JPH0145409B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold clamping abnormality detection method for an injection molding machine, which attempts to detect abnormalities in the mold clamping state during mold clamping of an injection molding machine.

In an injection molding machine, the fixed mold and movable mold approach each other during the mold closing process, from when the guide pin begins to fit into the guide pin hole provided in the other mold until both molds come into close contact. , During the mold clamping process after the molds are brought into close contact, and during the mold opening process of both molds from the mold clamping state, the contact surfaces of both molds remain parallel to each other and do not shift in the vertical and horizontal directions. It is necessary.

If this requirement is violated, a bending load is applied to the guide pin or boss pin for forming a hole in the molded product, causing breakage, or uneven wear of the guide pin or guide bush of the mold.

Therefore, in the injection molding process, the parallelism between both contact surfaces (free parallelism) until the two molds come into contact is
The parallelism when the two molds come into contact (parallelism when the molds touch) is important.

Also, when molten resin is injected into the mold with the mold closed, the mold clamping force is set to be greater than the force used to push the mold open with this resin pressure, but the Due to variations in the cross-sectional area, that is, the distribution of its projected area, the parallelism of the mold plate during injection varies, resulting in variations in the dimensions of the molded product in the mold clamping direction.

This kind of problem can also occur if the amount of extension of the four tie bars during mold clamping is not constant, that is, if the clamping force by each tie bar is not uniform, the force relationship between the clamping force and the resin pressure inside the mold may be affected. This also occurs due to variations in

In this way, from the perspective of protecting the mold and maintaining the accuracy of molded products, equalization of parallelism and tightening is important, and in the past, parallelism and variations in the amount of extension of tie bars during mold clamping were strictly controlled. Also, consideration has been given to making the projected area of the cavity uniform.

However, even with such strict controls,
It is inevitable that the clamping accuracy of the mold clamping device and the parallelism of the mold will deteriorate due to wear of each member due to long-term use and local overload due to incorrect operation.

Of course, it is possible to maintain the precision of the mold clamping device and the mold to some extent through careful daily maintenance and checking of the operating condition, but this is difficult to do satisfactorily at actual molding sites where production deadlines are tight.

Conventionally, to manage the accuracy of mold clamping devices and molds, the parallelism of the mold platen is measured, but depending on the size of the mold, it is necessary to adjust the detection distance or move the detection position. This method has disadvantages in that it is not possible to accurately reflect the contact state at the contact surface of the mold due to the elastic deformation of the fixed platen, movable platen, and mold. In addition, as shown in Japanese Utility Model Publication No. 35-27698, there is a method that detects the tightening pressure as elongation of the tie rod with a dial indicator via a pin and auxiliary rod inserted into the through hole of the tie rod. It is difficult to ensure detection accuracy and has the disadvantage of reducing the strength of the tie rod, so it is only used in some cases as a guideline.

The present invention was developed to solve these problems.A strain gauge is fixed to the surface of each tie bar to detect the axial load, and the variation between the axes is determined by a preset variation tolerance value. When the limit is exceeded, an alarm is issued, making it easier to control the accuracy of the mold clamping device and mold, enabling long-term molding of good molded products, and extending the life of the mold clamping device and mold. It was created so that it can be done.

This will be explained in detail with reference to the drawings.

In Figures 1 and 2, 1 is a fixed plate, 2 is a movable plate, 3 is a fixed mold, 4 is a movable mold, 5 is a tie bar, 6 is a mold clamping cylinder, and 7
indicates a toggle mechanism, 38 indicates an end housing,
8 is tie bar nut, 9 is cylinder rod, 39
is an injection device. It should be noted that although a toggle device 7 is shown as one embodiment, a direct pressure mold clamping device may also be used.

Since the tie bars 5, 5, 5, 5 mentioned above are connected to the fixed platen 1, if the mold contact surface is divided into four parts, top, bottom, left and right, each part has a The tie bars 5 are tightened and separated with the same force as the axial load generated on the closest tie bar 5. In other words, uneven mold thickness, poor parallelism of the molds, and poor accuracy of the mold clamping device appear as variations in the axial load of the tie bars 5.

Therefore, by detecting the axial load of each tie bar and knowing its variation, it is possible to detect variations in the clamping force or separation force of each part of the mold, and also to detect abnormalities in the tightening or separation state. Can be detected.

That is, the presence or absence of an abnormality in mold tightening or separation is determined from the variation value of the axial load of the tie bars 5, 5, 5, 5, and an alarm is issued in the event of an abnormality.

Further, the specific method will be explained based on FIG. 1, FIG. 2, and FIG. 3.

