JP2022180003A - Determination device and mold clamping device - Google Patents

Abstract

To provide a device that can determine abnormality of a mold platen caused by repetitive stress.SOLUTION: This invention relates to a device for determining a fatigue status of mold platens 12, 13 that comprise a mold clamping device. The determination device includes: a memory unit 45 that stores historical data of actual stress values measured for the mold platens 12, 13; a display 41 for showing the historical data of actual stress values; and a determination unit 49 for making a determination about the measured actual stress values. The determination unit 49 makes a first determination as to whether or not a measured actual stress value exceeds a predetermined allowable stress value. The display 41 can display historical data regarding the actual stress value determined to exceed the allowable stress value in the first determination.SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping device applied to a molding apparatus such as an injection molding machine and a die casting machine, and more particularly to a mold plate that constitutes the mold clamping device.

The mold clamping device includes a fixed mold platen whose position is fixed during molding, and a movable mold platen that moves forward and backward with respect to the fixed mold platen. A fixed mold and a movable mold are attached to the fixed mold platen and the movable mold platen, respectively. Metal (die casting machine) is supplied.

For the mold clamping device, strain is measured for the purpose of normal operation.
For example, in Patent Document 1, strain gauges are attached to a plurality of locations on the back side of a fixed platen, and the strain at a plurality of locations when the mold is normally clamped is measured in advance. Use the reference value. Then, the strain is measured when the mold is clamped in the actual work, the measured strain is compared with the reference strain, and when the difference between the two exceeds the preset upper limit value, the mold clamping is determined to be defective. .
In addition, Patent Document 2 discloses an injection molding device that detects axial loads of a plurality of tie bars that constitute a mold clamping device, and generates an alarm when the variation in the load between the axes exceeds a preset tolerance for variation. Disclosed is a mold clamping anomaly detection method for a machine.
Furthermore, Patent Document 3 proposes to stop the operation of the mold clamping device when the amount of strain detected by the strain gauge provided on the stationary mold exceeds a set value below the elastic limit.

JP-A-10-291061 Japanese Patent Publication No. 1-45409 JP 2006-102783 A

According to Patent Documents 1 to 3, by detecting the stress generated in the mold clamping device, it is possible to prevent damage to the mold platens including the fixed mold platen and the movable mold platen. However, according to Patent Documents 1 to 3, excessive stress can be detected, but it is only temporary at the time of detection and does not correspond to continuous use of the mold clamping device. According to this, if the standard strain is the value of the one-shot destruction level of the material, there is a possibility that the mold plate will already be severely damaged when the actually measured strain reaches the standard strain. In this case, the molding machine must be stopped immediately. However, when the standard strain is set to a value sufficiently lower than the one-shot breakage, almost no damage to the platen occurs when the actually measured strain reaches the standard strain. However, according to Patent Documents 1 to 3, even if there is no damage to the platen, if the measured value reaches the reference value even once, a warning or the like is issued based on the detection of an abnormality. become. However, even if there is no problem such as no damage to the platen or normal operation variation of the molding machine, a warning or the like is issued each time. In this case, although the operator can leave the mold clamping device as it is, the operator has to stop the work or the molding machine one by one, which deteriorates the workability and productivity. In addition, fatigue fracture due to repeated stress is one of the failure modes of platens generally produced by casting, but the strain caused by fatigue stress, which is the cause of fatigue fracture, is sufficiently lower than single-shot fracture. value. In other words, although one aspect of fatigue failure can be recognized from Patent Documents 1 to 3, workability and productivity may be deteriorated as described above.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an apparatus capable of judging and issuing a warning prior to occurrence of fatigue failure, ie, abnormal risk of mold platens due to repeated stress.

A determination device of the present invention determines the fatigue state of a platen that constitutes a mold clamping device.
This judging device comprises a storage unit for storing history data of actual stress values measured on a mold platen, a display unit for displaying the history data of actual stress values, and a judging unit for judging the measured actual stress values. , provided.
The determination unit makes a first determination as to whether or not the measured actual stress value exceeds a predetermined allowable stress value.
The display unit can display history data regarding the actual stress value determined to exceed the allowable stress value in the first determination.

The storage unit according to the present invention preferably stores the actual number of times the actual stress value exceeds the allowable stress value after the history data is accumulated.
Also, the determination unit preferably makes a second determination as to whether or not the actual number of times exceeds a predetermined allowable number of times.
Furthermore, the display unit preferably displays a warning based on the result of the second determination by the determination unit.

The history data displayed on the display unit according to the present invention preferably includes one or both of the actual number of times and the ratio of the actual number of times to the allowable number of times.

In the determination device of the present invention, preferably, the history data is displayed on the display unit based on an external request, and the display of the warning on the display unit is performed in accordance with the allowable number of times that the actual number of times is predetermined in the second determination. This is done within a predetermined period of time after it is determined to exceed.

The mold clamping device of the present invention, the fixed mold platen that supports the fixed mold, the movable mold platen that supports the movable mold, and any of the above-described fatigue conditions of the fixed mold platen and the movable mold platen are determined. and a determination device.

According to the determination device of the present invention, past history data in which the measured stress value exceeds the allowable stress value can be displayed on the display unit. Operators and other concerned parties who refer to this display can recognize the fatigue status of the fixed platen and the movable platen based on the historical data. As a result, the parties concerned should take measures to reduce the mold clamping force in order to reduce fatigue by reducing the distortion of the fixed platen and the movable platen, check for any abnormalities, or and advance arrangements for replacement of the movable platen, etc.

It is a figure showing a schematic structure of a mold clamping device concerning an embodiment of the present invention. It is a figure which shows the structure of the control part provided with the abnormality determination function of the mold clamping device which concerns on this embodiment. FIG. 5 is a diagram showing an example of history data stored in a storage unit of a control unit; It is a figure which shows the example which extracts and displays the measured distortion amount which exceeded the allowable distortion amount from the historical data memorize|stored in a memory|storage part. It is a figure which shows the example of the visual warning display by a memory|storage part. It is a figure which shows the example of the procedure of abnormality determination by the determination part of a control part. 10 is a table showing another example of history data;

A mold clamping device 10 according to an embodiment of the present invention will be described below with reference to the accompanying drawings. As an example, a mold clamping device 10 applied to an injection molding machine will be described below.

[Mechanical configuration of mold clamping device 10: FIG. 1]
As shown in FIG. 1, the mold clamping device 10 has a fixed mold platen 12 that holds a fixed mold 14 fixed to the upper surface of one end of a base frame 11 .
A movable mold platen 13 that holds a movable mold 15 is disposed on the upper surface of the other end of the base frame 11 so as to face the fixed mold platen 12 so as to move back and forth. A guide rail 26 is laid on the base frame 11 , and a linear bearing 27 guided by the guide rail 26 supports the movable platen 13 via a pedestal 28 .

The fixed platen 12 and the movable platen 13 are provided with a first sensor 31 and a second sensor 33, each of which is a strain gauge. In FIG. 1, it is provided at a clear position, but preferably it is provided at a portion of the fixed mold platen 12 and the movable mold platen 13 that undergoes large deformation when the mold clamping device 10 is operated. For example, it is preferable that the portion of large deformation is on the diagonal line connecting the hydraulic mold clamping cylinders 18 arranged at the four corners of the fixed mold platen 12 and the movable mold platen 13 . In this case, it is preferable to provide ribs along the diagonal or parallel to the diagonal, and to provide strain gauges on the diagonal ribs. Here, the four hydraulic mold clamping cylinders 18 arranged at diagonal positions are arranged in the center of the area surrounded by these hydraulic mold clamping cylinders 18 (fixed mold 14 and movable mold 15). Since a mold clamping force for compressing these molds in the axial direction is applied from the outside of the mold, the bending strain on the diagonal line becomes the largest. For this reason, the flexural stress acting on the platen (the fixed platen 12 and the movable platen 13) is transmitted to the diagonal ribs provided along the diagonal or parallel to the diagonal. By equipping the rib with a strain gauge, it is possible to accurately detect the bending stress acting on the platen. In this example, only one first sensor 31 is provided on the fixed platen 12 and only one second sensor 33 is provided on the movable platen 13. A plurality of first sensors 31 and second sensors 33 may also be provided. The measurement of strain of the fixed mold platen 12 and the movable mold platen 13 by the first sensor 31 and the second sensor 33 can be performed continuously or intermittently.

Four hydraulic mold clamping cylinders 18 each having a small stroke and a large cross-sectional area are provided at the four corners of the fixed mold platen 12 . A tie bar 17 is connected to one side of each ram 16 that slides in a hydraulic mold clamping cylinder 18. The tie bar 17 moves toward the movable mold platen 13 when the opposing movable mold platen 13 approaches for mold clamping. It penetrates through the opened four insertion holes.
A hydraulic mechanism 35 is connected to the hydraulic mold clamping cylinder 18 . The hydraulic mechanism 35 supplies hydraulic oil to the mold clamping side chamber 18 a and the mold opening side chamber 18 b of the hydraulic mold clamping cylinder 18 based on instructions from the control device 40 .

A means for moving the movable platen 13 is composed of a ball screw shaft 25 driven by a servomotor 22 via power transmission gears 23 and 24 . The ball screw shaft 25 is installed parallel to the moving direction of the movable platen 13 and is rotatably supported by the bearing housing 20 held by the fixed platen 12 while being constrained in the axial direction. It is rotatably supported by a ball screw nut 21 held in the housing. The number of rotations and the rotation speed of the ball screw shaft 25 are controlled via the servomotor 22 by a control device (not shown).
A plurality of equally pitched ring grooves (or male threads) are formed at the tip of each tie bar 17 . A split nut 29 having a ring-shaped inner groove (female thread) that meshes with the ring groove of each tie bar 17 is provided on the side of the movable platen 13 opposite to the mold.

[Control device 40: FIGS. 1, 2, 3, 4, and 5]
The mold clamping device 10 includes a control device 40 that controls the operation and functions of the mold clamping device 10 .
As the operation of the mold clamping device 10, the movable mold platen 13 is moved in the direction of the fixed mold platen 12 from the mold open state in which the fixed mold 14 and the movable mold 15 are separated, and the fixed mold 14 and the movable mold 14 are moved. After the mold 15 is brought into close contact, this corresponds to the operation up to the completion of mold clamping in which a predetermined mold clamping force is applied. In addition, as a function of the control device 40, as well as storing the actually measured strain amount En in the mold platen in the mold clamping state after the mold clamping is completed, the fixed mold is determined based on the stored actually measured strain amount En and the allowable strain amount Et. It is determined whether or not there is a possibility that the platen 12 and the movable mold platen 13 are mechanically abnormal.

[Configuration of control device 40: FIG. 2]
As shown in FIG. 2, the control device 40 includes a display unit 41 for displaying necessary information, and an input unit 43 operated by an operator to receive inputs such as mold thickness information and mold clamping force information. Prepare. The control device 40 includes a storage section 45 for storing various information necessary for molding, an instruction section 47 for instructing each operation of the mold clamping device 10, and whether or not there is a possibility that a mechanical abnormality will occur. and a judgment unit 49 for judging whether or not. In this case, the judging section 49 is made independent of the instruction section 47 in order to clarify the presence of the judging section 49 . The control device 40 is composed of a computer device, the input section 43 is composed of soft keys or hard keys, and the display section 41 is composed of, for example, an LCD (Liquid Crystal Display).

[Storage unit 45: FIG. 3]
The storage unit 45 stores the measured strain amount En during mold clamping in each molding cycle sent from the first sensor 31 and the second sensor 33 in the mold clamping state. Measurement of the actually measured amount of strain En may be made by continuously measuring the amount of strain in the mold platen during the mold clamping process with the passage of time, or measuring only once at an arbitrary timing from the completion of mold clamping pressure rise to mold clamping pressure drop. Alternatively, a maximum value or an average value may be selected by measuring multiple times. The measured strain quantity En sent from the first sensor 31 relates to the fixed platen 12 , and the measured strain quantity En sent from the second sensor 33 relates to the movable platen 13 . Note that n is a positive integer including 0 as an example. FIG. 3 shows the actually measured strain amount En (history data) stored and accumulated in the storage unit 45 in tabular form. In order to distinguish between the fixed mold platen 12 and the movable mold platen 13, the former is indicated as the measured strain amount ΕAn, and the latter is indicated as the measured strain amount ΕBn.

The measured strain amounts ΕAn and ΕBn are stored in association with the date and time of measurement and the number of mold clamping times, as shown in FIG. The measured strain amounts ΕAn shown here are symbolized as ΕA00, ΕA01, ΕA02, ΕA03, . The strain quantity stored in may be a dimensionless value or a value with a dimension of length.
The mold clamping number is preferably the number of mold clamping pressurizations performed after the mold is closed, regardless of whether the mold clamping device 10 is operated manually or automatically. For example, in FIG. 3, the number of times of mold clamping at which the measured strain amount ΕA00 of the fixed mold platen 12 is measured is "N". This indicates that the clamping time when the actually measured strain amount ΕA00 is measured is the "N" number of mold clampings after the mold clamping pressurization is performed for the first time.

As is well known, strain is caused by applied stress. Therefore, although the actually measured strain amount En is targeted here, the actually measured stress (σn) can also be targeted. Therefore, in the present embodiment, the actual stress value includes both the measured strain amount En and the measured stress (σn). The same applies to the actually measured strain amount En, the allowable strain amount Et to be compared with the actually measured stress (σn), and the allowable stress σt, and both of them are defined as the allowable stress value.

The history data in FIG. 3 also includes results of comparing the measured strain amount ΕAn of the fixed platen 12 and the measured strain amount EBn of the movable platen 13 with the allowable strain amount Et (EAt, EBt). This comparison result indicates whether or not the measured strain amount En (EAn, EBn) exceeds the allowable strain amount Et (EAt, EBt) (En>Et). Here, the allowable strain amount Et is a reference value for determining whether or not a large strain leading to fatigue fracture has occurred in the fixed platen 12 and the movable platen 13 . In the history data, if the actually measured strain amount En exceeds the allowable strain amount Et, the comparison index is set to "1", and if the actually measured strain amount En is equal to or less than the allowable strain amount Et, the comparison index is set to "0". memorize to Determination (first determination) as to whether or not the measured strain amount (actual stress value) En exceeds the allowable strain amount (allowable stress value) Et is performed by the determination unit 49 .

The allowable strain amount Et is stored in the storage unit 45 . This permissible strain amount Et may be commonly applied to both the measured strain amount ΕAn and the measured strain amount ΕBn, or may be applied to the actual number of times TAn applied to the measured strain amount ΕAn and the measured strain amount ΕBn. TBn may be applied individually. As an example, if the difference in bending stiffness between the fixed platen 12 and the movable platen 13 is small, the common actual number of times Tn is applied. For example, individual actual numbers TAn and actual numbers TBn are applied.

The history data in FIG. 3 includes the actual number of times Tn, which is the total number of times the measured strain amount ΕAn of the fixed platen 12 and the measured strain amount EBn of the movable platen 13 exceed the allowable strain amount Et. The actual number Tn includes the actual number TAn and the actual number TBn corresponding to the fixed mold platen 12 and the movable mold platen 13, respectively. For example, in FIG. 3, the actual number TAn of the fixed platen 12 is "n" from the measured strain amount ΕA00 to the measured strain amount ΕA02. This indicates that the number of times the actually measured strain amount ΕAn exceeds the allowable strain amount Et before the actually measured strain amount ΕA00 is measured is n times. Since the determination unit 49 determines that the measured strain amount ΕA03 exceeds the allowable strain amount Et, the determination unit 49 counts up and adds "1" to the actual number Tn stored in the storage device 45 to obtain "n+1", resulting in the actual number Tn. has been updated. Similarly, it indicates that the actually measured strain amount ΕA10 exceeds the allowable strain amount Et, and "1" is added to obtain "n+2". The same applies to EBn and TBn.

The actual number of times Tn (TAn) is compared with the allowable number of times Tt, as will be described later. This allowable number of times Tt is a reference value for judging whether or not a large strain leading to fatigue fracture has occurred in the fixed mold platen 12 and the movable mold platen 13 or whether the number of times has reached a limit (second judgment). The allowable number of times Tt is stored in the storage unit 45 . The allowable number Tt may be applied in common to the actual number TAn and the actual number TBn, or may be applied separately such as the allowable number TAt applied to the actual number TAn and the allowable number TBt applied to the actual number TBn. may be applied to

In addition to the history data described above, the storage unit 45 stores information necessary for instructing the operation of driving elements of the mold clamping device 10 such as the servomotor 22 and the hydraulic mechanism 35, and other information.

[Instruction unit 47: FIGS. 4 and 5]
The instruction unit 47 reads various information stored in the storage unit 45 according to instructions and selections from the operator, and generates operation command information.
In addition, according to the instruction from the operator, the instructing unit 47 determines that the measured strain amount En exceeds the allowable strain amount Et from the history data of FIG. history data is extracted and displayed on the display unit 41 . This history data is displayed on the display unit 41 as shown in FIG. 4, for example. The operator can recognize the fatigue state of the fixed mold platen 12 and the movable mold platen 13 by referring to this history data.
Furthermore, the date and time of measurement and the number of mold clamping times stored together with the history data in the storage unit 45 are not used for evaluation of the fatigue state, but are compared with the date and time of measurement during maintenance inspections or after the occurrence of fatigue fracture. By checking the , it is possible to grasp the period required to reach the fatigue state.
Alternatively, by recognizing the fatigue state in comparison with the number of mold clamping times, it is possible to grasp the number of mold clamping times required to reach the fatigue state. If there is a large difference in the production volume for a certain period of time due to differences in the machine operating rate and production cycle, it is preferable to compare the number of times of mold clamping rather than the date and time of measurement. As a result, for example, even when the machine is stopped for a long period of time and when the operation rate is high and the production volume is high, the fatigue state can be grasped more accurately by comparing the number of times of mold clamping.

FIG. 4 shows the measured strain amount En, the comparison result with the allowable strain amount Et, and the actual number of times Tn. can also be displayed. An operator can recognize the fatigue state of the fixed mold platen 12 and the movable mold platen 13 with only one of these.

Moreover, the instruction unit 47 causes the display unit 41 to display a warning based on the determination result of the determination unit 49 described below. This warning display is displayed on the display unit 41 as shown in FIG. 5, for example. By referring to this warning display, the operator recognizes the degree of progress of the fatigue state of the fixed platen 12 and the movable platen 13 and the degree of risk of fatigue failure, This is the starting point for maintenance.
5 shows an example in which the fixed platen 12 reaches the actual number Tn or the allowable number Tt, and the movable platen 13 does not reach the actual number Tn or the allowable number Tt. Both the mold platen 12 and the movable mold platen 13 may reach the actual number of times Tn or the allowable number of times Tt.

Although FIG. 5 shows an example in which a visual warning is given by displaying a predetermined display on the display unit 41, it is also possible to provide an auditory warning via a speaker provided in the control device 40. , or just an auditory warning. Also, here, an example of issuing a warning via the control device 40 that controls the mold clamping device 10 is shown. A warning can also be displayed from the control device 40 to this centralized monitoring device through communication.

[Determination unit 49: FIG. 6]
As an example, the determination unit 49 compares the actual number of times Tn with the allowable number of times Tt based on the procedure shown in FIG. It is determined whether or not to issue a warning (second determination). A specific example of this procedure will be described in the column of molding operation after completion of mold clamping.

[Operation until completion of mold clamping: Fig. 1]
The operation up to the completion of mold clamping by the control device 40 will be described with reference to FIG.
From the state in which the stationary mold 14 and the movable mold 15 in FIG. The movable platen 13 is moved by the rotation of the ball screw shaft 25 driven by the servomotor 22 until the mold 14 and the movable mold 15 are closed. In this process, the movable mold platen 13 slowly accelerates, moves at a constant speed, and then decelerates so that the fixed mold 14 contacts the movable mold 15 .

The split nut 29 is actuated at the stop position of the movable platen 13, and the inner ring groove of the split nut 29 engages with the ring groove at the tip of the tie bar 17, thereby coupling the tie bar 17 and the split nut 29 together.

After the tie bar 17 and the split nut 29 are connected, the hydraulic mechanism 35 is operated to pressurize the mold clamping side chamber 18a of the hydraulic mold clamping cylinder 18 to perform compression mold clamping. For example, when the center of gravity of the molten resin pressure generated in the cavity is at a position lower than the center of the mold clamping device 10, as described above, the mold clamping force of the tie bars 17 on the lower side is greater than the clamping force of the tie bars 17 on the upper side. You can increase the force.
After the mold clamping is completed in this manner, molten resin is injected from the injection barrel 30 into the cavity formed by the fixed mold 14 and the movable mold 15 to mold a molded product.

