JPH02188223A - Protective method of mold and its device in injection molding machine - Google Patents

Abstract

PURPOSE:To protect a mold reliably by early detecting pinching-in of a foreign matter into the mold, by giving an alarm when mold clamping pressure arrives at an established value by making use of a phenomenon where mold clamping pressure is raised. CONSTITUTION:When a foreign matter such as a runner or flashes are stuck to a parting line of molds 6, 7 after passing through a movable platen position detecting sensor 28, a movement of a movable platen 5 is controlled prior to completion of a mold clamping process. In this instance, the molds 6, 7 are not in touch with each other. Therefore, a contact detecting sensor 27 is not actuated and a relay 24 is in a closed state. On the one hand, when the movement of the movable platen 5 is controlled like this, mold clamping pressure P acted upon a rear chamber 9a of a mold clamping cylinder 9 is raised. The pressure P is detected by a pressure detector 19 and applied to a comparator 20. When the pressure P is raised up to foreign matter detecting pressure PA calculated with an operating device 21, a signal through a comparator 20 is put out, an alarm generator 25 raises an alarm and a directional control valve 12 is changed over to a neutral position and mold clamping is suspended.

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a method and device for protecting a mold in an injection molding machine, and particularly in the case where a foreign object is caught between the molds during the mold closing process. The present invention relates to a mold protection method and device.

(b) In conventional injection molding machines, the molded product is produced by retracting the movable platen from the fixed platen side, and separating the movable mold attached to the movable platen from the fixed mold attached to the fixed platen. taken out by Therefore, during the next molding, it is necessary to close and further clamp the molds. In that case, runners, various banners, etc. formed in the previous molding process may adhere to the dividing surface of the mold. If the mold is clamped with such foreign matter still attached to the mold dividing surface, a large load will be applied to a portion of the mold, resulting in damage to the mold.

Conventionally, the actual mold closing pressure applied to the mold clamping mechanism is continuously detected during the mold assembly process before the mold clamping process, and an alarm is issued when the mold closing pressure reaches a set value. The molds in injection molding machines were protected by emitting .

(c) Problems to be solved by the invention However, in the case of such a mold protection method, as shown in FIG. 2, the mold closing pressure increases not only when a foreign object is caught; Mold closing pressure may also increase due to loads such as guide pins of the mold.

The present invention aims to solve these problems.

(d) Means for solving the problem In order to achieve this objective, the method of the present invention uses the actual mold closing pressure acting on the mold clamping machine tlI8 during the mold closing process before the mold clamping process. It continuously detects a predetermined range and issues an alarm when the mold closing pressure reaches the preset value.

In addition, the mold protection device that implements the method includes a pressure detector 19 that detects the actual mold closing pressure and force applied to the mold clamping mechanism 8 during the mold closing process before the mold clamping process, and a mold protection device that detects the actual mold closing pressure and force applied to the mold clamping mechanism 8. A movable platen position detection sensor 28 that determines the starting position of closing pressure detection, a contact detection sensor 27 that determines the detection completion position, and a calculator 21 that calculates the foreign object detection pressure that is estimated to be when a foreign object is caught between the molds. A comparator 20 that compares the mold closing pressure and the foreign object detection pressure and generates an output signal when the values match, and an alarm generator 25 & that generates an alarm upon receiving the output signal from the comparator 20. We are prepared.

(e) During the operation mold closing process, while the movable block 5 is in a state of moving toward the fixed plate without resistance, the load pressure on the mold clamping mechanism required to move the movable plate is relatively low. If resistance is applied during movement of the movable platen, such as when a foreign object is caught, the mold closing pressure acting on the mold clamping mechanism increases. However, the mold closing pressure increases not only when a foreign object is caught, but also due to loads such as guide bins of the mold.

