JPS62122727A - Starving sensing device in injection mold - Google Patents

Abstract

PURPOSE:To surely detect the generation of resin material shortage in a product cavity portion by a method wherein a temperature sensor is faced to a product part most remote from a gate, through which molten resin is poured or to a portion, at which material shortage tends to develop so as to directly detect the temperature of resin during the pouring of the resin. CONSTITUTION:A through hole consisting of a small diametral part 4, a medium diametral part 5 and a large diametral part 6 is provided in a movable mold 2. A bushing 7 is fitted to said through hole. An axis core hole 10, to which a thermocouple 11 is fitted, is formed in the bushing 7. Lead wires 14, the tips of which are connected to a detection circuit, is connected to the thermocouple 11. During the mold closing period in molding cycle, if the detected temperature does not reach the predetermined temperature with respect to the set resin temperature, alarm is issued on the basis of the detection signal of starving by means of alarm lamp, buzzer or the like. At the same time, a machine is stopped or the amount of raw material resin is increased. Furthermore, the material lacking product is automatically selected as defective product.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for detecting lack of product in an injection mold, and in particular, when a synthetic resin is injected into the injection mold, molten resin is detected in the cavity. The present invention relates to an underfill sensing device that can reliably detect whether or not it is completely filled.

[Background of the invention]

Generally, when molding a product by injecting molten resin into a mold, the filling may not reach the entire mold due to fluctuations in injection pressure or mold temperature, resulting in some missing parts. It is known that molded products with insufficient thickness occur. Since some of the molded products have insufficient thickness, mechanisms have been conventionally provided for automatically sorting the molded products and adjusting the injection pressure. However, the occurrence of a molded product with insufficient thickness significantly reduces the yield of the product.

Therefore, in recent years, attempts have been made to detect in advance the lack of product thickness in injection molds and prevent the occurrence of products with insufficient thickness. In both cases, when molten resin is injected into an injection mold, it is indirectly detected whether or not the molten resin is completely supplied to the mold part.

As a conventional device for detecting lack of thickness in molten resin,
There are Japanese Utility Model Publication No. 5-174319, Japanese Utility Model Publication No. 57-6521, Japanese Utility Model Publication No. 59-16187, and Japanese Patent Publication No. 11610-1988. The first of these (for example, Utility Model Application No. 55-174319) has holes penetrating axially inside each of a pair of pins that are attached to an injection mold with their tips facing each other with the mold inserts in between. A recess with a diameter larger than that of each through hole is formed at the tip and rear end of each pin, and a light transmitting substance such as an optical fiber is inserted into each through hole. , a light emitting body for a photoelectric switch connected to the rear end of the phototransmitter is housed, a photoreceptor for the photoelectric switch connected to the rear end of the phototransmitter is housed in a recess at the rear end of the other pin; It is possible to detect whether the filler is filled or not, depending on whether or not light from the light emitting body is received.

2nd (for example, Utility Model Application No. 57-6521, Utility Model Application No. 59-
No. 16187) is built into an injection mold and causes a pressure receiving part for resin filling pressure to protrude, and a dummy pin that can be moved in the opposite direction to the protruding direction in the cavity by the resin filling pressure is installed to control the amount of movement. By detecting this, it is possible to detect lack of meat in the product.

The third method (for example, Japanese Patent Publication No. Sho 6o-11610) is to dispose the air circuit at the resin injection end of the cavity so that it can be cut off by the molten resin, regardless of the structure or size of the mold. It detects whether the molten resin has reached the resin injection end of the cavity by sensing the pressure change in the air circuit that is blocked due to the influence of the resin.

[Problem that the invention seeks to solve]

Such conventional devices have the following drawbacks.

That is, in the first step, a hole must be prepared for mounting a pin in which a pair of optical fibers or other light transmitting material is inserted into the through hole, facing each other with the mold hole in between. There are some items that should not leave marks, and this method has the disadvantage that it cannot be applied to such items.

In addition, the second method has the disadvantage that if high precision is required in the dummy pin and hole machining, malfunction may occur as the mold temperature rises, and if the precision is reduced, it may cause cracks and malfunction. Also, depending on this type of device, when resin is injected, the dummy pin is activated by the compressed gas pressure in the cavity, which tends to cause false detection, and the unit weight of the product is 5 to 5.
It has the disadvantage that it can only be applied to small size devices on the order of Log.

Furthermore, the third problem is that a gap for air release must be provided in the product part, and high pressure must be applied to release air in the gap of 30 to 40 μm, which is the limit for releasing air. The disadvantage is that the pressure difference is extremely small and requires large-scale equipment.

[Purpose of the invention]

An object of the present invention is to be able to reliably detect the filling state of molten resin at the end of a cavity with simple equipment, regardless of the size of the mold or the structure of the mold. An object of the present invention is to provide an underfill sensing device for an injection mold.

