U.S. patent application number 09/449082 was filed with the patent office on 2001-11-22 for method and apparatus for forming three-dimensional laminated product from photo-curable liquid.
Invention is credited to HAGIHARA, SHIGERU, Hizumi, Koki.
Application Number | 20010042942 09/449082 |
Document ID | / |
Family ID | 18489990 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042942 |
Kind Code |
A1 |
Hizumi, Koki ; et
al. |
November 22, 2001 |
METHOD AND APPARATUS FOR FORMING THREE-DIMENSIONAL LAMINATED
PRODUCT FROM PHOTO-CURABLE LIQUID
Abstract
A three-dimensional laminated product forming apparatus and
method for forming a three-dimensional laminated product from a
photo-curable liquid by progressively superposing solid laminae one
on top of another by photo-curing a surface layer of the
photo-curable liquid and converting it to a solid lamina. A product
table is provided on which a three-dimensional solid product is
built up in progressive steps and which is incrementally advanced
into the photo-curable liquid by a specified depth each step. A
liquid surface leveling device works as a capillary to draw up a
photo-curable liquid by capillary action while it is in contact
with the surface of the photo-curable liquid contained in the
container. The device is moved over the surface of the
photo-curable liquid to apply the collected photo-curable liquid
over a three-dimensional laminated product being partly built up on
a product table to form a uniform thickness of a surface layer of
the photo-curable liquid with a surface leveled and smoothed over
the three-dimensional laminated product being partly built up. An
irradiating head forms a beam spot of reactive stimulation on the
surface to cure the surface layer and convert it to a solid lamina
on the three-dimensional laminated product being partly built up as
the three-dimensional laminated product.
Inventors: |
Hizumi, Koki; (Kitakoma-gun,
JP) ; HAGIHARA, SHIGERU; (Kofu-shi, JP) |
Correspondence
Address: |
MARTINE FLEIT
FLEIT KAIN GIBBONS GUTMAN AND BONGINI P L
BRICKEL KEY ONE
520 BRICKEL KEY DRIVE #201
MIAMI
FL
33131-2607
US
|
Family ID: |
18489990 |
Appl. No.: |
09/449082 |
Filed: |
November 24, 1999 |
Current U.S.
Class: |
264/401 ;
264/233; 264/494; 425/174.4; 425/375 |
Current CPC
Class: |
B29C 64/194 20170801;
B29C 64/135 20170801; B29C 41/12 20130101; B29C 71/04 20130101;
B29K 2995/0073 20130101 |
Class at
Publication: |
264/401 ;
264/233; 264/494; 425/174.4; 425/375 |
International
Class: |
B29C 035/08; B29C
041/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 1999 |
JP |
11-367703 |
Claims
What is claimed is:
1. A three-dimensional laminated product forming apparatus for
forming a three-dimensional laminated product from a photo-curable
liquid by progressively superposing solid laminae having a
specified thickness one on top of another, each said solid lamina
being provided by photo-curing a surface layer of the photo-curable
liquid, said three-dimensional laminated product forming apparatus
comprising: a container for holding a photo-curable liquid; a
product table on which a three-dimensional laminated product is
built up in progressive steps, said product table being positioned
in said photo-curable liquid and adapted to be incrementally
advanced into the container step by step, each step being a equal
to a specified thickness for each solid lamina; a liquid surface
leveling device defining a working gap adapted to draw
photo-curable liquid into the device by capillary action to create
a reserve of photo-curable therein, said liquid surface leveling
device being movable horizontally in the container to pass over a
surface of photo-curable liquid when held in said container to form
a smoothed and leveled surface layer of photo-curable liquid over a
three-dimensional laminated product that is being built up on the
product table; and an irradiating head for forming a beam spot of
reactive stimulation in the container that corresponds to the
smoothed and leveled surface layer of photo-curable liquid at the
specified level so as thereby to cure and convert the smoothed and
leveled surface layer as a solid lamina on the three-dimensional
laminated product being built up on said product table.
2. A three-dimensional solid product forming apparatus as defined
in claim 1, wherein said liquid surface leveling device includes at
least one blade defining the gap for drawing the photo-curable
liquid by capillary action into a cavity defined by the at least
one blade.
3. A three-dimensional solid product forming apparatus as defined
in claim 2, wherein said blade is made of a porous material.
