JPH0534135B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control method and apparatus for an injection molding machine, and in particular, the pressure of the molten resin is detected by a resin pressure sensor in the sacback process, and the molten resin is This invention relates to a novel improvement for eliminating drooling, stringing, mold breakage, etc. by comparing a pressure signal of resin pressure with a set signal of target resin pressure to control the back-back process.

[Prior Art] Generally, the inside of a mold manifold is always filled with molten resin by a manifold heater.
Because it communicates with the molded part through the gate,
When a sufficiently high pressure is applied to the resin in the manifold during the injection and pressure holding processes, the molten resin, which is a non-Newtonian fluid, is elastically compressed and replenished, but after the mold has cooled down, the mold is opened and the molded product is taken out. At this time, the resin pressure in the manifold is not reduced and remains at high pressure, so the resin in the manifold drools from the gate area, causing a so-called stringing phenomenon, which may adhere to the molded product and result in a defective product. In some cases, the mold was damaged by adhering to the mold and clamping the mold under high pressure.

One solution to this problem is to use a timer or detection switch to control the so-called "success-back process" in which the screw is forcibly retreated in the reflection output direction after the completion of holding pressure to be performed for a predetermined timer or a predetermined stroke. That was commonly used.

[Problems to be Solved by the Invention] Since the conventional injection molding machine control method and apparatus were configured as described above, the following problems existed.

In other words, after opening the mold, when releasing the molded product, how many times should the suction stroke or suction timer be set to reduce the resin pressure in the manifold in the hot runner mold to the extent that drooling does not occur from the gate part? However, there was a problem in that it had to be determined through repeated trial-and-error tests and required considerable skill.

In addition, even if the above-mentioned suction back is actually carried out according to the set values, if the resin pressure in the manifold before the suction process is higher than normal, after the molded product has been released, there will be a drop from the gate of the hot runner mold. Rings are generated, and this drooled resin becomes cold slag in the next shot molded product, causing molded product defects, or it is crushed during mold clamping and blocks the gate, causing abnormally high pressure to occur during injection. There was a serious problem that it could cause the mold to break.

The present invention has been made to solve the above-mentioned problems, and in particular, in the suction process, the resin pressure of the molten resin is detected by a resin pressure sensor, and the pressure signal of the molten resin pressure is used as the target resin pressure. An object of the present invention is to provide a control method and apparatus for an injection molding machine that eliminates drooling, stringing, mold breakage, etc. by controlling the back-back process by comparing the set signal with the setting signal.

[Means for Solving the Problems] A method for controlling an injection molding machine according to the present invention forcibly retreats the screw in the cylinder in the direction of reflection and ejection after the injection and pressure holding process, and removes the molten resin communicating with the inside of the cylinder. In a method for controlling an injection molding machine that performs a suction step for reducing pressure, a first step of detecting the molten resin pressure in a nozzle at the tip of the cylinder with a resin pressure sensor provided in the nozzle; The second step is to compare the molten resin pressure obtained in the first step with a target resin pressure preset in a resin pressure setting device, and when the molten resin pressure and the target resin pressure match, the This method is designed to complete the process.

Furthermore, the method for controlling an injection molding machine according to the present invention includes:
In a method for controlling an injection molding machine, the screw in the cylinder is forcibly retreated in the direction of reflection and ejection after the injection and pressure holding steps, and a back-back step is performed to reduce the pressure of the molten resin in the molten resin communicating with the inside of the cylinder. , a first step of detecting the molten resin pressure in the mold facing the cylinder with a resin pressure sensor provided in the mold; and setting the molten resin pressure obtained in the first step to a resin pressure setting device in advance. This method includes a second step of comparing the molten resin pressure with a set target resin pressure, and ends the succumbing step when the molten resin pressure and the target resin pressure match.

