JP2008137315A - Method of detecting sink in injection molding, injection molding machine and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of detecting sinks in injection molding, which costs low which can certainly detect the sinks generated in a molded product on the molding process. <P>SOLUTION: The method comprises installing the IR temperature sensor 50 in the mold 30 in the position that contacts the molten resin injected into the cavity 32, measuring continuously the temperature of when the molded product cools by this IR temperature sensor 50, detecting the presence or absence of an inflection point in the obtained temperature change curve, and deciding that the sinks are generated in the molded product when there exists the inflection point. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sink detection method, an injection molding machine, and an injection molding method in injection molding. More specifically, the sink detection method using a temperature sensor, and the presence or absence of sink marks in a molded product are detected by the temperature sensor. And an injection molding method using the same.

  Conventionally, resin molded products molded by injection molding, especially thick parts, often have defects due to sink marks. These sink defects are generally selected by visual inspection of the molded products. Has been.

  On the other hand, as a sink detection method not based on appearance inspection, a method using ultrasonic waves disclosed in Patent Document 1 is known. In this method, an ultrasonic probe is provided in a mold for injection molding, and the presence or absence of sink marks generated in the molded product is detected based on the presence or absence of reflected ultrasonic waves transmitted toward the mold cavity. It is.

Japanese Patent Laid-Open No. 4-101821

  However, in the case of visual appearance inspection, since an inspection process by an inspector is required after molding, there is a problem that the cost for the inspection process increases. Furthermore, since the molding process and the inspection process are separate processes, the problem of sink defects detected in the inspection process cannot be utilized for quick response such as changing the molding conditions in the molding process. There were problems such as producing defective products.

  In addition, in the detection method using ultrasonic waves as described in Patent Document 1, the presence or absence of sink marks can be detected in the molding process, but the ultrasonic device attached to the mold is expensive. In addition, there is a problem that small sink marks generated in the molded product cannot be reliably detected.

  The problem to be solved by the present invention is a low-cost method for detecting sink marks in injection molding capable of reliably detecting sink marks generated in a molded product in a molding process, and an injection molding machine and injection molding using the same. It is to provide a method.

  In order to solve the above-described problem, the sink detection method in injection molding according to the present invention is provided with a temperature sensor in a mold at a position in contact with the molten resin injected into the cavity as described in claim 1, The temperature sensor continuously measures the temperature when the molded product is cooled, detects the presence or absence of an inflection point in the obtained temperature change curve, and if the temperature change curve has an inflection point, sinks the molded product. The gist of this is to determine that this has occurred.

  In this case, as described in claim 2, the temperature sensor is preferably an infrared temperature sensor, and as described in claim 3, the temperature sensor is located at a position where sink marks of the molded product are likely to occur. It is more preferable if it is provided.

  In order to solve the above problems, an injection molding machine according to the present invention includes, as described in claim 4, a temperature sensor provided in a mold so as to abut against a molten resin injected into a cavity, The temperature sensor continuously measures the temperature during cooling of the molded product, detects the presence or absence of an inflection point in the obtained temperature change curve, and if there is an inflection point in the temperature change curve, sinks in the molded product. And a distribution unit that distributes the molded product into a non-defective product and a defective product based on the presence or absence of the sink of the molded product determined by the sink detection unit. Is.

  In this case, as described in claim 5, it is preferable that the temperature sensor is an infrared temperature sensor, and as described in claim 6, the temperature sensor is at a position where sink marks of the molded product are likely to occur. It is more preferable if it is provided.

  In order to solve the above problems, an injection molding method according to the present invention continuously performs injection molding using the injection molding machine according to claims 4 to 6, and the molded product is divided into a good product and a defective product. The gist is that only good products are obtained by dividing.

  According to the method for detecting sink marks in injection molding according to the present invention, when sink marks occur in a molded product by providing a temperature sensor at a position where it contacts the molten resin injected into the cavity, the molded product and temperature Since the sensor is separated, an inflection point is generated in the temperature change curve in the molded product cooling process measured by the temperature sensor. Therefore, it is possible to determine the presence or absence of sink defects simply by determining the presence or absence of an inflection point that occurs in the temperature change curve. Generated sink marks can be reliably detected in the molding process.

