JP3419724B2 - Liquid level measurement device and three-dimensional molding device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a liquid level of a liquid medium used in three-dimensional modeling, and a three-dimensional modeling apparatus having a liquid level measuring mechanism.

[0002]

2. Description of the Related Art In recent years, U.S. Pat. No. 4,575,33 entitled "Apparatus for producing three-dimensional objects by three-dimensional modeling".
A "three-dimensional modeling" system as described in No. 0 has been put into practical use. Basically, stereolithography involves the formation of complex three-dimensional plastic parts by successively curing multiple thin layers of a polymerizable liquid medium on top of each layer, and combining all the thin layers to form the entire part. This is a method for automatic production. Each polymerized and cured layer is essentially a thin cross-sectional layer of the desired three-dimensional object. In this technique, parts are literally created in a bath containing a polymerizable liquid medium. This method is extremely effective for quickly turning a design concept into a concrete shape and making a model of a prototype. Furthermore, complex parts can be manufactured quickly without the need for tools.
Since this system uses a computer to generate a cross-sectional pattern, it can be easily connected to a CAD / CAM system.

The preferred polymerizable liquid medium is one that cures with an ultraviolet beam at a rate high enough to make it a working model building material. The liquid that was not used for polymerization at the time of manufacturing the parts is left in the tank as it is and used for manufacturing the parts thereafter. The ultraviolet beam emitted from the laser forms a small high-intensity ultraviolet beam beam spot that moves in a predetermined pattern on the liquid surface of the liquid medium by an XY scanning device using a galvanometer mirror. The scanning device is driven by computer generated vectors and the like, and precise and complex patterns are easily created by this technique.

The three-dimensional modeling system includes a laser scanning device,
It includes a tank for containing the polymerizable liquid medium, an object support stand that can be moved up and down in the tank, and a control computer. The system is programmed to automatically make plastic parts by forming one thin section at a time and building the desired three-dimensional object layer by layer.

In a typical stereolithography procedure, a thin layer of a highly viscous, curable polymerizable liquid medium is applied over an already cured layer, and the thin layer of polymerizable liquid medium is only smoothed by gravity. After a sufficient amount of time has passed, the computer-controlled beam travels over the thin layer, allowing the polymerizable liquid medium to cure sufficiently to allow subsequent layers to be applied thereon. The waiting time for the thin layer to become smooth depends on several factors such as the viscosity of the polymerizable liquid medium and the layer thickness.

Usually, the hardened layer is supported on a vertically movable object support, and a distance equal to a desired layer thickness is set so that a highly viscous polymerizable liquid medium is filled on the hardened layer.
It is submerged below the bath of the polymerizable liquid medium. When the liquid level is flat, the layer is ready for beam curing.

Details of stereolithography are set forth in US Pat. No. 4,575,330 and in the pending US patent applications listed below.

US Patent Application No. 339,246 "Reduction of Curl in Stereolithography" (filed April 17, 1989) US Patent Application No. 331,664 "Production of high resolution three-dimensional objects by stereolithography. US Patent Application No. 183,015 “Method and apparatus for producing three-dimensional objects by three-dimensional modeling” (filed April 18, 1988) US Patent Application No. No. 182,801 “Method and apparatus for producing three-dimensional objects by three-dimensional modeling” (filed on April 18, 1988) US Patent Application No. 268,429 “method for curing partially polymerized parts” (Filed Nov. 8, 1988) U.S. Patent Application No. 268,428 "Method for Making Partially Polymerized Parts" (1988 1
Filed Jan. 8) U.S. Patent Application No. 268,408 "Method for draining partially polymerized parts" (19
(Filed on November 8, 1988) US Patent Application No. 268,8
No. 16, "Apparatus and Method for Contouring a Beam"
(Filed Nov. 8, 1988) US Patent Application No. 26
No. 8,907, "Apparatus and method for correcting drift in three-dimensional modeling" (filed on November 8, 1988), U.S. Patent Application No. 268,837, "apparatus and method for calibrating and standardizing three-dimensional modeling apparatus" (1988) (Filed on Nov. 8) U.S. patent application no.
Filed on Mar. 26) U.S. patent application number 365,444 "Integrated three-dimensional modeling" (filed Jun. 12, 1989) U.S. patent application number 265,039 "apparatus and method for measuring and controlling liquid level" (Application October 31, 1988) The present invention utilizes an apparatus for measuring a liquid level, particularly an apparatus for measuring a liquid level of a liquid medium used in a three-dimensional modeling apparatus.

Many scientific experiments and industrial applications require liquid level measurements. As used herein, "liquid level" means the altitude of the liquid surface in a gravitational field or other accelerating coordinate system. There are many possibilities for the liquid that forms this liquid level, and it can be the sea, the gasoline in a gasoline tank of an automobile, or the liquid chemical in a test tube.
To measure the level of these liquids, dip sticks,
Various means have been adopted for many years, such as painted wire on the side of the pile, marking on the side of the test tube, and float. However, there is a need for a device that can measure liquid level very accurately and reliably. Devices of this type are particularly useful in industrial applications and can be combined with liquid level maintenance devices such as pump plungers, diaphragms and other regulators to maintain the liquid level at the desired altitude.

In particular, the three-dimensional modeling device requires extremely precise control of the liquid level of the liquid medium used. Charles. W. U.S. Pat. No. 4,575,330 to Hull
No. 1 discloses an apparatus for the production of three-dimensional objects by stereolithography. The liquid medium used in this three-dimensional modeling apparatus is usually a liquid photosensitive polymer that can be cured by irradiation with an ultraviolet beam. As described in U.S. Pat. No. 4,575,330, the liquid level of the liquid medium used in the preferred embodiment is such that the ultraviolet beam maintains a precise and accurate focus in a constant plane. Must be maintained at a certain level.

The total intensity of the ultraviolet beam on the liquid surface of the liquid photopolymer and the intensity distribution (beam profile) on the beam cross section depend on other factors (characteristics of the liquid photopolymer, the beam stays in a single spot). Time etc.)
In connection with this, the depth and contour of the photopolymer that is cured or polymerized by the irradiation of the beam is determined. The beam profile is dependent on the liquid level of the liquid photopolymer as the beam is focused so as to have a known contour at a given liquid level of the liquid photopolymer. If the liquid photopolymer has a liquid level that is different from the predetermined liquid level, the difference in beam profile is that the width of the cured photopolymer and its depth are different from the intended depth and width. Let

Further, if the liquid level of the liquid photosensitive polymer is higher than the predetermined liquid level, the depth of the cured photosensitive polymer is sufficient to reach and adhere to the preceding cured layer. And will result in adverse effects on the structural integrity of the object. On the contrary, if the liquid level of the liquid photosensitive polymer is low, the new layer becomes thinner than expected, which is inconvenient for the object reproduction accuracy.

The liquid level of the liquid photosensitive polymer must be maintained regardless of shrinkage or reduction caused by curing, heating, evaporation or the like of the liquid photosensitive polymer. In the early model of the three-dimensional modeling apparatus, this liquid level was maintained by providing a drainage channel. The liquid level of the liquid photopolymer rose slightly (due to surface tension) to just above the overflow drain. However, the drainage channel cannot control the liquid level of the liquid photopolymer with sufficient accuracy to allow high resolution of parts made by the stereolithography machine. Therefore, there is a need for more precise means of measuring liquid level.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is capable of measuring the liquid level of a liquid medium of a three-dimensional modeling apparatus with extremely high precision and high reliability. An object of the present invention is to provide an apparatus for measuring a level and a three-dimensional modeling apparatus having a liquid level measuring mechanism.

