Injection device, injection molding machine, and method for calibrating injection device

Abstract

To reduce molding defects in a molded product.SOLUTION: An injection device includes: a cylinder 202; a screw 23 arranged in the cylinder 202; a rotation mechanism 205 for rotating the screw 23; a fastening part 203CN for spline-connecting the screw 23 and the rotation mechanism 205; a detection member 301 fixed to the fastening part 203CN; and a sensor 302 for detecting a position of the detection member 301.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an injection unit, an injection molding machine, and a method for calibrating an injection unit. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2016-185607 (Patent Document 1) describes a technique related to an injection device that constitutes an injection molding machine.

[0003] Japanese Patent Laid-Open Publication No. 06-246803 (Patent Document 2) describes a technique for forming a light-transmitting optical resin molded article by injection molding.

[0004] Japanese Patent Application Laid-Open No. 2017-71085 (Patent Document 3) describes a technique related to a connection structure between a screw and a screw drive device of an injection molding machine. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-185607 [Patent Document 2] Japanese Patent Application Publication No. 06-246803 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-71085 Summary of the Invention [Problem to be solved by the invention]

[0006] An injection molding machine is a device that manufactures molded products by kneading and melting raw materials and then injecting them into a mold. An injection molding machine is a device that can handle a series of injection molding processes, including melting the raw materials, injecting them into a mold, cooling, and ejection.

[0007] An injection molding machine is composed of a clamping device to which a mold is attached and an injection device that injects molten raw material from a nozzle. A molded product is formed by injecting raw material from the injection device into a cavity formed when a fixed mold and a movable mold attached to the clamping device are closed. The molded product is then removed by ejecting an ejector pin while the fixed mold and movable mold are open. When injection molding is performed, defects such as discoloration or gelation may occur in some parts of the molded product under certain conditions. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] In one embodiment, the injection device includes a cylinder, a screw disposed within the cylinder, a rotation mechanism for rotating the screw, a fastening portion for spline-connecting the screw and the rotation mechanism, a detection member fixed to the fastening portion, and a sensor for detecting the position of the detection member.

[0009] An injection molding machine in one embodiment includes an injection device that melts and injects an injection material and a mold clamping device that clamps a mold into which the injection material has been injected. Here, the injection device has a cylinder, a screw disposed in the cylinder, a rotation mechanism for rotating the screw, a fastening part for spline-connecting the screw and the rotation mechanism, a detection member fixed to the fastening part, and a sensor for detecting the position of the detection member.

[0010] In one embodiment, a calibration method for an injection device is a calibration method for an injection device having a cylinder, a screw arranged in the cylinder, a rotation mechanism for rotating the screw, a fastening part for spline-connecting the screw and the rotation mechanism, a detection member fixed to the fastening part, and a sensor for detecting the position of the detection member.

[0011] The method for calibrating the injection device includes: (a) inserting a fastening portion into the rotation mechanism; (b) detecting the position of the detection member with a sensor after step (a); and (c) rotating the screw with the rotation mechanism after step (b) so that the position of the detection member is at a predetermined position. [Effects of the Invention]

[0012] According to one embodiment, defects in molded products can be reduced. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of an injection molding machine. [Figure 2] FIG. 2 is a diagram illustrating a configuration of an injection device. [Figure 3] 3 is a diagram showing a cross section of the fastening portion taken along line AA in FIG. 2, schematically illustrating a plurality of protrusions provided on the fastening portion. [Figure 4] 3 is a diagram showing a cross section of the fastening portion taken along line AA in FIG. 2, schematically illustrating a plurality of protrusions provided on the fastening portion. [Figure 5] 1 is a diagram showing a main configuration of an injection device according to an embodiment. FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. [Figure 7] 10 is a flowchart illustrating a method for calibrating the injection device. DETAILED DESCRIPTION OF THE INVENTION

[0014] In all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations thereof will be omitted. In addition, hatching may be used even in plan views to make the drawings easier to understand.

[0015] The technical idea of ​​this embodiment can be widely applied to injection molding machines equipped with an injection unit and a mold clamping unit. In this regard, the technical idea of ​​this embodiment will be explained below using an injection molding machine in which one injection unit is provided for one mold clamping unit as an example, but the technical idea of ​​this embodiment is not limited to this and can be widely applied to, for example, a "multi-injection molding machine" in which multiple injection units are provided for one mold clamping unit.

[0016] <Configuration of injection molding machine> 1 is a schematic diagram showing the configuration of an injection molding machine 100. The injection molding machine 100 is made up of a mold clamping unit 1 and an injection unit 2.

