JP2022077118A - Molding method for pre-plasticize injection molding machine - Google Patents

Abstract

To improve a quality of a molded product, reduce quality variation, improve production efficiency, and increase a yield rate of the final molded product by reducing the number of defective products.SOLUTION: A molding method for a pre-plasticize injection molding machine includes: a plasticizing process (S8) in which a molding material is plasticized by rotating a screw 2 built into a plasticizer Mp and is supplied to an injection device Mi; an injection process (S4) in which resin R supplied by advancing a plunger 3 built into the injection device Mi is injected and filled into a mold C from an injection nozzle 5; and, especially, a resin return process (S7) in which a supply channel 4 is opened at a predetermined timing after a cooling start (S6) of the resin R filled into the mold C by the injection process (S4) and the plunger 3 is advanced to a most forward position Xs to return resin Rr remaining in front of the plunger 3 to the plasticizer Mp by making the resin flow backward in the supply channel 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a molding method of a pre-plastic injection molding machine in which a plasticizing device having a built-in screw and an injection device having a built-in plunger are separately configured.

Conventionally, a plasticizing step of plasticizing a molded material charged by rotating a screw built in a plasticizing device and supplying the plasticized resin to an injection device through a supply path, and after this plasticizing step, the supply As a molding method of a pre-plastic injection molding machine including at least an injection step of closing a path and injecting and filling a mold with resin supplied by advancing a plunger built in an injection device from an injection nozzle, for example, a patent. A molding method used for a control method of a pre-plastic injection molding machine disclosed in Document 1 and a molding method used for a backflow prevention method of a pre-plastic injection molding machine disclosed in Patent Document 2 are known.

In the control method of the pre-plastic injection molding machine of Patent Document 1, the screw built in the plastic cylinder is rotated to plastically melt the molding material, and the molten resin is charged to the injection cylinder through a check valve in an open state. , The plunger built into this injection cylinder is retracted for weighing. In particular, when the plunger reaches a preset weighing end position during weighing, the rotation of the screw is stopped and the amount of rotation of the screw is measured in advance. And, it is rotated in the reverse direction according to the control conditions set by the rotation speed, and then the check valve arranged between the plasticized cylinder and the injection cylinder is closed. Further, the backflow prevention method of the pre-plastic injection molding machine of Patent Document 2 includes an injection cylinder having a plunger built in and a plasticized cylinder having a plastic screw equipped with a check valve at the tip that can rotate and move forward and backward. Are connected in parallel by a resin path provided over the tip, and a screw moving means and a motor for rotation are provided at the rear of the plasticized cylinder, and the backflow prevention valve is provided by the advance / retreat movement of the screw by the screw moving means. It is a pre-plastic injection molding machine that opens and closes, and in particular, when the plunger retracts due to the material charge due to the rotation of the screw and the retracted position reaches just before the weighing end position, the rotation speed of the screw is switched to a low speed. After that, the valve is moved backward at a lower pressure than when the valve was opened to close the valve, and then the screw rotation is stopped to prevent the resin from flowing back to the plasticized cylinder side after the measurement is completed.

Japanese Unexamined Patent Publication No. 2004-255588 Japanese Unexamined Patent Publication No. 11-207794

However, the above-mentioned molding method of the conventional pre-plastic injection molding machine still has the following problems to be solved.

That is, in the case of a pre-plastic injection molding machine, in the plasticization step in which the resin (molten resin) supplied from the plasticizing device is accumulated in the injection cylinder of the injection device, it is first accumulated in front of the plunger and then sequentially. It is accumulated so as to be stacked in the front (injection nozzle side). On the other hand, in the injection step, the molten resin is injected and filled in the mold by moving the plunger forward, and a predetermined holding pressure is applied to the resin in the mold in the pressure holding step following this injection step. Since it is necessary, the plunger to be moved forward is usually stopped before the frontmost position to leave a predetermined amount of resin in the injection cylinder.