4. A three-dimensional solid product forming apparatus as defined
in claim 2, wherein said blade is formed with a plurality of gaps,
each defining a cavity for drawing photo-curable liquid into each
cavity by capillary action.
5. A three-dimensional solid product forming apparatus as defined
in claim 2, wherein said blade is shaped with vertical depending
portions that partly lie below the surface of photo-curable liquid
held in the container when said product table advances
incrementally into said container during the formation of the
laminated product.
6. A three-dimensional solid product forming apparatus as defined
in claim 1, wherein said liquid surface leveling device comprises
at least two blades arranged face to face to define therebetween a
narrow gap through which the photo-curable liquid is drawn by
capillary action.
7. A three-dimensional solid product forming apparatus as defined
in claim 6, wherein each said blade is made of a porous
material.
8. A three-dimensional solid product forming apparatus as defined
in claim 6, wherein each said blade is formed with a number of
holes.
9. A three-dimensional solid product forming apparatus as defined
in claim 6, wherein said liquid surface leveling device further
comprises a porous member interposed between said blades above the
gap to absorb photo-curable liquid.
10. A three-dimensional solid product forming apparatus as defined
in claim 6, wherein at least one of said blades is shaped to partly
depend vertically to be situated below a surface of photo-curable
liquid when said product table is advance into the photo-curable
liquid by said distance equal to said specified thickness of a
solid lamina.
11. A method for forming a three-dimensional laminated product from
a photo-curable liquid by progressively superposing solid laminae
having a specified thickness one on top of another, each said solid
lamina being provided by photo-curing a surface layer of the
photo-curable liquid, said method comprising the steps of: filling
a container with a photo-curable liquid to define a working
surface; advancing a product table, on which a three-dimensional
laminated product is built up in progressive steps, into said
photo-curable liquid incrementally step by step with each step
being a depth equal to said specified thickness of said solid
lamina; drawing photo-curable liquid by capillary action into a
reservoir defined in a liquid surface leveling device; moving the
liquid surface leveling device over the working surface of said
photo-curable liquid in said container to coat and smooth said
photo-curable liquid over a three-dimensional laminated product
that is being built up on said product table; and irradiating a
beam spot of reactive stimulation on said smoothed and leveled
surface layer of said photo-curable liquid at said working surface
to cure and convert said smoothed and leveled surface layer as a
solid lamina on said three-dimensional laminated product being
built up on said product table.
12. A method as defined in claim 11, wherein the reservoir in said
liquid surface leveling device includes at least a blade.
13. A method as defined in claim 12, wherein said blade is made of
a porous material.
14. A method as defined in claim 12, wherein said blade is formed
with a number of holes.
15. A method as defined in claim 2, including the step of sinking
portions of said blade below the working surface of said
photo-curable liquid when said product table is incrementally
advance into said photo-curable liquid by said distance equal to
said specified thickness of said solid lamina.
16. A method as defined in claim 11 wherein the irradiation is
effected by a He--Cd laser having a wavelength of about 325 nm.
17. A method as defined in claim 11 including the further step of
removing the three dimensional laminated product from the
photo-curable liquid of the container, washing the removed product,
and subjecting the washed product to a secondary hardening by
irradiating with ultraviolet radiation.
18. A method as defined in claim 11 wherein only the portions of
the working surface are irradiated which correspond to the
perimeter of the three dimensional laminated product being built
during the formation of each lamina, and the entire portion of the
working surface corresponding to the entire cross-section of the
three dimensional laminated product is irradiated for the first and
last lamina and for each successive X lamina, where X is a whole
integer between 6 and 10.
19. A method as defined in claim 11, including the further step of
absorbing the photo-curable liquid in the reservoir into a porous
body.
20. A method as defined in claim 11 wherein the entrance to the
reservoir is set at approximately 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method and an apparatus
for forming a three-dimensional laminated product, such as, a model
or core useful for investment casting of an intended ornamental
jewelry craft product.