[0017] The mold clamping unit 1 is a device that performs mold clamping operations. A mold into which raw material injected from the injection unit 2 is poured is attached to the mold clamping unit 1. The mold clamping unit 1 is a device that manufactures molded products by injecting raw material into a cavity CAV that is formed by performing a mold clamping operation on the mold. On the other hand, the injection unit 2 is a device that performs injection operations. The injection unit 2 is a device that kneads and melts the raw material and injects it into the mold attached to the mold clamping unit 1.

[0018] <Configuration of the mold clamping unit> The mold clamping device 1 has a movable platen 11 and a fixed stationary platen 10. The mold clamping device 1 is configured to be able to variably control the distance between the movable platen 11 and the stationary platen 10. A movable mold 13 and a stationary mold 12 are arranged between the movable platen 11 and the stationary platen 10. This allows the mold clamping device 1 to, for example, "close the mold" ("close the mold" includes "clamping") by shortening the distance between the movable platen 11 and the stationary platen 10 by variably controlling the distance between the movable platen 11 and the stationary platen 10. The mold clamping device 1 can also "open the mold" by increasing the distance between the movable mold 13 and the stationary mold 12.

[0019] At this time, when the movable mold 13 and the fixed mold 12 are "closed," a cavity CAV is formed between the movable mold 13 and the fixed mold 12. A molded product is formed by injecting raw material into the cavity CAV. In the injection molding machine 100 shown in FIG. 1, when the movable mold 13 and the fixed mold 12 are "closed," one cavity CAV is formed, and a molded product is formed by injecting raw material into the cavity CAV.

[0020] <Configuration of injection unit> Fig. 2 shows the injection device 2 of Fig. 1. The injection device 2 will be described using Figs. 1 and 2. The injection device 2 has a cylinder 22 and a hopper 21 for feeding raw material into the cylinder. When the raw material is fed into the hopper 21, the raw material is kneaded by a rotatable screw 23 disposed inside the cylinder 22. The screw 23 is driven by a drive unit 24.

[0021] A heater 25 is arranged around the cylinder 22, and raw materials fed into the interior of the cylinder 22 are heated by the heater 25 and kneaded by the screw 23 to form a molten material. A nozzle 26 is provided at the tip of the cylinder 22. The molten material is extruded by the screw 23 driven by a drive unit 24 and injected from the nozzle 26.

[0022] The housing 204, the rotation mechanism 205, and the screw driving unit 206 shown in FIG. 2 are one example of the configuration of the driving unit 24 shown in FIG.

[0023] The screw 23 is provided with a plurality of screw flights 23F. A fastening portion 203CN is provided at the end of the screw 23. The screw 23 and the rotation mechanism 205 are spline-connected via the fastening portion 203CN. Here, "spline connection" refers to a connection method in which a plurality of convex portions 210A to 210F (see FIGS. 3 and 4) provided on the fastening portion 203CN are inserted into a plurality of grooves GR provided in the rotation mechanism 205. The rotation mechanism 205 is a mechanism for rotating the screw 23.

[0024] The screw driving unit 206 is configured to be able to rotate and move the screw 23 back and forth. For example, the screw driving unit 206 includes a rotation motor for rotating the screw 23 and an injection motor for moving the screw 23 back and forth.

[0025] The raw material fed into the cylinder 22 is kneaded by the screw 23 to become a molten material. The molten material is extruded by moving the screw 23 forward, and is then injected from the nozzle 26. Here, "forward" means moving the screw 23 in the positive direction of the X axis, and "rearward" means moving the screw 23 in the negative direction of the X axis.

[0026] <Operation of injection molding machine> 1, the movable platen 11 of the mold clamping unit 1 is moved, whereby the movable mold 13 is brought into contact with the fixed mold 12, thereby "mold closing."

[0027] Thereafter, when the screw 23 is driven by the drive unit 24, a predetermined amount of molten material accumulated between the nozzle 26 and the screw 23 in a measuring step, which will be described later, is injected from the tip of the nozzle 26 into the cavity CAV between the "closed" movable mold 13 and fixed mold 12. In other words, the measured molten material is injected from the nozzle 26 into the cavity CAV (injection step).

[0028] Subsequently, after injection is complete, pressure is applied to the material in the cavity CAV through the molten material remaining in the cylinder 22 to compensate for the shrinkage of the raw material that occurs as the molten material cools. In other words, after the molten material is injected, the state in which pressure is applied to the cavity CAV by the screw 23 is maintained (holding pressure process). After the holding pressure process is complete, the molten material is cooled by the movable mold 13 and fixed mold 12, which are controlled to a temperature below the solidification temperature of the molten material (cooling process). Specifically, the molten material filled in the cavity CAV is cooled by the movable mold 13 and fixed mold 12 to a temperature below the solidification temperature.

[0029] 1, solid raw material is fed from a hopper 21 into a cylinder 22. Then, in parallel with the cooling process on the mold clamping device 1 side, a screw 23 is driven to rotate by a drive unit 24 and is simultaneously moved backward by a predetermined amount.

