JP5059960B2 - Mold clamping force setting method and mold clamping force setting device for injection molding machine - Google Patents

Description

  The present invention seeks an appropriate mold clamping force that does not generate burrs in accordance with a resin pressure generated when a resin is injected into a mold and does not cause deformation of the mold in an injection molding machine. The present invention relates to a mold clamping force setting method and a mold clamping force setting device.

When the molten resin is injected into the mold, if the mold clamping force is insufficient with respect to the pressure generated by the molten resin, the mold may open and cause burrs. On the other hand, when the mold clamping force is excessive, there is no concern about burrs, but there is a problem that the mold is deformed and the dimension of the molded product becomes out of specification or the life of the mold is shortened. For this reason, it is desirable that the mold clamping force is an appropriate mold clamping force that does not generate burrs and does not cause deformation of the mold.
As a technique for adjusting the mold clamping force, Patent Document 1 discloses a technique for gradually changing the mold clamping force and obtaining the minimum mold clamping force to be applied to the mold based on the detected change in the mold clamping force. ing. Patent Document 2 discloses a technique for obtaining a minimum mold clamping force from coefficients such as injection pressure, projected area, and safety factor.

JP 2008-6651 A JP-A-8-252849

  If the behavior when the molten resin is injected into the mold when the clamping force is insufficient is analyzed in detail, the behavior is as shown in FIGS. FIG. 1 is a diagram for explaining the behavior when molten resin is injected into a mold when the mold clamping force is insufficient. FIG. 2 is a graph for explaining changes in the resin pressure during injection and the detection mold clamping force in the case of FIG.

State (1): After the molds (40a, 40b) are closed and a set clamping force is generated, the molten resin 50 is injected into the cavity 42 of the mold, and the molten resin 50 is filled into the cavity 42. .
State (2): When the molten resin 50 is further injected into the molds (40a, 40b) and the resin pressure rises and a resin pressure higher than the set mold clamping force acts on the wall surface of the mold (40a, 40a, 40b) , 40b) is applied. However, since the mold is compressed in accordance with the clamping force when the clamping force is generated, the force to open the mold acts in the direction of extending the mold from the compressed state to the original thickness. So the mold will not actually open. Furthermore, since the tie bar is extended by the extension of the mold, the mold clamping force starts to rise above the set mold clamping force.
State (3): After the molds (40a, 40b) return to their original thickness, when a force to open the mold is further applied by the resin pressure, the mold starts to open, and the molten resin 50 leaks from the cavity 42 and flashes. However, at the same time, since the resin leaks from the mold, the increase in the resin pressure is suppressed, so that the mold clamping force does not increase.
In order to show the above behavior, the smaller the mold clamping force set in the state (2), the greater the increase in the mold clamping force against the resin pressure, and the maximum mold clamping force during the injection in the state (3). The value also depends on the set clamping force. FIG. 3 shows a relationship in which the maximum value of the mold clamping force during injection depends on the set mold clamping force. FIG. 3 is a graph for explaining a change in the maximum value of the detected mold clamping force when the set mold clamping force is changed.

  In the technique disclosed in Patent Document 1 described in the background art section, it is necessary to make trial and error until an allowable value (a value obtained from an allowable mold opening amount) is reached as to whether the change in the mold clamping force is large. There is a problem that an appropriate mold clamping force cannot be obtained efficiently. In the technique disclosed in Patent Document 2, it is necessary to obtain coefficients such as a projected area and a safety factor. The projected area has to be determined by analyzing the mold drawing, and the safety factor is generally an empirical value, so it is extremely difficult to determine an accurate value. Therefore, it is difficult to obtain an accurate minimum clamping force with the technique of Patent Document 2.

  Accordingly, an object of the present invention is to prevent the occurrence of burrs in accordance with the resin pressure generated when the resin is injected into the mold, and to prevent deformation of the mold in view of the above-mentioned problems of the prior art. An object of the present invention is to provide a mold clamping force setting method and a mold clamping force setting device for an injection molding machine that can obtain an appropriate mold clamping force.