Therefore, a movable platen position detection sensor and a contact detection sensor are installed to set the mold protection range, and an alarm is issued when the mold closing pressure becomes larger than the predetermined pressure level within the mold protection range. By appropriately determining the set value, it is possible to detect that a foreign object is caught between the molds. If the mold closing operation is stopped at that time, excessive load is prevented from being applied to the mold, and the mold is protected.

Further, by configuring the mold protection device as described above, the method can be easily implemented. Moreover,
Since a calculator is used to calculate the foreign object detection pressure, it is possible to easily adapt to changes in the operating conditions of the injection molding machine.

(f) Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a mold protection device for an injection molding machine according to the present invention. As is clear from this figure, the injection molding machine 1 includes a fixed platen 2 and an end housing 3 arranged to face the fixed platen. These fixed platen 2 and end housing 3 have multiple diepers 4.
A movable platen 5 is supported by the diameter plate 4 so as to be movable forward and backward relative to the fixed platen 2.

Then, the fixed mold 6 is attached to the fixed platen 2, and the movable platen 5
A movable mold 7 is attached to the movable mold 7.

The movable platen 5 is moved back and forth by a mold clamping mechanism 8. In this embodiment, the mold clamping mechanism 8 is of a direct pressure type. That is,
The mold clamping machine 1148 includes a mold clamping cylinder 9 fixed to the end housing 3 and a mold clamping ram 10 driven by the mold clamping cylinder 9. The movable platen 5 is fixed to the front end of the mold clamping ram 10.

Hydraulic oil discharged from a hydraulic pump 11 is supplied to the mold clamping cylinder 9 via an electromagnetic directional switching valve 12 . By moving the spool to the left, the direction switching valve 12 sends the hydraulic oil from the hydraulic pump 11 to the 1 & chamber 9a of the mold clamping cylinder 9, and also transfers the hydraulic oil in the front chamber 9b of the mold clamping cylinder 9. tank 1
3 and move the spool to the right, the hydraulic oil from the hydraulic pump 11 is sent to the front chamber 9b of the mold clamping cylinder 9, and the hydraulic oil tank 13 in the rear chamber 9a is sent.
It is assumed that it will be returned to. Moreover, when the spool is placed in the neutral position, each oil passage is cut off.

Therefore, when the directional control valve 12 is switched to the left position, the mold clamping ram 10 protrudes and the movable platen 5 moves forward toward the fixed platen 2. When the directional control valve 12 is switched to the right position, the mold clamping ram 10
contracts, and the movable platen 5 retreats.

The flow rate and pressure of the hydraulic oil supplied to the mold clamping cylinder 9 are controlled by an electromagnetic flow control valve 14 and an electromagnetic pressure control valve 15, respectively. The flow rate controlled by the electromagnetic flow control valve 14 and the pressure v-controlled by the electromagnetic pressure control valve 15 are set in a flow rate setting device 16 and a pressure setting device 17, respectively.

In the oil passage 18 communicating with the rear chamber 9a of the mold clamping cylinder 9,
A pressure detector 19 is provided to detect the pressure of hydraulic oil acting on the rear chamber 9a, that is, the mold closing pressure P.
The output signal of the pressure detector 19 is input to one input section of the comparator 20. The output signal of the arithmetic unit 21 is input to the other input section of the comparator 20 .

As shown in FIG. 2, this calculator 21 calculates the foreign object detection pressure PA that is estimated to be when a foreign object is caught between the fixed mold 6 and the movable mold 7.
, a multiplication factor setter 22 that can set an appropriate multiplication factor slightly smaller than 1, and a multiplier 23 that multiplies each set value set in these setters 17 and 22.

The comparator 20 compares the mold closing pressure P detected by the pressure detector 19 and the foreign object detection pressure PA calculated by the calculator 21, and outputs a signal when these values match. ing. The output signal is sent via the relay 24 to an alarm generator 25 and a switching control circuit 26 that controls the solenoids 12a and 12b of the electromagnetic directional switching valve 12. The alarm generator 25 is configured to issue an alarm when receiving the output signal from the comparator 20. Furthermore, when the switching control circuit 26 receives the output signal from the comparator 20, it switches the directional switching valve 12 to the neutral position.

