JPH0685991B2 - Brightness distribution imaging type precision casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention heats and melts various casting materials by heating means such as high frequency induction type and electric resistance type, and improves the quality of small precision castings such as dental prostheses, restorations and ornaments with high quality. The present invention relates to a luminance distribution imaging type precision casting apparatus that can be efficiently manufactured.

Generally, the functions of the precision casting apparatus are classified into three: (a) heating and melting means for casting material, (b) determining means for pouring timing of molten metal (hereinafter referred to as casting timing), and (c) pressurizing means for casting pressure. The above (a) and (c) are stable even in the conventional device and are not a big problem.
It is customary that the operator of the above (2) decides visually by a conventional operator. The appropriate temperature for casting molten metal (hereinafter referred to as the casting temperature) is generally slightly higher than the melting point of the material, and its temperature range is extremely narrow. Overheating above this causes the crystal grains to become coarse, and the grain boundaries Impaired mechanical properties such as the inclusion of impurities in the product lead to defective products. On the other hand, if the temperature is lower than the proper temperature, melting will be insufficient, resulting in namera (insufficient casting) and the largest defect in the cast product. Therefore, the determination of the casting timing is the most important factor in the casting process, and it requires a high degree of skill to visually judge the suitability of the casting process. The loss is high especially in the dentistry which uses expensive materials. Therefore, various attempts have been made to replace the above-mentioned visual inspection method, such as a method of measuring the temperature of the molten material with a radiation thermometer or a method of controlling the melting time without controlling the temperature to control the casting timing. However, all of the methods have many problems, and it is difficult to determine the optimum casting timing practically and accurately, and the above-mentioned visual method still predominates. The present situation devised by the authors and left
"Precision casting method and its equipment" filed on May 21, 1959
Is a practical method and apparatus that is different from any of the above-mentioned methods and can easily and accurately determine the optimum casting timing, and has a much higher product yield than the visual method. That is, when the casting material is heated, it is difficult to uniformly heat the entire material by any means currently used, and therefore, as the heating of the material proceeds, a temperature distribution occurs in the material itself. The brightness per unit area of the radiated light emitted from each part of the material where the temperature distribution is generated, that is, the brightness distribution
It is detected by a self-propelled image detector called “rge coupled device” (hereinafter referred to as CCD image sensor), and this is displayed as a luminance distribution image on the screen of the image display, and the top of the distribution image is a straight line. When it is formed, it is set as a time point of complete melting, and the optimum casting timing can be determined for each material on the basis of this point. Therefore, the CCD image sensor with self-scanning that has excellent photodetection capability over a wide wavelength range from the visible light region to the infrared region of about 1000 nm has the peep window of the melting chamber clouded by the generated gas or metal vapor during melting. Also,
Since it accurately captures the brightness distribution image of the above material and displays it on the display, it is extremely easy to capture the time when the top of the material is straightened, and it does not require heat kneading at all, which has been a long-standing problem in the precision casting industry. It is a solution at once. However, in the case of a factory that mass-produces precision castings such as ornaments and industrial parts, an operator is required for each device, and there remains a problem that labor cannot be saved.

The present invention has been made in view of the above situation, solves the problem of the device by the "precision casting method and its device" that the inventors previously applied, and the luminance distribution imaged by the image detector of the device. It is intended to automatically determine the time when the top of the image forms a straight line. That is, the brightness distribution image of the casting material in the crucible melted by the heating means is detected by a one-dimensional or two-dimensional CCD image sensor,
This detected image is input to a microcomputer for storage and is also encoded into a binarized signal by signal processing. By comparing this with a reference signal, that is, an image in which the top is linearized, is compared with the same binarized signal, It is configured to perform pattern recognition (figure discrimination) with the reference image, automatically determine the time when the double-sided images match each other, and output a signal. With this structure, it is intended to provide a small-sized and inexpensive device with a simple structure that can be automatically cast at the optimum timing to produce a high-quality product efficiently and labor-savingly.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration block diagram of a high-frequency melting pressure precision casting apparatus as an embodiment. The melting section (1) shown by the cross section in the drawing comprises a cylindrical airtight melting chamber (2), a convex mold (3), and a mold stand (4) for supporting this mold. In the convex mold (3), the crucible (5) on the upper protruding portion, the mold cavity (6) and the runner (7) formed by the lost wax method are molded into one body, and the crucible (5) is formed. Is contained in the refractory tubular body (8), that is, in the melting chamber (2), and the convex mold base (9) is placed on the mold base (4) asbestos ring (1).
0) is supported through. The mold table (4) is pushed up from below by a predetermined pressure by a pneumatic cylinder piston or a compression spring on the central axis of a lower chamber (not shown), and the shoulder portion of the mold base (9) is asbestos packed (11).
It is in pressure contact with the outer surface part (12) of the bottom of the melting chamber via. The outer surface portion (12) is made of asbestos molding material and is fixed together with the upper casing (13) to a device upper casing (not shown), and the upper and lower ends of the fireproof tubular body (8) are airtightly engaged with each other. There is.
(14) is a high frequency induction coil, and (45) is a peep window made of a fireproof transparent material for sealing the upper part of the melting chamber. Further, the positions of the exhaust port for decompressing the melting chamber (2) and the inert gas inlet of about 5 kg / cm ² G for pressurizing when pouring the molten metal are indicated by white arrows (16) and black arrows (17). There is.

