JPS60115418A - Detection of defects in mold clamping in injection molding machine - Google Patents

Abstract

PURPOSE:To simplify the accurate control of a mold clamping device and a mold and to elongate the service life of the mold by a method wherein the axial load of each tie bar of an injection molding machine is detected and when the dispersion between the axial loads exceeds the preset allowable value of dispersion, an alarm is issued. CONSTITUTION:A strain gage 10 is fixed in the axial direction of each tie bar 5 at four places upper and lower, right and left on the surface near the fixed block 1 for four tie bars 5 to detect the load of each bar 5. The lead wire of each strain gage 10 is connected with the load surface device 14 of the defective-alarm unit 19 and further with the alarm device 17 through the comparison arithmetic unit 16. The allowable value presetting device 15 is connected with the comparison arithmetic unit 16.

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 by checking the mold clamp 1 of an injection molding machine.

In an injection molding machine, the fixed mold and the movable mold come close to each other, and the mold closing process begins when the guide bin begins to fit into the guide bin hole provided in the other mold and the two molds come into close contact. During the mold clamping process after the molds are brought into close contact with each other, 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 that there be no.

If this requirement is violated, a bending load will be applied to the guide bin or the boss bin used to form the hole in the molded product, resulting in breakage or uneven wear of the guide bin or guide bushing of the mold.

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

If you inject molten resin into the mold with the mold clamped, the mold clamping force is set to be greater than the force used to push the mold open with this resin pressure, but the cavity Due to the variation in the cross-sectional area of , 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 of each quiver is not uniform, the force between the clamping force and the tree finger pressure inside the mold Similar problems are occurring due to variations in relationships.

In this way, from the perspective of protecting the mold and maintaining the precision of molded products, equalization of parallelism and tightening is important, and traditionally, parallelism and variations in the amount of elongation of tie bars during mold clamping have been strictly controlled. However, consideration has been given to making the projected area of the cavity uniform.

However, even with such strict control, the clamping accuracy of the mold clamping device and the parallelism of the mold may deteriorate due to wear of each member due to long-term use or local overload due to incorrect operation. A decline is inevitable.

Of course, it is possible to maintain the accuracy of the mold clamping device and mold to some extent through careful daily maintenance and checking of the operating condition.
It is difficult to fully implement this method 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, hexagram, and mold.

(3) The present invention was developed to solve this problem, and detects the axial load of each tie bar, and when the variation between the axes exceeds a preset variation tolerance, By setting off an alarm, it is possible to easily control the accuracy of the mold clamping device and the mold, to enable molding of good molded products for a long period of time, and to extend the life of the mold clamping device and the mold. It was invented as such.

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, (+7) is a toggle mechanism, (3B) is an end housing, (8) is a tie bar nut, and (9) is a cylinder rod. , (v'9) is an injection device. Note that this embodiment is only shown as having a toggle mechanism (7), and a direct pressure mold clamping device may also be used.

The above-mentioned swivel (5) (5) (5) (5) is a fixed plate (
1), so the mold contact surface can be moved up, down, left and right.
When divided into two parts, each part will be tightened and separated by a force equal to the axial load generated on the tie bar (5) closest to it, as shown in FIG. In other words, uneven mold thickness or poor parallelism of the molds, or poor precision of the mold clamping device appears 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 separating force of each part of the mold, as well as abnormalities in the tightening or separating state. The power to do '5 is possible.

In other words, the presence or absence of an abnormality in mold tightening or separation is determined based on the variation value of the high 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, the fixed plate of the four tie bars (5) (
1) On a nearby surface, place strain gauges (10
) (10) (lO) (lo) is fixed in the axial direction of the tie bar (5) and the load is detected.

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

The lead wire of the strain gauge (10) is connected to the load indicator (14) of the abnormality alarm unit (19) shown in Figure 1 through the terminal yb (12) provided on the cover (11) and the connection cape ν (13). Connecting. As shown in the figure, the load indicator (
14) is connected to an alarm device (17) via a comparator (16). (15) is a tolerance value setter connected to the comparator (16).

(18) is an external output terminal connected to the alarm (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.

The digital setting device (26) (29) is the tolerance setting device (15).
).

Detection process selection diagram IL/(25), digital display (
21) (22) (23) (2f), (27) (2B),
The green lamps (30) (32) (34) and the red lamps (sx) (33) (3δ) are the load indicators (14).
belongs to

The comparison calculator (16) is housed inside the same 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.

It is desirable to measure the axial load applied to the trench tie bar (5) using absolute values, but in reality it is not possible to maintain a comparison signal with zero load for a long time, so both molds C3) (4)
) is the most open and the detected strain amount when the mold opening is completed is considered to be zero load and is used as the comparison standard value for each detection process.

Digital displays (21), (22), (23), and (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 display (2B) (27) shows the actual average load of the axial load applied to the four tie bars (5) (5) (5) (5) and the four wooden tie bars (5) (5), respectively. (5)(
5'>, that is, the difference between the maximum value and the minimum value (hereinafter referred to as the actual variation value) is shown numerically.

The digital setting device (26) is used to set the allowable value of the actual variation value, and the green lamp (32) lights up when the actual variation value is less than the allowable value. Red lamp (33)
lights up when the allowable value is exceeded, and an alarm (
near) sounds the buzzer.

