JPH0752208A - Method of monitoring injection molding machine and injection molding system using this method - Google Patents

Abstract

PURPOSE:To perform precisely a quality decision of a molded product, by a method wherein it is judged whether an action of an injection molding machine is normal or not by detecting a position where forward movement becomes impossible at the time when a pressurizing member is moved forward within a cylinder by pressurizing the pressure member by the first pressure and a position where the pressurizing member is stopped by moving the pressurizing member backward when the pressure is taken as the second pressure lower than the first pressure. CONSTITUTION:When a screw 9 becomes unable to move forward by controlling an injection cylinder 13 by the first injection pressure P=70%, a position of the tip 9a' of a screw head is detected by an encoder 15 by taking the position as the first position and a detected value x is obtained. Then when pressure is taken as the second pressure P=20%, the screw 9 is moved backward, a position of the tip 9a of the screw head is detected by the encoder 15 by taking the position as the second position and a detected value y is obtained. Then the absolute value ¦x-y¦ is obtained through the first and second positions x, y supplied to a controller 4 from the encoder by a judging device 16. The value is compared with an allowable range stored beforehand in the judging device 16 and an excellent article and it is judged whether an injection molding process is normal or an abnormal action.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring an injection molding machine and an injection molding system using this method.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine for injecting a resin material into a cavity of a mold by a screw to obtain a molded article, as means for judging whether the operation in the injection molding process is normal or abnormal, Some encoders detect the forward position of the screw for feeding the synthetic resin material into the cavity. Normally, the screw position at the completion of the injection process is detected.The screw position at the completion of the process is detected for each injection molding process, and injection is performed by checking whether this is within the preset allowable range. It is judged whether the operation of the molding machine is normal or abnormal. If the molding machine is out of the allowable range, the molded product is judged to be defective.

In the conventional injection molding system,
With respect to the one in which the resin in the cavity is pressurized with a high pressure by the screw to complete the operation at the maximum forward position of the screw, the operating state is monitored by comparing the maximum forward position (first conventional example). Also, for those that complete the operation from the state where the screw is at the maximum forward position with a slight pressure relief to reduce the load, it is necessary to monitor the operating state by comparing the position where the screw slightly retracted and stopped. (Second conventional example).

[0004]

In the conventional injection molding system, the operation abnormality is detected only by one item (for example, the screw position when the injection molding process is completed) at one point in the injection molding process. However, this does not mean that the accuracy is perfect. For example, in the first conventional example, if the screw cannot be sufficiently retracted due to some trouble and the sufficient amount of resin cannot be supplied, if the screw is advanced to a predetermined position, Although it is regarded as normal, there is a possibility that the size and shape of the molded product may be deformed due to an insufficient amount of resin. The second
In the conventional example of 1, even if the advance of the screw during the injection molding process is insufficient, it is considered normal if the stop position at the time of the process completion is within the predetermined range, but in this case also a sufficient amount of resin It does not necessarily spread throughout the cavity, and there is still a risk of abnormalities in the molded product.

On the contrary, if the screw is advanced too much during the molding process, the resin amount will be excessively filled, which may cause a large burr on the molded product. In that case, it is necessary to perform secondary processing such as deburring in order to use it as a product, which is troublesome. Thus, in the conventional technology,
It cannot be said that the injection molding machine can be accurately monitored whether it is operating normally according to the set conditions.

Therefore, an object of the present invention is to detect data that has a deep correlation with the dimensional accuracy of an injection-molded product particularly in the injection-molding process and use it as a criterion for judgment so that the injection-molding machine operates normally under the set conditions. It is to be able to accurately monitor whether or not it is operating.

[0007]

In order to achieve the above object, in a method for monitoring an injection molding machine according to the present invention, a resin material in a cylinder is pressurized by using a pressure member, and the pressure is applied to a cavity of a mold. Using an injection molding machine that enters into the interior to obtain a molded product, a first position at which a pressurization member is pressed at a first pressure to advance in the cylinder And a second position where the pressure member retracts and stops when the pressure applied to the pressure member is relaxed to a second pressure lower than the first pressure, and injection molding is performed based on this detection information. It is to determine whether the operation of the machine is normal.

A feature of the injection molding system of the present invention is that a cylinder to which a resin material is supplied and a pressurizing device that is disposed in the cylinder and pressurizes the resin material in the cylinder can be injected into the cavity of the mold. It is provided with a member and an advancing / retreating drive means for advancing / retreating the pressing member in the cylinder. Further, a first position at which the pressure member cannot move forward when the pressure member advances in the cylinder by the first pressure by the advancing / retreating drive means,
A second position where the pressure member retracts and stops when the pressure applied to the pressure member at the first position by the advancing / retreating drive means is relaxed to a second pressure lower than the first pressure is detected. And a determination unit that receives the output of the detection unit and determines whether the operation of the injection molding machine is normal.