  In this case, if the temperature sensor is an infrared temperature sensor, an inflection point in the temperature change curve can be reliably detected. Further, if the temperature sensor is provided at a position where sink marks are likely to occur in the molded product, molding defects due to the occurrence of sink marks are almost never missed.

  Further, according to the injection molding machine and the injection molding method according to the present invention, the presence or absence of an inflection point in the molded product is detected based on the presence or absence of an inflection point in the temperature change curve measured by the temperature sensor, and the detected information Based on the above, the molded product is divided into a non-defective product and a defective product. Therefore, after the molding process is finished, the molded product is automatically sorted into a non-defective product and a defective product, so that sorting by an appearance inspection after the molding process is unnecessary.

  In this case, similarly to the above, if the temperature sensor is an infrared temperature sensor, the inflection point in the temperature change curve can be reliably detected, and the temperature sensor is provided at a position where the sink of the molded product is likely to occur. If this is the case, molding defects due to the occurrence of sink marks are hardly missed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a side view of an injection molding machine 10 according to the present embodiment. In the injection molding machine 10, an injection unit 20 and a mold drive unit 40 are attached to a vertically standing base 11, and a molded product distribution unit 60 (corresponding to a distribution means according to the present invention) is provided under the base 11. Is provided. Hereinafter, each part will be specifically described.

  The injection unit 20 is mainly formed by attaching a heating cylinder 24 and an injection servo motor 26 for rotating the injection screw 27 on a base 22 attached on the base 11. A hopper 25 is attached to the heating cylinder 24, and resin pellets as raw materials are supplied from the hopper 25 to the heating cylinder 24 and melted in the cylinder. An injection nozzle 29 is attached to the tip of the heating cylinder 24, and the injection screw 27 advances by rotating the injection servomotor 26, and the molten resin in the heating cylinder 24 is attached to the fixed side plate 28. It is injected into the fixed mold 30a.

  The mold drive unit 40 mainly includes a mold clamping cylinder 42 which is a hydraulic cylinder mounted on the base 11 via a cylinder mounting plate 44, and a movable side plate 46 connected to a drive shaft 42a of the mold clamping cylinder 42. It consists of and. A movable mold 30b is attached to the movable plate 46, and the movable mold 30b can be moved back and forth in the direction of the fixed mold 30a using the clamping cylinder 42 as a drive source. The guide shaft 48 provided on the cylinder mounting plate 44 is inserted into the movable side plate 46 so that the movable side mold 30b is restricted from rotating.

  Further, an infrared temperature sensor 50 for detecting infrared heat ray radiation is attached to the movable mold 30b. FIG. 2 shows a sectional view of the mold 30. As shown in the figure, the infrared temperature sensor 50 is provided so that the tip thereof faces the cavity 32 which is a molding space in the mold 30. The infrared temperature sensor 50 is provided at a place where two sinks are likely to occur due to the shape of the molded product, such as a thick part of the molded product or a location where a rib is provided (two locations in the figure). Therefore, the number varies depending on the product to be molded.

  The molded product sorting unit 60 mainly includes an air cylinder 64 mounted on a base plate 62 via a cylinder mounting plate 66, a good product shooter 68a, and a defective product shooter 68b. An inclined block 70 is connected to the drive shaft 64 a of the air cylinder 64. The inclined block 70 is slidably mounted on a guide rail 72 disposed in the direction of the drive shaft 64a on the base plate 62.

  A control box 74 for controlling the driving of the air cylinder 64 based on a signal obtained from the infrared temperature sensor 50 is provided under the base plate 62. Further, an electromagnetic valve 76 for switching an air flow path for moving the air cylinder 64 forward and backward is attached to the side surface of the control box 74.

  FIG. 3 shows an electrical configuration diagram of the molded product sorting unit 60 around the control box 74. The temperature data measured by each infrared temperature sensor 50 is sent to a distribution unit control circuit 61 (corresponding to the sink detection means according to the present invention) via an amplifier 51 provided in a pair with each infrared temperature sensor 50. ). The distribution unit control circuit 61 performs opening / closing control of the electromagnetic valve 76 connected to the air cylinder 64 based on the temperature data.

  Here, a method for detecting sink marks in injection molding by the infrared temperature sensor 50 provided in the movable mold 30b will be described with reference to the following experimental example.