[0003] 2. Description of the Related Art
[0004] In recent years, it has been known to form a
three-dimensional product by successively superposing a number of
photo-cured laminae of stratified cross sections of the
three-dimensional product one on the top of another. Specifically,
a photo-cured lamina is formed on previously photo-cured laminae by
scanning and curing a specified thickness of surface layer of a
photo-curable liquid by laser energy, building up the
three-dimensional product. One of such methods and apparatus for
forming three-dimensional products from a photo-curable liquid is
known from, for instance, Japanese Unexamined Patent Publication
No. 56-144478.
[0005] In order to introduce a fresh liquid of a quantity necessary
to provide a specified thickness of surface layer of the
photo-curable liquid, which will to be formed as a photo-cured
lamina on the previously superposed photo-cured laminae, the
under-building product needs to be moved precisely by a distance
equal to the specified thickness in progress steps away from the
working surface level of the photo-curable liquid at which a
surface layer of the fresh liquid is irradiated with laser energy.
In practice this has proven difficult. For example, for forming the
surface layer of the photo-curable liquid with a precisely
controlled thickness, as described in, for instance, European
Patent Specifications EP.0171069B1 and EP 0535720B1, the
under-building product is initially moved down away from the
specified working surface to a level beyond the specified working
surface level, and then, moved back to the specified working
surface level in order to accomplish each stepwise adjustment
during the process of making the article being built.
Alternatively, as described in, for instance, Japanese patents Nos.
26195445 and 2715649, a fresh liquid spray mechanism is provided to
spray a fresh liquid so as to form a precise thickness of surface
layer of a photo-curable liquid on an under-building product after
moving down the under-building product away from the specified
working surface by a distance equal to the specified thickness.
[0006] While employing an initial increment of movement of the last
formed lamina away from the specified working surface to a level
beyond the specified working surface level enables the apparatus
for building a three-dimensional product by photo-curing to be
simple in construction and mechanism and compact in overall size,
however, it causes a somewhat tangled problem of spending a long
time before completely building a three-dimensional product. That
is, the photo-curable liquid is governed in fluidity by its
relatively high viscosity and surface tension, and therefore, a
relatively long time is required to introduce a precisely
controlled quantity of the fresh liquid for providing a specified
thickness of surface layer of the photo-curable liquid for the next
processing step. In addition to a long time that is spent before
introduction of a precisely controlled quantity of the fresh
liquid, a time is required to move back the working surface to the
specified working surface level after the introduction of a
precisely controlled quantity of the fresh liquid. Further,
application of laser energy onto a surface layer of the
photo-curable liquid must wait for a time until the surface layer
is entirely leveled. In consequence, a long working time is
necessary to complete a single photo-cured lamina, which causes a
rise in manufacturing costs. Since the photo-curable liquid
transforms from a fluid to a solid by means of photochemical
reaction, such as, a radical reaction and a cationic reaction, the
photo-curable liquid itself has a somewhat restricted effective
life, which causes a large quantity of photo-curable liquid of no
direct use, and hence leads to a rise in manufacturing costs.
[0007] On the other hand, while spraying a fresh liquid by means of
the fresh liquid spray mechanism to form a precise thickness of
surface layer of a photo-curable liquid on an under-building
product reduces a time required to introduce a precisely controlled
quantity of the fresh liquid and level a surface layer, and
realizes miniaturization of a fluid container in which the
photo-curable liquid is accommodated, the fresh liquid spray
mechanism has to be equipped not only with various associated parts
such as a nozzle, mesh screen, a rotary shaft, a brush and a water
wheel which makes the apparatus bulky, but also a secondary fluid
container in which a photo-curable liquid to be sprayed must be
provided. Further, there is the necessity of installing a surface
level adjusting mechanism for adjusting a level of the surface
layer after spraying a fresh liquid. Such a surface level adjusting
mechanism is complicated in structure and expensive, which leads to
a rise in manufacturing costs.
SUMMARY OF THE INVENTION
[0008] It is a primary object of the invention to provide a method
an apparatus for forming a three-dimensional laminated product from
a photo-curable liquid by step-wise photo-curing of laminae.
[0009] Another object of the invention is to provide a
three-dimensional laminated product forming apparatus equipped with
a liquid surface leveling device working as a capillary which draws
up a reserve of photo-curable liquid therein and applies it over a
laminated product that is being built up so as to form a uniform
thickness of a surface layer of the photo-curable liquid with a
working surface leveled and smoothed.
