JPH0615189B2 - Injection control method of injection molding machine - Google Patents

Description

The present invention relates to an injection control method suitable for use in setting a control position and a monitor position of a screw of an injection molding machine, in particular.

[Conventional technology]

Generally, in the injection process of an in-line screw type injection molding machine, predetermined speed control and pressure control are performed on the screw, and the screw position is monitored. Accurate setting of the screw control position and monitor position is of high quality. It is an important factor for obtaining a molded product.

Conventionally, the control position of the screw, such as the shift position of the injection speed, the speed pressure switching position from the speed control area to the pressure control area, etc., has been set as an absolute position, and the screw has advanced to reach these control positions. Was detected and predetermined control was performed.

The monitor range that monitors the most advanced position of the screw, detects whether the screw position exists between the upper limit value and the lower limit value set in advance, and judges the quality of the molded product in that cycle is also the same. Yes, the upper limit value and the lower limit value were set as absolute positions.

[Problems to be solved by the invention]

However, the conventional injection control method described above has the following problems.

That is, the screw position at the start of injection is not constant in each cycle, and the fluctuation occurs in the front and rear due to disturbance or the like. For example, as shown in FIG.
(p01), injection speed shift position (P02), (P03), speed pressure switching position from speed control area to pressure control area (p04), and from position (p04) a holding pressure is applied for a predetermined time by a timer. After setting the position (the most forward position) (p05), let the lower and upper limits that define the monitor range set before and after this position (p05) be (M01) and (M02), respectively. In the cycle, the injection start position is in front of the original position (P01) (P0H)
If it is, the moving stroke amount of the screw from at least the injection start position (P0H) to the shift position (P02) is insufficient, and the molded product becomes a short shot defect. Similarly, if the injection start position is located behind the original position (P01), the stroke of movement of the screw becomes excessive, resulting in overfilling and burr. Moreover, despite the defective product,
If it is within the monitor range, there is a problem that it is determined as a non-defective product. In Fig. 3, (40) is a screw,
(41) indicates a heating cylinder.

[Means for solving problems]

The present invention is intended to provide an injection control method for an injection molding machine that solves the above-mentioned problems existing in the related art, and is achieved by the following method.

That is, in the injection control method according to the present invention, first, the screw
The injection start position (P21) in (1) is detected. Then, with reference to the detected vehicle model start position (P21), the first shift position (P2) that is the control position of the screw (1) in the detected cycle.
2), the second shift position (P23), the speed pressure switching position (P24), the foremost entry position (P25), and the lower limit value (M21) for the most advanced position of the screw (1) for judging the quality of molded products. And the upper limit (M
22) is used to set the monitor position, and this detection and setting is performed for each cycle.

[Action]

 Next, the operation of the present invention will be described.

In the injection control method according to the present invention, each control position and monitor position are set relatively in real time with reference to the injection start position (P21) detected in each cycle.
Therefore, even if the injection start position of the screw fluctuates back and forth in each cycle, the substantial injection control distance of each sile becomes constant. In addition, each control position (P2
2) to (P24), that is, the lower limit (M2) that is the monitor range based on the most advanced position (P25) based on the best injection control distance.
1) and the upper limit (M22) are set. At this time, the lower limit (M21)
Since the upper limit value (M22) and the upper limit value (M22) are set in conjunction with the set control position of the screw (1), the range of the monitor position, that is, the width between the lower limit value (M21) and the upper limit value (M22) is narrowed. As a result, it is possible to accurately determine a subtle defective product including a defective product caused by a disturbance factor.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view of a screw for explaining the method of the present invention, and FIG. 2 is a sectional side view of an injection molding machine including a block circuit of a control system for carrying out the method of the present invention.

First, in order to help understanding of the method of the present invention, a schematic configuration of the injection molding machine (10) shown in FIG. 2 will be described.

(11) is the main body of the injection molding machine, and the screw is installed in the heating cylinder (12).
When the (1) is inserted, the rear end of the screw (1) is connected to the injection ram (14) in the injection cylinder (13). Therefore, the screw (1) constitutes a known molding machine body which is advanced by the injection cylinder (13) and rotated by the oil motor (15) provided at the rear end of the cylinder (13).

On the other hand, (20) indicates a control yarn. First, (21) is a central controller having a computer function. (22) is a screw
The position detector detects the position of (1), and this detection information is input to the central controller (21). Further, the central controller (21) includes an injection start position setter (23), a first gear shift position setter (24), a second gear shift position setter (25), a speed pressure switching position setter (26), and a holding pressure. A time setting device (27), an upper limit value setting device (28) for dividing the monitor range, a lower limit value setting device (29), a primary injection speed setting device, a secondary injection speed setting device, and a tertiary injection (not shown). Connect various necessary setting devices such as speed setting device, filling pressure setting device and holding pressure setting device. Molding conditions for obtaining the best molded product are set in each of these setting devices. The injection start position setting device also serves as the metering stop position setting, and the filling pressure setting device sets the pressure required to maintain the primary speed and the secondary speed. Further, (30) is a hydraulic oil control device connected to the injection cylinder (13), for controlling the pressure oil from the hydraulic pressure source (31) supplied to the oil chamber of the injection cylinder (13), It is controlled by a flow rate command signal and a pressure command signal from the controller (21). Reference numeral (32) represents an oil tank connected to the hydraulic oil control device (30).

