JP2003320577A - Numeral value analyzing method and device for blow- molding material behavior - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a numeral value analyzing method and a device by which a parison thickness by drawing down after a parison extrusion can be estimated by a simple method, and a blow-molding material behavior in a blow-molding process can be accurately estimated. <P>SOLUTION: The behavior of the blow-molding material in the blow-molding process is simulated by a computer for this numeral value-analyzing method. The numeral value analyzing method for the blow-molding material behavior includes a drawing down curve-inputting process wherein drawing down curve data is input, a material physical property parameter initial value setting process wherein an initial value of a specified material physical property parameter used for the analysis is set, an extrusion analysis performing process wherein the extrusion analysis of the blow-molding material is performed by the set material physical property parameter, a material physical property parameter correcting process wherein the material physical property parameter is corrected, and an extrusion analysis-performing process wherein the extrusion analysis is performed again by the corrected material physical property parameter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical analysis method, device and storage medium for simulating the behavior of blow molding material in a blow molding process by a computer.

[0002]

2. Description of the Related Art Simulation of a molding process of a blow molding material in a blow molding method contributes to high quality, efficiency, and cost reduction in the development of blow molded products. The main purpose of blow molding simulation is to predict the uneven thickness condition of the molded product that occurs during molding, and based on this result, set the molding conditions and change the mold design and product design to optimize the wall thickness distribution. It is to carry out. Therefore, it is important to accurately predict the uneven thickness state of the molded product by simulation. The blow molding method is a parison extrusion process in which a semi-molten resin material called a parison is extruded into a cylindrical shape from a die, and the extruded parison is sandwiched between molds, and then air is blown into the parison to expand it in the mold. It consists of a mold clamping and air blowing process for shaping into a cavity shape. The uneven thickness of the molded product occurs remarkably mainly in the air blowing step. A method of simulating the mold clamping / air blowing process is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-258128 by the present applicant.

In the simulation of the mold clamping / air blowing process, it is necessary to input the parison shape and the wall thickness after extrusion as initial data in the simulation. As a method of measuring the wall thickness distribution of the parison after extrusion, use a measuring device such as a laser-type non-contact wall thickness measuring machine, or after extruding, quickly cool the parison to solidify it and cut it by hand. Although there are methods such as measurement, all of them take time and effort, and therefore, in many cases, rough data such as a cylinder having a uniform wall thickness is used as the parison after extrusion used for the simulation. However, when the parison is extruded, it is widely known that the parison becomes thin around the center due to a drooping phenomenon due to its own weight called drawdown. The degree is
It depends on the material and molding conditions. Since this thinning has a great influence on the thickness of the final molded product, drawdown is a factor that cannot be ignored in blow molding. Therefore, also in this parison extrusion step, a parison wall thickness prediction method by simulation in consideration of drawdown is disclosed in Japanese Patent Laid-Open No. 2001-322160 as well as the air blowing step. However, semi-melting at the boundary between fluid and solid is disclosed. The modeling of the material when handling the material in the state is complicated, a large-scale simulation that requires calculation time is required, and it is difficult to collect the material property data used for the simulation.

[0004]

In view of these circumstances, the present invention predicts the change in the parison thickness due to drawdown after extrusion of the parison by a simple method and accurately predicts the behavior of the blow molding material in the blow molding process. It is an object of the present invention to provide a numerical analysis method and device capable of performing the numerical analysis.

[0005]

In order to achieve the above object, according to the present invention, there is provided a numerical analysis method for simulating the behavior of a blow molding material in a blow molding process by a computer. Drawdown curve input process to be input, material property parameter initial value setting process to set initial values of specific material property parameters used for analysis, and extrusion to perform blow molding material extrusion analysis by the set material property parameters Numerical value of blow molding material behavior, characterized by including an analysis execution step, a material physical property parameter correction step for correcting the material physical property parameter, and an extrusion analysis execution step for executing extrusion analysis again with the corrected material physical property parameter. An analysis method is provided.

A preferred embodiment of the present invention is the method for numerical analysis of blow molding material behavior, wherein the blow molding material is a parison extruded in a cylindrical shape from a blow molding machine.