[0010] The foregoing objects are accomplished by providing a
three-dimensional laminated product forming method and apparatus
for forming a three-dimensional laminated product from a
photo-curable liquid by progressively superposing solid laminae
having a specified thickness, one on top of another, each solid
lamina being provided by photo-curing a surface layer of the
photo-curable liquid and converting it to a solid lamina. The
three-dimensional laminated product forming apparatus comprises a
product table on which a three-dimensional solid product is built
up in progressive steps, said product table being sunken in a
reservoir of photo-curable liquid by a distance equal to the
specified thickness of the solid lamina in each said step; and a
liquid surface leveling device which works with a capillary effect
to collect or draw up a reserve of photo-curable liquid while it is
in contact with the surface of the photo-curable liquid contained
in a container which is placed on a container table. The leveling
device is moved over the surface of the photo-curable liquid to
apply the collected photo-curable liquid over a three-dimensional
laminated product, that has been partly built up on a product table
and stepped down for the next lamina, so as to form a uniform
thickness of a surface layer of the photo-curable liquid with a
surface leveled and smoothed over the three-dimensional laminated
product that has been partly built up. An irradiating head forms a
beam spot of reactive stimulation (ultraviolet energy) on the
smoothed and leveled surface layer of the photo-curable liquid so
as thereby to cure the surface layer, and convert it to a solid
lamina superposing on the three-dimensional laminated product that
is partly built up as the three-dimensional laminated product.
[0011] According to the three-dimensional solid product forming
apparatus and method, it is enabled to form a specified thickness
of a surface layer of a photo-curable liquid over a
three-dimensional product having been partly building up. The
surface layer leveling device comprises a pair of surface leveling
blades having an entrance that is set for a predetermined opening
so that it is arranged as to work as a capillary. The structure is
simple and the driving mechanism for it is also simple and
inexpensive. As a result, the three-dimensional solid product
forming apparatus is made small in overall size, operates quickly
and is provided at low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing and other objects and features of the
invention will be made clear when reading the following description
in accordance with a preferred embodiment thereof in conjunction
with the accompanying drawings in which:
[0013] FIG. 1 is a side view partly broken away of a
three-dimensional laminated product forming apparatus in accordance
with a preferred embodiment of the invention;
[0014] FIG. 2A is a front view of a liquid surface layer leveling
unit that is installed in the three-dimensional laminated product
forming apparatus shown in FIG. 1;
[0015] FIG. 2B is a side view of the liquid surface layer leveling
unit that is installed in the three-dimensional laminated product
forming apparatus shown in FIG. 1;
[0016] FIG. 3 is a side view of a liquid surface leveling device of
the liquid surface layer leveling unit shown in FIGS. 2A and
2B;
[0017] FIGS. 4A, 4B and 4C are front, top and cross-sectional views
of a ring model designed by CAD, respectively;
[0018] FIGS. 5A and 5B are explanatory top and cross-sectional
views of part of a three-dimensional laminated product that is
being built up by photo-curing; and
[0019] FIGS. 6A-6C are side schematic views showing various
variants of the liquid surface leveling device shown in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Referring to the drawings in detail, in particular, to FIG.
1 which shows a computer controlled laminate molding apparatus 100
specialized for forming a three-dimensional laminated product, such
as, a prototype of jewelry rings, from a photo-curable liquid by
photo-curing. The computer controlled laminate molding apparatus
100 has a housing 2 provided with a stationary bottom platform 4 on
which a laminated three-dimensional product building unit 200A is
installed, and a stationary top platform 6 to which a photo-curing
unit 200B is installed, both platforms being fixedly mounted to the
housing 2. The laminated product building unit 200A includes a
movable container table 22 on which a container 26 filled with a
photo-curable liquid PCL, such as, a photo-curable resin, is
placed, a movable product table 24 on which a three-dimensional
laminated product is built up from the photo-curable liquid PCL in
the container 26, and a liquid surface layer leveling unit 28 which
is detachably mounted on the movable container table 22. The
movable container table 22 is guided on a guide post 22b fixedly
supported on the stationary platform 4 and moved up and down in a
vertical direction by a vertical position control mechanism 22a to
adjust a vertical position of the container 26, and hence, in
particular, a vertical position of the top surface of the
photo-curable liquid PCL in the container 26, when required. The
movable product table 24 is guided on guide post 24b and moved down
by a vertical position shift mechanism 24a so as to shift a working
surface of the top photo-cured laminae in vertical position. The
term "working surface" used herein shall mean and refer to the
surface of liquid at which a spot of reactive stimulation is
focused on the photo-curable liquid to cure the photo-curable
liquid and convert it to a solid material. The working surface is
adjusted incrementally at a specified level by shifting down the
movable product table 24 in steps by a vertical distance of
preferably from approximately 30 to approximately 70 microns, that
is, substantially equal to a predetermined thickness of surface
layer of the photo-curable liquid is to be cured and converted to a
solid lamina over a solid body consisting of photo-cured laminae
that form part of a desired final three-dimensional laminated
product. The liquid surface layer leveling unit 28, which will be
described in detail later in connection with FIG. 2, develops and
forms precisely the specified thickness of surface layer of the
photo-curable liquid over the solid body consisting of photo-cured
laminae that form part of the desired three-dimensional laminated
product that is being built up from the photo-curable liquid
PCL.