[0009]

The distance between the first position and the second position of the pressing member corresponds to the amount of compression of the resin material injected into the cavity and represents the resin pressure in the cavity. That is, this is to detect whether or not the cavity is filled with an appropriate amount and pressure of the resin material in the injection molding process, and whether or not the operation for producing a normal molded product is normally performed. You can judge accurately.

[0010]

FIG. 1 shows the overall construction of an embodiment of the injection molding system according to the present invention, in which a fixed mold 2 is fixed to a fixed platen 1 and a movable mold facing the fixed mold 2. 3 is fixed to the movable platen 4 and can be moved back and forth toward the fixed mold 2 by the mold clamping means 5. A cavity 6 having a desired molded product shape is formed on the contact surface between the fixed mold 2 and the movable mold 3.

The cylinder 7 has a ring-shaped heater 8 on its outer circumference.
Is provided, and its tip (left end) is joined to the fixed mold 2. A hollow portion 7a is provided at the axis of the cylinder 7, and the nozzle 7b at the tip of the hollow portion communicates with the cavity 6. A screw, which is a pressurizing member 9 for pressurizing the resin material, is fitted in the hollow portion 7a so as to be rotatable and retractable. The stroke S of the screw 9 is represented by the stroke 0 mm at the most advanceable position, and the stroke S becomes larger as it moves backward.

A hopper 10 is disposed above the rear end (right end) of the cylinder 7, and the powdery resin material housed in the hopper 10 is stored in the hollow portion 7a of the cylinder 7 by its own weight. It is designed to fall.

The rear end of the hollow portion 7a is open, and the screw 9 is rotationally driven by transmitting the rotational force from the drive motor, which is the rotating means 11, through the gear device 12 from this opening. At the same time, a driving force that moves forward and backward is applied by the injection cylinder that is the forward-backward driving means 13.

FIG. 3 is a block diagram of the injection molding system of the present invention, in which the mold clamping means 5, rotating means 11 and advancing / retreating driving means 13 are controlled by a control means (controller) 14 for controlling the entire injection molding process. Is done,
The advance / retreat driving means 13 is driven under the control of the injection speed V (%) or the injection pressure P (%). The position of the tip 9a of the screw 9 is detected by the detection means (encoder) 15, and the detected value is supplied to the control means 14. Further, in response to the supply of the detection value from the control unit 14, the determination unit 16 monitors the operation of the injection molding machine described later. Further, the molded product take-out means 17 has a chucking means which is not shown but comprises a vacuum suction device or a gripping claw and the like, and is controlled by the control means 14 so that the two molds 2 and 3 in the mold open state and a non-defective product. It is movable between the accommodation means 18 and the defective article accommodation means 19. Then, the molded product take-out means 17 takes out the molded product from the cavity of the movable mold 3, and if the normal molding process is performed, it is stored in the good product storage means 18, and if it is determined that the operation is abnormal, the defective product storage means. The molded product is stored in 19.

Next, the operation of molding a molded product will be described with reference to FIGS. 2 and 4. FIG. 2 is an enlarged view of a part of the injection molding machine, and FIGS. 4A and 4B are diagrams showing control examples of the injection cylinder 13. 5 shows the relationship between the actual stroke and time in the injection process controlled based on the molding conditions shown in FIG.

First, the movable mold 3 is moved forward together with the movable platen 4 by the operation of the mold clamping means 5, and is brought into contact with the fixed mold 2 so that the cavity 6 is sealed. When powdered resin material is dropped from the hopper 10 into the hollow portion 7a and the screw 9 is driven to rotate by the drive motor 11, the material is sent to the tip portion of the hollow portion 7a while being kneaded. During this time, the resin material is heated by the heater 8 and becomes in a molten state. When the molten resin material is sufficiently stored in the tip portion of the hollow portion 7a, the drive motor 11 is stopped at the predetermined position S1 to stop the rotation of the screw 9. At the position where the rotation of the screw 9 is stopped, a sufficient amount of resin material to fill the cavity 6 is provided in the hollow portion 7.
It is determined by whether or not it is stored at the tip of a and can be regulated by a limit switch.
This position S1 is the resin injection start position, which is the position of stroke 16 mm in this embodiment as shown in FIG.

