JP3240841B2 - Insulation control method for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control method for an injection molding machine for replenishing shrinkage due to cooling and solidification of a molten resin filled in a mold by pressurizing the same.

[0002]

2. Description of the Related Art In general, in an injection molding machine, a molten resin material used is a viscoelastic body whose specific volume fluctuates in accordance with temperature and pressure. In order to stabilize the quality of the molten resin, so-called pressure-holding control, which controls the pressing force corresponding to the cooling and solidification of the charged molten resin, is usually applied. This pressure-holding control is known, and this control includes the so-called P (pressure) of the molten resin.
Profile control based on a V (specific volume) -T (temperature) diagram, that is, a specific volume V is made constant in response to a change in temperature T via a specific volume V-temperature T diagram using pressure P as a parameter. (Hereinafter simply PV−V−)
T control) is conventionally suitably applied.

As described above, according to the PVT control, since the weight of the product is kept constant throughout the molding process, stable quality is ensured.

In this PVT control, P-
When known physical property data is not prepared for preparing a VT diagram, the physical property data must be measured in advance using a special measuring device each time. However, since such measurement requires a great deal of trouble, in order to eliminate this inconvenience, the data measurement and the creation of a diagram are performed using the injection molding machine during a preliminary test operation of the injection molding machine. (Hereinafter, referred to as a measurement method using an injection molding machine)
(For example, Japanese Patent Application Laid-Open No. 3-27752)
No. 2).

According to this measuring method using an injection molding machine, even if there is no physical property data, the P-
A VT diagram can be created.

[0006]

SUMMARY OF THE INVENTION However, the method for controlling the pressure holding of an injection molding machine according to the PVT control described above is as follows.
The measurement method using an injection molding machine also has the following disadvantages.

That is, first, in the PVT control, since the physical property data of the molten resin is temperature, pressure and specific volume, and the unit of the specific volume is the ratio of volume to weight, Since the PVT diagram is hyperbolic, the creation of the diagram and the process of functioning are complicated, and
There is a difficulty that addition of a molten resin database becomes difficult. In addition, in the conventional injection molding machine utilization measurement system, molding of the product related to the weight measurement, using the attached mold from the relationship of the measuring device, that is, without using the production target mold of the injection molding machine, Since the measurement is performed, the specific function based on the measurement data and the corrected holding pressure do not match the actual production operation using the production target mold. This means that the molds to be produced have unique characteristics corresponding to the shape of the molded product, the shape of the runner, etc.
There is a disadvantage that the quality of the molded product is reduced.

[0008] This difficulty is further promoted when the mold is slightly opened during molding because the mold clamping force required by the mold is limited. The correction for the inconsistent specific function and the corrected holding pressure requires complicated processing and cannot be expected to be accurate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a molten resin characteristic function to be applied to the holding pressure of a molten resin in a relatively simple manner, and to accurately set the characteristic function and a corrected holding pressure corresponding thereto. An object of the present invention is to provide a holding pressure control method for a molding machine.

[0010]

In order to achieve the above object, a method for controlling a pressure of an injection molding machine according to the present invention comprises the steps of: The temperature of the molten resin and / or its equivalent value, the holding pressure, and the weight of the molded product by the mold to be produced under these conditions in the preliminary test operation of the injection molding machine. By repeatedly measuring the specific volume ratio characteristic function consisting of the temperature, holding pressure and specific volume ratio of the molten resin from these measurement data, a correction for the production of non-defective products at abnormal temperatures with respect to this specific volume ratio characteristic function Calculation and setting of pressure and actual production operation of injection molding machine
Sometimes holding pressure control method of the holding pressure the specific volume ratio characteristic function and the correction out morphism that controls via the holding pressure molding machine
In the above, the temperature equivalent value of the molten resin is determined in the injection molding machine.
Between the two points of the nozzle part of the molten resin flowing through the nozzle part
It is characterized by a pressure difference between the two.