[0021] The photo-curable resin employed as the photo-curable liquid
PCL in the preferred embodiment of the invention has a composition
such that it can be cured by ultraviolet energy of less than 400 nm
wave length. Many such compositions are known to those skilled in
the art, and the composition may consist, for example, of acrylate
resins and/or epoxy resins. For purposes of the present invention,
the photo-curable liquid PCL needs to have a specific gravity of
about 1.2, a viscosity of about 1.4 Pa.multidot.S and a molecular
weight of from about 200 to about 700. The composition may also
include a hardener and/or a photo-curing initiator, as are known,
and is of generally low viscosity and a relatively high shrinkage
rate.
[0022] The photo-curing unit 200B includes a beam irradiation
focussing head 32 for applying a spot of reactive stimulation, such
as, an He--Cd laser having a wavelength of 320 nm, to the
photo-curable liquid PCL at a specified working surface, an X-Y
position control mechanism such as an X-Y digital plotter 34 that
moves the beam irradiation head 32 in two horizontal directions
intersecting each other, and a laser light source 36. In the
preferred embodiment, a multiple mode type of laser is used that
has a wavelength of 325 nm and generates 5 to 10 mW output. In the
case where a three-dimensional laminated product has a minute
shape, it is preferable to employ a single mode type of laser
having 3 to 10 mW output which is easily focused since it does not
encounter waveform disorder. Laser rays generated by the light
source 36 are transmitted to the beam irradiation head 32 by way of
light guide means 38 and focused as a beam spot on the
photo-curable photo medium PCL at the working surface. In order to
transmit the laser rays with a high efficiency, and in a high level
of safety, the light guide device employs a step-index type of
optical fiber 38a and a flexible metal tube 38b in which the
optical fiber 38a is protected. Because the step index type of
optical fiber has apprehensions of causing waveform disorder due to
repeated internal refraction of laser rays in the optical fiber and
causing diffusion of laser rays after an exit end of the optical
fiber, in the case of a minutely shaped three-dimensional laminated
product, a single step index type of optical fiber, or otherwise a
grated index type of optical fiber, may be preferably employed. In
order to apply photo-curing laser energy generated by the laser
source 36 onto a surface layer of the photo-curable liquid PCL, the
light source 36 is provided with a plurality of high speed
mechanical shutters (not shown) which are controlled in operation
by actuators so as to admit laser energy to enter the optical fiber
and shut off it from entering the optical fiber. In order to
provide a laser beam of sufficient strength for curing a surface
layer of the photo-curing liquid, the beam irradiation head 32 is
provided with a focusing lens (not shown) operative to form a
specified diameter of laser beam spot on the surface layer of the
photo-curable liquid. The laser beam spot has a diameter of
approximately 80 microns and a radiation strength of approximately
200 W/cm.sup.2 at the working surface which is sufficient to cure a
predetermined thickness of surface layer of the photo-curable
liquid PCL. The working surface level is monitored by means or
surface level sensor 30. Accordingly, the working surface level the
working surface of the photo-curable liquid PCL is adjusted at a
specified level with respect to the beam irradiation head 32 by
moving up or down the movable container table 22.