In the invention according to claim 1 of the present application, the mold is closed by the mold clamping mechanism based on the set mold clamping force to generate the mold clamping force, and the molten resin is injected into the mold by the injection mechanism. Injecting by generating a mold clamping force with different mold clamping force, detecting the mold clamping force during the injection, and detecting the mold clamping force during the injection from the injection with the different mold clamping force Two or more combinations of the maximum detected mold clamping force and the set mold clamping force such that the maximum value of the detected mold clamping force is larger than the set mold clamping force are extracted, and the extracted maximum detected clamp force and the set mold clamping force are extracted. The relationship between the maximum value of the detected mold clamping force and the set mold clamping force is obtained from the combination of the above. A mold clamping force setting method for an injection molding machine, characterized in that the determined mold clamping force is set.
The invention according to claim 2 is the mold clamping force setting method for an injection molding machine according to claim 1, wherein the relational expression is obtained by applying a linear approximation.
According to a third aspect of the present invention, when there are three or more combinations of the extracted maximum value of the detected mold clamping force and the set mold clamping force, the relational expression is applied to a second-order or higher approximation formula. The mold clamping force setting method for an injection molding machine according to claim 1, wherein the mold clamping force is set.

According to a fourth aspect of the present invention, there is provided a mold clamping unit that closes a mold based on a set mold clamping force to generate a mold clamping force, an injection unit that injects a molten resin into the mold, and a melting by the injection unit. A detection unit for detecting a maximum value of the mold clamping force during the injection of the resin, a setting mold clamping force setting unit for performing injection by generating a mold clamping force with two or more different setting mold clamping forces, and the setting mold A storage unit that stores the clamping force and the maximum value of the detected mold clamping force detected during the injection in correspondence with each other, and a detection from the set mold clamping force and the detected mold clamping force stored in the storage unit. An extraction unit that extracts two or more combinations having a maximum value of the mold clamping force larger than the set mold clamping force, and a maximum detected mold clamping force from a combination of the extracted maximum value of the detected mold clamping force and the set mold clamping force. A relational expression calculation unit for obtaining a relational expression between the value and the set mold clamping force, and the maximum value of the detected mold clamping force and the set mold clamping A mold clamping force of an injection molding machine, characterized in that a mold clamping force calculated by the appropriate mold clamping force calculation unit is set. It is a setting device.
The invention according to claim 5 is the mold clamping force setting device for an injection molding machine according to claim 4, wherein the relational expression is obtained by applying linear approximation.
According to a sixth aspect of the present invention, when there are three or more combinations of the extracted maximum value of the detected mold clamping force and the set mold clamping force, the relational expression is applied with an approximation expression of second order or higher. The mold clamping force setting device for an injection molding machine according to claim 4, wherein the mold clamping force setting device is obtained by:

  According to the present invention, an injection molding capable of obtaining an appropriate mold clamping force without generating a burr according to a resin pressure generated when a resin is injected into a mold and without causing a deformation of the mold. A mold clamping force setting method and a mold clamping force setting device can be provided.

It is a figure explaining the behavior when molten resin is inject | poured in a metal mold | die when mold clamping force is insufficient. It is a graph explaining the change of the resin pressure during injection | pouring in the case of FIG. 1, and a detection clamping force. It is a graph explaining the change of the maximum value of the detection mold clamping force at the time of changing a setting mold clamping force. It is a side view of the injection molding machine which can set a mold clamping force using the mold clamping force setting method by this invention. It is a graph explaining calculating | requiring the mold clamping force that the maximum value of a detection mold clamping force and a setting mold clamping force become equal by a linear approximation formula. It is a graph explaining calculating | requiring the mold clamping force that the maximum value of a detection mold clamping force and a setting mold clamping force become equal by a quadratic approximate expression. It is a figure explaining the maximum value of the setting mold clamping force memorize | stored in memory and the detection mold clamping force during injection. It is a flowchart which shows the algorithm of the process which calculates the appropriate mold clamping force based on this invention using a linear approximation formula (the 1). It is a flowchart which shows the algorithm of the process which calculates the appropriate mold clamping force based on this invention using a linear approximation formula (the 2).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 4 is a side view of an injection molding machine capable of setting a mold clamping force using the mold clamping force setting method according to the present invention. The injection molding machine M includes a mold clamping part Mc and an injection part Mi on a machine base (not shown). The injection part Mi heats and melts a resin material (pellet), and injects the molten resin into the cavity of the mold 40. The mold clamping portion Mc mainly opens and closes the mold 40 (40a, 40b).

  First, the injection part Mi will be described. A nozzle 2 is attached to the tip of the injection cylinder 1, and a screw 3 is inserted into the injection cylinder 1. The screw 3 is provided with a resin pressure sensor 5 using a load cell or the like that detects the resin pressure by the pressure applied to the screw 3. The resin pressure sensor output signal is converted into a digital signal by the A / D converter 16 and input to the servo CPU 15.

