forming element23in a Z direction by integrally expanding and contracting. Besides, the actuators51,52and53can perform angle adjustment of the image forming element23in the XZ plane and in an YZ plane by properly combining the expansions and the contractions of the respective actuators.

The controlling unit (110;FIG. 2), which is an example of a controlling unit, calculates a shift amount of the pixels in the adjacent two projection images by processing the photographed images photographed by the camera130, and operates the actuators41to48so as to cancel the calculated shift amount.

FIG. 5is a schematic diagram for describing the projection region of the projector, andFIG. 6is an explanatory diagram for describing the boundary region of the projection image. As illustrated inFIG. 2, the camera130, which is an example of a photographing unit, photographs the boundary region KR from the outside of the vessel11. The controlling unit110adjusts the boundary region (KR:FIG. 6) between a first projection image (TGa:FIG. 6) obtained by projecting the first exposure image (RGa:FIG. 6) by the projector20aand a second projection image (TGb:FIG. 6) obtained by projecting the second exposure image by the projector20b.

The four adjacent projectors20, which are taken out from the additive manufacturing apparatus100illustrated inFIG. 1, will be explained hereinafter. As illustrated inFIG. 5, the four projectors20respectively project the quadrupled exposure images RG to form the projection images TG at the image forming position28. The projection image TG is set inside the projection region TR of the projector20.

As illustrated inFIG. 6, the projection regions TR of the four projectors20overlap at the boundary region KR. The adjacent projection images TG are joined together such that each image includes the half of the boundary region KR. The controlling unit (110:FIG. 2) adjusts the positions, inclination angles, illuminances and the like of the adjacent projection images TG in the boundary region KR, based on the photographed image of the boundary region KR by the camera130. Although the width of the boundary region KR is exaggerated inFIG. 6, actually, this region is merely an overlap of about 10 pixels (0.75 mm).

The camera130is disposed to face the boundary region KR of the adjacent projection regions TR and to be able to set the two positioning images IG projected on the projection region TR in an angle of view. The camera130photographs the positioning image IG when adjusting the position of the projection region before the start of the manufacture, and, after starting the manufacture, photographs an image obtained by projecting the exposure image RG of the product manufactured object30onto the projection region TR.

The camera130is used for projection image measurement. The camera130obtains the image data of the projection image TG at a sampling rate which is twice or more a frame rate of the image forming element27, in synchronization with the frame rate of an image forming element27. The camera130obtains position information and illuminance information of the image pattern of the projection image TG located in the boundary region KR.

In Embodiment 1, the camera130has an imaging element sensitive to ultraviolet light, and photographs the interface between the resin material10and the transmitting member12and an image of reflected light based on a refractive index difference of ultraviolet light in the product manufactured object30. However, it is also possible to use the camera130which has an imaging element sensitive to visible light. For this purpose, as described later, the light source21is temporarily switched to a visible light source at photographing timing, or visible light is overlapped on ultraviolet light. Besides, it is possible to convert ultraviolet light into visible light by mixing a fluorescent agent with the resin material, so that the projection image TG can be observed with visible light. As described later, it is possible by remotely operating the camera130individually to adjust the position in a planar direction, and adjust a focal position.

As illustrated inFIG. 4B, by moving the image forming element23in an XY plane, the projection image TG moves within the plane of the image forming position28. By inclining the image forming element23in the XY plane, the inclination angle of the projection image TG is adjusted within the plane of the image forming position28. As illustrated inFIG. 2, the CPU111divides the entire projection image of each layer to be formed, which is created from the design data of the product manufactured object30, into the projection image TG of each projector20. The CPU111prepares a large number of photographed images (so-called FLIP BOOK) grouped in time series for each projector20to which the divided exposure image is allocated, and waits for start of manufacture.

Here, in a modification of Embodiment 1, the camera130sensitive to an infrared light region is used in place of the camera130sensitive to the ultraviolet region. Generally, since the radical polymerization reaction of a resin monomer is a considerable exothermic reaction, the manufacturing region of the product manufactured object30in which solidification of the resin material is progressing in the projection image TG is an infrared ray source. By performing focusing and photographing of the image forming position28using the camera130sensitive to the infrared light region, an image having a manufacturing contour of the high-contrast product manufactured object30in which the illuminance of the manufacturing region is emphasized with respect to a non-manufacturing region is obtained. Thus, it is possible to detect a shift and a gap of the adjacent projection images TG in the boundary region KR with high resolution.

FIG. 7is a flowchart for describing shift (deviation) correction control of the projection image according to Embodiment 1.FIGS. 8A and 8Bare explanatory diagrams for describing the movement of the projection region. More specifically,FIG. 8Ashows the projection region before the correction, andFIG. 8Bshows the projection region after the correction. The CPU111photographs the boundary region KR by the camera130by performing a photographing process during the manufacture of the product manufactured object30. In an adjusting step following the photographing step, the CPU111adjusts the alignment of the boundary region KR by photographing the boundary region KR during the manufacture of the product manufactured object30.

As illustrated inFIG. 7, when it is instructed to start the manufacture from the external computer121, the CPU111starts the shift correction control of the projection image TG. The CPU111displays a positioning mark on the image forming element23, and forms the positioning image IG at the image forming position28as illustrated inFIG. 6. Then, the camera130photographs the positioning image IG and captures the photographed image (S21).

Incidentally, although the positioning image IG solidifies the resin material10on the pull-up member13, it does not become a problem because it is before the manufacture of the product manufactured object30. However, as for the positioning image IG, it is possible to avoid an unnecessary polymerization reaction of the resin material10by lowering the brightness gradation (ON duty) of the pixel in the image forming element23and finishing the process in a short time.

The CPU111processes the photographed image of the positioning image IG, and calculates a positional shift correction amount and an inclination correction amount of the individual projection region TR (S22). The CPU111causes the actuators41to48to operate to correct the positional shift and the inclination of the individual projection region TR (S23). After correcting the positional shift and the inclination of the projection region TR, the CPU111starts the manufacture (S24).

As illustrated inFIG. 8A, after the start of the manufacture, an image process of comparing the photographed image with the exposure image in the boundary region is performed, so that a rupture (breakage) in the boundary region KR of a product projection image30G, in which the exposure image of the product manufactured object30is projected onto the projection region TR, is detected. Then, when the rupture is detected, the actuators41to48are operated to adjust the position of the projection region as indicated by white arrows inFIG. 8B.

After the start of the manufacture, at a photographing timing of each predetermined time (1 second) (YES in S26), the CPU111photographs, by using the camera130, the projection image of the exposure image projected onto the boundary region KR, and captures the photographed image (S27).

The CPU111compares the photographed product projection image30G with the exposure image RG projected onto the boundary region KR to decide whether or not a gap GP is generated in the product projection image30G. When the gap GP is generated, the CPU obtains the number of pixels in the gap GP and the number of positional shift pixels in a direction along the gap, and calculates the positional shift correction amount and the inclination correction amount of the projection region TR (S28).

The CPU111operates the actuators41to48to correct the positional shift and the inclination of the projection region TR (S29). When the manufacture of the product manufactured object30ends (YES in S25), the CPU111ends the shift correction control of the projection image TG.