Furthermore, the control device for an injection molding machine according to the present invention includes:
A screw provided in the cylinder, a piston provided in the injection cylinder for rotating the screw and moving it in the axial direction, a hydraulic motor for rotating the piston, and an injection cylinder front chamber of the injection cylinder. A first directional switching valve for selectively supplying pressure oil from a hydraulic source, and a second directional switching valve for selectively switching pressure oil to the hydraulic motor and the rear chamber of the injection cylinder,
In the control device for an injection molding machine, the screw can be moved in the injection direction and the back-back direction by the rotation and axial reciprocation of the piston, the melting of the molten resin in the nozzle communicating with the inside of the cylinder. a resin pressure sensor provided in the nozzle at the tip of the cylinder to detect resin pressure; and a comparison calculation for comparing and calculating the pressure signal of the resin pressure sensor and the target resin pressure setting signal from the resin pressure setting device. and a controller for controlling switching of the first directional switching valve based on the output signal from the comparison calculator,
The configuration is such that the operation of the first directional switching valve is controlled when the molten resin pressure and the target resin pressure match.

Furthermore, the method for controlling an injection molding machine according to the present invention includes:
A screw provided in the cylinder, a piston provided in the injection cylinder for rotating the screw and moving it in the axial direction, a hydraulic motor for rotating the piston, and an injection cylinder front chamber of the injection cylinder. A first directional switching valve for selectively supplying pressure oil from a hydraulic source, and a second directional switching valve for selectively switching pressure oil to the hydraulic motor and the rear chamber of the injection cylinder,
In the control device for an injection molding machine, the screw can be moved in the injection direction and the back-back direction by the rotation and axial reciprocation of the piston, in which the molten resin in the mold communicating with the inside of the cylinder is controlled. a resin pressure sensor provided in the mold for detecting molten resin pressure; and a comparator for comparing and calculating the pressure signal of the resin pressure sensor and the target resin pressure setting signal from the resin pressure setting device. and a controller for controlling switching of the first directional switching valve based on the output signal from the comparator, the controller controlling switching of the first directional switching valve when the molten resin pressure and the target resin pressure match. This configuration controls the operation of the valve.

[Function] In the injection molding machine control method and apparatus according to the present invention, the resin pressure at the nozzle part of the cylinder, the resin pressure in the manifold in the hot runner mold, and the resin pressure in the gate part in the hot runner mold are controlled by the resin pressure setting device. When the pressure is reduced to the target resin pressure, the suction process ends and the mold is opened after that, so drooling from the gate does not occur.
It is possible to prevent molded product defects due to stringiness and mold damage mainly caused by stringy resin.

[Embodiments] Hereinafter, preferred embodiments of the injection molding machine according to the present invention will be described in detail with reference to the drawings.

A first embodiment of the method and apparatus for controlling an injection molding machine according to the present invention shown in FIG. 1 will be described in detail.

In Fig. 1, the reference numeral 1 indicates a cylinder of an injection molding machine, and a screw 2 is rotatably provided in a cylinder chamber 1a within the cylinder 1, and a resin supply is provided in the upper part of the cylinder 1. A section 1b is provided.

An injection cylinder 21 containing a piston 20 that can rotate and move in the axial direction is attached to the rear end 1c of the cylinder 1, and the screw 2 is connected to one end 20a of the piston 20. , the other end 20 of the piston 20
A rotating shaft 22a of a hydraulic motor 22 is connected to b.

The hydraulic motor 22 is rotated by pressure oil supplied from a hydraulic power source 23 via a second directional valve 27, and the piston 20 and screw 2 are configured to rotate due to the rotation of the hydraulic motor 22. ing.

Injection cylinder front chamber 21 of the injection cylinder 21
a is connected to the first port A of the first directional control valve 26 via the electromagnetic proportional flow valve 29 for suction speed control.
is connected to and leads to the tank. The a side of the first directional switching valve 26 is connected to the hydraulic pressure source 23 in an excited state, and is further connected to the input side of an electromagnetic relief valve 30 for setting the back-back pressure. Furthermore, the relief valve 24 is provided as a safety valve for the hydraulic power source 23, and also serves as a safety valve for the check valve 2.
5 is provided as a backflow prevention valve to the hydraulic power source 23.