  The screw 3 is rotated by a screw rotating servo motor M2 via a transmission mechanism 6 composed of a pulley, a belt and the like. Further, the screw 3 is driven by a screw servo motor M1 through a transmission mechanism 7 including a mechanism for converting a rotational motion such as a pulley, a belt, and a ball screw / nut mechanism into a linear motion. Moved in the direction. Reference numeral P1 is a position / speed detector that detects the position and speed of the screw 3 in the axial direction by detecting the position and speed of the servo motor M1 for moving forward and backward, and reference numeral P2 is the position of the servo motor M2. The position / speed detector detects the rotational position and speed around the axis of the screw 3 by detecting the speed. Reference numeral 4 denotes a hopper that supplies resin to the injection cylinder 1.

  Next, the mold clamping part Mc will be described. The mold clamping portion Mc includes a movable platen forward / reverse motor M3 for moving the movable platen 30 forward and backward, a rear platen 31, an ejector forward / reverse motor M4 for ejecting an ejector pin for pushing out a molded product from the mold, a movable platen 30, a tie bar 32, and a fixed plate. A platen 33, a cross head 34, an ejector mechanism 35, and a toggle mechanism 36 are provided. The rear platen 31 and the fixed platen 33 are connected by a plurality of tie bars 32, and the movable platen 30 is disposed so as to be guided by the tie bars 32. A movable mold 40 a is attached to the movable platen 30, and a fixed mold 40 b is attached to the fixed platen 33. The toggle mechanism 36 can operate the toggle mechanism 36 by advancing and retracting the cross head 34 attached to the ball screw shaft 38 driven by the movable platen forward / reverse motor M3. In this case, when the cross head 34 is moved forward (moved in the right direction in the figure), the movable platen 30 is moved forward to perform mold closing. Then, a mold clamping force is generated by multiplying the propulsive force by the propulsive force of the movable platen forward / reverse motor M3 by the toggle magnification, and the mold clamping is performed by the mold clamping force.

  A mold clamping force sensor 41 is disposed on one of the tie bars 32. The mold clamping force sensor 41 is a sensor that detects distortion (mainly elongation) of the tie bar 32. When the mold is clamped, the tie bar 32 is applied with a tensile force corresponding to the clamping force, and extends slightly in proportion to the clamping force. Therefore, the mold clamping force actually applied to the mold 40 can be known by detecting the extension amount of the tie bar 32 by the mold clamping force sensor 41. As the mold clamping force sensor 41, for example, a strain sensor can be used.

  The rear platen 31 is provided with a mold clamping position adjusting motor M5. A driving gear (not shown) is attached to the rotating shaft of the mold clamping position adjusting motor M5. A power transmission member such as a toothed belt is wound around a gear of a tie bar nut (not shown) and the driving gear. Therefore, when the mold clamping position adjusting motor M5 is driven to rotate the driving gear, the tie bar nuts screwed into the threaded portions 37 of the tie bars 32 are rotated in synchronization. Accordingly, the mold clamping position adjusting motor M5 can be rotated in a predetermined direction by a predetermined number of rotations, and the rear platen 31 can be advanced and retracted by a predetermined distance. The mold clamping position adjusting motor M5 is preferably a servomotor as shown in the figure, and includes a position detector P5 for detecting the rotational position. The detection signal of the rotational position of the mold clamping position adjusting motor M5 detected by the position detector P5 is input to the servo CPU 15.

  The control device 100 of the injection molding machine M includes a CNC CPU 20 that is a microprocessor for numerical control, a PMC CPU 17 that is a microprocessor for a programmable machine controller, and a servo CPU 15 that is a microprocessor for servo control. Thus, by selecting mutual input / output, information can be transmitted between the microprocessors.

  The servo CPU 15 is connected to a ROM 13 that stores a control program dedicated to servo control that performs processing of a position loop, a speed loop, and a current loop, and a RAM 14 that is used for temporary storage of data. The servo CPU 15 can detect pressure signals from the resin pressure sensor 5 that detects various pressures such as injection pressure provided on the injection molding machine main body side via an A / D (analog / digital) converter 16. It is connected to the. The servo CPU 15 is connected to servo amplifiers 11 and 12 for driving the injection servo motor M1 connected to the injection shaft and the screw rotation servo motor M2 connected to the screw rotation shaft based on a command from the servo CPU 15. The outputs from the position / speed detectors P1, P2 attached to the servo motors M1, M2 are fed back to the servo CPU 15. The rotational positions of the servo motors M1 and M2 are calculated by the servo CPU 15 based on the position feedback signals from the position / speed detectors P1 and P2, and updated and stored in the current position storage registers.