[0015]

That is, an apparatus for measuring a liquid surface level according to the present invention determines a liquid surface level of a liquid medium in a container of an apparatus for curing a liquid medium and three-dimensionally molding a three-dimensional object. An apparatus for measuring, the first tank of the above-mentioned container containing a liquid medium, the second tank of the above-mentioned container, which is provided outside the first tank and is connected to the first tank. A second tank having an upper opening and at least a liquid surface of the liquid medium in the second tank is separated from a liquid surface of the liquid medium in the first tank, and The liquid surface level of the liquid medium in the second tank is measured, and the liquid surface level of the liquid medium in the first tank is determined from the measured liquid surface level of the liquid medium in the second tank. An apparatus characterized in that it is provided with means.

In the above-mentioned apparatus for measuring the liquid level according to the present invention, the determining means is a beam source for generating a measuring beam that does not cure the liquid medium, and the measuring beam is the above-mentioned first beam. Beam directing means for entering the liquid surface of the liquid medium in the second tank, and a sensor for detecting the measurement beam reflected by the liquid surface of the liquid medium in the second tank A sensor that outputs a different signal depending on the position of the measurement beam may be provided.

In this case, the beam source for generating the measuring beam may be a laser.

The sensor may be a two-cell type photodetector. In this case, the device for measuring the liquid level may further include means for producing a signal from two separate signals generated by the two-cell photodetector.

Further, the above-mentioned first and second tanks are arranged so that the liquid level of the liquid medium in the first and second tanks becomes the same level, and the above-mentioned sensor. The signal output by may output a liquid level of the liquid medium in the first tank.

Further, the first tank is adjacent to the second tank and has a common wall having an opening submerged in a liquid medium, which connects the first and second tanks. It may be separated from the second tank.

Furthermore, the device for measuring the liquid level may further comprise means for adjusting the liquid level of the liquid medium, which is connected to the determining means. In this case, the adjusting means may comprise a plunger movable into and out of the liquid medium, and in addition, the device for measuring the liquid level may include the plunger in the liquid medium. A motor may be provided for moving in and out. Where the motor is
The plunger may be moved based on the liquid level in the second tank measured by the determining means.

Further, the sensor may be arranged at a position fixed with respect to the second tank.

Furthermore, the device for measuring the liquid level may further include a mirror for directing the measuring beam, which is arranged at a fixed position with respect to the second tank.

The liquid medium in the first tank and the liquid medium in the second tank may be the same liquid medium.

In the three-dimensional modeling apparatus according to the present invention, a layer of the liquid medium is formed and cured on the layer formed in front of the three-dimensional object which is being formed from the cured liquid medium. A three-dimensional modeling device for modeling the three-dimensional object substantially layer by layer, the first tank of a container containing a liquid medium, and the three-dimensional object in the first tank. The first tank in which the object is molded, the three-dimensional object in the process of molding,
Means for immersing the liquid medium in the first tank below the liquid level, a second tank of the above-mentioned container provided outside the first tank and connected to the first tank. A second tank having an upper opening and at least the liquid surface of the liquid medium in the second tank is separated from the liquid surface of the liquid medium in the first tank; Means for measuring the liquid level of the liquid medium in the second tank and determining the liquid level of the liquid medium in the first tank from the measured liquid level of the liquid medium in the second tank The device is characterized by being provided.

In a preferred embodiment, first a layer of polymerizable liquid medium is applied to the surface of the object support. Excess polymerizable liquid medium is scraped from the layer by bladed over the surface of the layer to obtain a smooth layer of the desired layer thickness. A curing medium, such as a curing beam, is applied to the upper or work surface of the smoothed layer in a preselected pattern so that the layer is sufficiently cured to form the desired three-dimensional object. Subsequent layers are similarly applied and allowed to cure.

In a preferred embodiment, the object support is
It has a surface on which the layers constituting the three-dimensional object are laminated, and is provided so as to be able to move up and down in the bath of the polymerizable liquid medium in the first tank. The object support is lowered into the bath so that its surface (which may be the latest hardening layer) is generally below the level of the bath of polymerizable liquid medium by a distance greater than the desired layer thickness. To be The support is then raised so that the highly viscous polymerizable liquid medium on the surface is above the liquid level of the bath. After that, the horizontally moving doctor blade horizontally moves to scrape the excess polymerizable liquid medium so that a liquid layer of the polymerizable liquid medium having a desired thickness is formed. The support is then lowered so that the level of the upper surface of the smoothed layer of polymerizable liquid medium is approximately the same as the level of the bath. A curing beam is then applied over the layer smoothed in a graphic pattern to cure the thin liquid layer,
As a result, subsequent layers of the polymerizable liquid medium can be laminated thereon. The object support with a partially cured solid layer is further lowered from the bath level to allow the polymerizable liquid medium to flow over the solid layer and the above cycle is repeated.

This process involves the formation of a number of successively formed layers while bonding the layers together.
This is continued until the desired three-dimensional object is formed. The three-dimensional molded final product must be strong enough for subsequent handling. Normally, the object is final cured after formation. In the above process, the level of the polymerizable liquid medium in the bath is maintained at a constant level, especially when the smoothed layer is lowered into the bath and cured by the curing beam. You have to be careful. This is because the liquid medium in the bath forms the boundary of the smooth layer of the liquid medium. In a preferred embodiment, the liquid level of the liquid medium in the bath is detected in a suitable manner, the liquid level is compared to a desired level, and in response to the difference, the piston or plunger in the bath is Raised and lowered in the bath to control the level to the desired set point.

The three-dimensional object is moved one level at a time by moving a curing beam such as an ultraviolet beam by a helium-cadmium laser on the liquid surface of the liquid medium and solidifying the liquid medium in the portion irradiated with it. Layer by layer.
Ultraviolet absorption of the liquid medium prevents the ultraviolet beam from penetrating deep into the liquid medium, forming a thin layer.

For the liquid level control, a device for generating a measuring beam that does not harden the liquid medium and an electric signal that differs according to the change in the position of the measuring beam that collides with the liquid surface of the liquid medium and is reflected. A new and improved device for measuring liquid level, including an output sensor, is used.
This sensor is installed at a fixed distance in the vertical direction with respect to the liquid surface. The measurement beam is emitted at a constant angle with respect to the liquid surface toward the liquid surface along the first optical path, and is reflected at the beam detectable position of the sensor along the second optical path from the liquid surface to the sensor. (The measurement beam need not be visible light, but the term "optical path" is used). The change in liquid level changes the position at which the measuring beam strikes the sensor, thereby causing a change in the electrical signal from the sensor.
This signal can then be used to control devices that manage liquid level, such as pumps, diaphragms, plungers and the like.

It is assumed that the liquid surface of the liquid medium is flat, that is, it maintains the same angle with respect to the measuring beam even when the liquid surface level of the liquid medium changes. Therefore, the angle at which the measuring beam is reflected from the liquid surface does not change. If the liquid surface is not flat, the measuring beam will not be reflected or will be reflected at an unpredictable angle. A weighted mirrored float may be placed on the liquid surface to reflect the measuring beam.

In a preferred embodiment, the device for producing the measuring beam is a laser and the sensor is a number of coupled photocells (photovoltaic cells) located offset from the liquid surface along a direction perpendicular to the liquid surface. including. The measuring beam by the laser should not change the state of the liquid. Electronic circuitry is used to compare the electrical output signals of each of the photocells and thereby detect movement of the position of the measuring beam as it strikes the sensor.
When the liquid level changes, the measuring beam does not strike the same position on the sensor. One photocell receives more beams than before and another photocell receives less. This changes the electrical output signal from each of the photocells. The comparison circuit detects this difference and either the instrument for displaying the liquid level or the device for changing the liquid level (plunger, etc.), or
Drive both.