A preferred aspect of the present invention is a numerical analysis method for blow molding material behavior, wherein the specific material physical property parameter is a viscosity coefficient of the material.

In a preferred embodiment of the present invention, in the drawdown curve input step, the drawdown curve data is inputted as a function of extrusion time and extrusion length, and numerical analysis of the behavior of the blow molding material is carried out. Method.

A preferred embodiment of the present invention is a numerical analysis method of blow molding material behavior, wherein the drawdown curve data is measured in advance by a drawdown measuring device.

A preferred embodiment of the present invention is characterized in that, in the extrusion analysis execution step, the blow molding material is modeled as an assembly in which microelements composed of springs and dashpots are connected in series. This is a numerical analysis method for the behavior of blow molding materials.

Further, according to the present invention, there is provided an analysis device for simulating the behavior of a blow molding material in a blow molding process by a computer, the analysis condition setting means for setting analysis condition data used for the analysis, and the analysis condition setting means. An initial parameter setting means for setting an initial value of a specific material physical property parameter to be used, an analysis execution means for executing extrusion analysis of a blow molding material, and a material physical property parameter correction means for correcting the material physical property parameter. A numerical analysis device for the behavior of blow molding material is provided.

A preferred embodiment of the present invention is a numerical analysis device for behavior of blow molding material, wherein the blow molding material is a parison extruded in a cylindrical shape from a blow molding machine.

A preferred embodiment of the present invention is a numerical analysis apparatus for blow molding material behavior, wherein the specific material physical property parameter is a viscosity coefficient of the material.

A preferred embodiment of the present invention is a numerical analysis apparatus for blow molding material behavior, wherein the extrusion length measurement data of the blow molding material is calculated as a function of extrusion time.

Further, a preferred embodiment of the present invention is a numerical analysis apparatus for behavior of blow molding material, characterized in that the extrusion length measurement data of the blow molding material is previously measured by a drawdown measuring apparatus. is there.

[0016] In a preferred aspect of the present invention, in the analysis execution means, the blow molding material is modeled as an assembly in which microelements including a spring and a dashpot are connected in series. This is a numerical analysis device for molding material behavior.

Further, according to the present invention, a computer program for simulating the behavior of the blow molding material in the blow molding process by a computer is used for the draw down curve input step for inputting the draw down curve data and the analysis. The initial step of setting the initial value of the physical property parameter of the specific material to be set, the extrusion analysis executing step of executing the extrusion analysis of the blow molding material by the set physical parameter of the material, and the correction of the physical parameter of the material There is provided a computer-executable program for causing a computer to execute each step including a material physical property parameter correction step and an extrusion analysis step of executing extrusion analysis again with the corrected material physical property parameter.

According to the present invention, there is also provided a computer-readable storage medium storing the above program.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below. First, an extrusion analysis method by numerically modeling a blow molding material (hereinafter referred to as a parison) extruded from a die as an aggregate of elements defined by a combination of a spring and a dashpot will be described.

FIG. 1 is a flow chart showing a schematic procedure of an embodiment of the present invention. The numerical analysis method according to this embodiment includes a drawdown curve input step (step 1), an analysis data input step (step 2), a material physical parameter initial value setting step (step 3), an extrusion analysis execution step (step 4), and a material. It comprises a physical property parameter correction step (step 5) and an analysis result output step (step 6). The material physical property parameter correction step and the extrusion analysis execution step are repeatedly executed until the parameter correction is completed.

Here, the drawdown curve is a plot of the relationship between the extrusion time and the length of the extruded parison as shown in FIG. 2, and is widely known as an index showing the drawdown characteristic of a material. Has been. For example, comparing the materials A and B extruded at the same extrusion speed in the figure, the material B having a longer parison length with respect to the extrusion time is a material that is easier to draw down than the material A. Can be said.

FIG. 4 is a block diagram of the analysis apparatus used in this embodiment, which comprises analysis condition setting means 101, initial parameter setting means 102, analysis executing means 103, parameter correcting means 104, and analysis result output means 105. An arithmetic unit 100 for performing an analytical arithmetic process, a data storage unit 110 including a memory and a hard disk for storing analysis data and software, an analysis condition input unit 120 including a keyboard and a mouse, a display, a printer, and a stereolithography device. An output device 130 and the like are provided. Each of these means is a CPU of an arithmetic unit (computer)
It is also realized in the form of functions and subroutines on the hardware constructed by the memory.