Servo amplifiers 8 and 9 are connected to a servo motor M3 for driving a mold clamping shaft for clamping the mold and an ejector shaft servo motor M4 for taking out a molded product from the mold, respectively.
Outputs from position / speed detectors P3 and P4 attached to the servo motors M3 and M4 are fed back to the servo CPU 15. The rotational positions of the servo motors M3 and M4 are calculated by the servo CPU 15 based on the position feedback signals from the position / speed detectors P3 and P4, and updated and stored in the current position storage registers.

A ROM 18 storing a sequence program for controlling the sequence operation of the injection molding machine and a RAM 19 used for temporary storage of calculation data are connected to the PMC CPU 17, and an automatic operation program for overall control of the injection molding machine is connected to the CNC CPU 20. A ROM 21 storing various programs such as a control program for realizing the mold clamping force setting method related to the present invention and a RAM 22 used for temporary storage of calculation data are connected. The molding data storage RAM 23 is a non-volatile memory, and is a molding data storage memory that stores molding conditions relating to injection molding work, various set values, parameters, macro variables, and the like. A display device / MDI (manual data input device) 25 is connected to a bus 26 via an interface (I / F) 24 so that a function menu can be selected and various data can be input. A numeric keypad for inputting numeric data and various function keys are provided.
The display device may be an LCD (liquid crystal display device), CRT, or other display device.

  With the above-described configuration of the injection molding machine, the PMC CPU 17 controls the entire sequence of the injection molding machine, and the CNC CPU 20 controls the servo motors for each axis based on the operating conditions of the ROM 21 and the molding conditions stored in the molding data storage RAM 23. The servo CPU 15 uses the movement command distributed to each axis and the position and speed feedback signals detected by the position / speed detectors P1, P2, P3, P4, 53, 54, etc. Based on this, digital servo processing is executed to drive and control the servo motors M1, M2, M3, M4, and M5.

  A molding operation using the injection molding machine M will be described. When the movable platen forward / reverse motor M3 is rotated in the forward direction, the ball screw shaft 38 is rotated in the forward direction, and the crosshead 34 screwed to the ball screw shaft 38 is moved forward (to the right in FIG. 4). When the mechanism 20 is actuated, the movable platen 30 is advanced.

  When the movable mold 40a attached to the movable platen 30 comes into contact with the fixed mold 40b (mold closed state), the mold clamping process is started. In the mold clamping process, a mold clamping force is generated in the mold 40 by the toggle mechanism 36 by further driving the movable platen forward / reverse motor M3 in the forward direction. The screw servo motor M1 provided in the injection part Mi is driven to move forward in the axial direction of the screw 3, so that the cavity space formed in the mold 40 is filled with the molten resin. When opening the mold, when the movable platen forward / reverse motor M3 is driven in the reverse direction, the ball screw shaft 38 is rotated in the reverse direction. Along with this, the cross head 34 moves backward, the toggle mechanism 36 operates in a bending direction, and the movable platen 30 moves backward in the direction of the rear platen 31. When the mold opening process is completed, the ejector forward / reverse motor M4 for ejecting the ejector pin that pushes out the molded product from the movable mold 40a is operated. Thereby, an ejector pin (not shown) is protruded from the inner surface of the movable mold 40a, and a molded product in the movable mold 40a is protruded from the movable mold 40a.

  Next, a mold clamping force setting method and a mold clamping force setting device according to an embodiment of the present invention will be described. In the embodiment of the present invention, a mold clamping force sensor 41 attached to the tie bar 32 is used to set an appropriate mold clamping force of the injection molding machine. The mold clamping force sensor 41 is a sensor provided for detecting the mold clamping force during molding. The embodiment of the present invention is a method and apparatus for obtaining an appropriate mold clamping force based on a detection value of a mold clamping force sensor 41 that is originally provided.

