JPH07117113A - Design method for optimum blow molding temperature by blow molding analysis - Google Patents

Abstract

PURPOSE:To reduce a period of development of products by rnaking analyses while giving a parison, a bottle shape and a blow pressure load with reference to a plurality of blow molding temperatures, finding the functions of molding temperatures to display them on a graph with reference to a maximum thickness or a minimum thickness and evaluating and designing a range of proper molding temperatures before making a mold. CONSTITUTION:Surface temperatures of a preform are varied to five levels of 80, 90, 100, 110 and 120 deg.C, fixed input conditions are applied thereto, the analysis and arithmetic operation of blow molding are successively executed, a maximum value and a minimum value for the wall thickness of the preform are obtained and data on each blow molding temperature are graphed. The characteristic curves of the graph are represented by thetamax=fmax (T) and thetamin=fmin (T). That is, a maximum line and a minimum line of a minimum wall thickness and a maximum wall thickness are set and, in the case where the surface temperatures of the preform are on the axis of abscissa, the surface temperatures of the preform become unsuitable if they exceed or are less than these ranges. Further, the range of an optimum wall thickness is set on the basis of experiences and actual results, and it can be judged that the surface temperatures are in a range of 91 to 108 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a preform or parison, which is a thermoplastic polymer primary molded article, when the preform or parison, the shape of the final blow-molded article and the blow pressure condition are set in advance. The present invention relates to a method for evaluating and designing an appropriate range of a blow molding temperature for obtaining a high quality and high performance final molded article by blow molding analysis.

[0002]

2. Description of the Related Art When analyzing (simulating) the large deformation contact problem in blow molding of a plastic container, as shown in FIG. 3, the shape of a preform or parison which is a thermoplastic polymer primary molding and a blow molding metal are used. Structural analysis that calculates the deformation of the heated preform or parison using the numerical analysis method such as the finite element method by dividing the mold shape into minute elements, or the deformation of the heated preform or parison Structural analysis that performs calculations,
Heat conduction analysis that performs heat conduction (temperature transfer) calculation that occurs when a heated preform or parison deforms, and preform or parison-cooling that occurs when the heated preform or parison deforms and contacts the cooling mold. The deformation amount of each element can be calculated by using a numerical analysis method characterized in that contact heat transfer analysis for calculating contact heat transfer between molds is coupled and solved simultaneously. In the blow molding analysis method that deals with such a large deformation contact problem, the temperature-dependent physical property value of the resin used, the temperature distribution of the preform or parison immediately before molding, and the blow molding conditions (time change of blow air pressure load) are used. By inputting and calculating the deformation completion time, the progress of deformation of the preform and the wall thickness distribution at each time obtained by arbitrarily dividing the deformation completion time can be calculated. These techniques are described by the present inventors in the International Journal For Numerical Methods.
Published in In Engineering (1991). FIG. 4 shows the progress of analysis of preform deformation in the finite element model. Further, FIG. 5 shows the result of wall thickness distribution analysis performed by blow molding analysis in the finite element model.

[0003]

However, in the blow molding analysis method dealing with the large deformation contact problem described above, which of the several input conditions is appropriate, what blow molding temperature is the best, etc. No means for making a decision is known, and therefore the decision as to whether or not the calculation result is appropriate has to rely on empirical know-how obtained by repeating the comparison between the analysis result and the actual blow molding. As described above, the conventional blow molding analysis method for dealing with the large deformation contact problem is the empirical or experimentally obtained preform or parison of the desired preform or parison, the shape of the blow molded product, and the resin used. It is mainly used to judge the suitability of the product thickness distribution by inputting the temperature distribution just before molding and blow molding conditions (time change of blow air pressure load). No evaluation has been attempted. Therefore, an object of the present invention is to evaluate and design an appropriate range of blow molding temperature for a required blow molding bottle, preform or parison shape by blow molding analysis of a preform or parison which is a thermoplastic polymer primary molding. Is to provide a way to do.

[0004]

That is, the present invention is
(1) A structure in which the shape of a preform or parison and a blow molding die are divided into minute elements, and (A) the deformation of the heated preform or parison is calculated by using a numerical analysis method such as the finite element method. Analysis or (B) (a) Structural analysis for performing deformation calculation of a heated preform or parison, (b) Thermal conduction analysis for performing heat conduction (temperature transfer) calculation that occurs during deformation of a heated preform or parison And (c) Simultaneously solve by contact heat transfer analysis that performs contact heat transfer calculation between the preform or parison and the cooling mold that occurs when the heated preform or parison deforms and contacts the cooling mold. In the blow molding analysis in the blow molding temperature design, by calculating the deformation amount of each element by using the numerical analysis method characterized by (2)
Preform or parison shape fixed for multiple blow molding temperatures, blow molding bottle shape, blow pressure load is applied and analysis is performed until each element completely contacts the mold, and all elements are calculated based on the displacement calculation results obtained. For the maximum thickness θmax or the minimum thickness θmin in the inner wall thickness direction, a function with each blow molding temperature T as a variable is obtained as θmax = fmax (T) and θmin = fmin (T), and (3) the function is graphically represented. Display,
It is a method of designing an optimum blow molding temperature by blow molding analysis characterized by evaluating and designing an appropriate range of blow molding temperature for a given preform or parison and final molded product bottle shape.