Next, the parison extruded from the die is
The extrusion analysis method numerically modeled as a set of elements defined by the combination of springs and dashpots will be described.

FIG. 5 shows minute elements used for the main extrusion analysis. This element is called the Maxwell model, which is defined as a one-dimensional element in which a spring, dashpot, and mass are connected in series, and is widely used as a simple method for modeling materials with viscoelastic properties. ing. In the main extrusion analysis by connecting the elements in series, as shown in FIG.
The parison is one-dimensionally modeled as follows. The analysis flow will be described below with reference to FIG. 7. First, input the input conditions required for analysis. Here, the required material characteristic parameters are the density ρ, elastic modulus E and viscosity coefficient μ of the material. Here, in the Maxwell model, the density ρ is a mass, the elastic modulus E is a spring characteristic, and the viscosity coefficient μ is a parameter that determines a dashpot characteristic. Next, the extrusion speed v from the die is input as the molding condition, and the analysis time step Δt is input as the analysis control parameter. Here, the time step Δt is set as the time for which one Maxwell element is extruded from the die. If the element first extruded from the die is E1, its length S0 is the product of the extrusion speed v and the time step Δt (v · Δt). At this time, the element E1 is replaced by the element E1
It is assumed that the load F calculated by the equation (1) is applied due to its own weight. Here, g is the gravitational acceleration.

Equation (1) F = S0 × ρ × g Under this load condition, the longitudinal strain ε1 of the element E1 after Δt seconds is calculated based on the constitutive equation of the Maxwell model.
(Z), strains ε1 (x) and ε1 (y) in the cross-sectional direction are calculated. At this time, in the cylindrical parison, ε1 (z) calculated in the Maxwell model is the extrusion direction, ε1 (z)
(X) and ε1 (y) correspond to the strain of the parison thickness and the parison diameter.

Then, after the next Δt seconds, ie (2 × Δt) seconds after the start of extrusion, an element E2 is produced following E1, which is extruded. In the parison model, two elements E1 and E2 are connected in series. At this time, the load F calculated previously is continuously added to E1, but E2
In addition to the self-weight of E2 itself, the weight of E1 extruded earlier is added to the load, so that the load value is twice the weight of E1, that is, 2 × F.

Under this load condition, as in the previous step, the strain ε1 (z) in the longitudinal direction of the element E1 after Δt seconds, the strain ε1 (x), ε1 (y) in the cross-sectional direction, and the strain E1 (y) in the longitudinal direction of the element E2 were measured. Strain ε2 (z), cross-sectional strain ε2 (x), ε2
Calculate (y).

Thereafter, the elements are sequentially extruded as E3, E4 and E5. The load applied to each element is 3 × F for E3, 4 × F for E4 and 5 × F for E5. And increase sequentially. By repeating the above operation, the analytical model is extended in the longitudinal direction by extrusion and extension by its own weight.

FIG. 8 shows the correspondence relationship between the Maxwell model and the actual parison, and the method of converting the analysis result by the Maxwell model into the parison shape data will be described below.

First, the length S (Ei) of the i-th extruded element Ei can be derived by the equation (2).

Equation (2) Si = S0 × exp ((ε _i (z)) Further, the length L of the parison after N × Δt seconds is calculated by the equation (2) of N elements. Since it is the sum of the respective element lengths, it can be calculated by Expression (3).

Equation (3) L = ΣS0 × exp ((ε _i (z)) where ε _i (z) is the strain in the extrusion direction of the element Ei.

If the initial wall thickness of the element Ei is T0 and the diameter of the element Ei is D0, the wall thickness Ti and the diameter Di can be calculated from the equation (4) from the strain in the cross-sectional direction of each element.

Expression (4) Ti = T0 × exp ((ε _i (x)) Di = D 0 × exp ((ε _i (x)) ε _i (x) = ε _i (y) The above operation is preset. By repeating until the extrusion time is reached, it is possible to predict the change in the parison shape after extrusion.

