JP2009137076A - Injection molding mold, method for detecting defective plasticization in injection molding, and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding mold which can cheaply and easily detect the defect of a plasticization process in injection molding, a method for detecting defective plasticization, and an injection molding method. <P>SOLUTION: The mold 10 which has a cavity 13 inside and in which an ejector pin 18 with a pressure sensor is attached to a cold slug well 15 just under a sprue 14 is used. In the cooling and plasticization process, when the pressure of a resin in the mold measured by the pressure sensor is deviated from a prescribed range, it is distinguished that a molding 1 is defective in plasticization. The molding defective in plasticization is removed to carry out injection molding. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection mold in injection molding, a method for detecting poor plasticization, and an injection molding method.

  The plasticizing process in injection molding is a process with many variations. There are many defects due to variations in plasticization. For example, if the plasticization measurement is insufficient, short shots and sink marks occur. On the other hand, if the plasticization measurement is excessive, burrs are generated. Further, if degassing due to plasticization is insufficient, molding defects such as silver and voids occur. Therefore, in order to perform injection molding satisfactorily, it is necessary to detect an abnormality in the plasticizing process (plasticizing abnormality) using a pressure sensor or the like.

  Conventionally, many methods for attaching a sensor to a molding machine such as a cylinder or a nozzle have been proposed as means for detecting plasticization abnormality in injection molding. Further, as described in Patent Document 1, a method of providing a plasticizing characteristic evaluation device between a nozzle and a mold is known.

JP 2000-263618 A

  However, when a sensor or the like is provided on the molding machine side, the cylinder or nozzle of the molding machine has a temperature of 200 ° C. or higher, and depending on the resin to be molded, it has a high temperature of 300 ° C. or higher. Etc. are concerned. In addition, since cylinders and nozzles are required to have high heat resistance and durability, very hard metal is often used, and there has been a problem that the processing cost when mounting a sensor or the like increases. .

  Further, when the plasticizing characteristic evaluation device is provided at the tip of the nozzle as described in Patent Document 1, the high-temperature nozzle is in close contact with the plasticization evaluation device, as in the case of attaching a sensor or the like to the molding machine. For this reason, the plasticizing evaluation apparatus is still at a high temperature, and the plasticizing evaluation apparatus is required to have heat resistance, and thus becomes expensive.

  The problem to be solved by the present invention is to solve the above-mentioned problems, and it is possible to easily detect defects in the plasticizing process at low cost and to detect defective plasticization in injection molding. It is to provide a method and an injection molding method.

  In order to solve the above problems, an injection mold according to the present invention is characterized in that a pressure detection means for measuring a resin pressure of a cold slug well immediately below a sprue is provided in the mold.

  In the injection mold, the pressure detection means is preferably an ejector pin having a pressure detection function.

  The method of detecting plasticization failure in injection molding of the present invention uses a mold provided with pressure detection means for measuring the resin pressure of the cold slug well immediately below the sprue, and the pressure in the plasticizing process at the time of injection molding The gist is that when the pressure of the resin in the mold measured by the detection means is out of a predetermined range, it is determined that the molded product has poor plasticization.

The injection molding method of the present invention includes an injection step of injecting a plasticized resin from an injection nozzle into a mold cavity, a pressure holding step of holding the resin in the cavity at a predetermined pressure, and the resin in the cavity at a predetermined temperature. In the injection molding method that sequentially performs a cooling / plasticizing step of plasticizing a resin with a plasticizing device while cooling the mold until it becomes, and a step of taking out the molded product by opening the mold after cooling is completed,
Using a mold provided with pressure detection means for measuring the resin pressure of the cold slug well immediately below the sprue, the pressure of the resin in the mold measured by the pressure detection means in the cooling / plasticizing process is predetermined. If it falls outside the range, the gist is to determine that the molded product is poorly plasticized and to remove the molded product having poor plasticization.

  In the above injection molding method, a pressure profile curve is created from the pressure of the resin in the mold in the cooling / plasticizing process, and a plasticization failure is determined by comparison with the pressure profile curve in the cooling / plasticizing process of normal injection molding. It is preferable to perform molding at a mold temperature of 150 ° C. or lower.