In this case, the plunger in the injection cylinder does not rotate like a screw, and it repeatedly moves forward and backward, so that a part of the resin remaining in the injection cylinder remains as it is for a long time. It tends to stay in a stagnant state. As a result, the residual resin gradually deteriorates such as discoloration and carbonization, and when mixed in the molded product, the quality and homogeneity of the molded product are likely to deteriorate. In addition, since it is necessary to deal with this problem, it is usually necessary to clean the inside of the injection cylinder by regular maintenance, which increases the work man-hours and labor during production, and further, the production accompanying this. There was a problem that the efficiency (production efficiency) was lowered.

An object of the present invention is to provide a molding method for a pre-plastic injection molding machine that solves the problems existing in such a background technique.

In order to solve the above-mentioned problems, the present invention plasticizes the molded material charged by rotating the screw 2 built in the plasticizing device Mp, and transfers the plasticized resin R to the injection device Mi through the supply path 4. The plasticization step (S8) to be supplied, and after this plasticization step (S8), the resin R supplied by closing the supply path 4 and advancing the plunger 3 built in the injection device Mi is ejected from the injection nozzle 5 to the mold. In the molding method of the pre-plastic injection molding machine M including at least an injection step (S4) for injecting and filling C, a predetermined method after the start of cooling (S6) of the resin R filled in the mold C by the injection step (S4). A resin recirculation step (returning the resin Rr remaining in front of the plunger 3 by opening the supply path 4 at the timing and advancing the plunger 3 to the most advanced position Xs by causing the supply path 4 to flow back to the plasticizer Mp. It is characterized by providing S7).

In this case, according to a preferred embodiment of the invention, the resin reflux step (S7) may be executed in the first mode in which the screw 2 is stopped when the plunger 3 is moved forward, or the screw 2 may be executed when the plunger 3 is moved forward. The first mode and the second mode may be switched by the selection means. Further, the plasticization step (S8) can be performed after the resin reflux step (S7), and the back pressure of the plunger 3 in the plasticization step (S8) can be variably set.

According to the molding method of the pre-plastic injection molding machine according to the present invention by such a method, the following remarkable effects are obtained.

(1) Since the resin R remaining in front of the plunger 3 is refluxed to the plasticizer Mp in each molding cycle, the resin R remaining in the injection cylinder should be eliminated and the problem of remaining in the injection cylinder should be eliminated. Can be done. As a result, it is possible to prevent the resin deteriorated due to the residue from being mixed into the molded product, so that the quality of the molded product can be further improved and the variation in the quality of the molded product can be reduced. In addition, it is possible to reduce the work man-hours and labor during production, such as reducing the maintenance for cleaning the inside of the injection cylinder, and to improve the production efficiency (production efficiency) associated with this, as well as the resin. Waste of (resources) can be reduced.

(2) By refluxing the remaining resin to the plasticizing device Mp and mixing it with the resin in the plasticizing device Mp, the plasticizing treatment can be performed again, so that a molten resin having more homogeneity can be obtained. It is possible to increase the yield rate of the final molded product by reducing the number of defective products. As a result, it becomes possible to improve production efficiency and reduce production costs, especially in the production of large-sized molded products and special resin molded products. From this point of view, avoiding resource loss and avoiding waste of energy consumption. Can also contribute effectively.

(3) According to a preferred embodiment, when the resin recirculation step (S7) is performed, if the first mode for stopping the screw 2 when the plunger 3 is moved forward is used, the resin R is recirculated only by the forward operation of the plunger 3. Therefore, it is possible to facilitate the implementation including the control process.

(4) According to a preferred embodiment, when the resin recirculation step (S7) is performed, the pressure on the plasticizer Mp side can be reduced by using the second mode in which the screw 2 is rotated in the reverse direction when the plunger 3 is moved forward. Therefore, the reflux treatment can be performed quickly, and the reflux time and the amount of reflux can be easily adjusted by variably controlling the rotation speed.