[0033]

The apparatus for measuring the liquid surface level according to the present invention is an apparatus for measuring the liquid surface level of a liquid medium in a container of an apparatus for curing a liquid medium to three-dimensionally form a three-dimensional object. A first tank of the above-mentioned container containing a liquid medium, a second tank of the above-mentioned container provided outside the first tank and connected to the first tank, wherein A second tank which is open and in which at least the liquid surface of the liquid medium in the second tank is separated from the liquid surface of the liquid medium in the first tank; and in the second tank For measuring the liquid surface level of the liquid medium, and for determining the liquid surface level of the liquid medium in the first tank from the measured liquid surface level of the liquid medium in the second tank Therefore, the liquid level can be measured with extremely high precision and high reliability. The same applies to the three-dimensional modeling apparatus according to the present invention.

That is, the apparatus for measuring the liquid surface level according to the present invention is a rapid, highly reliable apparatus which reacts extremely sensitively. This device is able to measure the liquid level very precisely and to maintain it accordingly very accurately. Currently, the device for measuring liquid level made according to the present invention is at least ± 0.5.
The liquid level can be measured (maintained) within the range of mil (± 0.0005 inch = 0.0125 mm).
The same applies to the three-dimensional modeling apparatus according to the present invention. By measuring the liquid level in this way with extremely high precision and high reliability, the three-dimensional object formed by the three-dimensional modeling apparatus of the present invention has extremely improved dimensional accuracy, and the three-dimensional object is formed. It is possible to significantly reduce the formation cycle time of each layer to be processed, and it is possible to increase the untreated strength and the final cured strength.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

1 and 2 schematically show an example of a three-dimensional modeling apparatus for forming a three-dimensional object. As shown in these figures, a vessel 10 is provided for containing a bath 11 of a polymerizable liquid medium. Object support stand 1
2 is arranged in the tank 10 and is a motor (not shown)
Are adapted by frame elements 13 and 14 to move up and down in the bath. The support 12 has a horizontal surface 15 on which the three-dimensional object is formed according to the invention. A trough 16 is provided on the upper surface of one wall of the tank 10, and a plunger 17 or a piston is arranged in the trough to adjust the liquid level of the liquid surface 20 of the polymerizable liquid medium in the tank 10. Moved up and down by the control 18 to control.

The liquid surface level of the liquid surface 20 of the bath 11 is a radiation source 21 such as a He-Ne laser directed to the liquid surface 20 at an angle, and a beam sensor capable of a two-cell type detector ( (Detector) 22. Sensor 2
The position of 2 is adjusted so as to form a complementary angle with respect to the liquid surface 20 so as to receive the measurement beam from the He-Ne laser. A control system 23 is provided to control the movement of the plunger 17 by the motor 18.

Computer controlled curing beam source 2
4 is arranged above the bath 11, and the liquid surface 20 of the bath 11
A curing medium such as an ultraviolet beam or another type of curing beam is emitted in a predetermined pattern to cure the polymerizable liquid medium in the layer on the support table at the portion where the curing beam acts.
The movement and movement of the curing beam source 24 and the up and down movement of the object support 12 are an integral part of the computer control system 25, as will be described in more detail below.

A doctor blade 26 is equipped on the upper part of the tank 10 and is adapted to move horizontally on the upper part of the tank. The blade support 27 is slidably installed on rails 30 and 31 arranged along one side surface of the tank 10. The threaded drive shaft 32 passes through a threaded passage (not shown) in the blade support 27,
Rotation of the shaft by the motor 33 moves the blade support 27, which causes the blade 26 to move horizontally over the top of the tank.

The operation of the three-dimensional modeling system shown in FIGS. 1 and 2 is well illustrated in a series of drawings, FIGS. 3-6. First, in FIG. 3, the object support 12 is
The stereolithography procedure begins with the horizontal surface 15 being positioned within the bath 11 of the polymerizable liquid medium such that it lies a short distance from the liquid level 20 of the bath. This distance is greater than the desired thickness of the layer of polymerizable liquid medium to be cured.
The layer of polymerizable liquid medium just above the horizontal surface 15 forms the first solid layer of the three-dimensional object when cured.

The next stage in the process is shown in FIG.
The object support 12 is raised so that the layer 34 of the polymerizable liquid medium on the horizontal surface 15 is kept above the liquid level 20 of the bath 11. This polymerizable liquid medium is a relatively viscous liquid, so that when the layer is withdrawn from the bath,
It does not immediately drain from the edge of the horizontal surface 15 of the support 12.
The doctor blade 26 moves horizontally and its lower edge 3
5 scrapes excess polymerizable liquid medium from layer 34, smoothing upper working surface 36. The appropriate blade speed is empirically determined to impart the desired level to the work surface 36. Here, the "working surface" means a surface on which the work of hardening the polymerizable liquid medium on the support 12 by applying an ultraviolet beam or other suitable hardening beam is performed. In addition, one or more passes through the doctor blade 26 at a particular speed may be required to provide the desired level of smoothness 34. Typical blade speeds are approximately 1 to 1 per second
It will be between 0 inches (2.54 and 25.4 cm).
If a low viscosity polymerizable liquid medium is used, an enclosure may be used to hold the polymerizable liquid medium until it cures.

The working surface 36 of the layer 34 is the doctor blade 2
After being leveled by 6, the object support 12 is lowered into the bath 11 as shown in FIG.
6 has the same height as the liquid surface 20 of the bath 11, that is, the same plane. The polymerizable liquid medium of the bath 11 surrounding the layer 34 forms an interface 37 which essentially becomes a wall supporting the outer periphery of the layer 34. Disturbances in either the working surface 36 or the liquid surface 20 of the bath 11 caused by the immersion of the object support 12 and the layer 34 in the bath 11 are relatively slight and subside quickly.

Computer controlled curing beam source 2
4 is actuated with a short delay to eliminate any turbulence of the liquid surface and places an ultraviolet beam or other suitable curing beam on the working surface 36 of layer 34 in a predetermined pattern, where the curing beam acts. To cure the polymerizable liquid medium. Layer 34 is sufficiently cured to provide the green strength needed to support additional layers that are subsequently made as well, and to facilitate handling of the molded object after it has been three-dimensionally shaped and before final curing. obtain.

After irradiation of the layer 34, the object support 12 is further lowered, as shown in FIG. 6, allowing the polymerizable liquid medium from the bath 11 to flow over the preceding hardened layer 34, and the new layer 3
8 is formed and a new cycle of the process is started.

As described above, a series of polymerized and cured layers are laminated as shown in FIG. 1, with each layer effectively being a thin cross section of the desired three-dimensional object 40. The thickness of the individual layers can be varied based on the composition and viscosity of the polymerizable liquid medium and the nature and strength of the curing medium. However, the typical thickness is about 0.005 to 0.
The range is up to 01 inches (0.125 to 0.254 mm). The final three-dimensional object 40 formed by the stereolithography system described above is removed from the bath 10 and further processed to complete the cure of the uncured material remaining within the bounding surface of the three-dimensional object. If necessary, a surface finish such as sander finish may be applied.

A wide variety of polymerizable liquid media can be used in the present invention, as well as a wide variety of curing media. But for now,
A photopolymerizable liquid medium such as acrylic resin is preferred with an ultraviolet beam for its curing. Preferably, the viscosity of the polymerizable liquid medium should exceed 100 centipoise, with the range of about 1000-6000 centipoise being preferred.

