JP2927923B2 - Method and apparatus for detecting resin leakage in injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a resin leakage detection of an injection molding machine capable of accurately detecting a resin leakage due to a mismatch between a sprue bush of a mold and an injection nozzle during injection molding. A method and apparatus.

(Prior art and its problems) In injection molding by an injection molding machine, resin pellets are supplied to the rear of the injection cylinder and the injection screw in the heating cylinder is rotated, whereby the resin pellets in the heating cylinder are gradually melted and kneaded. Then it moves toward the injection nozzle. During this period, the mold is closed. After the mold is closed in each cycle, the heating cylinder moves to the mold side, and the injection nozzle contacts the sprue bush of the fixed mold. The screw moves to the mold side and the molten resin accumulated at the tip of the heating cylinder is filled into the mold cavity via the screw bush.

What is important in this injection process is that the center of the injection nozzle and the sprue bush of the mold match as shown in FIG. 2, and the curvature of the tip of the injection nozzle is smaller than the curvature of the sprue bush so that the injection nozzle is accurately formed. Is fitted into the sprue bush. In this case, the injected resin is filled into the mold cavity without leaking. However, as shown in FIG. 3, when the curvature of the injection nozzle is larger than the curvature of the sprue bush, or If the center of the sprue bush and the center of the injection nozzle do not match, a gap is formed between the sprue bush and the tip of the injection nozzle. When the resin is injected, a part of the injected resin enters the gap and the surface pressure is reduced. Rises, the area of the resin to which the injection resin pressure is applied increases, and finally, the force generated by the resin pressure entering the gap becomes greater than the force pressing the heating cylinder against the sprue bush, and the injection nozzle , And
In addition, the phenomenon of promoting resin leakage from this part occurs, which not only tends to cause molding failure, but also causes problems such as loss of leaked resin and trouble of cleaning leaked resin attached around the injection nozzle. In addition, there can be situations where there is the danger that the molten hot resin will scatter around.

(Object of the Invention) The present invention has been made in view of the drawbacks of the conventional example, and its object is to instantaneously detect when even a slight back of the heating cylinder occurs due to resin leakage during injection,
An object of the present invention is to provide a method and an apparatus for detecting a resin leak in an injection molding machine, which can take necessary measures for a subsequent injection operation.

(Means for Solving the Problems) In order to achieve the above object, a method for detecting a resin leak of an injection molding machine according to the present invention comprises the steps of: heating a heating cylinder (10) of an injection molding machine (A) into a mold (1);
(2), and press the injection nozzle (25) at the tip of the heating cylinder (10) against the sprue bush (9) of the mold (1) (2). It is detected that the heating cylinder (10) has retreated a minute amount by the resin leakage pressure generated between the injection nozzle (25) and the sprue bush (9) when the injection filling into the mold cavity (7) is performed.

In order to achieve the above object, in the resin leakage detecting device of the injection molding machine, the injection molding dies (1) and (2) and the die (1) A heating cylinder (10) of an injection molding machine (A) having an injection nozzle (25) that comes into contact with and separates from (2).
A driving means (111) for bringing the heating cylinder (10) into contact with and separating from the dies (1) and (2); and the injection nozzle (25) being a sprue bush () of the dies (1) and (2). 9), the heating cylinder (10) retreats by a small amount due to the resin leakage force generated between the injection nozzle (25) and the sprue bush (9) of the mold (1) (2) at the start of injection. And a detecting means (16) for detecting an event.

(Operation) The resin pellets supplied from the hopper (24) are heated and melted and kneaded by rotating the injection screw (13) in the heating cylinder (10), and gradually heated in the heating cylinder (1).
Store inside the tip of 0). When a certain amount of molten kneaded resin is stored, the injection screw (13) is pushed forward to inject the molten kneaded resin accumulated at the tip of the heating cylinder (10) into the mold cavity (7). When the injection is completed, the injection screw (13) retreats while rotating, stops at the set retreat position, and completes preparations for starting injection in the next cycle.

Injection molding is performed by repeating the above operation. The sprue bush (9) of the fixed mold (1) is used.
When a mismatch occurs between the nozzle and the injection nozzle (25),
As shown in FIG. 3, the molten resin is pushed into the gap between the injection nozzle (25) and the sprue bush (9), so that the area of the resin portion to which the injection resin pressure is applied increases, and acts in a direction to enlarge the gap. Force is generated. In this case, the injection nozzle touch cylinder which presses the heating cylinder (10) and the injection nozzle (25) against the sprue bush (9) of the mold during the injection process, losing the increased force generated in the molten resin portion. The piston (11a) of (11) is slightly retracted.
The linear encoder (1
In step 6), the injection screw (13) is retreated, and the injection operation is stopped. As a result, it is possible to prevent the molten resin from projecting, which may cause a resin leak or a serious accident.