[0030] During this time, the raw material supplied from the hopper 21 is melted in the cylinder 22 of the injection device 2 by the rotational drive of the screw 23 and advances forward (in the positive direction of the X-axis). That is, the raw material supplied from the hopper 21 is heated and melted by the heat from the heater 25 and the shear heat of the material generated by the rotation of the screw 23, and advances forward as a molten material. As a result, a predetermined amount of molten material accumulates in the cylinder 22 between the nozzle 26 and the screw 23 (measurement process).

[0031] Thereafter, when the metering process and the cooling process are completed, the mold clamping unit 1 is operated to "open" the space between the movable mold 13 and the fixed mold 12. After "opening" the space between the movable mold 13 and the fixed mold 12 in this way, the molded product is ejected by an ejector pin of the ejector unit provided in the mold clamping unit 1. This allows the molded product to be removed from the mold clamping unit 1. This molded product becomes the product molded by the injection molding machine 100.

[0032] By repeating this series of operations, molded articles of the same shape can be continuously manufactured. By repeatedly operating the injection molding machine 100 in the above manner, molded articles can be mass-produced.

[0033] <Consideration> For example, when a screw is used continuously, carbides from the raw material may adhere to a portion of the screw. This may result in defects such as discoloration or gelation in a portion of the molded product. In particular, when discoloration or gelation occurs in a translucent molded product such as a lens or a light guide plate, the translucent properties such as haze, transmittance, and refractive index deteriorate. Furthermore, discoloration not only in translucent molded products but also in white molded products can cause abnormal appearances such as darkening. For this reason, in order to remove the carbides from the raw material that have adhered to the screw, the screw is removed from the rotation mechanism to which it is spline-connected, and maintenance work such as cleaning the screw is performed.

[0034] However, after the maintenance work, when the screw is splined back into the rotation mechanism and the injection molding operation is resumed, the above defects may occur in some parts of the molded product despite the maintenance work having been performed. These defects are often caused by shear heating that occurs during the process in which the raw material is mixed from solid pellets by the screw and melted. Therefore, these defects are thought to be related to the thermal history of the raw material before the pellets are melted.

[0035] When pellets are fed from the hopper 21 into the cylinder 22, they are kneaded and melted by the rotating screw flight 23F. At this time, if the flight position (hereinafter referred to as the "initial flight position"), which is the position of the screw flight 23F when the screw 23 starts to rotate, is different, the "meshing conditions" when the pellets start to be kneaded will be different. Different "meshing conditions" mean that the thermal history applied to the raw material before the pellets melt will be different. In other words, the thermal history applied to the raw material will be different depending on the initial flight position. In other words, it is thought that there are initial flight positions that are less likely to cause defects in the molded product and initial flight positions that are more likely to cause defects.

[0036] 3 and 4 are cross-sectional views taken along line AA in Fig. 2. The fastening portion 203CN is provided with protrusions 210A-210F. The protrusions 210A-210F are spline-connected by being fitted into a plurality of grooves GR provided in the rotation mechanism 205. The fastening mode between the protrusions 210A-210F and the plurality of grooves GR of the rotation mechanism 205 differs depending on the positions of the protrusions 210A-210F as shown in Figs. 3 and 4, and therefore the initial flight position of the screw 23 also differs.

[0037] If the initial flight position of the screw 23 is different, the "biting conditions" when the pellets start to be kneaded will be different. As a result, the heat history applied to the raw materials until the pellets melt will be different. In other words, depending on the initial flight position after maintenance work on the screw 23, defects may be more likely to occur. <Embodiment> As shown in FIG. 5, a detection member 301 is provided in the fastening portion 203CN. Here, the detection member 301 is positioned based on an initial flight position that has been confirmed in advance to prevent any defects. A sensor 302 capable of detecting the detection member 301 is provided inside the housing 204. As shown in FIG. 6, the detection member 301 is disposed so as to face the sensor 302 by rotation of the fastening portion 203CN. As an example, when the detection member 301 is positioned facing the sensor 302, the sensor 302 detects the detection member 301. However, the position of the detection member 301 is not limited to this, and it may be any position that allows detection by the sensor 302. Furthermore, the following examples are given as combinations of the sensor 302 and the detection member 301.

[0038] (1) Photoelectric sensors (electromagnetic waves and ultrasonic waves) and reflective (reactive) detection materials, (2) infrared sensors and heater-equipped temperature-responsive detection materials, (3) mutual induction sensors and induction-responsive detection materials, and (4) laser sensors and reflective (reactive) detection materials.

[0039] The control unit 303 is configured to control the sensor 302 and the screw driving unit 206. The control unit 303 performs calibration of the screw 23 based on the output signal from the sensor 302. Calibration is a process of setting initial conditions including an initial flight position before the injection unit 2 starts operating.