[0011] Multiple this case, the temperature and / or equivalent values thereof for molten resin (the corresponding pressure difference), as measured by dividing the until recombinant holding pressure from the filling start to the injection molding machine of the molten resin Can be set to the average of the measured values.

Further, the weight of the molded product can be set to the average value of the measured values of a plurality of products molded respectively for each condition of one temperature and / or its equivalent value and holding pressure of the molten resin. .

Further, the molten resin specific volume ratio characteristic function is obtained by calculating and setting the thermal expansion coefficient at an equal pressure temperature rise of the molten resin and the compression ratio at isothermal pressurization from the temperature, holding pressure and specific volume ratio of the molten resin. The ratio of the specific volume at an arbitrary temperature and pressure to the specific volume at a specific reference temperature and pressure can be displayed from a plurality of constant pressure specific volume ratio linear groups using pressure as a parameter.

Further, the corrected coercive pressure for the specific volume ratio characteristic function is obtained by measuring the temperature and pressure of the molten resin during the production of non-defective products, and measuring the isobar specific volume ratio straight line with respect to the preservation pressure during non-defective product production in the linear group of constant pressure specific volume ratios. By calculating and setting the specific volume ratio, it is possible to set the holding pressure to be equal to the specific volume ratio at the time of producing the non-defective product.

[0015]

In the present invention, the molten resin characteristic function applied to the holding pressure of the molten resin is such that the molten resin data is composed of temperature, pressure and specific volume ratio. In other words,
The specific volume in the conventional control method of this type is changed to a specific volume ratio (specific volume change rate). Therefore, it is clear that the molten resin characteristic function of the present invention can be simply (primarily) constructed by changing the control line on the control diagram from the conventional specific volume hyperbola to the specific volume ratio straight line. is there.
Further, in the present invention, the molten resin characteristic function and the corrected holding pressure are configured so that product molding relating to weight measurement related to the setting is performed using the production target mold itself of the injection molding machine. Therefore, the molten resin characteristic function and the corrected holding pressure of the present invention can be accurately adapted even in the actual production operation, even if the production target mold is slightly opened during molding. it is obvious.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a method for controlling a dwell pressure of an injection molding machine according to the present invention.

FIG. 1 is a system block diagram showing one embodiment of a method for controlling the pressure retention of an injection molding machine according to the present invention. The pressure-holding control method of the present invention is basically a pressure-holding control method of the injection molding machine 14 that pressurizes the molten resin 12 filled in the cavity 10a of the mold 10 and replenishes the shrinkage accompanying the cooling and solidification. Consists of Then, in the preliminary test operation of the injection molding machine 14, the temperature T of the molten resin 12 and / or its equivalent value [in this embodiment, the pressure of the molten resin 12 flowing through the nozzle portion 16 between the two points of this nozzle portion] Difference Δ
P (see FIG. 2)], the holding pressure P, and the weight W of the molded product 18 by the production target mold 10 under these conditions.
With the respective detectors 2 for weight, temperature, pressure and position.
The measurement is repeatedly performed using 0, 22, 24, and 26. As a result, first, from these measurement data, a specific volume ratio characteristic function including the temperature T, the holding pressure P, and the specific volume ratio VC of the molten resin 12 and a non-defective product at an abnormal temperature when the specific volume ratio characteristic function is abnormal. The corrected holding pressure is calculated and set by the calculation processing unit 28. Next, in the actual production operation of the injection molding machine 14, the holding pressure P is passed through the control unit 30, the holding pressure control means (electromagnetic pressure valve) 32, and the screw device 34 via the specific volume ratio characteristic function and the corrected holding pressure. It is configured to be controlled.

Reference numeral 36 in the figure denotes a storage unit for storing non-defective molding conditions such as a molten resin characteristic function and / or a corrected holding pressure, and reference numeral 38 denotes an arithmetic processing of data in the storage unit 36 and the like. Setters to set for section 28 are shown, and reference numerals 40 and 42 indicate a screw rotation motor and a hydraulic pump, respectively.

