JP2013075382A - Method and apparatus for setting mold clamping force for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for setting a mold clamping force of an injection molding machine, configured to prevent burr while improving the quality by degassed molding or to prevent reduction in the service life of a mold by determining a necessary and minimum set mold clamping force for preventing the mold from being opened.SOLUTION: When a transition point from a state 2 (the section in which a mold clamping force maximum increment in injection is increased when a set mold clamping force is increased) to a state 3 (the section in which the mold clamping force maximum increment is increased larger than in the state 2) is detected, measurement is performed at two arbitrary points of the two sections to acquire measured mold clamping force maximum increment Amax and mold clamping maximum increment Bmax respectively, and linear approximate expression Fmax=a*Fs+b is determined. Since a set clamping force C in the state 2 satisfies mold clamping force maximum increment Cmax≤(A*C+b)+β, and a set mold clamping force D in the state 3 satisfies measured mold clamping force maximum increment Dmax>(a*D+b)+β. The transition to the state 3 can be determined accordingly, and a proper mold clamping force can be set on the basis of the set mold clamping force in the transition from the state 2 to the state 3.

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.

  In the injection molding cycle, the mold is closed by a mold closing process, a set clamping force is generated by the mold clamping process, and then a molten resin is injected into the mold. 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, if the mold clamping force is excessive, there is no worry about burrs, but the gas will not escape and the quality will deteriorate, and the mold clamping force will be applied to the mold more than necessary. There's a problem. Therefore, the mold clamping force should be set to the minimum value that does not open the mold when injecting to prevent the occurrence of burrs, and it should not cause an excessive load on the mold as it is prone to outgassing. In order to make this possible, it is desirable to find and set a minimum clamping force that does not open such a mold. As a technique for setting 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

In the technique disclosed in Patent Document 1 described in the prior art, it is necessary to perform 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 it is impossible to efficiently obtain a proper mold clamping force. In the technique disclosed in Patent Document 2, it is necessary to obtain coefficients such as a projected area and a safety factor. The projection area must be obtained by analyzing the mold drawing, and the safety factor is generally an empirical value, so it is extremely difficult to obtain an accurate value. Therefore, it is difficult to obtain an accurate minimum clamping force with the technique of Patent Document 2.
Therefore, an object of the present invention is to obtain a minimum setting clamping force that does not open the mold, thereby preventing burrs caused by opening the mold and molding in a state in which gas is likely to escape. It is an object of the present invention to provide a mold clamping force setting method and a mold clamping force setting device for an injection molding machine that do not impose an unnecessary burden on the mold and do not unnecessarily shorten the mold life.

The invention according to claim 1 of the present application is an injection molding machine in which a mold is closed by a mold clamping mechanism based on a set mold clamping force to generate a mold clamping force, and a molten resin is injected into the mold by an injection mechanism. Injecting with a set clamping force of any different size, clamping force generated when the mold is closed, and clamping during injection occurring when molten resin is injected into the mold The maximum value of the clamping force is detected by calculating the maximum increase in clamping force, which is the difference between the clamping force generated when the mold is closed and the clamping force during injection. Two or more set mold clamping forces that are different in increase amount and do not open the mold are extracted, and the combination of the two or more extracted set mold clamping forces and the maximum mold clamping force increase amount is used to set the mold clamping force. A relational expression indicating the maximum increase amount of the mold clamping force is obtained, and the set mold clamping is smaller than the two or more different set mold clamping forces extracted. The mold clamping force maximum increase amount is calculated by performing injection, and the set mold clamping force at the time when the calculated mold clamping force maximum increase amount exceeds the comparison value based on the relational expression is obtained. A mold clamping force setting method for an injection molding machine, characterized in that a mold clamping force immediately before a clamping force is set as a minimum mold clamping force that prevents a mold from opening.
In the invention according to claim 2, extracting two or more set mold clamping forces that are different in the maximum increase amount of the mold clamping force and do not open the mold reduces the magnitude of the set mold clamping force from a large value. When the injection is performed while changing to a value, if the change amount of the maximum increase amount of the mold clamping force is smaller than the first predetermined value, the setting mold clamping force before the change is removed. A mold clamping force setting method for an injection molding machine according to claim 1.
The invention according to claim 3 is that the maximum amount of mold clamping force increase is different, and two or more set mold clamping forces that do not open the mold are extracted. 2. The mold clamping force setting method for an injection molding machine according to claim 1, further comprising removing a set mold clamping force when the value is smaller than the value of.
The invention according to claim 4 is the mold clamping force setting method for an injection molding machine according to any one of claims 1 to 3, wherein the relational expression is obtained by applying linear approximation.
The invention according to claim 5 is characterized in that a threshold used as one term for the comparison value is set in advance or is automatically determined from a measured value of the clamping force. The mold clamping force setting method of the injection molding machine described in 1.