The computer controlled stereolithography apparatus shown schematically in FIGS. 1 and 2 was used to form the three-dimensional object shown in FIG. 0.25 x 8.25 inches (20.9 cm x 2
0.9 cm), maximum height is about 4 inches (about 10 cm),
The minimum height was about 1 inch (about 2.54 cm). The wall thickness was about 0.25 inch. As the polymerizable liquid medium, a relatively viscous resin called 4112-65 resin manufactured by Desoto Chemical Company was used. The temperature of the liquid medium was maintained at about 30 ° C. The thickness of each layer to be made was about 0.02 inch (about 0.5 mm).

Each layer was manufactured by the following steps. The object support base of the three-dimensional modeling apparatus is used as a polymerizable liquid medium.
It is submerged in a bath of 12-65 resin and poured onto the surface of the support to form an initial layer of polymerizable liquid medium that is thicker than desired. Raise the support so that its first layer is above the bath level. A blade moving at about 1 inch per second (about 2.54 cm) scrapes about 0.1 inch (about 2.54 mm) of polymerizable liquid medium in one pass, and about 0.02 inch ( Leave about 0.5 mm) of polymerizable liquid medium. The support is then lowered so that the smooth working surface of the layer is level with the liquid level of the bath. The layer is a He-C that emits a beam at a wavelength of about 325 nanometers with a power output of about 15 milliwatts.
Receives an ultraviolet beam from a d laser. The total time for each layer cycle was about 35 seconds. The time to make such parts by conventional methods is about 1 per layer cycle.
It was 65 seconds. The total time saved by utilizing the apparatus of Figures 1 and 2 was about 7.5 hours.

Next, FIG. 8 showing one embodiment of the present invention will be described. In this embodiment, a preferable mechanism for measuring the liquid level of the liquid medium 20 (UV curable photosensitive polymer such as Desoto # 65) in the first tank (main tank) 30a is attached to the three-dimensional modeling apparatus. Has been shown. 8th
Parts of the three-dimensional modeling apparatus shown in the figure other than the auxiliary mechanism for measuring the liquid level described above are described in US Pat. No. 4,575,330.
Has the basic form found in commercial stereolithography equipment sold by 3D Systems, Inc. under the acronym SLA-1. .

The solid modeling apparatus includes a wall 60 of the first tank 30a.
A second tank (sub tank) 40a communicating with the first tank 30a is added by the opening 50 in the. The dimensions of the second tank are 7 x 4 inches (1 inch) in the preferred embodiment of the invention.
7.78 cm × 10.1 cm). Liquid medium 20
Fills the first tank 30a and the second tank 40a. The liquid medium 20 is free to flow from the second tank to the first tank and, conversely, from the first tank to the second tank. The liquid level of the first tank (and hence the second tank) is precisely at a predetermined level for performing the three-dimensional manufacturing of parts (objects manufactured by three-dimensional modeling are referred to as “parts”). Must be managed. The device of the present invention achieves this end by the form of the preferred embodiment shown.

The first tank 30 below the side surface of the second tank 40a
A helium-neon laser 100 is mounted on the outer surface of a. The laser is adjusted so that its output measuring beam is emitted right above the side surface of the second tank. In the preferred embodiment of the invention, the Uniphase 1508 laser was successful. Uniphase 1
The 508 laser was chosen because of its low cost, small size, and low power requirements. The measuring beam emitted by this laser does not cure the liquid medium.

The measuring beam 110 output from the helium-neon laser was a mirror 120 (Lorin Optics # 60.2, mounted on an overhang above the second chamber.
It is emitted upward toward 1). As can be seen in FIG. 9, this mirror is provided with the liquid surface 7 of the liquid medium in the second tank 40a.
Refract the measuring beam along a first optical path to 0.
The measuring beam strikes the liquid surface 70 of the liquid medium at an angle β (incident angle is 90 ° -β). The angle β has a value such that the measuring beam is reflected along the second optical path 114. The variable range of angles meets the requirements of the second optical path, based on the characteristics of the liquid medium and the laser and the dimensions of the second vessel. In the preferred embodiment described here, this angle is 15 °.

The apparatus described herein measures the liquid level of the liquid medium in the second tank, but not in the first tank. This is advantageous because bubbles or other turbulence of the liquid surface may occur in the first tank when the component or the support passes through the liquid surface of the liquid medium in each cycle of manufacturing the component. When the measurement beam hits such a bubble or other turbulence of the liquid surface, the measurement beam may be reflected from the liquid surface of the liquid medium at an incorrect angle. Other liquid surface turbulences may occur at the top of the submerged part, which may cause erroneous measurement beam refraction, and it will take time to smooth these turbulences. These include areas where the liquid medium has been extruded by the blade during recoating due to swelling of the liquid medium or pulling of the blade. These problems are especially acute for certain component geometries that have closed volumes or have large flat horizontal surfaces, which are discussed in more detail below. By measuring the liquid level of the liquid medium in the second bath, the above problems are minimized or completely solved.

After reflection from the liquid surface 70 of the liquid medium to be used, the measurement beam has a second optical path 1 at the same angle as the angle with respect to the liquid surface when the measurement beam hits the liquid surface 70.
Return along 14. Then, the measurement beam is reflected by the mirror 120.
This corresponds to the two-cell type photodetector 130 attached to the plunger housing 85 on the side surface of the second tank 40a on the opposite side. The mirror is adjusted so that the measuring beam impinges on the two-cell photodetector 130 when the liquid level 70 is at the desired liquid level. The mirror does not move or rotate after being adjusted to reflect the measurement beam from the liquid surface 70 of the liquid medium to the two-cell photodetector when the liquid surface 70 is at the desired liquid surface level. .

A good two-cell type photodetector as shown in FIG. 11 is known as product number SD113-24-21-021 manufactured by Silicon Detector Corporation. 2 of other products and sizes
Cellular photodetectors would also be satisfactory. Hamamatsu 2D PSD (S1544) and 2D lateral cell (S1B5
Linear PSDs (position detectors) such as 2) could also be accommodated and may be preferable for devices intended to measure and display a large amount of output in length units. Two
The cell type photodetector consists of two parallel photocells 140.
The two-cell photodetector is mounted in the plunger housing 85 such that the parallel photocells 140 are one above the other and both photocells are above the liquid level 70. The two-cell photodetector can be tilted to intersect the second optical path 114 at a right angle, which is best seen in FIGS. 9 and 12. By doing so, the contour of the beam spot of the measurement beam on the two-cell photodetector is made to be a circle instead of an ellipse when the cross section of the measurement beam is originally a circular contour. it can.

When the liquid level rises or falls due to contraction due to curling or heating, the measuring beam strikes different positions on the liquid level 70. Therefore, the measurement beam impinges on a different location of the two-cell photodetector. This effect of the measuring beam is shown in phantom in FIG. 9, where the measuring beam is reflected along the second optical path 150 when the liquid level of the liquid medium is at a low level 80. It hits the low position of the 2-cell photodetector.

Although the change in liquid level is exaggerated to illustrate this effect, the preferred embodiment of the present invention measures the liquid level to maintain it at a predetermined level. It is a thing. Changes in liquid level are negligible as such changes in liquid level are quickly corrected as described below. For a given change in liquid level, the position at which the measuring beam hits the two-cell photodetector, irrespective of the value β, if the two-cell photodetector is mounted vertically without tilting Is also displaced. FIG. 10 shows low level 82 to high level 84.
The result of the change of the liquid surface level is shown in FIG. The difference between the liquid level 82 and 84 is the vertical distance d. It is shown that two different measuring beams arrive along the first optical paths 151 and 152 and strike the liquid surface of the liquid medium at angles β1 and β2, respectively. The second optical paths 153 and 154 (for the lower level 82) are
It is set so as to intersect the same point Y1 of the perpendicular line P.
When the liquid level rises to the higher level 84, the measuring beam follows the second optical paths 155 and 156, respectively. A simple trigonometric calculation is performed on both second optical paths 1
55 and 156 intersect the same point Y2 of the perpendicular P, and Y
The vertical distance between 1 and Y2 indicates a vertical change in liquid level, which is twice the value d. Therefore, if the two-cell photodetector is mounted vertically without tilting, the change in β does not affect the accuracy of the device for measuring the liquid level according to the present invention. The value of β chosen depends mainly on the angle at which a good reflection of the measuring beam is obtained within the constraints of the device.

The change in liquid level causes a change in the electrical signal emitted by the two-cell photodetector. The photocell 140 of the 2-cell photodetector has a thickness of 1 mil (0.02
They are separated by a narrow slit 160 of less than 5 mm (see Fig. 11). When the two-cell photodetector is not illuminated by the measurement beam, or when the measurement beam is exactly centered on the slit 160 between the photocells 140, the output signals of both photocells are equal. If the beam moves so that it hits one photocell instead of the other, the output signals will be unequal. The comparison of the unequal output signals by the comparator circuit results in a signal being sent to the stepper motor 90 to drive the plunger 95, as described below. The plunger 95 (see FIG. 9) moves up and down as needed to maintain the liquid level.

The plunger maintains the liquid surface level spatially at a substantially constant level. This is advantageous for keeping the curing beam emitted by the laser in focus. If the liquid level is variable, as is the case with some liquid medium supply systems that supply a new liquid medium to the first bath at each cycle of component fabrication, the laser emitting the curing beam will generate a new liquid medium. The face level would have to be refocused.

FIG. 12 will be described. Figure 12 shows
6 illustrates a feedback loop provided between the photocell 140 and the step motor 90. With this feedback loop, the step motor 90
The plunger 95 is moved up and down based on the current output signals from the two photocells 140. Photo cell 1
The current output signals 205 and 207 of 40 are provided to a current / voltage converter 200 which converts the output of each photocell to a voltage between 0 and 2.5 volts. Current / voltage converter 2
00 of the two voltage output signals 215 and 217 (each photocell 140 has its own output signal).
Where the voltage output signals are subtracted from each other. The voltage output signal 215 is generated by adding the reference voltage (not shown).
And 217 is the difference between the signal 22 between 0 and +5 volts.
It is 5. If the liquid level is at the desired level, signal 2
25 will be +2.5 volts. The signal 225 is sent to the analog-to-digital converter 230, where it is converted to a digital signal 235 and sent to the computer 240. Computer 240 compares signal 235 with a predetermined digital signal of the desired fluid level and activates stepper motor controller 245. The step motor controller 245 then steps motor 90 which moves the plunger 95 up and down to displace the liquid level in order to return it to the desired value (in the preferred embodiment, Mineral Electric Company). LAS3802-
001 step motor).

The computer is programmed to measure the liquid level immediately after the first dipping operation, in which the part is submerged by moving the support deep into the liquid medium before The platform is raised,
Draw the next layer on the part. The liquid level is measured and controlled only at this particular time in the fabrication process. The computer compares the signal 235 to the reference voltage only at this particular time and generates a signal 242 to the stepper motor controller 245 that determines the time and direction in which the stepper motor controller 245 operates the stepper motor 90.

Next, an auxiliary example of the recoating apparatus which can be added to the three-dimensional modeling apparatus of the present invention and used will be described. In this example, the ability to change several parameters related to the blade recoating process is provided, these parameters include the doctor blade and the bath in which the three-dimensional object is formed (the first one in the above embodiment). There is a blade gap, which is the distance between the liquid surface of the liquid medium in the tank) and a blade clearance, which is the distance between the blade and the upper part of the component. Usually the blade clearance is the same as the layer thickness of the next layer formed, but it may not be.

The optimum size of the blade gap depends on the weight of some considerations. A large blade gap is problematic because it takes time to smooth and can wrinkle the liquid surface of the bath of liquid medium.
The reason this is such a problem is the extent to which the blade gap must be raised above the level of the liquid medium to scrape the top of the part, and then the part before the next layer begins to cure. This is because it determines how much the upper part of the must be lowered. For example, if the blade gap is 125 mils (3.125 mm) and the desired blade clearance is 20 mils (0.51 mm), then the part is scratched after it is fully immersed in the liquid medium. It is pulled above the liquid surface of the liquid medium for removal. Specifically, because the blade clearance is 20 mils (0.51 mm), the top of the part must be raised 105 mils (2.67 mm) above the liquid surface of the liquid medium before the scraping can begin. . After that, up to the surface of the bath of liquid medium, which is the working surface before curing begins, ie 125 mils (3.1
75 mm) so that the top of the part is 20 mils (0.51 mm) below the surface of the liquid medium. The greater the movement of the upper part of the component, the greater the turbulence that can occur on the liquid surface due to the movement of the support and the support and other parts of the component into and out of the liquid medium. This turbulence was described as "wrinkle" in the above. These wrinkles usually occur at the interface of the liquid medium and the component.

A small blade gap is also a problem. The smaller the blade gap, the more
This is because the doctor blade pushes out a large amount of liquid medium with a predetermined scraping. For example, if the blade gap is 0 mils and the doctor blade is kept exactly at the bath level, the wrinkle problem described above may be reduced, but the doctor blade will form a three-dimensional object. It may be necessary to scrape the liquid medium from the entire liquid surface of the bath. This creates a slight wave of the liquid medium, which can flood the sides of the tank in which the three-dimensional object is formed, causing bubbles to burst on the liquid surface of the liquid medium.

It has been found that a blade gap of 25 mils (0.64 mm) is a good compromise between both problems mentioned above. Normally, the blade gap is set once before the parts are manufactured, and then kept constant throughout the parts manufacturing.

Another parameter for which modification is advantageous is blade clearance. However, unlike the blade gap, it is desirable that the blade clearance can be changed not only once before the component is manufactured but also during the component manufacturing.

Variable blade clearance is advantageous because it allows for step recoating. Staged recoating is where multiple scrapings of blades are used for recoating a given layer, with different blade clearances at each scraping and possibly different blade speeds. For example, if the layer thickness of the next layer is 20 mils (0.51 mm), in the step recoating process the blade clearance is 60 mils (1.52 mm) on the first scraping and the second 40 mils (1.02 mm) for scraping, 20 mils (0.51) for third scraping
mm). As a result, each scrape scrapes a smaller amount of liquid medium than if a single scraper was used for recoating and the blade compared to when a single scrape was used for recoating. Blisters of liquid medium rarely occur on the front surface. Large blistering on the front of the blade is a problem when a closed volume of liquid medium hits the blade. In the presence of a closed volume, gravity can cause a large, blistering liquid medium to flow under the blade, disturbing the desired layer thickness of the smooth layer formed at the trail of the blade. This problem would not be so serious if it did not cause blistering at the first time. This problem can be illustrated by FIG. 13, showing the blade 300 in the process of being scraped. Part 304
Is lowered below the blade by a distance 303 which is a blade clearance. Smooth liquid layer 301
Are formed in the imprint of the blade, but excess liquid medium swelling, indicated by reference numeral 302, occurs on the front surface of the blade. If the blisters 302 are large enough when the blade hits the closed volume of liquid medium indicated by reference numeral 305, the blistering liquid medium will flow underneath the blades as indicated and the smooth layer 301 May disturb formation. This effect is not so great when the blade is moving on a flat horizontal surface of the part, since there is little room for the liquid medium to flow under the blade.

