Plastic and nonmetallic article shaping or treating: processes – Stereolithographic shaping from liquid precursor
Reexamination Certificate
1999-07-09
2001-01-30
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Stereolithographic shaping from liquid precursor
C425S174400, C425S375000, C700S120000
Reexamination Certificate
active
06180050
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to a solid model creation apparatus for creating models having three-dimensional shapes using photocurable resin.
TECHNICAL BACKGROUND
A great many inventions are known with respect to solid model creation apparatuses, these including, for example, Japanese Patent No. 1827006. Conventional solid model creation apparatuses generally employ as light source a gas laser generator outputting ultraviolet laser light.
Gas laser generator size is fairly large (e.g., 150 cm×30 cm×30 cm), and consequently solid model creation apparatus main body size is likewise correspondingly large. In addition, the gas laser generator is itself expensive, and moreover, depending on the type of generator, a 200 V power supply and a water cooling apparatus (chiller) may well be required. Accordingly, the price of a conventional solid model creation apparatus is extremely high (e.g., several tens of millions of yen).
Accordingly, the object of the present invention is to provide a solid model creation apparatus that is small in size and inexpensive.
DISCLOSURE OF THE INVENTION
The solid model creation apparatus with which the present invention is concerned is equipped with a tank that holds a photocurable resin solution, an exposure region set within the photocurable resin solution in the tank, an exposure apparatus that irradiates light onto this exposure region, and a control apparatus that controls the exposure apparatus so as to cure selected pixel(s) within the exposure region. The exposure region may be defined as a two-dimensional set of a multiplicity of pixels fine enough to satisfy requirements for dimensional accuracy in a solid model. The exposure apparatus possesses at least one light spot generator that is capable of being switched on and off and that irradiates the exposure region with a light spot when turned on. The size of each light spot with which the exposure region is irradiated is larger than each pixel in the exposure region. Furthermore, the exposure apparatus scans the exposure region with the light spot generator, and throughout the course of this scanning the control apparatus turns on the sum total plurality of light spot generators present at locations permitting irradiation of the selected pixel with the light spot.
“Sum total plurality” as used here is meant to include not only simultaneous irradiation of the same pixel with a plurality of light spots from a plurality of physically different light spot generators, but also repeated irradiation of the same pixel with light spots generated by a single physical light spot generator at different times during scanning.
The size of the light spot irradiated on the exposure region from a light spot generator in the solid model creation apparatus of the present invention is not as small as an exposure region pixel, but rather is larger than the pixel. Furthermore, because exposure of each pixel is carried out in multiple fashion using a sum total plurality of light spots, the output of each light spot generator may be relatively low. It is therefore not necessary that a conventional large and expensive gas laser generator be employed as light source in the light spot generator, it being possible to employ a small and inexpensive solid-state luminescent element such as an LED therefor. As a result, it is possible to provide a solid model creation apparatus that is far more inexpensive than was the case conventionally (e.g., on the order of several millions of yen as opposed to several tens of millions of yen, as was the case conventionally).
From the standpoint of exposure efficiency, it is desirable that there be a plurality of light spot generators. In such a case, in order to permit multiple exposure as described above, it is desirable that the apparatus be constituted such that the light spots from the plurality of light spot generators are arrayed in the primary scan direction at a first pitch (typically the pixel pitch) which is smaller than the diameter of the light spots at the exposure region, and the exposure region is scanned in the secondary scan direction with that plurality of light spots. Furthermore, it is still more desirable that a multiplicity of light spots be arrayed across the entire length of the exposure region in the primary scan direction.
As described above, in arraying a plurality of light spots at a small first pitch, a plurality of light spot generator subarrays, each comprising two or more light spot generators lined up in a single row in the primary scan direction at a second pitch which is the same as or greater than the light spot diameter may be provided, and these light spot generator subarrays may themselves be arranged in the secondary scan direction with a displacement therebetween in the primary scan direction which is equal to the aforesaid first pitch. Adoption of such an arraying method makes it possible for large light spot generators to be arrayed in the primary scan direction at the first pitch even when the size of each of those light spot generators is much larger than the first pitch.
In order to permit the aforementioned multiple exposure, a control apparatus may control the exposure apparatus as follows. To wit, the control apparatus first receives data indicating the cross-sectional profile of a solid model and expands the cross-sectional profile by applying a prescribed offset to this data. Next, while light spot generator(s) are scanning the exposure region, the control apparatus turns on light spot generator(s) for which the center of the light spot(s) therefrom are located at respective pixels contained within the expanded cross-sectional profile. A method incorporating this offset expansion processing makes it possible to carry out effective multiple exposure of all pixels within the cross-sectional profile of a solid model (in particular, not just the pixels at the interior of the profile but also pixels in the vicinity of the outline thereof) by merely carrying out a simple light spot drive method wherein respective light spot generators are turned on and off in accordance with the value of the pixel at the center of the light spot therefrom.
As mentioned above, a solid-state luminescent element such as an LED may be employed as light source in the respective light spot generators. It is desirable that the apparatus permit a constitution wherein an optical fiber is connected to each LED, and that a light spot from the tip of that optical fiber irradiate the plane of exposure. It is further desirable that the apparatus permit a constitution wherein a GRIN lens (gradient index lens; graded refractive index lens) is arranged at the end of the tip of the optical fiber, and the image of the tip of the optical fiber is formed on the exposure region. Such a constitution will make it possible to produce a light spot having a small diameter corresponding to the diameter of the optical fiber (e.g., 0.5 mm). Use of a light spot on this order of smallness will permit creation of solid models having dimensional accuracies adequately permitting practical use for typical solid model creation applications. In addition, the solid model creation apparatus of the present invention possesses an extremely large practical advantage because price is lowered to the extent that it is of a different order of magnitude in comparison with conventional solid model creation apparatuses employing gas lasers, and because the apparatus is also made small in size.
It is desirable that the LED serving as light source emit light of wavelength as high in energy (i.e., as short in wavelength) as possible, and from this standpoint it is desirable that a blue LED be used, or that an ultraviolet LED be used if one is available.
Moreover, the LED used as light source may be integral with the light spot generator (exposing head) which scans the exposure region such that it moves together with the exposing head, or the apparatus may be constituted such that the LED is secured at a location removed some distance from the exposing head and is linked to the ex
Arai Mahito
Nakagawa Takeo
Niino Toshiki
Gallagher & Lathrop
Lathrop David N.
Tentoni Leo B.
The Institute of Physical and Chemical Research
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