JP4889574B2 - Control method of injection molding machine - Google Patents

Description

  The present invention relates to a method for controlling an injection molding machine, and more particularly to a method for controlling the injection pressure of the resin.

Conventional control methods for injection molding machines are disclosed in, for example, Patent Documents 1 to 3 and the like.
In Patent Document 1, optimum molding condition data when the mold temperature takes a plurality of different values, for example, data such as holding pressure, injection speed, cooling time, etc. are obtained in advance and stored. Based on this data, making a regression equation for the mold temperature etc. for each molding condition such as holding pressure, injection speed, cooling time, etc., while measuring the mold temperature, based on this measured mold temperature, A control method of an injection molding machine is disclosed in which a holding pressure, an injection speed, and a cooling time are calculated from a regression equation, and control is performed so that the calculated values are obtained.

  Patent Document 2 discloses a control method for an injection molding machine that switches a molding condition that enables good molding with respect to a cyclically changing environmental condition along a time course of one cycle (for example, one day). It is disclosed. Note that the conditions are gradually changed linearly.

  Patent Document 3 discloses a molded product non-defective product determination method for determining whether a molded product is good or not based on a resin pressure and a shot output received by a screw or a plunger during an injection process or a movement amount of a plunger during a pressure holding process. It is disclosed.

As shown in FIG. 2 of Patent Document 3, the molding process of the injection molding machine is composed of an injection process and a pressure holding process, and generally the resin injection pressure is constant in the pressure holding process. Controlled.
JP-A-62-249722 JP-A-1-288418 JP-A-4-173316

  However, if the control method disclosed in Patent Document 1 is to be performed, a large amount of data must be input in order to obtain a good regression equation. In order to actually collect these data, Actually molding in various environmental conditions, it is necessary to collect a great variety of data, and the mold temperature is different depending on the measurement location and the shape of the mold. It is often difficult to obtain a regression equation. Further, it is difficult to determine which part should be used as a reference for the mold temperature as a parameter, and it is difficult to accurately measure the temperature of the mold in the vicinity of the cavity.

  Further, the control method as disclosed in Patent Document 2 employs a method of switching along a period of time (for example, one day) with respect to periodically changing environmental conditions. There is a disadvantage that it cannot cope with a rapid change at the start of molding. That is, since the periodic environmental change is not always constant, if there is a non-periodic variation, a molding defect is caused.

  Further, in Patent Document 3, it is possible to determine whether a molded product is good or bad, but it is not possible to control so as to mold well. In addition, in hoop molding or the like that can form a composite part of metal (hoop material) and resin in one step, it is difficult to automatically detect defective products, and it takes a lot of time and labor for humans to determine There was also a problem.

  That is, the techniques according to Patent Documents 1 to 3 have a problem that it is difficult to mold with high quality under a short-term large environmental change at the start of molding or a long-term small environmental change.

  For example, at the start of molding of an injection molding machine, due to temporary troubles, the injection molding machine is temporarily stopped (so-called chocolate stop), and the current state is restored by simple measures to perform molding work. May be resumed. In this way, if the plasticized resin stays in the injection molding machine and temporarily stopped before the start of molding, the resin is melted. Therefore, as shown in FIG. The resin temperature increases, which decreases the resin viscosity with a decrease in pressure loss. Therefore, under such circumstances, as shown in FIG. 8 (a), the resin is excessively injected into the mold at the start of molding, and the product weight becomes excessive in several shots after the start of molding. Good products are likely to be generated.

  In addition, in an injection molding machine, a purge operation for purifying the resin may be performed before the start of molding. In this case, at the start of molding, the resin introduced into the injection molding machine is renewed, and a lot of heat is taken away from the plasticization of the resin. As a result, as shown in FIG. 7 (b), the resin temperature in the cylinder becomes low at the start of molding, which is accompanied by an increase in pressure loss due to an increase in resin viscosity. Therefore, under such a situation, as shown in FIG. 8 (b), the injection of resin into the mold at the start of molding is insufficient, and the thickness of the product is reduced in several shots after the start of molding. It becomes easy to generate the trouble that it becomes few or the defective product which resin is not inject | poured into the regular place generate | occur | produces.

  In addition, if the injection molding machine is used for a long time, various pressure loss changes such as resin viscosity, mold temperature, gate wear, etc. occur, and pressure correction corresponding to this pressure loss change is performed. Otherwise, defective products with excessive product weight or defective products in which resin is not injected into regular locations are likely to occur.