In the invention according to claim 6, in the case of performing injection with the set mold clamping forces of any two or more different sizes, the set mold clamping force that is sufficient in consideration of the maximum injection pressure and the projected area of the mold The mold of the injection molding machine according to any one of claims 1 to 5, wherein an injection is started at a step, and a maximum increase in mold clamping force during each injection is calculated while lowering the set mold clamping force. This is a tightening force setting method.
In the invention according to claim 7, the set clamping force at which the change in the maximum increase amount of the mold clamping force is different and the mold does not open is calculated by performing injection and calculating the maximum increase amount of the clamping force. 7. The injection mold machine according to claim 1, wherein the set mold clamping force causes a change in the maximum increase amount, and is a set mold clamping force when the molded product can be determined to be a non-defective product. This is a mold clamping force setting method.
The invention according to claim 8 is characterized in that the necessary minimum mold clamping force is corrected by a preset margin. Clamping of an injection molding machine according to any one of claims 1 to 7 Force setting method.
The invention according to claim 9 includes 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 molten resin into the mold, and an arbitrary set mold clamping. A detection unit that performs injection with force and detects a maximum value of a mold clamping force that is generated when the mold is closed and a mold clamping force that is generated when the molten resin is injected into the mold; A mold clamping for obtaining a maximum increase in mold clamping force from a difference between a mold clamping force generated when the mold is closed and a maximum value of mold clamping force generated during injection of molten resin into the mold. A force increase calculation unit; a storage unit for storing the mold clamping force generated when the mold is closed and the mold clamping force maximum increase in correspondence; and at least two calculations of the mold clamping force maximum increase. Performed with two or more different setting mold clamping forces, and extracted two or more set clamping forces that differ in the maximum increase in mold clamping force and do not open the mold. And a relational expression indicating a maximum increase amount of the clamping force with respect to the set clamping force from a combination of the clamping force generated when the extracted mold is closed and the maximum increase amount of the clamping force. Injection is performed with a relational expression calculation unit and a set mold clamping force smaller than the two or more different set mold clamping forces, the mold clamping force maximum increase amount is calculated, and the mold clamping force maximum increase amount is expressed in the relational expression A mold clamping force detection unit that obtains a set mold clamping force that exceeds a comparison value based on the minimum, and the minimum required to prevent the mold from opening the set mold clamping force immediately before the mold clamping force detected by the mold clamping force detection unit. A mold clamping force setting device for an injection molding machine, characterized in that the mold clamping force is set as a mold clamping force.
According to a tenth aspect of the present invention, when the extraction unit performs injection while changing the magnitude of the set mold clamping force from a large value to a small value, the amount of change in the mold clamping force maximum increase amount is the first amount. 10. The mold clamping force setting device for an injection molding machine according to claim 9, further comprising removing a set mold clamping force before being changed when it is smaller than a predetermined value.
The invention according to claim 11 is characterized in that the extraction unit includes removing a set mold clamping force when the maximum amount of mold clamping force increase is smaller than a second predetermined value. This is a mold clamping force setting device for an injection molding machine.

The invention according to claim 12 is the mold clamping force setting device for an injection molding machine according to any one of claims 9 to 11, wherein the relational expression is obtained by applying linear approximation.
The invention according to claim 13 is characterized in that a threshold used as one term for the comparison value is set in advance or is automatically determined from a measured value of the clamping force. The mold clamping force setting device of the injection molding machine described in 1.
In the invention according to claim 14, in the case of performing injection with the set mold clamping forces of any two or more different sizes, the set mold clamping force that is sufficient in consideration of the maximum injection pressure and the projected area of the mold The mold of the injection molding machine according to any one of claims 9 to 13, wherein the injection is started at, and the maximum increase amount of the clamping force during each injection is calculated while lowering the set clamping force. It is a tightening force setting device.
According to a fifteenth aspect of the present invention, the means for obtaining a set mold clamping force at which the change in the mold clamping force maximum increase amount is different and the mold does not open calculates the mold clamping force maximum increase amount by performing injection, 15. The setting mold clamping force that causes a change in the maximum amount of mold clamping force, and is a means for selecting a set mold clamping force when the molded product can be determined to be a non-defective product. A mold clamping force setting device for an injection molding machine according to the above.
The invention according to claim 16 is characterized in that the necessary minimum mold clamping force is corrected by a preset margin. Clamping of an injection molding machine according to any one of claims 9 to 15 It is a force setting device.

  According to the present invention, it is possible to prevent burrs caused by opening the mold by obtaining the minimum required setting clamping force that does not open the mold, and quality by molding in a state in which gas is likely to escape. It is possible to provide a mold clamping force setting method and a mold clamping force setting apparatus for an injection molding machine that do not impose an unnecessary burden on the mold and unnecessarily shorten the mold life.