(5) According to a preferred embodiment, if the resin recirculation step (S7) is provided with a selection means for switching between the first mode and the second mode, the operator can arbitrarily select the first mode or the second mode. The optimum mode can be selected according to the flow rate, the type of molding material, and the like.

(6) According to a preferred embodiment, if the plasticization step (S8) is performed after the resin recirculation step (S7) and the back pressure of the plunger 3 in the plasticization step (S8) can be variably set, the back pressure of the plunger 3 can be set variably. Since the pressure can be set according to the amount of recirculation, the type of molding material, etc., it is possible to realize an appropriate mixing treatment of the new resin R and the recirculated residual resin Rr, and it is possible to realize a more homogeneous plasticization treatment. A higher quality molded product can be obtained.

A flowchart showing step by step each molding process of the molding method of the pre-plastic injection molding machine according to the preferred embodiment of the present invention. A flowchart showing step by step the detailed processing of the initial plasticization process in the molding process of the same molding method. A flowchart showing step by step the detailed processing of the resin reflux process in the molding process of the same molding method. Configuration diagram of a pre-plastic injection molding machine that can carry out the same molding method, A block diagram showing the stop valve of the pre-plastic injection molding machine extracted. The first explanatory diagram showing the operation at the time of molding by the same molding method in principle, The second explanatory diagram, which shows the operation at the time of molding by the same molding method in principle, A third explanatory diagram showing the operation during molding by the same molding method in principle,

Next, preferred embodiments according to the present invention will be given and will be described in detail with reference to the drawings.

First, the configuration of the pre-plastic injection molding machine M suitable for carrying out the molding method according to the present embodiment will be described with reference to FIGS. 4 and 5.

As shown in FIG. 4, the pre-plastic injection molding machine M is roughly classified into a plasticizing device Mp and an injection device Mi. The injection device Mi is horizontally installed on a machine base (not shown), and is provided with an injection cylinder 11 at the front and an injection drive unit 12 at the rear. The injection cylinder 11 has a built-in plunger 3 that can be freely moved forward and backward, and is provided with an injection nozzle 5 at the front end of the injection cylinder 11. The central position of the inner front end of the injection cylinder 11 and the injection nozzle 5 communicate with each other by a resin path. Further, the exemplary injection drive unit 12 is configured by a hydraulic drive cylinder 12d containing a drive piston 12p. Then, the tip of the piston rod 12pr protruding forward from the drive piston 12p is coupled to the rear end of the plunger 3. In the figure, reference numeral 54 denotes a plunger position sensor such as an optical sensor that detects the position of the plunger 3 in the front-rear direction. A heating heater (not shown) is mounted on the outer peripheral surfaces of the injection cylinder 11 and the injection nozzle 5.

On the other hand, as shown in FIG. 4, the thermoplastic device Mp is provided with a heating cylinder 21 at the front portion and a plasticization drive unit 22 at the rear portion, and the entire surface is tilted downward to the front end of the heating cylinder 21. The portion is coupled to the upper surface of the front end portion of the injection cylinder 11 via the valve block portion 23. The heating cylinder 21 has a screw 2 built-in, and is provided with a hopper 21h at the rear position of the heating cylinder 21 for charging a molding material into the inside of the heating cylinder 21. Further, the exemplary plasticized drive unit 22 is composed of an oil motor 22 m, and the rotary output shaft 22 ms of the oil motor 22 m is coupled to the rear end of the screw 2. Therefore, this plasticizer Mp has a forward / reverse rotation function with respect to the screw 2. In the figure, reference numeral 55 indicates a motor rotation sensor such as a rotary encoder that detects the rotation speed (rotational speed) of the oil motor 22m. A heating heater (not shown) is mounted on the outer peripheral surface of the heating cylinder 21.