[Molding operation after completion of mold clamping: Figures 1, 3, and 6]
When mold clamping is completed, the determination unit 49 obtains the measured strain amounts ΕAn and ΕBn of the fixed mold platen 12 and the movable mold platen 13 measured by the first sensor 31 and the second sensor 33 (S101 in FIG. 6). In FIG. 6, the measured strain amounts ΕAn and ΕBn are collectively written as the measured strain amount En. The same applies to other allowable strain amounts EAt, EBt, and the like.

After acquiring the measured strain amounts ΕAn and ΕBn, the determination unit 49 compares the magnitude relationship with the allowable strain amounts EAt and EBt (Fig. 6 S103, first determination). If the measured strain amounts ΕAn and EBn are respectively larger than the allowable strain amounts EAt and EBt (Y in FIG. 6 S103), the measured strain amounts ΕAn and EBn are stored in the storage unit 45 in association with being larger than the allowable strain amounts EAt and EBt. is stored (S105 in FIG. 6). The accumulation of stored data is as shown in FIG. 3, where the comparison index "1" in FIG. 3 represents association. If the measured strain amounts ΕAn and ΕBn are equal to or less than the allowable strain amounts EAt and EBt, respectively (S103 N in FIG. 6), the measured strain amounts ΕAn and ΕBn are stored in the storage unit 45 without being associated. The judging unit 49 continuously compares the newly obtained measured strain amounts ΕAn, ΕBn and the allowable strain amounts EAt, EBt, and stores the comparison results in the storage unit 45 in the same manner as described above (FIG. 6). S101, S103, S105). If the storage device 45 has a sufficiently large capacity, the measured strain amounts ΕAn and EBn may be stored in the storage unit 45 even when the measured strain amounts ΕAn and ΕBn are equal to or less than the allowable strain amounts EAt and EBt.

The determination unit 49 counts the actual number of times TAn, TBn of the actually measured strain amounts ΕAn, ΕBn larger than the allowable strain amounts EAt, EBt (S107 in FIG. 6). The results of counting are as shown in the column of actual number of times Tn in FIG.
After counting the actual numbers TAn and TBn, the determination section 49 compares the allowable numbers TAt and TBt stored in the storage section 45 with the magnitude relationship (Tn>Tt) (S109 in FIG. 6, second determination). If the actual numbers TAn and TBn exceed the allowable numbers TAt and TBt (Y in FIG. 6 S109), the instruction section 47 is notified to display a warning on the display section 41 (S111 in FIG. 6). Based on this notification, the instruction unit 47 displays the warning shown in FIG. 5 on the display unit 41, for example.
The above procedure (S101 to S111) is continued until a predetermined molding cycle is completed (S113 Y).

[effect]
The mold clamping device 10 described above has the following effects.
The mold clamping device 10 can display on the display unit 41 past history data in which the measured strain amount En exceeds the allowable strain amount Et. An operator and other concerned parties who refer to this display can recognize the fatigue status of the fixed platen 12 and the movable platen 13 based on the historical data. As a result, the concerned parties can take measures to reduce the mold clamping force in order to reduce fatigue by reducing distortion of the fixed mold platen 12 and the movable mold platen 13, check for abnormalities, or Maintenance preparation for the mold clamping device 10 such as prior arrangement for replacement of the fixed platen 12 and the movable platen 13 can be performed without neglect.

Further, the mold clamping device 10 issues a warning that fatigue fracture may occur in the fixed mold platen 12 and the movable mold platen 13 based on the determination of whether the actual number of times Tn or the allowable number of times Tt has been reached. Those concerned who refer to this warning take measures to reduce the mold clamping force in order to reduce fatigue by reducing the distortion of the fixed platen 12 and the movable platen 13, and Since it is possible to check whether or not the fixed platen 12 and the movable platen 13 are replaced, it is possible to prevent fatigue failure from actually occurring in the fixed platen 12 and the movable platen 13 .

In addition to the above, the configurations described in the above embodiments can be selected or changed as appropriate without departing from the gist of the present invention.
The configuration of the mold clamping device 10 is merely an example. The drive mechanism for mold closing and mold opening of the present invention is not limited to this. For example, a toggle link mechanism may be used to close and open the mold.