It is a graph which shows the relationship between the setting mold clamping force and the mold clamping force maximum increase amount at the time of injection. It is a graph which shows the time change of mold clamping force. It is a figure explaining the setting mold clamping force and the mold state at the time of injection. It is a graph explaining the variation | change_quantity determination method of mold clamping force maximum increase amount. It is a schematic block diagram of an injection molding machine. It is a flowchart which shows the algorithm of the process which calculates | requires appropriate clamping force using a linear approximation formula (the 1). It is a flowchart which shows the algorithm of the process which calculates | requires appropriate clamping force using a linear approximation formula (the 2). It is a graph explaining calculating | requiring an appropriate clamping force based on the intersection of a linear approximation formula. It is a flowchart which shows the algorithm of the process which calculates appropriate mold clamping force based on the intersection of a linear approximation formula (the 1). It is a flowchart which shows the algorithm of the process which calculates appropriate mold clamping force based on the intersection of a linear approximation formula (the 2). It is a flowchart which shows the algorithm of the process which calculates appropriate mold clamping force based on the intersection of a linear approximation formula (the 3).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
If the clamping force is insufficient with respect to the pressure at which the molten resin is generated, the mold opens and burrs are generated. Defeat the set clamping force and injection pressure at the time of injection when the clamping force is lowered from the sufficient clamping force that can be considered with reference to the maximum injection pressure and the projected area of the die to the state where the die opens. FIG. 1 shows the relationship between the maximum amount of increase in mold clamping force that represents the amount of mold opening when the mold is opened. Here, the maximum increase in mold clamping force means the difference between the set mold clamping force and the maximum value of mold clamping force (detected value) during injection, as shown in FIG. If this relationship is analyzed, it can be divided into the following three states. The state of the mold at the time of injection in each state is shown in FIG. The mold thickness is L.

State 1: A section in which the maximum increase amount of the mold clamping force at the time of injection does not change even if the set mold clamping force is lowered. In this section, since the mold clamping force is sufficient with respect to the injection pressure, the mold is distorted so as to be compressed. Ideally, there is no change in the maximum increase in mold clamping force during injection. The mold is compressed by the strain amount δ1 by the mold clamping force, the mold thickness becomes L−δ1, and the distance between the platens (between the movable platen and the fixed platen) also becomes L−δ1.
State 2: A section in which the maximum amount of mold clamping force increase during injection increases when the set mold clamping force is lowered. In this section, the mold clamping force is lower than that in state 1 so that the mold is opened against the injection pressure, so that the mold distortion generated in state 1 is gradually released. Therefore, the maximum increase in mold clamping force at the time of injection is increased by the amount that the strain is released at the time of injection. A little strain is released, and the compression of the mold becomes a strain amount δ2 smaller than δ1. Therefore, the mold thickness is L−δ2 (0 <δ2 <δ1), and the distance between the platens is also L−δ2 (0 <δ2 <δ1).
State 3: A section in which the maximum increase amount of the mold clamping force at the time of injection increases more than in the state 2 when the set mold clamping force is lowered. In this section, since the mold strain generated in states 1 and 2 is completely released at the time of injection, the mold thickness is L, and in addition, the mold opening amount δ3 occurs, so the distance between the platens is L + δ3.

  The above injection refers to all processes in which the screw is operated to fill the cavity space in the mold with the molten resin. This is called a pressure holding process, and pressure is applied to the molten resin to create a cavity in the mold. It also includes a step of completely filling the space with the molten resin.

  FIG. 4 is a diagram for explaining a method of determining the amount of change in the maximum increase amount of the mold clamping force. FIG. A graph illustrating the above is shown. The horizontal axis is the set mold clamping force (Fs), and the vertical axis is the maximum amount of mold clamping force increase (Fmax) during injection. In order to detect the transition point between the state 2 and the state 3, first, the change in the state 2 is obtained by a linear approximation formula. Therefore, as shown in FIG. 3, measurement is performed at any two points in two sections in a state where the mold strain is released and the maximum amount of increase in the mold clamping force is changed. The mold clamping force maximum increase amount Amax measured in this way and the mold clamping force maximum increase amount Bmax measured with respect to the set mold clamping force B are acquired. At this time, if the mold clamping force maximum increase amount Amax is equal to Bmax, since this point is the state 1 section, the set mold clamping force is lowered and measurement is performed again at a point where Amax <Bmax as shown in FIG.

  Based on the measured values Amax and Bmax, a linear approximate expression Fmax = a * Fs + b indicating the maximum amount of mold clamping force increase in state 2 can be calculated. Since this linear approximation Fmax = a * Fs + b represents an increase in mold clamping force due to release of mold strain in state 2, the maximum increase in mold clamping force measured with respect to the set mold clamping force C in the state 2 section The amount Cmax is a value that satisfies Cmax ≦ (a * C + b) + β. At this time, β is a threshold value that takes into account measurement errors and variations, performs injection several times with the same set clamping force, detects the maximum increase in clamping force, and detects the difference between the maximum and minimum detection values. Can be used as a threshold value. The method for obtaining the threshold value is not limited to this method.

  Next, since the state 3 is in a state where the mold is released and the mold is opened, the amount of increase in the mold clamping force is greatly changed. For this reason, the mold clamping force maximum increase amount Dmax measured with respect to the set mold clamping force D in the state 3 section is Dmax> (a * D + b) + β. In other words, the transition point from state 2 to state 3 is determined by obtaining the linear approximation formula Fmax = a * Fs + b from the maximum amount of mold clamping force increase at any two points in the state 2 section, and lowering the set mold clamping force X. When the maximum clamping force increase amount Xmax measured in the course of the process satisfies Xmax> (a * X + b) + β, it is determined as a transition point to the state 3. Then, the set clamping force at a point before the transition point is detected as the lowest clamping force at which the mold does not open. If a slight burr is not allowed, the minimum clamping force detected as a margin may be corrected within the state 2 section. Further, the transition from the state 2 to the state 3 may be performed by two different set mold clamping forces that are not dependent on one set mold clamping force. In this case, when Xmax> (a * X + b) + β is continuously satisfied, it is determined that the state 2 is shifted to the state 3.