Then, as shown in FIG. 4, the central position of the front end inside the heating cylinder 21 and the upper position of the inner front end of the injection cylinder 11 communicate with each other by the supply path 4, and the middle of the supply path 4 inside the valve block portion 23. The position is provided with a stop valve 7 that opens and closes (opens or shuts off) the supply path 4. As shown in FIG. 5, the exemplary stop valve 7 includes a rotary valve body portion 7v, and can be switched by drive control of the switching cylinder 7c. That is, if the exemplified valve body portion 7v includes a valve passage 7vs formed through the diameter direction, the switching cylinder 7c is driven and controlled, and the valve body portion 7v is switched to the position of the valve body portion 7vc shown by the solid line, The valve passage 7vs is perpendicular to the supply path 4, the supply path 4 can be shut off, and the valve body portion 7v is rotatably displaced by 90 [°] to form a valve body portion 7vo shown by a virtual line. When the position is switched, the valve passage 7vs and the supply path 4 communicate with each other, and the supply path 4 can be opened. In this way, if the supply path 4 is opened and closed by the control of the stop valve 7 provided in the supply path 4, the supply path 4 can be opened and closed by the control of the stop valve 7, so that the supply path 4 can be opened and closed. It can be done quickly and reliably.

On the other hand, the pre-plastic injection molding machine M includes a molding machine controller 51 shown in FIG. 4 and a hydraulic drive unit 52 configured by a hydraulic circuit controlled by the molding machine controller 51. The hydraulic drive unit 52 is connected to the hydraulic drive cylinder 12d, the oil motor 22m, and the switching cylinder 7c shown in FIG. 5, and the hydraulic drive unit 52 is connected to the molding machine controller 51. Further, the plunger position sensor 54 and the motor rotation sensor 55 are connected to the input port of the molding machine controller 51. Further, the molding machine controller 51 has a built-in sequence control program, and can carry out the molding method according to the present embodiment described later. That is, a control command can be given to the hydraulic drive unit 52 according to the sequence control program, and the hydraulic drive cylinder 12d, the oil motor 22m, and the switching cylinder 7c shown in FIG. 5 can be sequence-controlled.

Next, the molding method of the pre-plastic injection molding machine M according to the present embodiment will be described according to the flowchart shown in FIGS. 1 to 3 with reference to FIGS. 4-FIG. 8. Note that, in FIGS. 6-8, C indicates a mold C composed of a fixed mold Cc and a movable mold Cm.

First, the initial plasticization step is executed (step S1). The detailed processing procedure of the initial plasticization step is shown in FIG. 2 by a flowchart. When executing the initial plasticization step, first, the supply path 4 is opened in the open state by switching the stop valve 7 to the open side (position shown in FIG. 8) (step S1-1). Then, the thermoplastic drive unit 22 of the thermoplastic device Mp is driven and controlled, and the screw 2 is rotationally controlled by a preset positive rotation speed (rotation speed) (step S1-2). As a result, the molding material (pellet material) in the hopper 21h is charged into the heating cylinder 21, is plastically melted by the screw 2, and the molten resin (molten resin) R is supplied from the front end of the heating cylinder 21 to the supply path. It is supplied to the injection device Mi through 4 (step S1-3).

As a result, the molten resin R is gradually accumulated in the injection cylinder 11 in front of the plunger 3, and the plunger 3 moves backward with this accumulation (step S1-4). FIG. 8 shows the position of the plunger 3 that has moved backward. When the plunger 3 moves backward and reaches a preset target position (weighing position), control is performed to stop the rotation of the screw 2 (steps S1-5 and S1-6). The arrival of the target position can be detected by the plunger position sensor 54. The above is the initial plasticization step in step S1.

When the initial plasticization step (step S1) is completed, the mold clamping device (not shown) is driven and controlled, and the mold C is clamped by the mold clamping force set in advance with respect to the mold C shown in FIG. Is executed (step S2). Then, at the end of the mold clamping step, the stop valve 7 is switched to the closed side (position shown in FIG. 6) to shut off the supply path 4 (step S3). After that, the injection drive unit 12 of the injection device Mi is driven and controlled, and an injection step of moving the screw 2 forward at a preset injection speed is executed (step S4). As a result, the molten resin R accumulated in front of the plunger 3 flows in the direction of the dotted arrow Fc shown in FIG. 6 and is injected from the injection nozzle 5 to fill the cavity of the mold C. When the plunger 3 reaches the injection end position set in advance, the injection process is completed and the process proceeds to the pressure holding process (step S5).