Further, in the above design method, the maximum value θmax and the minimum value θmin are set as the limit values in the thickness direction thickness θ of an arbitrary element, and the above function is evaluated to evaluate an appropriate range of the blow molding temperature. It is an object of the present invention to provide a method for designing an optimum blow molding temperature by a blow molding analysis characterized by designing.

[0006]

According to the method for designing the optimum blow molding temperature by the blow molding analysis according to the present invention, a plurality of blow moldings are analyzed by the blow molding analysis which deals with the large deformation contact problem of the preform or parison which is the thermoplastic polymer primary molding. Deformation state of each minutely divided element of the preform shape model with respect to the molding temperature at the completion of molding is obtained by calculation, and each blow molding temperature is calculated for the maximum or minimum thickness in the thickness direction of all elements. It is possible to obtain a function as a variable, display this function graphically on a display device, and evaluate and design an appropriate range of blow molding temperature for a predetermined preform, parison, or final molded product bottle shape. In this case, the maximum and minimum values are set as the limit values for the thickness direction thickness of an arbitrary element, and the appropriate performance is considered in consideration of the required performance (pressure resistance strength, compression strength, etc.) and the optimum wall thickness distribution for the final molded product bottle. Blow molding temperature range can be evaluated and designed.

[0007]

【Example】

Example 1 A method for designing an optimum blow molding temperature by blow molding analysis according to the present invention will be described with reference to the drawings. In the present invention, the procedure for performing blow molding analysis of a preform or parison that is a thermoplastic polymer primary molded body for a shape model of a predetermined molded article is the same as in the conventional simulation. That is, as shown in FIG. 3, in order to analyze the resin deformation (blow molding) in the blow mold, element division of the shape model of the blow mold and the preform or parison is performed (the illustrated example is a quadrilateral 4-node). Elements are used, but a quadrangle 8-node or 9-node element may also be used), and the finite element method is applied. Then, a preset optimum blow pressure is input to the inner wall of the preform, the mold is defined as a rigid body that does not deform, and the mouth and neck of the preform is constrained so that it does not move in the vertical direction. Conduction analysis-Contact heat transfer analysis Move to blow molding analysis by complete coupled analysis.

The blow molding analysis of this embodiment deals with the phenomenon of biaxial stretch blow molding. Its characteristic is blow molding while pushing up the preform with a stretch rod. At this time, the expansion ratio from the preform to the bottle is obtained by multiplying the axial expansion ratio and the circumferential expansion ratio, and is 10 times or more in the plane direction. It is a point that becomes a super large deformation of. In FIG. 2, 1 is a preform, 2 is a cooling mold, and 3 is a stretch rod. The stretch rod is driven by compressed air, and the molding starts when this rod pushes up the preform, then blow air flows out from the gap between 1 and 3, and the preform expands and deforms in the axial and circumferential directions. Then, it is cooled and solidified by coming into contact with the mold to form the final molded product in the form of a bottle. Fixed input conditions for the simulation are preform or parison, mold shape of blow-molded product, temperature-dependent physical property data of resin to be used, and change of blow pressure and stretch pressure in load time history. The blow molding temperature design is a parameter for obtaining the optimum wall thickness distribution of the blow molded product.

The shapes to be analyzed are the portion excluding the mouth of the preform and the mold as shown in FIG.
For one type of preform and blow molding die shape,
Preform surface temperature of 80, 90, 100, 110,
Variable to 5 kinds of 120 ° C., the fixed input condition is applied, the blow molding analysis calculation is sequentially executed, and the maximum value and the minimum value in the thickness direction of all the elements of the obtained results are extracted, The data is for each blow molding temperature. If the data obtained by repeating this procedure is graphed, the horizontal axis represents the preform surface temperature and the vertical axis represents the thickness of one element with the maximum and minimum values in the thickness direction of all elements as parameters. The characteristic curve diagram shown in FIG. 1 is obtained.

Next, the following equation can be obtained by formulating the characteristic curve shown in FIG.

Θmax = fmax (T) and θmin = fmin (T)

As a reference value for evaluation, the minimum wall thickness for one element considering the required performance for the final product as shown in FIG.
When the maximum wall thickness (MAX, MIN line in the figure) is set and the preform surface temperature is taken on the horizontal axis, if the preform surface temperature is above or below this range, the molding temperature will be relative to the product structure. Can be determined to be unsuitable. If the thickness does not reach or exceeds a certain limit value, the required performance for the product, namely gas loss, creep deformability, stress crack resistance, heat resistance, impact resistance,
Compressive strength, compressive strength, etc. do not satisfy the respective required ranges, and the value as a product is lost. Therefore,
Depending on the type of filling (drinking water, etc.), preform or parison, and bottle shape of the final molded product, the optimum thickness range is generally set from the experience or experience accumulated so far, as shown in Fig. 1. Target. In Fig. 1, the preform surface temperature that satisfies the required performance of the product is 91 to 1
It can be judged to be in the range of 08 ° C.

Therefore, this evaluation method allows absolute evaluation of the preform surface temperature when the molding conditions (change of blow pressure / stretch pressure with time), preform or parison, and final molded product bottle shape are fixed input values. It is extremely important as a means for supporting the blow molding temperature design for obtaining the optimum blow molding product thickness distribution.

[0014]

INDUSTRIAL APPLICABILITY According to the present invention, the required preform or parison, by using the blow molding analysis,
It is possible to support the optimum blow molding temperature design to obtain a higher quality molded product by a simple graphic display, depending on the shape of the blow molded product or the molding conditions (stretch pressure, blow pressure). Therefore, by using this simulation and evaluation method, the optimum design of the blow molding temperature according to the user's needs (the optimum design of the preform and the blow molded product) can be predicted before making the mold. That is, the period from design to product development, which has been performed by repeating conventional trial and error, is significantly shortened, and it also leads to reduction in development costs such as mold manufacturing.

[Brief description of drawings]

FIG. 1 shows a method of designing an optimum blow molding temperature by a blow molding analysis.
It is a graph chart which made the maximum value and the minimum value of the thickness direction thickness of an element into data.

FIG. 2 is a plan view showing the shapes of a preform which is a polymer primary molded body, a blow molding die, and a stretch rod.

FIG. 3 is a finite element mesh diagram of a preform and a blow mold.

FIG. 4 is a diagram showing the progress of analysis of preform deformation in the shape model shown in FIG. 3; (1) shows the initial setting state of the molding analysis, proceeds from (2) to (6), and (7)
Indicates the end state of the molding analysis.

5 is a wall thickness distribution analysis result obtained by performing a blow molding analysis on the shape model shown in FIG. The calculated value shows the analysis result, and the experimental result shows the result of blow molding in the experiment.

[Explanation of symbols]

 1 Preform 2 Blow Molding (Cooling) Mold 3 Stretch Rod 4 Preform Mesh 5 Blow Molding (Cooling) Mold Mesh

Claims (2)

[Claims] (1) A preform or parison and a blow molding die shape are divided into minute elements, and a numerical analysis method such as a finite element method is used to (A) heat the preform or parison. Structural analysis for deformation calculation, or (B)
(A) Structural analysis for calculating deformation of the heated preform or parison, (b) Thermal conduction analysis for calculating heat conduction (temperature transfer) that occurs during deformation of the heated preform or parison, and (c) Heating. Numerical values characterized by simultaneous contact heat transfer analysis that performs contact heat transfer calculation between preform or parison-cooling mold that occurs when the preform or parison deforms and contacts the cooling mold By using the analysis method to calculate the amount of deformation of each element, in blow molding analysis in blow molding temperature design, (2) fixed preform or parison shape for a plurality of blow molding temperatures, blow molding bottle shape,
Analysis is performed until a blow pressure load is applied to each element until it completely contacts the die, and the maximum amount of displacement θmax or the minimum thickness θmin in all elements is calculated according to the displacement calculation results obtained.
For each of the blow molding temperatures T, the functions θmax = fmax (T) and θmin = fmin (T) are obtained, and (3) the function is graphically displayed.
A method for designing an optimum blow molding temperature by blow molding analysis, characterized by evaluating and designing an appropriate range of blow molding temperature for a given preform, parison, or final molded product bottle shape. 2. In the method for designing an optimum blow molding temperature by blow molding analysis according to claim 1, the maximum value θma as a limit value for the thickness direction thickness θ of an arbitrary element.
A method for designing an optimum blow molding temperature by blow molding analysis, wherein x and a minimum value θmin are provided, and the function is evaluated to evaluate and design an appropriate range of blow molding temperature.