  The present invention solves the above-mentioned drawbacks and problems, enables pressure correction corresponding to changes in the molding environment, and achieves high quality even under large short-term environmental changes at the start of molding and small long-term environmental changes. An object of the present invention is to provide a method for controlling an injection molding machine that can be molded.

To overcome the above drawbacks and problems, the present invention, the resin is plasticized, a control method of an injection molding machine for injecting the plasticized resin with the screw or plunger into the mold, to the injection molding machine The plastic is pre-plasticized by the pre-plasticizer provided, the pressure loss is measured by the pressure detector provided in the injection molding machine, and the resin is kept for a certain number of shots from the start of molding according to the change in pressure loss. Molding is performed while correction control is performed so that the injection pressure becomes a value obtained by adding the pressure correction value ΔP to the reference pressure value P, and N is the number of shots until at least one of the resin viscosity and the mold temperature is stabilized. When the pressure correction value of the shot is ΔP0, the pressure correction value ΔP when the number of shots is n is ΔP = (1− (n−1) / N) ^ k · ΔP0 (k is an approximate expression) The order of While characterized by molding. The preliminary plasticizing device preferably includes a hopper, a screw, and a screw housing. The pressure detector is preferably a load cell.

By this method, when the pressure loss changes due to changes in the molding environment such as resin viscosity and mold temperature fluctuation, pressure correction corresponding to the pressure loss is possible. This method also reduces the injection pressure of the resin in response to pressure loss caused by a short-term large molding environment change, such as resin viscosity and mold temperature fluctuation, which occurs during a fixed number of shots from the start of molding. It can be adjusted and can be molded with high quality. In addition, this method makes it possible to perform high-quality molding in a favorable manner corresponding to fluctuations in resin viscosity and mold temperature at the start of molding.

  As described above, according to the present invention, molding is performed while correcting and controlling so that the injection pressure of the resin becomes a value obtained by adding the pressure correction value ΔP to the reference pressure value P in accordance with the change in pressure loss. When the pressure loss changes due to changes in the molding environment such as resin viscosity and mold temperature fluctuation, pressure correction corresponding to the pressure loss is possible.

  Further, during the constant number of shots from the start of molding, by molding while controlling the resin injection pressure to be a value obtained by adding the pressure correction value ΔP to the reference pressure value P, between the constant number of shots from the start of molding. The injection pressure of the resin can be adjusted in response to pressure loss caused by large changes in the molding environment such as the viscosity of the resin and fluctuations in the mold temperature. It is possible to always apply an appropriate pressure to the product part (cavity) of the mold, and it is possible to form a good product from the first shot, eliminate unnecessary processes such as defective discharge, and hoop molding. It is also possible to omit the inspection after the molding process.

  Further, when the number of shots until at least one of the resin viscosity and the mold temperature is stabilized is N, and the pressure correction value for the first shot is ΔP0, the pressure correction value ΔP when the number of shots is n is , ΔP = (1− (n−1) / N) ^ k · ΔP0 (k is the order of the approximate expression), so that the viscosity of the resin and the mold temperature at the start of molding are controlled. It is possible to mold with high quality in response to the fluctuations.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall cross-sectional view schematically showing an injection molding machine and a mold for carrying out an injection molding machine control method according to an embodiment of the present invention.

  As shown in FIG. 1, the injection molding machine is of a screw / prepa type, and includes an injection device 100 and a preliminary plasticizing device 200 that supplies a plasticized molding material to the injection device 100. The plasticized molding material is injected into the cavity 301 of the mold 300. The injection molding machine is not limited to the screw / prepa type.

  The injection device 100 is driven by a cylinder 1 having an injection port 11 at the tip and driving means 3 and slides in the axial direction of the cylinder 1 on the base side (inside the main body) from the injection port 11 inside the cylinder 1. And a driving means 3 for moving the plunger 2 in the axial direction (raising and lowering in FIG. 1). A supply port 12 to which the plasticized molding material from the preliminary plasticizing apparatus 200 is supplied is provided in the middle of the sliding position of the plunger 2 in the cylinder 1.