[0023] Referring to FIGS. 2A and 2B, the surface layer leveling
unit 28 includes a liquid surface leveling device 50 that is driven
in a direction X or the reverse direction Y by means of a drive
mechanism 60 to level the surface layer of the photo-curable liquid
PCL, as will be described in detail later. The liquid surface
leveling device 50 comprises a pair of leveling blades 52 and an
attachment 54 to which the leveling blades 52 are detachably
secured at opposite sides by set screws 54a. The attachment 54 is
an integral part of a blade mount beam 56. The drive mechanism 60
includes a pair of movable blade supports 62 on which the blade
mount beam 56 is supported. Each blade support 62 comprises a base
block 64 to which a pair of L-shaped support members 66 are secured
by set screws 66a so as to form a space 66b therebetween for
receiving the blade mount beam 56. The blade support 62 is provided
with a blade adjustment screw 65 for adjusting a vertical level of
the leveling blades 52 with respect to the working surface of the
photo-curable liquid PCL. The base block 64 at its lower portion is
provided with a guide slider 68 which slides on a guide rail 70
secured to an upright side wall 72 detachably secured to the
container table 22. The blade support 62 is integrally formed with
an arm 63 extending inwardly from the base block 64. The drive
mechanism 60 further includes a reversible motor 80 secured to the
container table 22. As shown in FIG. 2B, the upright side walls 72
at their opposite end portions support a drive shaft 82a and an
idle shaft 82b. The motor 80 is connected to the drive shaft 82a by
a belt 80a to transmit rotation of the motor 80 to the drive shaft
82a. Two timing belt 84 are mounted between the drive shaft 82a and
the idle shaft 82b with appropriate tension. The arms 63 of the
blade supports 62 are secured to the timing belts 84, respectively.
When the motor 80 is actuated to rotate in an counterclockwise
direction as viewed in FIG. 2B, the blade supports 62 with the
liquid surface leveling device 50 supported thereby are moved in a
direction X along the guide rail 70. On the other hand, when the
motor 80 is reversed to rotate in a clockwise direction as viewed
in FIG. 2B, the blade supports 62 with the liquid surface leveling
device 50 supported thereby are moved back in a reverse direction Y
along the guide rail 70.
[0024] The drive mechanism 60 further includes position limiting
means 90 comprising a leg member 90a secured to the base block 64
of the blade support 62, a stationary limit sensor 90b secured to a
guide rail 90d that is installed to the upright side wall 72, and a
movable limit sensor 90c mounted on the guide rail 90d for slide
movement. Each of the limit sensors 90b and 90c is operative to
stop the motor 80 when detecting the leg member 90a. By sliding the
movable limit sensor 90c, the extent of movement of the surface
layer leveling unit 28 is regulated.
[0025] FIG. 3 shows the liquid surface leveling device 50 in detail
by way of example. The liquid surface leveling device 50 includes a
pair of the leveling blades 52 which are secured to the attachment
54 by the set screws 54a and separated at their distal edges by a
separation of, for example, preferably approximately one (1) mm
from each other so as to form therebetween a narrow 1 mm space 51a
that provides the leveling blades 52 with a capillary action. When
the liquid surface leveling device 50 is moved down until the
leveling blades 52 at their lower distal edges are brought into
contact with the surface of the photo-curable liquid PCL, the
leveling blades 52, because of their spacing and construction, work
as a capillary to draw up the photo-curable liquid PCL into the
space 51a by the aid of surface tension of the photo-curable liquid
PCL to establish a small reservoir of PCL liquid above the gap 51a,
as shown in FIG. 3. Since when the product table 24 is stepped down
below the photo-curable liquid by a distance equal to the specified
thickness of one cross-sectional stratum of the three-dimensional
solid product, the surface of the photo-curable liquid does not
always flow and cover evenly over the three-dimensional laminated
product that is being built up due to the surface tension,
liquidity and viscosity of the photo-curable liquid. Consequently,
when the liquid surface leveling device 50 moves in one of the
directions X and Y with the leveling blades 52 at their lower
distal edges remaining in contact with the liquid surface, the
collected reserve of photo-curable liquid is drawn and flows out
from the space 51a between the leveling blades 52 to flow and cover
over the three-dimensional laminated product LP, thereby
immediately forming a surface layer of the photo-cured liquid
having the specified thickness ready for photo-curing. While the
liquid surface leveling device 50 moves, the leveling blades 52 at
their lower distal edges smooths and levels the surface of the
photo-curable liquid to form a uniform thickness of a surface layer
over the three-dimensional laminated product, so as to enable
immediate cure of the surface layer and conversion to a solid
lamina having the specified thickness.