  The mold clamping force in state 2 where mold strain is released is the mold clamping force in state 1, which is sufficient to consider the maximum injection pressure and the projected area of the mold. The maximum increase in mold clamping force during each injection can be calculated while lowering the value, and this can be obtained from the point where the maximum increase in mold clamping force occurs. In addition to the method of obtaining the set mold clamping force in state 2 by changing the mold clamping force from state 1 to state 2 above, the mold clamping force maximum increase amount is calculated with any set mold clamping force, and the mold clamping is calculated. In the setting mold clamping force that causes a change in the maximum force increase amount, the mold clamping force when the molded product can be determined to be a non-defective product by the operator and camera monitoring and the pass / fail judgment function can also be obtained as the set mold clamping force of state 2.

  In an injection molding machine equipped with a mold clamping force detection device, an embodiment of the present invention attempts injection from a mold clamping force that is considered sufficient with reference to the maximum injection pressure and the projected area of the mold. It can cope with measuring the maximum increase in mold clamping force during each injection while lowering the clamping force. That is, by setting an arbitrary mold clamping force corresponding to the state 1, it is possible to cope with measuring the maximum amount of mold clamping force increase during each injection while lowering the mold clamping force. In the embodiment of the present invention, at least two different mold clamping forces are set in at least the state 2 to obtain two mold clamping force maximum increases, and at least one mold clamping force is set in the state 3 to obtain one mold clamping. It is necessary to find the maximum force increase.

  As described above, the maximum increase in mold clamping force means the difference between the set mold clamping force and the maximum value of the mold clamping force during injection. Since the set mold clamping force and the actual mold clamping force applied to the mold do not always match depending on the size and structure of the mold, in the embodiment of the present invention, it is detected after mold clamping and before injection. The exact maximum increase in mold clamping force may be measured from the difference between the mold clamping force and the maximum value of the mold clamping force detected during injection. Then, it is necessary to detect the point at which the maximum increase in mold clamping force during injection shifts from state 2 to state 3 (the point at which the maximum increase in mold clamping force changes greatly), and the mold does not need to open the mold clamping force immediately before that. It can be determined as the minimum set clamping force. Further, as another embodiment, linear approximation expressions can be obtained in state 2 and state 3, respectively, and can be obtained as the minimum required set clamping force that prevents the mold from opening based on the intersection of these linear approximation expressions.

  FIG. 5 is a schematic block diagram of the injection molding machine. The injection molding machine shown in FIG. 5 is configured as 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 servo motor M3 for moving the movable platen 30 forward and backward, a rear platen 31, an ejector forward / reverse servo motor M4 for ejecting an ejector pin for pushing out a molded product from the mold, a movable platen 30, and a tie bar 32. , A fixed platen 33, a cross head 34, an ejector mechanism 35, and a toggle mechanism 36. 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 servomotor 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 generated by the propulsive force of the movable platen forward / backward servomotor 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. A detection signal from the mold clamping force sensor 41 is sent to the servo CPU 15 via the A / D converter 27. The graph of the relationship between the mold clamping force (detected value) and time shown in FIG. 2 is obtained based on the detection signal from the mold clamping force sensor 41. Then, the servo mold 15 calculates the set mold clamping force and the mold clamping force maximum increase, which is the difference between the set mold clamping force and the maximum mold clamping force during injection, and stores the obtained data in the RAM 14. Here, the difference is the die clamping force detected after the end of mold closing and before the start of injection. Alternatively, a set clamping force value may 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. In the present invention, by driving the mold clamping position adjusting motor M5, an optimal mold clamping force can be set by executing the processing shown in FIGS. 6 and 8, for example.

  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.

  A 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 includes servo amplifiers 11 and 12 that drive a screw forward / backward servomotor M1 connected to the injection shaft and a screw rotation servomotor M2 connected to the screw rotation shaft based on a command from the servo CPU15. The outputs from the position / speed detectors P1, P2 connected 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 the bus 26 via an interface (I / F) 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 servomotor M3 is rotated in the forward direction, the ball screw shaft 38 is rotated in the forward direction, and the cross head 34 screwed into the ball screw shaft 38 is moved forward (rightward in FIG. 4). When the toggle mechanism 36 is activated, 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 / backward servomotor 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 the mold is opened, the ball screw shaft 38 is rotated in the reverse direction when the movable platen forward / reverse servo motor M3 is driven 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, an ejector forward / reverse servomotor M4 for ejecting an 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.