As described above, according to the present invention, the pressure of the molten resin in the injection molding machine is controlled through the specific volume ratio characteristic function including the temperature T, the pressure P, and the specific volume ratio VC. However, the specific volume ratio characteristic function of the present invention has already been understood from the above description. If the pressure of the molten resin is constant, the specific volume is proportional to the temperature. That is, as is well known, the characteristics of the molten resin utilize the fact that it is represented by the so-called Spencer-Gilmore equation of state. Therefore,
The Spencer-Gillmore equation of state and the characteristic function of the present invention derived from the equation will be described.

First, the Spencer-Gillmore equation of state is:

(Equation 1)

## EQU2 ## Incidentally, as described above, the above equation (1) controls the pressure (holding pressure) P so as to keep the specific volume V constant in accordance with the fluctuation of the temperature T, that is, so-called P
-A basic equation applied to VT control.

Next, the specific volume ratio characteristic function of the present invention will be described. This characteristic function has a resin characteristic consisting of a temperature T, a pressure P and a specific volume ratio VC, as described above. And this resin characteristic is the mold 1 to be produced.
It is obtained by measuring the weight W of the molded product 18 by 0. That is, assuming that the capacity of the cavity 12a is Q, the specific volume is represented by Q / W. By substituting this into the above equation (1), the following equation is obtained.

(Equation 2)

Is derived and further rearranged as 1 / W = M, the following equation is obtained.

(Equation 3)

Is derived. That is, the equation (3) is
This is a basic equation defining the specific volume ratio characteristic function of the present invention, and the above equation (3) is a linear function in which the reciprocal M of the weight W is proportional to the temperature T and inversely proportional to the pressure P. Accordingly, the control line on the control diagram, that is, the reciprocal M-temperature T diagram of the weight W with the pressure P as a parameter indicates that the curve is set to a straight line. Incidentally, the control line on the PVT control diagram is hyperbolic, which is as described above. Therefore, assuming that the pressure P is constant Pc in the equation (3), the following equation is obtained.

(Equation 4)

Is derived. This is expressed as a group of a plurality of straight lines with the pressure P as a parameter,

(Equation 5)

Which can also be described as a value at a certain reference temperature Tc and pressure Pc:

(Equation 6)

As a ratio to the following equation,

(Equation 7)

Can be described as follows. That is, the above equation (5) is a characteristic function representing the constant pressure specific volume ratio straight line of the present invention. And by using this line group,
Temperature fluctuation can be corrected by the holding pressure.

Here, the characteristic function equation (5) is obtained by converting the resin characteristic from its temperature T to its equivalent value, that is, the pressure difference ΔP
(See FIG. 2). That is, referring to FIG. 2, the relationship between the viscosity η of the molten resin 12 and the pressure difference ΔP is as follows in the case of an isothermal and Newtonian fluid.

(Equation 8)

## EQU2 ## Here, assuming that the flow rate Q is constant and K = 8LQ / (πR ⁴ ), the following equation is obtained.

(Equation 9)

Is described. On the other hand, the relationship between the viscosity η of the viscous non-Newtonian fluid and the temperature T is expressed by the following equation.

(Equation 10)

## EQU2 ## Assuming that the flow rate Q is constant, the shear rate γ is also constant.

Therefore, from the above equations (6) and (7), the following equation is obtained.

[Equation 11]

Is derived. Then, in this case, ΔP and T
When the absolute value of C * T is smaller than 1 within a minute range in which a non-defective product is produced, the variation range of the temperature T is regarded as a linear expression. ) Is obtained by replacing the temperature T with a pressure difference ΔP.

(Equation 12)

Can be converted to That is, the present invention uses the functional expression (8) related to the pressure difference ΔP, in other words, even if the temperature variation is detected as the pressure difference variation in the nozzle unit 16, the functional formula (5) related to the temperature T is obtained. As in the case of using, it is possible to achieve the dwell control.