A contact detection sensor 27 for detecting contact with the movable mold 7 is provided in the fixed mold 6 by one inch. In addition, a movable position detection sensor 28 is provided to detect the position of the movable platen 5, and after the movable platen 5 passes the movable platen position detection sensor 28, the relay 24 is closed until the contact detection sensor 27 operates, and the comparator is closed. An output signal from 20 is sent to an alarm generator 25.

Next, the operation 44 of the mold protection device configured as described above will be explained.

When performing injection molding, the mold 6.7 is first opened and then closed. In the mold closing process, the electromagnetic directional control valve 12 is switched to the left position, and the hydraulic pump 11 is switched to the left position.
Hydraulic oil discharged from the mold clamping cylinder 9 is introduced into the rear chamber 9a of the mold clamping cylinder 9. As a result, the mold clamping ram 10 protrudes, and the movable platen 5 changes to the fixed platen 2ffl! Moving forward toward I, the movable mold 7 approaches the fixed mold 6.

At this time, the load applied to the mold clamping cylinder 9 varies depending on the mold structure and the mold clamping mechanism of the molding machine, but since the relay 24 is open until it passes the movable platen position detection sensor 28, the load applied to the mold clamping cylinder 9 in FIG. As can be seen, even if the mold closing pressure P detected by the pressure detector 19 exceeds the foreign object detection pressure PA calculated by the calculator 21, no alarm is issued.After passing the movable platen position detection sensor 28, the relay is activated. 24 is closed, but when there is no foreign material between the molds 6 and 7,
Since the mold moulding process proceeds below the foreign object detection pressure PA, no alarm is issued, and in this state the movable mold 7 comes into contact with the fixed mold 6. Therefore, the contact detection sensor 27 detects this and opens the relay 24.

Once the mold 6.7 comes into contact, further movement of the movable ff15 is controlled. On the other hand, the rear chamber 9a of the mold clamping cylinder 9
The maximum pressure set in the electromagnetic pressure control valve 15,
That is, a set mold clamping pressure Pc is applied. Therefore, the movable mold 7 is pressed toward the fixed mold 6 by the mold clamping pressure Pc, thereby performing mold clamping. At this time, the molds 6 and 7 are in contact with the entire dividing surface, so the molds 6 and 7
．． 7 will not be damaged.

If foreign matter such as runners or burrs is attached to the dividing surface of the mold 6.7 after passing the movable platen position detection sensor 28, the first
As shown in the figure, the foreign object S is caught between the molds 6 and 7, and the movement of the movable platen 5 is restricted before the mold closing process is completed. At this time, the molds 6.7 are not in contact, so the contact detection sensor 27 is not activated and the relay 24 is in a closed state.

On the other hand, when the movement of the movable platen 5 is restricted in this way, the mold closing pressure P acting on the rear chamber 9a of the mold clamping cylinder 9 increases as described above. This pressure P is detected by a pressure detector 19 and input to a comparator 20. Therefore, when the pressure P rises to the foreign object detection pressure PA calculated by the calculator 21, a signal is output from the comparator 20.

Then, the alarm generator 2 is activated by the output signal from the comparator 20.
5, an alarm is generated, and the directional control valve 12 is switched to the neutral position to stop mold closing. In this case, the foreign object detection pressure PA is set to a value obtained by multiplying the set mold closing pressure Ps by a multiplier smaller than 1. therefore,
Mold closing will be stopped before the mold closing pressure P reaches the pressure Ps for the set mold. And the directional control valve 12
The pressure P in the rear chamber 9a of the mold clamping cylinder 9 decreases due to oil leakage or the like when the mold clamping cylinder 9 is switched to the neutral position, and is maintained in that state.

In this way, the pressure change in the rear chamber 9a of the mold clamping cylinder 9 when the foreign object S is caught between the molds 6.7 is as shown by the solid line in FIG. The mold 6.7 is reliably protected.