[Means for solving problems]

In the present invention, a temperature sensor is placed in the part of the product farthest from the gate for injecting molten resin or a part where underfilling is likely to occur, and the resin temperature during resin injection is directly detected, thereby preventing underfilling in the product cavity area. The idea is to detect the occurrence of such a phenomenon.

That is, the present invention is a molding method in which molten resin is injected from a gate into a cavity of a fixed mold and a movable mold, and the resin temperature of the molten resin is directly detected near the part where underfilling is most likely to occur. The present invention is characterized in that a temperature sensor is provided, and underfilling is detected when the temperature value detected by the temperature sensor does not exceed a predetermined temperature.

[Effect]

With this structure, when the cavity is filled with molten resin, the temperature of the molten resin is detected by the temperature sensor exposed inside the cavity. If the temperature of the molten resin (above a predetermined temperature) is not detected by this temperature sensor, it means that the cavity is completely filled with the molten resin. Further, if the predetermined temperature is not detected by the temperature sensor, this is a case where the portion where the temperature sensor is installed is not filled with molten resin. Therefore, if a predetermined temperature is not detected by the temperature sensor, the occurrence of underfilling is detected. When this occurrence of underfilling is detected, measures such as stopping injection molding are taken.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the invention.

In the figure, the product is molded by injecting molten resin into a cavity 3 formed by a fixed mold 1 and a movable mold 2 through a gate (not shown).

This movable mold 2 is provided with a through hole formed by a small diameter part 4, a medium diameter part 5, and a large diameter part 6. This through hole has a bushing 7.
are fitted. This bushing 7 connects the flange 8 with the bolt 9.
It is attached to the movable mold 2 by. A shaft hole 10 is formed in this bushing 7, and a thermocouple 11 is fitted into this shaft hole 10. This thermocouple 11 is held by a holding cap 12, and this holding cap 1
2 is screwed onto the threaded portion 13 of the bushing 7. A lead wire 14 is connected to this thermocouple 11, and this lead wire 14 is connected to a groove having a U-shaped cross section that is bored in the movable mold 2 from the bush through hole toward the outside at right angles to the mold opening direction. 1
5 and is taken out to the outside. A detection circuit (not shown) is connected to the tip of this lead wire 14.

The thermocouple 11 configured in this manner constantly detects the temperature of the resin. When the mold is closed in the molding cycle, if the detected temperature does not reach the predetermined temperature for the set resin temperature, an alarm is issued with an alarm lamp, buzzer, etc. based on the underfill detection signal, and the machine is stopped or the raw material Products with increased resin content or insufficient thickness are automatically sorted out as defective products.

As the thermocouple in this embodiment, a sensor with a small diameter of about 1.6 to 1 diameter, a small heat capacity, and a quick response is suitable. Also,
To prevent the temperature sensing part of the thermocouple from being affected by the mold temperature of the mold it is in contact with, it is better to bush it with a material that has a good heat insulating effect, and to cool the area around or near the bushing. is desirable.

FIG. 2 shows the mounting position of the thermocouple 11 on the side, and the basic components are the same.

A circuit diagram using the thermocouple 11 is shown in FIG.

In the figure, a power switch 100 includes a thermocouple drive device 1.
01 is connected. A thermocouple 102 is attached to this thermocouple drive device 101.

Additionally, the power switch 100 includes a timing relay 103.
, detection relays 105 and 108 and underfill display flicker
A lamp 110 is connected. A molding machine type close signal switch 107 is connected to this timing relay 103 . Further, this molding machine mold close signal switch 107 is connected to a detection relay 1 via a timing relay contact 104.
05 is connected. In addition, this detection relay 105
A relay contact 106A is connected to this relay contact 106A, and a return press switch 112 is connected to this relay contact 106A via a thermocouple drive device contact 113. Further, a return push button switch 112 is connected to the detection relay 108 via a detection relay contact 109. Further, a detection relay contact 106B is connected to the detection relay 108 and the underfill indicator flicker lamp 110, and a mold closing signal switch 111 is connected to the detection relay 106B. Further, the relay contact 109 is connected to a stop device of the molding machine (not shown).

Note that the detection relay contacts 106A and 106B are connected to the detection relay 105 by the detection relay contact 109A.
, 109B are configured to act respectively by the detection L/-108.

With this configuration, when the power switch 100 is currently ON and the relay contact 107 is turned ON by a signal issued from the molding machine, the timing relay 103 is turned ON. When timing relay 103 is turned on, timing relay contact 104 is turned on. When this relay contact 104 is turned on, a detection relay 105 is activated. This detection relay 105 is ON
Then, relay contacts 106A and 106B are turned on. The return push button switch 112 is always ON.

The switch is turned off by pressing the button.

When the relay contacts 106A and 106B are turned on, the thermocouple 1
When the detected temperature of 02 reaches a predetermined temperature, the contact 101 is turned on. As a result, in the detection relay 105, the timing relay 103 is activated and the relay contact 104 is turned ON.
and while the signal emitted from the molding machine is coming,
Relay contacts 104 and 107, relay contact 106A, relay contact 113 operated by thermocouple drive device 101,
The operating state is maintained by a return push button switch 112.