In the present invention, as described above, various kinds of resin characteristic data are measured or calculated. Therefore, in the following, regarding the following items, measurement of the average weight of the molded product, setting of the specific volume ratio, creation of an equal pressure specific volume ratio straight line (characteristic function), creation of an equal pressure specific volume ratio straight line during non-defective molding The description will be made in accordance with the items of setting of the holding pressure for the temperature fluctuation. In this description, regarding the temperature T of the molten resin and the equivalent value (pressure difference) ΔP, the temperature T will be mainly described and the pressure difference ΔP will be described subordinately.

First, in the measurement of the average weight of a molded product, standard molding conditions (pressure P ₀ and reference temperature T ₀ ) for setting a good product are set, and an average weight W ₀₀ of a plurality of molded products is obtained. Thereafter, the reference molding conditions (P ₀ , T ₀ )
Is changed, and the respective molding conditions (P ₁ , T ₁ ), (P ₁ ,
T ₂ )... (P ₂ , T ₁ ), (P ₂ , T ₂ ), the corresponding average weights, W ₁₁ , W ₁₂ .
_21, seeking a W _22.

In this case, the standard molding conditions can be arbitrarily selected, and the change from the standard molding conditions is performed within a range in which a good product is molded.

The temperature T is an average value of n measured values obtained by dividing the period from the start of filling of the molten resin into the injection molding machine to the switching of the holding pressure, for example. Note that the temperature T
Is replaced with the pressure difference ΔP, the temperature and its sign T in the above description are replaced with the pressure difference and its sign ΔP. In this case, each of the pressure differences ΔP is measured corresponding to each of the temperatures T.

Next, in setting the specific volume ratio, as described above, assuming that the capacity of the cavity 12a is Q, the specific volume is represented by Q / W. The volume is V ₀₀ = Q / W ₀₀ , V ₁₁ = Q
/ W ₁₁ , V ₁₂ = Q / W ₁₂ ,.
The specific volume ratio VC, that is, the ratio of the specific volume under each molding condition to the reference specific volume is expressed as VC ₁₁ = V ₁₁ / V ₀₀ , VC ₁₂ = V ₁₂ /
V ₀₀ ,... (See Table 1). In this case, if the temperature T is replaced with the pressure difference ΔP,
The temperature and its sign T are replaced by the pressure difference and its sign ΔP, and Table 1 is changed to Table 2.

[0041]

[Table 1]

[0042]

[Table 2]

Next, in preparing an isobar specific volume ratio line, the thermal expansion coefficient (isothermal thermal expansion coefficient) of the molten resin when the isobar temperature rises and the compressibility (isothermal compressibility) under isothermal pressing are measured and calculated. Then, from the measurement calculation data, the ratio of the specific volume at the given temperature and pressure to the specific volume at the reference temperature and pressure is created as a group of a plurality of straight lines (ie, equal pressure specific volume ratio straight lines) using pressure as a parameter. I do. By the way, as described above, the straight line group (characteristic function) is approximately equal to the linear expression (5).

(Equation 13)

In FIG. 3, for example, a point group PO _j1 (T ₁ , VC _{Pj, T1} ), PO _j2 (T ₂ , V
C _{Pj, T 2} ),... PO _jm (T _m , VC _{Pj, Tm} ), using the least squares method, the linear equation VC (T) _{P = P1} = a
The coefficients a _Pj and b _{Pj of Pj} + _bPj · T, that is,

[Equation 14]

By obtaining the above equation, the straight line group (equal pressure specific volume ratio straight line) can be created.

When the temperature T is replaced with the pressure difference ΔP, the temperature and its sign T are equal to the pressure difference and its sign ΔP.
The expression (5) is changed to the expression (8) while being replaced with P.