The above configuration is the same as that of the conventional apparatus, and the main part of the present invention is to image the luminance distribution of the casting material (M) in the crucible (5),
The configuration is described below in which the time point at which the top of the distribution image is flattened is automatically determined. Above peep window (1
A collecting lens (20) with a magnification of 10 is provided at a predetermined position on the central axis of 5). The collecting lens (20) is not limited to a single convex lens, and may be a compound lens, and a reflecting mirror may be used to change the optical axis (21) in any direction. The radiant light (22) emitted from the casting material (M) due to the progress of heating is applied to the photosensitive portion (24) of the one-dimensional CCD image sensor (23) fixed at the imaging position of the lens (20). ) Of the luminance distribution. The photosensitive portion (24) has a width of about 30 μm and a length of about 30 μm, for example.
30mm arrayed about 2600 pieces of photosensitive pixels in a row during, wherein the photoelectric conversion and accumulated signal charges transferred within the analog shift register, the time-series analog voltage signal (S _A) the output To do. This signal (S _A ) is input to the A / D converter (27) of the microcomputer (26) surrounded by the alternate long and short dash line. As is well known, the microcomputer (26) is composed of a micro processor (cpu), a main memory, an auxiliary memory, an input / output device, etc., but they are not shown and the function realizing means of the present invention is shown in a block diagram. And the program written in the main memory is
This will be described with reference to the flowchart of FIG. The back to the original (S _A) signal is A / D converter (27) in example 1
It is converted into a 2-bit digital image signal (D ₁ ) and, for example, a luminance distribution image storage means (2
8) read in. Here, the procedure of encoding the luminance distribution image will be described with reference to FIGS. FIG. 2 shows, for example, 60 se from the start of heating the casting material (M) in the crucible (5).
c shows a state in which there is a difference in brightness between the outer peripheral portion and the central portion after the passage of time, Figure ▲ A ₁ ▼ is a plan view as seen through the observation window, and Figure ▲ B ₁ ▼ is read into the image memory (28) above. It is an image signal (I ₁ ) having a different brightness distribution. In Figure ▲ A ₁ ▼, (5H) indicates the upper surface of the crucible wall, the shaded area (H / B) of the material (M) indicates the high brightness area, and the central circle indicates the low brightness area (LB) and the arrow ( a) is the self-scanning direction of the CCD image sensor (23). Figure ▲ B ₁ ▼ shows the brightness distribution with each position (P) in the direction (a) above as the horizontal axis and brightness (B) as the vertical axis.
(D) Corresponds to the inner diameter of the crucible (5). The image signal (I ₁ ) is based on the luminance (B ₅ ) of the crucible wall, has a bimodal shape, and has a fine variation. Third
Figure ▲ A ₂ ▼ shows that heating progresses, for example, ₁₀ seconds from Figure ▲ A ₁ ▼
The state in which the material (M) has completely melted over time is shown in the figure ▲
B ₂ ▼ is an image signal (I ₁ s) of the brightness distribution, and the top part thereof forms a flat plateau with a thin rising shape. The reason why the luminance distribution is uniform is that the material (M) is completely melted and its temperature is uniform, and the above-mentioned patent application "Precision casting method and its apparatus" is an image display device. By this, it is possible to visually judge when a similar image (L ₁ s) appears on the screen as shown in Fig. B ₂ . The present invention replaces the above visual judgment with the automatic judgment by the video coding. Returning to FIG. 1, the image signal (I ₁ ) of the memory (28) is input to the image binarizing means surrounded by the solid line (29). The means (29) may have various configurations, but the four means (30) to (3) shown in the figure as another embodiment.
The process of 3) will be described by sequentially using FIG. 2 and FIG. First distribution image smoothing means (30) smoothes fine variations in image signal (I ₁₎ shown in FIG. 2 ▲ B ₁ ▼, Figure 2 ▲ C ₁
The smoothed image signal (I ₂ ) from which fine fluctuations have been eliminated is input to the image shaping means (31) as indicated by ▼. The image shaping means (31) is a kind of function generating circuit which forms the smoothed image signal (I ₂ ) by a plurality of approximated polygonal lines (straight lines) and has a bimodal shape as shown in Fig. 2 (D ₁₎ . The image (I ₂ ) is shaped with, for example, 7 broken lines. This shaped image signal (I ₃ ) is input to the following differential processing means (32), and the four gradients (I ₃₁ ), (I ₃₂ ), (I ₃₃ ), of the two-dimensional image signal (I ₃ ),
The respective starting points (P ₁ ) (P ₂ ), (P ₃ ), of (I ₃₄ ),
One-dimensional differentiation consisting of four pulses with amplitudes (Ic ₁ ) to (Ic ₄ ) and pulse widths (W ₁ ) to (W ₄ ) corresponding to the above gradients, with (P ₄ ) as the pulse rising point. Converted to image signal (I ₄ ). This signal (I ₄ ) is further input to the encoding means (33),
For example, using a threshold value of the crucible wall brightness (B ₅ ) as a threshold, a signal higher than that (H) or (1) and a signal lower than that as (L) or (O) are converted into a binarized signal (D ₂ ), and a binary value is obtained. The output signal of the conversion means (29). The binarized image signal (D ₂ ) is used for correlation determination means (34), which is, for example, a counter.
Input to one of the input terminals (34A) and the other terminal (34A)
In B), a reference image signal (Ds) indicating completion of melting set in advance is always input to the reference signal output means (35) as a test pattern. The reference image signal (Ds) is two binarized signals of (H ₁ ) and (H ₂ ) as shown in FIG. 3 (F ₂ ), and the correlation judging means (34) is (H).
The numbers of the signals are compared, and the pulse interval (L) is not a comparison target. Therefore, when it has four (H) s like (D ₂ ) in Fig. ₂ (F ₁ ), the means (34) does not judge that there is no significant difference and does not emit any signal. . Therefore, the heating control device (37) drives the high frequency power supply (38) with a predetermined control amount, for example, 100%, which is set at the time of starting, and continues heating. (39) is an AC power supply. In this way, as the heating of the material (M) in the crucible (5) progresses, the temperature of the material (M) rises, exceeds the melting point, and when the casting timing is reached, as shown in Figure 3 (A ₂ ), the center of the material (M) is reached. The low luminance area (L / B) disappears, the luminance (B) in the high luminance area (H / B) is also high (Bm), and the entire material has the same luminance. Therefore, the image signal (I ₁ s) of the brightness distribution imaged by the CCD image sensor (23) has the maximum brightness distribution at the top of the crucible wall brightness (B ₅ ) as shown in Fig. ▲ B ₂ ▼. The brightness (Bm) becomes almost linear with some fluctuations. When this image signal (I ₁ s) is subjected to signal processing by the smoothing means (30) and shaping means (31) in the same manner as described above, it is converted into (I ₂ s) and (I ₃ s), and as shown in FIG. since ₂ ▼ to indicate shaping the image signals (I ₃ s) the top portion is flat in charge, output or FIG ▲ E ₂ ▼ differential image signal of differential processing means (32) (I ₄
s) The amplitude (I
c ₁ ), (Ic ₂ ), and pulse width (W ₁ ) (W ₂ ), which are approximated by two pulses, and no pulse is generated between them. This is a large difference from the signal (I ₄ ) in Fig. 2 (E ₁ ), which enables automatic determination. The differential image signal (I ₄ s) is further converted to the encoding means (33) shown in FIG _{▲ F 2 ▼ (H 1)} 2 binarized signal (H ₂₎ (D's), correlation determination means It is input to (34). As described above, since the binary signal of the above (Ds) is always set and input as the test pattern in this means (34), it becomes (D's = Ds), and the judging means (34) records. It is determined that there is no significant difference between the image binarization signal (D's) and the reference image binarization signal (Ds) indicating the completion of melting, that is, if they match, the determination signal (S ₁ ) is output as the casting signal. Output to the circuit (40). This circuit (40) has two output signals (S ₂ )
(S ₃ ) is output and the signal (S ₂ ) is the mooring time setting device (41).
Then, the signal (S ₃ ) is input to the heating control device (37). The mooring time setting device (41) is for presetting how many seconds the completely melted state is to be held, corresponding to the type of casting material and the casting amount, and can be arbitrarily set from 0 seconds to several seconds. The signal (S ₃ ) controls the heating control device (37) to change the high frequency current (i) to a predetermined set decreasing value.
_{H 2} ) is gradually decreased, and the material is kept warm during the holding time.
When the set hold time has elapsed, the setting device (41) outputs a pouring signal (S ′ ₂ ) to the casting pressure pressurizing device (42), and the pressurizing device (42) outputs, for example, the pressure source (43). Argon gas of 5 kg / cm ² G was introduced into the melting chamber (2) through the gas inlet (17), the surface of the molten metal (M) was pressurized, and the mold cavity (6) was passed through the runner (7). ) Press into. The mooring setting device (41) outputs the signal (S ′ ₂ ) and simultaneously outputs the signal (S ₄ ) to the heating control device (37) to stop the supply of the high frequency current (i _H ).

Next, the program written in the ROM which is the main memory of the microcomputer will be described with reference to FIGS. FIG. 4 shows the entire casting process, and FIG. 5 shows the detailed processing procedure of the defined processing step (46) in FIG. In step (45), the data in the memory (28) is erased and all the circuits are returned to the initial state. Next step (4
6) will be explained with reference to FIG. In step (47), an appropriate melting power, for example, a high-frequency current value, which is determined by the type of casting material and its casting amount, is set. Next, in step (48), a casting pressure, for example, 5 kg / cm ² G is set by the pressurizing device (42).

When the above is completed, the step (49) is to put the casting material (M) in the crucible (5) and set the convex mold (3) as shown in FIG. Mouth (1
The inside of the melting chamber (2) is depressurized through 6) by a vacuum exhaust device (not shown) to, for example, about 10 ^-2 Torr, and an inert gas is introduced at a low pressure. Depending on the type of casting material, the step (50) may only perform the above-mentioned depressurization. After the above preparation is completed, the heating control device is turned on to start heating in step (51). Returning to FIG. 4, step (53) is the first
Corresponding to the operation of the CCD image sensor (23) to the luminance distribution image storage means stage (28) in the figure, steps (54) to (57) correspond to one of the image binarization means (29) in FIG. It corresponds to each means of (30) to (33) which is an embodiment. In step (58), between the signals (H) and (L) corresponding to the distribution image input by the binarizing means every moment and the preset reference signal obtained by binarizing the flat distribution image. That is, there is no significant difference, that is, it is a step of judging whether or not the number of (H) of the input image binarized signal matches two of the reference image binarized signals. In this determination, heating is continued until the number of (H) in the input signal becomes two, and the image binarizing means is also repeated. If (YES), move to step (59). This corresponds to the judgment signal (S ₁ ) of the correlation judging means (34) shown in FIG. ₁ being output, and the casting signal output circuit (40) outputs signals (S ₂ ) (S ₃ ) and moored. The next step (60) corresponding to the operation of the time setting device (41) and the heating control device (37) determines whether or not the predetermined time set in the mooring time setting device (41) has ended. In step (61), pouring is performed by the pouring signal (S ′ ₂ ) of the setting device (41). Although not shown in FIG. 1, the last step (62) is a step for automatically determining the end point of a predetermined solidification time by starting a timer or the like with a pouring signal (S ′ ₂ ). Is.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the drawings and the description. For example, the casting apparatus is not limited to the high frequency melting pressure type, but may be an electric resistance furnace type or a heating element crucible type. The CCD image sensor is not limited to the one-dimensional sensor, and the same brightness distribution image can be taken by replacing the self-scanning function of either the X or Y axis of the two-dimensional sensor with the averaging function.
The correlation determining means (34) is not limited to the counter, and can be performed using a shift register or an Exclusive-OR circuit. Further, the image binarizing means is not limited to the four processes of smoothing, shaping, differentiating, and encoding, and for example, the delta-modulating binarizing means used for television image transmission, that is, a stepped wave capable of changing the image by ± 1. By approximating and binarizing this staircase wave when it is one step higher than the previous level (1) and when it is lower (0), a 1-bit value is obtained for each sampling point (extracted amplitude width at predetermined intervals). Means for obtaining a binarized signal that approximates a staircase by only assigning pulses can also be applied to the present invention.