As described in the subject of the present invention, the proper clamping force does not generate burrs according to the resin pressure generated when the resin is injected into the mold, and the mold is deformed. There is no value.
Obtaining such an appropriate value of the mold clamping force is important in order to keep the mold clamping force to the minimum necessary level and not to shorten the mold life unnecessarily.

As described with reference to FIGS. 1, 2, and 3, when the mold clamping force is insufficient, as shown in FIG. 3, the maximum value of the detected mold clamping force according to the change in the set mold clamping force. Also changes.
In the present invention, in an injection molding machine equipped with a mold clamping force detection device, injection is attempted with two or more different set mold clamping forces, and the maximum value of the mold clamping force during injection is detected. Then, two or more combinations are extracted from the set mold clamping force and the detected maximum mold clamping force value such that the maximum mold clamping force value during injection is greater than the set mold clamping force. Then, from among the extracted combinations, a mold clamping force that makes the set mold clamping force equal to the maximum value of the mold clamping force during injection is obtained and set as the set mold clamping force (see FIG. 5). In addition, when there are three or more extracted combinations, a quadratic or higher approximation formula is applied, and the mold clamping force is set so that the set clamping force is equal to the maximum value of the clamping force during injection. The force may be obtained by calculation to obtain a set clamping force (see FIG. 6).
The above injection refers to all processes in which the screw 3 is operated to fill the cavity space in the mold 40 with the molten resin, and only the process of injecting the molten resin into the cavity space in the mold 40. In addition, it includes a step called a pressure holding step, in which a pressure is applied to the molten resin to completely fill the cavity space in the mold 40 with the molten resin.
As described above, according to the present invention, it is possible to accurately obtain an appropriate clamping force without generating burrs with the minimum number of trials and with less deformation of the mold.

FIG. 5 is a graph for explaining obtaining a mold clamping force such that the maximum value of the detected mold clamping force is equal to the set mold clamping force by a linear approximation formula. The horizontal axis represents the set mold clamping force (Fs), and the vertical axis represents the maximum value (Fmax) of the detected mold clamping force during injection.
Explaining in correspondence with FIG. 3, the maximum value (Amax) of the mold clamping force detected when the first set mold clamping force (A) is set and injection is performed, and the second set mold clamping force (B ) Is the maximum value (Bmax) of the clamping force detected when the injection is performed. Since both the values of Amax and Bmax are values above the straight line where Fmax = Fs, there are two sets of combinations in which the maximum value of the mold clamping force during injection is greater than the set mold clamping force. Therefore, the first set mold clamping force (A), the maximum value (Amax) of the detected mold clamping force, the second set mold clamping force (B), and the maximum value of the detected mold clamping force (Bmax). Thus, the two coefficients a and b of the linear approximation formula (Fmax = a * Fs + b) can be obtained. Then, by obtaining the intersection of Fmax = Fs and the linear approximation formula (Fmax = a * Fs + b), an appropriate set mold clamping force Fs that does not cause burrs and does not cause deformation of the mold _{(good )} Value.
In FIG. 5, data of two measurement points are used. However, a linear approximation expression may be obtained by a method such as a least square method using data of a larger number of measurement points.

Here, setting the mold clamping device of the injection molding machine to an appropriate set mold clamping force Fs _(good) will be described. If the set mold clamping force is currently B, the difference in mold clamping force from the appropriate set mold clamping force Fs _(good) obtained as the intersection may be adjusted. Since the relationship between the magnitude of the mold clamping force and the extension of the tie bar 32 is proportional as described above, the position of the rear platen 31 is determined by the amount of movement corresponding to the magnitude of the mold clamping force that needs to be adjusted. Adjustment may be performed by driving the adjustment motor M5.

  FIG. 6 is a graph for explaining how to obtain a mold clamping force such that the maximum value of the detected mold clamping force is equal to the set mold clamping force by a quadratic approximate expression. The horizontal axis represents the set mold clamping force (Fs), and the vertical axis represents the maximum value (Fmax) of the detected mold clamping force during injection.