That is, in the above description, approximately the following equation (8)

(Equation 15)

In FIG. 3, for example, a point group P _Oj1 (ΔP ₁ , V
C _{Pj, ΔP1} ), P _Oj2 (ΔP ₂ , VC _{Pj, ΔP2} ) _{,.
From Ojm} (ΔP _m , VC _{Pj, ΔPm} ), using the least squares method, a linear equation VC (ΔP) _{P = P1} = a _Pj + b _Pj.
The coefficients a _Pj and b _Pj in ΔP are expressed by the following equations.

(Equation 16)

By obtaining the above, the straight line group (equal pressure specific volume ratio straight line) can be prepared and replaced.

Next, in preparing the equal pressure specific volume ratio straight line at the time of molding a non-defective product, the coefficients as and b of the linear equation at the time of non-defective product molding (pressure Ps, temperature Ts) are obtained from the above-mentioned group of constant pressure specific volume ratio straight lines.
s is obtained from a known coefficient by proportional distribution (see FIG. 4). That is, the known pressures before and after the pressure Ps to be obtained are _Pj , _{Pj + 1} ; where _Pj ≦ Ps ≦ _{Pj + 1} , and the coefficient α is α = (Ps− _Pj ) / (P _{j + 1} -P _j )
In other words, the constant pressure ratio volume ratio line to the holding pressure at the time of molding a good product is given by the following equation.

[Equation 17]

Thus, from these coefficients a _Ps and b _Ps ,
The specific volume ratio when P = Ps and T = Ts is expressed by the following equation.

(Equation 18)

Is as follows. That is, an equal pressure specific volume ratio straight line at the time of non-defective molding is created. When the temperature T is replaced with the pressure difference ΔP, it is obvious that the temperature and its sign T are replaced by the pressure difference and its sign ΔP.

Finally, the setting of the correction holding pressure for temperature fluctuation, that is, the temperature is changed from the reference temperature Ts to the non-reference temperature Ts'
In the case where the pressure varies, the correction for changing the holding pressure from the reference pressure Ps to the correction pressure Ps' so as to maintain the specific volume ratio constant is performed as follows. That is, pressure (holding pressure)
Is Ps ', the specific volume ratio is a coefficient a _Ps' ,
If b _{Ps ′} is set, the following equation is obtained as in the case of equation (9).

[Equation 19]

Therefore, the specific volume ratio when the temperature is Ts' is expressed by the following equation.

(Equation 20)

Is represented by Then, both states (Ps, T
s) and (Ps ', Ts'), to make the specific volume ratio constant,

(Equation 21)

It suffices that the following condition be satisfied.
0) and (11), the following equation

(Equation 22)

Is derived. That is, by solving the equation (12), the necessary coefficients a _{Ps ′} and b _{Ps ′} can be set. In this case, an iterative calculation is performed because an analytical method cannot be applied to the solution. That is, the initial value of the specific volume ratio is obtained by a certain procedure, and the initial value and the target specific volume ratio V when the pressure and the temperature are Ps and Ts are obtained.
Iterative calculation is performed so that the difference between C (Ts) _{P = Ps} is within an allowable value. For example, referring to FIG. 5, the specific volume ratio at the temperature Ts ′ is VC (Ts) _{P = Ps} from the constant pressure specific volume ratio straight line at the reference pressure Ps and another constant pressure specific volume ratio straight line at the known pressure Pk. Pressure s' equal to
Ask for. Therefore, in order to select an equal pressure specific volume ratio straight line at the known pressure Pk, Pk is a pressure near Ps, and when Ts '> Ts, Pk> Ps When Ts'<Ts, the temperature and specific volume of Pk <Ps are satisfied. Assume that the relational expression of the ratio is a known pressure (Pj or Pj + 1). In this way, Ps' to be obtained is P
Since the pressure is between s and Pk, the target pressure can be obtained while narrowing the range by ２. That is, (1) The initial value of the correction pressure (holding pressure) is obtained.

It is assumed that ΔPi = １ ／ · (Pk−Ps).

(2) i = Ps + ΔPi (3) The coefficients A _Pi and b _Pi are obtained by the proportional distribution method, and the pressure Pi
The specific volume ratio VC (Ts ') _{P = Pi} at the temperature Ts' is calculated.

(4) This specific volume ratio VC (Ts') _{P = Pi}
The specific volume ratio VC (Ts) at the time of the pressure Ps and the temperature Ts is compared with _{P = Ps,} and if the difference between the two is within an allowable value, (5)
To VC (Ts') _{P = Pi} <VC (Ts) If _{P = Ps,} then ΔPi
= 1/2 · ΔPi, Pi = Pi−ΔPi VC (Ts ′) _{P = Pi} > VC (Ts) If _{P = Ps,} then ΔPi
= 1/2 · ΔPi, Pi = Pi + ΔPi (3), and thereby (5) Pi can be set as the corrected holding pressure.

When the temperature T is replaced with the pressure difference ΔP, that is, in the setting of the correction holding pressure for the pressure difference fluctuation accompanying the resin temperature fluctuation, the pressure difference fluctuates from the reference pressure difference ΔP to the non-reference pressure difference ΔP ′. In this case, the holding pressure is changed from the reference pressure Ps to the correction pressure P to maintain the specific volume ratio constant.
When changing to s', it is clear that, as before, the temperature and its sign T are replaced by a pressure difference and its sign ΔP.

As described above, in the present invention, the molten resin characteristic function applied to the holding pressure of the molten resin is such that the molten resin data is composed of temperature, pressure and specific volume ratio. In other words, the specific volume in the conventional control method of this type is changed to a specific volume ratio (a change ratio of the specific volume). Therefore, it is apparent that the molten resin characteristic function of the present invention is simply (primarily) configured by changing the control line on the control diagram from the conventional specific volume hyperbola to the specific volume ratio straight line. It is. Further, in the present invention, the molten resin characteristic function and the corrected holding pressure are configured so that product molding relating to weight measurement related to the setting is performed using the production target mold itself of the injection molding machine. Therefore, the molten resin characteristic function and the corrected holding pressure of the present invention are:
In the actual production operation, it is apparent that even if the mold to be produced slightly opens during molding, it can be accurately applied.

[0063]

As described above, the method for controlling the dwelling pressure of an injection molding machine according to the present invention is directed to an injection molding machine for pressurizing a molten resin filled in a mold and supplementing shrinkage due to cooling and solidification thereof. It consists of a holding pressure control method, by repeatedly measuring the temperature of the molten resin and / or its equivalent value, the holding pressure, and the weight of the molded product by the target mold under these conditions in the preliminary test operation of the injection molding machine, From these measurement data, the specific volume ratio characteristic function consisting of the temperature of the molten resin, the holding pressure and the specific volume ratio, and the corrected holding pressure for non-defective product production at abnormal temperature with respect to this specific volume ratio characteristic function are calculated and set, actual production operation sometimes Oite the holding pressure to holding pressure control method of the specific volume ratio characteristic function and the correction holding pressure via a control <br/> to that elevation molding machine of the injection molding machine, the molten resin
The temperature equivalent to the temperature of the melt flowing through the nozzle in the injection molding machine
The pressure difference between the two points of the nozzle portion of the molten resin
And is characterized by the following.

In other words, in the present invention, the molten resin characteristic function applied to the holding pressure of the molten resin is such that the molten resin data is composed of temperature, pressure and specific volume ratio. Moreover, the specific volume in the conventional control method of this type is changed to a specific volume ratio (specific volume change rate).
Therefore, the molten resin characteristic function of the present invention can be simply (primarily) constructed by changing the control line on the control diagram from the conventional specific volume hyperbola to the specific volume ratio straight line. it is obvious. Further, in the present invention, the molten resin characteristic function and the corrected holding pressure are configured so that product molding relating to weight measurement related to the setting is performed using the production target mold itself of the injection molding machine. Therefore, it is clear that the molten resin characteristic function and the corrected coercive pressure of the present invention can be accurately applied in actual production operation even if the production target mold has a minute mold opening during molding.