FIG. 6 is a flowchart showing an algorithm of processing for obtaining an appropriate mold clamping force using a linear approximation formula. Hereinafter, it demonstrates according to each step.
[Step SA01] Set an initial value N = 1. N is an index representing the number of trials for specifying the maximum mold clamping force increase amount.
● [Step SA02] Execute 5 molding cycles with the set mold clamping force FsN, measure the maximum mold clamping force increase during injection, and use frequent values and center values to eliminate variations and errors in measured values. The set mold clamping force FsN and the maximum mold clamping force increase amount FmaxN with respect to the set mold clamping force FsN are stored in one point. In addition, although it is set as 5 molding cycles here, it is not limited to 5 molding cycles, and when there is no variation in measurement values, one molding cycle may be used, and when there is variation in measurement values, the number of samples is larger. You may measure by increasing. The same applies to the other steps in the 5 molding cycles. The frequent value is a value having the highest appearance frequency among the five maximum mold clamping force increase amounts FmaxN.
[Step SA03] The set clamping force FsN + 1 is set to (FsN−ΔFs). ΔFs is a positive value.
[Step SA04] Execute 5 molding cycles with the set mold clamping force FsN + 1, measure the maximum mold clamping force increase during injection, and use frequent values and center values to eliminate measurement value variations and errors. One point of the maximum mold clamping force increase FmaxN + 1 with respect to the set mold clamping force FsN + 1 and the set mold clamping force FsN + 1 is stored.
[Step SA05] If FmaxN obtained immediately before and FmaxN + 1 obtained most recently are FmaxN + 1> FmaxN + α (that is, YES), the process proceeds to Step SA07, and if FmaxN + 1> FmaxN + α is not satisfied (that is, NO) In the case), the process proceeds to step SA06. Note that α (> 0) is a value that allows a measurement error in the state 1, and corresponds to the first predetermined value according to claim 2 or claim 10.
More specifically, when the process of the flowchart is started and N = 1, Fs1 and Fmax1 are stored in step SA02. In step SA04, Fs2 and Fmax2 are stored. In step SA05, Fmax2 and Fmax1 are compared. If the relationship of step SA05 is not satisfied, the process proceeds to step SA06, N = 2 is set, the process returns to step SA03, and Fs3 and Fmax3 are stored in step SA04, and Fmax3 and Fmax2 are stored in step SA05. Are compared. Then, the processing of step SA03 to step SA06 is continued until the relationship of step SA05 is satisfied.
[Step SA06] The index N is incremented by one to N + 1, and the process returns to Step SA03.
[Step SA07] The index N is incremented by one to N + 1, and the process proceeds to Step SA08.
[Step SA08] Set mold clamping force FsN + 1 is (FsN-ΔFs). ΔFs is a positive value.
● [Step SA09] Execute 5 molding cycles with the set clamping force FsN + 1, measure the maximum amount of clamping force increase during injection, and use frequent values and center values to eliminate variations and errors in measured values. One point of the maximum mold clamping force increase FmaxN + 1 with respect to the set mold clamping force FsN + 1 and the set mold clamping force FsN + 1 is stored.
[Step SA10] Using the latest (FsN, FmaxN) stored in Step SA04 and (FsN + 1, FmaxN + 1) stored in Step SA09, a linear approximation formula Fmax = a * Fs + b is obtained.
Note that when only step SA04 and step SA09 are viewed, both are represented by (FsN + 1, FmaxN + 1). However, since the index N is increased by 1 in step SA07, what is stored in step SA09 is (FsN + 1, FmaxN + 1). ) Is described as (FsN, FmaxN).
[Step SA11] The index N is incremented by 1 to N + 1, and the process proceeds to Step SA12.
[Step SA12] The set clamping force FsN + 1 is set to (FsN−ΔFs). ΔFs is a positive value.
[Step SA13] The molding cycle is executed with the set mold clamping force FsN + 1, the maximum mold clamping force increase during injection is measured, and the set mold clamping force FsN + 1 and the maximum mold clamping force increase FmaxN + 1 are stored.
[Step SA14] The maximum mold clamping force increase amount a * FsN + 1 + b with respect to the set mold clamping force FsN + 1 obtained from the linear approximation obtained in Step SA10 and the maximum mold clamping force increase amount FmaxN + 1 measured in Step SA13 are FmaxN + 1 ≦ ( If a * FsN + 1 + b) + β (that is, YES), the process returns to step SA11. If FmaxN + 1 ≦ (a * FsN + 1 + b) + β is not satisfied (that is, NO), the process proceeds to step SA15.
Here, in the case of NO, it indicates that the state 2 is shifted to the state 3. Although the transition from the state 2 to the state 3 is determined by one measurement value, the measurement may be performed a plurality of times as in the steps SA02, SA04, and SA09. Alternatively, it may be determined that the state shifts from the state 2 to the state 3 when the set mold clamping force is changed and the expression of step SA14 is satisfied twice or more continuously (that is, YES).
In step SA10, β may be obtained simultaneously with the linear approximation formula based on measurement value variations and measurement errors, or may be set in advance as a parameter according to the machine difference of the injection molding machine.
[Step SA15] FsN is set as the set clamping force as the minimum clamping force that prevents the mold from opening, and the process is terminated. Note that FsN is the latest value stored in step SA13.

  Next, an embodiment of the present invention for obtaining an appropriate mold clamping force based on the intersection of linear approximation equations will be described. FIG. 7 is a diagram for explaining obtaining an appropriate clamping force based on the intersection of the linear approximation formula. In the above-described embodiment, the linear approximation formula is obtained in the state 2 (see FIG. 4). In this embodiment, the linear approximation formulas Fmax = a * Fs + b and Hmax = c * Fs + d are obtained in the state 2 and the state 3, respectively. An appropriate mold clamping force can be set based on the intersection of the linear approximation formulas Fmax = a * Fs + b and Hmax = c * Fs + d.