Timing relay 103 operates only for a predetermined time. When this timing relay 103 turns OFF due to time-up, the circuit by relay contacts 104 and 107 goes to 0FFL, and the detection relay 105 turns OFF at relay contact 1.
06A, 113 The ON state is maintained by the return push button switch 112. At this time, if the underfilling occurs inside the mold, when the injection process is completed, the resin temperature is detected by the thermocouple 102, and if the resin temperature exceeds the set value, the relay contact 113 activated by the thermocouple drive device 101 is set to ○FFL, and the detection relay 105
The hold is broken. In addition, if there is a lack of thickness, the resin temperature will not be detected by the thermocouple 102 even after the injection process is finished, and therefore the thermocouple drive device 101 will not exceed the set value.
The relay contact 113 activated by this remains ON, and the detection relay 105 remains held.

Next, when the signal from the molding machine turns OFF, the relay contact 10
7 is 0FFL, the mold closing signal switch 111 is turned on,
If there is a lack of metal, the detection relay 105 is still in the ON state, so the detection relay 108 is turned ON by the relay contact 106B and the mold closing signal switch 111. This return push button switch 112) Relay contact 10
9A, the ON state of the detection relay 108 is maintained, and the underfill indicator flicker lamp 110 blinks to indicate the presence of underfill. In this case, measures such as stopping the molding machine are taken using the relay contact 109B.

Note that by pressing the return push button switch 112, the holding of the detection relays 105 and 108 is released. An example of detection using a thermocouple is shown in FIG. 4(A). Figure 4 (A)
Point b is the electromotive force in the case of a non-defective product, and point C is the electromotive force indicating the occurrence of underfilling. In the figure, a is the electromotive force, d is the electromotive force at the start of injection, and between dd and d is one shot cycle.
e indicates the set electromotive force.

Figure 4 (B) shows the mold temperature difference for determining the set temperature, and the upper limit temperature (directly related to injection) and lower limit temperature (when cooled immediately before injection) of the mold in long-lot production. Based on this data, ■ The maximum temperature difference between the upper and lower limits is 9℃, and the average is 5℃ ■ The minimum temperature difference between the upper and lower limits is 9℃ or more, so the set temperature should be determined based on the upper limit temperature at startup. The temperature was set at 4°C, and after about 2 hours, when stable production was achieved, the temperature was reset to 4°C below the upper limit temperature. However, the set temperature varies slightly depending on the cooling water temperature and molding conditions as the upper and lower humidity limits change.

Therefore, according to this embodiment, a thermocouple is embedded in the end part of the product farthest from the gate or in a part where underfilling is likely to occur (see A in FIG. 1 and A in FIG. 2), and the temperature is maintained at a set temperature. Because it detects the presence or absence of underfill based on the difference,
It is not affected by the size or structure of the mold.

Furthermore, according to this embodiment, large-scale equipment is not required;
Since the filling state of molten resin at the end of the cavity is reliably detected, it is easy to connect directly to automatic sorting.

Further, according to this embodiment, the structure is simple, it can be easily incorporated into a mold, almost no maintenance is required, and it has excellent effects with high reliability.

Another embodiment of the invention is shown in FIG.

In the figure, this embodiment differs from the embodiments shown in FIGS. 1 and 2 in that a resistor is used instead of a thermocouple to detect the temperature of the molten resin. Components in FIG. 5 denoted by the same reference numerals as in FIG. 1 are the same parts and have the same functions.

According to this embodiment, the temperature of the molten resin can be accurately detected without being affected by changes in ambient temperature.

There is also a method of using a thermistor instead of a thermocouple. The circuit configuration is the same as that of the thermocouple except that a thermistor is deposited on the temperature sensing portion in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, the filling state of the molten resin at the end of the cavity can be controlled with simple equipment, regardless of the size of the mold or the structure of the mold. Can be reliably detected.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an embodiment of the present invention, Figure 2 is a diagram with the thermocouple shown in Figure 1 in a different mounting position, Figure 3 is a circuit diagram using the thermocouple, and Figure 4 (A ) Diagram showing the electromotive force of a thermocouple,
FIG. 4(B) is a diagram showing electromotive force converted to temperature, and FIG. 5 is a diagram showing another embodiment of the present invention. 1... Fixed mold 2... Movable mold 3... Cavity 7... Bush 11... Thermocouple agent Patent attorney Tatsuyuki Unuma (and 2 others) Figure 1

Claims (2)

[Claims] (1) In molding by injecting molten resin from a gate into a cavity that is a combination of a fixed mold and a movable mold, the resin temperature of the molten resin is directly detected near the point where underfilling is most likely to occur. What is claimed is: 1. A lack-of-filling detection device for an injection mold, comprising: a sensor; and detecting a lack of fillet when a temperature value detected by the temperature sensor does not exceed a predetermined temperature. (2) In the invention as set forth in claim 1, the underfill sensing device in an injection mold is characterized in that the temperature sensor is a thermocouple.