[0026] The three-dimensional solid product building unit 200A and
photo-curing unit 200B are numerically controlled in operation in
accordance with three-dimensional data of a design of a
three-dimensional solid product provided by the aid of a computer
system 300. Such systems are well known to those skilled in the
art.
[0027] The following description will be directed to the process of
producing a three-dimensional solid product which is formed by the
method and apparatus of the invention and used as a model for
producing a mold for casting rings by way of example.
[0028] Referring to FIGS. 4A-4C which are side, plane and
cross-sectional views of a model M that is three-dimensionally
designed by the computer system 300 by the use of a known modeling
program, CAD data is translated into CAM data which is
three-dimensional numerical data of specified angular positions of
points (P1, P2, . . . Px) of inner and outer contours Ma and Mb for
a number of cross-sectional strata of the model M.
[0029] As shown in FIG. 5A and 5B, when the three-dimensional solid
product producing process is started according to the CAM data, the
movable table 24 is moved down until it sinks into the
photo-curable liquid PCL away from the working surface WS by a
distance which is equal to the specified thickness of
cross-sectional strata of the model T, and then the movable
container table 22 is moved up or down according to a signal
provided by the surface level sensor 30 so as to position the
working surface WS of the photo-curable liquid PCL at the specified
level with respect to the beam irradiation head 32 and
subsequently, the liquid surface leveling unit 28 is moved over the
working surface WS of the photo-curable liquid PCL to form a
surface layer and smooth over the surface layer. Subsequently, the
X-Y digital plotter 34 is controlled by the computer 300 to move
the beam irradiation head 32 according to the CAM data. Immediately
when the X-Y digital plotter 34 moves to locate the beam spot BS in
a position P(1)1 on the working surface WS, the shutter is opened.
Thereafter, the X-Y plotter 34 moves linearly to pass through
positions P(1)2 . . . P(1)X at a constant speed between
approximately 300 mm/min and 1,000 mm/min, desirably at a constant
speed of 800 mm/min, to scan the surface of the photo-curable
liquid PCL along a polygonal track. As a result, the area of the
surface layer of the photo-curable liquid PCL that is traversed by
the beam is progressively cured in the form of a polygon, which is
almost similar to a circle, having a width equal to the diameter of
the beam spot BS and converted to a polygon-shaped solid loop
having the same thickness as the specified thickness of the
cross-sectional stratum Ln of the model M. The polygonal solid loop
LMa-1 forms an inner contour Ma of the first for the first
cross-sectional strata L1 of the model M. As soon as the bean spot
BS reaches the starting position P(1)1 passing through a position
P-(1)X, the shutter is closed. Subsequently, the X-Y digital
plotter 34 is moved outwardly to shift the beam irradiation head 32
by a distance equal to the diameter of the beam spot BS on the
working surface WS, and the shutter is opened. Thereafter, the X-Y
plotter 34 moves linearly to pass through positions P(1)2 . . .
P(1)X at the constant speed to scan the working surface WS of the
photo-curable liquid PCL, so as thereby to progressively cure the
surface layer of the photo-curable liquid PCL in the form of a
polygon having the same width as the diameter of the beam spot BS
and convert it to a polygon-shaped solid loop having the same
thickness as the specified thickness of the cross- sectional
stratum L of the model M. The polygonal solid loop LMb1 forms an
outer contour Mb of the first for the first cross-sectional strata
L1 of the model M. These polygonal solid loops Lma1 and LMb1
constitute a first solid lamina equivalent to the first
cross-sectional strata L1 of the model M.