Another parameter that can be changed is the blade speed, and more particularly the blade speed in step scraping, where a different speed can be specified for each scraping. It is advantageous to be able to set the blade speed according to the part geometry. If the blade is moving in a large flat horizontal area of the part, if the blade moves too fast, excess liquid medium can be scraped off by the tension, which moves the liquid medium under the blade at discrete speeds. It will be. For example, when the blade is moving at 5 inches per second (about 13 cm), 1 mil below the blade (about 0.
(025 mm) liquid medium is 4 inches per second (about 10 cm)
And the liquid medium below it is 3 inches per second (about 7.6
cm). In some cases, even in flat areas, the tension can be quite severe and all the liquid medium may be scraped off by the blade. Therefore, in large flat areas, it may be desirable to reduce the blade speed so that the above problems do not occur.

On the other hand, above the closed volume, if the blade moves too slowly, this will cause the blistering liquid medium to take a lot of time to flow under the blade. Therefore, above the closed volume, it is desirable to increase the velocity of movement of the blade so that there is not enough time for the liquid medium to flow. However, the speed cannot be increased too much, because if the speed is increased too much, waves of the liquid medium may form on the front surface of the blade and cause bubbles or bursts.

Unfortunately, it is difficult to dynamically change the blade speed based on the shape of the part during part manufacture. However, if a variable speed is applied for each scrap of the step recoating, the blade speed and number of scrapes for each scrap can be selected to minimize the above-mentioned problems for conventional parts. For example, for certain parts with a large flat area and closed volume combined, use multiple scrapes per layer, in the range of 5-10, with relatively slow blade speeds at each scraping. May be desirable. Due to the multiple scrapings, only a small amount of liquid medium is extruded with each scraping, resulting in blisters that cannot flow under the blades when hitting the closed volume. On the other hand, due to the slow blade speed,
The problem of over-extruding the liquid medium from the surface of large flat horizontal parts is minimized. This is because the blade cannot produce enough tension to scrape all the liquid medium. Moreover, slow blade speeds are not a problem on closed volumes, as large blisters cannot be formed, and slow blade speeds cause little or no liquid medium flow below the blades.

It is also advantageous to be able to vary the extent to which the part is over-immersed in the liquid medium before the start of scraping. As mentioned above, the component is usually dipped below the liquid surface of the liquid medium by a thickness greater than the desired layer thickness of the next layer. For example, in the commercial embodiment of the SLA known as SLA-250 manufactured by 3D Systems, Inc., the assignee of the present invention, the preferred layer thickness is ½ mm or less. SLA
At -250, the part is usually over-immersed in a liquid medium by 8 mm, the thickness of which is several times the nominal layer thickness. Therefore, it is desirable to be able to change this parameter according to the layer thickness.

A typical recoating cycle involves the following steps. 1) Deep over-immersion of parts, 2) Measurement and adjustment of liquid level of liquid medium, 3) Lifting of immersion, 4)
Scraping, 5) Delay until the liquid level stabilizes. Over-immersion of a thickness greater than the layer thickness not only ensures that the liquid medium swells on top of the parts that can be smoothed during scraping, but can also hinder the measurement of the liquid medium level in step 2) Guarantees that the turbulence of the liquid surface is smoothed at high speed. If the part were submerged near the surface, it would take more time due to any leveling of the surface disturbances that could form on the part. This is because the "passage" between the top of the part and the liquid medium is small, limiting the movement of the liquid medium necessary to smooth the turbulence.
Therefore, over-immersion greater than the layer thickness makes the measurement of the liquid level even more accurate. Furthermore, if over-immersion is limited to a single layer thickness, 1/2 mm (about 20 mm
Thin layer thicknesses below (mils) would be less desirable. However, such layer thicknesses may be necessary to fabricate certain components with high resolution. Therefore,
Deep over-dip also facilitates the use of thin layers in this range.

That is, in the above example, the ability to change the blade gap, blade clearance, over-immersion depth and blade speed, and the ability to use step recoating is a bespoke blade tailored to a particular part geometry. Means may be provided to improve recoating, thereby overcoming certain problems associated with these geometries.

In the ancillary example, the blade design can be modified to be more efficient. SLA-
At 250, the doctor blade cross section is rectangular with a width of 1/8 inch (3.175 mm). further,
The blade is supported only at one end with a support rail that guides the blade and its movement in a manner similar to a cantilever. This can lead to problems known as flutter and twist, which can result in wobbling and twisting of the unsupported end of the blade, leading to failure of the recoating process such as uneven layer thickness. The degree to which the unsupported end twists or wobbles is proportional to the square of the blade length. An additional problem that can occur is the setting of the blade gap due to this problem. This process involves a number of steps, each of which can result in failures, and is time consuming. In addition, the process requires rotating the screw that will impart the torque, thus deforming the blade.

In a new commercial embodiment of the stereolithography system known as SLA-500, also developed by 3D Systems, the blades are redesigned from the blades used in SLA-250.

First, in order to make it easier to obtain the setting of the blade gap, a micrometer screw is provided at each end of the blade, this screw of the blade on the liquid surface of the liquid medium. Allow the height of each end to be independently adjusted to a known value with a tolerance of 1/2 mil (0.0125 mm) without torque on the blade.

In addition, there are threaded and extendable needles, one at each end of the blade, each needle extending a known distance from the bottom of the blade,
That distance is equal to the expected blade gap. Currently, the needle is 25 mils (0.64 m) from the bottom of the blade.
m) It is supposed to come out. If different blade gaps are desired, needles that extend different amounts can be used.

Such a needle is illustrated in FIGS. 14 and 15. FIG. 14 shows needles 401 and 4 at both ends.
2 shows a blade 400 equipped with 02. First
FIG. 5 is an enlarged view of one of the needles attached to the blade. As shown, the needle is attached to the bottom surface 408 of the blade.
It has an extension 403 that extends a distance 404 away from. For SLA-500, this distance is 25 ± 0.5 cm
(0.635 ± 0.0125 mm). As shown, the needle is preferably a threaded portion 40 that is a 60 revolutions / inch (23.6 revolutions / cm) micrometer screw.
Have five.

The blade needle mount is identified by reference numeral 409. As shown, the mount has a threaded portion 406 and a stop 407 into which the threaded portion of the needle can be screwed in to control the extent to which the needle exits the bottom surface of the blade.

To set the blade gap, attach the needle by screwing it into the blade until the needle is out the proper amount, and the micrometer screw at one end of the blade touches the liquid surface of the liquid medium with the needle at that end. Rotate up to. This is because the tip of the needle is 1/4 to 1/2 cm (0.0064
(mm to 0.0127 mm), a large meniscus that can be easily observed with the liquid surface of the liquid medium is formed when it comes into contact with the liquid medium, so that it can be easily visually determined. Therefore, the needle is 1 /
4 to 1/2 cm (0.0064 mm to 0.0127 m
It can be positioned at the liquid level with a tolerance of m).
Then adjust the micrometer screw at the other end of the blade until the needle at that end touches the liquid surface of the liquid medium. Then the blade is pulled up and then pulled down to see if both needles touch the surface at the same time. If they do not touch at the same time, repeat the above cycle until they touch. If both needles touch the surface of the liquid at the same time, the blade gap is considered set and the needles do not screw in and do not extend any further. However, the needle is held in the mount so that the blades have the same weight.

Other means for attaching the needle to the blade are possible, including the use of detent pins and release buttons similar to those used in ratchet mechanisms.

To reduce twisting and wobbling of the blades, a second rail can be added so that each end of the rail is supported by that rail. This will reduce or eliminate twisting and wobbling of the unsupported end of the blade.

With such dual rail support, the blade can be made thicker to increase strength and reduce wobbling in the center of the blade. Thick blades may deflect more and may not be supported by just one support. Currently, the SLA-500 blade has a width of 1
/ 8 inch (3.175 mm), 3/16 inch (4.
76 mm) and 1/4 inch (6.35 mm).