The material physical property parameters required in the above analysis method are density ρ, elastic modulus E, and viscosity coefficient μ. Of these, the density is generally known as a catalog value for each material, so if this is used, Good. Also, the elastic modulus is
In this analysis, a fixed value does not have a large effect on the result because it does not have a large effect on the drawdown.
On the other hand, the viscosity coefficient μ of the parison is an important factor that determines the drawdown characteristics, but it is difficult to measure in a semi-molten state with a general measuring device. Therefore, in the present invention, it is preferable to analyze by the method of the present invention using the viscosity coefficient as a specific material physical property parameter. By correcting the viscosity coefficient so that the difference between the drawdown curve obtained by analysis and the actually measured drawdown curve becomes small, the accuracy of analysis improves, and it is possible to accurately predict changes in the parison thickness and shape after extrusion. Is possible.

In the following examples, for the purpose of explaining the basic method for carrying out the present invention, materials whose drawdown characteristics are shown by a drawdown curve as shown in FIG. 9 will be described.

First, in step 1, the analysis condition input device 12
With 0, the measured data of the drawdown curve is input.
Here, the drawdown curve can be measured by measuring the tip position of the extruded parison with respect to the extrusion time, and can be easily measured by using a commercially available drawdown measuring instrument equipped with a photoelectric tube and a counter. .
Here, the input data may be numerical data of the extrusion time and the parison length measured by the drawdown measuring device, or may be in the form of an approximate expression obtained by approximating the measured data with a polynomial.

Next, in step 2, analysis conditions are input from the analysis condition input device 120. The analysis conditions input here are the density and the elastic modulus in the Maxwell model as the material physical property data. The density uses a catalog value of the material, and the elastic modulus uses a fixed value. Further, as the extrusion conditions, the extrusion speed and the extrusion thickness are input. The extrusion speed input here may be calculated from the extrusion amount set in the molding machine, but as shown in FIG. 9, it is preferable to use the value calculated from the gradient immediately after extrusion of the drawdown curve. Further, as the extruded thickness, the extruded thickness may be the thickness immediately after it comes out of the parison die. These analysis condition inputs may be input by selecting them from electronic information that has been input to the analysis condition input device 120 in advance and stored in the data storage device 110 as a database. The input analysis condition data is held in the memory and, if necessary, saved in the data storage device 110 by the analysis condition setting means 101.

Next, in step 3, the parameter initial value setting means 102 sets a temporary initial viscosity coefficient. The initial viscosity coefficient input in this step is 100 MPa /
A value selected from the range of s to 500 MPa / s is preferable.

Next, in step 4, the drawdown analysis is executed by the analysis executing means 103 based on the set initial viscosity coefficient and other analysis condition data. The drawdown analysis is performed until the preset extrusion time is reached. In the normal case, the period from the start of extrusion to the end of extrusion is divided into a plurality of steps for calculation. As a result, in each calculation step, an analysis result of the progress state of the parison extrusion, the strain amount in each Maxwell element, the extension amount, etc. is obtained, and is recorded in the memory of the arithmetic device 100 or the data storage device 110 as the analysis result.

Next, in step 5, based on this result,
The parameter correcting means 104 corrects the viscosity coefficient. In this step, first, an evaluation parameter is calculated by digitizing the comparison between the drawdown curve obtained as a result of the analysis and the drawdown curve measured and input in advance.
As the method of digitizing this, as shown in FIG. 10, the time integrated value of the parison length from the drawdown curve is calculated by the area shaded in the figure, or the parison length at the same extrusion time as shown in FIG. Although a method of using the length can be considered, here, the latter parison length is used as the evaluation parameter.

Next, a correction parameter for correcting the viscosity coefficient is calculated. Here, the value of (parison length obtained by analysis / measured parison length) is used as the correction parameter. If the absolute value of the value (1-correction parameter) obtained by subtracting the correction parameter calculated at this time from 1 is less than or equal to a preset threshold value ε, the viscous coefficient at this time is used as a simulation material physical property parameter for calculation. The data is recorded in the memory 100 or the data storage device 110, and the process proceeds to step 6.