As shown in Fig. 2, strain gauges 10, 10, 10, 10 are fixed in the axial direction of the tie bars 5 at four locations on the top, bottom, left and right on the surface of the four tie bars 5 near the fixed plate 1 to detect the load. do.

A cover 11 provided on the outside of the strain gauge 10 protects the strain gauge 10 and its lead wires (not shown).

The lead wire of the strain gauge 10 is connected to the load indicator 1 of the abnormality alarm unit 19 shown in FIG. 1 via the terminal 12 provided on the cover 11 and the connection cable 13.
Connect to 4. As shown in the figure, load indicator 1
4 is connected to an alarm device 17 via a comparator 16. Reference numeral 15 denotes a tolerance value setter connected to the comparator 16.

Reference numeral 18 denotes an external output terminal connected to the alarm device 17, which can be connected to a central monitoring device or the like (not shown).

A specific example of the abnormality alarm unit 19 shown in FIG. 3 will be explained.

Digital setting devices 26 and 29 are tolerance value setting device 15
belongs to

Detection process selection dial 25, digital display 2
1, 22, 23, 24, 27, 28, green lamps 30, 32, 34, and red lamps 31, 3
3 and 35 belong to the load indicator 14.

The comparator 16 is housed inside the unit 19 and is not shown in the figure. .

The detection process setting dial 25 is used to set the process of detecting the load, and the processes are a mold touching process, a mold clamping process, an injection process, and a mold release process.

Note that the timing of these detections is given by a signal from an electric control device (not shown) of the injection molding machine, and can be easily changed depending on the characteristics of the injection molding machine, the mold, and the molded product.

In addition, the measurement of the axial load applied to the tie bar 5 is as follows:
It is desirable to use absolute values, but in reality it is not possible to maintain a zero load comparison signal for a long period of time, so
The amount of strain detected at the time when both molds 3 and 4 are fully opened is assumed to be zero load, and is used as a comparison reference value for each detection process.

The digital displays 21, 22, 23, 24 are the upper and lower parts of the tie bar 5 on the operation side, the upper part on the non-operation side,
Displays the axial load at the bottom numerically.

The digital displays 28 and 27 respectively show the actual average load of the axial load applied to the four tie bars 5, 5, 5, 5, and the amount of variation in the load applied to the four tie bars 5, 5, 5, 5. That is, the difference between the maximum value and the minimum value (hereinafter referred to as the actual dispersion value) is expressed numerically.

The digital setting device 26 is for setting an allowable value for the actual variation value, and the green lamp 32 lights up when the actual variation value is less than the allowable value. The red lamp 33 lights up when the permissible value is exceeded, and also sounds the buzzer of the alarm 17.

The green lamp 30 of each digital display 21, 22, 23, 24 indicates that the difference between each axial load displayed on each display and the average value of the load shown on the digital display 28 is due to the variation in the digital setting device 26. It lights up when it is less than half of the allowable value, and when it is larger than that, the red lamp 31 lights up and issues an alarm.

The digital setting device 29 is for setting the standard value of the axial load of each tie bar 5, and the digital setting device 29 is for setting the reference value of the axial load of each tie bar 5.
The difference from the actual average load shown in 8 is the difference between the digital setting device 2
When the variation is less than half of the tolerance value of 6, the green lamp 34 lights up, and when it is larger than that, the red lamp 35 lights up to issue an alarm.

Next, the actual operating state will be explained.

Set the detection process selection dial 25 to the "mold clamping" process position.

The amount of strain on the strain gauge 10 caused by the axial load on each tie bar 5 is transmitted to the load display 14,
The strain amount difference between the strain amount when the mold is opened and the strain amount when the mold is opened is calculated instead of the strain amount when the load is zero, and the average value of the strain amount difference detected by each of the four strain gauges 10 of each tie bar 5 is converted. The calculated load value is displayed on the digital displays 21, 22, 23, 2 as the axial load of each tie bar.
4, 101.4ton, 99.8ton, 107.0ton, 98.1ton are displayed.

Among them, the maximum value is 107.0 tons, the minimum value is 98.1 tons, the difference is 8.9 tons, and the average value is 101.6 tons.

The difference value of 8.9 tons is displayed on the digital display 27 as an actual variation value, and the average value of 101.6 tons is displayed on the digital display 28 as an actual average load.

Further, since the actual variation value of 8.9 tons is smaller than the variation tolerance value of 10 tons of the digital setting device 26, the green lamp 32 is lit.

This indicates that there is no abnormal variation in the axial load of each tie bar 5, that is, there is no abnormality in the distribution of mold clamping force, but if the actual variation value is
If it exceeds 10 tons, the red lamp 33 lights up and the buzzer of the alarm 17 sounds.