[0040] FIG. 7 is a flowchart showing the calibration and injection operation of the injection unit after the maintenance work. First, the screw 23 removed for maintenance work is connected to the rotation mechanism 205 (S101). Specifically, the fastening portion 203CN at the end of the screw 23 is inserted into the rotation mechanism 205, which is provided with a plurality of groove portions GR, thereby spline-connecting the screw 23 and the rotation mechanism 205.

[0041] Next, the sensor 302 performs a detection operation for the detection member 301. When the control unit 303 receives an output signal from the sensor 302 and determines that the sensor 302 has not detected the detection member 301 (S102), the control unit 303 controls the screw driving unit 206 to rotate the screw 23 via the fastening unit 203CN (S103). When the rotation of the fastening unit 203CN brings the detection member 301 to a position facing the sensor 302 (see FIG. 6), the detection member 301 is detected by the sensor 302 (S102).

[0042] When the control unit 303 determines that the sensor 302 has detected the detection member 301, the rotation of the screw 23 stops, and the calibration ends (S104).

[0043] Thereafter, pellets are charged into the hopper 201, the screw 23 is rotated, and the operation of plasticizing the pellets is started (S105). When the operation of plasticizing the pellets is completed (S106), the injection operation is carried out (S107). In this embodiment, even after maintenance work, it is possible to always assume the initial flight position that has been confirmed in advance to prevent defects. Therefore, in the process in which the pellets are sent to the tip of the screw 23 while changing state from the pellet bite position (solid) at the start of plasticization → semi-molten → completely melted, the pellets are plasticized under almost the same conditions as they pass through the screw flight 23F, and the plasticization of the pellets is stabilized, thereby increasing the reproducibility of molded products that do not cause defects such as discoloration or gelation. The present invention has been specifically described above based on the embodiments thereof. However, the present invention is not limited to the above embodiments and can be modified in various ways without departing from the spirit and scope of the present invention. For example, while the present application has disclosed a problem with a translucent molded product or a white molded product, the problem is not limited to these molded products, and the technology disclosed in the present application can also be used to manufacture opaque molded products or black molded products. Furthermore, although the present embodiment has shown an example in which only one detecting member 301 and one sensor 302 are used, multiple detecting members 301 and one sensor 302 may be used. [Explanation of symbols]

[0044] 1 Mold clamping device 2 Injection device 10 Fixed plate 11 Movable plate 12 Fixed mold 13 Movable mold 21 Hopper 22 cylinders 23 screw 23F Screw Flight 24 Drive unit 25 Heater 26 nozzles 100 injection molding machine 203CN Fastening part 204 Housing 205 Rotation Mechanism 206 Screw drive unit 210A convex part 210B convex part 210C convex part 210D convex part 210E convex part 210F convex part 301 Detection member 302 Sensors 303 Control Unit CAV Confined space GR groove

Claims

1. An injection unit including: Cylinder; a screw disposed within the cylinder; a rotation mechanism for rotating the screw; a fastening portion for spline-connecting the screw and the rotation mechanism; a detection member fixed to the fastening portion; and A sensor for detecting the position of the detection member.

2. 2. The injection device according to claim 1, The screw includes flights that mix the raw materials.

3. 3. The injection device according to claim 2, The raw material is a translucent material or a white raw material.

4. Injection molding machines, including: an injection device for melting and injecting the injection material; and a mold clamping device that clamps the mold into which the injection material has been injected; Here, the injection device is A cylinder; a screw disposed within the cylinder; a rotation mechanism for rotating the screw; a fastening portion for spline-connecting the screw and the rotation mechanism; a detection member fixed to the fastening portion; and a sensor for detecting the position of the detection member; It has.

5. 5. The injection molding machine according to claim 4, The screw includes flights that mix the raw materials.

6. 6. The injection molding machine according to claim 5, The raw material is a translucent raw material or a white raw material.

7. A cylinder; a screw disposed within the cylinder; a rotation mechanism for rotating the screw; a fastening portion for spline-connecting the screw and the rotation mechanism; a detection member fixed to the fastening portion; and a sensor for detecting the position of the detection member; A method for calibrating an injection device, comprising: (a) inserting the fastener into the rotation mechanism; (b) after step (a), detecting the position of the detection member with the sensor; and (c) after the step (b), rotating the screw by the rotation mechanism so that the position of the detection member is at a predetermined position; A method for calibrating an injection device, comprising:

8. 8. The method for calibrating an injection unit according to claim 7, The screw includes a flight for kneading raw materials, Even if the screw is removed from the rotation mechanism and then reinserted into the rotation mechanism, the flight position of the screw at the start of operation after the screw is reinserted into the rotation mechanism is the same as the flight position of the screw at the start of operation before the screw was removed from the rotation mechanism.

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