In the pressure holding step, it is necessary to apply a preset holding pressure to the molten resin R filled in the mold C. Therefore, as described above, a predetermined amount is in front of the plunger 3 even at the injection end position. The molten resin R of the above remains as the residual resin Rr. FIG. 6 shows a state at the time when the injection process is completed. After shifting to the pressure holding step, cooling starts (step S6) and the resin R in the mold C is cured. Therefore, when the set time Tr has elapsed, the resin reflux step is executed (step S7). In this case, the set time Tr can be set to a time length in which the resin R is cured to some extent from the time when the injection is started and the molded product Gm is not affected even if pressure is applied from the injection device Mi side.

The detailed processing procedure of the resin reflux step is shown in FIG. 3 by a flowchart. In this resin reflux step, first, the stop valve 7 is switched to the open side (position shown in FIG. 7) to open the supply path 4 (step S7-1). In the example, in the resin reflux step, a first mode in which the screw 2 is stopped and executed and a second mode in which the screw 2 is rotated in the reverse direction can be selected (step S7-2).

In the first mode, the screw 2 is stopped and the injection drive unit 12 in the injection device Mi is driven and controlled to advance the screw 2 at a preset moving speed (steps S7-2 and S7-4). .. In this case, since the resin R on the mold C side is in a cured state, the residual resin Rr existing in front of the plunger 3 flows in the direction of the dotted arrow Fr shown in FIG. 7, and is passed through the supply path 4 to the plasticizer Mp. Backflow to the side. That is, it is refluxed to the inside of the heating cylinder 21. As described above, when the resin recirculation step is performed, if the first mode in which the screw 2 is stopped and executed when the plunger 3 is moved forward is used, the resin R can be recirculated only by the forward operation of the plunger 3. It is possible to facilitate the implementation including the control process.

On the other hand, in the second mode, the forward control of the plunger 3 and the reverse rotation control of the screw 2 are performed at the same time. That is, the screw 2 is rotated in the reverse direction at the preset reverse rotation speed (steps S7-2 and S7-3), and at the same time, the plunger 3 is advanced at the preset movement speed (step S7-4). As described above, when the resin recirculation step is performed, if the second mode in which the screw 2 is rotated in the reverse direction when the plunger 3 is moved forward is used, the pressure on the plasticizer Mp side can be reduced, so that the recirculation can be performed. The treatment can be performed quickly, and the reflux time and the amount of reflux can be easily adjusted by variably controlling the rotation speed.

The first mode or the second mode in which such a resin reflux step is performed can be selected by a predetermined switching means. Therefore, the operator can select the optimum mode according to the amount of recirculation, the type of molding material, and the like.

Then, when the preset forward set time for the plunger 3 to reach the maximum forward position Xs has elapsed, the forward movement of the plunger 3 is stopped (steps S7-5 and S7-6), and in the case of the second mode, the plunger 3 is stopped. At the same time, the reverse rotation control of the screw 2 is stopped (step S7-7). FIG. 7 shows the state of the plunger 3 at the most advanced position Xs. In this case, almost the entire amount of the residual resin Rr is returned to the plasticizing device Mp side, and the residual resin Rr staying on the injection device Mi side becomes almost zero. It is desirable to set the most forward position Xs to a forward limit position that cannot be physically advanced any further, but it does not exclude a position other than the forward limit position set in advance by the operator or the like.