Explaining in correspondence with FIG. 3, the maximum value (Amax) of the mold clamping force detected when the first set mold clamping force (A) is set and injection is performed, and the second set mold clamping force (B ) Is set to the maximum value (Bmax) of the mold clamping force detected when the injection is performed, and the maximum value of the mold clamping force detected when the third set mold clamping force (C) is set (Bmax). Cmax). Since the values of Amax, Bmax, and Cmax are values above the straight line where Fmax = Fs, there are three sets of combinations in which the maximum value of the mold clamping force during injection is greater than the set mold clamping force. . Therefore, the first set clamping force (A), the detected maximum value (Amax) of the clamping force, the second set clamping force (B), the detected maximum value of clamping force (Bmax), Three coefficients a of a quadratic approximate expression (Fmax = a * Fs ² + b * Fs + c) are obtained by three combinations of the third set clamping force (C) and the maximum value (Cmax) of the detected clamping force. b and c can be obtained. Then, by obtaining the intersection of Fmax = Fs and the quadratic approximation (Fmax = a * Fs ² + b * Fs + c), an appropriate setting die that does not generate burrs and does not cause deformation of the mold. The value of the fastening force Fs _(good) can be obtained.

  FIG. 7 is a diagram for explaining the maximum value of the set clamping force and the detected clamping force during injection stored in the memory. It is an example of the concrete numerical value memorize | stored in the memory of the injection molding machine corresponding to (setting die clamping force Fs, the maximum value Fmax of the detection die clamping force during injection) shown by FIG.3, FIG.5, FIG.6. The set mold clamping force Fs (A) for the first injection trial frequency and the maximum value Fmax (Amax) of the detected mold clamping force during injection are 25 tons and 27 tons, respectively, and the set mold clamping force Fs (second injection trial frequency for the second time). B) The maximum value Fmax (Bmax) of the detected clamping force during injection is 15 tons and 20 tons, respectively. The set mold clamping force Fs (C) for the third injection trial and the maximum value Fmax (Cmax) of the detected mold clamping force during injection are 10 tons and 17 tons, respectively. For example, a linear approximation expression can be obtained using the first and second data. Further, a quadratic approximate expression can be obtained using the data of the first to third times.

FIGS. 8A and 8B are flowcharts showing an algorithm of processing for calculating an appropriate mold clamping force according to the present invention. Hereinafter, it demonstrates according to each step.
[Step SA01] One molding cycle is executed with the set mold clamping force Fs1, the detected mold clamping force during injection is acquired, the maximum value Fmax1 is specified, and the difference between the maximum value Fmax1 and the set mold clamping force Fs1 The maximum increase amount Finc1 of the mold clamping force is stored in association with the set mold clamping force Fs1.
[Step SA02] Set mold clamping force Fs2 is (Fs1 + ΔFs). ΔFs is a positive value.
[Step SA03] One molding cycle is executed with the set mold clamping force Fs2, the detected mold clamping force during injection is acquired, the maximum value Fmax2 is specified, and the difference between the maximum value Fmax2 and the set mold clamping force Fs2 is The maximum increase amount Finc2 of the mold clamping force is stored in association with the set mold clamping force Fs2. The maximum value of the detection mold clamping force can be specified using a conventionally known technique.
[Step SA04] It is determined whether Finc1 obtained in Step SA01 is equal to Finc2 obtained in Step SA03. If they are equal, the process proceeds to Step SA09, and if they are not equal, the process proceeds to Step SA05.
[Step SA05] The set mold clamping force Fs3 is set to (Fs1-ΔFs).
[Step SA06] One molding cycle is executed with the set mold clamping force Fs3, the detected mold clamping force during injection is acquired, the maximum value Fmax3 is specified, and the set mold clamping force Fs3 and the maximum value Fmax3 are associated with each other. Remember.
[Step SA07] A linear approximate expression is obtained from (set mold clamping forces Fs1, Fmax1) and (set mold clamping forces Fs3, Fmax3).
[Step SA08] The coordinates of the intersection point are obtained by the linear approximation formula obtained in Step SA07 and the two formulas Fmax = Fs, an appropriate mold clamping force Fs _(good) is calculated, and the process is terminated.
[Step SA09] Set mold clamping force Fs3 is (Fs1-ΔFs).
[Step SA10] One molding cycle is executed with the set mold clamping force Fs3, the detected mold clamping force during injection is acquired, its maximum value Fmax3 is specified, and the difference from the set mold clamping force Fs3, that is, the maximum mold clamping force The increase amount Finc3 is stored in association with the set mold clamping force Fs3.
[Step SA11] It is determined whether Finc1 obtained in Step SA01 and Finc3 obtained in Step SA10 are equal. If they are equal, the process proceeds to Step SA12, and if not, the process proceeds to Step SA13.
[Step SA12] (Fs3−ΔFs) is newly set as the set clamping force Fs3, and the process returns to Step SA09 to continue the process.
[Step SA13] Set Fs4 to (Fs3-ΔFs).
[Step SA14] One molding cycle is executed with the set mold clamping force Fs4, the detected mold clamping force during injection is acquired, the maximum value Fmax4 is specified, and the set mold clamping force Fs4 and the maximum value Fmax4 are associated with each other. Remember.
[Step SA15] A linear approximate expression is obtained from (set mold clamping forces Fs3, Fmax3) and (set mold clamping forces Fs4, Fmax4).
[Step SA16] The coordinates of the intersection point are obtained by the linear approximation formula obtained in Step SA15 and the two formulas Fmax = Fs, an appropriate set clamping force Fs _(good) is calculated, and the process is terminated.