Further, the electromagnetic relief valve 28 is connected to the second directional control valve 2
It is connected to the fourth port T of 7.

Further, the injection cylinder rear chamber 21b is connected to the second port B of the first directional switching valve 26 and the first port A of the second directional switching valve 27. A nozzle 12 having a resin pressure sensor 13 is formed at the tip of the cylinder 1, and a pressure signal 13 which is the molten resin pressure is output from the resin pressure sensor 13.
a is the first signal of the comparator 15 via the amplifier 14.
A setting signal 16a, which is the target resin pressure set in the resin pressure setting device 16, is applied to the input section 15a, and is input to the second input section 15b.

The output signal 15c of the comparator 15 is applied to a controller 17 connected to the first switching valve 26, and this controller 17 is connected to the first switching valve 26.
6.

The injection molding machine control method and apparatus according to the present invention are configured as described above, and the operation thereof will be explained below.

First of all, the packing after pressure holding and weighing is as follows.
The a side of the first directional switching valve 26 is energized, and the hydraulic pressure is set at the opening degree of the electromagnetic proportional flow valve 29 corresponding to a predetermined suction speed and at the pressure set by the electromagnetic relief valve 30 corresponding to a predetermined suction pressure. Pressure oil from 23 is supplied to the injection cylinder front chamber 21a of the injection cylinder 21.

When the screw 2 retreats due to the above-mentioned back-back operation, the tip of the screw 2 communicates with the inside of the mold (not shown) through the nozzle 12, and the pressure of the molten resin, which has been accumulated and increased due to the holding pressure, gradually increases. Reduce the pressure to

In the above-mentioned state, the resin pressure sensor 13 detects the pressure of the molten resin communicating within the mold, and the pressure signal 13a indicating the detected actual molten resin pressure is
After being amplified by the amplifier 14, it is input to the comparator 15 and compared with a setting signal 16a which is a target resin pressure preset in the resin pressure setting device 16.

The comparison calculator 15 outputs a signal to the first controller 17 to operate the first directional control valve 26 in order to control the back-back operation to end when the calculated deviation becomes zero.

Therefore, the back-to-back operation that starts after holding pressure is
It operates at a predetermined pressure and speed and can be terminated when the resin pressure within the nozzle 12 reaches a predetermined set pressure.

Although the resin pressure sensor 13 has been described for detecting the resin pressure inside the nozzle 12, it detects the resin pressure inside the manifold inside the hot runner mold and the mold (not shown) inside the gate section inside the hot runner mold. ) Resin pressure sensor 13
The same effect can be obtained even if a mold is provided and the resin pressure inside the mold is detected. Furthermore, the present invention can also be applied to the back-up operation after metering for the purpose of preventing drooling from the nozzle after metering.

[Effects of the Invention] Since the injection molding machine control method and apparatus according to the present invention are configured as described above, the following effects can be obtained.

In other words, after holding pressure and/or after metering, the back-back operation is performed when the resin pressure in any of the nozzle, the manifold in the hot runner mold, the gate part in the hot runner mold, etc. reaches a predetermined target resin pressure. Since the feedback control is carried out so as to complete the process, there is no drooling or stringing from the gate inside the hot runner mold after the molded product is released, and mold damage during mold clamping can be completely eliminated.

[Brief explanation of the drawing]

The drawings are for illustrating a method and apparatus for controlling an injection molding machine according to the present invention, and FIG. 1 is a block diagram showing an embodiment. 1 is a cylinder, 2 is a screw, 13 is a pressure sensor, 13a is a pressure signal, 15 is a comparator, 15
c is an output signal, 16 is a resin pressure setting device, 17 is a controller, 20 is a piston, 21 is an injection cylinder, 21a is an injection cylinder front chamber, 21b is an injection cylinder rear chamber, 22 is a hydraulic motor, 23 is a hydraulic source,
27 is a second directional switching valve, and 26 is a first directional switching valve.