FIG. 8 is a flowchart showing an algorithm of processing for calculating an appropriate mold clamping force based on the intersection of the linear approximation formula. Hereinafter, it demonstrates according to each step.
[Step SB01] N = 1 and an initial value are set. N is an index representing the number of trials for specifying the maximum mold clamping force increase amount.
● [Step SB02] Execute 5 molding cycles with the set mold clamping force FsN, measure the maximum mold clamping force increase during injection, and use frequent values and center values to eliminate variations and errors in measured values. The set mold clamping force FsN and the maximum mold clamping force increase amount FmaxN with respect to the set mold clamping force FsN are stored in one point. In addition, although it is set as 5 molding cycles here, it is not limited to 5 molding cycles, and when there is no variation in measurement values, one molding cycle may be used, and when there is variation in measurement values, the number of samples is larger. You may measure by increasing. The same applies to the other steps in the 5 molding cycles. The frequent value is a value having the highest appearance frequency among the five maximum mold clamping force increase amounts FmaxN.
[Step SB03] The set clamping force FsN + 1 is set to (FsN−ΔFs). ΔFs is a positive value.
● [Step SB04] Execute 5 molding cycles with the set mold clamping force FsN + 1, measure the maximum mold clamping force increase during injection, and use frequent values and center values to eliminate measurement value variations and errors. One point of the maximum mold clamping force increase FmaxN + 1 with respect to the set mold clamping force FsN + 1 and the set mold clamping force FsN + 1 is stored.
[Step SB05] If FmaxN obtained immediately before and FmaxN + 1 obtained most recently are FmaxN + 1> FmaxN + α (that is, YES), the process proceeds to Step SB07, and if FmaxN + 1> FmaxN + α is not satisfied (that is, NO) In the case), the process proceeds to step SB06. Note that α (> 0) is a value that allows a measurement error in the state 1, and corresponds to the first predetermined value according to claim 2 or claim 10.
More specifically, when the process of the flowchart is started and N = 1, Fs1 and Fmax1 are stored in step SA02. In step SB04, Fs2 and Fmax2 are stored. In step SB05, Fmax2 and Fmax1 are compared. If the relationship of step SB05 is not satisfied, the process proceeds to step SB06, N = 2 is set, the process returns to step SB03, and Fs3 and Fmax3 are stored in step SB04, and Fmax3 and Fmax2 are stored in step SB05. Are compared. And the process of step SB03-step SB06 is continued until the relationship of step SB05 is satisfy | filled.
[Step SB06] The index N is incremented by one to N + 1, and the process returns to Step SB03.
[Step SB07] The index N is incremented by 1 to N + 1, and the process proceeds to Step SB08.
[Step SB08] The set mold clamping force FsN + 1 is set to (FsN−ΔFs). ΔFs is a positive value.
● [Step SB09] Execute 5 molding cycles with the set mold clamping force FsN + 1, measure the maximum mold clamping force increase during injection, and use frequent values and center values to eliminate measurement value variations and errors. One point of the maximum mold clamping force increase FmaxN + 1 with respect to the set mold clamping force FsN + 1 and the set mold clamping force FsN + 1 is stored.
[Step SB10] Using the newest (FsN, FmaxN) stored in Step SB04 and (FsN + 1, FmaxN + 1) stored in Step SB09, a linear approximation formula Fmax = a * Fs + b is obtained.
Note that when only step SB04 and step SB09 are viewed, both are represented by (FsN + 1, FmaxN + 1). However, since the index N is increased by 1 in step SB07, what is stored in step SB09 is (FsN + 1, FmaxN + 1). ) Is described as (FsN, FmaxN).
[Step SB11] The index N is increased by one to N + 1, and the process proceeds to Step SB12.
[Step SB12] The set mold clamping force FsN + 1 is set to (FsN−ΔFs). ΔFs is a positive value.
[Step SB13] A molding cycle is executed with the set mold clamping force FsN + 1, the maximum mold clamping force increase during injection is measured, and the set mold clamping force FsN + 1 and the maximum mold clamping force increase FmaxN + 1 are stored.
[Step SB14] The maximum mold clamping force increase amount a * FsN + 1 + b with respect to the set mold clamping force FsN + 1 obtained from the linear approximation obtained in Step SB10 and the maximum mold clamping force increase amount FmaxN + 1 measured in Step SB13 are FmaxN + 1 ≦ ( If a * FsN + 1 + b) + β (that is, YES), the process returns to step SB11. If FmaxN + 1 ≦ (a * FsN + 1 + b) + β is not satisfied (that is, NO), the process proceeds to step SB15.
Here, in the case of NO, it indicates that the state 2 is shifted to the state 3. Although the transition from the state 2 to the state 3 is determined by one measurement value, the measurement may be performed a plurality of times in the same manner as in steps SB02, SB04, and SB09. Alternatively, it may be determined that the state shifts from state 2 to state 3 when the set clamping force is changed and the expression of step SB14 is satisfied twice or more continuously (that is, YES).
In step SB10, β may be obtained at the same time as the linear approximation formula based on measurement value variations and measurement errors, or may be set in advance as a parameter according to the machine difference of the injection molding machine.
[Step SB15] The index N is incremented by 1 to N + 1, and the process proceeds to Step SB16.
[Step SB16] The set clamping force FsN + 1 is set to (FsN−ΔFs). ΔFs is a positive value.
● [Step SB17] Execute 5 molding cycles with the set mold clamping force FsN, measure the maximum mold clamping force increase during injection, and use frequent values and center values to eliminate variations and errors in measured values. One point of the maximum mold clamping force increase FmaxN + 1 with respect to the set mold clamping force FsN + 1 and the set mold clamping force FsN + 1 is stored.
[Step SB18] Using the newest (FsN, FmaxN) stored in Step SB13 and (FsN + 1, FmaxN + 1) stored in Step SB17, a linear approximate expression Hmax = c * Fs + d is obtained.
Note that when only step SB13 and step SB17 are viewed, both are represented by (FsN + 1, FmaxN + 1). However, since the index N is increased by 1 in step SB07, what is stored in step SB17 is (FsN + 1, FmaxN + 1). ) Is described as (FsN, FmaxN).
[Step SB19] Based on the set clamping force at the intersection of the linear approximation formula Fmax and the linear approximation formula Hmax, the minimum mold clamping force that prevents the mold from opening is obtained and set as the set mold clamping force, and the process ends. To do.

