JP2012161982A - Injection molding machine and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a molding failure such as a wrinkle, twist and jetting, and to easily set a molding condition in a short time.SOLUTION: This injection molding machine includes a servo motor for filling a resin material into a molding die, and a control part which changes an injection speed stepwise by controlling the servo motor, and changes a pressure-holding force so that the pressure-holding force applied into the molding die in which the resin material is filled.

Description

  The present invention relates to an injection molding machine and an injection molding method for controlling an injection speed for filling a molding die with a resin material and a holding pressure applied to the molding die filled with the resin material.

  In general, in the injection process, a holding pressure is applied to the resin material in the cavity in order to compensate for shrinkage associated with cooling of the resin material filled in the mold and the filling process of filling the resin material in the mold mold cavity. And a pressure holding step.

  In the pressure-holding step, the gate 109 of the molding die 102 connected to the cylinder 103 of the injection molding machine is applied to the surface of the molded product by the force F applied to the resin material that is gradually solidified as shown in FIG. There is a disadvantage that wrinkles 110 occur in the vicinity.

  As a countermeasure against such molding defects, wrinkles 110 can be prevented from being generated on the surface of the molded product in the vicinity of the gate 109 of the molding die 102 by gradually reducing the holding pressure. In addition, by reducing the injection speed in the filling process, it is possible to prevent wrinkles, distortion due to distortion, traces of adhered resin scattered in the cavity, so-called jetting, from occurring in the molded product.

  For example, Patent Document 1 discloses a technique for changing the injection speed in the filling process stepwise and changing the holding pressure in the pressure holding step so as to decrease stepwise. And when performing injection molding using hard resin materials, such as a polystyrene, the method of controlling in steps in this way is taken.

Japanese Utility Model Publication No. 5-91827

  However, when performing injection molding using a soft resin material such as a thermoplastic elastomer or soft vinyl chloride, the viscosity at the time of melting is lower than that of a hard resin material, and the inside of the cavity becomes a relatively high pressure. For this reason, when a soft resin material is used, there is a problem in that the residual stress in the cavity is relatively high, and shininess tends to occur.

  Therefore, when a soft resin material is used, as in the technique described in Patent Document 1, when the injection speed and the holding pressure are changed in stages, it is very difficult to manually set the numerical values of the molding conditions in the control device. There is also a problem that a numerical value is erroneously set when a large number of molding conditions are set. Therefore, in order to reliably set such difficult molding conditions, there is a disadvantage that the operator needs skill and skill.

  That is, there is a wide range of condition setting values for preventing defects of the molded product as described above, and it is not known unless the molded product is actually molded and tested. For this reason, it takes time to find and set the optimum molding condition for obtaining a molded product as a non-defective product within the range of numerical values that can be set, and this is a factor that reduces productivity.

  In addition, molded products made while adjusting the molding conditions are all discarded because the material characteristics become unstable, and there is a problem that the resin material used for the molded products made until the molding conditions are found is wasted. is there.

  Further, in order to suppress molding defects, when finding and setting molding conditions for gently changing the injection speed and holding pressure, many fine settings of the molding conditions are required. For this reason, the number of places for setting molding conditions increases, and there are secondary problems such as erroneous input of numerical values at the time of setting molding conditions and damage to the molding die due to erroneous input.

  Accordingly, the present invention provides an injection molding machine and an injection molding method capable of solving the above-described technical problems, reducing complicated setting work of molding conditions, and setting molding conditions easily and in a short time. That is.

  In order to achieve the above-described object, the injection molding machine according to the present invention changes the injection speed steplessly by controlling the drive means for filling the molding die with the resin material and the drive means, And control means for changing the holding pressure so that the holding pressure applied to the molding die filled with the resin material is steplessly reduced.

  In addition, the injection molding method according to the present invention includes a filling step for steplessly changing an injection speed for filling the resin material in the molding die, and a stepping pressure applied to the molding die filled with the resin material. And a pressure holding step of changing the pressure holding pressure so as to be smaller.

  According to the present invention, molding conditions for obtaining a molded product as a non-defective product can be easily set in a short time. Moreover, according to this invention, it can prevent that the secondary problem of damaging a shaping die arises.