When the resin reflux step (step S7) is completed, the plasticization step is executed (step S8). In the plasticization step, the plasticization drive unit 22 is driven and controlled, and the screw 2 is rotationally controlled by a preset positive rotation speed (rotational speed). As a result, the molding material in the hopper 21h is charged into the heating cylinder 21, is plastically melted by the rotation of the screw 2, and at the same time, a mixing process with the residual resin Rr recirculated from the injection device Mi side is performed. .. That is, since the plasticization treatment is performed in a state where the new resin R from the hopper 21h side and the refluxed residual resin Rr are mixed, the residual resin Rr is particularly replasticized. Then, the plasticized molten resin R flows out from the front end of the heating cylinder 21 and flows in the direction of the dotted arrow Fi shown in FIG. 8 and is supplied to the injection device Mi through the supply path 4.

As described above, in the molding method according to the present invention, unlike the general plasticization step, the plasticization step includes the residual resin Rr, and is, so to speak, the plasticization step including the mixing step. Therefore, in the plasticization step, the injection drive unit 12 is driven and controlled, and the back pressure of the plunger 3 is variably set to an appropriate size. That is, if the back pressure is set large, the supply speed of the resin R supplied to the injection device Mi through the supply path 4 can be slowed down, and if the back pressure is set low, the supply speed of the resin R can be increased. It is desirable to set an appropriate back pressure according to the amount of recirculation of Rr, the type of molding material, and the like. As a result, an appropriate mixing treatment of the new resin R and the refluxed residual resin Rr can be realized, a more homogeneous plasticization treatment can be realized, and a higher quality molded product can be obtained.

Then, the molten resin R supplied from the heating cylinder 21 is gradually accumulated in the injection cylinder 11 in front of the plunger 3, so that the plunger 3 moves backward with this accumulation. FIG. 8 shows the position of the plunger 3 that has moved backward. When the plunger 3 moves backward and reaches a preset target position (weighing position), control is performed to stop the rotation of the screw 2. Therefore, this plasticizing step is basically the same as the operation of the initial plasticizing step described above, except that the residual resin Rr and the normal resin R are mixed.

On the other hand, since the mold C is cooled, the cooling is terminated when the preset cooling time has elapsed (step S9), and then the molded product taking-out step is performed (step S10). That is, the movable mold Cm is moved in the mold opening direction to open the mold, and the molded product Gm is taken out from the mold C. Then, when there is the next molding (production), the mold C is molded by the mold clamping step (steps S11 and S2). FIG. 8 shows this state. When the mold clamping step is completed, the stop valve 7 is switched to the closed side, and thereafter, the same processing can be performed according to the processing procedure described above (steps S3, S4 ...).

As described above, according to the molding method of the pre-plastic injection molding machine M according to the present embodiment, as a basic method, the molded material charged by rotating the screw 2 built in the plasticizing device Mp is plasticized. In addition, a plasticization step (step S8) in which the plasticized resin R is supplied to the injection device Mi through the supply path 4, and after this plasticization step (step S8), the supply path 4 is closed and the plunger built in the injection device Mi is closed. It is provided with at least an injection step (step S4) of injecting and filling the resin R supplied by advancing 3 into the mold C from the injection nozzle 5, and in particular, filling the mold C by the injection step (step S4). The supply path 4 is opened at a predetermined timing after the start of cooling of the resin R (step S6), and the resin Rr remaining in front of the plunger 3 is removed from the supply path 4 by advancing the plunger 3 to the most advanced position Xs. Since the resin recirculation step (step S7) of backflowing and recirculating to the plasticizing device Mp is provided, the resin Rr remaining in front of the plunger 3 is recirculated to the plasticizing device Mp in each molding cycle. As a result, the resin Rr that stays in the injection cylinder 11 is eliminated, and the problem that remains for a long time can be solved.

As a result, it is possible to prevent the resin Rr deteriorated due to the residue from being mixed into the molded product Gm, further improve the quality of the molded product Gm, and reduce the variation in the quality of the molded product Gm. In addition, it is possible to reduce the work man-hours and labor during production, such as reducing the maintenance for cleaning the inside of the injection cylinder 11, and further to improve the production efficiency (production efficiency) associated therewith. Waste of resin (resources) can be reduced.