The strain data (FIG. 3) stored in the storage unit 45 may include other data. For example, as shown in FIG. 7, in addition to the actual number Tn, the ratio of the actual number Tn to the allowable number Tt can be included. Then, this ratio can be displayed on the instruction unit 47 as past history data. Operators and other interested parties viewing this ratio display are more likely to intuitively perceive the time period until the allowable number of times is reached.

The history data based on the strain data stored in the storage unit 45 can be displayed on the display unit 41 in addition to the operator's instructions. For example, it can be displayed arbitrarily in terms of time, such as displaying before the mold closing operation starts, displaying at a specific time, or the like.

The strain data stored in the storage unit 45 includes the measured strain amount En, and the stress can be obtained directly from the strain according to Hooke's law. Therefore, the measured strain amount En of the strain data may be replaced with the measured stress (σn), or the strain data may include both the measured strain amount En and the measured stress (σn). When the measured stress (σn) is included, the allowable stress (σt) is prepared, and the measured stress (σn) and the allowable stress (σt) are compared.

Although the risk of fatigue fracture can be evaluated by a known fatigue evaluation method, it is particularly preferable to evaluate by the linear cumulative damage rule (minor rule). Since the mold clamping force usually varies depending on the molded product, the mold clamping force (distortion amount of mold platen) generated at the time of mold clamping changes when the molded product changes. In this case, some molded products have a large amount of mold platen strain, while other molded products have a small amount of platen strain. Fatigue failure does not only occur when the maximum stress value generated in the load history during operation exceeds the fatigue limit, but also when the repeated operation occurs in a state where the peak value of the repeated stress fluctuates. Even if there is, fatigue fracture progresses. In this case, if the degree of fatigue is evaluated only by the number of times the maximum stress value reaches the fatigue limit value in the stress history, there is a possibility that the degree of progression of fatigue fracture may be misdiagnosed. Therefore, instead of setting the allowable stress value corresponding to the maximum stress value generated in the load history and the allowable number of times as constant values, the linear cumulative damage law is used to accumulate the actual stress value that fluctuates irregularly, and the fatigue damage degree is calculated. , it is possible to accurately predict the life to fatigue failure.

10 Mold clamping device 11 Base frame 12 Fixed mold platen 13 Movable mold platen 14 Fixed mold 15 Movable mold 16 Ram 17 Tie bar 18 Hydraulic mold clamping cylinder 18a Mold clamping side chamber 18b Mold opening side chamber 20 Bearing box 21 Ball screw nut 22 Servo motor 23 Power transmission gear 25 Ball screw shaft 26 Guide rail 27 Linear bearing 28 Pedestal 29 Split nut 30 Injection barrel 31 First sensor 33 Second sensor 35 Hydraulic mechanism 40 Control device 41 Display unit 43 Input unit 45 Storage unit 47 Instruction unit 49 Judgment Part En, ΕAn, ΕBn Measured strain amount Et, EAt, EBt Allowable strain amount Tn, TAn, TBn Actual number of times Tt, TAt, TBt Allowable number of times

Claims (5)

A device for determining the fatigue state of a mold platen constituting a mold clamping device,
a storage unit for storing history data of actual stress values measured on the platen;
a display unit for displaying history data of the actual stress values;
A determination unit that determines the measured actual stress value,
The determination unit is
making a first determination as to whether the measured actual stress value exceeds a predetermined allowable stress value;
The display unit
In the first determination, the history data related to the actual stress value determined to exceed the allowable stress value can be displayed.
The mold plate determination device characterized by:
The storage unit
storing the actual number of times the actual stress value exceeds the allowable stress value after the history data is accumulated;
The determination unit is
making a second determination as to whether or not the actual number of times exceeds a predetermined allowable number of times;
The display unit
Displaying a warning based on the result of the second determination by the determination unit;
The determination device according to claim 1.
The history data displayed on the display unit is
3. The determination device according to claim 2, comprising one or both of the actual number of times and a ratio of the actual number of times to the allowable number of times.
Display of the history data on the display unit is performed based on an external request,
The display of the warning on the display unit is performed within a predetermined period after it is determined in the second determination that the actual number of times exceeds the predetermined allowable number of times.
The determination device according to claim 2 or 3.
a stationary platen that supports the stationary mold;
a movable platen that supports the movable mold;
a determination device according to any one of claims 1 to 4, which determines the fatigue status of the fixed platen and the movable platen;
A mold clamping device characterized by:

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