JP2012143960A - Method of changing resin and color for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of changing a resin and changing a color without interrupting a continuous production operation of an injection molding machine.SOLUTION: After the resin or the color is changed and a prescribed quantity of the resin is molded in the continuous production operation, a screw is continuously rotated in a state where the screw forward movement and the screw backward movement of a molten resin in a screw advanced position are obstructed. Next, the obstruction of the screw backward movement is canceled and the prescribed quantity of the molten resin is measured and filled in a mold cavity under the same injection condition as that in the continuous production operation and after a resin change and a color change operation mode of taking out the molded article from the mold are repeated prescribed preset times, the injection molding is switched to the continuous production operation.

Description

  The present invention relates to a resin change and a color change method for changing a resin or a color in a cylinder barrel of an injection molding machine, and more particularly to a resin change and a color change method performed while continuing molding without interrupting a continuous molding operation. .

Conventionally, during the production operation of an injection molding machine, when the old resin in the cylinder barrel is replaced with another resin of a different type or color, the resin is changed and the color is changed with the following configuration.
That is, with the nozzle attached to the tip of the cylinder barrel in contact with the sprue bush of the mold, the old resin in the cylinder barrel is injected and filled into the mold, and then the new resin is supplied into the cylinder barrel. While plasticizing with low back pressure, the screw is retracted and new resin is stored at the tip of the screw, and the screw is moved forward and back in a stroke smaller than the forward stroke until the screw reaches the forward position. Performs inching and high-speed injection that fills the mold with new resin repeatedly. Next, the resin replacement molding cycle for taking out the molded product from the mold is repeated a plurality of times, and then the process shifts to injection molding with a new resin. (See Patent Document 1)

  In the resin change and color change methods with such a configuration, the plasticization measurement and injection filling behavior change greatly during production operation, so the supply of molten resin into the cavity is not stable, and the mold resin when the screw is retracted Since the flow stops and is cooled and solidified, it becomes impossible to fill the resin at the next inching injection, and further, since the normal molding operation is performed until the old resin is empty, the empty shot has insufficient resin amount, The molding operation could not be performed stably, and the molding operation was interrupted.

  Moreover, the staying location of the molten resin was investigated in advance in the cylinder barrel of the injection molding machine. Residue of the molten resin causes resin change and color change failure. As a result of the investigation, it was found that there was no contact with the screw parts, the flow rate of the molten resin at the time of injection filling was slow (the scraping force of the resin was small), and the inner wall surface at the tip of the cylinder barrel was the most stagnant. As a means for discharging the residence of the molten resin at this location, for example, a method of using the scraping force by the unmelted resin in combination with the plasticizing measurement conditions in which the unmelted resin is mixed and the injection conditions shown in the prior art Can be understood that it is effective, but because it is significantly different from the state of plasticized molten resin during production operation, the injection filling behavior into the mold is not stable, and color change operation can be performed without interrupting production operation. It is difficult to continue. In addition, even in shocking operating conditions due to inching high-speed injection and changes in the screw back pressure shown in the prior art, the inner diameter center of the cylinder barrel changes the flow velocity of the molten resin, but the inner diameter outer periphery Since the flow rate of the molten resin is slowed down by the wall resistance, the flow rate of the molten resin on the inner wall surface of the cylinder barrel tip cannot be changed greatly, the scraping force of the staying resin is small, efficient resin and color change I had a problem that I could not expect sex.

JP 11-28753 A

  The present invention has been made in view of the problems of the conventional resin changing and color changing methods described above, and is an efficient injection molding without interrupting the production operation by switching the resin while continuously supplying the resin. It aims at providing the resin change and color change method of a machine.

  The resin and color change method of an injection molding machine according to claim 1 of the present invention is a resin change and color change method of an injection molding machine that changes resin or color during continuous production operation. A first step in which the number of production shots in which resin or color mixing occurs in the product is determined in advance, and after the predetermined number of production shots is molded, the screw is continuously rotated at a predetermined screw advance position for a predetermined time, and the continuous production. Second step of plasticizing and weighing the resin under the same measurement back pressure and screw rotation speed conditions as in the operation, and closing the mold, and the same injection holding pressure, speed and speed distribution as in the continuous production operation And a third step of filling the cavity space of the mold with the molten resin plasticized in the second step to obtain a molded body, and after cooling and holding for a predetermined time, the mold is opened and the molding is performed. Remove body from mold The fourth process is shifted to the resin change and color change operation mode, and the resin change and color change operation mode is completed by repeating the first process to the fourth process a predetermined number of times, and then the continuous process. It is characterized by shifting to production operation.

  The resin and color changing method of the injection molding machine according to claim 2 of the present invention is the invention according to claim 1, wherein the first step is such that the metering back pressure is higher than the metering back pressure during the continuous production operation. It sets, and it transfers to the said 2nd process from the said 1st process at the predetermined pressure | voltage fall speed, It is characterized by the above-mentioned.

The resin and color changing method of the injection molding machine according to claim 3 of the present invention are the cushion position at the time of the continuous production operation and the screw advance position at the first step in the invention according to claim 1 or 2. If there is a difference between the two, the measurement completion position in the second step is set based on the screw stroke difference, and the injection holding pressure speed switching position in the third step is corrected. .
The resin and color changing method of the injection molding machine according to claim 4 of the present invention is the continuous production according to the invention according to claim 1 or 2 according to the number of production shots in which the resin and color mixture occur. It is characterized in that the transition from operation to resin change and color change operation mode is automatically performed.

Since the screw is continuously rotated at the screw advance position for a predetermined time, the distance between the screw and the inner wall surface of the cylinder barrel tip is reduced at the screw advance position so that the distance between the screw and the inner wall surface of the cylinder barrel tip is reduced. When a thin molten resin layer is formed on the screw and the screw is continuously rotated in this state, a strong rotational shearing force is generated in the thin molten resin layer, and this strong rotational shearing force is used to retain the inner wall surface of the cylinder barrel tip. In order to scrape off the resin, the scraping power of the resin is high, and the resin and the color change are preferentially performed at the place where the resin and the color stay much. Therefore, efficient resin and color change can be realized. Time can be shortened.
In addition, molding is performed under the same plasticization and injection conditions as in the continuous production operation, and the metering stroke is constant in the color change operation mode, and the mold cavity is filled with molten resin. There is no excess (overpack) or underfilling (short shot). For this reason, efficient resin and color change operation can be performed without interrupting the continuous molding operation of the injection molding machine.

It is explanatory drawing which shows roughly the whole structure of the injection molding machine used for the resin change and color change method of this invention. It is a flowchart explaining the resin change of the injection molding machine as embodiment of this invention, and a color change method. It is a time chart explaining the resin change of the injection molding machine as embodiment of this invention, and a color change method.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings, flowcharts, and time charts. First, the configuration of the injection molding machine 100 used in the present invention will be described. As shown in FIG. 1, an injection molding machine 100 used in the present invention includes a mold 10, a mold clamping device 20, an injection device 30, and a mold clamping device 20 (not shown) and a control device that controls the injection device 30. Yes.
The mold 10 includes a fixed mold 11 attached to a fixed platen 21 and a movable mold 12 attached to a movable platen 22, and a mold clamping cylinder 23 that opens and closes the mold 10 provided in the mold clamping device 20. Thus, the movable platen 22 and the movable mold 12 can be moved forward and backward. The movable platen 22 and the movable die 12 are guided by a tie bar (not shown) and move forward and backward with respect to the fixed die 11 and the fixed platen 21. Reference numeral 13 denotes a cavity space of the mold 10 formed by the fixed mold 11 and the movable mold 12.

  Next, the configuration of the injection device 30 will be described. An injection device 30 shown in FIG. 1 includes a cylinder barrel 31, a screw 32 that is built in the cylinder barrel 31 and has a flight, and a hopper 33 that supplies a molded resin material into the cylinder barrel 31. A screw moving means 34 for moving the screw 32 and a screw rotating means 35 for rotationally driving the screw 32 are provided. A heater (not shown) is attached to the outer peripheral surface of the cylinder barrel 31.

  The injection device 30 is configured such that a pellet-shaped molding resin material is supplied from the hopper 33 to the cylinder barrel 31 when the screw 32 is rotated by the screw rotating means 35, and the supplied pellet-shaped molding is performed. The resin material is heated by a heater attached to the cylinder barrel 31 and melted by receiving a kneading compression action by the rotation of the screw 32, and is sent to the front of the screw 32. The molten resin sent to the front of the screw 32 can be injected and filled into the cavity space 13 from the nozzle 36 attached to the tip of the barrel 31 by the screw 32 advanced by the screw moving means 34. The nozzle 36 is provided with a molten resin shut-off means 37 to prevent the molten resin from leaking from the tip of the nozzle 36 to the outside when the screw 32 is rotated in the closed state.

As shown in FIG. 1, the hydraulic drive unit is used for the screw moving unit 34 and the screw rotating unit 35 of the injection device 30 used in the present invention. However, the configuration is not limited to this configuration, and an electric servo motor is used as the drive unit. The structure to be used may be used.
Further, although the mold clamping device 20 is a direct pressure type mold clamping mechanism using a hydraulically driven mold clamping cylinder 23, the toggle mechanism may be driven by an electric servo motor.

  The control device (not shown) includes a mold clamping side control unit that controls the mold clamping device 20, a mold clamping condition setter that sets the mold clamping conditions, an injection control unit that controls the injection device, and injection conditions, resin replacement, and An injection condition setting device for setting the color change condition is provided, and the resin change and the color change can be performed without interrupting the continuous molding operation.

Next, the resin change and color change method of the present invention will be described with reference to FIGS. The resin changing and color changing methods of the present invention are as follows.
(A) A first step of continuously rotating the screw for a predetermined time at a predetermined screw advance position.
(B) A second step in which the resin is plasticized and measured under the same measurement back pressure and screw rotation speed conditions as in the continuous production operation.
(C) Closing the mold and filling the cavity space of the mold with the molten resin plasticized in the second step under the same injection holding pressure, speed and speed distribution conditions as in the continuous production operation. And a third step of obtaining a molded body.
(D) A fourth step of opening the mold and taking out the molded body from the mold after cooling and holding for a predetermined time.

As shown in FIGS. 2 and 3, the transition to the resin change and color change operation mode is performed by first switching the material supply during the continuous production operation and mixing the resin calculated from the relationship between the amount of residual resin and the molded product. Alternatively, the production shot number N with no color mixture is formed, and the continuous production operation is finished.
The end of the continuous production operation is a state in which the mold opening is completed in the mold clamping device and the molded product is taken out. In the last production shot of the continuous production operation, the weighing operation is switched to the resin change and color change operation mode after the injection filling is completed. That is, the last production shot of the continuous production operation and the resin change and color change operation modes are lap operations. Both lap operations can be performed by the shut-off means 37. If the injection molding machine is not equipped with the shut-off means 37, it is possible, for example, if the resin flow path in the mold is equipped with a resin flow path closing means such as a valve gate means. This lapping operation is also applied between production shots in the resin change and color change operation modes. If the resin channel closing means is not equipped, the start of the mold opening / product removal process of the previous production shot is delayed until the end of the first process and the second process in the resin change and color change operation modes. Will respond.
Then, switching to the resin change and color change operation modes is performed by detecting that the remaining number of production shots in the continuous production operation set in advance matches the number N of production shots.

  The color of the same resin material that has been colored is switched by, for example, setting the hopper 33 to a twin hopper structure and selectively using one of the hoppers. In the case of molding using the same resin material with a colorant (dry color, color masterbatch, etc.), for example, the required number of colors is prepared for the colorant supply means. It can carry out by changing to the supply means of a coloring agent.

  In the (a) first step of the resin change and color change operation modes thus transferred, the screw 32 is continuously rotated for a predetermined time at a predetermined screw advance position shown in FIG. The screw 32 is driven to rotate at the number of rotations during continuous production operation. In this process, the melt resin is pushed forward by the rotation of the screw 32, and the shut-off means 37 is closed so as not to flow into the cavity space 13 of the mold through the nozzle 36. Further, in order to realize continuous rotation of the screw 32 for a predetermined time at a predetermined screw advance position, the measured back pressure BP2 that does not move backward even by the reaction force of the resin pressure pushed out of the screw 32 by the pressure adjusting valve 38 provided in the screw moving means 34. Is set so that the screw advance position is maintained even when the screw 32 rotates. The rotation time of the screw 32 is set by the screw rotation time T.

By continuously rotating the screw 32 for a predetermined time at the screw advance position, the distance between the screw 32 and the inner wall surface of the tip end of the cylinder barrel 31 is reduced by setting the screw advance position. A thin molten resin layer is formed between the wall surface and a strong rotational shearing force is generated in the thin molten resin layer. By utilizing this strong rotational shearing force, the scraping force of the retained resin on the inner wall surface of the cylinder barrel 31 is high. Since the resin and the color change are preferentially performed at a place where the resin or the color stays a lot, efficient resin and color change can be realized, and the resin and color change time can be shortened. In addition, although the rotation speed of the screw 32 was made the same as the time of continuous production operation, in order to increase scraping power, you may change rotation speed high.
In addition, when an electrically driven injection device using a servo motor is used, a torque back pressure can be applied to the rear portion of the screw by outputting torque to the servo motor of the screw moving means.

(B) In the second step, the resin is plasticized and weighed under the same conditions of the measurement back pressure BP1 and screw rotation speed as in the continuous production operation. By doing this, the state of the plasticized and weighed molten resin can be made almost the same as in continuous production operation, and the same molded product as in continuous production operation can be obtained when combined with injection filling conditions in the subsequent process, and production operation is interrupted. Can be avoided.
In addition, the measurement back pressure that is set by the pressure regulating valve 38 when changing from the first step to the second step is changed from BP2 to BP1, and the gradient of the step-down speed is determined by the predetermined back pressure step-down time t1. The When the back pressure pressure reduction time is long, the resin pressure in the barrel 31 gradually decreases, and when it is short, the pressure is suddenly decreased and air remaining in the molten resin or a gas generated by thermal decomposition of the molten resin is generated in the form of bubbles. (Same as the principle that gas components are extracted from a saturated solution in which gas is dissolved by rapid pressure drop), foamed gas or the like is ejected at the time of injection filling, and residual resin in the nozzle 36 or the mold hot runner Demonstrate the effect of forcibly discharging.
The measurement completion position S1 is performed under the same conditions as in the continuous production operation.

(C) In the third step, the mold was closed and plasticized in the cavity space of the mold in the second step under the same injection holding pressure, speed and speed distribution conditions as in the continuous production operation. Filled with molten resin to obtain a molded body. By plasticizing the resin under the same measurement back pressure BP1 and screw rotation speed conditions as in the second process continuous production operation, it is possible to form a molded product almost equivalent to that in the continuous production operation. Can avoid the trouble of interrupting.
However, the second process and the third process are the same as the conditions in the continuous production operation, but the first process is different from that in the continuous production operation. May be different. Therefore, the cushion position C2 in the injection process is detected, a deviation amount δ1 from the cushion position C1 in the continuous production operation is calculated, and the measurement completion position S1 after the second time is corrected by δ2 based on the detected deviation amount, and the measurement completion position. S2 is determined. The deviation amount δ1 and the correction amount δ2 are the same value. By doing so, the operating conditions are almost as close as those during continuous production operation, and troubles such as interruption of production operation can be reliably avoided. Furthermore, by making the cushion position the same as in the continuous production operation, there is an advantage that the switching from the resin change and color change operation modes to the continuous production operation mode can be performed smoothly.
Similarly, the position of speed change in the injection process is corrected by the detected deviation amount δ1, and the second and subsequent injection speed changes are determined.

(D) In the fourth step, after cooling for a predetermined time, the movable mold 12 is opened and the molded body is taken out from the mold apparatus 10. Thereby, one molding cycle of the resin change and color change operation modes is completed, and this molding cycle is repeated a predetermined number of times. A predetermined number of times are repeated to switch from the resin change and color change operation mode to the continuous production operation mode, and shift to a new resin continuous production operation.
In the transition to the continuous production operation of a new resin, the resin change and color change operation production and the continuous production operation are lapped, but the production may be temporarily stopped for quality confirmation of the molded product.

  As described above, the plasticizing measurement conditions and injection pressure holding conditions are the same as those in continuous production operation, and the measurement completion position and injection speed switching position are corrected and corrected according to the change in cushion position. Since molding defects such as shot shots and overpacks (burr defects) do not occur, stable molding can be performed, and molding operations are not interrupted even if resin or color change operations are performed during continuous production operations. In addition, since the resin and color change are preferentially performed at locations where the resin or color stays a lot, efficient resin and color change can be realized, and the resin and color change time can be shortened.

The excellent effect of the present invention will be described with reference to examples of the present invention and comparative examples. For molding, a horizontal toggle type electric drive injection molding machine (MD850S-V injection molding machine manufactured by Ube Industries) is used as an injection molding machine, and polypropylene for automobile interior (MRF = 35 manufactured by prime polymer) is used as a resin material. The new color was changed from black masterbatch (manufactured by Tokyo Ink 3%) to white (no masterbatch).
The molded product is a 350 × 350 plate-shaped product with a mass of 480 grams. The resin temperature was set to 190 ° C.
During the black molding process, the black masterbatch supply was stopped, and after the color mixture started to appear in the molded product, the color change mode was switched to the continuous molding operation to obtain a good product with no color mixture. It was done by confirming the completion of color change by the number of times.

[Example 1]
As Example 1, the rotational speed of the screw 32, the measured back pressure BP1, and the injection holding pressure are set to be the same as those in the continuous production operation, the measured back pressure PB2 in the first step is 20 MPa higher than that in the continuous production operation, and the screw rotation time T Was set to 10 seconds, the back pressure reduction time t1 was set to 10 seconds, and the color change measurement completion position S2 corrected for the measurement completion position was set, and the color change operation was performed. A continuous molding operation could be performed, and a non-colored good product was obtained after molding 10 times.

[Example 2]
As Example 2, a molding example in which the measured back pressure BP2 in the first step is set higher than Example 1 will be described. The rotational speed of the screw 32, the measured back pressure BP1, and the injection holding pressure are set to be the same as those in the continuous production operation, the measured back pressure PB2 in the first step is 50 MPa higher than in the continuous production operation, and the screw rotation time T is set to 10 seconds. The back pressure reduction time t1 was set to 10 seconds, the color change measurement completion position S2 with the measurement completion position corrected, and the color change operation was performed. A continuous molding operation could be performed, and a good product with no color mixing was obtained after molding 5 times.

[Example 3]
As Example 3, a molding example in which the screw rotation time T and the back pressure reduction time t1 in the first step are set shorter than in Example 2 will be described. The rotational speed of the screw 32, the measured back pressure BP1, and the injection holding pressure are set to be the same as those in the continuous production operation, the measured back pressure PB2 in the first step is 50 MPa higher than in the continuous production operation, and the screw rotation time T is set to 5 seconds. The back pressure reduction time t1 was set to 1 second, and the color change measurement completion position S2 in which the measurement completion position was corrected was set, and the color change operation was performed. A continuous molding operation was performed, and a good product with no color mixing was obtained after three moldings.

[Comparative Example 1]
A molding example as Comparative Example 1 will be described. The injection molding machine, molding material, and molded product used are the same as in the examples.
The molding conditions during color change continuous operation were set to the same conditions as during continuous production operation, and color change operation was performed. Although the continuous molding operation could be performed, a good product with no color mixture could not be obtained even with 50 moldings.

