Injection molding machine and injection molding method

Abstract

To provide a screw-in plunger type injection molding machine that adjusts a flow rate and a pressure of a resin while metering a resin material.SOLUTION: An injection molding machine includes: a cylindrical barrel having a heater on its outer periphery and storing a molten resin inside; a cylindrical plunger including a heater on its outer periphery and a screw that moves back and forth inside the barrel to send the molten resin to the barrel, melting the resin material inside and injecting the molten resin stored inside the barrel by moving back and forth inside the barrel; a mechanism for controllably moving the plunger forward and backward relative to the barrel; and a mechanism for controllably moving the screw forward and backward relative to the plunger.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an injection molding machine and an injection molding method. [Background technology]

[0002] In order to plasticize and inject the molten resin at an appropriate pressure, the pressure inside the plunger is monitored. The electric injection device of Patent Document 1 uses an electric motor 54 as a drive source to move the plunger back and forth, and while supplying the resin material into the injection chamber, the plunger moves back while applying back pressure to the resin material with the plunger, thereby filling and measuring the injection material into the injection chamber. A pressure sensor is provided at the tip of the plunger in a state in which it moves back together with the plunger, and a controller applies a drive torque in the backward direction of the plunger by the electric motor so that the pressure detected by the pressure sensor becomes the set appropriate back pressure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-131898 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the injection molding machine in the above document is not a screw-in plunger type injection molding machine. Also, the injection molding machine in the above document is not a device that adjusts pressure during metering. Therefore, an object of the present disclosure is to provide a screw-in plunger type injection molding machine that adjusts the flow rate and pressure of resin during metering of resin material. [Means for solving the problem]

[0005] The injection molding machine of the present disclosure comprises: A cylindrical barrel having a heater on its outer periphery and storing molten resin inside; a cylindrical plunger that includes a heater on an outer periphery and a screw that moves back and forth inside the barrel to send the molten resin to the barrel, melts a resin material inside the plunger, and moves back and forth inside the barrel to inject the molten resin stored inside the barrel; a mechanism for controllably advancing the plunger relative to the barrel; and a mechanism for controllably advancing the screw back and forth relative to the plunger.

[0006] The above configuration provides a screw-in plunger type injection molding machine that adjusts the flow rate and pressure of the resin while metering the resin material.

[0007] The injection molding machine of the present disclosure comprises: The mechanism for controllably moving the screw back and forth relative to the plunger is a motor.

[0008] With the above configuration, it is possible to control the mechanism that advances and retreats the screw relative to the plunger.

[0009] The injection molding machine of the present disclosure comprises: The mechanism for controllably moving the screw back and forth relative to the plunger is characterized in that it is a hydraulic cylinder equipped with a brake mechanism.

[0010] With the above configuration, it is possible to control the mechanism that advances and retreats the screw relative to the plunger.

[0011] The injection molding machine of the present disclosure comprises: The mechanism for controllably moving the screw forward and backward relative to the plunger is a variable screw length cylinder.

[0012] With the above configuration, it is possible to control the mechanism that advances and retreats the screw relative to the plunger.

[0013] The injection molding method of the present disclosure comprises: A cylindrical barrel having a heater on its outer periphery and storing molten resin inside; a cylindrical plunger that includes a heater on an outer periphery and a screw that moves back and forth inside the barrel to send the molten resin to the barrel, melts a resin material inside the plunger, and moves back and forth inside the barrel to inject the molten resin stored inside the barrel; a mechanism for controllably advancing the plunger relative to the barrel; A method for injection molding a resin material using an injection molding machine comprising: This is an injection molding method in which the flow rate and pressure of the molten resin passing through the tip of the screw are adjusted by the opening of a screw check while the resin material is being metered.

[0014] The above configuration provides a method for adjusting the flow rate and pressure of resin during metering of resin material in a screw-in plunger type injection molding machine. Effect of the Invention

[0015] The present disclosure provides a screw-in plunger type injection molding machine that adjusts the flow rate and pressure of resin during metering of resin material. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram of an injection molding apparatus according to an embodiment, and a schematic diagram showing the opening degree of a screw check. FIG. [Diagram 2] 1A to 1C are schematic diagrams of three types of screw check mechanisms according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the invention according to the claims is not limited to the following embodiment. Furthermore, not all of the configurations described in the embodiment are necessarily essential as means for solving the problem. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and repeated explanations are omitted as necessary.

