JPH0753404B2 - Holding pressure control method and apparatus for injection molding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holding pressure control method and apparatus for injection molding.

[0002]

2. Description of the Related Art Injection molding is performed under various temperature changes such as seasonal changes and morning and evening temperature changes. These temperature changes mainly appear as the mold temperature and the temperature change of the molten resin that is the molding material that enters the mold, and along with this,
The heat history of the resin changes until it is filled in the mold, cooled and solidified, and taken out. Changes in the thermal history of the resin in the mold change the viscosity and density of the resin, resulting in, for example, changes in resin pressure within the mold. As a result, the weight and size of the molded product vary, and the reproducibility of the quality of the molded product is impaired.

Conventionally, as a means for solving the problem caused by such a temperature change, a pressure sensor is mounted in the mold, the resin temperature in the mold is calculated from the wall thickness of the molded product, the effective thermal diffusivity, etc., and the molding material ( PVT which is basic physical property data showing the relationship between the pressure (P) of the resin), the specific volume (V) and the temperature (T).
It is known to control the specific volume of a molded product so as to match the target value based on the characteristic data regardless of temperature change (Japanese Patent Laid-Open Nos. 63-3926 and 63-39).
No. 27).

[0004]

SUMMARY OF THE INVENTION In the above conventional technique,
In either case, it is necessary to mount the resin pressure sensor in the mold, which is not economical, and moreover, adjustment and mounting of this pressure sensor are troublesome.

Further , as in the conventional case, the resin pressure in the mold is measured.
The measured resin pressure in the mold is the same as the preset value.
Method to control the holding pressure of the machine, that is, the mold
In the feedback control method of the internal resin pressure,
The resulting effect on quality may be limited. why
In that case, the molten resin filled in the mold is suddenly removed from the mold wall.
Since the heat is taken away quickly and it is cooled, the fluidity of the molten resin
Rapidly decreases and solidifies. How much holding pressure at this point
This is because the resin pressure inside the mold does not change even if the force is changed.
is there. In addition to this, the resin pressure in the mold is measured and the
In the feedback control method, a certain responsiveness is ensured.
Therefore, a hydraulic servo valve and an amplifier for the hydraulic servo valve are required.
It is important. These are usually expensive and impair economics.
There will be cases where it will be added .

Furthermore , since the conventional formula for calculating the resin temperature in the mold is an approximate formula, the calculation precision is poor, and as a result, the quality of the molded product cannot be controlled with high precision. Further , in calculating the resin temperature in the mold, additional data such as the wall thickness of the molded product and the effective thermal diffusivity are required, which causes a problem that it takes time to collect these data.

The present invention has been made in view of the above-mentioned problems of the prior art. It is not necessary to mount a pressure sensor in the mold, and the resin pressure in the mold is measured to feed the resin.
No need to control back, hydraulic servo valve and servo
Without requiring a valve amplifier, also, the wall thickness of the molded article, without the need for additional data, such as effective thermal diffusivity, and conventional inexpensive
Hydraulic electromagnetic flow control valve, electromagnetic pressure control valve, electromagnetic proportional valve, etc.
It is an object of the present invention to provide a holding pressure control method and device capable of controlling the quality of a molded product with high accuracy by using the method.

[0008]

In order to achieve the above object, the method for controlling the pressure holding according to the present invention is such that a molten resin in a cylinder of an injection molding machine is heated sequentially by advancing a screw.
Inner reservoir, nozzle resin flow path, spool, runner
Supplement parts, the filling phase to be injected into the cavity of the mold through a gate portion, after filling the molten resin into the cavity portion, the to shrink as the molten resin is cooled and solidified within the cavity Therefore, in injection molding having a pressure-holding step of pressing the screw to replenish the molten resin, the measured value of the mold temperature in the filling step and the inside of the heating cylinder that is the resin flow path. Reservoir, nozzle
Resin flow path, spool, runner, gate or key
At the filling stage in any one of the cavity parts
Based on the measurement values of the definitive resin temperature, end of the filling phase
The in- mold resin temperature required to achieve the target product weight is estimated by estimating the in-mold resin temperature at an arbitrary time in the pressure-holding stage starting from the end time (time 0). calculated from the inner resin temperature, to achieve the type in resin pressure
A required holding pressure set value is calculated, and the holding pressure is controlled based on the holding pressure set value in the holding pressure stage.

