JP3282437B2 - Injection compression molding method and control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method in which a molten resin is injected and filled into a mold which has been clamped at a low pressure, the mold is slightly opened by the filled resin pressure, and then compression is performed on the mold clamping side. The present invention relates to a compression molding method and a control device.

[0002]

2. Description of the Related Art Conventional injection compression molding has been performed by the following method. (1) The mold clamping is completed with the toggle mechanism fully extended, and a predetermined gap is secured in the mold in this state.
Then, after the molten resin is injected and filled into the mold, compression is performed by a hydraulic cylinder dedicated to compression or the like separately provided on a movable platen or a fixed platen. (2) The crosshead position of the toggle mechanism and the displacement of the movable plate (die opening, mold clamping force) when the toggle mechanism is not fully extended
Using the geometrical relationship of the above, control is performed based on the set value obtained by converting the mold clamping force set value at which the mold is opened by injection filling to the crosshead retreat position, and the toggle mechanism is stopped by this control. After the tightening, the molten resin is injected and filled in the mold, and thereafter, the compression is performed by re-driving the toggle mechanism so that the resin is fully extended.

[0003]

However, the conventional injection compression molding has the following problems. (1) Although no special modification is required on the toggle mechanism side, it is necessary to incorporate and remodel it into a molding machine such as a hydraulic cylinder dedicated for compression separately from the toggle mechanism, which increases the complexity and cost of the molding machine. Invite. For this reason, a method is considered in which only the compression mechanism is unitized so that it can be attached to and detached from the movable platen or fixed platen of the molding machine. Since the function of the molding machine main body is reduced, the moldable range is limited.

(2) The geometric relationship between the crosshead position of the toggle mechanism and the amount of displacement of the movable platen is determined by a mold thickness set value according to the thickness of the mold to be mounted and a mold clamping according to the size of the mold. Since the relational expression exists infinitely depending on the combination of die height adjustment values that increase or decrease the maximum generated mold clamping force at the time of completion, it must be calculated based on the geometric relationship for each mold used,
Operability is extremely poor and impractical. Furthermore, since the most important control of the mold opening in the injection compression molding is the setting of the mold clamping force based on the calculated and estimated value, it is necessary to accurately control the mold opening that the mold is opened by injection filling during actual molding. Without
Therefore, when switching to high-pressure mold clamping, advanced timing control such as interlocking operation between the injection side and mold clamping side is required so that there is no change in the resin flow rate in the mold, and stable supply of high quality molded products It is difficult to do.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a high-precision mold opening amount control without significantly modifying the existing molding machine of a toggle mechanism. It is an object of the present invention to provide an injection compression molding method and a control device capable of stably and continuously supplying quality products.

[0006]

According to the present invention, in order to achieve the above object, in the first invention according to the present invention, a tie bar is provided.
Injection with toggle- type mold clamping mechanism with elongation detector
An injection compression molding method performed by using a molding machine, wherein a tie bar is extended to a mold opening amount corresponding to a cooling solidification shrinkage amount of a resin by a resin pressure of a resin filled in a mold cavity. Is set to a mold clamping force that can be opened
Thereafter, injection filling is performed, and after completion of the injection filling, the mold clamping operation is continued again to perform compression. Further, in the second invention, the detection is made based on the time at which the ultrasonic signal irradiated from the tie bar end face to the opposite end face side is reflected. Furthermore, in the third invention, a mold opening amount setting unit that has an injection control unit that controls injection filling and a mold clamping control unit that controls mold clamping, and sets a mold opening amount corresponding to the amount of cooling, solidification, and shrinkage of the resin. And the tie-bar elongation amount detection unit consisting of an ultrasonic sensor incorporating the tie-bar elongation amount and an ultrasonic wave transmission / reception unit for counting the signal from the sensor, the set value of the die opening amount setting unit And a comparison control unit for generating a mold clamping holding signal to the mold clamping control unit and an injection start signal to the injection control unit based on a detection signal of the tie bar extension amount detection unit.

[0007]

After the tie bar elongation during the mold clamping operation reaches the mold opening set value corresponding to the amount of the resin solidifying and shrinking, the mold clamping operation is stopped and held, and the resin amount obtained by adding the shrinkage is reduced. By injection filling, the mold is almost completely filled with resin (just pack). Therefore, even when switching the compression process, there is no occurrence of defects such as flow marks due to discontinuous resin flow velocity in the mold. Becomes Therefore, it is not necessary to perform an extremely sophisticated timing control for switching the compression process, which is conventionally required.

The most important control of the mold opening (elongation of the tie bar) in the injection compression molding is performed by the tie bar elongation detecting unit incorporated in the tie bar, so that the influence of the mold thickness set value and the die height adjustment value can be reduced. Since it is possible to directly detect the mold opening amount (tie bar elongation amount) with high accuracy without receiving it at all, it is possible to control injection compression molding with high accuracy. Furthermore, since the tie bar elongation is detected using an ultrasonic signal and controlled by the reflection time of the reflected wave signal from the end face of the tie bar, the ultrasonic signal propagating inside the tie bar is extremely fast. The detection response of the elongation amount is extremely high, and continuous detection corresponding to the molding operation is possible. Further, since the processing of the ultrasonic signal is performed only by counting the reflection time, complicated arithmetic processing is not required, and highly accurate detection of the mold opening amount can be performed with simple software and hardware.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An injection compression molding method and a control device according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a control diagram of an injection molding machine according to the present invention,
2 is a diagram showing the relationship between the amount of tie bar elongation and the set mold clamping force in the toggle mold clamping device, FIG. 3 is a conceptual diagram of detecting an ultrasonic signal, and FIG.
Is a control flow diagram.

The injection molding apparatus 100 according to the present embodiment
Toggle type mold clamping device 50, injection device 40, and control unit 60
It is composed of

FIG. 1 shows an injection molding apparatus 100 provided with a toggle-type mold clamping device 50. The upper half of the center line shows the mold clamping state before injection filling, and the lower half of the center line after the completion of the compression step. This shows a mold clamping state. 1 includes a link housing 1, a fixed platen (fixed platen) 2, a movable platen (movable platen) 3, a mold 4 (fixed mold 4b and movable mold 4a), a cavity 5, and a toggle. It comprises a mechanism 6, a crosshead 7, a mold clamping cylinder (die lock cylinder) 8, a piston rod 9, and a guide rod 10.

In the injection molding apparatus 100 provided with the double toggle type mold clamping device 50, as shown in FIG. 1, three toggle links 6a are provided between the movable platen 3 and the link housing 1.
A pair of upper and lower toggle mechanisms 6b and 6c are provided, and a mold clamping cylinder (die-lock cylinder) 8 is mounted substantially at the center of the outer end surface of the link housing 1, and the tip of the piston rod 9 of the mold clamping cylinder 8 is crossed. A guide rod 10 connected to the head 7 and having the crosshead 7
And the toggle mechanism 6 is operated via the crosshead 7 to move the movable platen (movable platen) 3 with respect to the fixed platen 2 to perform a mold clamping operation. . Reference numeral 11 indicates a tie bar.

Next, the injection device 40 will be described. In this embodiment, the injection device 40 includes a screw 4 in a barrel 41.
2 is provided, and the resin material in the hopper 43 is supplied to the supply zone,
It is configured to be heated and compressed in a compression zone, melt metered in a metering zone, and injected into a nozzle 44 via an injection zone.

A heater for externally heating the resin material is provided on the outer peripheral surface of the barrel 41, and the resin material is fed forward by the rotation of the screw 42.

Reference numeral 46 denotes an injection cylinder, and 47 denotes a forward / reverse rotation motor which is directly connected to the screw 42 so as to rotate the screw 42 forward / reverse.

Next, the control unit 60 will be described. The control unit 60 includes a mold clamping control unit 61, a mold clamping cylinder stroke sensor 62, an injection control unit 63, a mold opening amount setting unit 64, a tie bar elongation amount detecting unit 65, an ultrasonic wave transmitting / receiving unit 66 and a comparison control unit 67, a hydraulic control. Valves 68, 69, hydraulic supply sources 70a, 70
b, an ultrasonic sensor 71.

The injection control section 63 is connected to a hydraulic control valve 69 for controlling the operation of the injection cylinder 46, and the injection control section 63 is connected to a comparison control section 67.

The tie-bar elongation detecting unit 65 detects the tie-bar elongation in the mold clamping process, and the ultrasonic transmission / reception unit 66 incorporated in the tie bar 11 is connected to the tie-bar elongation detection unit 65. The unit 64 is connected to the comparison control unit 67.

A mold clamping cylinder stroke sensor 62 is provided on the side of the mold clamping cylinder 8 opposite the crosshead 7 on the way of the piston rod 9 and is connected to the mold clamping control unit 61. When the set tie bar extension amount is reached, It is used as a means for fixing the operation of the mold clamping cylinder 8 by detecting the stroke of the mold clamping cylinder 8 and holding the position. The mold clamping control section 61 is connected to the comparison control section 67.

The operation of the injection compression molding apparatus configured as described above will be described.

The mold opening amount corresponding to the amount of cooling, solidification, and shrinkage of the resin by injection filling calculated from the mold cavity volume, the cavity projected area, and the physical properties of the resin to be filled is set as the tie bar elongation by the mold opening amount setting section 64. .

In this case, the toggle mechanism 6 is in a state where it is not fully extended, and the relationship between the tie bar extension amount and the set mold clamping force will be described in detail with reference to FIG.

That is, the principle of generation of the mold clamping force in the toggle-type mold clamping device 50 is as follows: the toggle mechanism 6 is driven to move the movable platen 3 forward, and the movable mold 4a and the fixed mold 4b are touched (at this time, The toggle mechanism 6 has not yet fully extended, Ko value), and the movable platen 3 is further pressed toward the fixed platen 2 to extend the tie bar 11 (the mold clamping cylinder 8 is advanced) to generate a mold clamping force. . The mold clamping force is the maximum value in the state where the toggle mechanism 6 is fully extended (however, when the die height is adjusted to the mold clamping force value according to the cavity projection area by the mold size to protect the mold, Kma
x value). At this time, the tie bar 11 has the maximum value (△ lm
ax value).

In the case of performing the injection compression molding by utilizing the extension of the tie bar 11, the maximum allowable extension (△ lmax value) of the tie bar 11 becomes a range in which the mold opening can be adjusted by the injection filling pressure. By detecting the amount, accurate mold opening amount control can be performed.

Assuming that the mold opening amount (tie bar elongation amount) corresponding to the cooling solidification shrinkage amount of the resin at the time of completion of injection filling is an S value, the tie bar elongation amount (（lmax value) smaller than the maximum tie bar elongation amount (△ lmax value). Mold clamping state (Ks
Value), the mold opening amount S value can be secured.

Next, a case where the tie bar elongation is measured using an ultrasonic signal will be described with reference to FIG.

The ultrasonic signal emitted from the ultrasonic sensor 71 attached to the end surface of the tie bar 11 toward the opposite end surface propagates inside the tie bar 11, is reflected at the opposite end surface of the tie bar 11, and returns to the ultrasonic sensor 71 again. When this state is observed on a screen using, for example, a digital oscillograph scope, the transmitted signal from the ultrasonic sensor 71 shows a peak value as a transmitted wave signal, and the reflected received signal to the ultrasonic sensor is a reflected wave signal. Shows the peak value.

Here, the mold clamping force Kmax is compared with the reflection time (to value) of the reflected wave signal (△ lo value) at the time of the mold clamping force Ko value (tie bar elongation amount △ lo value) shown in FIG. Value (△ l
The reflection time (tmax value) of the reflected wave signal (△ lmax value) at the time of (max value) becomes longer as the Δtmax value. That is, the propagation speed of the ultrasonic signal propagating inside the tie bar (about 5300 m / sec when the tie bar material is steel) is constant under the environmental conditions in which a normal molding machine is used, and is not affected by disturbance factors at all. Tie bar extension (△ lmax
Value) = the amount of change in reflection time (Δtmax value).

Therefore, the change of the reflected wave signal during the mold clamping operation (△ lo → 型 max) is monitored, and the mold opening amount (S
(Δt value, which is obtained by calculating the propagation speed of the ultrasonic signal from the tie bar length or utilizing the linear relationship between the Δlmax value and the Δtmax value) The reflected wave signal (△ l
By detecting the reflection time (ts value) of the s value), accurate mold opening amount control can be performed.

Further, since the detection of the ultrasonic signal only measures the reflection time of the reflected wave signal, in practice,
The digital oscilloscope or the like used in the description of FIG. 3 is unnecessary, and the ultrasonic sensor 71 is provided with an ultrasonic sensor 71 and an ultrasonic receiving / transmitting unit 6 having a function of receiving and transmitting an ultrasonic signal and counting a reflection time.
6, a simple software and hardware configuration is sufficient, and cost reduction is possible.

The following are conceivable advantages of detecting the tie bar elongation amount using the ultrasonic signal. Since the propagation speed of the ultrasonic signal is extremely high, the detection response is high, and as a result, the tie bar 1 during the mold clamping operation for a short time is used.
1 can be detected without delay. Since the propagation speed of the ultrasonic signal is extremely high, the detection resolution is high and the mold opening amount can be detected with high accuracy. There is almost no change in the propagation speed of the ultrasonic signal within the practical range, and highly reliable measurement that is strong against disturbance factors can be performed. Since the measurement can be performed only by fixing the ultrasonic sensor to the tie bar, no modification of the molding machine is required. Also, since the ultrasonic sensor is extremely small, it does not cause waste in space.

Incidentally, the following are desirable as the specifications of the ultrasonic measurement. Ultrasonic sensor: frequency = 5 MHz, sensor diameter = 1 /
2 inches-The higher the frequency, the higher the straightness, but the shorter the propagation distance. -The smaller the sensor diameter, the higher the beam quality, but the lower the signal level. Ultrasonic transmission / reception unit: A unit that can control the ultrasonic signal in pulses

Although FIG. 3 shows the transmitted wave signal and the reflected wave signal in the same phase for easy explanation, the actual reflected wave signal has the opposite phase for the following equation (1).

[0035]

(Equation 1)

Here, Z1 and Z2 indicate the acoustic impedance (kg / m ² · s) of the object through which the ultrasonic signal propagates.
The reflected wave signal passes through the tie bar 11 (Z1) → air (Z2), so that Z1 of the tie bar 11 (iron) becomes 45.
Since 3 × 10 ⁶ and Z 2 of air are 4 × 10 ² , when these values are substituted into the above equation, the sound pressure reflectance (Rp) becomes negative and has an opposite phase.

Next, the molding operation of this embodiment will be described with reference to FIG.

(1) The mold clamping control section 61 controls the oil pressure of the mold clamping cylinder 8 to perform mold clamping based on the mold opening amount set value of the mold opening amount setting section 64. During the mold clamping operation, the tie-bar elongation detecting unit 65 monitors the tie-bar elongation. (2) After detecting that the tie bar elongation amount has reached the set value (ts), the comparison control unit 67 transmits a mold clamping holding signal to stop and hold the mold clamping operation. In this case, for example, the stroke value of the mold clamping cylinder 8 is detected by the mold clamping cylinder stroke sensor 62, the hydraulic pressure of the mold clamping cylinder 8 is controlled, and the mold clamping cylinder 8 position holding control is performed.

(3) At the same time, the comparison control section 67 transmits an injection start signal to the injection control section 63, and based on the injection filling amount set value (the resin amount obtained by adding the cooling, solidification and shrinkage amount of the resin) set previously. Perform injection filling. (4) Mold opening behavior due to injection filling (tie bar 11 extends)
When the injection is completed, the mold opening amount previously set (corresponding to the amount of resin solidification shrinkage upon cooling) is obtained. By doing this,
Since the mold is almost fully filled with resin (just pack), there is no occurrence of defects such as flow marks due to discontinuity of the resin flow rate in the mold even when the compression process is switched. Therefore, it is not necessary to perform an extremely sophisticated timing control for switching the compression process, which is conventionally required.

(5) It is to be noted that the tie bar elongation at the time of the completion of the injection is detected and, for example, when there is a slight deviation from the set value of the mold opening, or based on the result of the quality judgment of the molded product after the product is taken out. When it becomes necessary to correct the mold opening, the tie-bar elongation detecting unit 65 can transmit a mold opening correction signal to the mold opening setting unit 64 to perform the correction.

(6) After the injection filling is completed, the mold clamping is restarted to perform high-pressure mold clamping, and compression is started. In this case, when the injection is completed, the resin is in a just-packed state, and the elastic recovery force due to the tie bar extension is continuously continued in response to the cooling, solidification, and shrinkage of the resin, so that a time lag occurs at the start of compression. No defects such as flow marks occur.

(7) The compression step and the injection side control are performed, for example, at a set time of a timer which starts after detecting completion of injection filling. Start of measurement: Based on the gate sealing time, when the shut-off valve is installed, the shut-off valve closing operation completion time. Cooling completion: The cooling time of the resin is calculated based on the resin temperature, the mold cooling capacity, the shape of the molded product, and the like, and is set as the compression completion time. (8) After the cooling is completed, the mold is opened to take out the product.

[0043]

As is apparent from the above description, the injection compression molding method and the control apparatus according to the present invention include: (1) detecting the amount of tie bar elongation during the mold clamping operation to cool, solidify, and shrink the resin; As soon as the mold opening amount set value corresponding to is reached, the mold clamping operation is stopped and held, and the resin in the mold is in a just-packed state by injection-filling the resin amount obtained by adding the shrinkage amount. There are no defects such as flow marks due to the discontinuity of resin flow,
As a result, extremely sophisticated timing control at the time of switching the compression process becomes unnecessary, and the operability is simplified. (2) Since the most important control of the mold opening (tie bar elongation) in injection compression molding is performed directly using ultrasonic signals,
High-response and high-precision mold opening control without fluctuations due to disturbance factors can be performed, and as a result, extremely high-quality molded products can be continuously supplied. (3) Since it is only necessary to attach an ultrasonic sensor to the current toggle-type mold clamping molding machine, there is no need to modify the molding machine at all, and it can be converted to an injection compression molding machine that can be controlled with high precision with one touch, greatly reducing costs. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a control diagram of an injection molding machine according to the present invention.

FIG. 2 is a relationship diagram between a tie bar elongation amount and a set mold clamping force in a toggle-type mold clamping device.

FIG. 3 is a conceptual diagram of detection of an ultrasonic signal.

FIG. 4 is a control flowchart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Link housing 2 Fixed board 3 Movable board 4 Mold 4a Movable mold 4b Fixed mold 5 Cavity 6 Toggle mechanism 7 Crosshead 8 Mold clamping cylinder 9 Piston rod 10 Guide rod 11 Tie bar 40 Injection device 41 Barrel 42 Screw 43 Hopper 44 Nozzle 46 Injection cylinder 47 Forward / reverse rotation motor 48 Injection piston 50 Toggle type mold clamping device 60 Control unit 61 Mold clamping unit 62 Mold clamping cylinder stroke sensor 63 Injection control unit 64 Mold opening setting unit 65 Tie bar extension amount detection unit 66 Ultra Sound wave transmission / reception unit 67 Comparison control unit 68, 69 Hydraulic control valve 70a, 70b Hydraulic supply source 71 Ultrasonic sensor

Claims (3)

(57) [Claims] 1. A toggle type having a tie bar elongation detector .
An injection compression molding method using an injection molding machine with a mold clamping mechanism, in which the tie bar extends to the mold opening amount corresponding to the resin's cooling solidification shrinkage amount due to the resin pressure of the resin filled in the mold cavity.
Set the mold clamping force that can be mold is opened by that
After that, injection molding is performed, and after the injection filling is completed, compression is performed by continuing the mold clamping operation again to perform compression. 2. The injection compression molding method according to claim 1, wherein the amount of elongation of the tie bar according to claim 1 is detected based on a time at which an ultrasonic signal irradiated from the end surface of the tie bar toward the opposite end surface is reflected. 3. An injection control section for controlling injection filling, a mold closing control section for controlling mold clamping, and a mold opening amount setting section for setting a mold opening amount corresponding to an amount of cooling, solidification and shrinkage of resin. The detection of the tie-bar elongation is performed by a tie-bar elongation detection unit including an ultrasonic sensor incorporated in the tie bar and an ultrasonic transmission / reception unit that counts a signal from the sensor. An injection compression molding control device, comprising: a comparison control unit that generates a mold clamping holding signal to the mold clamping control unit and an injection start signal to the injection control unit based on a detection signal of a tie bar elongation amount detection unit.