(Examples) Hereinafter, the present invention will be described in detail with reference to illustrated examples. FIG. 1 is a schematic sectional view of an injection molding machine according to the present invention.
Is a fixed mold, and (2) is a movable mold, which is mounted on the fixed plate (3) and the movable plate (4), respectively. The movable plate (4) reciprocates with four horizontal tie bars (5). It is freely supported, and is pressed by a fixed mold (1) by a toggle mechanism (6) on the back side to be clamped.
The fixed mold (1) is provided with a sprue bush (9) that communicates with the cavity (7) via a sprue (9a) and a runner (8).
The shape of the whole surface is bowl-shaped as shown in Figs. 2 and 3,
A sprue (9a) is drilled in the center. The heating cylinder (10) is fixed to the mount (12), and the injection nozzle touch cylinder (11) is fixed to the frame (13). The piston rod (11a) of the cylinder (11) is fixed to the mount (12).
The frame (12) can be reciprocated horizontally on a slide surface (13a) on a frame (13). As a result, the injection nozzle (25) at the tip portion comes into contact with or separates from the sprue bush (9) of the fixing plate (3). Heating cylinder (10)
Inside, an injection screw (13) is inserted so as to be rotatable and reciprocable by a drive mechanism (14), and a heater (15) is provided around the outer periphery of the heating cylinder (10) and around the injection nozzle (25). ) Is wound. In addition, heating cylinder (10)
At the rear end, a hopper (24) for supplying resin is mounted. The heating cylinder (10) is equipped with a linear encoder (16). The moving amount of the heating cylinder (10) is digitally output as a pulse, and the data is sent to the CPU (18) via a pulse input counter (17). Is to be entered. The CPU (18) has a RAM (19) attached to it.
8) and exchange necessary data with it. As shown in FIG. 4, the linear encoder (16) is fitted with a graduated slit plate (16a) and a slit plate (16a) which are horizontally arranged on a gantry (12) working with the heating cylinder (10). The slit plate (16a) moves together with the heating cylinder (10) horizontally between the photosensor portions (16b) fixed on the frame (13), with the U-shaped photosensor portion (16b). As a result, a pulse is output according to the scale engraved on the slit plate (16a). In this embodiment, the slit plate (16a)
Is moved by 0.5 mm, one pulse is output, and the movement amount is detected at the rise and fall of the pulse. Therefore, the movement amount can be detected in 0.25 mm width. I have. The detection accuracy of the above-mentioned movement amount is, for example, that the horizontal movement of the heating cylinder (10) is
Using a pinion device (not shown), slit plate (16a)
The accuracy can be increased to about 10 times by making the shape of a disk. Injection nozzle touch cylinder (11)
Is a return-type hydraulic cylinder, which is connected to a hydraulic pump (22) via a nozzle touch-back valve (20) and controlled by a CPU (18) via a valve output control circuit (21). When the solenoid (20a) of the nozzle touch back valve (20) is turned on, the heating cylinder (10) moves forward, and when the solenoid (20b) is turned on, the heating cylinder (10) moves backward. In addition, CPU (1
8) has a CRT (26) and a numeric keypad (23) connected.
Image display of necessary data and manual input of necessary data can be performed.

Next, the operation of the present embodiment will be described. Hopper (24)
The resin pellets are supplied to the heating cylinder (1) and the injection screw (13) is rotated while heating the heating cylinder (10).
0) The resin pellets from the hopper (24) attached to the rear part are sequentially heated and melted, kneaded, gradually fed to the injection nozzle (25) side, and stored inside the tip of the heating cylinder (10). The injection screw (13) gradually retreats with the storage of the melt-kneaded resin. Meanwhile, the mold (1)
On the side (2), the mold clamping is completed, and the injection receiving state is ready. Subsequently, the injection nozzle touch-back valve (20) is operated by a signal from the CPU (18) to supply pressure oil to the forward hydraulic chamber (11c) of the injection nozzle touch cylinder (11), and the cylinder ( 11) works to move the heating cylinder (10) to the fixed mold (1) side, and finally, as shown in FIG. 2, the injection nozzle (25) is accurately connected to the sprue bush. Thereafter, the drive cylinder (23) is operated to push the injection screw (13) forward, and the molten kneaded resin accumulated at the tip of the heating cylinder (10) is injected into the injection nozzle (2).
Extruded from 5) and injected into the mold cavity (7) through the sprue bush. When the injection ends, the CPU (1
In response to the command from 8), the injection nozzle touch back valve (20) is switched to the nozzle back side, and the injection nozzle (25) is retracted and separated from the sprue bush. When the heating cylinder (10) stops at the retracted position, the resin is again supplied to the heating cylinder (10), and the melt-kneading of the resin pellets is resumed, preparing for the next shot. All the moving amounts of the heating cylinder (10) forward and backward during this time are converted into pulse signals from the linear encoder (16), added and subtracted by a pulse counter, and taken into the CPU (18). In addition, the movement of the toggle mechanism (6) and others are all controlled based on a command from the CPU (18).