  The driving means 3 includes a plurality of slide guide shafts 31 extending upward along the axial direction from the base end portion of the cylinder 1, a support base 32 attached to the other end of the slide guide shaft 31, and the support base 32. The drive motor 33 installed on the screw shaft 34, one end of the screw shaft 34 coupled to the drive motor 33 and rotating, and the screw shaft 34 meshes with the threaded portion and moves along the slide guide shaft 31 by forward and reverse rotation of the screw shaft 34. And a moving member 35. One end of the moving member 35 is connected to the upper end of the plunger 2 via a load cell 36 as a pressure detector, and the driving force is transmitted to the plunger 2 to move the plunger 2. The load cell 36 functions as a pressure detector for detecting the injection pressure (pressure loss of the injection cylinder 1) received from the resin (resin pellet) side of the injection cylinder 1 of the plunger 2. The drive motor 33 is attached with an encoder 37 as a position detector that detects the position of the plunger 2 based on the rotation speed and rotation angle of the screw shaft 34. Instead of providing the encoder 37, a proximal end portion or a distal end portion of the plunger 2 or a position sensor for detecting the position of the moving member 35 may be provided. Reference numeral 5 denotes a control unit that performs drive control of the drive motor 33 and a control operation that will be described later. Reference numeral 4 denotes a backflow prevention valve that prevents the resin melt as a molding material from flowing back to the supply port 12. The driving means 3 is not limited to the above configuration, and any configuration may be used as long as the plunger 2 can be moved and controlled to a predetermined position and the resin injection pressure acting on the plunger 2 and the position of the plunger 2 can be recognized. .

  The preliminary plasticizing apparatus 200 includes a hopper 201, a screw 202, and a screw housing 203, and granular resin (resin pellets) as a molding material stored in the hopper 201 is plasticized in the screw housing 203 by the screw 201. The plasticized plastic is sent into the cylinder 1 through the supply port 12 of the cylinder 1.

  Although not shown, the screw housing 203 and the cylinder 1 are each provided with a heating device (for example, a panel heater) or the like, and are heated to a predetermined temperature at the time of molding.

  In the above configuration, the plasticized resin is supplied from the preliminary plasticizing apparatus 200 into the cylinder 1 through the supply port 12, and the plunger 2 is inserted into the injection port 11 in a state where the plasticized resin is filled in the cylinder 1. By moving to the side (lowering in this embodiment), one shot of plasticized molding material (resin) is injected and injected into the cavity 301 of the mold 300. Thereafter, the injection pressure is held by the plunger 2 until the resin in the cavity 301 of the mold 300 is cured. When the resin is cured, the mold 300 is released, the molded product in the cavity 301 is taken out, the mold 300 is assembled again, the plunger 2 is moved and held, and the injection process and the holding process are performed. By repeating the above, the molding operation is repeated.

  In particular, in this embodiment of the present invention, detection of the injection pressure of the resin is started by the load cell 36 as a pressure detector from the start of molding, and as shown in FIG. 2, it responds to changes in the molding environment (molding situation). The injection pressure of the resin is set to a reference pressure value P that is a resin injection pressure value in a reference state (for example, a state in which the temperature of the mold 300 and the cylinder 1 is stable during continuous molding) for a certain number of shots. It shape | molds, controlling by the control part 5 so that it may become the value which added pressure correction value (DELTA) P. In this embodiment, the pressure is corrected only in the injection process between the start of molding and a fixed number of shots.

  Further, as the correction amount, when the number of shots until the viscosity of the resin is stabilized is N and the pressure correction value of the first shot is ΔP0, the pressure correction value ΔP when the number of shots is n is ΔP = (1− (n−1) / N) ^ k · ΔP0 (k is the order of the approximate expression, and molding is performed while controlling so as to be a value of 1 or more, for example, 2 (therefore, the viscosity of the resin is If the number of shots n is stable and N + 1 or more, ΔP is not added).

  When the plasticized resin stays in the cylinder 1 and there is a stop time of t seconds before the start of molding, the standing time for stabilizing the resin viscosity is T, and the pressure correction standard When the value is ΔPt, the pressure correction value ΔP0 for the first shot is set to ΔP0 = − (t / T) ^ k · ΔPt (see the one-dot chain line portion in FIG. 2).

  In addition, when a purge operation for purifying the resin before the start of molding is performed, when the stop time before the start of molding is t seconds and the pressure correction reference value by purge is ΔPp, the pressure of the first shot The correction value ΔP0 is set to ΔP0 = ΔRp− (t / T) ^ k · ΔPt (see the dotted line portion in FIG. 2).