The green lamp (30) of each digital display (21) (22) (23) (24) indicates the load in each axial direction displayed on each display and the average value of the load indicated on the digital display (28). It lights up when the difference is less than half of the tolerance value of the digital setting device (26), and when it is larger than that, the red light (3) lights up.
1) is lit.

The digital setting device (29) is for setting the reference value of the axial load of each tie bar (5), and the digital display (28)
When the difference from the actual average load indicated by is less than half of the allowable variation value of the digital setting device (29), the green lamp (34) lights up, and when it is larger than that, the red lamp (35) lights up.

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), and the amount of strain at the time of mold opening is compared with the amount of strain at the time of mold opening, which is replaced by the amount of strain at zero load. The difference in amount is calculated, and the load value obtained by converting the average value of the difference in strain amount detected by each of the four strain gauges (10) of each tie bar (5) is calculated as the axial load of each tie bar. 101.4 on the digital display (2 units) (22) (23) (24)
ton, 99.8 ton, 107.0 to
It is displayed as 98.1 ton.

Among them, the maximum value is 107. Q ton , minimum value 98.
1 ton, the difference is 8.9 ton, and the average value is IQl, 6 ton.

The difference value B0g ton is displayed on the digital display (27) as the actual variation value, and the average value 101.6 ton is displayed on the digital display (28) as the 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) lights up.

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. However, if the actual variation value exceeds 1 Qton, the red light ( 33) lights up and the alarm (11) buzzer sounds.

Standard load lQO, Q ton of digital setting device (29)
The difference between the actual average value of 101.6 ton and the actual average value of 1.6 ton is the variation tolerance of 10; 0 ton O half (7) rs,
Since it is smaller than ot, on, the green lamp (34) lights up.

This means that the difference between the standard load and the actual average load is not abnormal.
That is, it indicates that a predetermined mold clamping force is being generated, but if the difference is greater than 5.0 tons, a red lamp (35) lights up to notify the abnormality.

Furthermore, digital display (ax) (2g) (gF) (p
4) Each tie bar axial load and actual average load 101.6
The difference is 0.2 ton at the upper part of the operating side, 1.8 ton at the lower part, 5.4 tofl at the upper part of the non-operating side,
3.5 tons at the bottom, and when these values are less than half of the allowable variation value lQ ton, the green lamp (3o) lights up at the three positions of the operating side upper, the same lower, and the non-operating side lower, indicating an abnormality. The red lamp (31) lights up at the upper part of the non-operation side where the variation is larger than half of the allowable variation value of 10.0 ton.

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 credit mold clamping mechanism of the tie bar (5) at this position, or in the mold itself.

By setting the detection process selection dial (25), "mold touch", "injection", and other processes can be similarly activated. The selection is made depending on the purpose of abnormality detection and the forming blade method, and it is also possible to operate in two or more 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 (10) are attached to the tie bar (5).
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 to prevent errors caused by the position of the strain gauge (10'). , Therefore, when the influence of bending is small, a single strain gauge (1o) is sufficient.

In addition, the displacement of a certain distance on the tie bar (5) can be measured not necessarily by using a strain gauge (lo), but also by using a contact type length measuring device such as a dial gauge, or an optical or magnetic length measuring device. You can also detect it and convert it into a load.
.

In addition, in the embodiment, it is possible to display the standard load, actual average load, and load of each tie bar (5), but this makes it easier to check the load status with a glance, and improves reliability as an abnormality warning device. It's expensive. However, this can be omitted if necessary. In this case, the device can be made compactly and inexpensively.

Also, green lamp (3o)lz) (3a') red lamp (
31), (33), and (35) can be similarly omitted, and the lighting criteria for the red lamps (31) and (35) can also be changed.

A yellow lamp may be provided to indicate an intermediate range between the green lamp (30) (32') 04) and the red lamp (31) (33) (35).

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 a preset variation tolerance value, an alarm is issued. By checking the tightening state of the tightening device, the accuracy of the 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 failure of the molding element (12), and also prevents molding with the same mold for a long period of time. Even in cases where tightening accuracy deteriorates over time, it can be used to repair molds and mold clamping devices, and to prevent molding defects.

・When continuously molding the same part, it is necessary to detect shot-to-shot fluctuations in the mold clamping state, i.e., the effects of fluctuations in equipment other than the mold clamping equipment, such as the injection equipment and mold cooling equipment, and at the same time detect them. It is possible to indirectly monitor equipment abnormalities.

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 line A--A in FIG. 1, and FIG. 3 is a front view of an abnormality alarm unit. 5..11-tie bar 21,22.23.2411.
-Digital indicator 25...Detection process setting dial 26...Digital setting device 2'7...Digital display (15)

Claims (2)

[Claims] (1) A mold clamping abnormality detection method for an injection molding machine that detects the axial load of each tie bar and issues an alarm when the dispersion between the axes exceeds a preset dispersion tolerance. (2) A method for detecting a mold clamping abnormality in an injection molding machine according to claim 1, wherein the axial load of the tie bar is detected every two or more predetermined processes by 11 of the injection molding machine.