Injection molding is performed by repeating the above operation. In order for the injection molding operation to be performed smoothly, the curvature of the contact surface between the injection nozzle (25) and the sprue bush must be appropriate. Conditions such as (25) that the center line of the sprue bush coincides are required. Usually, accurate adjustments are made in advance so that a mismatch between the two does not occur. If the molten resin is pushed between the injection nozzle (25) and the sprue bush and acts in the direction of expanding the gap as shown in FIG. Since the force generated by the resin pressure applied to the spout is greater than the force pressing the injection nozzle (25) against the sprue bush (9), the injection nozzle touch cylinder (11) is slightly Retreat to This retreat amount is output as a pulse in the minimum unit by the linear encoder (16) to detect the occurrence of abnormal retreat of the heating cylinder (10) and notify the CPU (18) that the CPU (18) Immediately upon receipt of the input, an alarm is issued, and at the same time, the drive cylinder (23) is operated in the reverse direction to retract the injection screw (13) and stop the injection operation. As a result, it is possible to prevent the molten resin from projecting, which may cause a resin leak or a serious accident. After that, the cause of the mismatch is investigated, readjustment is performed to eliminate the mismatch, and the injection operation is restarted.

In this embodiment, after the minimum unit retreat amount (for example, 0.25 mm) of the slit plate (16a) is read by the counter (17), if the retreat amount is immediately greater than the comparison set value in the comparison step of the flowchart of FIG. Since the judgment is made and a resin leak alarm is issued and the machine is stopped, an extremely simple and inexpensive linear encoder such as a slit plate (16a) or a photo sensor unit (16b) can be used. This is because, as shown in FIG. 8, every time the injection is performed, a distortion occurs such that the central portion of the mold expands, for example, by about 0.1 mm due to the injection pressure applied to the mold cavity. Therefore, the injection nozzle (25) also retreats to that extent, which is a normal range for normal molding. However, for example, when the curvature of the sprue bush (9) is smaller than the curvature of the tip of the injection nozzle (25) as shown in FIG. 3, the cross-sectional area (S) of the gap between the two is equal to the cross-sectional area of the nozzle diameter. It is not unusual for the size of the injection nozzle (25) to be 0.25 to 0.5 mm, depending on the resin pressure applied to the cross-sectional area (S).
Things are set back. It is a useful feature of the present invention that simple and inexpensive linear encoder detection as described above can be performed from the reality where the difference is large. Of course, when the reading accuracy of the near encoder (16) is increased, the calculated value of the counter (17) becomes large. Even in this case, the set value can be appropriately increased to determine the normal / abnormal.

(Effects of the Invention) In the resin leakage detection method for an injection molding machine according to the invention, the heating cylinder of the injection molding machine is advanced toward the mold, and the injection nozzle at the tip of the heating cylinder is pressed against the sprue bush of the mold. Then, when the injection of the molten resin into the mold cavity was performed, it was detected that the heating cylinder was retracted due to the resin leakage force generated between the injection nozzle and the sprue bush. There is an advantage that the leaked resin can be immediately detected, and an accident such as a protrusion of the molten resin caused by the resin leak can be prevented.

In addition, the injection molding machine according to the present invention includes a mold for injection molding, a heating cylinder of the injection molding machine having an injection nozzle that comes into contact with and separates from the mold, and a heating cylinder that is brought into contact with the mold.・ Detecting that the heating cylinder retreats due to the resin leakage force generated between the injection nozzle and the mold sprue bush at the start of the injection when the injection nozzle comes into contact with the drive means for separating and the sprue bush of the mold at the start of injection. Therefore, the method of the present invention of immediately detecting a resin leak occurring during injection can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of the injection molding machine of the present invention and a block circuit diagram of a nozzle touch portion. FIG. 2 is a sectional view showing a relationship between a sprue bush and an injection nozzle in a normal case. FIG. FIG. 4 is a cross-sectional view showing the relationship between the sprue bush and the injection nozzle. FIG. 4 is a perspective view of an embodiment of the detecting means used in the present invention. FIG. 5 is a flowchart of a nozzle touch portion during the injection molding process of the present invention. ... Flowchart of the injection portion during the injection molding process of the present invention FIG. 7. Flowchart of the nozzle back portion during the injection molding process of the present invention FIG. 8. ... injection molding machine, (1) ... fixed mold (2) ... moving mold, (7) ... mold cavity (9) ... sprue bush, (10) ... heating cylinder (11) ... Drive means, (16) ... Detecting means (25) ... injection nozzle

Claims (2)

(57) [Claims] 1. A heating cylinder of an injection molding machine is advanced toward a mold, and an injection nozzle at a tip of the heating cylinder is press-connected to a sprue bush of the mold. A resin leakage detection method for an injection molding machine, characterized in that it detects that the heating cylinder has receded a minute amount by the resin leakage force generated between the injection nozzle and the sprue bush when performing the injection filling. 2. A mold for injection molding, a heating cylinder of an injection molding machine having an injection nozzle which comes into contact with and separates from the mold, and driving means for bringing the heating cylinder into contact with and separating from the mold. Detecting means for detecting that the heating cylinder is retracted due to a resin leakage force generated between the injection nozzle and the sprue bush of the mold at the time of starting the injection, wherein the injection nozzle comes into contact with the sprue bush of the mold. A resin leakage detection device for an injection molding machine, characterized in that it has been performed.