(Experimental example)
When the injection molding machine 10 was used for injection molding under certain molding conditions, the temperature change during cooling of the molded product from the first shot to the ninth shot at the start of molding was continuously measured by the infrared temperature sensor 50. FIG. 4 is a temperature change curve from the first shot (No. 1) to the ninth shot (No. 9) measured at this time. Sink defects have occurred.

  In general, it is known that immediately after the start of production by injection molding, sink defects are likely to occur in a molded product due to the influence of the mold temperature and the temperature of the molten resin not being sufficiently high. Also in this experimental example, sink marks were generated in the molded product from the first shot to the eighth shot, resulting in a defect, but in the ninth shot, a good product having no sink marks could be obtained.

  Here, as shown in FIG. 4, the temperature change curve from the first shot to the eighth shot is inflected into the temperature change curve at about 1.2 to 1.3 seconds from the start of cooling of the molded product. It can be seen that the point P is generated. The size of the inflection point P becomes smaller every time molding is repeated, and no inflection point occurs in the temperature change curve of the ninth shot.

  That is, when sink marks occur in the molded product, the surface of the infrared temperature sensor 50 and the surface of the molded product are separated from each other, resulting in an inflection point in the temperature change curve during cooling. On the other hand, when sink marks do not occur in the molded product, it becomes a monotonically decreasing temperature change curve like the curve of No. 9. Therefore, based on the presence or absence of an inflection point in the temperature change curve measured by the infrared temperature sensor 50, it can be determined whether or not sink marks have occurred in the molded product without depending on the appearance inspection.

  Next, an injection molding method in which such a sink detection method is applied to the above-described injection molding machine 10 will be described. FIG. 5 is a flowchart for explaining a resin product molding process by the injection molding machine 10.

  First, after inputting the target production number (N) by operating an operation panel (not shown) and then pressing the start switch (S501), the main servo control circuit of the injection molding machine 10 causes the injection servo motor 26, the clamping cylinder 42, and the like. Is in-origin (S502).

  At this time, when it is detected that any of the actuators such as the injection servo motor 26 and the mold clamping cylinder 42 is not in the original position (S502 “NO”), the injection molding machine 10 is started by the interlock mechanism. There is no (S503).

  When it is confirmed that all of the actuators whose original positions should be confirmed are located at the original positions (S502 “YES”), the mold clamping cylinder 42 moves forward, and the movable mold 30b is pressed against the fixed mold 30a. The mold is clamped (S504). Thereafter, the injection servo motor 26 is rotationally driven (S505), and the molten resin in the heating cylinder 24 is injected into the cavity 32 of the mold 30.

  When the injection of the molten resin is completed (S506) and the molded product cooling process is started, the infrared temperature sensor 50 starts temperature measurement (S507). And after completion | finish of cooling of a molded article (S508), the temperature measurement of the infrared temperature sensor 50 is complete | finished (S509).

  After the temperature measurement is completed, the distribution unit control circuit 61 in the control box 74 analyzes the temperature change curve measured by the infrared temperature sensor 50 and determines whether or not an inflection point has occurred in the temperature change curve. (S510). At this time, if it is determined that an inflection point has not occurred in the measured temperature change curve (S510 “NO”), the mold clamping cylinder 42 is immediately retracted (S511), and the mold 30 is provided. The workpiece 99 is dropped and discharged toward the non-defective shooter 68a by an ejector pin (not shown).

  Thereafter, the production number n is counted up (S512), and it is determined whether or not the counted production number (n + 1) has reached the target production number (N) (S513). When it is determined that the target production number (N) has been reached (S513 “YES”), the injection molding machine 10 stops, and the production ends (S514). On the other hand, if it is determined that the target production number N has not yet been reached (“NO” in S513), the process returns to step S504, and the injection molding of the next cycle is performed.

  On the other hand, if it is detected in step S510 that an inflection point has occurred in the temperature change curve (“YES” in S510), it is determined that a sink defect has occurred in the work 99, and the distribution unit is determined. In response to a command from the control circuit 61, the solenoid valve 76 switches the air flow path, and the air cylinder 64 moves forward in the direction of the arrow X in FIG. 1 (S515). After the air cylinder 64 moves forward, the mold clamping cylinder 42 moves backward (S516), and the work 99 in which sink defects have occurred is dropped and discharged by the ejector pin.