The process of the flowcharts shown in FIGS. 6-1, 6-2, FIGS. 8-1 and 8-2 is basically performed by changing the clamping force from state 1 to state 2 and then to state 3. The relational expression of state 2 is obtained. As another embodiment of the present invention, the set mold clamping force Fs is arbitrarily changed, the maximum amount of increase in the mold clamping force is measured in the state 1, state 2 and state 3, and the set mold is stored as described above in the flowchart. The clamping force X and the mold clamping force maximum increase amount Xmax may be stored, and using the stored data, for example, the relational expression may be obtained in order from the smaller of the set mold clamping force X according to the determination procedure of the flowchart. .
Alternatively, the stored data is displayed as a graph on the display screen of the display device / MDI 25 (see FIG. 5), the operator selects two appropriate points that are judged to be in state 2, and the relationship is based on the two selected points. An expression may be calculated. The two points selected by the operator may be selected based on, for example, the rate of increase in the maximum amount of mold clamping force or data on the set mold clamping force that can determine that the molded product is a non-defective product. Further, the maximum increase in mold clamping force may be measured from the set mold clamping force corresponding to the state 2 in consideration of the maximum injection pressure and the projected area of the mold. Alternatively, the quality judgment function using a camera or the like is used to judge the quality of the molded product, and the mold clamping force when the product can be judged as a good product is set as the set mold clamping force of state 2, and the maximum increase in the clamping force at that time Data may be used as data for obtaining a relational expression. Alternatively, when there is no change in the maximum amount of increase in the mold clamping force in the state 1, it is determined whether the set mold clamping force is in the state 1 or the state 2 by using the second predetermined value as a reference for comparison. Also good.

DESCRIPTION OF SYMBOLS 1 Injection cylinder 2 Nozzle 3 Screw 4 Hopper 5 Resin pressure sensor 6 Transmission mechanism 7 Transmission mechanism 8 Servo amplifier 9 Servo amplifier 10 Servo amplifier 11 Servo amplifier 12 Servo amplifier 13 ROM
14 RAM
15 Servo CPU
16 A / D converter 17 PMCCPU
18 ROM
19 RAM
20 CNCCPU
21 ROM
22 RAM
23 Molding data storage RAM
24 interface 25 display device / MDI (manual data input device)
26 bus 27 A / D converter

30 Movable platen 31 Rear platen 32 Tie bar 33 Fixed platen 34 Cross head 35 Ejector mechanism 36 Toggle mechanism 37 Screw part 38 Ball screw shaft

40 Mold 40a Movable mold 40b Fixed mold 41 Clamping force sensor

M injection molding machine Mc mold clamping part Mi injection part M1 screw servo motor for forward and backward movement M2 servo motor for screw rotation M3 movable platen forward and backward servo motor M4 ejector forward and backward servo motor M5 mold clamping position adjustment motor

P5 Position detector

Claims (16)