Effect of Embodiment 1

As illustrated inFIG. 6, in Embodiment 1, the boundary region KR between the first projection image TGa on which the first exposure image RGa is projected and the second projection image TGb on which the second exposure image RGb is projected is adjusted. Therefore, it is possible to reduce a streak pattern, a swelling, a dent, a deformation, a slit and the like which are made in the product manufactured object30and continuous in the manufacturing direction.

In Embodiment 1, the camera130photographs the boundary region KR from the outside of the vessel11. Then, based on the photographed image of the boundary region KR by the camera130, a relative position, an inclination angle, an illuminance and the like of the two adjacent projection images TG in the boundary region KR are adjusted. Therefore, it is possible to start the control to correctly decide and eliminate the streak pattern and/or the slit in the manufacturing direction to be formed on the product manufactured object30at an early stage. Further, it is possible to simply constitute the photographing optical system of the camera130.

In Embodiment 1, the position of the image forming element23can be adjusted within the plane where the actuators41to48cross the projection optical axis of the exposure image. Therefore, the controlling unit110can move the projection image TG of the exposure image RG along the projection surface TM and perform the positioning of the two adjacent exposure images RGa and RGb.

In Embodiment 1, the position and the inclination of the image forming element23are mechanically adjusted, and the boundary region of the adjacent projection regions is adjusted. On the other hand, in Embodiment 2, the image forming element23is not moved, but the position of the product manufactured object30on the exposure image on the image forming element23is corrected. Incidentally, since the mechanical constitution and the manufacturing process of the additive manufacturing apparatus100are the same as those in Embodiment 1, duplicate explanations are omitted.

As described above, in case of projecting the individual exposure image RG obtained by dividing the whole exposure image by the plurality of projectors20, when there is the positional shift of the image pattern on the boundary between the adjacent projection images TG, the three causes, i.e., (1) the position to which the image is to be projected is shifted, (2) the difference in magnification of the image occurs, and (3) the image itself is distorted, are conceivable. Under the circumstances, even if the cause itself cannot be eliminated, it is possible by correcting or deforming the individual exposure image RG to eliminate the shift of the image pattern at the boundary between the adjacent projection images TG.

As illustrated inFIG. 6, in Embodiment 2, as well as Embodiment 1, the position of the image pattern included in the projection image TG in the plane of the projection surface TM is measured. Then, a difference amount of the measured position with respect to a design position of the image pattern is calculated. Then, the image data of the exposure image RG is corrected so that the position of the image pattern on the projection image TG on the projection surface TM becomes the design position.

(Correction of Exposure Image)

FIG. 9is a flowchart for describing shift correction control of the projection image according to Embodiment 2.FIGS. 10A and 10Bare explanatory diagrams for describing correction of the exposure image. More specifically,FIG. 10Ashows the exposure image before the correction, andFIG. 10Bshows the exposure image after the correction. As illustrated inFIG. 6, in Embodiment 2, the image data of the first exposure image RGa or the second exposure image RGb corresponding to the boundary region KR is adjusted, thereby aligning the adjacent projection images TGa and TGb.

As illustrated inFIG. 9, after the start of the manufacture, at a photographing timing of each predetermined time (1 second) (YES in S32), by using the camera130, the CPU111photographs the respective projection images TGa and TGb of the exposure images RGa and RGb projected onto the boundary region KR, and captures the photographed image (S33).

The CPU111compares the image located in the boundary region KR of the photographed product projection image30G with the before-division exposure image RG projected onto the boundary region KR to decide whether or not the gap GP is generated. When the gap GP is generated, the CPU obtains the number of pixels in the gap GP and the number of positional shift pixels in the direction along the gap, and calculates the positional shift correction amount and the inclination correction amount of the projection region TR (S34).

As illustrated inFIG. 10A, if the positional shift occurs between the adjacent projection regions TR, there is case where the gap GP is generated in the product projection image30G. At this time, in Embodiment 2, as illustrated inFIG. 10B, the individual projection region TR is not moved. Instead, the projection image TG of the exposure image RG is moved in the projection region TR as indicated by arrows, thereby canceling the gap GP. A contour position of the product manufactured object30in the exposure image RG displayed on the image forming element23is shifted by the positional shift correction amount and is inclined by the inclination correction amount.

The CPU111corrects the exposure image RG of each layer to be used for subsequent manufacture of the product manufactured object30, such that the contour position of the product manufactured object in the original exposure image RG is moved by the positional shift correction amount and is inclined by the inclination correction amount (S35). When the manufacture of the product manufactured object30ends (YES in S31), the CPU111ends the shift correction control of the projection image.

As illustrated inFIG. 6, in Embodiment 2, the image data of at least one of the two exposure images RGa and RGb located in the boundary region KR where the gap GP has been generated is adjusted. Therefore, there is no need to provide a mechanism for moving the image forming element23. Besides, vibration or noise caused by the mechanical movement of the image forming element23does not occur.

If the illuminances of the product projection image are different from each other across the boundary between the adjacent projection images, a streak in the manufacturing direction is made at the boundary position of the product manufactured object30. Therefore, in Embodiment 3, adjustment for eliminating an illuminance (brightness) difference between the adjacent projection images is performed.

That is, when there is an illuminance difference between the images at the boundary between the adjacent projection images TG, (1) a performance difference of the projection optical systems25and (2) a performance difference of the light sources21are conceivable. Therefore, in Embodiment 3, the illuminance distribution on the projection surface TM of the projection image TG is measured, and the brightness gradation (duty ratio) of each pixel in the plane of the image forming element23is adjusted such that the illuminance distribution becomes uniform. Moreover, the brightness gradation (duty ratio) of each pixel in the plane of the image forming element23is controlled such that the illuminance difference of the adjacent projection images TG across the boundary is eliminated.

As described above, even if the boundary region KR has about ten pixels, when an overlap of the optical images of patterns occurs, the areas which are set that ultraviolet light is incident overlap each other and the exposure amount locally doubles. For this reason, a degree of polymerization of the resin material10in the relevant portion increases or the pattern dimension becomes thick, thereby causing the streak pattern in the manufacturing direction. Therefore, with regard to the region which is set that ultraviolet light is incident and in which the projection is performed so that patterns overlap each other, it is necessary to sum up the irradiation amounts of both the adjacent regions and then lower the illuminance amount of ultraviolet light such that the summed radiation amount becomes equal to the irradiation amount of the region in which patterns do not overlap each other. It is necessary to control the irradiation amount of ultraviolet light by performing duty control or the like on a pixel basis of the image forming element23.

FIG. 11is a flowchart for describing of illuminance correction control of the projection image according to Embodiment 3.FIGS. 12A to 12Care explanatory diagrams for describing correction of the exposure image. More specifically,FIG. 12Ashows a state before the correction,FIG. 12Bshows illuminance correction, andFIG. 12Cshows a state after the correction. The light source21, which is an example of the adjusting unit, can adjust the output of the light source21for each projector20. The controlling unit110adjusts an illuminance level difference of the boundary region KR by controlling the light source21.

As illustrated inFIG. 11, after the start of the manufacture, at a photographing timing of each predetermined time (1 second) (YES in S42), by using the camera130, the CPU111photographs the projection image of the exposure image projected onto the boundary region KR, and captures the photographed image (S43).