Next, a molding process including the injection control method according to the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows the original screw position immediately before the shift to the injection process. The original injection start position, which is the reference, is
(P11), the corresponding first shift position is (P12), the second shift position is (P13), the speed pressure switching position is (P14), and the lower source value and the upper limit value that are the monitor positions are the screw (1). Most advanced position (P15)
Are set in the corresponding setters (23) to (26), (28) and (29) in advance as (M11) and (M12) located before and after, respectively. In addition, in the present embodiment, for the sake of convenience, only these control elements will be described, but it goes without saying that various other control elements are included as described above.

First, in the injection process, the hydraulic oil control device receives an injection start command based on the sequence control of the central controller (21).
The filling pressure command signal and the primary speed command signal are sent to (30), and the screw (1) starts to move forward at the primary speed.

On the other hand, the screw position when the injection start command is issued, that is, the injection start position is detected by the position detector (22). Now, the detected injection start position is (P21), and this position (P21) is in front of the reference injection start position (P11) set in the setting device (23), and the deviation ( α) Suppose. The controller (21) calculates the deviation (α) by the arithmetic processing function ((P21)-(P11)),
Based on this deviation (α), each setter (24) ~
Correct the value in (29) and set a new optimum value. That is,
The first gear position (12) is set to (22) (= (12) + (α)), the second gear position (13) is set to (23) (= (13) + (α)), and the speed / pressure switching position is set. (14)
Is (24) (= (14) + (α)), and the lower limit value (11) is (21) (= (11) +
In (α)), the upper limit value (12) is reset to (22) (= (12) + (α)).

Then, after the injection is started, the screw (1) is in the first shift position (P22).
When it reaches, the central controller (21) sends a secondary speed command signal to the hydraulic fluid control device (30), the screw (1) shifts to the secondary speed and advances, and the screw (1) shifts to the second shift speed. When the position (P23) is reached, a tertiary speed command signal is sent from the control (21) to the device (30), and the screw (1) shifts to the tertiary speed and moves forward. When the screw (1) reaches the speed pressure switching position (24), a pressure holding command signal is sent from the controller (21) to the device (30), and the screw (1) sets the pressure holding time setting unit (27). The pressure is controlled for a set time.

The screw (1) becomes the most advanced position after the holding time has elapsed, and this position is determined by the monitor range. That is, if the most advanced position (P25) exists between the upper limit value (M22) and the lower limit value (M21), the molded product in this cycle is determined as a good product, and if it deviates from this range, it is determined as a defective product. Since the upper limit value (M22) and the lower limit value (M21) that are the monitor positions are reset based on the injection start position, for example, by narrowing the monitor range, including defective products caused by disturbance factors, Even a subtle defective product can be accurately determined.

After that, the process shifts to the measuring step, the screw (1) is rotated by the operation of the oil motor (15), and new material is measured and accumulated in front of the screw (1). The screw (1) retreats along with weighing, reaches the weighing stop position (injection start position), and stops. Thus, one cycle of molding process is completed.

Then, again in the next cycle, the injection start position of the screw (1) is detected, the deviation from the reference position (P11) is calculated, and each control position and monitor position in the same cycle are reset in real time.

Although the embodiments have been described in detail above, the present invention is not limited to such embodiments. For example, although the monitor item is set as the most advanced position of the screw, this position may be set at the time of completion of injection (before applying the holding pressure), or a plurality of positions may be simultaneously monitored. In the deviation (α), the deviation amount for resetting the control position, etc. may be variably set at a predetermined ratio with respect to the deviation of the injection start position or the width of the monitor range. , The position and the like may be changed according to the magnitude and direction of the deviation (α). Furthermore, any other factors such as the temperature of the material can be taken into account in these settings.

〔The invention's effect〕

As described above, the injection control method of the injection molding machine according to the present invention detects the injection start position of the screw for each cycle, and with the detected injection start position as a reference, the control position of the screw in the detected cycle and the molded product Since the monitor position using the lower limit value and the upper limit value with respect to the most advanced position of the screw for performing quality determination is set for each cycle, the following remarkable effects are achieved.

Control accuracy is greatly improved, stable and high molding quality is guaranteed, and at the same time, the lower and upper limit values of the monitor position for judging the quality of molded products are set in conjunction with the set screw control position. Therefore, by making the monitor position (range) narrower or the like, it is possible to perform accurate and accurate quality determination, such as higher quality non-defective product selection or subtle defective product reliable selection.

Control can be easily performed by changing the program of the central controller, which contributes to cost reduction.

[Brief description of drawings]

1 is a side view of a screw for explaining the method of the present invention, FIG. 2 is a sectional side view of an injection molding machine including a block circuit of a control system for implementing the method of the present invention, and FIG. 3 is a conventional method. The side view of the screw for doing. In the drawings, (1): screw, (P21): injection start position (P22): first gear shift position, (P23): second gear shift position (P24): speed pressure switching position (P25): most forward position, (M21): Lower limit (M22): Upper limit

Claims (1)

[Claims] 1. A lower limit to a screw re-advance position for detecting the injection start position of a screw for each cycle, and using the detected injection start position as a reference to detect the screw control position in the detected cycle and the quality of a molded product. An injection control method for an injection molding machine, wherein a monitor position using a value and an upper limit value is set for each cycle.