  In the above configuration, there is a stop time of t seconds before the start of molding in a state where the plasticized resin stays, and the stop time t before the start of molding is longer than the standing time T for stabilizing the viscosity of the resin. In this case, since the melting of the resin proceeds, as shown in FIG. 7 (a), the resin temperature increases corresponding to the stop time t, which is accompanied by a decrease in pressure loss due to a decrease in resin viscosity. Therefore, if the injection pressure of the resin remains at the reference pressure value P, as shown in FIG. 8A, the resin is excessively injected into the mold 300 at the start of molding, resulting in an excessive product weight. It becomes easy to generate defective products.

  On the other hand, according to the above method, when the plasticized resin stays in the cylinder 1 and there is a stop time of t seconds before the start of molding, it corresponds to the stop time t. Then, the injection pressure of the resin is adjusted by the pressure correction value ΔP = (1− (n−1) / N) ^ k · ΔP0, and in the first shot, the pressure correction value ΔP0 = (t / T) ^ It is lowered by k · ΔPt (refer to the chain line portion in FIG. 2). As a result, the resin is suppressed from being excessively injected into the mold 300 at the start of molding, and the resin is successfully injected into the mold 300. As shown in FIG. A molded product can be formed. Therefore, good products can be formed from the first shot, and it is not necessary to perform a process such as defective discharge.

  Further, in the above configuration, when a purging operation for purifying the resin is performed before the molding starts, the resin introduced into the cylinder 1 is renewed at the time of the molding start. Since the heat is taken away, the temperature of the cylinder 1 is lowered. Accordingly, as shown in FIG. 7 (b), the resin temperature is lowered corresponding to the stop time t before the start of molding, which is accompanied by an increase in pressure loss due to an increase in resin viscosity. Therefore, if the injection pressure of the resin remains at the reference pressure value P, as shown in FIG. 8 (b), the injection of the resin into the mold 300 at the start of molding is insufficient, and the resin is placed in a proper place. It becomes easy to generate defective products that are not injected.

  On the other hand, according to the above method, when a purging operation for purifying the resin before the start of molding is performed, the injection pressure of the resin corresponds to the stop time t before the start of molding at this time. The pressure correction value ΔP = (1− (n−1) / N) ^ k · ΔP0 is adjusted, and in the first shot, the pressure correction value ΔP0 = ΔRp− (t / T) ^ k · ΔPt is increased. (See the dotted line in FIG. 2). When the purge operation is performed, the resin temperature decreases at the start of molding. However, if there is a sufficient elapsed time (stop time t) until the molding starts thereafter, the resin is melted. Since the resin temperature rises, the correction equation is set in consideration of this phenomenon.

  By performing the above correction, it is possible to prevent the resin from being insufficiently injected into the mold 300 at the start of molding, and the resin is satisfactorily injected into the mold 300. ) Can be formed. Therefore, good products can be formed from the first shot, and it is not necessary to perform a process such as defective discharge.

  In any case, the absolute value of the pressure correction value ΔP decreases as the number of shots n (where n ≦ N) increases. However, by setting the order k of the approximate expression to 1, the number of shots depends on the number of shots. The pressure value to be corrected is proportionally reduced, and the pressure value to be lowered is rapidly reduced only at the first shot such as the second shot by setting a large number as the order k of the approximate expression. Therefore, this order may be set in accordance with the heat volume of the cylinder 1 or the like.

  In the above embodiment, the case where the number of shots until the viscosity of the resin is stabilized is described as N. However, the present invention is not limited to this, and the number of shots until the mold temperature is stabilized may be used. Further, the number of shots until both the viscosity of the resin and the mold temperature are stabilized may be used.

That is, as shown in FIGS. 7A and 7B, at the start of molding, the temperature of the mold 300 is low, and a relatively long time is required for the mold 300 to reach an appropriate temperature. A time longer than the time required for the resin temperature to reach an appropriate temperature is required. Therefore, when considering the environment until both the viscosity of the resin and the mold temperature are stabilized, control is performed as follows. When the number of shots until the mold temperature is stabilized is N ′ and the pressure correction value for the first shot mold 300 is ΔPk (where N ′> N), the number of shots n after the start of molding is n. Is less than the number of shots N until the viscosity of the resin is stabilized,
ΔP = (1− (n−1) / N) ^ k · ΔP0 + (1− (n−1) / N ′) ^ k ′ · ΔPk (k ′ is the order of the approximate expression) Mold.