Moreover, the residual resin Rr can be refluxed to the plasticizing device Mp and mixed with the resin R in the plasticizing device Mp so that the plasticizing treatment can be performed again, so that a molten resin R having more homogeneity can be obtained. This makes it possible to further increase the yield rate of the final molded product by reducing the number of defective products. This makes it possible to improve production efficiency and reduce production costs, especially in the production of large molded products and special resin molded products. From this point of view, it is possible to avoid resource loss and waste of energy consumption. Can also contribute effectively.

Although the preferred embodiment has been described in detail above, the present invention is not limited to such an embodiment, and the present invention does not deviate from the gist of the present invention in terms of detailed configuration, shape, material, quantity, numerical value, and the like. It can be changed, added, or deleted arbitrarily within the range.

For example, the case where the supply path 4 is opened and closed by the stop valve 7 provided in the supply path 4 is shown, but if the supply path 4 has a function of selectively opening or shutting off, various means or methods can be used. Available. Further, it is configured as an in-line injection molding machine by adding an advancing / retreating movement function to the screw 2 of the plasticizing device Mp. For example, when the plasticizing step after the resin recirculation step is performed, the stop valve 7 is closed. Various modified embodiments are possible, such as performing a mixing step of rotating the screw 2.

Further, in the embodiment, a general molding method is exemplified as the base molding method, but in addition, the molding method already proposed by the applicant, that is, at least with the solidification of the resin in the mold C, the resin is used. Using a mold clamping device that enables natural compression, a predetermined mold gap is created between the movable mold Cm and the fixed mold Cc in advance during injection filling, and the molding injection pressure that can be molded into a good product and the molding mold that can be molded into a good product can be molded. The molding method already proposed by the applicant (international), in which a force is obtained and set, and at the time of molding, the mold clamping force is used to mold the mold clamping device, and the molding injection pressure is set as the limiter pressure for molding. A molding method based on (see Publication No. WO2011 / 161899, etc.) is also possible.

The molding method according to the present invention can be used as a molding method for various pre-plastic injection molding machines in which a plasticizing device having a built-in screw and an injection device having a built-in plunger are separately configured.

2: Screw, 3: Plunger, 4: Supply path, 5: Injection nozzle, 7: Stop valve, M: Pre-plastic injection molding machine, Mp: Plasticization device, Mi: Injection device, C: Mold, R: Resin , Rr: Remaining resin (residual resin), Xs: Most advanced position of plunger, (S4): Injection step, (S6): Cooling start, (S7): Resin recirculation step, (S8): Plasticization step

Claims (5)

A plasticizing step of plasticizing the molded material charged by rotating the screw built in the plasticizing device and supplying the plasticized resin to the injection device through the supply path, and after this plasticizing step, the supply path is It is a molding method of a pre-plastic injection molding machine including at least an injection step of closing and injecting and filling the resin supplied by advancing the plunger built in the injection device from an injection nozzle into a mold, according to the injection step. The supply path is opened at a predetermined timing after the start of cooling of the resin filled in the mold, and the plunger is advanced to the most advanced position so that the resin remaining in front of the plunger flows back through the supply path. A method for molding a pre-plastic injection molding machine, which comprises providing a resin recirculation step for recirculating the plasticizing device. The molding method for a pre-plastic injection molding machine according to claim 1, wherein the resin reflux step includes a first mode in which the screw is stopped and executed when the plunger is moved forward. The molding method for a pre-plastic injection molding machine according to claim 1, wherein the resin reflux step includes a second mode in which the screw is rotated in the reverse direction when the plunger is moved forward. The molding method for a pre-plastic injection molding machine according to claim 2 or 3, wherein the resin reflux step can switch between the first mode and the second mode by a selection means. The pre-plastic injection molding machine according to any one of claims 1 to 4, wherein the plasticizing step is performed after the resin refluxing step, and the back pressure of the plunger in the plasticizing step can be variably set. Molding method.

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