On the other hand, when the absolute value of (1-correction parameter) is larger than the threshold value ε, a value obtained by multiplying the above-mentioned correction parameter by the viscosity coefficient used in the previous analysis is taken as the corrected viscosity coefficient and the calculation means 100. , Or the data storage device 110. Then, the process returns to step 4 again, and reanalysis is executed based on the corrected material physical property parameters. In this way, steps 4 and 5 are performed until the absolute value of (1-correction parameter) becomes smaller than the threshold value ε.
repeat.

When the absolute value of (1-correction parameter) becomes equal to or smaller than the threshold value ε, the analysis result output means 105 outputs the analysis result in step 6, and the analysis result output device 130 outputs the parison. The length, wall thickness, and diameter are output by a method such as contour line drawing, numerical data output, graph output, and vector display. FIG. 11 is a graph showing the thickness distribution of the parison when the parison extrusion is completed. In the figure, the curve is the analysis result, and the black circle is the measured data.

[0045]

EXAMPLE An example in which the analysis method and apparatus of the present invention are applied to a practical product will be described below with reference to a box-shaped blow-molded product shown in FIG.

First, a parison extrusion test was conducted under the resin and molding conditions set at the time of actual molding, and a drawdown measuring device was used to obtain measured data of a drawdown curve as shown in FIG. In this example, glass reinforced nylon resin CM1046K4B for Toray blow (specific gravity 1.29) was used, and as molding conditions, resin temperature was 245 ° C., die / core diameter 118.6 mm / 110 mm (gap 4.3 mm), extrusion time. 73 seconds was set.

Next, in step 1, the drawdown curve data measured above was input. In this embodiment, approximate data obtained by approximating the data measured by the drawdown measuring device with a polynomial is input. For the calculation of the approximate polynomial, the approximation method by the least square method based on the measurement data is generally used, and in this embodiment, the parison length L (T) (mm) after T seconds.
Is approximated in the form of a cubic expression of the extrusion time T as in Expression (5).

Equation (5) L (T) = A × T + B × T ³ Here, the coefficients A and B are constants obtained by the method of least squares, and A corresponds to the extrusion time calculated from the drawdown curve. .

The constants A and B were calculated as follows from the drawdown curve of this example by the least squares method.

A = 5.64 B = 0.0735 FIG. 13 shows a graph in which the drawdown actual measurement data and the curve obtained by the approximate expression consisting of the above constants are plotted together. It can be seen from the figure that the measured data are on the curve obtained by the approximate equation. As a result, the extrusion speed used in the analysis is 5.64 mm / s.

Next, in step 2, analysis conditions necessary for analysis are input. From the above, the drawdown curve is input as constants A and B, the parison thickness is set to the set thickness of 4.3 mm, and the parison outer diameter is set to 118.6 mm. Further, as the material physical property value, 100 MPa was input as the specific gravity of 1.29 and the elastic modulus. As the analysis control parameter, 0.1 second was input as the time step width Δt per step. As a result, in the parison extrusion analysis, one Maxwell microelement is generated and extruded every 0.1 seconds. Further, 0.01 was set as the threshold value ε for correction.

Next, in step 3, the viscosity coefficient was set to 200 MPa / s as the initial setting of the material physical property parameters.

The analysis of step 4 is executed by setting the above conditions. The drawdown curve obtained from the initially set material property data is shown in FIG. 14 together with the measured drawdown curve. The measured parison length after extrusion for 73 seconds was 698 mm, whereas the parison length obtained by analysis was 1314 mm. As a result, the correction parameter (analyzed parison length / measured parison length) is calculated as 1.9 in step 5, and | 1-correction parameter | is 0.9, that is, the set threshold value ε0.0.
Since it exceeds 1, the viscosity coefficient of the initial value is 200 MPa / s
Then, the value is corrected to 380 MPa by multiplying this by a correction parameter, and the process returns to step 4 to perform the analysis again.

As a result of repeating the above operation, when the viscosity coefficient reaches 420 MPa / s, the threshold value ε is 0.0
Since it was 1 or less, the analysis was completed, and in step 6,
The result was output as shown in FIG.

When the parison thickness distribution obtained by the above extrusion analysis was compared with the measured thickness distribution indicated by the black circles in the figure, good agreement was confirmed as shown in FIG.

Next, a finite element model for numerical analysis is created based on the parison shape including the wall thickness distribution after extrusion calculated by the above extrusion analysis, and using this as input data, mold clamping / air blowing in blow molding. A process simulation was performed. In this simulation,
As shown in FIG. 16, the deformation of the parison due to the mold clamping and the shape change at the time of shaping into the shape of the molded product due to the air blowing inside the mold after the mold clamping were predicted and finally taken out from the mold. Predict the molded product thickness distribution at that time. This method is described in detail in Japanese Patent Application Laid-Open No. 8-258128 by the present applicant.

FIG. 17 shows the results of prediction of the wall thickness of the molded product obtained as a result of this simulation in contour lines. On the other hand, for comparison, without performing extrusion analysis, the initial parison was set as a cylindrical parison with a uniform wall thickness of 4.3 mm and a diameter of 118.6 mm, and the wall thickness when performing mold clamping / air blowing simulation The distribution prediction is shown in FIG. Comparing the two, in the case of considering the influence of drawdown according to the present invention, since the parison after extrusion was stretched by drawdown and thinned was set as the initial value of the simulation, the molded part also had a uniform thickness. Compared with the result of using the thick cylinder parison as the initial value, the result was that the wall thickness was reduced. It was confirmed that this result agrees with the tendency of the actually manufactured molded product.

[0058]

According to the present invention, the behavior of the blow molding material in the blow molding process can be accurately predicted. For example, by setting the parison shape with the predicted wall thickness distribution as the initial condition, it becomes possible to accurately predict the wall thickness of the molded product in the mold clamping / air blowing simulation after extrusion, and feed back this result. By doing so, it is possible to improve the efficiency of mold design and product design, such as setting the appropriate parison extrusion conditions, the radius of the molded product, and the parting line of the mold, shortening the product development period and improving product quality. It can contribute to improvement.

[Brief description of drawings]

FIG. 1 is a flowchart showing a schematic procedure of an embodiment of the present invention.

FIG. 2 is a diagram for explaining a drawdown curve.

FIG. 3 is an example in which a measured drawdown curve and a drawdown curve obtained by an analysis using a material physical property parameter before correction are plotted.

FIG. 4 is a configuration diagram of an analysis device used in the present embodiment example.

FIG. 5 is a diagram for explaining minute elements used for parison extrusion analysis.

FIG. 6 is a diagram in which a parison at the time of extrusion is modeled by the minute element of FIG.

FIG. 7 is a diagram for explaining the flow of parison extrusion analysis.

FIG. 8 is a diagram for explaining the correspondence between minute elements used for parison extrusion analysis and actual parison.

FIG. 9 is a diagram showing a drawdown curve for explaining a basic method of implementing the present invention.

FIG. 10 is a diagram for explaining a method of calculating a time integral value of parison length from a drawdown curve.

FIG. 11 is a graph showing a comparison between the analysis result and the actual measurement result of the wall thickness distribution of the parison in the state where the parison extrusion is completed.

FIG. 12 is a box-type blow molded product used in an example of the present invention.

FIG. 13 is a graph in which the actual drawdown data used in the example of the present invention and the curve obtained by the approximate expression are plotted together.

FIG. 14 is a graph in which an actual drawdown curve and a drawdown curve obtained from the initially set material property data are plotted together in the example of the present invention.

FIG. 15 is a diagram in which the parison extrusion analysis result in the example of the present invention is output in a contour line display of the parison shape and the wall thickness.

FIG. 16 is a diagram showing a state of mold clamping of blow molding and deformation of a parison by an air blowing simulation in an example of the present invention.

FIG. 17 is a diagram showing the results of predicting the thickness of a molded product in contour lines when the parison extrusion analysis is used in the example of the present invention.

FIG. 18 is a diagram showing the results of predicting the wall thickness of a molded product in contour lines when the parison extrusion analysis is not used in the example of the present invention.