Further, when the number of shots n after the start of molding is larger than the number of shots N until the viscosity of the resin is stabilized and is equal to or less than the number of shots N ′ until the mold temperature is stabilized,
ΔP = (1− (n−1) / N ′) ^ k ′ · ΔPk (k ′ is the order of the approximate expression)
It shape | molds, controlling so that it may become. When the viscosity of the resin and the mold temperature are stable but the shot number n is N + 1 or more, the pressure correction value ΔP is not added. Further, the pressure correction value ΔPk related to the first shot mold 300 is set in the same manner as in the case of the pressure correction value ΔP0.

  As a result, an even better molded product can be formed immediately after the start of molding, and a non-defective product can be molded from the first shot. When considering only the mold temperature stability, the pressure correction value ΔP = (1− (n−1) / N ′) when the number of shots is N ′ or less until the mold temperature is stabilized. Correction control may be performed as ^ k ′ · ΔPk.

  Next, FIG. 4 shows a control method according to another embodiment of the present invention. In this embodiment, the injection pressure of the resin in the pressure holding process in accordance with the change in the pressure loss in the injection process. However, it shape | molds, carrying out correction | amendment control so that it may become the value which added pressure correction value (DELTA) P to the reference pressure value P. FIG.

  Specifically, in the injection process of injecting the resin into the mold 300, the detection time is reached in a state where the viscosity of the resin and the mold temperature are stable after a process of several tens of shots has passed since the start of molding. Time t1 is set, and as shown in FIG. 5 (a), the reference injection pressure P10 at the time t1 at the time of standard molding (when the molding state is stable) is measured in advance by the load cell 36. As shown in FIG. 5B, the pressure correction value ΔP, which is stored in the memory and is added to the reference pressure value Pp of the resin injection pressure in the pressure-holding process, is calculated as ΔP. = K1 · (P1−P10) (k1 is an arbitrary positive coefficient), and the pressure Ps in the pressure-holding process is controlled by adding the pressure correction value ΔP to the reference pressure value Pp and performing molding. .

  Thus, when the actual injection pressure P1 in the injection process is larger than the reference injection pressure P10 based on the correction formula, the injection pressure of the resin in the pressure holding process is also increased, and the actual injection pressure P1 in the injection process is When it is smaller than the reference injection pressure P10, the injection pressure of the resin in the pressure holding process is also reduced. As a result, even if the injection molding machine has been used for a long time and various pressure loss changes such as resin viscosity, mold temperature, and wear of the gate portion occur, the cavity of the mold 300 during holding is maintained. The resin can be injected well into 301, the density of the resin can be stabilized, the generation of defective products can be prevented, and high-quality molding can be performed.

  That is, when the actual injection pressure P1 in the injection process is larger than the reference injection pressure P10 and the difference between the pressure of the plunger 2 and the actual pressure of the cavity 301 is large (that is, the pressure loss is large), the pressure loss is higher than the present. If the pressure holding state is the same as that at a small reference time, the density of the resin injected into the cavity 301 of the mold 300 becomes low, and the molded product shrinks more than expected at the time of pressure holding (during cooling). Although it may become defective, it can prevent that such a malfunction arises by controlling as mentioned above.

  As a result, pressure correction corresponding to any change in the molding environment is possible, so that high-quality molding is possible even under a short-term large environmental change at the start of molding or a long-term small environmental change.

  In the above-described embodiment, the reference injection pressure P10 when the predetermined time t1 has elapsed from the start of molding is stored and the actual injection pressure P1 is measured. The reference injection pressure P10 at the time of molding as a reference when the nozzle passes the predetermined position X1 (see FIG. 1) is measured and stored in advance, and the actual injection at the time of passing through the predetermined position X1 at the time of actual molding In the same manner as described above, the pressure correction value ΔP to be added to the reference pressure value P of the resin injection pressure in the pressure holding process is ΔP = k1 · (P1−P10) (k1 is an arbitrary positive coefficient). Even if it shape | molds, controlling so that it may become, the same effect can be acquired.

  Here, the position X1 of the plunger 2 at the time of detecting the pressure is, for example, the origin X0 (see FIG. 1) as the origin X0 (refer to FIG. 1) when the plunger 2 is not retracted (initial position). It is calculated from the detection position of the encoder 37 that the position X1 has been protruded (advanced) by a predetermined distance from X0 (moved downward in FIG. 1) and reached the position X1. The position X1 at this time is a state in which the viscosity of the resin and the mold temperature are stable after a process of several tens of shots has passed in advance from the start of molding in the injection process of injecting the resin into the mold 300. It is desirable to set the detection position.