  The present invention can grasp the profile of the pressure applied to the molded article in real time during molding by using the pressure detection means for measuring the resin pressure of the cold slug well immediately below the sprue. In particular, when the resin pressure of the cold slag well portion is measured, when normal plasticization is performed in the plasticizing process, a pressure change characteristically appears in this portion, but if abnormal plasticization occurs, this It was found that the pressure change in the part was different. This pressure change cannot be detected when the pressure detecting means is provided at a portion other than the cold slug well portion. By measuring the pressure of the resin in the mold in the cooling and plasticizing process by the pressure detecting means provided in the cold slag well in this way, it is determined whether the pressure is within a predetermined range. It is possible to determine the presence or absence of poor plasticization of the molded body in the mold.

  Since the temperature of the mold is generally less than 200 ° C. and is lower than the temperature of the molding machine, it is a temperature at which a pressure sensor or the like can be used normally, and the cost does not increase. Further, when the pressure sensor is provided in the mold, the processing is easier and the processing cost does not increase compared to the case where the pressure sensor is provided in the molding machine. Therefore, according to the injection mold of the present invention, the method for detecting poor plasticization in injection molding, and the injection molding method, it is possible to easily detect defective plasticization processes and to reduce the cost of the entire injection molding apparatus. Can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view schematically showing an injection mold according to the present invention. As shown in FIG. 1, an injection mold 10 (hereinafter sometimes simply referred to as a mold) includes a fixed mold 11 and a movable mold 12, and has a cavity 13 therein. The mold 10 is connected to a molding machine 20 including a cylinder portion 21 for plasticizing a resin and an injection nozzle 22 for injecting the resin, and is formed in the cavity 13 so that the molding resin can be injected.

  A mold 10 shown in FIG. 1 is formed so as to be split between a fixed mold 11 and a movable mold 12, and although not particularly shown, a drive mechanism for opening and closing the mold, a cooling mechanism, etc. It has. With the mold 10 in a closed state, a cavity 13 serving as a space for injecting the resin of the molded product 1 is formed. A sprue 14 serving as a resin path to the cavity 13 is provided at a position where the injection nozzle 22 of the fixed mold 11 is connected. Further, a cold slag well 15 as a resin reservoir is provided immediately below the sprue 14, and a resin path is formed so that the resin injected from the injection nozzle 22 enters the cavity 13 through the gate 16. The mold 10 in FIG. 1 shows a closed state, in which resin is injected into the sprue 14, the cold slug well 15, the gate 16, and the cavity 13.

  An ejector pin 17 is provided at a position facing the cavity 13 of the movable mold 12. Further, an ejector pin 18 with a pressure sensor having a pressure detection function is provided at a position facing the cold slug well 15 immediately below the sprue 14. The resin pressure in the cold slug well 15 immediately below the sprue 14 can be measured by the ejector pin 18 with a pressure sensor. As the ejector pin 18 with a pressure sensor, for example, a trade name “EPSBQL series” commercially available from Futaba Electronics Co., Ltd. can be used.

  The temperature of the mold 10 is 100 ° C. or less for general-purpose plastics and general-purpose engineering plastics, and about 150 ° C. at most for super-engineering plastics. On the other hand, the cylinder 21 and the injection nozzle 22 of the molding machine 20 may be at a high temperature of 200 ° C. to 300 ° C. If a pressure sensor is to be provided at a position in contact with a cylinder or a nozzle, restrictions are large and costs are increased. On the other hand, if the temperature of the mold 10 is 150 ° C. or lower, the pressure sensor may be installed in a loose condition, and the cost of an apparatus such as a pressure sensor can be kept low.

  Moreover, as shown in FIG. 1, it is preferable to use the ejector pin 18 with a pressure sensor for the following reason. In general, an ejector pin for protrusion is provided at the position of the cold slug well 15 immediately below the sprue of the mold. When the ejector pin 18 with pressure sensor is used, when the pressure sensor is attached to the mold, it only needs to be replaced with a normal ejector pin, and there is no need to apply special processing to the mold in order to secure the installation location of the sensor. , Processing costs can be reduced. Moreover, it is not necessary to attach the ejector pin and the pressure sensor separately.

  In the present invention, the pressure detection means is not limited to using an ejector pin with a pressure sensor as long as the pressure in the cold slag well portion can be measured, and a simple pressure sensor having no ejector pin function is used. May be.

  The ejector pin 17 and the ejector pin 18 with a pressure sensor are formed in a shape that allows the molded product 1 to be added at the tip. Although not particularly illustrated, the mold 10 has a mechanism for projecting the ejector pin 17 and the ejector pin 18 with the pressure sensor when the mold is opened, and an ejector pin 17 and the ejector pin 18 with the pressure sensor that are projected before the mold is closed. A mechanism for retracting to a position is provided. The mold 10 is opened, and the molded product 1 and the cold slag well 15 are protruded from the tips of the ejector pins 17 and 18 so that the molded product 1 can be taken out of the mold 10.

  The ejector pin 18 with a pressure sensor is formed so as to measure the resin pressure of the cold slag well 15 and to output the data to the outside. The ejector pin 18 with pressure sensor is connected to the control device 30. The resin pressure output from the ejector pin 18 with the pressure sensor is input to the control device 30 to create a pressure profile including the relationship between pressure and time in each step of injection molding. The control device 30 is formed so as to be able to control the operations of the mold 10 and the molding machine 20. Specifically, the control device 30 manages the injection temperature, injection time, pressure holding time, cooling / plasticizing time, etc. of the resin, and operates an opening / closing mechanism (not shown), a movable mechanism of the ejector pin, a cooling device, and the like. Thus, it is possible to control resin injection, mold opening, mold removal, mold closing, and the like.

  FIG. 2 is a flowchart showing an injection molding method. Hereinafter, the injection molding method will be described. As shown in FIG.1 and FIG.2, first, resin is plasticized in the cylinder 21 of the injection apparatus 21 at a plasticization process (S110). Next, A: The mold 10 is closed in an injection step (S120), and the resin plasticized by the cylinder 21 of the molding machine 20 is injected into the formed cavity 13 from the tip of the injection nozzle 22. The injection time is set to a predetermined time according to the injection amount of the injection resin. The injected resin passes through the sprue 14, the cold slug well 15, and the gate 16 of the mold 10 and fills the cavity 13. Next, in the B: pressure holding step (S130), the pressure is kept constant for a predetermined time, and the resin is spread in the cavity 13. Next, in C: cooling / plasticizing step (S140), the molding die 10 is cooled by the cooling mechanism. After cooling the mold for a predetermined time to plasticize the resin, the cooling process is terminated. Next, in D: mold opening / projecting step (S150), the mold 10 is opened, the molded product 1 is ejected by the ejector pin 17 and the ejector pin 18 with a pressure sensor, and the molded product 1 is taken out from the mold 10. .

  Subsequently, the above steps A: injection step (S120), B: pressure holding step (S130), C: cooling / plasticizing step (S140), D: mold opening / projecting step (S150) are repeated as one shot. By performing the molding, the molded product 1 can be continuously molded. In the present invention, when the pressure in the C: cooling / plasticizing step is within a predetermined range, plasticization is normal, and the predetermined range is used such as when the pressure is too high or too low. If it is outside the range, an abnormality occurs in plasticization, and it can be determined that the molded product is defective. A specific method for determining whether or not plasticization is defective will be described below.

  FIG. 3 is a graph of a pressure profile showing a change in the resin pressure during molding. In the molding steps A to D, the pressure measured by the pressure sensor of the ejector pin 18 with the pressure sensor is output to the control device 30 connected to the pressure sensor and recorded. The control device 30 uses this pressure to create a pressure profile for the molding process for each shot. The pressure profile created in this way is the graph of pressure change shown in FIG. The pressure of the resin at the cold slag well position changes as shown by the profile curve shown in FIG.

  In the profile curve of FIG. 3, A: In the injection process, since the resin passes through the cold slag well and is filled in the cavity, a peak in which the pressure rapidly increases and decreases is observed. Next, in the B: pressure holding step, the pressure gradually increases to spread the resin in the cavity. And C: In the cooling / plasticizing step, a pressure increase peak P in which the pressure slightly rises only for a short time is observed after the pressure suddenly drops at the point where the holding pressure is finished. D: In the mold opening / projection process, when the molded product and the cold slug well are projected with the ejector pin, pressure is applied to the ejector pin and a peak appears for a moment.