[Explanation of symbols]

100 ... Arithmetic device 101 ... Analysis condition setting means 102 ... Initial parameter setting means 103 ... Analysis execution means 104 ... Parameter correction means 105 ... Analysis result output means 110 ... Data storage Device 120 ... Analysis condition input device 130 ... Output device 21 ... Drawdown curve 22 of material A ... Drawdown curve 31 of material B ... Drawdown curve 32 obtained by analysis ...・ Drawdown curve 51 ... Spring element 52 ... Dashpot element 53 ... Mass 61 ... Parison model 81 by one-dimensional Maxwell element ... One-dimensional Maxwell model 82 ... Parison 91 cut into slices ... Drawdown curve 92 obtained by actual measurement ... Extrusion speed 93 ... Drawdown time integration region 111 ...・ Parison wall thickness analysis result 112 ・ ・ ・ Parison wall thickness actual measurement value 121 ・ ・ ・ Box blow molding model 131 ・ ・ ・ Measurement drawdown approximate curve 132 ・ ・ ・ Parison length measurement data 141 ・ ・ ・ Parameter pre-correction analysis Drawdown curve 142 obtained by ... Approximate drawdown approximate curve 161 ... Parison shape after extrusion analysis 162 ... Parison shape after mold clamping simulation 163 ... Parison shape after air blowing simulation

Claims (14)

[Claims] 1. A numerical analysis method for simulating, by a computer, the behavior of a blow molding material in a blow molding process, comprising a drawdown curve input step of inputting drawdown curve data and a specific material physical property parameter used for the analysis. Material physical parameter initial value setting step for setting the initial value of, the extrusion analysis execution step for executing the extrusion analysis of the blow molding material by the set material physical parameter, the material physical parameter correction step for correcting the material physical parameter And an extrusion analysis execution step of performing extrusion analysis again with the corrected material physical property parameters. 2. The method for numerical analysis of blow molding material behavior according to claim 1, wherein the blow molding material is a parison extruded in a cylindrical shape from a blow molding machine. 3. The method for numerical analysis of blow molding material behavior according to claim 1, wherein the specific material physical property parameter is a viscosity coefficient of the material. 4. The step of inputting a drawdown curve,
The method for numerical analysis of blow molding material behavior according to claim 1, wherein the drawdown curve data is input as a function of extrusion time and extrusion length. 5. The method for numerical analysis of blow molding material behavior according to claim 1, wherein the drawdown curve data is measured in advance by a drawdown measuring device. 6. The extrusion molding execution step is characterized in that the blow molding material is modeled as an assembly in which microelements composed of springs and dashpots are connected in series. Numerical analysis method of behavior of blow molding material described in. 7. An analysis device for simulating the behavior of a blow molding material in a blow molding process by a computer, and an analysis condition setting means for setting analysis condition data used for the analysis, and physical properties of a specific material used for the analysis. Blow molding material behavior comprising initial parameter setting means for setting initial values of parameters, analysis executing means for executing extrusion analysis of blow molding material, and material physical property parameter correcting means for correcting the material physical property parameters Numerical analysis device. 8. The blow molding material behavior numerical analysis apparatus according to claim 7, wherein the blow molding material is a parison extruded in a cylindrical shape from a blow molding machine. 9. The numerical analysis apparatus for blow molding material behavior according to claim 7, wherein the specific material physical property parameter is a viscosity coefficient of the material. 10. The apparatus for numerically analyzing the behavior of blow molding material according to claim 7, wherein the extrusion length measurement data of the blow molding material is calculated as a function of extrusion time. 11. The numerical value of the behavior of the blow molding material according to claim 7, wherein the extrusion length measurement data of the blow molding material is previously measured by a drawdown measuring device. Analyzer. 12. The blow molding material according to claim 7, wherein the blow molding material is modeled as an assembly in which minute elements including a spring and a dashpot are connected in series. Numerical analysis device for behavior of blow molding material described. 13. A numerical analysis program for simulating the behavior of a blow molding material in a blow molding process by a computer, wherein a drawdown curve input step for inputting drawdown curve data and a specific material property parameter used for the analysis. Material physical parameter initial value setting step of setting the initial value of, the extrusion analysis execution step of executing the extrusion analysis of the blow molding material by the set material physical parameter, the material physical parameter correction step of correcting the material physical parameter , A computer-executable program that causes a computer to execute each step including an extrusion analysis step of performing extrusion analysis again based on the corrected material physical property parameters. 14. A computer-readable storage medium storing the program according to claim 13.