  FIG. 8 is a flowchart for obtaining an appropriate clamping force by linear approximation. When obtaining an appropriate clamping force using an approximate expression of second or higher order, it is necessary to collect data of more measurement points corresponding to the order. In this case, for example, in the flowchart of FIG. 8, the set mold clamping force is decreased continuously after step SA06, the maximum value of the detected mold clamping force is specified, and the detected mold clamping force is associated with the set mold clamping force. Is stored, and instead of obtaining the linear approximate expression in step SA07, an approximate expression having a higher order is obtained using the data of the obtained many measurement points. Similarly, continuing to step SA14, the set mold clamping force is reduced, the maximum value of the detected mold clamping force at that time is specified, and the maximum value of the detected mold clamping force is stored in association with the set mold clamping force. Instead of obtaining the linear approximate expression in step 15, an approximate expression having a higher order is obtained using the data of the obtained many measurement points.

5 Resin pressure sensor 41 Mold clamping force sensor

Fs Setting mold clamping force Fs _(good) Appropriate setting mold clamping force Fmax Maximum value of detected mold clamping force during injection

Claims (6)

  Based on the set mold clamping force, the mold is closed by the mold clamping mechanism to generate a mold clamping force, the injection mechanism injects molten resin into the mold, and the mold clamping force is set by two or more different set mold clamping forces. The mold clamping force during the injection is detected and the maximum value of the mold clamping force detected during the injection is larger than the set mold clamping force. Two or more combinations of the maximum detected mold clamping force and the set mold clamping force are extracted, and the maximum value of the detected mold clamping force is determined from the combination of the extracted maximum detected mold clamping force and the set mold clamping force. And the set mold clamping force, find the mold clamping force that makes the maximum value of the detected mold clamping force equal to the set mold clamping force, and set the calculated mold clamping force. A mold clamping force setting method for an injection molding machine.   2. The mold clamping force setting method for an injection molding machine according to claim 1, wherein the relational expression is obtained by applying a linear approximation.   The relational expression is obtained by applying a quadratic or higher approximation formula when there are three or more combinations of the extracted maximum value of the detected mold clamping force and the set mold clamping force. 2. A mold clamping force setting method for an injection molding machine according to 1. A mold clamping unit that generates a mold clamping force by closing the mold based on the set mold clamping force;
An injection part for injecting molten resin into the mold,
A detection unit for detecting a maximum value of mold clamping force during injection of the molten resin by the injection unit;
A setting mold clamping force setting unit that generates a mold clamping force with two or more different setting mold clamping forces to perform injection, the set mold clamping force, and a maximum value of the detected mold clamping force detected during the injection; A storage unit for storing
An extracting unit for extracting two or more combinations of the set mold clamping force stored in the storage unit and the detected mold clamping force, wherein the maximum value of the detected mold clamping force is greater than the set mold clamping force;
A relational expression calculation unit for obtaining a relational expression between the maximum value of the detected mold clamping force and the set mold clamping force from the combination of the extracted maximum value of the detected mold clamping force and the set mold clamping force;
An appropriate mold clamping force calculation unit for obtaining a mold clamping force such that the maximum value of the detected mold clamping force and the set mold clamping force are equal from the relational expression;
With
A mold clamping force setting device for an injection molding machine, which sets a mold clamping force obtained by an appropriate mold clamping force calculation unit.   5. The mold clamping force setting device for an injection molding machine according to claim 4, wherein the relational expression is obtained by applying a linear approximation.   The relational expression is obtained by applying a quadratic or higher approximation formula when there are three or more combinations of the extracted maximum value of the detected mold clamping force and the set mold clamping force. 4. A mold clamping force setting device for an injection molding machine according to 4.

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