Next, the injection cylinder 13 is driven. In the following description, the actual speed and pressure are shown as percentages when the speed and pressure of the screw 9 when the advancing / retreating driving means 13 is operated with the maximum driving force are set to 100%, respectively.

First, as shown in FIG. 4A, a step of injecting a molten resin material into the cavity 6,
The injection cylinder 13 is controlled based on the stroke S and the injection speed (speed of the screw 9) V. First, the injection speed V
= 40%, the injection cylinder 13 is controlled, the screw 9 is moved forward from the position S1, and when the position S2 with a stroke of 8 mm is reached, the injection speed V = 5% is controlled thereafter. By reducing the injection speed V from 40% to 5%, the molten material is reasonably injected into the cavity 6 through the thin sprue and runner (not shown). Injection speed V
= 5%, when the screw 9 advances to the position S3 with a stroke of 6 mm, the injection speed V is increased to 40% again, but this is the position S4 with a stroke of 0.1 mm.
Stop with. This ensures the filling of the resin material in the cavity 6. The process from this position S1 to S4 is the actual injection operation and is called the filling region.

Next, as shown in FIG. 4B, the process moves to the step of applying pressure in order to make the density of the resin material filled in the cavity 6 uniform, and the injection cylinder 13 is operated for a time T.
And the injection pressure P. First, the injection pressure P =
Cylinder 13 is controlled at 20%, and this state is maintained for time T =
Hold for 0.1 seconds. Next, the injection cylinder 13 is controlled at the injection pressure P = 70% as the first pressure P1, and this state is maintained for the time T = 1.5 seconds. As a result, the density of the resin material with which the cavity 6 is filled becomes uniform, the internal pressure of the resin is maintained at a predetermined value, and the screw 9 cannot move forward. The position (maximum forward movement position) of the tip 9a 'of the screw head at this time is detected by the encoder 15 as the first position to obtain the detection value x. Next, as the second pressure P2, the injection pressure P =
When the injection cylinder 13 is controlled at 20%, the pressure applied to the resin material, which is kept at a predetermined resin internal pressure, is reduced, and the resin in the cavity repels the screw 9, causing the screw 9 to move backward, The backward movement of the screw 9 stops at a position where the injection pressure of 9 and the repulsive force of the resin maintain a balance. The position of the tip 9a of the screw head at this time is detected by the encoder 15 as the second position to obtain the detection value y.

In FIG. 5, the stroke Smm is plotted on the vertical axis and the time Tsec is plotted on the horizontal axis, showing the movement of the tip 9a of the screw head at the injection stage and the pressure-holding stage shown in FIGS. It is shown in the figure.

Then, the first position (detection value x) and the second position (detection value y) supplied from the encoder 15 to the controller 14 are supplied to the judging means 16 and the absolute value of the difference between the two detection values is supplied. (| X−y |) is obtained. This corresponds to the distance between the two positions. That is, it corresponds to the fluctuation of the compression amount of the resin material in the cavity 6. Therefore, this absolute value | x−y | is compared with a predetermined allowable range stored in advance in the determination means 16, and if it is within the allowable range, it is considered that the injection molding process is normal, and it is outside the allowable range. The case is determined to be abnormal operation. For example, when the screw head tip 9'is 2.5 mm from the nozzle at the first position and 5.7 mm at the second position, the absolute value of this difference is 3.2 mm, which is a tolerance (for example, ± 0.1 mm). ) Added allowable range 3.1 mm to 3.
3 mm is the standard for quality judgment. Therefore, x = 2.0 mm,
Even when a result such as y = 5.2 mm is obtained, the absolute value of these differences | x−y | = 3.2 mm is equal to the set value, so it is determined that the injection molding operation is normal. .
Therefore, based on the determination result by the determination means 16, the control means 14 sends a normal signal or an abnormal signal to the molded product take-out means 17.

Next, the movable platen 4 and the movable mold 3 are retracted by the mold clamping means 5 to be in the mold open state, and the molded product take-out means 1
The molded product is taken out from the cavity 6 by bringing 7 into close proximity to the movable mold 3. When a normal product is formed (when a normal signal is sent), the molded product is taken out from the molded product removing means 17
It is transferred to the non-defective item storage means 18 by. When an abnormal product is formed (when an abnormal signal is sent), the molded product is transferred to the defective product storage unit 18 by the molded product takeout unit 17. As described above, the molded product whose molding process is normal and the molded product which is abnormal are divided into the non-defective product accommodating means 18 and the defective product accommodating means 19 to be accommodated. The non-defective product accommodating means 18 and the defective product accommodating means 19 may be a simple box-shaped container, or may have a configuration in which a tube-shaped carrier pipe is provided and a molded product is fed into the box-shaped container.