  It has not been conventionally known that a pressure increase peak P appears in the above-mentioned C: cooling / plasticizing step. This pressure increase peak P could be detected for the first time by providing a pressure sensor at the position of the cold slug well immediately below the sprue. The appearance of this pressure rise peak P is assumed to be due to the following reason. As shown in FIG. 1, the resin of the sprue 14 and the cold slug well 15 is solidified to form a solidified body. The solidified body is linearly integrated at the nozzle tip of the molding machine. When plasticizing and metering is performed by the molding machine 20, the molten resin is stored while applying back pressure in front of the nozzle. The molten resin of the molding machine presses the solidified resin of the sprue and cold slag well through the nozzle. It is considered that the pressure applied to the solidified body is transmitted directly under the sprue and appears as a pressure increase peak P.

  The reason why the pressure increase peak of the same type as the pressure increase peak P does not appear except under the sprue is considered to be as follows. The pressure applied to the solidified body by being pressed through the nozzle by the molten resin of the molding machine is only a slight pressure. When this pressure is transmitted to the molded product 1 through the sprue 14 and the cold slug well 15, pressure loss occurs at the runner and the gate, so that the pressure cannot be detected at the site of the molded product 1. Therefore, it is considered that the pressure at the time of plasticization transmitted through the nozzle can be detected only directly under the sprue which is transmitted linearly and causes minimal pressure loss.

  FIGS. 4A to 4C are graphs showing the relationship between the pressure sensors of Examples and Comparative Examples and the resin pressure, where (a) is the standard time and (b) is the plastic time. (C) shows the case where the plasticizing time is extended. 4A to 4C, the solid line is the pressure profile of Example 1, the dotted line is the pressure profile of Comparative Example 1, and the alternate long and short dash line is the pressure profile of Comparative Example 2.

  Example 1 is a pressure profile at the position of the cold slug well immediately below the sprue of the mold. Comparative Example 1 is a pressure profile at a position other than the cold slug well. Comparative Example 2 is a pressure profile at a position different from that of Comparative Example 1 and at a position other than the cold slug well. As shown in the graphs of FIGS. 4A to 4C, the pressure profile curves differ depending on the position where the pressure sensor for measuring the pressure of the molding resin in the mold is installed. 4A to 4C, in each case, C: pressure increase peaks P1, P2, and P3 in the cooling and plasticizing process are observed in the pressure profile curve of Example 1, but Comparative Example 1 and Comparative Example In the pressure profile curve of Example 2, there is no pressure increase peak in the cooling / plasticizing process.

  In Example 1, when the plasticizing time is shortened as shown in FIG. 4B, the waveform of the pressure rise peak P2 becomes sharp. Moreover, as shown in FIG.4 (c), when the plasticization time of Example 1 is lengthened, the pressure rise peak P3 has a broad waveform. Thus, in Example 1, the shape of the pressure increase peak P changes following the plasticization time. This change in the pressure rise peak P confirms that it is related to the plasticization of the resin. On the other hand, in Comparative Examples 1 and 2, no pressure increase peak is observed even if the plasticizing time is increased or decreased. A pressure increase peak cannot be detected except where the pressure sensor is provided at a portion of the cold slag well 15 immediately below the sprue 14.

  The waveform of the pressure rise peak P in the cooling / plasticizing process is different between the case of poor plasticization and the case of normal plasticization. By using the pressure rise peak P, it is possible to determine whether the plasticization of the molded product is normal or defective. Then, molded articles having poor plasticization can be excluded. In addition, as described below, a pressure profile curve of a normal molded product is created in advance as a master curve, and the quality profile of the plastic product is determined by comparing and comparing the pressure profile curve of the molded product with the master curve. You can also