The difference of 1.6 tons between the standard load of 100.0 tons on the digital setting device 29 and the actual average value of 101.6 tons is the variation tolerance.
Since it is smaller than 5.0 tons, which is half of 10.0 tons, the green lamp 34 lights up.

This indicates that the difference between the standard load and the actual average load is not abnormal, that is, a predetermined mold clamping force is being generated. However, if the difference is greater than 5.0 tons, the red lamp 35 will light up. Lights up to notify you of an abnormality.

Furthermore, digital displays 21, 22, 23, 2
4 each tie bar axial load and actual average load 101.6ton
The difference is 0.2 tons at the upper part of the operation side and
1.8ton, 5.4ton at the top on the non-operating side, 3.5ton at the bottom
When these values are smaller than half of the variation tolerance value of 10 tons, that is, the green lamp 30 lights up at the three positions of the operating side upper part, the same lower part, and the non-operating side lower part, indicating that there is no abnormality, and the variation tolerance value is exceeded.
A red lamp 31 lights up on the upper part of the non-operation side that is larger than half of 10.0 tons.

This indicates that the mold clamping force at this position is different from the other three positions, that is, there is an abnormality in the tie bar 5 or other mold clamping mechanism at this position, or in the mold itself.

By setting the detection process selection dial 25, the same operation can be performed in each process such as "mold touch", "injection", and others. The selection is made depending on the purpose of abnormality detection and the molding method, and it can also be operated at two or more process positions at the same time.

In the above embodiment, as a method for detecting the load applied to the tie bar 5, four strain gauges 1 are attached to the tie bar 5.
0 is fixed, but this is because when a bending load is applied to the tie bar 5, the average is taken at four locations on the same cross section in order to prevent errors caused by the position of the strain gauge 10. Therefore, when the influence of bending is small, a single strain gauge 10 is sufficient.

Alternatively, the displacement of a certain distance on the tie bar 5 may be detected not necessarily by the strain gauge 10 but by a contact type length measuring device such as a dial gauge, or an optical or magnetic length measuring device. , it may be converted into a load.

In addition, in the embodiment, it is possible to display the reference load, actual average load, and load of each tie bar 5, which facilitates visual checking of the load condition and increases reliability as an abnormality warning device. It is. However, this can be omitted if necessary. In this case, the device can be made compactly and inexpensively.

The effect will be explained.

According to the present invention, the variation in the axial load generated in the four tie bars is detected, and when the variation exceeds three preset variation tolerance values, three types of alarms are issued, each of which can be identified separately. Therefore, by periodically checking the clamping state of the mold clamping device, the accuracy of the mold clamping device can be easily controlled.

In addition, when replacing a mold, the accuracy of the mold can be immediately determined, which prevents damage to the mold clamping device and molding defects.Also, when molding with the same mold for a long period of time, Deterioration of tightening accuracy over time can be detected and used to repair molds and mold clamping devices, and to prevent molding defects.

In addition, when continuously molding the same part, it is possible to detect shot-to-shot fluctuations in the mold clamping state, that is, the effects of fluctuations in equipment other than the mold clamping equipment, such as injection molding equipment and mold cooling equipment. Anomalies can be monitored indirectly.

Further, if the method of the present invention is used when assembling or repairing a mold clamping device, adjustment work can be performed more quickly and accurately.

[Brief explanation of drawings]

FIG. 1 is a front view of an apparatus for carrying out the method of the present invention;
FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 3 is a front view of the abnormality alarm unit. 5... Tie bar, 21, 22, 23, 24... Digital display, 25... Detection process setting dial, 26
...Digital setting device, 27...Digital display device.

Claims (1)

[Claims] 1. Detect the axial load on each tie bar and display it on the digital display, set the allowable value of actual variation in the load applied to the tie bar with the digital setting device, and set the axial load shown on the digital display. An alarm is issued when the actual variation value exceeds the allowable value, and the alarm is issued when the difference between each axial load shown on the digital display and the average value of the load is greater than half of the actual variation allowable value on the digital setting device. A different type of alarm that can be identified separately is issued, and each of the above alarms is issued when the difference between the reference value of the tie bar axial load and the actual average load shown on the digital display is more than half of the actual variation allowable value on the digital setting device. A method for detecting a mold clamping abnormality in an injection molding machine that issues different types of alarms that can be identified separately. 2. The axial load of the tie bar is detected in each of one or more predetermined steps among the mold touching step, mold clamping step, injection step, and mold release step of the injection molding machine, as described in claim 1. A method for detecting mold clamping abnormalities in injection molding machines.