In this way, by calculating the foreign object detection pressure PA, which is the set value, by the calculator 21, even when the operating conditions such as the set mold closing pressure Ps of the injection molding machine 1 are changed, the same value can be used as is. You will be able to make it compatible. Furthermore, by setting the multiplication factor for calculating the foreign object detection pressure PA in the multiplication factor setting device 22,
The optimum multiplier is selected according to the flow rate of the hydraulic oil supplied to the mold clamping cylinder 9, etc., and the mold closing pressure P is set depending on the foreign object detection pressure PA and the inertia after mold closing is stopped.
It becomes possible to set the size to a size that does not exceed s.

In addition, in the above embodiment, this mold [IR1 method and apparatus are applied to an injection molding machine 1 equipped with a direct pressure mold clamping mechanism 8, but the present invention is not limited to this. It can also be applied to injection molding machines equipped with a toggle-type mold clamping mechanism and injection molding machines that close and clamp the mold using an electric motor. In the case of a mold clamping mechanism using an electric motor as a driving source, the mold closing pressure may be determined by detecting current or the like.

(g) Effects of the Invention As is clear from the above explanation, according to the present invention, when a foreign object is caught between the molds during mold closing, the mold is closed by utilizing the phenomenon that the mold closing pressure increases. Since an alarm is issued when the pressure reaches a set value, it is possible to detect the presence of foreign matter at an early stage, and the pressure applied to the mold can be kept low. Therefore, the mold can be reliably protected.

Furthermore, since the set value is calculated as the foreign object detection pressure, it can be easily adapted to the model and operating conditions of the injection molding machine, the mold used, etc.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a mold protection device in an injection molding machine that implements the mold protection method of the present invention. FIG. 2 is a characteristic curve diagram showing changes in mold closing pressure in the mold protection device, 21...Arithmetic unit 22...Multiplier setting device 2
3... Multiplier 24... Relay 25...
・Alarm generator 27...Contact detection sensor 28・
...Movable plate position detection sensor P: Mold closing pressure PA...Foreign object detection pressure Pc...Setting mold clamping pressure Ps...Setting mold closing pressure S...Foreign object patent applicant Nippon Steel Corporation Representative Yagi holder 1... Injection molding machine 5... Movable plate 7... Movable mold 15... Electromagnetic pressure control valve 19... Pressure detector 2... Fixed plate 6... Fixed mold 8...Mold clamping model 17...Pressure setting device 20...Comparator

Claims (1)

[Claims] 1. During the mold closing process before the mold clamping process, the actual mold closing pressure acting on the mold clamping mechanism (8) is continuously detected in an arbitrary set interval, and the mold closing pressure is detected. A mold protection method in an injection molding machine that consists of issuing an alarm when the value reaches a set value. 2. Mold protection in an injection molding machine according to claim 1, wherein the mold closing pressure set value is a value obtained by multiplying the set mold closing pressure set in the mold clamping mechanism (8) by a set multiplier. Method. 3. During the mold closing process before the mold clamping process, a pressure detector (
19), a movable platen position detection sensor (28) that determines the starting position of mold closing pressure detection, a contact detection sensor (27) that determines the position of detection completion, and a foreign object that is estimated to have been caught between the molds. a calculator (21) that calculates the detected pressure;
A comparator (20) that compares the mold closing pressure and the foreign object detection pressure and generates an output signal when these values match, and an alarm that issues an alarm upon receiving the output signal from the comparator (20). A mold protection device in an injection molding machine, comprising a generator (25). 4. A pressure setting device (17) in which the computing unit (21) sets a mold closing pressure to the mold clamping mechanism (8), and a multiplication factor setting device (22) capable of setting an appropriate multiplication factor; a multiplier (23) that multiplies the set type closing pressure set in the pressure setter (17) by a set multiplier set in the multiplier setter (22);
) The mold protection device for an injection molding machine according to claim 3, comprising: