JP2525222B2 - Molding control method for injection molding machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an injection molding method using an injection molding machine.

2. Description of the Related Art A molding method for changing the cavity volume from the start of injection to the end of holding pressure and its control method are described in, for example, JP-A-63-35327, as an injection compression molding method.
It is known from JP-A-63-39314 and the like. The control in the compression step of these conventional injection compression molding methods is only compression control, and control on the cavity volume from the compression side is not performed. For example, the one described in Japanese Patent Laid-Open No. 63-35327 discloses speed control of the mold moving speed at the initial stage of mold clamping for compression, and when the mold reaches a set position, speed control is performed. The pressure control is switched to single-stage or multi-stage pressure control to control the compression process, and no control is performed on the mold position at the end of the compression process, that is, the final volume of the resin injected into the cavity.

Further, the one described in JP-A-63-39314 also switches from the filling step to the compression step when the amount of resin filled in the cavity by injection reaches a target value.
The pressure is controlled, and in this case as well, there is no control over the final volume of the resin injected into the cavity from the compression side.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in the conventional compression control, only the cavity volume is secured and the pressure control is performed, and the control from the compression side to the final volume is not performed at all. Therefore, in the conventional compression control method, the amount of resin filled in the cavity is related to the accuracy in the injection process, and it is not possible to obtain more than this accuracy, and the volumetric accuracy of the molded product, that is, the dimensional accuracy of the molded product. Depends on the accuracy of this injection process.

Therefore, an object of the present invention is to provide a molding control method for an injection molding machine that can improve the dimensional accuracy of a molded product by controlling the cavity volume.

Means for Solving the Problems In order to achieve the above object, the invention described in claims 1 to 4 is a compression means for compressing a resin in a mold, and a rotation motion of the compression means is linear. A servo motor driven via a means for converting into motion and a position detector for detecting the rotational position of the servo motor to detect the position of the compression means are provided, and the position of the compression means is feedback-controlled to start injection. From the time to the end of the pressure holding, the servo motor is driven to advance the compression means, and the pressure for pressing the resin in the mold by the servo motor in a single step according to the position detected by the position detector is applied. Alternatively, while controlling by switching to multiple stages, the resin in the mold is compressed until the position detector detects that the set position has been reached, and both position control and pressure control are performed to form a molded product. of Improve dimensional accuracy.

Further, when the resin is not compressed to the set position within the set predetermined time after the drive of the compression means is started, the molded product is discriminated as a defective product to improve the dimensional accuracy of the molded product.

In particular, the compression means is composed of a moving member that moves in the mold that is clamped to compress the resin in the mold, or is used as a mold clamping device that moves the movable mold to clamp the mold. .

Action In the invention described in claims 1 to 4, the compression means presses the resin in the mold by the servo motor in accordance with the position detected by the position detector from the start of injection to the end of pressure holding. The pressure is switched to a single stage or multiple stages and controlled to control the resin in the mold to a set position.

As a result, the cavity volume control and pressure control are performed, and the dimensional accuracy of the molded product is improved.

Further, if the set position is not reached within the set predetermined time after the driving of the compression means, the amount of resin filled in the cavity is large,
It is determined that the molded product is not a product with the required dimensional accuracy.

Embodiment FIG. 2 is a block diagram of the essential parts of an injection molding machine that employs the molding control system of the present invention.

In the figure, 1 is a mold, 2 is a heating cylinder, and 3 is a screw. Further, 4 is a core, and in this embodiment, a servo motor
The rotation of 10 is passed through the timing gear 9 and the timing belt 8 so that the core 4 is moved to the right in the figure by the ball nut 7 and the ball screw 6 that convert the rotational movement into the linear movement so that the resin 13 in the cavity is compressed. ing. Reference numeral 5 is a load cell for detecting the pressure applied to the resin 13 in the cavity. The pressure detected by the load cell 5 is the A / D converter 1
It is designed to be converted into a digital signal at 2. Reference numeral 11 is a pulse coder as a position detector for detecting the rotation of the servomotor, that is, the position of the core 4. Reference numeral 20 denotes a numerical control device as a control device for controlling the injection molding machine. The numerical control device 20 is a central processing unit (hereinafter, CPU) 21 for numerical control (hereinafter, NC) and a programmable machine. CPU for controller (hereinafter referred to as PMC)
The CPU 22 for NC has a bus 24 connected to the NC CPU 21. The ROM 24 stores a control program for controlling the entire injection molding machine and the RAM 25 used for temporary storage of data. Further, the NC CPU 21 has a servo interface 26
Is connected to a bus, and the servo interface 26 is connected to a servo circuit for driving and controlling a servo motor for each axis of injection, clamping, screw rotation, compression, and the like. Only the servo circuit 27 of is shown. The servo circuit 27 is connected to the servo motor 10 and receives a feedback pulse from the pulse coder 11 to control the rotational position, torque, etc. of the servo motor 10.

The PMC CPU 22 has a ROM 28 and a PMC for storing a sequence program for controlling the sequence operation of the injection molding machine.
A RAM 29, which is used for temporary storage of data in the process of the CPU 22 performing arithmetic processing, is connected to the bus.

The NC CPU 21 and the PMC CPU 22 are bus-connected by a bus arbiter controller (hereinafter referred to as BAC) 23, and a shared RAM 30, an input circuit 31, and an output circuit 32 are further bus-coupled to the BAC 23. The shared RAM 30 is composed of a writable non-volatile memory such as a bubble memory or a CMOS memory, and stores an NC program for controlling the operation of the injection molding machine, various set values such as molding conditions, parameters, macro variables and the like. It is like this. Various sensors provided in the injection molding machine are connected to the input circuit 31, and particularly related to the present invention, a pressure signal obtained by converting the output signal of the load cell 5 into a digital signal by the A / D converter 12 is output. It is supposed to be entered.

Although various actuators of the injection molding machine are connected to the output circuit 32, the output circuit 32 is related to the present invention.
Therefore, a torque limit value for limiting the output torque of the compression servo motor 10 is output to the servo circuit 27.

Further, a manual data input device with a CRT display device (hereinafter referred to as CRT / MDI) 34 is connected to the BAC 23 via an operator panel controller 33.

With the above configuration, the CRT /
Various molding conditions are input and set from the MDI 34 and stored in the shared RAM 30. Particularly, regarding the present invention, the position of the core 4 that has completed compression during the compression process, that is, the rotational position of the servo motor 10 that has completed compression, the torque limit value that is the compression force, the compression time, and the quality of the molded product Set the value of timer TN.

Next, when the injection molding machine is operated, the numerical controller 20
Sequence program stored in ROM 28 and shared RAM 30
The injection molding machine is controlled according to the NC program stored in, and the molding process is repeated by repeating the steps of mold closing, mold clamping, injection, compression, holding pressure, cooling, metering, mold opening, and molding product ejection. At the step, the PMC CPU 22 starts the processing of the compression step shown in FIG. First, the PMC CPU 22 is a shared RAM 30
The compression time set in is read via BAC23 and RAM
The compression time is set in the compression timer Tp provided in 29 and started (step S1). The torque limit value as the compression force set in the shared RAM30 is set to BAC23,
Output to the servo circuit 27 via the output circuit 32 to limit the output torque of the servo motor 10 (step S2), and the shared RAM 30
The compression completion position set to is set to the address position of the shared RAM 30 read by the NC CPU 21 (step S3),
Furthermore, the setting value of the NG timer TN set in the shared RAM 30 is read, set in the NG timer TN provided in the RAM 29 and started (step S4), and the compression start command is shared.
Write to RAM30 (step S5). When the compression start command is read from the shared RAM 30, the NC CPU 21 starts pulse distribution to the set compression completion position, and the servo interface
Output to the servo circuit 27 via 26. The servo circuit 27 outputs a torque command according to the difference between the commanded pulse amount and the pulse amount detected by the pulse coder 11, and the output circuit
The servo motor 10 is driven by limiting the output torque according to the torque limit value output from 32, the timing gear 9,
The core 4 is moved to the right in FIG. 1 via the timing belt 8, the ball nut 7, and the ball screw 6 to compress the resin in the cavity. At this time, the compression pressure detected by the load cell 5 is converted into a digital signal by the A / D converter 12 and input to the input circuit 31, but the PMC CPU 22 receives the feedback compression pressure and the current torque limit value. Compare
The torque limit value is increased / decreased so that the pressure detected by the load cell 5 becomes the set compression pressure (torque limit value) and output to the servo circuit 27 via the output circuit 32.

Although this pressure feedback control is not shown in the flowchart of FIG. 1, this is the same as the conventional pressure feedback control. Alternatively, the compression pressure control may be performed by simply applying the torque limit to the output of the servo motor 10 by the open control without performing the pressure feedback control.