It is a schematic diagram which shows the injection molding machine of embodiment. It is a flowchart for demonstrating briefly operation | movement of the injection molding machine of embodiment. It is a figure for demonstrating the filling process and pressure-holding process in the injection molding machine of embodiment. It is a flowchart for demonstrating the case where the changeover switch is operated in the injection molding machine of embodiment. It is a schematic diagram for demonstrating the force which acts on a molded article in the pressure-holding process in an injection molding machine.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  Drawing 1 is a mimetic diagram showing the injection molding machine of an embodiment. As shown in FIG. 1, an injection molding machine 1 includes a cylinder 3 having a nozzle connected to a gate of a molding die 2, a screw 5 for transporting a resin material and filling the cavity of the molding die 2. And a servo motor 6 as a driving means for rotating the screw 5.

  Further, the injection molding machine 1 controls the servo motor 6 for filling the molding die 2 with the resin material, thereby changing the injection speed steplessly, and the molding die filled with the resin material. 2 is provided with a control unit 7 serving as a control means for changing the holding pressure applied to 2 in a stepless manner.

  The injection molding machine 1 switches between an operation state in which the injection speed is changed steplessly and the holding pressure is changed steplessly and another operation state in which the injection speed and the holding pressure are changed stepwise. A selector switch 8 is provided as a switching means.

  The servo motor 6 is rotationally driven by the control unit 7 to rotationally drive the screw 5 in the cylinder 3 and fill the molding die 2 with a resin material.

  The control unit 7 includes a control board 7 a on which a control circuit is formed, and the control board 7 a is electrically connected to the servo motor 6. The control unit 7 has a controller provided with a changeover switch 8 and various setting switches.

  The changeover switch 8 is electrically connected to the control board 7 a of the control unit 7. When the driver switches the change-over switch 8, the servo motor 6 is used to change the injection speed and holding pressure in a stepwise manner using the servo motor 6 as described above, and the injection speed and holding pressure are not changed. It is configured to be able to drive by switching to a stepless mode that changes in stages.

  That is, in this embodiment, when the changeover switch 8 is in the ON state, the control unit 7 changes the injection speed so as to increase steplessly and changes the holding pressure so as to decrease steplessly. Further, the control unit 7 controls the injection speed so as to change steplessly when the changeover switch 8 is in the on state, and the injection speed is set when a predetermined amount of the resin material is filled in the molding die 2. Control to be infinitely small.

  Further, when the changeover switch 8 is in the OFF state, the control unit 7 controls the injection speed to increase at an arbitrary stage from, for example, 1st stage to 6th stage, and a predetermined amount of resin material in the molding die 2 When the is filled, the injection speed is controlled to be reduced by, for example, one step. Further, when the changeover switch 8 is in the OFF state, the control unit 7 changes the holding pressure so as to decrease at an arbitrary stage from, for example, the first stage to the sixth stage. In addition, when the changeover switch 8 is in the OFF state, the holding pressure may be controlled so as to decrease steplessly.

  FIG. 2 is a flowchart for briefly explaining the operation of the injection molding machine 1 according to the embodiment. As shown in FIG. 2, when changing the injection speed and the holding pressure steplessly as described above, the controller of the control unit 7 of the injection molding machine 1 is operated (step S1), and the changeover switch 8 is turned on. (Step S2). The control unit 7 starts the control when the changeover switch 8 of the control board 7a is turned on (step S3), and starts driving the servo motor 6 (step S4). And the control part 7 rotates the screw 5 with the servomotor 6, and changes an injection speed and a holding pressure continuously.

  In the injection molding machine 1 configured as described above, the control of the injection speed and the holding pressure performed when the molded product is molded will be described.

  Drawing 3 is a figure for explaining the filling process and pressure holding process in injection molding machine 1 of an embodiment. In FIG. 3, the vertical axis indicates the injection speed, injection pressure, and holding pressure, and the horizontal axis indicates time. FIG. 4 is a flowchart for explaining a case where the changeover switch 8 is operated in the injection molding machine 1 of the embodiment.

  In the injection molding machine 1 of the present embodiment, as shown in FIG. 3, in the filling process in the injection process, the distance that the screw 5 moves in the cylinder 3 toward the nozzle side, in other words, with the passage of time, for example, As shown by the broken line in the figure, the injection speed is controlled to gradually increase linearly. At this time, for example, the injection pressure changes so as to form a curve as shown by a solid line in the drawing.

  Further, in the present embodiment, immediately before the filling of the resin material into the cavity of the molding die 2 is completed, for example, when about 80% to 90% of the volume of the cavity is filled, the inside of the molding die 2 In order to reduce the pressure to a predetermined pressure, control is performed so that the injection speed decreases linearly. Note that the control unit 7 controls the filling rate into the cavity at the time of starting the reduction of the injection speed, that is, the deceleration point, by the driver arbitrarily setting the molding conditions as necessary. It may be configured.