Furthermore, as shown in FIG. 16, the cross section of the blade can be modified and need not be rectangular. First, the bottom surface of the blade is known as the angle of attack and the clearance angle, respectively, such that the non-horizontal edges of the blade near the bottom surface are indicated by reference numerals 506 and 507, respectively.
The corners can be configured to form the liquid surface of the liquid medium. The angle of attack is the angle in the direction of movement of the blade and the angle of departure is the angle of the other edge. These corners are added to further improve the flow of liquid medium below the blades. Without these corners, turbulence can occur under the blade and bubbles can form. Air bubbles are a problem because they can move under the blade with the blade and remain after the blade scrapes the surface of the component. as a result,
Air bubbles will cause component failure. By angling the edges of the blades, the pressure gradient under the blades can be reduced, resulting in less liquid medium splitting and thus less turbulence and bubble formation. It has been found that, depending on the part geometry, these angles can range between 5 and 8 ° and that the angle of attack can be different from the clearance angle. For the SLA-500, a 6 ° angle of attack is used.

The blade of FIG. 16 is shown as symmetrical so that it can be scraped in either direction. Alternatively, an asymmetric blade could be used to selectively scrape in either direction depending on the angle of attack of the direction of travel. Other blade configurations are possible.

FIG. 17 shows the blade of FIG. 16 with each apex angle being a curve. This will further reduce the disturbance of the liquid surface of the liquid medium. FIG. 18 is an example in which the entire bottom surface is a curved surface. FIG. 19 shows an example in which the bottom surface has a sharp apex angle.

Next, the recoating software used in SLA-250 will be described. FIG. 20 shows the software specifications according to the flowchart. Before utilizing this software, the user must first specify certain parameters used to control the movement of the support. These parameters are ZA,
ZV, ZW and ZD. US Patent Application No. 33
As detailed in No. 1,644, the support base is PROCE
It is under the control of a computer known as the SS computer. ZA is the amount by which the PROCESS computer accelerates or decelerates the support. ZV is the maximum speed the support can achieve. ZD is the depth for overimmersing the support in the liquid medium before scraping.
As mentioned above, the ZD is usually greater than the layer thickness. Z
W is a delay for stabilization, and after the support is lowered after scraping, the upper surface of the layer of the liquid medium is brought to the same level as the liquid level of the liquid medium in the tank in which the three-dimensional object is formed. The amount of time the PROCESS computer is instructed to wait to grant. The PROCESS computer
Wait the amount of time specified by ZW before curing the liquid medium on top of the part.

In addition to these parameters, the user
SN indicating the number of scrapings for each layer, meaning global speed, and GV indicating that all scrapings are performed at a specified speed
Other variables may be specified for each layer or range of layers, such as. The user can also use the individual speeds V1 to V7 for each scraping 1 to 7 respectively.
Can also be specified. By setting these values, the user can instruct to change the speed after each scraping.

The process begins at step 700, where layer N is depicted. Next, in step 701, the support is lowered below the surface of the liquid medium by a depth of ZD at a rate determined by ZA and ZV. Step 703
In, a post-immersion delay is performed to stabilize the liquid medium after the support is moved.

In step 704, the signal from the two-cell photodetector is obtained and the bias (BCV) introduced from the detection circuit is obtained.
(Identified as AL-BIAS)). The value of the signal is the upper limit and L designated as UPLIM.
OWLIM is compared with the lower limit value indicated. If the value of the signal is between these two values, the liquid level of the liquid medium is estimated to be at the correct level.

Assuming the liquid level is at the correct level, step 705 checks to see if a flag has been set. The flag is set in response to a key pressed by the user and indicates that the user manually adds or removes the liquid medium from the bath. If the flag is not set, then in step 708 a determination is made that the scraping number SN of layer N + 1 is greater than 0 and that the support is in a safe position so that the blade does not bump during scraping. The inspection is done. The upper limit of the position of the support is designated by the simple memory name NOSWEEP.

If these conditions are met, then in step 709 the internal counter SWEEP is first initialized to 0 and then incremented. At step 712, the blade is inspected to determine whether it is at the front or the back of the bath in which the three-dimensional object is formed. At that time, if it is in the front part of the tank in which the three-dimensional object is formed, in step 713,
The blade moves at a speed based on the current value of SWEEP (S
Scraping towards the rear of the bath in which the three-dimensional object is formed (for the distance specified by WEEPDIST).

When the blade reaches the rear of the tank in which the three-dimensional object is formed, it is customary to use the short memory name LIMIT SWIT.
Activate the switch identified by CH. If the limit switch is activated, then in step 727 a check is made to determine if all the scraping specified by SN has been performed for that layer. If the scraping has not been performed, the process jumps back to step 709 and the above-described cycle is repeated.

Returning to step 714, if the limit switch does not actuate, the blade moves slowly toward the rear at a rate of 0.5 inch (1.27 cm) per second, so long as the limit switch actuates within 2 seconds. , Jump to step 722. If still not working, the process ends at step 721.

Returning to step 712, if the blade is at the rear of the bath in which the three-dimensional object is formed, step 717.
, The blade scrapes towards the front of the vessel where the three-dimensional object is formed at a speed that should be a function of the current scraping number, and then in step 718, determines whether the limit switch has been activated. Inspections are performed to confirm. If the switch is activated, the process jumps to step 722. If not, the blade moves slowly toward the front at a rate of 0.5 inches (1.27 cm) per second, and if the limit switch is activated within 2 seconds, step 722.
Jump to. If still not working, the process ends at step 721.

Returning to step 704, which is a stage immediately after the support table (and the parts) is submerged below the liquid surface of the liquid medium, if the liquid surface level of the liquid medium is not at the correct level,
In step 723, a test is performed to see if the liquid level is too high or too low. BCVA
If L-BIAS is greater than UPLIM, then the liquid level is too low and the plunger must be lowered. At step 724, a check is made to see if the plunger is at the bottom of the tub where it is already installed, and if the plunger is not at the bottom of the tub, the plunger is lowered at steps 725 and 726, The plunger position identified by the short memory name PLUNGPOS is updated. At step 727, a delay is started to stabilize the liquid level and jumps again to step 704 to check the liquid level. After that, the above cycle is repeated.

Returning to step 724, if the plunger is at the bottom of the bath, the only way to raise the liquid level is to add a liquid medium into the bath. Step 73
At 2, the liquid level is checked again, and if the liquid level is still too low, in steps 733 and 734, the user is asked to press a key indicating to manually add the liquid medium. The process enters a loop until this key is pressed. When the key is pressed, the flag (the same flag that is checked in step 703) is set. While the user is naturally adding liquid medium to the bath, at step 739 the process enters a loop until the liquid medium level is at the current desired liquid level. When the liquid medium level reaches the current desired liquid level, a message is displayed to the user in step 740 indicating that sufficient liquid medium has been added, and jumps to step 704.

Returning to step 705, the flag must be reset after the liquid medium is added and the liquid surface level of the liquid medium is at the correct level. This condition is detected in steps 705 and 706, step 7
At 07, the flag is reset.

Returning to step 723, BCVAL-B
If IAS is less than LOWLIM, it indicates that the liquid level is too high and the plunger must be raised. At step 728, a check is made to see if the plunger is already in its highest possible position (indicated by 0). If the plunger is not in the highest position, then in steps 729 and 730 the plunger is raised and the plunger position identified by the short memory name PLUNGPOS is updated. Then step 72
At 7, a delay is started to stabilize the liquid level and jump to step 704.