[0018] (Description of Injection Molding Apparatus According to an Embodiment) Fig. 1 is a schematic diagram of an injection molding apparatus according to an embodiment and a schematic diagram showing the opening degree of a screw check. Fig. 2 is a schematic diagram of three types of screw check mechanisms according to an embodiment. The injection molding apparatus according to an embodiment will be described with reference to Figs. 1 and 2. The injection molding apparatus according to an embodiment is an injection molding apparatus that injects molten resin and pours it into a mold.

[0019] As shown in FIG. 1, an injection molding machine 100 includes a barrel 101, a plunger 104, a screw 106, a hopper 108, a screw check mechanism 110, and a motor 111 for rotating the screw.

[0020] The barrel 101 has a cylindrical shape. A heater 102 is provided on the outer periphery of the cylindrical shape of the barrel 101. Molten resin 103 is stored inside the cylindrical shape of the barrel 101. The molten resin 103 is kept in a molten state by heating from the heater 102. A plunger 104 having an outer diameter that matches the inner periphery of the cylindrical shape of the barrel 101 is disposed inside the barrel 101. The molten resin 103 stored inside the barrel 101 is injected to the outside by the plunger 104 moving back and forth relative to the barrel 101. For this purpose, a mechanism 109 is provided that controllably moves the plunger back and forth relative to the barrel. Controllable means that not only the forward and backward movement can be controlled but also that it can be stopped and held. The mechanism 109 that moves the plunger back and forth relative to the barrel uses, for example, a motor mechanism.

[0021] The plunger 104 has a cylindrical shape. A heater 105 is provided on the outer periphery of the cylindrical shape of the plunger 104. Inside the plunger 104, there are resin material 107 supplied from a hopper 108 and molten resin 103 obtained by melting the resin material 107. As the resin material 107 travels from the supply source in the hopper 108 to the tip of the plunger 104, it is heated and melted by the heater 105 to become the molten resin 103. Inside the plunger 104, there is a screw 106 that rotates to apply a shear force to the resin material 107 while moving it forward to melt it.

[0022] The screw 106 is rotated by a screw-rotating motor 111 and a pulley or a reducer.

[0023] The purpose of controlling the molten resin pressure in the barrel during the metering operation is to indirectly control the pressure of the molten resin flowing around the screw in the plunger, thereby appropriately controlling the shear heat generated in the molten resin by the rotation of the screw.

[0024] The molten resin pressure in the barrel may be changed for purposes other than controlling the plasticization back pressure, such as degassing or adding fibrous materials. However, if the molten resin pressure is changed during the metering operation, the plasticization back pressure will be affected, so the molten resin pressure cannot be changed. Therefore, if the molten resin pressure in the barrel is changed for purposes other than controlling the plasticization back pressure, it is necessary to perform the operation other than during the metering operation, which leads to an increase in cycle time and a decrease in productivity.

[0025] Due to its structure, a small amount of resin leaks from the sliding part of the plunger, but the amount of leakage is proportional to the molten resin pressure inside the barrel and the time. During the metering operation, increasing the molten resin pressure inside the barrel to increase the molten resin pressure inside the plunger increases the amount of resin leaking from the barrel and the sliding part of the plunger.

[0026] Therefore, the screw-in plunger type injection molding machine of the present disclosure is provided with a screw check mechanism 110, which is a mechanism for controllably moving the screw forward and backward relative to the plunger.

[0027] 1, the screw check mechanism 110 can control the screw relative to the tip of the plunger to be fully closed, intermediate, or fully open. That is, the screw check mechanism 110 can control the advancement, retreat, and stoppage of the plunger 104.

[0028] By fully closing the screw check mechanism 110, the flow rate can be zero and the resin pressure can be maximized. By fully opening the screw check mechanism 110, the flow rate can be maximized and the resin pressure can be minimized. By taking an intermediate position between fully closing and fully opening, the opening of the screw check can be adjusted during the metering operation, and the flow rate and resin pressure of the resin passing through the tip of the screw can be feedback controlled. Also provided is an injection molding method in which the opening of the screw check is used to adjust the flow rate and pressure of the molten resin passing through the tip of the screw while the resin material is being metered.

[0029] 2(a), the screw check mechanism 110 can use a motor 201 that moves the screw forward and backward relative to the plunger 104. The screw check mechanism 110 can be realized using the motor 201 that moves the screw forward and backward, a ball screw, or an actuator similar thereto.

[0030] As shown in FIG. 2(b), the screw check mechanism 110 can use a hydraulic cylinder 202 with a brake mechanism.

[0031] As shown in FIG. 2( c ), the screw check mechanism 110 can use a screw length variable cylinder 203 .