In Embodiment 3, the portion located in the boundary region KR of the product projection image extending over the two projection images is detected, and the illuminance correction amount of the two projection images is obtained (S44).

For example, when there is an illuminance difference in the product projection images30G and30G′ as illustrated inFIG. 12Aand the illuminance difference is detected as illustrated inFIG. 12B, the illuminance difference in the product projection images30G and30G′ are corrected as indicated by the broken line. Thus, as illustrated inFIG. 12C, the illuminances of the product projection images30G and30G′ sandwiching the boundary are made equivalent.

The CPU111extracts the portion located in the boundary region KR of the product projection images30G and30G′ of the adjacent projection images TG and TG′. Then, an average illuminance of the product projection image30G is compared with an average illuminance of the product projection image30G′ in this portion, thereby obtaining the illuminance correction amount (S44).

The CPU111corrects the exposure image RG of each layer to be used for subsequent manufacture of the product manufactured object30so as to change the brightness gradation of the product manufactured object in the original exposure image RG by the illumination correction amount (S45). When the manufacture of the product manufactured object30ends (YES in S41), the CPU111ends the illuminance correction control of the projection image.

In Embodiment 3, brightness information of the first exposure image or the second exposure image corresponding to the boundary region KR is adjusted. Therefore, it is possible to suppress the streak in the manufacturing direction (i.e., dispersion in manufacturing length in a direction along the boundary) caused by the illuminance level difference in the boundary region.

Incidentally, in the additive manufacturing apparatus100, it is also possible to adjust the illuminance of the entire projection image TG by changing output of the light source21. Accordingly, the controlling unit110can adjust the illuminance level difference of the boundary region KR by controlling the light source21. By controlling the light source21, it is possible to reduce the illuminance level difference in the boundary region KR and suppress the streak in the manufacturing direction (i.e., the dispersion in the manufacturing length in the direction along the boundary) caused by the illuminance level difference.

In Embodiment 4, the inclination of the image forming element27is adjusted according to the inclination of the transmitting member12, thereby securing a liquid layer31having an appropriate thickness between the transmitting member12and the product manufactured object30.

FIGS. 13A and 13Bare explanatory diagrams for describing a deflection (or flexure) of the projection surface, andFIG. 14is an explanatory diagram for describing an inclination adjusting mechanism of the projection surface of the exposure image. More specifically,FIG. 13Ashows the projection surface, andFIG. 13Bshows the deflection of the transmitting member. As illustrated inFIG. 13A, the transmitting member12is disposed on the bottom surface of the vessel11, and the resin material10is stored on the transmitting member12. As described above, the projection optical system25projects the exposure image RG formed on the image forming element23onto the projection surface TM formed at the image forming position28.

As illustrated inFIG. 4A, the image displaying unit40holds, by the actuators51to53, the image forming element23inside the casing40fso that the inclination angle thereof can be adjusted within the XZ plane and the YZ plane. Namely, the actuators51to53can adjust the inclination of the image forming element23with respect to the projection optical axis of the exposure image. The actuators51to53can expand and contract according to the applied DC voltage and rotate the image forming element23in the XZ plane. Therefore, the controlling unit110can arbitrarily adjust the inclination of the projection surface TM.

In the additive manufacturing apparatus100, when the transmitting member12is made thick, sufficient oxygen cannot be supplied to the interface with the resin material10, so that the liquid layer31cannot be formed. On the other hand, in the additive manufacturing apparatus100, the large manufacturing area is secured such that the large-sized product manufactured object30can be formed. Therefore, as illustrated inFIG. 13B, when the resin material10is injected into the vessel11, the rigidity of the transmitting member12becomes insufficient, and the center of the transmitting member12is deflected downward by gravity.

As a result, since the liquid layer31having the appropriate thickness is not secured between the transmitting member12and the product manufactured object30, accurate manufacture at the image forming position28cannot be performed. Besides, since the transmitting member12under the projection surface TM is inclined such that the center thereof becomes low and the periphery thereof becomes high, the projection surface TM of the exposure image RG by the projection optical system25is greatly away from the transmitting member12at the center of the transmitting member12. In this case, the exposure image is projected, in a state of defocus, on the surface of the transmitting member12securing the liquid layer31having the appropriate thickness. Thus, the manufacturing resolution of the additive manufacturing apparatus100is lowered.

Therefore, the controlling unit110obtains the inclination amount of the transmitting member12by processing the photographed image of the camera130. Then, the controlling unit inclines the image forming element23in the XZ plane and in the YZ plane by using the actuators51to53, thereby forming the projection surface TM substantially parallel to the transmitting member12as illustrated inFIG. 14.

(Angle Correction Control of Projection Surface)

FIG. 15is a flowchart for describing angle correction control of the projection surface according to Embodiment 4. As illustrated inFIGS. 4A to 4C, the actuators51to53, which are the examples of the adjusting unit, can adjust the inclination of the image forming element23with respect to the projection optical axis of the exposure image. The controlling unit (110:FIG. 2) adjusts the inclination of the projection surface TM of the projection image TG by controlling the actuators51to53.

As illustrated inFIG. 15, when it is instructed to start the angle correction control, the CPU111displays the positioning mark on the image forming element23, and forms the positioning image IG at the interface between the resin material10and the transmitting member12as illustrated inFIG. 6. Then, the camera130photographs the positioning image IG and captures the photographed image (S51).

The CPU111detects a difference in blur amount of the pair of positioning images IG along the boundary between the pair of projection images TG, and attempts to measure a distance difference to the pair of positioning images IG (S52). Then, when the distance difference to the pair of positioning images IG is obtained (YES in S53), the CPU operates the actuators51to53such that the distances to the pair of positioning images IG coincide with each other, thereby setting the projection surface TM to be inclined substantially parallel to the transmitting member12(S55).

That is, when one of the pair of positioning images IG has a small blur amount and it is clearly detected, it is possible measure the distance difference to the pair of positioning images IG by evaluating a blur amount of the other image. The inclination of the interface of the transmitting member12can be obtained from the distance difference measured using a so-called autofocus principle.

When the distance difference to the pair of positioning images IG cannot be obtained, the CPU111operates the actuators51to53to incline the image forming element23by a predetermined amount in a direction corresponding to the direction in which the transmitting member12is deflected (bent) and inclined (S54). Then, until the distance difference to the pair of positioning images IG is obtained (NO in S53), the projection and the photographing of the positioning image IG are repeated (S51, S52).

Incidentally, in Embodiment 4, the inclination amount of the transmitting member12or the deflection amount of its center are estimated by evaluating the photographed image of the positioning image IG by using the camera130. However, it may be possible, by disposing a vertical-direction distance sensor such as an ultrasonic sensor or the like at the center of the transmitting member12, to measure a descent amount at the center of the transmitting member12, and estimate the inclination amount of the transmitting member12based on the measured descent amount.

In the additive manufacturing apparatus100, if there is a deflection in the transmitting member12, the deflection itself becomes a cause of a positional shift of the projection image TG, a cause of a magnification difference and a cause of a distortion of an image itself. For this reason, when coping with these causes by correcting the image of the exposure image RG, the correction becomes complicated. Besides, as the size of the vessel11increases in order to manufacture the large-sized product manufactured object30, the deflection of the transmitting member12increases. Therefore, in Embodiment 5, a pressure of an oxygen chamber62is adjusted according to the inclination of the transmitting member12, thereby reducing a distortion of the transmitting member12. Thus, the liquid layer31having an appropriate thickness is secured between the transmitting member12and the product manufactured object30.