  Then, as shown in FIG. 1, since the inclined block 70 fixed to the drive shaft of the air cylinder 64 has advanced to the position indicated by the dotted line in the drawing, the entrance of the non-defective shooter 68a is blocked. It becomes a state. Then, the work 99 that has fallen toward the non-defective product shooter 68a rolls on the inclined surface of the inclined block 70 and is dropped into the defective product shooter 68b.

  Thus, after the defective product is discharged from the mold 30 and sorted separately from the non-defective product, the air cylinder 64 moves backward (S517) and returns to the original position. And it returns to step S504 and the injection molding of the next cycle will be performed.

  As described above, according to the injection molding method according to the present embodiment, the infrared temperature sensor 50 determines whether there is a sink defect occurring in the workpiece 99 based on the presence or absence of the inflection point of the temperature change curve when the workpiece 99 is cooled. When a bending point occurs, it is assumed that a sink defect has occurred, and the molded product distribution unit 60 automatically distributes the product into a non-defective product and a defective product. Therefore, distribution by appearance inspection after molding becomes unnecessary, and sink marks occurring in the molded product can be reliably detected in the molding process.

  In addition to the configuration of the injection molding method described above, if a sink defect of the workpiece 99 is continuously detected, the operation of the injection molding machine 10 is stopped and the operator is informed that the defect has continuously occurred. You may do it. By doing in this way, it is possible to prevent in advance a large amount of defective products from occurring, and it is possible to quickly respond to changes in molding conditions and the like.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, it has been explained that the inclined block 70 is advanced and retracted by the air cylinder 64, so that the molded product is divided into the non-defective product and the defective product. However, the product can be reliably classified into the good product and the defective product. The method is not limited to this. For example, a non-defective product and a non-defective product may be distributed by controlling a take-out robot generally used in the injection molding process based on temperature change curve data.

It is a side view of the injection molding machine concerning one embodiment of the present invention. It is sectional drawing of the metal mold | die for injection molding used for the injection molding machine shown in FIG. It is an electrical block diagram of the molded article distribution unit arrange | positioned at the injection molding machine shown in FIG. It is a temperature change curve at the time of measuring the temperature change at the time of cooling of the molded article from the 1st shot of the start of molding to the 9th shot in the case of injection molding under a certain molding condition with an infrared temperature sensor. It is a flowchart for demonstrating the shaping | molding process in the injection molding machine shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Injection molding machine 30 Mold 32 Cavity 50 Infrared temperature sensor 60 Molded product distribution unit 61 Control circuit for distribution unit

Claims (7)

  A temperature sensor is provided in the mold at a position where it abuts the molten resin injected into the cavity, and the temperature at the time of cooling the molded product is continuously measured by the temperature sensor, and the inflection point in the obtained temperature change curve is measured. A method for detecting sink marks in injection molding, wherein the presence or absence is detected and it is determined that sink marks have occurred in a molded product when the temperature change curve has an inflection point.   The method for detecting sink marks in injection molding according to claim 1, wherein the temperature sensor is an infrared temperature sensor.   3. The method for detecting sink marks in injection molding according to claim 1, wherein the temperature sensor is provided at a position where sink marks are likely to occur in a molded product.   A temperature sensor provided in the mold so as to come into contact with the molten resin injected into the cavity, and a temperature change curve obtained by continuously measuring the temperature when the molded product is cooled by the temperature sensor. Based on the presence or absence of sink marks in the molded article determined by the sink detection means, which detects the presence or absence of points, and determines that sink marks have occurred in the molded article when the temperature change curve has an inflection point. An injection molding machine comprising a sorting means for sorting the molded product into a non-defective product and a defective product.   The injection molding machine according to claim 4, wherein the temperature sensor is an infrared temperature sensor.   6. The injection molding machine according to claim 4, wherein the temperature sensor is provided at a position where sink marks of the molded product are likely to occur.   7. An injection molding method characterized in that injection molding is performed continuously using the injection molding machine according to claim 4 and only good products are obtained by distributing molded products into good products and defective products. .

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