On the other hand, the PMC CPU 22 keeps the NC CP during the compression.
It is determined whether a pulse distribution end signal from the U21 to the shared RAM 30 has been written to the compression completion position, or an in-position signal indicating that the compression position has entered the in-position width (step S6). ), If these signals are not written and the core 4 has not reached the compression completion position, it is judged whether or not the NG timer TN has timed up (step S7), and if not, to step S6. Returning to step S6, S7 is repeated. And N
If the core 4 reaches the commanded position, that is, the compression completed position before the G timer TN times out, the error between the commanded position and the current position disappears, so the servo motor 10 stops at that position and the torque of the set torque limit value is reached. To the core 4, hold the core 4 at the position, and wait until the compression timer Tp expires (step S8). And the compression timer Tp
When the time elapses, the process of this compression process ends.

While performing pressure control in this way, position control (compression position control) is also performed.

On the other hand, when the NG timer TN times out before the core 4 reaches the command compression completion position (step S7), this occurs when the amount of resin filled in the cavity is large. At this time, a signal indicating that the molded product is a defective product is sent and defective product processing such as writing in the shared RAM 30 is performed (step S9), and the processing of the compression process is ended. When the defective product signal is sent, the molded product is taken out from the mold separately from the non-defective product.

The above is the operation in the compression process, but the position of the core 4 when the compression process is started may be at the position B where the volume is larger than the cavity volume at the compression completion position A (see FIG. 1), and in particular, The position of the core 4 before the start of injection may be any position, but the cavity volume is smaller than the compression completion position A (the position on the right side of the compression completion position A in FIG. 1).
If it is, it becomes a form of vacuum forming, and it becomes easy to remove air.
In this case, at the time of injection, the torque limit value of the servo motor 10 is reduced or the servo is turned off to perform injection, and the core 4 is moved leftward in FIG. It may be moved to the position B where the cavity volume increases.

In the above embodiment, an example in which the compression pressure is not changed during the compression process has been described. However, the compression pressure may be switched in multiple stages. In this case, if the compression pressure is changed according to the position of the core 4, for example. By doing so, the compression pressure switching position of each stage and the torque limit value of the compression pressure of each stage are shared in advance in RAM 30.
, The position of the core 4 (position of the servomotor 10) is detected while repeating the processing of steps S6 and S7 in FIG. 1, and the torque limit is reached each time the core 4 reaches the switching position of each stage. The value may be switched to the next set torque limit value.

Further, although the core 4 is moved to compress the resin in the above-described embodiment, the same method as the conventional method of moving the movable die to compress the resin may be used.

EFFECTS OF THE INVENTION The invention described in claims 1 to 4 changes the pressure for compressing the resin in the mold in accordance with the position of the compression member during the period from the start of injection to the end of the holding pressure, and the compression is performed. Since both pressure control and compression position control are performed, transferability and dimensional accuracy can be ensured. If the dimensional accuracy cannot be ensured, the molded product can be determined as a defective product. Moreover, since the compression means is driven by the servo motor and the position is feedback-controlled, the position of the compression member is held even if the compression member receives the resin pressure, and thus the accurate position control can be performed. Further, since the position detector for detecting the rotational position of the servo motor can easily detect the position of the compression member, the compression pressure can be easily switched depending on the position of the compression member.

[Brief description of drawings]

FIG. 1 is a process flow chart of a compression process according to an embodiment of the present invention, and FIG. 2 is a block diagram of essential parts of an injection molding machine for carrying out the same embodiment. 1 ... Mold, 4 ... Core, 10 ... Servo motor, 20 ... Numerical control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuaki Neko 3-5-5 Asahigaoka, Hino City, Tokyo Inside the Product Development Laboratory, Fanuc Co., Ltd. (56) Reference JP-A-61-205111 (JP, A) JP Sho 63-9523 (JP, A)

Claims (4)

(57) [Claims] 1. A molding control method for an injection molding machine, comprising: a compression means for compressing a resin in a mold; and a servomotor for driving the compression means via a means for converting a rotary motion into a linear motion. A position detector for detecting the rotational position of the servo motor to detect the position of the compression means,
The position of the compression means is feedback-controlled, and the servo motor is driven to advance the compression means between the start of injection and the end of the pressure holding, and the amount of money generated by the servo motor is increased according to the position detected by the position detector. While controlling by switching the pressure to press the resin in the mold to single-stage or multi-stage,
A molding control method for an injection molding machine, characterized in that the resin in the mold is compressed until the set position is detected by the position detector, and both position control and pressure control are performed. 2. The injection molding according to claim 1, wherein if the resin is not compressed to a set position within a set predetermined time after the driving of the compression means, the molded product is judged to be defective. Molding control method of machine. 3. The molding control of an injection molding machine according to claim 1, wherein the compression means is composed of a moving member that moves in a mold that is clamped to compress the resin in the mold. Method. 4. The molding control method for an injection molding machine according to claim 1, wherein the compression means is also used as mold clamping means for moving the movable side mold to clamp the mold. .