[Comparative Example 2]
Next, as Comparative Example 2, the color change operation was performed under the same conditions except that the measurement completion position S2 in the color change operation of Example 1 was changed to the measurement completion position S1 in the continuous production operation. An overpack (burr failure) occurred and the continuous operation was interrupted, and the continuous molding operation could not be continued.

[Comparative Example 3]
As Comparative Example 3, the color change operation was performed by setting the same weighing conditions during the continuous production operation and setting the injection condition to injection / reverse inching injection. A short shot occurred, the continuous operation was interrupted, and the continuous molding operation could not be continued.

As described above, according to the present invention, since the screw position is maintained by setting a high measurement back pressure before the plasticizing and measuring step and the screw is continuously rotated at a predetermined forward limit position, the resin is scraped by rotating the screw. Peeling of the remaining old resin is promoted by the take-off force, and the resin and the color change are preferentially changed in the resin and the portion where the color stays, so that an efficient resin and color change can be realized, and the amount of resin required for the color change Time can be saved.
In addition, since the first color change injection process data is detected and the measurement position for the second time and the speed switching position of the injection process are corrected, short shot (underfilling), overpack (overfilling), etc. Molding defects are prevented, resin replacement and color change operation can be performed continuously, and the continuous molding operation of the injection molding machine is not interrupted.

DESCRIPTION OF SYMBOLS 10 Mold 11 Fixed mold 12 Movable mold 13 Cavity space 20 Clamping device 21 Fixed plate 22 Movable plate 23 Clamping cylinder 30 Injection device 31 Cylinder barrel 32 Screw 33 Hopper 34 Screw moving means 35 Screw rotating means 36 Nozzle 37 Shut OFF means 38 Pressure regulating valve BP1 Metering back pressure during continuous production operation BP2 Metering back pressure during color change operation C1 Cushion position during continuous production operation C2 Cushion position during color change operation S1 Measurement completion position during continuous production operation S2 Measurement completion position during color change operation N Number of non-defective shots T Screw rotation time t1 Back pressure reduction time δ1 Cushion position deviation (screw stroke difference)
δ2 Correction amount equivalent to deviation T1 Injection speed switching position during continuous production operation T2 Injection speed switching position during color change molding operation

Claims (4)

In resin change and color change methods of injection molding machines that change resin or color during continuous production operation,
After switching the resin or color supply, the number of production shots where resin or color mixing occurs in the product is determined in advance, and after molding the determined number of production shots,
A first step of continuously rotating the screw for a predetermined time at a predetermined screw advance position;
A second step of plasticizing and weighing the resin under the same measurement back pressure and screw rotation speed conditions as in the continuous production operation;
The mold is closed and filled with the molten resin plasticized in the second step into the cavity space of the mold under the same injection holding pressure, speed and speed distribution conditions as in the continuous production operation. A third step of obtaining a body;
After cooling and holding for a predetermined time, the mold is opened and the fourth step of taking out the molded body from the mold, and the process shifts to a resin change and color change operation mode,
The resin change and color change operation modes are completed by repeating the first to fourth steps a predetermined number of times,
Next, a method for changing the resin and changing the color of the injection molding machine, wherein the process is shifted to the continuous production operation.   The first step is characterized in that the metered back pressure is set higher than the metered back pressure during the continuous production operation, and the process proceeds from the first step to the second step at a predetermined step-down speed. The resin change and color change method of the injection molding machine described in 1.   When there is a difference between the cushion position during the continuous production operation and the screw advance position in the first step, the measurement completion position in the second step is set based on the screw stroke difference, and the third step The method for changing the resin and color of an injection molding machine according to claim 1, wherein a speed switching position of injection holding pressure in the process is corrected.   The injection molding according to claim 1 or 2, wherein a transition from continuous production operation to resin change and color change operation mode is automatically performed in accordance with the number of production shots in which the resin and color mixture occur. How to change resin and color of machine.

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