The above operation is continuously repeated to perform injection molding one after another, and it is judged whether or not the molding process is normal. Based on the result, the molded product is stored in the good product storing means 18 and the defective product storing means 19. The work of separating and taking out is continued. Note that the molding machine is stopped when the occurrence of operation abnormality continues for a predetermined number of times (for example, 5 times) or when the cumulative number of occurrence of operation abnormality reaches a predetermined number (for example, 10 times) during the molding process continuation. I am trying to do it.

Since the amount of resin used is determined by the shape of the molded product at the stage of designing the molded product, the molding condition is determined in consideration of these and is registered in the controller 14 in advance, whereby the automatic injection is performed. Molding becomes possible. Specifically, trial firing is performed several times, and the first position x and the second position y
However, it is possible to obtain an appropriate molded product and a position suitable for detection and quality judgment (for example, x = 2.5 mm, y = 5.
7 mm or the like), the molding conditions as shown in FIG. 4 are set in advance, and in the actual molding process, injection molding is performed under the same molding conditions to obtain the absolute value | xy. , That value was set based on the trial shot (3.2 m
Find out how different it is from m). Further, if a plurality of types of optimum molding conditions are registered in advance, accurate and efficient automatic injection molding can be performed even when molds are exchanged and a wide variety of products are molded.

The determination means 16 may be built in the control circuit of the injection molding machine main body, or may be configured to use a computer or the like provided separately from the injection molding machine main body.

[0026]

As described above, according to the method of monitoring the injection molding machine and the injection molding system of the present invention, when the cavity is filled with resin and the pressing member is pressurized at the first pressure, it is advanced. Whether the molding process was normal by detecting the first position where the pressure is disabled and the second position where the pressure member retracts and stops when the pressure is reduced to the second pressure lower than the first pressure. Since it is determined whether there is an abnormality and the correlation with the dimensional accuracy of the molded product is based on the compression amount of the resin material filled in the cavity, it is possible to ensure that a predetermined amount of resin with a predetermined pressure is placed in the cavity. It is possible to accurately determine whether or not the operation for filling is performed accurately. Thus, the quality of the molded product can be accurately determined.

[Brief description of drawings]

FIG. 1 is a partially sectional front view showing an embodiment of an injection molding system according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view of FIG.

FIG. 3 is a control block diagram of the injection molding system of FIG.

FIG. 4 is a diagram for explaining control of the injection cylinder 13,
(A) is an operation diagram of injecting a resin material into a cavity, and (b) is an operation diagram of pressurizing and holding the filled resin material.

[FIG. 5] The vertical axis represents the stroke S (mm) and the horizontal axis represents the time T.
FIG. 6 is a diagram showing the movement status of the tip of the screw during the injection operation and the pressure holding operation shown in FIGS. 4A and 4B as (seconds).

[Explanation of symbols]

 2, 3 Mold 6 Cavity 7 Cylinder 9 Pressurizing Member (Screw) 13 Advance / Retract Drive Means (Injection Cylinder) 15 Detecting Means (Encoder) 16 Judging Means P1 First Pressure P2 Second Pressure x First Position y Number Position 2

Claims (2)

[Claims] 1. An injection molding machine for pressurizing a resin material in a cylinder by using a pressurizing member and injecting the resin material into a cavity of a mold to obtain a molded article, and pressurizing at the first pressure. A first position at which the pressurization member cannot be advanced when the pressurization member is advanced in the cylinder and the pressure applied to the pressurization member at the first position is relaxed; And a second position where the pressure member retracts and stops when the second pressure is lower than the lower pressure, and it is determined whether the operation of the injection molding machine is normal based on the detected information. A method for monitoring an injection molding machine, comprising: 2. A cylinder to which a resin material is supplied, a pressurizing member which is disposed in the cylinder and which pressurizes the resin material in the cylinder and injects the resin material into a cavity of a mold. A forward / backward drive means for moving the pressure member forward and backward in the cylinder; and a first forward / backward drive means for preventing the pressure member from moving forward when the pressure member advances in the cylinder at a first pressure. The position and the first and second drive means for moving the first
Detecting means for detecting a second position where the pressure member retracts and stops when the pressure applied to the pressure member at the position is relaxed to a second pressure lower than the first pressure. An injection molding system comprising: a determination unit that determines whether or not the operation of the injection molding machine is normal by receiving the output of the detection unit.