  As a further alternative, as shown in FIG. 6, a reference injection pressure at the time of molding as a reference is measured in advance during a predetermined time t1 to Δt seconds in the injection process of injecting the resin into the mold 300. Then, the reference injection average value Pv is stored, the injection pressure at the time of actual molding is measured, the actual injection average value Pj is calculated, and the pressure correction value to be added to the reference pressure value P of the resin injection pressure in the pressure holding process You may shape | mold, controlling (DELTA) P to become (DELTA) P = k1 * (Pj-Pv) (k1 is an arbitrary coefficient).

  Also with this method, it is possible to satisfactorily correct the injection pressure of the resin in the pressure holding process in accordance with the change in the pressure loss in the injection process, and in particular, the correction is made based on the actual injection average value Pj. Adverse effects such as detection errors of pressure measurement values can be minimized.

  In place of this, in the injection step of injecting resin into the cavity 301 in the mold 300, the reference at the time of molding which becomes the reference while the plunger 2 moves by the predetermined distance ΔX after passing through the predetermined position X1. The injection pressure is measured in advance, the reference injection average value Pv is stored, the injection pressure at the time of actual molding is measured, and the actual injection average value Pj is calculated. Molding may be performed while controlling the pressure correction value ΔP to be added to the reference pressure value P to be ΔP = k1 · (Pj−Pv) (k1 is an arbitrary positive coefficient), and the same effect can be obtained. Can do.

  In the above-described embodiment, the case of an injection molding machine in which a plasticized resin is injected into the mold 300 with the plunger 2 is described. However, the present invention is not limited to this. The present invention can also be applied to an injection molding machine for injecting into a mold (except for the case of controlling by the position of the plunger 2).

  The control method for an injection molding machine of the present invention can be used for a sealing molding machine for a semiconductor or the like using a thermosetting resin because the pressure command value can be corrected in response to a change in pressure loss during injection.

FIG. 1 is an overall cross-sectional view schematically showing an injection molding machine and a mold for carrying out a method for controlling an injection molding machine according to an embodiment of the present invention. The figure which shows the relationship between the injection pressure which concerns on the control method of the injection molding machine of embodiment of this invention, and time. The figure which shows the product weight at the time of implementing the control method of the injection molding machine which concerns on embodiment of this invention The figure which shows the relationship between the injection pressure which concerns on the control method of the injection molding machine of other embodiment of this invention, and time. (A) and (b) are flowcharts schematically showing a reference pressure value storing step and an actual molding operation according to the control method of the injection molding machine. The figure which shows the relationship between the injection pressure which concerns on the control method of the injection molding machine of other embodiment of this invention, and time. (A) is the figure which shows simply the resin temperature and metal mold | die temperature of the state which stopped the equipment of the injection molding machine temporarily, and resin remained, (b) is the state after performing a purge operation | work Of resin temperature and mold temperature (A) is the figure which shows simply the product thickness at the time of shaping | molding after resin equipment stagnates by stopping the equipment of an injection molding machine temporarily, (b) is the case where it shape | molds after performing a purge operation | work Of product weight

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Plunger 3 Drive means 5 Control part 11 Injection port 12 Supply port 33 Drive motor 35 Moving member 36 Load cell (pressure detector)
37 Encoder (position detector)
100 Injection device 200 Preplasticizer 300 Mold 301 Cavity

Claims (3)

A method of controlling an injection molding machine that plasticizes a resin and injects the plasticized resin into a mold with a screw or a plunger, wherein the resin is pre-plasticized by a preplasticizer provided in the injection molding machine, The pressure loss is measured by the pressure detector provided in the injection molding machine, and the resin injection pressure is set to the reference pressure value P with the pressure correction value ΔP for a certain number of shots from the start of molding in response to the change in pressure loss. When molding is performed with correction control so that the added value is obtained, and the number of shots until at least one of the resin viscosity and the mold temperature is stabilized is N, and the pressure correction value for the first shot is ΔP0, the shot The pressure correction value ΔP when the number is n is shaped while being controlled so that ΔP = (1− (n−1) / N) ^ k · ΔP0 (k is the order of the approximate expression). Features injection molding machine Control method. 2. The method of controlling an injection molding machine according to claim 1, wherein the preliminary plasticizing apparatus includes a hopper, a screw, and a screw housing. The method of controlling an injection molding machine according to claim 1 or 2, wherein the pressure detector is a load cell.

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