Since the present invention is configured as described above, the yield of cast products is improved by automatically and accurately determining the casting timing, which has been forced to rely on the visual judgment of the skilled person while being devised variously in the conventional precision casting. Is to dramatically improve. That is, the radiation thermometer, which is expensive and difficult to measure accurately, is small and inexpensive, and the influence of gas and metal vapor in the melting chamber is small, and the melting state of the material is accurately imaged by its brightness distribution image. A CCD image sensor is used as a detector, and a microcomputer is used to perform pattern matching between the detected image and the completely melted image by the binarized correlation of both images. In addition, it is possible to provide a convenient device capable of automatically pouring molten metal at an optimum casting timing and efficiently producing a high-quality cast product.

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of a high-frequency melting pressure precision casting apparatus as an embodiment of the present invention, and FIGS. 2 and 3 are luminance distribution images of the casting material in the above apparatus during heating and during complete melting, respectively. binarizing means is a diagram illustrating a FIG ▲ a ₁ ▼
Is a plan view of the material being heated, Figure ▲ A ₂ ▼ is a plan view of the above material when it is completely melted, Figure ▲ B ₁ ▼ ▲ B ₂ ▼ is the brightness distribution memory image of each of the above, and Figure ▲ C ₁ ▼ ▲ C ₂ ▼ is a smoothed image diagram of each of the above, ▲ D ₁ ▼ ▲ D ₂ ▼ is a shaped image diagram of each of the above, ▲ E ₁
▼ ▲ E ₂ ▼ is each of the above differential images, Fig. ▲ F ₁ ▼ ▲ F ₂ ▼ is each of the above binarized signals, Fig. 4 is a flowchart showing the casting program of the microcomputer of the above apparatus, and Fig. 5 is 4 is a flowchart of the melting sequence steps of FIG. (2) ... Melting chamber, (3) ... Convex mold, (5) ... Crucible, (6) ... Mold cavity, (M) ... Mold material,
(14), (37), (38), (39) ... Heating means (for example, high frequency induction heating device), (20) ... Collective lens, (2
3) …… Self-scanning image detector (CCD one-dimensional image sensor), (S _A ), (D ₁ ) …… The image signal of the above detector,
(28) …… Brightness distribution image storage means, (I ₁ ) (I ₁ s) …… Brightness distribution storage image signal, (29) …… Image binarization means,
(D ₂ ) ・ (D's) …… Binarized signal, (Ds) …… Reference 2
Quantized signal, (30) …… Distributed image smoothing means, (31) …… Image shaping means, (32) …… Differentiation processing means, (I ₄ ), (I ₄ s)
...... Differential image, (33) …… Encoding means, (34) …… Correlation judging means, (S ₁ ) …… Judgment signal, (40) …… Casting signal output circuit, (S ₂ ) …… Mooring signal , (S ′ ₂ ) …… Pouring signal

Claims (3)

[Claims] 1. An electric heating / melting chamber for melting a small amount of casting material contained in a crucible, a collecting lens for imaging a heating progress state of the material, and a luminance distribution image of the material through the lens. A self-scanning image detector that picks up an image and outputs the image signal, a brightness distribution image storage unit that sequentially stores the image signals output from each pixel of the detector in time series, and the stored image. A binarized signal in which the luminance of the inner wall of the crucible is a threshold value, a high-luminance image that exceeds the threshold value is a signal (1) or (H), and a low-luminance image that does not reach the threshold value is a (0) or (L). The image binarizing means for converting to and outputting and the binarizing signal output by the binarizing means is compared with a preset reference binarizing signal indicating completion of melting, and a correlation determining means for determining whether they match. Based on this judgment, The power for heating the molten material of the inner,
A mold signal that gradually reduces to a preset diminution value by the heating control device and moored this diminished power for a predetermined time through a mooring time setting device, and then outputs a signal for pouring the molten material into the mold. A luminance distribution imaging type precision casting apparatus, which is provided with an output circuit. 2. Image binarizing means for image processing, smoothing,
The brightness distribution image pickup type precision casting apparatus according to claim 1, which goes through four steps of shaping, differentiating and encoding. 3. The brightness distribution imaging type precision casting apparatus according to claim 1, wherein the electrically heating and melting chamber is a heating and melting chamber of a high-frequency induction heating device.