  FIG. 5 is a flowchart showing a method of detecting a plasticization failure according to the present invention. In the detection of plasticization failure in the injection molding, as shown in FIG. 5, when one shot is completed after performing the injection molding (S100), the control device 30 detects from the pressure sensor installed immediately below the sprue of the mold 10. A pressure profile is created using the output pressure data (S200). A pressure profile curve at the time of injection molding of a normal molded product is recorded in advance in a storage device or the like of the control device 30 as a master curve. This master curve has a pressure rise peak P in the cooling / plasticizing process, like the pressure profile curve shown in FIG. Next, the control device 30 compares the pressure profile curve created in S200 with the previously input master curve, and performs a process of determining the similarity between the two pressure profile curves (S210). In the process of S210, if the pressure profile curve is similar to the master curve (YES), it is determined that plasticization is normal. On the other hand, when the pressure profile is different from the master curve in the process of S210 (NO), it is determined that plasticization is defective. In this way, it is possible to determine the presence or absence of plasticization failure of the molded product.

  From the molded product manufactured by injection molding, the molded product with poor plasticization detected by the above-described discrimination method is removed. Since this plasticization failure can be determined mechanically, in the injection molding method, a defective product due to plasticization failure can be automatically excluded without manually performing visual inspection or the like. It is possible to obtain only molded products that are not defective.

  In addition, when detecting plasticization failure of a molded product in the cooling / plasticizing process, instead of the similar determination process (S210) between the pressure profile and the master curve, the pressure measured by the pressure sensor is a predetermined value. Even if it is judged whether it is within the numerical range, and if it is within the numerical range, the plasticization of the molded product is good, and if it is out of the numerical range, the plasticization is bad It may be judged whether or not. As the numerical value range of the pressure, a predetermined pressure range such as a pressure upper limit value and a lower limit value of a peak of pressure increase can be set in advance from manufacturing data of normal molded products and defective molded products.

It is a schematic block diagram which shows an example of the metal mold | die for injection molding of this invention. It is a flowchart of an injection molding method. It is a graph which shows the change of the resin pressure at the time of shaping | molding. It is a graph which shows the relationship between the position of a pressure sensor, and resin pressure, (a) when plasticization time is standard time, (b) when plasticization time was shortened, (c) extended plasticization time. Is the case. It is a flowchart which shows the detection method of the plasticization defect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molded product 10 Injection mold 11 Fixed side mold 12 Movable side mold 13 Cavity 14 Spru 15 Cold slug well 18 Ejector pin 20 with pressure sensor Molding machine 21 Cylinder 22 Injection nozzle 30 Controller P Pressure rise peak

Claims (6)

  An injection mold, characterized in that the mold is provided with pressure detection means for measuring the resin pressure of the cold slug well immediately below the sprue.   2. The injection mold according to claim 1, wherein the pressure detecting means is an ejector pin having a pressure detecting function.   Using a mold provided with pressure detection means for measuring the resin pressure of the cold slag well just below the sprue, the pressure of the resin in the mold measured by the pressure detection means in the plasticizing process at the time of injection molding is A method for detecting poor plasticization in injection molding, characterized in that a molded product is determined to be poorly plasticized when outside a predetermined range. An injection process in which plasticized resin is injected into the mold cavity from the injection nozzle, a pressure holding process in which the resin in the cavity is held at a predetermined pressure, and the mold is cooled until the resin in the cavity reaches a predetermined temperature. At the same time, in the injection molding method of sequentially performing the cooling / plasticizing step of plasticizing the resin by the plasticizing device, and the taking-out step of taking out the molded product after completion of the cooling,
Using a mold provided with pressure detection means for measuring the resin pressure of the cold slug well immediately below the sprue, the pressure of the resin in the mold measured by the pressure detection means in the cooling / plasticizing process is predetermined. An injection molding method characterized in that if it falls outside the range, it is determined that the molded product is poorly plasticized, and the molded product that is poorly plasticized is removed.   A pressure profile curve is created from the pressure of the resin in the mold in the cooling / plasticizing process, and a plasticization failure is distinguished from the pressure profile curve in the cooling / plasticizing process of normal injection molding. The injection molding method according to claim 4.   6. The injection molding method according to claim 4, wherein the molding is performed at a mold temperature of 150 ° C. or lower.

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