[Brief description of the drawings]

FIG. 1 is a system block diagram showing an embodiment of a pressure holding control method for an injection molding machine according to the present invention.

FIG. 2 is an enlarged view of a main part showing a nozzle part of the injection molding machine shown in FIG.

FIG. 3 is a graph showing a characteristic of a straight line of an equal pressure specific volume ratio.

FIG. 4 is a graph showing characteristics of a coefficient of a constant-pressure specific volume ratio straight line (primary expression) and a target specific volume ratio during non-defective molding.

FIG. 5 is a flowchart illustrating a procedure for calculating a correction holding pressure for an abnormal cooling temperature (temperature fluctuation).

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 mold 10 a cavity 12 molten resin 14 injection molding machine 16 nozzle part 18 molded product 20 weight detector 22 temperature detector 24 pressure (difference) detector 26 position detector 28 arithmetic processing unit 30 control unit 32 holding pressure control means 34 Screw device 36 Data storage unit 38 Setting unit 40 Screw rotation motor 42 Hydraulic pump

Continuation of the front page (56) References JP-A-4-148911 (JP, A) JP-A-4-67930 (JP, A) JP-A-3-254922 (JP, A) JP-A-3-292121 (JP) , A) Hikaru Hei 3-52122 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00 B29C 45/17 B29C 45/46-45/57 B29C 45/76 -45/84

Claims (5)

(57) [Claims] 1. A pressure control method for an injection molding machine for replenishing shrinkage accompanying cooling and solidification of a molten resin filled in a mold by pressurizing the molten resin. / Or its equivalent value, holding pressure and the weight of the molded product by the mold to be produced under these conditions are repeatedly measured, and from these measurement data, the specific volume consisting of the temperature, holding pressure and specific volume ratio of the molten resin is obtained. The specific characteristic function and the corrected holding pressure for non-defective product production at abnormal temperature with respect to the specific volume ratio characteristic function are calculated and set, and during the actual production operation of the injection molding machine, the holding pressure is set to the specific volume ratio characteristic function and the Oite the holding pressure control method for a molding machine out morphism that control through a correction holding pressure, temperature equivalent of the molten resin
The value is before the molten resin flowing through the nozzle in the injection molding machine.
Characterized by a pressure difference between two points of the nozzle portion.
Pressure control method of injection molding machine. 2. The method according to claim 1, wherein the temperature of the molten resin and / or its equivalent value is an average value of a plurality of measured values divided and measured from the start of filling of the molten resin into the injection molding machine to the switching of the holding pressure. Item 3. A method for controlling a dwell pressure of an injection molding machine according to Item 1. 3. The injection according to claim 1, wherein the weight of the molded product is an average value of measured values of a plurality of products molded respectively for each condition of the temperature and / or its equivalent value and the holding pressure of the molten resin. Pressure control method of molding machine. 4. The molten resin specific volume ratio characteristic function is obtained by calculating and setting a thermal expansion coefficient at an equal pressure temperature rise of the molten resin and a compression ratio at isothermal pressing from the temperature, holding pressure and specific volume ratio of the molten resin. 2. The injection molding machine according to claim 1, wherein the ratio of the specific volume at a given temperature and pressure to the specific volume at a specific reference temperature and pressure is displayed from a plurality of constant pressure specific volume ratio linear groups using pressure as a parameter. Holding pressure control method. 5. The corrected coercive pressure for the specific volume ratio characteristic function is obtained by measuring the temperature and pressure of the molten resin during the production of non-defective products, and calculating the constant pressure specific volume ratio straight line and the preservation pressure during non-defective product production in the group of constant pressure specific volume ratio straight lines. 5. The holding pressure control method for an injection molding machine according to claim 4 , wherein the holding pressure is set to be equal to the specific volume ratio at the time of producing non-defective products by calculating and setting the specific volume ratio.