As illustrated inFIG. 2, in Embodiment 5, the vessel11is the resin tank (=monomer-material tank) of the additive manufacturing apparatus100. The vessel holds the monomer material on the projection surface (=manufacturing surface), and has the transmitting member12having ultraviolet light permeability for irradiation of ultraviolet light. As illustrated inFIG. 16B, a space tightly sealed from the outside is provided outside the transmitting member12of the vessel11. A pressurizing unit comprises an adjusting mechanism for introducing gas into the sealed space and adjusting a gas pressure of the sealed space. Then, the controlling unit controls the adjusting mechanism so as to suppress, by controlling an air pressure in the sealed space, deformation (due to gravity) of the transmitting member12caused by introducing the resin material10into the vessel11. The controlling unit detects a position of the surface of the transmitting member12, and controls the air pressure of the sealed space according to a detected value of the position, thereby keeping the position of the surface of the transmitting member12within a desired range. The transmitting member12is oxygen permeable. The space between the transmitting member12and a quartz glass plate61is filled with a gas having a pressure higher than atmospheric pressure containing oxygen.

FIGS. 16A and 16Bare explanatory diagrams for describing of an oxygen supplying chamber. More specifically,FIG. 16Ais the diagram for describing a deflection state of the transmitting member, andFIG. 16Bis the diagram for describing an oxygen supplying system. As illustrated inFIG. 2, the transmitting member12, which is an example of a first transmitting member, has oxygen permeability, and transmits oxygen to form the oxygen-rich liquid layer31at the interface with the resin material10. The transmitting member12holds the resin material10, and transmits, from below into the resin material10, the exposure image for solidifying the resin material. The quartz glass plate61, which is an example of a second transmitting member, forms an oxygen supplying chamber65which is an example of the space between the quartz glass plate and the transmitting member12. The projection optical system25transmits the exposure image through the quartz glass plate61and the transmitting member12, thereby projecting transmitted image into the resin material.

As illustrated inFIG. 16A, it is desirable to form that the transmitting member12thin in order not to impair the oxygen permeability and the ultraviolet ray permeability. In a case where the transmitting member12has a thin thickness not having rigidity as a plate material, when the resin material10is stored in the vessel11, the center of the transmitting member tends to be lowered and the resin material10tends to be deformed into an inverted dome shape, due to the weight of the resin material10. When a large projection area (e.g., 100 mm square or more) is ensured in the transmitting member12, there is a case where the thickness of the resin material10under the manufactured object is different between the center and the periphery of the transmitting member12by 100 μm or more. As a result, since the liquid layer31having an appropriate thickness is not secured between the transmitting member12and the product manufactured object30, accurate manufacture at the image forming position28cannot be performed. Besides, since the transmitting member12under the projection surface TM is inclined such that the center thereof is low and the periphery thereof is high, the projection surface TM of the exposure image RG by the projection optical system25is greatly away from the transmitting member12at the center of the transmitting member12. In this case, the exposure image is projected, in a state of defocus, on the surface of the transmitting member12securing the liquid layer31having the appropriate thickness. Thus, the manufacturing resolution of the additive manufacturing apparatus100is lowered. Therefore, in Embodiment 5, as illustrated inFIG. 16B, the oxygen chamber62is disposed outside the vessel11and the quartz glass plate61which transmits the ultraviolet light is brought into close contact with the bottom surface of the oxygen chamber62, thereby forming the airtight oxygen supplying chamber65. Then, oxygen gas supplied from an oxygen cylinder64can be adjusted to an arbitrary pressure by a pressure adjusting device63and supplied to the oxygen supplying chamber65.

Then, the pressure adjusting device63, which is an example of the pressurizing unit, supplies oxygen to keep the gas pressure of the oxygen supplying chamber65higher than the atmospheric pressure. By adjusting the pressure adjusting device63and increasing the pressure of the oxygen supplying chamber65, the weight of the resin material10is canceled out and the transmitting member12is upwardly pushed back to the horizontal state to keep the pressure. Incidentally, the gas to be supplied to the oxygen supplying chamber65may be 100% oxygen, but may be a gas such as nitrogen containing oxygen. Also, the atmosphere may be used as the gas. In order to suppress the deflection of the transmitting member12, it is necessary to apply a certain pressure. However, in this case, when pure oxygen gas is used, there is a possibility that an oxygen inhibiting effect by the transmitting member12becomes too large. In such a case, it is possible to control an oxygen supply amount by decreasing a partial pressure of the oxygen contained in the supplied gas. That is, the pressure adjusting device63can adjust the pressure of the supplied gas and the oxygen partial pressure.

The controlling unit110obtains the pressure and the oxygen partial pressure of the oxygen supplying chamber65capable of correcting the deflection of the transmitting member12, by using the pressure of the gas to be supplied, the oxygen partial pressure, and the oxygen permeability of the transmitting member12as three parameters. Then, the controlling unit110controls the pressure adjusting device63such that the obtained pressure and the obtained oxygen partial pressure are output, thereby achieving both the oxygen inhibiting effect and the deflection correcting effect of the transmitting member12.

A distance sensor66projects a visible-light index into the resin material10and images an index image formed by a difference in refractive index of the interface between the resin material10and the transmitting member12. Then, by performing so-called autofocus control for adjusting the focal length of the lens such that the index image is formed on the imaging element of the distance sensor66, the distance to the index image is measured. The controlling unit110operates the pressure adjusting device63such that the distance to the index image output by the distance sensor66is made coincident with a reference value in which the transmitting member12does not have distortion. The controlling unit110automatically controls the pressure of the oxygen supplying chamber65so as to cancel out the distortion of the transmitting member12.

As illustrated inFIG. 8A, when the center-to-center distance between the two adjacent projection regions increases, the gap is formed in the product projection image30G, so that the resin material located in the gap is not solidified. Therefore, in Embodiment 6, the exposure image of the product manufactured object is subjected to an image process, so that the gap is difficult to be formed in the product projection image30G even when the center-to-center distance between the two adjacent projection regions increases. Namely, when dividing the exposure image for each projector20, an image range and an illuminance gradation of the portion of the boundary region KR extending over the adjacent projection images TG in the manufacture image of the product manufactured object30are adjusted.

In the image process according to Embodiment 6, even when there is a positional shift of the image pattern on the boundary between the adjacent projection images TG, the exposure image itself is deformed or adjusted such that an influence on manufacture quality of the product manufactured object30is reduced. That is, an overlap region is provided such that the same image data if displayed on both the exposure images adjacent to the boundary region. Then, a duty ratio of each pixel in the overlap region is set such that an illuminance difference between the overlap region and an image adjacent to the overlap region becomes a desired value or less.

FIGS. 17A to 17Care explanatory diagrams for describing the image process of the exposure image of the product manufactured object. More specifically,FIG. 17Ashows the exposure image of the product manufactured object,FIG. 17Bshows the exposure image of one projection region, andFIG. 17Cshows the exposure image of the other projection region. In Embodiment 6, an illuminance of a first exposure image (G1) or a second exposure image (G2) corresponding to the boundary region KR is adjusted.

