JPH079522A - Designing method of mold - Google Patents

Abstract

PURPOSE:To obtain a designing method of a mold which can prevent defective mold release, by a method wherein mold release resistance up to a mold releasing time is forecast through a frictional coefficient between a product and a mold and a position and a number of pieces of ejector pins are decided through a distribution of the mold release resistance. CONSTITUTION:In the third step 3, mold release resistance RA at a part A, mold elease resistance RB at a part B, mold release resistance RC at apart C are obtained respectively through the product of a frictional coefficient f (2, 0), force FA by which the part A obtained by the second step 2 is pressed against a mold, force FB by which the part B is pressed against the mold and force FC by which the part C is pressed against the mold and in the fourth step 4, a number of pieces of elector pins EA to be allotted to the part A, a number of pieces of the elector pins EB to be allotted to the part B and a number of the elector pins EC to be allotted to the part C are obtained respectively through the product of a ratio to the whole mold release resistance to each part mold release resistance RA (RB, RC) and the total number of piesces E of the input ejector pins.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold design method capable of preventing defective molding of an injection molded product.

[0002]

2. Description of the Related Art In recent years, by taking into consideration the deformation behavior in a mold and the temperature behavior in the mold after the start of deformation, which have not been taken into consideration in the past, it is possible to predict a deformation defect closer to an actual molding phenomenon and to separate it. By using the injection molding process simulation method that enables the evaluation of moldability, an appropriate mold is designed.

As this injection molding process simulation method, the present applicant has first described a filling analysis, a holding pressure flow analysis,
Cooling analysis is sequentially performed to calculate the temperature change, pressure, and specific volume change of the molding material during the injection molding process, and based on these calculation results, the state quantity of the resin at the time when each part of the molded product begins to deform is calculated. Then, by performing a thermal strain simulation from the start of deformation to the time of mold release based on the state quantity of this resin, the dimensions and temperature change behavior of the molded product in the mold are calculated, and based on the calculation results The temperature of the molded product from the time of mold release,
By performing thermal strain simulation until it becomes dimensionally stable, the dimensions and temperature change behavior of the molded product outside the mold are calculated, and based on the calculation results, warpage, sink marks, wall thickness fluctuations, etc. of the final product Proposal of an injection molding process simulation method for calculating the amount of shape deformation of a mold (Japanese Patent Application No. 4-28274)
No. 7).

[0004]

The above-mentioned injection molding process simulation method predicts and separates a deformation defect (a deformation defect such as a warp, uneven thickness, or a sink mark that occurs during molding of an injection-molded product) closer to the actual molding phenomenon. Since the moldability can be evaluated, it is possible to examine the quality of materials, molding conditions, products, and mold structure before making the mold, and change the mold structure, product shape, and molding conditions during product development compared to the past. It has the effect of reducing the time loss and cost loss associated with.

However, although the above-mentioned method can predict the stress applied to the product portion, it cannot completely prevent the mold release failure. The present invention has been made in view of such circumstances, and an object thereof is to provide a method for designing a mold that can prevent mold release defects.

[0006]

In order to achieve the above object, the method of designing a heel mold according to the present invention is such that a filling analysis, a holding pressure flow analysis, and a cooling analysis in an injection molding process are sequentially performed to perform injection molding. Calculate the temperature change, pressure, and specific volume change of the molding material during the process, calculate the state quantity of the resin at the time when each part of the molded product starts to deform based on this calculation result, and based on this calculation result The temperature of the molded product is
By performing thermal strain simulation until it becomes dimensionally stable, the dimensions and temperature change behavior of the molded product outside the mold are calculated, and based on the calculation results, warpage, sink marks, wall thickness fluctuations, etc. of the final product Using the injection molding process simulation method that calculates the amount of shape deformation of the product, find the stress distribution applied to the product part, the stress distribution, the area of the part where the product is in contact with the mold, and the space between the product and the mold. The mold release resistance until the mold was opened was predicted from the friction coefficient of No. 1, and the position and the number of protruding pins were determined from the distribution of mold release resistance.