Returning to step 728, if the plunger is already in its highest possible position and cannot be raised any further, the user should be informed to remove some of the liquid medium in the bath. At step 741 a check is made to determine if the liquid level is still too high, and at steps 742 and 743 the user is sent a message asking to remove the liquid medium and the key to acknowledge the message. You are prompted to press. The process goes into a loop until a key is pressed. If the key is pressed, the flag is set in step 744 and then step 7
At 45, while the user is removing the liquid medium, the level of the liquid medium is inspected to an appropriate level. The process enters a loop until the liquid surface level is at the proper level. When the liquid level of the liquid medium reaches the correct level, the user is informed in step 746 to stop the removal of the liquid medium, and jumps to step 704. In steps 705 to 707, as described above,
The flag is reset.

The liquid level measurement need not be performed on each layer, but because of either 1) thermal expansion, 2) contraction, and 3) displacement caused by support of the support, It should be noted that this is necessary if the may have changed. If neither of these is present, then liquid level measurements need not be made for each layer.

Returning to step 749, when all the scraping of layer N + 1 has been performed, the stabilization delay, which is ZW, is started, and in steps 750 and 751, layer N
Vectors of +1 are calculated and layers are drawn with these vectors in step 751. For more information on vector computation and layer delineation, see US patent application Ser.
No. 644.

The above cycle is then repeated for all remaining layers of the part.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a three-dimensional modeling device.

2 is a perspective view of the apparatus of FIG.

3 is a schematic cross-sectional view of the tank shown in FIG. 1 at each stage of the three-dimensional modeling procedure.

FIG. 4 is a schematic sectional view of the tank shown in FIG. 1 at each stage of the three-dimensional modeling procedure.

5 is a schematic cross-sectional view of the tank shown in FIG. 1 at each stage of the three-dimensional modeling procedure.

6 is a schematic cross-sectional view of the tank shown in FIG. 1 at each stage of the three-dimensional modeling procedure.

7 is a perspective view of a three-dimensional object manufactured by the apparatus shown in FIG.

FIG. 8 is a perspective view of a part of a three-dimensional modeling apparatus including a preferred embodiment of the liquid level measuring apparatus of the present invention.

FIG. 9 is a side elevational view of the preferred embodiment of the present invention.

FIG. 10 is a side elevational view of the optical path taken by the measuring beam of the preferred embodiment of the present invention under conditions of varying liquid level and angle of incidence.

FIG. 11 is a front elevation view of a two-cell photodetector used in the preferred embodiment of the present invention.

FIG. 12 is a block diagram of electronic components related to a two-cell photodetector according to a preferred embodiment of the present invention.

FIG. 13 is an explanatory diagram of a closed volume problem.

FIG. 14 is an explanatory view of a retractable needle with a thread for setting a blade gap.

FIG. 15 is an enlarged view of the needle attached to the blade.

FIG. 16 is a sectional view of a blade having an attack angle in the blade moving direction.

FIG. 17 is an explanatory view of another sectional shape of the blade of FIG.

FIG. 18 is an explanatory view of a sectional shape of a further different example of the blade of FIG.

FIG. 19 is an explanatory view of a sectional shape of still another example of the blade of FIG.

FIG. 20: Part of Flowchart of Recoating Software Used in SLA-250

FIG. 21 Partial continuation of a flowchart of the recoating software used on the SLA-250.

FIG. 22 Partial continuation of the flowchart of the recoating software used on the SLA-250.

FIG. 23 Partial continuation of the flowchart of the recoating software used on the SLA-250.

FIG. 24 Partial continuation of the flowchart of the recoating software used on the SLA-250.

[Explanation of symbols]

30a First layer 40a second layer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Charles, W. Hull United States California, Santa, Clarita, North, Tamarak, Lane, 28155 (72) Inventor Borzo. Modleque, Montobello, Nehru, California, Armstrong, Number, 306, 1640 (72) Inventor Andr J, Earl. Serkchewski, Glen, 26257 (72) Inventor Paul, F. Newhall, California, USA. Jacob, California, LA, Crecenta, Pine Ridge, Drive, 5347 (72) Inventor Charles, W. Lewis United States California, Sherman, Oaks, Codie, Road, 3930 (72) Inventor Mark, A.D. Lewis, Creek, Sycamore, Valencia, USA 27624 (72) Inventor Abraham. 18619 (56) Reference JP 62-37109 (JP, A) JP 51-88056 (JP, A) JP 59-28624 (JP, A) ) Actual development Sho 62-135927 (JP, U) Tokuheihei 4-503634 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 67/00 G01F 23/28

Claims (15)

(57) [Claims] 1. An apparatus for measuring a liquid level of a liquid medium in a container of an apparatus for solidifying a three-dimensional object by hardening a liquid medium, the first tank of the container containing the liquid medium. (30a), a second tank (40a) provided outside the first tank and connected to the first tank, the second tank (40a) having an upper opening and at least the second tank Measuring the liquid surface level of the liquid medium in the second tank and the second tank in which the liquid surface of the liquid medium in the tank is separated from the liquid surface of the liquid medium in the first tank. An apparatus comprising means for determining the liquid level of the liquid medium in the first tank from the measured liquid level of the liquid medium in the second tank. 2. The beam source for generating a measuring beam that does not cure the liquid medium, the beam directing means for causing the measuring beam to enter the liquid surface of the liquid medium in the second tank. And a sensor for detecting the measurement beam reflected by the liquid surface of the liquid medium in the second tank, the sensor outputting a different signal depending on the position of the measurement beam incident thereon. The device according to claim 1, wherein 3. The apparatus according to claim 2, wherein the beam source for generating the measurement beam is a laser. 4. The device according to claim 2, wherein the sensor is a two-cell photodetector. 5. The apparatus of claim 4, further comprising means for producing a signal from two separate signals generated by the two cell photodetector. 6. The first and second tanks are arranged so that the liquid levels of the liquid media in the first and second tanks are the same level, and the signal output from the sensor is An apparatus according to claim 2, characterized in that it indicates the liquid level of the liquid medium in the first tank. 7. The second wall is defined by a common wall adjacent to the second tank and connecting the first and second tanks with an opening submerged in a liquid medium. The device of claim 1, wherein the device is separated from the tank. 8. The apparatus of claim 1, further comprising means for adjusting a liquid level of the liquid medium, the means being connected to the determining means. 9. The apparatus of claim 8 wherein said means for adjusting comprises a plunger movable in and out of said liquid medium. 10. The apparatus of claim 9, further comprising a motor that moves the plunger into and out of the liquid medium. 11. The apparatus according to claim 10, wherein the motor moves the plunger based on a liquid level in the second tank measured by the determining means. 12. The apparatus according to claim 2, wherein the sensor is arranged at a fixed position with respect to the second tank. 13. The apparatus according to claim 2, further comprising a mirror for directing the measuring beam, the mirror being arranged in a fixed position with respect to the second bath. 14. The apparatus according to claim 2, wherein the liquid medium in the first tank and the liquid medium in the second tank are the same liquid medium. 15. A layer of a liquid medium is formed and cured on a layer formed in advance of a three-dimensional object in the process of being formed from a cured liquid medium, thereby substantially layer by layer. A three-dimensional modeling apparatus for modeling the three-dimensional object, comprising: a first tank (30a) of a container containing a liquid medium, the first tank in which the three-dimensional object is molded. Tank, means for immersing the three-dimensional object in the process of shaping below the liquid surface of the liquid medium in the first tank, provided outside the first tank, and connected to the first tank. Further, the second tank (40a) of the container is opened at an upper side, and at least the liquid surface of the liquid medium in the second tank is the liquid surface of the liquid medium in the first tank. A second tank separated from the second tank and a liquid level of the liquid medium in the second tank, and measuring in the second tank. An apparatus comprising means for determining the liquid level of the liquid medium in the first tank from the liquid level of the liquid medium.