[0030] When the beam spot BS reaches the starting position P(1)1,
and the shutter is closed, the movable table 24 is moved down until
the top surface of the polygonal solid loops LMa1 and LMb1 as a
solid lamina sinks into the photo-curable liquid PCL away from the
working surface WS by the same distance as the specified thickness
T of cross-sectional strata of the model M. At this time, the
movable container table 22 may be moved up or down according to a
signal provided by the surface level sensor 30 so as to position
the working surface WS of the photo-curable liquid PCL at the
specified level with respect to the beam irradiation head 32, if
some adjustment is necessary. Subsequently, the liquid surface
leveling unit 28 is moved back over the working surface WS of the
photo-curable liquid PCL to form a surface layer over the polygonal
solid loops LMa1 and LMb1 and smooth over the surface layer. In the
same manner as described above, the X-Y digital plotter 34 is moved
to locate the beam spot BS in a position P(2)1 over the working
surface WS of the photo-curable liquid PCL and smooth over the
surface layer and scan the surface of the photo-curable liquid PCL
along a polygonal track, so as thereby to form polygonal solid
loops Lma2 and is superposed LMb2 as second solid lamina equivalent
to the second cross-sectional strata L2 of the model M over the
previously formed first solid lamina. The same process is
progressively performed according to the CAM data to form polygonal
solid loops LMan and LMbn as solid laminae equivalent to
cross-sectional stratum Ln of the model M.
[0031] By repeating the process the same times as the number of
cross-sectional stratum of the model M to superpose the same number
of polygonal solid loops as the number of cross-sectional stratum
of the model M one top of the another, a three-dimensional
laminated product is built up as a mold for rings on the table 24.
The entire surface space between the inner and outer loops is
solidified every 6 to 10 laminae to give structure to the
product.
[0032] When the product has been completely built-up, it is removed
from the table 24, and washed with ultrasonic cleaning for about 5
minutes to remove liquid resin. Use of ethanol and a detergent may
also be required to remove the liquid resin. Next, the product or
model is subjected to secondary hardening under ultraviolet ray
treatment, to solidify the entire model.
[0033] Various variants of the liquid surface leveling device 50
may be employed as schematically shown in FIGS. 6A through 6C.
Liquid surface leveling device 50a shown in FIG. 6A comprises a
pair of double walled leveling blades 52a detachably secured to an
attachment 54. Each double-walled leveling blade 52a consists of
outer and inner wall sections separated at a constant distance to
provide a crevice or gap 51b which works as a supplementary
capillary. Further, the double-walled leveling blades 52a are
secured to the attachment 54 by set screws 54a and separated at
distal edges by a separation of, for example, preferably
approximately 1 from each other to form therebetween a narrow space
51a which works as a primary capillary. When the double walled
leveling blades 52a are brought into contact with the surface of
photo-curable liquid PCL, the liquid surface leveling device 50a
draws up the photo-curable liquid PCL into the space 51a and the
crevice 51b by the aid of its own capillary action and surface
tension of the photo-curable liquid PCL. This liquid surface
leveling device 50a is preferable to draw up and hold a larger
quantity of the photo-curable liquid PCL therein.
[0034] FIG. 6B shows another liquid surface leveling device 50b
which comprises a pair of surface leveling blades 52b are secured
to an attachment 54 by set screws 54a and separated at lower distal
edges by a separation of, for example, preferably approximately 1
from each other to form therebetween a narrow space 51b which works
as a primary capillary. Each surface leveling blade 52b is formed
with opposite end extensions 5 which is always positioned below the
surface of the photo-curable liquid PCL to draw up the
photo-curable liquid PCL into the space 51b while the surface
leveling blades 52b are at least in contact with the surface of
photo-curable liquid PCL. This liquid surface leveling device 50b
is preferable to draw up the photo-curable liquid PCL and fill the
space 51b with it quickly.
[0035] FIG. 6C shows still another liquid surface leveling device
50c which comprises a pair of surface leveling blades 52c separated
at their distal edges by a specified separation of about 1 mm to
form therebetween a narrow space 51c, and a porous pad 59, such as,
a sponge pad or a foam pad, is interposed between the surface
leveling blades 52c with an effect of actively holding or retaining
the photo-curable liquid drawn up by capillary action, and
supplying it over a laminated product that is being built up in the
manner described. Further, the surface level blades 51c may
themselves be made of porous material.
[0036] The liquid surface leveling device may take any form of
combinations of the leveling blades 50, 50a-50c shown in FIGS. 3
and 6A through 6c.
[0037] While the present invention has been described in terms of a
preferred embodiment, those skilled in the art recognize that the
present invention can be practiced with various changes and
modifications without departing from the scope of the claims.
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