In an injection molding machine that closes a mold by a mold clamping mechanism based on a set mold clamping force to generate a mold clamping force, and injects molten resin into the mold by an injection mechanism,
Clamping force generated when the mold is closed by injection with a set clamping force of any different size, and mold clamping force during injection generated when the molten resin is injected into the mold The maximum increase in mold clamping force is calculated by calculating the maximum increase in mold clamping force, which is the difference between the mold clamping force generated when the mold is closed and the maximum value of the mold clamping force during injection. Extract two or more set clamping forces that are different in quantity and do not open the mold,
From the combination of the two or more extracted set clamping forces and the maximum clamping force increase, a relational expression indicating the maximum clamping force increase with respect to the set clamping force is obtained.
Performing the injection with a set clamping force smaller than the two or more different set clamping forces extracted to calculate the maximum increase in clamping force;
Obtaining a set clamping force when the calculated maximum increase in clamping force exceeds a comparison value based on the relational expression;
A mold clamping force setting method for an injection molding machine, characterized in that the mold clamping force immediately before the obtained set mold clamping force is set as a minimum mold clamping force that prevents the mold from opening. Extracting two or more set clamping forces at which the maximum increase in mold clamping force is different and the mold does not open is as follows:
When injection is performed while changing the magnitude of the set mold clamping force from a large value to a small value, if the amount of change in the maximum mold clamping force increase is smaller than the first predetermined value, the set mold before the change is made The method for setting a clamping force of an injection molding machine according to claim 1, comprising removing the clamping force.   Extracting two or more set mold clamping forces that are different in the maximum amount of increase in the mold clamping force and do not open the mold means that the set mold when the maximum amount of mold clamping force increase is smaller than a second predetermined value 2. The mold clamping force setting method for an injection molding machine according to claim 1, further comprising removing the clamping force.   The mold clamping force setting method for an injection molding machine according to any one of claims 1 to 3, wherein the relational expression is obtained by applying a linear approximation.   The mold for an injection molding machine according to any one of claims 1 to 4, wherein a threshold value used as one term for the comparison value is set in advance or automatically determined from a measured value of the clamping force. Tightening force setting method.   When injection is performed with a set clamping force of any two or more different sizes, the injection is started with a set clamping force that is sufficient considering the maximum injection pressure and the projected area of the mold, and the setting is performed. The mold clamping force setting method for an injection molding machine according to any one of claims 1 to 5, wherein the maximum amount of mold clamping force increase during each injection is calculated while lowering the mold clamping force.   The mold clamping force is set so that the change in the maximum amount of mold clamping force is different and the mold does not open. The mold clamping force setting method for an injection molding machine according to any one of claims 1 to 6, wherein the mold clamping force is a set mold clamping force when the molded product can be determined as a non-defective product.   8. The mold clamping force setting method for an injection molding machine according to claim 1, wherein the minimum mold clamping force is corrected by a preset margin. A mold clamping unit that closes the mold based on the set mold clamping force to generate a mold clamping force, an injection unit that injects molten resin into the mold, and
Performs injection with any set clamping force, and detects the maximum clamping force generated when the mold is closed and the maximum mold clamping force that is generated when molten resin is injected into the mold. A detector to perform,
A mold clamping for obtaining a maximum increase in mold clamping force from a difference between a mold clamping force generated when the mold is closed and a maximum value of mold clamping force generated during injection of molten resin into the mold. A force increase calculation unit;
A storage unit for storing the mold clamping force generated when the mold is closed and the mold clamping force maximum increase amount in association with each other;
Calculation of the maximum increase in mold clamping force is performed with at least two different setting mold clamping forces. The maximum increase in mold clamping force is different, and there are two or more set clamping forces that do not open the mold. An extractor for extracting;
A relational expression calculation unit for obtaining a relational expression indicating a maximum amount of mold clamping force increase with respect to a set mold clamping force from a combination of a mold clamping force generated when the extracted mold is closed and the mold clamping force maximum increase amount; ,
Injection is performed with a set mold clamping force smaller than the two or more different set mold clamping forces, the mold clamping force maximum increase is calculated, and the mold clamping force maximum increasing exceeds the comparison value based on the relational expression A mold clamping force detector for obtaining mold clamping force;
With
A mold clamping force setting device for an injection molding machine, wherein the set mold clamping force immediately before the mold clamping force detected by the mold clamping force detection unit is set as a minimum mold clamping force that prevents the mold from opening. .   The extraction unit changes when the amount of change in the maximum increase in mold clamping force is smaller than the first predetermined value when injection is performed while changing the magnitude of the set mold clamping force from a large value to a small value. 10. The mold clamping force setting device for an injection molding machine according to claim 9, further comprising removing a set mold clamping force before the operation.   10. The mold clamping force of an injection molding machine according to claim 9, wherein the extraction unit includes removing a set mold clamping force when the maximum amount of mold clamping force increase is smaller than a second predetermined value. Setting device.   The mold clamping force setting device for an injection molding machine according to any one of claims 9 to 11, wherein the relational expression is obtained by applying a linear approximation.   13. The injection molding machine according to claim 9, wherein a threshold value used as one term for the comparison value is set in advance or is automatically determined from a measured value of the clamping force. Mold clamping force setting device.   When injection is performed with a set clamping force of any two or more different sizes, the injection is started with a set clamping force that is sufficient considering the maximum injection pressure and the projected area of the mold, and the setting is performed. The mold clamping force setting device for an injection molding machine according to any one of claims 9 to 13, wherein the maximum amount of mold clamping force increase during each injection is calculated while lowering the mold clamping force.   The means for obtaining the set mold clamping force at which the change in the maximum increase in mold clamping force is different and the mold does not open is calculated by calculating the maximum increase in mold clamping force by injection, and changing to the maximum increase in mold clamping force. The mold of an injection molding machine according to any one of claims 9 to 14, wherein the mold is a means for selecting a set mold clamping force when the molded product can be judged as a non-defective product with a set mold clamping force at which occurrence occurs. Tightening force setting device.   The mold clamping force setting device for an injection molding machine according to any one of claims 9 to 15, wherein the minimum mold clamping force is corrected by a preset margin.

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