[0007]

[Function] In the pressure / temperature / specific volume calculation unit, molded product shape data, molding condition data (injection condition, pressure holding condition, cooling condition, etc. data), resin characteristic data (viscosity, P
(vT data, mechanical properties, etc.), etc., input various condition data necessary for analysis, and perform filling analysis, holding pressure flow analysis, and cooling analysis in sequence to change the temperature, pressure, and ratio of the molding material during the injection molding process. The volume change is calculated, and the state quantity of the resin at the time when each part of the molded product starts to deform (that is, when the pressure becomes zero) is calculated based on this calculation result.

Next, in the thermal strain calculation unit in the mold, based on the state quantity of the resin calculated by the pressure / temperature / specific volume calculation unit, a thermal strain simulation from the deformation start time to the mold release time is performed. Due to the dimensions of the molded product in the mold,
Calculate temperature change behavior. Then, based on the calculation result of the in-mold thermal strain calculation unit, a thermal strain simulation from the time of mold release to the time when the molded product is stable in terms of temperature and dimensions is performed, so that the molded product outside the mold The size and temperature change behavior are calculated, and the stress distribution of the product is obtained based on the calculation result.

The force with which each part of the product is pressed against the mold is calculated from this stress distribution, and the release resistance of each part of the product is obtained by multiplying this force by the coefficient of friction between the product and the mold. Next, the number of projecting pins by which the projecting force by the projecting pin with respect to each part is larger than this mold release resistance is obtained, and the projecting pins are evenly distributed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. Table 1 below

[0011]

[Table 1] A molding die for manufacturing the molded product P shown in FIG. 1 under the molding conditions shown in FIG. 1 was designed by the method of the present invention. In addition, Fm in the table
ax is the maximum ejection force of the molding machine used.

That is, first, as a result of obtaining the stress of each element of the portions A, B, and C shown in FIG. 2 by an injection molding process simulation, the stress is σa1 to σaNA, and the portion of B is relative to the number of elements NA of the portion A. The stress was σb1 to σbNB with respect to the number of elements NB, and the stress was σc1 to σcNC with respect to the number of elements NC in the C portion. Moreover, the area of each element is Sa1-SaNA, Sb1-SbNB, Sc1.
Was ScNC.

From this result, the number and position of the protruding pins of the mold were determined by the method shown in the protruding pin arrangement calculation flow shown in FIG. That is, the calculation method will be described in detail using this flow. First, in the first step 1, the total number E of protruding pins is provisionally input. In the second step 2,
The force FA for pressing the A portion against the mold, the force FB for pressing the B portion against the mold, and the force FC for pressing the C portion against the mold.
Is calculated from the product of the total stress applied to each part and the total area of each part.

The friction coefficient f (0.2) in the third step 3 and the force FA, which is obtained in the second step 2, for pressing the portion A against the mold, the force FB, which is pressed for the mold FB, the portion C against the mold. Based on the product of the force FC, the mold release resistance RA at the A part, the mold release resistance RB at the B part, and the mold release resistance R at the C part.
Find C respectively. In the fourth step 4, the product of the ratio of the release resistance RA (RB, RC) of each part to the total release resistance and the input total number E of protruding pins is assigned to the A portion. The protruding pin numbers EA and B are assigned. Number of protruding pins E
The protruding pin numbers EC assigned to the B and C parts are obtained.

In the fifth step 5, the ratio of the number of protruding pins EA (EB, EC) assigned to each part to the total number E of protruding pins and the maximum ejecting force Fmax (2 of the molding machine used.
000 kgf), the protrusion force EFA of the portion A, the protrusion force EFB of the portion B, and the protrusion force EFC of the portion C are obtained. Ejection force of each part EFA (EFB, EFC) in 6th step 6
And the release resistances RA (RB, RC) of the respective parts are compared, and if the protruding force EFA (EFB, EFC) of the respective parts becomes larger than the release resistance RA (RB, RC) of the respective parts, the seventh step 7 is carried out. If the mold release resistance is larger than the protruding force even at one place, the process returns to the first step 1 to increase the total number E of the protruding pins by one from the previous input, and the calculations of the second to sixth steps are performed again.

On the other hand, in the seventh step 7, the length LA (LB, LC) of each part shown in FIG. 2 is divided by the number of protruding pins EA (EB, EC) of each part obtained in the fourth step 4 to obtain A. The protruding pin pitch PA of the portion, the protruding pin pitch PB of the portion B, and the protruding pin pitch PC of the portion C are obtained, respectively. As a result of the above determination, EA is 2
Book, 3 EBs, 3 ECs, 15mm PA, 1PB
It was 0 mm and PC was 10 mm.

Based on this result, a mold K shown in FIG. 4 was prepared and a molded product as shown in FIG. 1 was manufactured. As a result, a product P as designed could be obtained without causing mold release defects. It was The injection molding process simulation method used in the present invention will be described below with reference to FIG. 5 showing the electrical configuration of the applied apparatus.

In the figure, the output of the data input section 11 for inputting various condition data necessary for analysis is the filling analysis,
It is guided to the pressure / temperature / specific volume calculation unit 12 that performs the pressure-holding flow analysis, the cooling analysis, etc., and the pressure / temperature / specific volume calculation unit 1
The output of No. 2 is guided to the storage unit 13 that stores the data of the state quantity of the resin calculated here. In addition, the storage unit 13
Is guided to the in-mold thermal strain calculation unit 14, and the output of the in-mold thermal strain calculation unit 14 is the external mold heat strain calculation unit 1.
It has a structure guided by 5.

The data input section 11 is for molding product shape data,
Various condition data necessary for analysis such as molding condition data (each data such as injection condition, pressure holding condition, cooling condition, etc.), data representing resin properties (viscosity, PvT data, mechanical properties, etc.) are input. The pressure / temperature / specific volume calculation unit 12 calculates the temperature change, pressure, and specific volume change of the molding material during the injection molding process by sequentially performing the filling analysis, the holding pressure flow analysis, and the cooling analysis. When each part of the molded product starts to deform based on (that is, when the pressure becomes zero)
Although it is not shown in the figure, it is composed of a filling analysis device, a pressure-holding flow analysis device, and a cooling analysis device for performing cooling analysis inside and outside the mold. . In addition, each analysis here is basically the same as the analysis method conventionally performed.

The in-mold thermal strain calculation unit 14 calculates the pressure / temperature /
Based on the state quantity of the resin calculated by the specific volume calculation unit 12,
This is a block for calculating the dimension and temperature change behavior of the molded product in the mold by performing thermal strain simulation from the start of deformation to the release. Outer mold thermal strain calculation unit 15
Is based on the calculation result of the thermal strain calculation unit 14 in the mold,
By performing thermal strain simulation from the time of mold release until the molded product is stable in temperature and dimension, the dimension and temperature change behavior of the molded product outside the mold are calculated, and based on the calculation results, the final product This is a block for calculating the amount of shape deformation such as warp, sink mark, and thickness variation.

Next, the operation of the injection molding process simulation apparatus having the above configuration will be described with reference to the flow charts shown in FIGS. First, the operator uses the data input unit 11 to obtain molded product shape data, molding condition data (injection conditions, pressure holding conditions, cooling conditions, and other data) and resin characteristic data (viscosity, PvT data, mechanical properties, etc.).
Various condition data necessary for analysis such as the above is input (step S1).

The pressure / temperature / specific volume calculation unit 12 first performs a filling analysis based on these input data (step S2), and changes in the pressure and temperature of the resin during the process of filling the resin at high temperature and high pressure. Calculate the behavior. Next, when the filling of the resin into the mold is completed, the pressure-holding flow analysis is executed based on the amount of state of the resin at the time of completion of the filling calculated by the filling analysis (step S3). The holding pressure flow analysis calculates the change behavior of the resin pressure, temperature, and specific volume during the compensating flow cooling process from the completion of filling to the compensating flow stop (gate seal).