[0032] During the metering operation, the resin material 107 fed from the hopper 108 into the plunger 104 is gradually melted and sent forward by the screw 106. During this time, the resin material 107 is heated by heat transfer from the heater 105 installed inside or on the outer periphery of the plunger, as well as by shear heat generated by friction between the rotating screw 106 and the resin material 107, and is melted.

[0033] For example, if the screw rotation speed is increased to speed up the feed speed in order to shorten the time of the metering operation, the amount of heat received by the resin material 107 may be insufficient, resulting in a defect called non-melting. As a means to prevent this, there is a method of increasing the molten resin pressure in the plunger 104 in order to increase the amount of shear heat generated by the screw 106 and the resin material 107.

[0034] There is a correlation between the pressure, viscosity, and shear heat generation of the molten resin, and increasing the molten resin pressure increases the molten resin viscosity as well as the shear heat generation of the screw and the resin material. Therefore, measures to intentionally increase the molten resin pressure are often used to prevent unmelted resin.

[0035] On the other hand, the feed rate of the molten resin, which is mainly given by the screw rotation, decreases in exchange for the amount of energy converted to heat energy by shearing, according to the law of conservation of energy. Therefore, excessive pressure not only increases the metering time, but also causes new quality defects such as decomposition of the resin due to excessive heat input to the molten resin.

[0036] By appropriately controlling the molten resin pressure inside the plunger 104, it is possible to achieve both melt quality and molding cycle.

[0037] (Description of Pressure Control According to the Embodiment) During the metering operation, the molten resin 103 in the plunger 104 passes through a hole provided at the tip of the plunger 104, which becomes the screw check mechanism 110, and is stored inside the barrel 101. At this time, the flow path width of the screw check is smaller than the others, and pressure loss occurs during the passage.

[0038] If the molten resin pressure in barrel 101 is P1, the molten resin pressure in plunger 104 is P2, and the pressure loss in the screw check section is P3, the following relationship must hold for molten resin 103 in plunger 104 to flow into barrel 101. P1+P3 <P2

[0039] In the related screw-in plunger type injection molding machine, P3 is constant, so P2 is controlled by controlling P1.

[0040] With the technology disclosed herein, P2 can be controlled by controlling P3. According to the Darcy-Weisbach equation, the pressure loss in the piping is inversely correlated with the cross-sectional area of ​​the flow path, so P3 increases by narrowing the opening of the screw check and narrowing the flow path through which the molten resin 103 can pass. Also, P3 decreases by widening the opening of the screw check and widening the flow path through which the molten resin 103 can pass.

[0041] Therefore, by controlling P3, the value of P2 can be freely changed even during a weighing operation.

[0042] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0043] 100 injection molding machine, 101 barrel, 102 heater, 103 molten resin, 104 plunger, 105 heater, 106 screw, 107 resin material, 108 hopper, 109 mechanism for moving the plunger back and forth relative to the barrel, 110 screw check mechanism, 111 screw rotation motor, 201 motor for moving the screw back and forth, 202 hydraulic cylinder with brake mechanism, 203 screw length variable cylinder

Claims

1. A cylindrical barrel having a heater on its outer periphery and storing molten resin therein; a cylindrical plunger that includes a heater on an outer periphery and a screw that moves back and forth inside the barrel to send the molten resin to the barrel, melts a resin material inside the plunger, and moves back and forth inside the barrel to inject the molten resin stored inside the barrel; a mechanism for controllably advancing the plunger relative to the barrel; and a mechanism for controllably advancing the screw back and forth relative to the plunger.

2. 2. The injection molding machine according to claim 1, wherein the mechanism for controllably moving the screw back and forth relative to the plunger is a motor.

3. 2. The injection molding machine according to claim 1, wherein the mechanism for controllably moving the screw forward and backward relative to the plunger is a hydraulic cylinder equipped with a brake mechanism.

4. 2. The injection molding machine according to claim 1, wherein the mechanism for controllably moving the screw forward and backward relative to the plunger is a screw length variable cylinder.

5. A cylindrical barrel having a heater on its outer periphery and storing molten resin inside; a cylindrical plunger that includes a heater on an outer periphery and a screw that moves back and forth inside the barrel to send the molten resin to the barrel, melts a resin material inside the plunger, and moves back and forth inside the barrel to inject the molten resin stored inside the barrel; a mechanism for controllably advancing the plunger relative to the barrel; A method for injection molding a resin material using an injection molding machine comprising: a flow rate and a pressure of the molten resin passing through the tip of the screw being adjusted by an opening degree of a screw check during metering of the resin material.

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