Claims (1)

[Claims] 1. After the injection and pressure holding steps, the screw 2 in the cylinder 1 is forcibly retreated in the direction of reflection and exit, and a suction step is performed to reduce the pressure of the molten resin in the molten resin communicating with the inside of the cylinder 1. In the injection molding machine control method, a first step of detecting the molten resin pressure in the nozzle 12 at the tip of the cylinder 1 with a resin pressure sensor 13 provided in the nozzle 12; The molten resin pressure is compared with a target resin pressure preset in the resin pressure setting device 16, and when the molten resin pressure and the target resin pressure match, the suction process is completed. A method for controlling an injection molding machine, characterized by: 2. An injection molding machine that forcibly retreats the screw 2 inside the cylinder 1 in the reflection and exit direction after the injection and pressure holding steps to perform a suction step for reducing the pressure of the molten resin in the molten resin communicating with the inside of the cylinder 1. In the control method, a first step of detecting the molten resin pressure in the mold facing the cylinder 1 with a resin pressure sensor 13 provided in the mold; and a step of detecting the molten resin pressure obtained in the first step. The present invention is characterized by comprising a second step of comparing the molten resin pressure with a target resin pressure preset in a resin pressure setting device 16, and ending the suction step when the molten resin pressure and the target resin pressure match. How to control an injection molding machine. 3. A screw 2 provided in the cylinder 1, a piston 20 provided in an injection cylinder 21 for rotating the screw 2 and moving it in the axial direction, a hydraulic motor 22 for rotating the piston 20, and a hydraulic motor 22 for rotating the piston 20. A first directional switching valve 26 selectively supplies pressure oil from a hydraulic source 23 to the injection cylinder front chamber 21a of the injection cylinder 21, and selectively supplies pressure oil to the hydraulic motor 22 and the injection cylinder rear chamber 21b. control of an injection molding machine, which is equipped with a second directional switching valve 27 for switching to the injection molding machine, and is capable of moving the screw 2 in the injection direction and the back direction by the rotation and axial reciprocation of the piston 20. In the apparatus, a resin pressure sensor 13 provided at the nozzle 12 at the tip of the cylinder 1 to detect the pressure of the molten resin in the nozzle 12 communicating with the inside of the cylinder 1, and a pressure signal from the resin pressure sensor 13. 13
a comparison calculator 15 for comparing and calculating a target resin pressure setting signal 16a from the resin pressure setting device 16; and an output signal 15 from the comparison calculator 15.
a controller 17 for controlling the switching of the first directional switching valve 26 based on c, and controlling the operation of the first directional switching valve 26 when the molten resin pressure and the target resin pressure match. A control device for an injection molding machine, characterized in that: 4. A screw 2 provided in the cylinder 1, a piston 20 provided in an injection cylinder 21 for rotating and moving the screw 2 in the axial direction, a hydraulic motor 22 for rotating the piston 20, and A first directional switching valve 26 selectively supplies pressure oil from a hydraulic source 23 to the injection cylinder front chamber 21a of the injection cylinder 21, and selectively supplies pressure oil to the hydraulic motor 22 and the injection cylinder rear chamber 21b. control of an injection molding machine, which is equipped with a second directional switching valve 27 for switching to the injection molding machine, and is capable of moving the screw 2 in the injection direction and the back direction by the rotation and axial reciprocation of the piston 20. In the apparatus, a resin pressure sensor 13 provided in the mold for detecting a molten resin pressure of molten resin in a mold communicating with the inside of the cylinder 1, and the resin pressure sensor 13
a comparison calculator 15 for comparing and calculating the pressure signal 13a of the target resin pressure with the target resin pressure setting signal 16a from the resin pressure setting device 16; and the first direction switching based on the output signal 15c from the comparison calculator 15. valve 26
an injection molding machine, comprising: a controller 17 for controlling switching of the molten resin pressure and a target resin pressure, and controlling the operation of the first directional switching valve 26 when the molten resin pressure matches the target resin pressure control device.