After that, when the compensating flow is stopped, the change of the state quantity of the resin during the cooling process in the mold until the start of deformation is based on the state quantity of the resin when the compensating flow is stopped calculated by the holding pressure flow analysis. Data of the calculated and obtained state quantity is stored in the storage unit 13 (step S4). In-mold thermal strain calculation unit 14
On the basis of the data indicating the state quantity of the resin stored in the storage unit 13, performs a thermal strain simulation from the start of deformation to the time of mold release (step S5), and measures the dimensions and temperature of the molded product in the mold. Calculate change behavior.

That is, the in-mold thermal strain calculation unit 14 calculates the temperature change of the molded product in the mold after a lapse of a minute time, based on the state quantity of the resin at the start of deformation inputted from the storage unit 13. Yes (step S51). Then, based on the calculated temperature change, thermal strain analysis is performed while considering the constraint conditions of the mold, creep phenomenon of the molded product, etc., and the deformation amount of the molded product is obtained (step S52).

After that, the in-die thermal strain calculation unit 14 checks the contact state between the die and the molded product based on the deformation amount, and determines the contact state (step S53). In this judgment, if it is judged that the surface of the molded product is in the state of being separated from the mold surface, the temperature boundary condition (heat transfer coefficient) of the surface is determined in the condition that the surface is not in contact with the mold. The condition is changed to (steps S54 and S55). When it is determined in step S54 that each surface of the molded product is in contact with the mold surface, the process proceeds to step S56 without changing the temperature boundary condition.

Then, in step S56, it is determined whether or not the mold release time is reached. If the mold release time is not reached, the process returns to step S51 again, and if the temperature boundary condition is changed. Calculates the temperature change of the molded product after a lapse of a minute time by using the changed temperature boundary condition. The calculations in steps S51 to S56 are repeated until the mold release time is reached. Then, when the mold release time comes in step S56, step S5
The data of the temperature, the amount of deformation, and the stress of each part of the molded product calculated last in 1 and step S52 are given to the external mold thermal strain calculation part 15. (Step S57).

The external mold thermal strain calculation unit 15 determines the temperature and dimension of the molded product from the time of mold release based on the temperature, deformation amount, and stress data provided by the internal mold heat strain calculation unit 14. A thermal strain simulation is performed until it stabilizes, and the dimensions and temperature change behavior of the molded product outside the mold are calculated. Then, based on the calculation result, the amount of shape deformation such as warp, sink mark, wall thickness variation, shrinkage amount (dimension) of the final product is calculated (step S6).

[0028]

Since the mold designing method according to the present invention is configured as described above, it is possible to easily set an appropriate number and position of the projecting pins, and to perform mold release failure without modifying the mold. Can be prevented. Therefore, the die cost can be reduced without waste.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a product manufactured by a mold designing method according to the present invention.

FIG. 2 is an element model of the molded product.

FIG. 3 is a flowchart of a protruding pin arrangement calculation of the mold designing method according to the present invention.

FIG. 4 is a cross-sectional view of a mold.

FIG. 5 is a block diagram showing an electrical configuration of an apparatus to which the injection molding process simulation method used in the mold designing method of the present invention is applied.

FIG. 6 is a flowchart for explaining the operation.

FIG. 7 is a flowchart for explaining the operation.

[Explanation of symbols]

 Part A Part B Part C Part K Mold P Product

Claims (1)

[Claims] 1. A filling analysis, a pressure-holding flow analysis, and a cooling analysis in an injection molding process are sequentially performed to calculate a temperature change, a pressure, and a specific volume change of a molding material during the injection molding process,
Based on this calculation result, the state quantity of resin at the time when each part of the molded product starts to deform is calculated, and based on this calculation result, a thermal strain simulation from the time of mold release until the molded product is stable in temperature and dimension The injection molding process that calculates the dimension and temperature change behavior of the molded product outside the mold by performing the above, and calculates the amount of shape deformation such as warpage, sink mark, wall thickness fluctuation of the final product based on the calculation result. Using the simulation method, find the stress distribution on each part of the product, and from this stress distribution, the area of the part where the product is in contact with the mold, and the coefficient of friction between the product and the mold, The mold designing method is characterized by predicting the mold release resistance up to and determining the position and the number of protruding pins from the distribution of the mold release resistance.