In the pressure-holding control method of the present invention, the resin temperature in the mold at the pressure-holding stage is expressed by T (t) = Ts (t) + {Trs-Ts (t)} (Tw
-Tws) / (Trs-Tws) + {Ts (t) -Tw
s} (Tr-Trs) / (Trs-Tws) where T (t): in the mold at the pressure holding stage in any molding shot
Resin temperature (however, the value corresponding to the measured value of Tw, Tr
It is. ) Tw: Measured value of mold temperature in filling stage Tws: Filling in shot when good product is molded
Measured value of mold temperature Tr in stages : Reservoir in the heating cylinder, which is a resin flow path , nozzle
Resin flow path, spool, runner, gate or key
At the filling stage in any one of the cavity parts
That measured values of the resin temperature Trs: Filling a shot when a non-defective molded
Measured value Ts (t) of the resin temperature in any one of the resin flow paths of the stage : in a shot when a good product is molded
Resin temperature in mold during pressure- holding stage : starting point at time of pressure- holding stage (end of filling stage) (time)
It is possible to estimate the time as 0) . This expression is a formula that does not include the approximation errors, the heat transfer engineering hand
It was derived by law.

[0010] In the holding pressure control method of the present invention, shot to your Keru mold resin temperature Ts when the good has been molded
Holding pressure but a fixed time tg reaches the flow stop temperature Tg
Used as the time to evaluate the resin temperature in the mold in the stage ,
Mold resin temperature T (t of the time tg which definitive in each shot
g) is estimated .

However, the time tg in the pressure holding stage is a variable
Assuming its existence as
You don't need to ask. Generally in the holding stage
The in-mold resin temperature Ts (t) is the same as that of the resin in the filling step.
The upper limit of the resin temperature Trs in any one of the flow paths
As a result, it is empirical to decrease the mold temperature Tws.
Is obvious. In addition, the flow stop determined by the resin material
The stop temperature Tg is lower than Trs and higher than Tws.
It is common to hear. Therefore, tg that satisfies the following equation
Can always be assumed to exist.

Ts (tg) = Tg On the other hand, if the existence of tg can be assumed,
Resin temperature in the mold at the time tg of the pressure holding stage in shot
The degree is given by the following formula.

T (tg) = Tg + (Trs−Tg) ·
(Tw-Tws) / (Trs-Tws) + (Tg-Tw )
s) · (Tr−Trs) / (Trs−Tws) where Tg is a temperature given as a numerical value, and the right side
Others are given as measurements at the filling stage.
It is what is done. Therefore, to find T (tg)
In addition, since tg as a numerical value is not used, it is not necessary.
Yes.

Furthermore, the holding pressure control method of the present invention is a holding pressure stage.
It is possible that the in- mold resin pressure and the in-mold resin temperature at the floor are expressed as a function form of the in-mold resin specific volume.

The pressure-holding control device of the present invention is a pressure-holding control device for an injection molding machine, wherein a mold temperature sensor for detecting the temperature of the mold and a heating cylinder in the heating cylinder which is a resin flow path are used.
Bar, nozzle resin flow path, spool, runner, gate
Filling in either one of the cavity or cavity
Resin temperature sensor for detecting the temperature of the molten resin in the step , charging the mold temperature sensor and the resin temperature sensor.
Based on the detected values in Hama step estimates the mold resin temperature in the dwell pressure phase, obtains the mold resin pressure required to achieve the product weight to the target from the estimated-mold resin temperature, the Holding pressure setting required to achieve resin pressure in the mold
The present invention is characterized by having an arithmetic processing unit that calculates a constant value and a holding pressure control unit that performs holding pressure control based on the holding pressure set value obtained by the arithmetic processing unit.

[0016]

[Action] mold resin temperature in the pressure holding step, the filling phase
Resin temperature of the mold temperature and resin passage definitive can be estimated by knowing. It is known that the relationship between the resin pressure in the mold, the resin temperature in the mold, and the specific resin volume in the mold is expressed in various forms, and the specific resin volume in the mold is obtained from the weight of the molded product. Then, the resin pressure in the mold required to obtain the target value of the molded product weight is the relationship between the resin pressure in the mold, the resin temperature in the mold, and the resin specific volume in the mold, and the target value of the molded product weight and the mold. It can be obtained from the estimated value of the inner resin temperature. Furthermore, mold resin pressure, die temperature, can be approximated at a resin temperature and the coercive pressure setpoint of the resin flow path. Thus, holding pressure setting value required to obtain the target value of the molded product weight, without the need for pressure sensors and additional data, it can be determined based on the resin temperature of the mold temperature and resin flow path it can.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory view showing an embodiment of the present invention. The screw 1 is constructed so that it can be moved forward and backward in the cylinder 12 by the driving force of a hydraulic cylinder 9 in the left-right direction in the figure. The nozzle 2 provided at the tip of the cylinder 12 is formed with a nozzle resin flow path 2a which communicates with the reservoir 12a in the heating cylinder and the mold 3.
Consists of a fixed mold 3a and a movable mold 3b,
Its interior, in order from the side close to the nozzle 2, spool over <br/> Le portion 3c, runner portion 3d, the gate portion 3e and the cavity portion 3f is formed.

A resin temperature sensor 5 is attached to the nozzle resin flow passage 2a, a fixed mold temperature sensor 4a is mounted on the fixed mold 3a, and a movable mold 3b is mounted on the movable mold 3b. The mold temperature sensors 4b for the movable side are attached respectively. The resin temperature sensor 5, if the resin flow path, in addition to the nozzle resin flow path 2a, the heating cylinder Li
Observers 12a, spool portion 3c, may be attached to any one place of the runner portion 3d or cavity portion 3f,. The signal output terminals of the resin temperature sensor 5 and the mold temperature sensors 4a, 4b are connected to the A / D converters 6d, 6 via the amplifiers 6a, 6b, 6c in the control device 6, respectively.
e and 6f, respectively, and each A / D converter 6
The output terminals of d, 6e, and 6f are connected to the respective input terminals of the arithmetic processing unit 6g.

The arithmetic processing unit 6g outputs the outputs of the A / D converters 6d, 6e, 6f and the constants a, b, c, d, e, f, πi, which will be described later, which are set in the setter 6h. ω,
The holding pressure setting value PL is calculated according to various setting values such as R ′, W, V, and the injection start signal S1 and the holding pressure switching signal S2 for measuring various timings output from the sequence control unit 8, It is composed of a microcomputer that outputs a digital signal to the pressure holding control unit 6i. The holding pressure control unit 6i converts the digital signal indicating the holding pressure setting value PL output from the arithmetic processing unit 6g into a voltage signal and outputs the voltage signal to the servo valve amplifier 7. The servo valve amplifier 7 is a holding pressure control unit. the value of the voltage signal output from 6i and pressure-holding force setting value, the hydraulic pressure sensor 11 for detecting the pressure of the hydraulic cylinder 9
The pressure of the hydraulic cylinder 9 is based on the detected value of
A control voltage is output to the servo valve 10 so as to reach the force set value.

Next, the calculation of the holding pressure set value PL by the arithmetic processing unit 6g will be described.

In the following calculation, the time point when the fixed-side mold 3a and the movable-side mold 3b are filled with the molten resin, that is, the time when the filling is completed (at the start of the holding pressure) is the time 0, and the elapsed time from the time 0. And the time thereof are represented by t, and in order to show that the in-mold resin temperature and the in-mold resin pressure, which will be described later, are functions of time, (t) is added to each symbol and T
(T), Ts (t), P (t), Ps (t). Then, in each shot, the die temperature Tw does not change in each shot, and the die temperature Tw is the die temperature Tw1 of the fixed side die 3a and the die of the movable side die 3b. Either the temperature Tw2 or the average of the two may be used, and in the mold temperature Tw, a value at a shot (hereinafter, referred to as “predetermined shot”) when a predetermined non-defective product is molded is a mold of a predetermined shot. The temperature is Tws. The mold temperatures Tw1 and Tw2 are the filling step.
At the start of filling, or as an average value during filling.
Further, among the resin temperatures in the filling stage output from the resin temperature sensor 5, the maximum value or the average value from the start of injection to the switching of the pressure holding, the sample value at the time of switching the pressure holding, or the sample value at the time of starting the injection. Any of the above in the filling stage
The resin temperature Tr in the resin flow path is set, and in particular, the value at the predetermined shot is set as the resin temperature Trs at the predetermined shot.

The average temperature in the thickness direction of the molded product in the mold at the time t in the predetermined shot is defined as the in-mold resin temperature Ts (t) of the predetermined shot, and in the shots other than the predetermined shot, the mold temperature changes from Tws. Tw to the resin channel
Heating cylinder reservoir 12a, nozzle resin flow path 2
a, spool portion 3c, runner portion 3d or cavity
At the filling stage measured at any one of the parts 3f
Kicking When the mold resin temperature when varied respectively from the resin temperature Trs to Tr and T (t), mold resin temperature T (t) and change before after variation (shots other than the predetermined shot) of (predetermined shot) Between the resin temperature Ts (t) in the mold, the following (1)
It can be considered that there is an expression relationship.

T (t) = Ts (t) + {Trs-Ts
(T)} (Tw-Tws) / (Trs-Tws) + {T
s (t) -Tws} (Tr-Trs) / (Trs-Tw
s) ··· (1) In addition to the one-dimensional infinite flat plate, the above equation (1) has a wall isothermal temperature of 2,
It also holds for three-dimensional prisms, rectangular parallelepipeds, semi-infinite flat plates, spheres, etc. Further, it is also established when considering the heat transfer coefficient between the resin and the mold wall surface .

In the heat conduction analysis of a one-dimensional infinite flat plate,
The resin temperatures Trs and Tr described above are interpreted as initial conditions.
Shall be used. Further, the mold temperature Tw and
Tws is interpreted and used as a boundary condition.

[0026] Here, the average resin density in the mold, the
Mold resin temperature Ts (t) is assumed which is determined by the conditions of the time reaching the flow stop temperature Tg, i.e. a mold resin pressure P at that time (t) and the mold resin temperature T (t) at a given shot . This is because the mass of the molding material filled in the mold at the flow stop temperature Tg is almost fixed, and high calculation accuracy can be expected. Further, the time at which the flow stop temperature Tg is reached in the predetermined shot is defined as the flow stop time tg at the predetermined shot. That is, time tg
Is defined as tg satisfying Ts (tg) = Tg
It Furthermore, in-mold resin pressure P (t), in-mold resin temperature T
The relationship between (t) and the in-mold resin specific volume v is expressed as a function form by the Spencer and Gilmore (Spence) of the following formula (2).
r & Gilmore).

{P (t) + πi} (v-ω) = R '{T
(T) +273} (2) where πi: internal pressure (kg / cm ² ) ω: absolute 0 degree specific volume (cm ³ / g) R ′: modified gas constant [(kg / cm ² · cm ³ /
g) / ° K], and v = V / WW: molded product weight (g) V: cavity volume (cm ³ ).

The upper internal pressure πi, the specific volume ω, and the modified gas constant R'are material constants determined by the material.

At the same time as the flow stop time tg of each shot, the in-mold resin pressure P1 (tg) required to obtain the target value W1 of the weight of the molded product is based on the above assumptions (1). The time t in the formula is the flow stop time tg
And the resin pressure P (t)
= P1 (tg), in-mold resin temperature T (t) = T (tg),
By setting the in-mold resin specific volume v = v1 (= V / W1), it is given by the following equation (3).

P1 (tg) = R ′ {T (tg) +27
3} / (v1-ω) -πi (3) In-mold resin pressure P ( tg ) in each shot is the mold temperature Tw of the shot, the resin flow path in the filling stage
By using the resin temperature Tr and the holding pressure set value PL in the above, the following equation (4) can be used for approximation.

P ( tg ) = a ₁ Tw + a ₂ Tw ² + b ₁
Tr + b ₂ Tr ² + cPL + d (4) However, a ₁ , a ₂ , b ₁ , b ₂ , c, d are constants set in advance for each shot.

In shots other than the above-mentioned predetermined shots, the holding pressure set value necessary to obtain the in-mold resin pressure P1 (tg) of the above formula (3), that is, to obtain the target value W1 of the weight of the molded product. PL1 is the mold temperature Tw measured in the shot and the resin in the filling stage.
By substituting the resin temperature Tr in the flow channel into the above (4), it is given by the following equation (5).

[0033] PL1 = {P1 (tg) -a 1 Tw-a 2
^{_{Tw 2 -b 1 Tr-b 2}} Tr 2 -d} / c
(5) The above formula (3) is replaced by the resin pressure P1 (t in the mold in the above formula (5).
Substituting into g), the holding pressure set value PL1 for obtaining the target value W1 of the weight of the molded product in each shot can be accurately obtained by calculation by the arithmetic processing unit 6g.

FIG. 2 shows the time variation of each state in the mold in this embodiment, (A) is a graph showing the time variation of the resin temperature T (t) in the mold, and (B) is the resin pressure in the mold. It is a graph which shows the time variation of P (t).

As shown in FIG. 2A, the in-mold resin temperature Ts (t) at a predetermined shot decreases monotonously after the pressure holding starts.
The resin temperature in the mold Ts (tg) = Tg at the elapsed time t when the pressure holding start time is 0 . Further, in the shots other than the predetermined shot, the in-mold resin temperature T (t) is T (t) = T ′ (t) for each shot depending on the mold temperature Tw and the resin temperature Tr in the resin flow path in the filling stage. ) Or T (t) = T ″ (t).

On the other hand, as shown in FIG. 2 (B), the in-mold resin pressure Ps (t) at a predetermined shot (shot when a predetermined non-defective product is molded) changes so as to draw a curved curve. In the shots other than the predetermined shot, the in-mold resin pressure P (t) becomes P (t) = P ′ (t) or P in each shot as the in-mold resin temperature T (t) changes.
(T) = P ″ (t).

However, in any variation, the holding pressure set value PL1 for obtaining the target value W1 of the weight of the molded product in each shot is obtained by the above calculation.

FIG. 3 is a flow chart showing the steps of the present embodiment. When the injection start signal S1 is output from the sequence controller 8 in the step of performing shots other than the predetermined shot (step 21), the pressure holding controller. 6i inputs this, and the screw 1 starts to advance to the left in FIG. At the same time, the injection start signal S1 is also input to the arithmetic processing unit 6g, and the arithmetic processing unit 6g receives the same until the pressure holding switching signal S2 is output from the sequence control unit 8 (step 24). From 5 to the filling stage
That the resin temperature of the resin flow path, each mold temperature sensor 4
The mold temperatures Tw1 and Tw2 are continuously input from a and 4b, respectively (steps S22 and S23).

[0039] Upon entering the hold pressure signal S2, the arithmetic processing section 6g is put into the filling stage the resin temperature of the resin passage from the resin temperature sensor 5 inputted up to that point
The resin temperature Tr in the resin flow path is calculated (step 25), and the mold temperature Tw is calculated from the mold temperature Tw1 of the fixed mold 3a and the mold temperature Tw2 of the movable mold 3b.
= (Tw1 + Tw2) / 2 is calculated (step 26).

The calculated value of Tr is the above-mentioned tree at the filling stage.
Of the measured values of the resin temperature in the oil passage, the pressure is maintained from the start of injection.
The maximum or average value until switching, and the sun when switching holding pressure.
Either the pull value or the sample value at the start of injection
It

Next, the arithmetic processing unit 6g estimates the in-mold resin temperature T (tg) at the flow stop time tg according to the above equation (1) (step 27), and the target product weight according to the above equation (3). In-mold resin pressure P1 required to achieve W1
(Tg) is calculated (step 28), and the holding pressure set value PL1 is calculated according to the above equation (5) (step 29).

After the above calculation is completed, the calculation processing unit 6g
Outputs a voltage signal corresponding to the holding pressure set value PL1 to the servo valve amplifier 7 via the holding pressure control unit 6i (step 3
0) In response to this, the servo valve amplifier 7 outputs an operating voltage to the servo valve 10 so that the hydraulic pressure of the hydraulic cylinder 9 becomes the hydraulic pressure corresponding to the holding pressure set value PL1 (step 31). When the pressure holding switching signal from the sequence control unit 8 is cut off, the arithmetic processing unit 6g and the pressure holding control unit 6 are operated.
i stops the output and ends the pressure holding control (step 3).
2).

In this embodiment, it is assumed that the relationship between the in-mold resin pressure P, the in-mold resin temperature T and the in-mold resin specific volume v is represented by the above Spencer-Gillmore equation of state. It is not limited to this.

For example, it is also possible to use the modified formula of Tait of the following formula (6).

1-v (P, T) / v (P0, T) = 0.
0894ln [1 + P / B ( T )]
(6) where v (T, P): Resin volume specific volume v in the above formula (2)
Corresponds to, in-mold resin temperature T and the mold internal resin pressure P also show that is a function of v in (T, P0): mold resin specific volume of in standard atmospheric pressure (1 atm) (hereinafter, "v0 B (T) = − B ₀ exp (−B ₁ T) B ₀ , B ₁ : Material constant From the above equation (6), the following equation (7) for obtaining the in-mold resin pressure P1 can be obtained. . P1 = B (T) {1-exp [(1 / 0.0894)
(1-v1 / v0)]} (7) Since the in-mold resin specific volume v0 at standard atmospheric pressure is obtained in advance, the above equation (7) is replaced by the above equation (3), The target value W of the weight of the molded product in each shot is used by directly using the equations (4) and (5) without changing them.
The holding pressure set value PL1 for obtaining 1 can be obtained.

Further, the following equation (8) of Breuer & Rehage can also be used.

V (P, T) = v ₀ + φ ₀ (T + 273)
_{- (K 0 / a) [} 1 + b (T + 273)] ln (1 + a
P) (8) where a, b: material constant v ₀ : resin temperature in mold T = 0 ° C., resin specific volume in mold at standard atmospheric pressure φ ₀ = (∂v / ∂T) _P , T = 0 ° C., value at standard atmospheric pressure K ₀ = (∂v / ∂T) _T , T = 0 ° C., value at standard atmospheric pressure The following for obtaining the in-mold resin pressure P1 from the above equation (8) ( Equation 9) is obtained.

P1 = (1 / a) [exp {[v1-v ₀
−φ ₀ (T + 273)] (a / K ₀ ) [1 + b (T + 27
3)]}-1] (9) The above equation (9) is replaced by the above (3).
By substituting the equation, the holding pressure set value PL1 for obtaining the target value W1 of the weight of the molded product in each shot can be obtained as in the equation (7).

[0049]

Since the present invention is configured as described above, it has the following effects.

It is not necessary to mount a pressure sensor in the mold, and the resin pressure in the mold is measured and feedback-controlled.
No need, need hydraulic servo valve and servo valve amplifier
In addition, the usual cheap hydraulic electromagnetic flow control valve and electromagnetic pressure control
It can be controlled using a control valve, a solenoid proportional valve, etc., and it does not require additional data such as the thickness of the molded product and the effective thermal diffusivity, so the cost for holding pressure control can be kept low. . As a result, the price of the molded product can be reduced.

[0051] Particularly, in the invention of claims 2 to 4, regardless of variations in mold temperature and resin temperature, since the molded product weight to the target always be obtained with high precision, stable and high-quality molded articles Can be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing a temporal change of each state in the mold in the present invention, (A) is a graph showing a time change of temperature, and (B) is a graph showing a time change of pressure.

FIG. 3 is a flowchart showing the steps of this example.

[Explanation of symbols]

1 screw 2 nozzle 2a nozzle resin flow path 3 mold 3a fixed mold 3b movable mold 3c spool portion 3d runner portion 3e gate portion 3f cavity 4a, 4b mold temperature sensor 5 resin temperature sensor 6 control Device 6a, 6b, 6c Amplifier 6d, 6e, 6f A / D converter 6g Arithmetic processing unit 6h Setting device 6i Pressure holding control unit 7 Servo valve amplifier 8 Sequence control unit 9 Hydraulic cylinder 10 Servo valve 11 Hydraulic sensor 12 Cylinder 12a Heating In-cylinder reservoir

Claims (5)

[Claims] 1. A molten resin in a cylinder (12) of an injection molding machine is sequentially heated in a heating cylinder by advancing a screw (1) .
Reservoir (12a), nozzle resin flow path (2a), spoo
Part (3c), runner part (3d), gate part (3e)
Filling step of injecting into the cavity part (3f) of the mold (3) through the mold, and the molten resin in the cavity part (3f)
The molten resin is filled in the cavity part (3f).
In order to compensate for shrinkage as it is cooled and solidified inside, there is a pressure-holding step of pressing the screw (1) to replenish the molten resin .
Kicking measured value of the mold temperature (Tw1, Tw2) and the resin flow
The heating cylinder internal reservoir (12a), which is a passage,
Resin flow path (2a), spool section (3c), runner section
(3d), gate part (3e) or cavity part (3
Based on the measured value (Tr) of the resin temperature in the filling stage in any one of f) ,
Estimate the in-mold resin temperature (T (t)) at an arbitrary time (t) in the pressure-holding stage starting from the end time (time 0), and then achieve the target product weight (W1). calculated from the estimated mold resin temperature-mold resin pressure required (P1 (t)) to (T (t)), the type in resin pressure (P1
Holding pressure setting value (PL1) required to achieve (t))
Is calculated, and at the holding pressure stage, the holding pressure set value ( PL
1 ) A holding pressure control method characterized by controlling the holding pressure based on 1 ). 2. The resin temperature in the mold (T
(T)), T (t) = Ts (t) + {Trs−Ts (t)} (Tw
-Tws) / (Trs-Tws) + {Ts (t) -Tw
s} (Tr-Trs) / (Trs-Tws) where T (t): in the mold at the pressure holding stage in any molding shot
Resin temperature (however, the value corresponding to the measured value of Tw, Tr
It is. ) Tw: Measured value of mold temperature in filling stage Tws: Filling in shot when good product is molded
Measured value of mold temperature at the stage Tr: Reservoir in the heating cylinder (12
a), nozzle resin flow path (2a), spool portion (3c),
Runner (3d), gate (3e) or cavite
At the filling stage in any one of the 3rd part (3f)
Measured value of the kick resin temperature Trs: Filling a shot when a non-defective molded
Measured value Ts (t) of the resin temperature in any one of the resin flow paths of the stage : in a shot when a good product is molded
Resin temperature in mold during pressure- holding stage : starting point at time of pressure- holding stage (end of filling stage) (time)
The holding pressure control method according to claim 1 , wherein the time is assumed to be 0) . 3. Contact the shot when the good has been molded
In-mold resin temperature (Ts (t)) is flow stop temperature (Tg)
Fixed time (tg) type in a dwell pressure stage reached
It is used as the time to evaluate the internal resin temperature and is used for each shot .
The holding pressure control method according to claim 2, wherein the in-mold resin temperature (T (tg)) at the time (tg) is estimated. 4. The resin pressure in the mold (P
(T)) and mold resin temperature (T (t)) is your holding pressure of claims 1 to 3 any one of claims and is represented as a functional form of the mold resin specific volume (v) Method. 5. A pressure control device for an injection molding machine, comprising:
Mold temperature sensor (4a, 4) for detecting the temperature of the mold (3)
b) and the resin flow pathReservoir in the heating cylinder (12
a), nozzle resin flow path (2a), spool portion (3c),
Runner (3d), gate (3e) or cavite
At the filling stage in any one of the 3rd part (3f)
KickResin temperature sensor (5) for detecting the temperature of molten resin
And the mold temperature sensor (4a, 4b) and the resin
Of temperature sensor (5)At the filling stageBased on each detection value
To estimate the resin temperature (T (t)) in the mold at the pressure holding stage
Then, from the estimated in-mold resin temperature (T (t)),
Resin pressure in the mold required to achieve the product weight (W1)
(P1(T)), and the resin pressure in the mold (P1
(T))Holding pressure setting value (PL1) required to achieve
To calculateAn arithmetic processing unit (6g) and the arithmetic processing unit (6
g) Calculated holding pressure set value (PL1) Based on pressure retention
And a holding pressure control unit (6i) for controlling
Pressure control device.