As illustrated inFIG. 17A, the product projection image30G extends over two projection regions TR1and TR2.

As illustrated inFIG. 8A, in Embodiment 1, since the product projection image30G is formed within the range of the projection image TG, the gap of the projection image TG is the gap of the product projection image30G as it is. On the other hand, in Embodiment 6, as illustrated inFIG. 17B, an illuminance gradation that the projection image G1protrudes into a projection image TG2and falls stepwise is given. Besides, as illustrated inFIG. 17C, an illuminance gradation that the projection image G2protrudes into a projection image TG1and falls stepwise is given.

Thus, the product projection image30G located in the boundary region KR is exposed to both the projection image TG1and the projection image TG2. Thus, even if the center-to-center distance between the adjacent projection regions TR1and TR2increases and the gap is formed in the adjacent projection images TG1and TG2, no gap is generated in the boundary region KR of the product projection image30G.

As illustrated inFIG. 2, the CPU111sets the exposure image of each layer of the product manufactured object30and creates the exposure image divided for each projector20. At this time, the CPU111extracts the manufacturing region of the product manufactured object30extending over the adjacent exposure images and sets the manufacturing region protruding into the adjacent exposure image. Then, the CPU sets the illuminance of the exposure image of the boundary region such that the illuminance is gradually reduced in the range where the adjacent projection regions TR overlap each other.

When the individual exposure image RG obtained by dividing the entire exposure image with the plurality of projectors20is projected, the positional shift of the image pattern may be detected at the boundary between the adjacent projection images TG. At this time, as described above, the positional shift of the image pattern may be caused by the magnification difference of the exposure image or the distortion of the projection image. For this reason, when the correction amount of the image data of the exposure image RG in the additive manufacturing apparatus100is large, it is desirable to perform calibration of the projection optical system25. In Embodiment 7, the calibration of the additive manufacturing apparatus100will be described.

FIG. 18is an explanatory diagram for describing the calibration. As illustrated inFIG. 18, the camera130individually comprises an XY stage72having a lock mechanism. The controlling unit110can control the XY stage72to rotate and translate the photographing region of the camera130in the XY plane. The projector20individually comprises an XY stage74having a lock mechanism. The controlling unit110can control the XY stage74to rotate and translate the photographing region of the projector20in the XY plane. In the calibration, the controlling unit110operates the XY stages72and74to adjust the positions of the camera130and the projector20respectively, and then locks the XY stages72and74. In the calibration, an instruction operation, a calibration result and an image are displayed through the external computer122. The controlling unit110automatically performs the calibration in response to the instruction operation, and transmits the calibration result and the image to the external computer122.

FIGS. 19A and 19Bare explanatory diagrams for describing an alignment reference plate. More specifically,FIG. 19Ashows a positioning image, andFIG. 19Bshows an alignment plate.FIGS. 19A and 19Bschematically show planar arrangements of the four adjacent projectors20inFIG. 18. As illustrated inFIG. 18, the calibration is performed by positioning an alignment reference plate70at the image forming position28. By precisely positioning and fixing the alignment reference plate70to the pull-up member13and actuating the pull-up device17, the alignment reference plate70is positioned at the image forming position28of the plurality of projection optical systems25with high repeatability. As illustrated inFIG. 19B, the alignment reference plate70is a jig to be used at the time of the calibration. On the lower surface of the alignment reference plate70, four indices IM are arranged for each projector20, and one index IC is formed for each camera130.

As illustrated inFIG. 19A, at the position immediately below the index IC facing each camera130, the controlling unit110first adjusts the position of the camera130such that the index IC can be photographed at the center of the photographed image. The controlling unit110processes the photographed image of the index IC obtained by the camera130. Then, when there is a positional shift or an inclination between the center position of the photographed image and the index IC, the controlling unit decides that the camera130is shifted or inclined, and performs the correction by the XY stage72.

The controlling unit110subsequently operates the projector20to project the positioning image IG onto the alignment reference plate70by the projection optical system25as illustrated inFIG. 19A. The positioning image IG is an aligning pattern which is projected on the projection surface TM where the manufacturing surface is formed. The controlling unit110operates the camera130to photograph an overlap between the positioning image IG and the index IM of the alignment reference plate70. The controlling unit110reads position information of the positioning image IG included in the photographed and captured data of the camera130and position information of the index IM of the alignment reference plate70, and calculates a necessary adjustment amount of the projector20.

The controlling unit110processes the photographed image, and obtains a positional shift amount between the positioning image IG and the index IM and an inclination amount. Then, the controlling unit operates the XY stage74to adjust the positional shift amount and the inclination amount, and adjusts an enlargement magnification of the projector20. The controlling unit110adjusts the position and the enlargement magnification of the projection optical system25, such that the four positioning images IG for each projection optical system25are positioned on the corresponding four indices IM of the alignment reference plate70and the positioning images IG of the adjacent projectors20overlap each other.

Incidentally, from the viewpoints of workability and mechanical adjustment accuracy, it is preferable to perform the calibration in a state that the resin material10is removed from the vessel11as illustrated inFIG. 18. However, since the photographed image of the camera130is not actually information reflecting a refractive index of the resin material10, it is necessary to perform final confirmation in a state that the resin material10is introduced into the vessel11. Alternatively, the calibration may be carried out by introducing an inexpensive liquid having the same refractive index as that of the resin material10and having no light manufacturability.

In Embodiment 5, as illustrated inFIGS. 16A and 16B, the oxygen supplying chamber65is provided on the lower surface of the transmitting member12, the gas pressure in the oxygen supplying chamber65is increased by the pressure adjusting device63, and thus the deflection of the transmitting member12is canceled out. On the other hand, in Embodiment 8, as illustrated inFIG. 20, a liquid tank201is provided on the lower surface of the transmitting member12, and an oxygen-soluble liquid202is filled in the liquid tank201to apply buoyancy, thereby canceling the deflection of the member12.

FIG. 20is the explanatory diagram for describing the liquid tank according to Embodiment 8. As illustrated inFIG. 20, the transmitting member12, which is the example of the first transmitting member, holds the photosetting liquid resin material and transmits the exposure image which solidifies the resin material. A quartz glass plate61, which is an example of the second transmitting member, forms a space between the quartz glass plate and the transmitting member12. The projector20, which is the example of the image projecting unit, projects the exposure image into the resin material through the quartz glass plate61and the transmitting member12. The pull-up device17, which is the example of the moving unit, moves a not-illustrated manufacturing layer manufactured by solidifying the resin material by the exposure image away from the transmitting member12. The transmitting member12is a membrane material of a fluororesin having oxygen permeability. The transmitting member12allows oxygen dissolved in the oxygen-soluble liquid202to be transmitted toward the resin material10, thereby forming the oxygen-rich liquid layer31at the interface between the transmitting member12and the resin material10.

As described above, in the additive manufacturing apparatus100, if there is the deflection in the transmitting member12, the deflection itself becomes the cause of the positional shift of the projection image (TG:FIG. 5), the cause of the magnification difference and the cause of the distortion of the image itself. For this reason, when coping with these causes by correcting the image of the exposure image RG, the correction becomes complicated. Therefore, in Embodiment 8, the liquid tank201is provided outside the vessel11, and the space between the transmitting member12and the liquid tank201is filled with the oxygen-soluble liquid202, thereby reducing the deflection of the transmitting member12. The space between the transmitting member12and the quartz glass plate61is filled with the oxygen-soluble liquid in which oxygen having a mole fraction of 0.001 or more is dissolved so as not to impede oxygen supply to the transmitting member12.

The vessel11is the resin tank (monomer-material tank) of the additive manufacturing apparatus100, and the vessel holds the monomer material on the projection surface (manufacturing surface). The transmitting member12having ultraviolet light permeability for irradiating ultraviolet light is provided on the lower surface of the vessel11. Then, a liquid supplying device204introduces the oxygen-soluble liquid202between the transmitting member12and the liquid tank201to apply pressure from the lower side to the transmitting member12, thereby preventing the deflection of the transmitting member12. Then, the liquid layer31having an appropriate thickness is secured between the transmitting member12and the product manufactured object30. Further, during the manufacture of the product manufactured object30, when the product manufactured object30is moved in the direction away from the transmitting member12, the oxygen-soluble liquid202being in contact with the transmitting member12acts as a damper to resist the deflection of the transmitting member12in an upward direction.

The liquid supplying device204adjusts a liquid introduction amount so as to suppress a deformation of the transmitting member12(caused by gravity) due to the introduction of the resin material10into the vessel11, by introducing the oxygen-soluble liquid202into the liquid tank201. The liquid supplying device204, which is an example of a liquid amount controlling unit, controls the liquid amount of the oxygen-soluble liquid202, i.e., a height of a liquid surface203such that the projection surface of the transmitting member12is kept flat.

Here, in a case where specific gravity of the resin material10is the same as that of the oxygen-soluble liquid202, mere adjustment of a liquid surface205of the resin material10and the liquid surface203of the oxygen-soluble liquid202to the same height makes the pressure applied to the transmitting member12by the resin material10and the pressure applied to the transmitting member12by the oxygen-soluble liquid202equal to each other. Thus, the transmitting member12is not deflected. However, in fact, the specific gravity of the resin material10and the transmitting member12is different from that of the oxygen-soluble liquid202. Therefore, the controlling unit110detects the position of the surface of the transmitting member12by using a distance sensor66, adjusts the supply amount of the oxygen-soluble liquid202according to a detected value of the position, thereby keeping the position of the surface of the transmitting member12within a desired range.

The distance sensor66projects a visible-light index into the resin material10, and images an index image formed by a refractive index difference in the interface between the resin material10and the transmitting member12. Then, by performing so-called autofocus control for adjusting a focal length of the lens such that the index image is imaged on an imaging element of the distance sensor66, a distance to the index image is measured. The controlling unit110operates the liquid supplying device204such that the distance to the index image output by the distance sensor66is coincided with a reference value given in a state that the transmitting member12is not deflected. The controlling unit110automatically controls the supply amount of the oxygen-soluble liquid202with respect to the liquid tank201so as to cancel out the deflection of the transmitting member12.

Instead of the distance sensor66, it is also possible to use, for example, a distance sensor of a type having a light source unit67and a detecting unit68. In this type, position information on the surface of the transmitting member12is obtained by detecting the position where a light beam emitted from the light source unit67is reflected on the surface of the transmitting member12and is incident on the detecting unit68.

Besides, it is also possible, by providing an oxygen supplying device206in a path for circulating the oxygen-soluble liquid202to the liquid supplying device204, to keep a concentration of the dissolved oxygen of the oxygen-soluble liquid202in the liquid tank201at a predetermined concentration. The oxygen supplying device206, which is an example of an oxygen supplying unit, supplies oxygen into the oxygen-soluble liquid202. An oxygen concentration sensor207and the controlling unit110, which are an example of a measuring unit, measure the oxygen concentration in the oxygen-soluble liquid202. The controlling unit110and the oxygen supplying device206, which are an example of the adjusting unit, operate the oxygen supplying device206such that the oxygen-soluble liquid202keeps the predetermined oxygen concentration based on a detection output of the oxygen concentration sensor207. The oxygen supplying device206may be constituted such that a window material such as an oxygen-permeable fluororesin is provided in a part or the whole of the liquid supplying device204so as to supply oxygen to the oxygen-soluble liquid202from a gas atmosphere containing oxygen such as the atmosphere or the like. The controlling unit110adjusts an oxygen supply amount by the oxygen supplying device206such that the oxygen concentration of the oxygen-soluble liquid202measured by the oxygen concentration sensor207becomes the predetermined oxygen concentration.

For the oxygen-soluble liquid202, a liquid capable of dissolving oxygen having a mole fraction of 0.001 or more, such as perfluorocarbons, can be used. When the oxygen concentration is less than the mole fraction of 0.001, an effective liquid layer31cannot be ensured, and there is a possibility that the resin material10is solidified on the surface of the transmitting member12. Preferable specific examples of the oxygen-soluble liquid202include perfluorooctane, perfluorobutyl perfluorotetrahydrofuran, perfluoro-1-isopropoxyhexane, perfluoro-1,4-diisopropoxybutane, and the like. Among them, perfluorobutyl perfluorotetrahydrofuran is particularly preferable from the viewpoint of the dissolved oxygen concentration.

Besides, in order to prevent attenuation of the light amount to be used for the exposure, it is necessary to use, as the oxygen-soluble liquid202, a substance having a high transmissivity of a light beam of wavelength used for the exposure. In the example illustrated inFIG. 20, a UV-LED (ultraviolet light-emitting diode) having the wavelength of 350 nm to 400 nm is used as the light source for the exposure. For this reason, as the oxygen-soluble liquid202, it is desirable to use a liquid material of which the light transmissivity with respect to the wavelength of 350 nm to 400 nm is 90% or more per 1 cm. Besides, it is desirable that the oxygen-soluble liquid202is a substance of which the light transmissivity with respect to the wavelength of 350 nm to 400 nm is 95% or more per 1 cm. Besides, it is more desirable that the light transmissivity of the substance is 99% or more per 1 cm.

In order to precisely control the deflection of the transmitting member12, it is preferable that the specific gravity of the oxygen-soluble liquid202is equal to the specific gravity of the resin material10. The specific gravity of the oxygen-soluble liquid202is preferably within ±80% of the specific gravity of the resin material10. The specific gravity of the oxygen-soluble liquid202is more preferably within ±20% of the specific gravity of the resin material10, and particularly preferably within ±10%.

The controlling unit110controls the supply amount of the oxygen-soluble liquid202to the liquid tank201by the liquid supplying device204and/or the height of the liquid surface203, in accordance with the detection value of the surface position of the transmitting member12. Thus, the state that the weight of the resin material10is canceled out and the transmitting member12is upwardly pushed back until it is horizontal is maintained. The liquid supplying device204can also reduce the upward deflection of the transmitting member12during the manufacture of the product manufactured object (30:FIG. 2), and hold the transmitting member12in a substantially horizontal state. The controlling unit110controls the amount of oxygen to be dissolved in the oxygen-soluble liquid202by the oxygen supplying device206, such that the oxygen inhibiting effect of the curing of the resin material10by the transmitting member12becomes appropriate.

In Embodiment 8, the liquid amount of the oxygen-soluble liquid202in the liquid tank201is adjusted to reduce the deflection of the transmitting member12. However, as a modification of Embodiment 8, it may be possible to cause the liquid tank201to have a sealed structure and adjust the pressure of the oxygen-soluble liquid202, thereby reducing the deflection of the transmitting member12. That is, the liquid supplying device204, which is an example of a pressure controlling unit, controls the pressure of the oxygen-soluble liquid202such that the projection surface of the transmitting member12is kept flat.

In Embodiment 8, as illustrated inFIG. 20, the constitution that the liquid tank201is provided on the lower surface of the horizontal transmitting member12and is filled with the oxygen-soluble liquid202has been described. In contrast, in Embodiment 9, as illustrated inFIG. 21, a constitution that the liquid tank201is provided on the side surface of a vertical transparent member and is filled with the oxygen-soluble liquid202will be described.

FIG. 21is the explanatory diagram for describing the liquid tank according to Embodiment 9. Incidentally, the constitution of Embodiment 9 is similar to that of Embodiment 8 except for a projection direction of the projection image (TG:FIG. 5) with respect to the resin material10and a manufacturing direction of the product manufactured object30, and is controlled in the same manner as the manner in Embodiment 8. For this reason, inFIG. 21, the same reference numerals as those inFIG. 20are assigned to the components common to those in Embodiment 8, and redundant explanations will be omitted. Besides, inFIG. 21, the constitution of the projector20, the aligning mechanism, and the like are omitted.

As illustrated inFIG. 21, in the additive manufacturing apparatus100according to Embodiment 3, if there is the deflection in the transmitting member12, the deflection itself becomes the cause of the positional shift of the projection image (TG:FIG. 5), the cause of the magnification difference and the cause of the distortion of the image itself. Besides, as the size of the vessel11increases in order to manufacture the large-sized product manufactured object30, the deflection of the transmitting member12increases. Besides, in Embodiment 9, the transmitting member12is disposed on the side surface of the vessel11, and the exposure image is irradiated in the horizontal direction from the projector20, thereby manufacturing the product manufactured object30in the horizontal direction. When the transmitting member12is disposed on the side surface of the vessel11, the pressure due to gravity applied to the transmitting member12when the resin material10is introduced into the vessel11increases as the position in the transmitting member12is lower. Therefore, a higher (heavier) pressure is applied to the lower portion in the transmitting member12, and the lower portion of the transmitting member12bulges outwardly, so that a large deflection occurs. At this time, since the surface shape of the transmitting member12is deformed complicatedly, it is difficult to correct the shape of the projection image at the time of the exposure. When coping with such a situation by the correction of the image of the exposure image RG, the correction of the image becomes complicated.

Therefore, in Embodiment 9, the liquid tank201is provided outside the transmitting member12of the vessel11, and the oxygen-soluble liquid202is filled between the transmitting member12and the liquid tank201. The oxygen-soluble liquid202applies a higher (larger) pressure at the lower position of the transmitting member12, and the resin material10applies a higher (larger) pressure at the lower position of the transmitting member12, so that these higher pressures at the lower position of the transmitting member12can be cancelled out by the oxygen-soluble liquid202. Besides, by adjusting the liquid amount of the oxygen-soluble liquid202, the deflection of the transmitting member12is reduced, and the liquid layer31having an appropriate thickness is secured between the transmitting member12and the product manufactured object30.

In Embodiment 9, the transmitting member12having the ultraviolet light permeability for performing the irradiation of ultraviolet light is disposed on the side surface of the vessel11. The projector20irradiates the exposure image for solidifying the resin material10from the side of the transmitting member12into the resin material10. The pull-up device17moves the product manufactured object30in the horizontal direction to perform the manufacture.

In Embodiment 9, the liquid tank201is provided outside the vessel11, and the oxygen-soluble liquid202is filled between the vessel11and the liquid tank201. As each of the quartz glass plate61and the oxygen-soluble liquid202, a material having a low absorptivity with respect to light having the wavelength used for the exposure is used. The oxygen-soluble liquid202is desirably a material which transmits 90% or more of light having a wavelength to be used for the exposure. The oxygen-soluble liquid202applies the pressure from the side to the transmitting member12to cancel out the horizontal deflection of the transmitting member12due to the pressure of the resin material10. Here, when the specific gravity of the resin material10, the specific gravity of the transmitting member12and the specific gravity of the oxygen-soluble liquid202are the same, the pressures applying on both the surfaces of the transmitting member12are canceled out by adjusting the liquid surface205of the resin material10and the liquid surface203of the oxygen-soluble liquid202to the same height. However, in fact, the specific gravities of the resin material10, the transmitting member12and the oxygen-soluble liquid202are different respectively.

Therefore, the controlling unit110adjusts a liquid amount to be supplied to the liquid tank201by the liquid supplying device204, such that the deformation of the transmitting member12toward the outside occurring due to the weight of the resin material10in the vessel11is canceled out or suppressed by the pressure of the oxygen-soluble liquid202. As well, as Embodiment 8, the controlling unit110detects the position of the surface of the transmitting member12from the outside of the liquid tank201by using the distance sensor66, and adjusts the supply amount of the oxygen-soluble liquid202according to the detected value of the position. The controlling unit110controls the liquid supplying device204according to the surface position of the transmitting member12to adjust the supply amount of the oxygen-soluble liquid202with respect to the liquid tank201and/or the height of the liquid surface203. Thus, a pressure distribution in a depth direction that the resin material10exerts on the transmitting member12is canceled out, and the transmitting member12is pushed back to the vertical state and held.

The distance sensor66projects a visible-light index into the resin material10and images an index image formed by a difference in refractive index of the interface between the resin material10and the transmitting member12. Then, by performing so-called autofocus control for adjusting the focal length of the lens such that the index image is formed on the imaging element of the distance sensor66, the distance to the index image is measured. The controlling unit110operates the liquid supplying device204such that the detected distance to the index image is made coincident with a predetermined reference value. The controlling unit110automatically controls the supply amount of the oxygen-soluble liquid202to the liquid tank201so as to cancel out a vertical deflection distribution of the transmitting member12and hold the transmitting member12substantially linearly. The deflection of the transmitting member12caused by the movement of the product manufactured object30during the manufacture is reduced by controlling the supply amount of the oxygen-soluble liquid202to the liquid tank201and/or the height of the liquid surface203.

Incidentally, when the specific gravities of the resin material10and the oxygen-soluble liquid202facing each other across the transmitting member12are different from each other, even how the liquid amounts of both the material and the liquid are adjusted, the pressure distribution in the direction of the transmitting member12applied to the transmitting member12cannot be made uniform. Therefore, it is desirable that the resin material10and the oxygen-soluble liquid202have substantially the same specific gravity.

The oxygen supplying device206dissolves a predetermined amount of oxygen in the oxygen-soluble liquid202which is to be supplied to the liquid tank201by the liquid supplying device204. The controlling unit110controls the amount of the oxygen dissolved in the oxygen-soluble liquid202by the oxygen supplying device206such that the oxygen inhibiting effect by the transmitting member12becomes appropriate.

In Embodiment 9, the liquid amount of the oxygen-soluble liquid202in the liquid tank201is adjusted to reduce the deflection of the transmitting member12. However, as a modification of Embodiment 9, it may be possible to cause the liquid tank201to have a sealed structure and adjust the pressure of the oxygen-soluble liquid202, thereby reducing the deflection of the transmitting member12. That is, the liquid supplying device204, which is the example of the pressure controlling unit, controls the pressure of the oxygen-soluble liquid202such that the projection surface of the transmitting member12is kept flat.

Other Embodiments

FIGS. 22A and 22Bare explanatory diagrams for describing another example of the camera arrangement.FIG. 23is an explanatory diagram fir describing another example of the light source.FIGS. 24A and 24Bare explanatory diagrams for describing other examples of the manufacturing direction of the product manufactured object. More specifically,FIG. 22Ashows an intermediate position of the projection optical system, andFIG. 22Bshows the outside of the manufacturing region. Besides,FIG. 24Ashows an embodiment in which manufacture is performed in the downward direction, andFIG. 24Bshows an embodiment in which manufacture is performed in the horizontal direction.

It should be noted that the additive manufacturing apparatus of the present invention is not limited to the specific constitutions, parts form, parts properties, actual dimensions, and the like in Embodiments 1 to 6. Namely, the present invention can also be implemented in another embodiment in which some or all of the constitutions of Embodiments 1 to 6 are replaced with equivalent members.

In Embodiment 1, as illustrated inFIG. 1, the embodiment in which the manufacture of 500 mm×500 mm can be performed using the 5×5 projectors20has been described. However, Embodiment 1 can be implemented even in a case where arbitrary number of the projectors20such as 2, 3, 4 or the like are used. The projection area of one projector is not limited to 100 mm×100 mm. Namely, it may be possible to use an area of 10 mm×10 mm, 50 mm×50 mm or the like.

In Embodiment 1, the embodiment in which each layer is manufactured by projecting the exposure image into the resin material has been described. However, the invention of adjusting the boundary region of the divided exposure images can also be implemented in an additive manufacturing apparatus which performs exposure by scanning a line image, and an additive manufacturing apparatus which draws an image by scanning a beam spot.

As illustrated inFIG. 22A, the camera130may be disposed at an intermediate position in the four projection optical systems25. Besides, for the camera130, a photographing region (image extraction region) SR including the corners of the four projection images TG may be set so as to photograph the corners of the four projection images TG at the same time. That is, the disposition of the camera130is not limited to the intermediate position between the two projection optical systems25.

As illustrated inFIG. 22B, the cameras130may be arranged to photograph index images LC projected outside the four corners of the 25 projection images TG. The manufacturing region by the 5×5 projectors20corresponds to a range which is defined by the outside contour of the 5×5 projection images TG. The index images LC are projected outside the suchlike manufacturing region and within a range where the projectors20at the four corners can project the index images.

As illustrated inFIG. 2, the controlling unit110causes the four cameras130ofFIG. 22Bto photograph the overlaps between alignment marks provided at the four corners outside the manufacturing region of the transmitting member12and the index images LC respectively during the manufacture of the product manufactured object30. Then, the controlling unit monitors a reference position of the projection image TG in real time. In order to obtain alignment information outside the manufacturing region, the camera130is provided at the outer periphery of the manufacturing region.

An alignment mark projecting from the surface or an alignment mark having a light shielding property can be used as long as it is outside the manufacturing region of the transmitting member12. Besides, as long as it is outside the manufacturing region of the transmitting member12, even if ultraviolet light is irradiated, curing of the resin which affects the manufacture of the product manufactured object30does not occur. Besides, it is possible to perform real-time monitoring of the alignment of the projection image by concurrently using ultraviolet light irradiation control in the image forming element23, such as irradiation of ultraviolet light only at the detection of the alignment mark, decrease in an irradiation amount, or the like.

As illustrated inFIG. 23, it may be possible to provide a light source21R which outputs visible light for photography illumination to be used in alignment of the camera (130:FIG. 2). Here, the visible light output by the light source21R may be overlapped on the ultraviolet light output by the light source21with use of a half mirror21m. Besides, as a light source for alignment, it may be possible to also use as a light source a wavelength range advantageous for the alignment selectively extracted with use of a filter from a broadband light source such as a halogen lamp or the like. Besides, a HeNe laser light source, a blue LED or the like can also be used. However, when illumination light having a wavelength different from that of ultraviolet light is used, it is necessary to change not only focus correction of the camera130but also aberration correction of the optical system of the camera130according to the wavelength of the illumination light to be used.

As illustrated inFIG. 24A, the product manufactured object30may be manufactured so as to grow downward. A vessel11B is filled with a photosetting liquid resin material10. A transmitting member12B having ultraviolet ray permeability and oxygen permeability is disposed in close contact with the resin material10. The projector20projects the exposure image onto a layer of the resin material10adjacent to a pull-down member13B and solidifies it. A pull-down device17B lowers in a stepwise fashion the pull-down member13B in synchronism with switching of the exposure image in the projector20, and manufactures the product manufactured object30.

As illustrated inFIG. 24B, it may be possible to manufacture the product manufactured object30so as to grow in the horizontal direction. A vessel11C is filled with the photosetting liquid resin material10. A transmitting member12C having ultraviolet ray permeability and oxygen permeability is disposed in close contact with the resin material10. The projector20projects the exposure image onto a layer of the resin material10adjacent to a moving member13C and solidifies it. A moving device17C moves in a stepwise fashion the moving member13C in synchronism with switching of the exposure image in the projector20, and manufactures the product manufactured object30.

In Embodiments 1 to 6, the projector20which operates the mirror for each pixel to form the exposure image is adopted. However, it may be possible to constitute the additive manufacturing apparatus by adopting a liquid crystal projector which uses a liquid crystal shutter as the image forming element.

In Embodiments 1 to 6, the image forming element23is moved by deforming, in the opposite directions, one (41,42) and the other (43,44) of the pair of actuators41to44arranged across the image forming element23. However, it may be possible to adopt a constitution in which the other (43,44) of the actuators41to44are replaced by spring members and one (41,42) of the actuators expand and contract against the biasing force of the spring members.

In Embodiment 1, the alignment of the adjacent projection images TG in the boundary region KR is realized by the mechanical movement of the image forming element23. In Embodiment 2, the alignment of the adjacent projection images TG in the boundary region KR is performed by the data process of the adjacent exposure images. However, it may be also possible to perform the alignment of the adjacent projection images TG in the boundary region KR by properly combining the mechanical movement of the image forming element23and the data process of the exposure images.

In Embodiment 2, the image data of the exposure image is processed such that the entire projection image TG is moved within the projection region TR. However, it may be possible to locally deform and correct the image data of the exposure image. Also, it may be possible to adopt an image process which gives the illuminance gradation to the pixel of the exposure image corresponding to the gap detected in the photographed image or gently resolves the level difference detected in the photographed image.

The present invention can be realized also by a process in which a program for realizing one of more functions of the above embodiments is supplied to a system or an apparatus via a network or a storage medium and one or more processors in the system or the apparatus read and execute the supplied program. Besides, the present invention can be realized also by a circuit (e.g., an ASIC) of realizing one or more functions of the above embodiments.

According to the present invention, it is possible to provide the additive manufacturing apparatus in which a streak pattern and/or a slit in a manufacturing direction are/is difficult to be made on the surface of a product manufactured object in the boundary region of a projection region of the exposure image.