  Further, the control unit 7 performs control so that the holding pressure applied to the molding die 2 filled with the resin material is continuously reduced. The holding pressure is controlled based on the back pressure of the screw 5. In addition, as a timing for lowering the holding pressure, for example, control is performed so that the lowering of the holding pressure starts when the resin material is filled to about 95% to 98% in the cavity.

  In the present embodiment, by changing the injection speed linearly in a stepless manner, the residual stress of the resin material filled in the cavity is reduced compared to the case where the injection speed is changed in multiple steps. Occurrence is suppressed. Similar to the injection speed, in this embodiment, the holding pressure is linearly reduced steplessly, so that the resin material filled in the cavity is compared with the case where the holding pressure is reduced in multiple steps. Residual stress is reduced, and the occurrence of shininess is suppressed.

  The switching operation of the changeover switch 8 in this embodiment will be briefly described. As shown in FIG. 4, molding is started (step S11), and the driver determines whether or not molding defects such as wrinkles occur in the molded product (step S12). When wrinkles or the like are generated in the molded product, the injection speed and the holding pressure are controlled by the control unit 7 as described above by turning on the changeover switch 8. By operating the control unit 7 in this way, it is not necessary for the driver to set the molding conditions necessary for changing the injection speed and the holding pressure in stages. Therefore, it is not necessary for the driver to perform a part of complicated setting work, and the molding conditions can be easily set. Next, the driver manually sets the molding conditions (step S14).

  If no molding failure has occurred in the molded product, the molding conditions are set while the changeover switch 8 remains off (step S14). In this case, the injection speed and the holding pressure are controlled so as to change in multiple stages.

  After setting the molding conditions, the driver determines whether or not molding defects such as wrinkles occur in the molded product (step S15). At this time, if a molding defect has occurred in the molded product, the process returns to step S14, the molding conditions are set again, and thereafter the molding conditions are set until no molding defect occurs in the molded product. Repeated. If no molding defect has occurred in the molded product, a desired amount of molded product is produced under the molding conditions (step S16), and molding is terminated (step S17).

  As described above, according to the injection molding machine 1 of the embodiment, the control unit 7 controls the servo motor 6 for filling the molding die 2 with the resin material, thereby changing the injection speed steplessly. The holding pressure applied to the molding die 2 filled with the resin material is changed steplessly. As a result, in the present embodiment, when injection molding is performed using a soft resin material having a low viscosity at the time of melting compared to a hard resin material, a high pressure that causes molding defects does not occur in the filling process. The resin material can be filled at a relatively low pressure, and in the pressure-holding step, the pressure can be held at a relatively low pressure so as not to cause a high pressure that causes molding defects.

  Therefore, according to the present embodiment, it is possible to prevent the occurrence of wrinkles, distortion, and jetting, and to easily and quickly set the molding conditions for obtaining a molded product as a non-defective product. For this reason, the resin material required for setting the optimal molding conditions can be reduced, and the productivity of the molded product can be improved. In addition, according to the present embodiment, it is possible to prevent the occurrence of a secondary problem that would damage the molding die 2.

  In the injection molding machine 1 according to the present embodiment, the injection speed is controlled to gradually increase linearly and the holding pressure is controlled to gradually decrease linearly. It is not limited. Depending on the requirements of the molding conditions, for example, the inclination angle of the straight line in which the injection speed and holding pressure change is controlled to change, or the injection speed and holding pressure are controlled to gradually change in a curve. May be.

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Molding die 6 Servo motor 7 Control part 8 Changeover switch

Claims (5)

Drive means for filling the molding die with resin material;
By controlling the drive means, the injection speed is changed steplessly, and the holding pressure is changed steplessly so that the holding pressure applied to the molding die filled with the resin material is reduced steplessly. And an injection molding machine.   Switching means for switching the injection speed steplessly and switching between an operation state where the holding pressure is changed steplessly and another operation state where the injection speed and the holding pressure change stepwise. The injection molding machine according to claim 1.   The injection molding machine according to claim 1 or 2, wherein the control means changes the injection speed linearly and changes the holding pressure linearly. A filling process for steplessly changing the injection speed for filling the resin material into the molding die;
A pressure holding step of changing the holding pressure so that the holding pressure applied in the molding die filled with the resin material is continuously reduced.   5. The injection molding method according to claim 4, wherein, in the filling step, the injection speed is changed linearly and the holding pressure is changed linearly.

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