JP2828897B2 - Mold making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a mold, and more particularly to a method of manufacturing a multi-cavity injection molding mold.

[0002]

2. Description of the Related Art In a multi-cavity mold having a plurality of cavities, a sprue connected to an injection molding machine and each cavity are usually connected through a main runner and a sub-runner or a gate branched from the main runner. However, if the resin flow paths to the cavities are completely the same, the time at which the resin is completely filled into the cavities is different, and the time at which the molded product can be taken out also differs. Therefore, in order to form a mold that can efficiently mold a good molded product, it is necessary to design and manufacture the resin flow path to each cavity so that the resin filling completion time is the same.

For this purpose, Japanese Patent Application Laid-Open No. H2-120643 discloses that a resin flow path is designed by simulating the flow state of a molding material (thermosetting resin) in a mold by flow analysis. I have.

[0004]

In this case, even if the completion of filling each cavity is the same on a simulation, if a mold based on this design is manufactured and actually used for molding, Due to analysis errors and other factors not included in the analysis conditions, the completion time of filling is often not the same.In addition, the mold correction processing as a countermeasure must be repeated many times before the completion of filling. The fact is that they cannot be the same.

The present invention has been made in view of such a point, and an object of the present invention is to minimize the number of corrections required to make the completion time of resin filling in each cavity the same. To provide a mold manufacturing method.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a resin molding die having a plurality of cavities, wherein a resin characteristic, a die characteristic, a molded product shape, molding conditions and the like are inputted. Value, the resin filling completion time for each cavity is obtained by analysis using the shape data of the resin flow path to the cavity as a parameter, and the resin flow path shape in which the resin filling completion time in each cavity is equal is determined. Create a test mold with a resin flow path shape, mold using the created test mold, measure the resin filling state in each cavity, and specify a specific cavity from the resin filling state measured for each cavity. To determine the filling ratio of the other cavities with respect to, fixed the resin flow path shape data for the specific cavity, and changed the resin flow path shape data for the other cavities By performing the above analysis, a change curve of the filling ratio between a specific cavity and another cavity with the change of the shape data is obtained, and the change curve is corrected by a correction amount derived from the filling ratio based on the actual measurement. It is characterized in that the shape data when the filling ratio of the corrected change curve becomes 1 is used as the resin flow path shape data of another cavity, and a mold is manufactured with the above flow path shape.

[0007]

According to the present invention, since the flow path shape obtained by the analysis is corrected by the difference between the case where it is actually used for molding and the analysis value, the final flow path shape is determined and the mold is manufactured. In addition, it is possible to take into account a state where the flow of the resin in the mold at the time of actual molding cannot be grasped only by analysis.

At this time, the resin filling completion time for each cavity is obtained by analysis using the resin characteristics, mold characteristics, molded product shape, molding conditions and the like as input values, and using the shape data of the resin flow path to the cavity as parameters. In order to determine the shape of the resin flow path in which the resin filling completion time in each cavity is equal, if the shape of the resin flow path is determined under the condition of minimizing the molding cycle time, the molding cycle time is also reduced. be able to.

Further, if the cavity and the resin flow path are divided into a plurality of symmetrical blocks around the sprue and the analysis and correction are performed on the resin flow path in a single block, the calculation time for the analysis is reduced. Can be shortened. In order to measure the resin filling state in each cavity by performing molding using the created test mold, when measuring the resin filling state from the molded product molded by changing the resin filling amount, it is a test to make the initial production It is not necessary to add a measuring device to the tool, and the final tool can be manufactured by modifying the tool.

Further, if the sprue, the main runner and the gate in the shape data of the resin flow path to the cavity are fixed input values, and the shape data of the sub-runner is a parameter, the number of parameters is reduced. It will be easier.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiment. First, in the present invention, a mold design for obtaining a target molded product is analyzed by a flow analysis when the molded product is molded. The simulation is performed so that the filling of the molding material into each cavity is completed at the same time.

That is, molded product shape data (data of the cavity shape of the mold used, obtained by dividing into minute finite elements), resin data (physical properties such as viscosity, specific heat, density, solidification temperature, etc.) Data), molding condition data (data of resin temperature, mold temperature, injection time, etc.),
Based on the mold characteristics (thermal conductivity, specific heat, density), etc., the pressure loss value and filling completion time for each cavity are determined by flow analysis, using the shape data of the resin flow path leading to the mold cavity as a parameter. The resin flow path (diameter and length of each of the sprue 11, the main runner 12, the sub-runner 13, and the gate 14 shown in FIG. 2) reaching the cavity 10 is determined so that these values become the same in each cavity.

The above flow analysis is performed, for example, by the following equation of motion.

[0014]

(Equation 1)

(X, y: flow direction, z: thickness direction, τ
x, τy: shear stress in x, y directions, P = pressure)

[0016]

(Equation 2)

(U, v: a continuous equation given by the flow velocity in the x and y directions (distribution in the thickness direction)

[0018]

(Equation 3)

(T: temperature (distributed in the thickness direction), η: viscosity, λ: thermal conductivity, ρ: density, C _P : specific heat, γ: shear rate (distributed in the thickness direction), J: constant, t: time), the flow field of the molding resin can be obtained as a function of position and time, and the resin pressure and resin viscosity can be obtained together with the position information and time information. From this, the pressure loss value of the cavity 10 and the point of time when the filling is completed can be obtained.

Then, a test mold is manufactured by a mold design having a flow path in which the pressure loss value and the filling completion time of each cavity 10 are the same, and actual molding is performed by this mold to fill each cavity. The filling state of the molding material is actually measured, and the filling ratio between a specific cavity and another cavity is examined. As shown in FIG. 3, the filling ratio is determined by arranging the pressure sensors 5a and 5b in the cavities 10a and 10b and examining the times ta and tb from the start of injection to the rise of the pressure sensors 5a and 5b. Cavity 1
Ratio of time required for filling at filling ratio A / B of 0a, 10b t
a / tb (A / B = ta / tb).

The flow path shape for the specific cavity is fixed, and how the filling ratio between the specific cavity and the other cavity changes when the flow path shape for the other cavity is changed is described above. Determined using flow analysis. FIG. 4 shows a filling ratio change curve f when the diameter of the sub-runner reaching another cavity is changed. In this case, the diameter P of the sub-runner where the filling ratio is 1 is the same as that of the die manufactured above.

Next, the above-mentioned filling ratio change curve f is corrected by the filling ratio A / B obtained by performing actual molding.
That is, as shown in FIG. 5, the filling ratio A / B is set so that the filling ratio when the sub-runner diameter is P becomes the filling ratio (indicated by X in the drawing) obtained by performing the actual molding. Is a value obtained by subtracting 1 which is the filling ratio on the analysis from the above, and the filling ratio change curve f
To obtain a filling ratio change curve fc. Then, the sub-runner diameter Pd at the intersection of the filling ratio change curve fc and the filling ratio 1 is set as the sub-runner diameter of another cavity from which the filling ratio is determined with respect to the specific cavity. As a result, the completion of filling the specific cavity and the completion of filling the other cavities are simultaneous.

The evaluation can be performed in the same manner as the sub-runner in the flow path other than the sub-runner. Further, even when there are three or more cavities, the filling ratio with respect to a specific cavity is obtained in each cavity and compared to obtain a flow path having the same filling completion time. In any case, the flow path shape obtained by the flow analysis was corrected in accordance with the difference between the case where it was actually subjected to molding and the analysis value to obtain the final flow path shape, and thus the flow path shape was obtained in this manner. If a mold is manufactured in the flow path, it is possible to surely obtain a mold in which the completion time of filling each cavity is the same. And since the manufacture of the mold here may be a correction of the mold manufactured first, in that sense, it is possible to manufacture the mold required with a very small number of corrections. .

By the way, in the above embodiment, the filling ratio was obtained by the ratio ta / tb of the required filling time measured using the pressure sensor. In this case, the mold manufactured first was modified due to the relation of the pressure sensor. In order to make it difficult to form an actual molded product, the filling ratio may be derived from the weight ratio or volume ratio of the molded product molded in each cavity. When the weight ratio is used, as shown in FIG. 6 (a), each weight Wa, Wb of the molded product obtained by completely filling each cavity 10a, 10b with the molding material is shown in FIG. 6 (b). The weights Wa ', W of the incompletely filled molded product obtained by reducing the filling amount as described above, that is, by stopping the filling before the complete filling.
From (b ′), (Wa ′ / Wa) / (Wb ′ / Wb) is obtained, and this weight ratio is defined as a filling ratio A / B. However,
Since the weight ratio before complete filling changes as shown in FIG. 7 with an increase in the amount of injected resin, immediately before the change before complete filling becomes large (the filling ratio is 90 to 90% by weight). 9
(8%) (weight ratio of several points).

When the filling ratio change curve f is corrected by the filling ratio A / B based on the weight, the filling ratio A / B
And the difference between the weight equivalent ratio of the specific cavity and the other cavity in the analysis. The weight equivalent ratio is obtained by first analyzing the filling time and injection speed until the filling rate (incompletely filled molded article weight / completely filled molded article weight) when the above-mentioned incompletely filled molded article is actually molded. The obtained injection speed is multiplied by the filling time, and the product is further multiplied by the cross-sectional area of the position where the injection speed is determined in the resin flow path and the resin flow path. To obtain the ratio between the two weight equivalents.

When the volume ratio is used, each cavity 1
Each of the volumes Ca and Cb of the molded product obtained by completely filling the molding materials into the parts 0a and 10b and the filling amount as shown in FIG. 6B are reduced, that is, the filling is stopped before the complete filling. Each volume Ca ', Cb' of the incompletely filled molded product obtained by
From this, (Ca ′ / Ca) / (Cb ′ / Cb) is obtained, and this volume ratio is defined as a filling ratio A / B, and the filling is performed by a difference between the filling ratio A / B and the volume equivalent ratio by analysis. The ratio change curve f is corrected. The volume ratio equivalent amount is obtained by analyzing the filling time and the injection speed until the filling rate (uncompletely filled molded product volume / completely filled molded product volume) when the above-mentioned partially filled molded product is actually molded, The product is obtained by multiplying the product of the obtained injection speed and the filling time by the cross-sectional area at the position where the injection speed is determined in the resin flow path.

When a large number of cavities 10 are formed in a mold, the main runner 12, the sub-runner 13, the cavities 10 and the like are usually arranged symmetrically about the sprue 11. For example, in the arrangement shown in FIG. 8, the block B1 and the block B4 are in a point symmetrical relationship around the sprue 11, the block B1 and the block B2 are in a symmetrical relationship about a symmetry axis La passing through the sprue 11, and The block B3 passes through the sprue 11 and the main runner 12, and the axis of symmetry Lb
Are symmetrical. In such a case, block B
It is only necessary to make the resin flow path for the cavity 10 in 1 symmetrical for evaluation, and the time required for analysis can be reduced. Further, as is apparent from this figure, it is practical to perform an analysis using the sub-runner 13 as a parameter in the resin flow path.

When a mold is designed by the first analysis, molded product shape data, resin data, molding condition data,
From the mold characteristics (thermal conductivity, specific heat, density), etc., select the conditions (eg, mold temperature, resin temperature, injection speed, etc.) that are important for shortening the molding cycle time, and select the molding machine capacity and resin. By determining the molding condition width from the properties and the like, and performing injection molding analysis at several points within the molding condition width at each selected condition, the relationship between the above-mentioned selection condition and the molding cycle time is determined as shown in FIG. And the combination of the selection conditions when the molding cycle time is minimized,
Under these conditions, if the shape data of the resin flow path is obtained by the flow analysis described above, it is possible to obtain the resin flow path shape data in which the molding cycle time is short and the filling of the resin into each cavity is completed at the same time.

In the case of thermoplastic resin molding, the molding cycle time is the sum of the filling time, the dwell time, the cooling time, and the mold opening time. In the case of thermosetting resin molding, the molding cycle time is the filling time, the curing time, In the injection molding analysis for minimizing the molding cycle time, the filling time may be used as the molding cycle time.

[0030]

As described above, in the present invention, the final flow path shape is obtained by correcting the flow path shape obtained by the analysis based on the difference between the case of actually performing molding and the analysis value. Since the mold is manufactured with the flow path obtained in this way, it is possible to take into account the state where the flow of the resin in the mold at the time of actual molding could not be grasped by analysis alone, Therefore, it is possible to manufacture a mold in which the filling of each cavity is completed at the same time without repeating the correction many times.

Then, the resin filling time for each cavity is obtained by analysis using the resin characteristics, mold characteristics, molded product shape, molding conditions and the like as input values and using the shape data of the resin flow path to the cavity as a parameter. In defining the resin flow path shape in which the resin filling completion time in each cavity is equal, if the resin flow path shape is determined under the condition of minimizing the molding cycle time, the molding cycle time is short, and A mold that completes simultaneous filling can be obtained.

Further, if the cavity and the resin flow path are divided into a plurality of symmetric blocks around the sprue, and the analysis and correction are performed on the resin flow path in a single block, the evaluation portion is limited. Calculation time for analysis can be reduced. Performing molding using the test mold created and measuring the resin filling state in each cavity.When measuring the resin filling state from the molded product molded by changing the resin filling amount, increase the filling ratio. Since it can be obtained accurately and it is not necessary to add a measuring device to the test mold to be initially produced, the final mold can be produced by modifying this.

Furthermore, if the sprue, main runner, and gate of the shape data of the resin flow path to the cavity are fixed input values and the shape data of the sub-runner are parameters, the number of parameters is reduced, so that the analysis calculation is not performed. It will be easier.

[Brief description of the drawings]

FIG. 1 is a flowchart according to the present invention.

FIG. 2 shows an example of a resin flow path, (a) is a side view,
(b) is a front view, and (c) is a bottom view.

3A and 3B show a method of measuring a filling ratio in one embodiment, in which FIG. 3A is a model diagram showing an arrangement of a pressure sensor as a measuring means, and FIG. 3B is an explanatory diagram of an output of the pressure sensor.

FIG. 4 is an explanatory diagram of a filling ratio change curve.

FIG. 5 is an explanatory diagram of a correction filling ratio change curve.

FIG. 6 (a) is an explanatory view of a completely filled molded article, and FIG. 6 (b) is an explanatory view of an incompletely filled molded article.

FIG. 7 is an explanatory diagram showing a relationship between an injection amount and a weight ratio.

FIG. 8 is an explanatory diagram of a symmetric relationship between resin flow paths.

FIG. 9 is an explanatory diagram showing a correlation between a mold temperature and a molding cycle time, a resin temperature and a molding cycle time, and an injection speed and a molding cycle time.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-91703 (JP, A) JP-A-6-39882 (JP, A) "Special issue: Quality improvement of plastic products from the viewpoint of runner and gate design", Mold Technology, Vol. 4, No. 8 (August 1989), published August 1, 2001, p. 18-68 Louis T.M. Manzion, Translated by Osamu Amano, “Injection Molding CAE”, Industrial Research Council, Inc., published on February 10, 1989, p. 192-202, p. 272-284 (58) Fields investigated (Int.Cl. ⁶ , DB name) B29C 45/00-45/84 B29C 33/38 G01N 11/00-11/08 G05B 17/00

Claims (5)

(57) [Claims] 1. A method for manufacturing a resin molding die having a plurality of cavities, comprising: inputting resin characteristics, die characteristics, molded product shape, molding conditions, and the like; The resin filling completion time for each cavity is determined by analysis using the shape data as a parameter, and the resin flow path shape in which the resin filling completion time in each cavity is equal is determined. Created, molded using the created test mold, measured the resin filling state in each cavity, calculated the filling ratio of other cavities to specific cavities from the measured resin filling state for each cavity, By fixing the resin flow path shape data for the specific cavity and changing the resin flow path shape data for the other cavities and performing the analysis, a specific key is obtained. The change curve of the filling ratio between the cavity and the other cavity due to the change of the shape data is obtained, and the change curve is corrected with a correction amount derived from the filling ratio based on the actual measurement. A mold manufacturing method, wherein the shape data at the time of 1 is used as the resin flow channel shape data of another cavity, and a die is manufactured with the flow channel shape. 2. A resin filling completion time for each cavity is obtained by analysis using resin characteristics, mold characteristics, molded product shape, molding conditions, and the like as input values, and using the shape data of a resin flow path to the cavities as parameters. 2. The resin flow path shape according to claim 1, wherein the resin flow path shape in which the resin filling completion time in each cavity is equal is determined under the condition of minimizing the molding cycle time. Mold making method. 3. The method according to claim 1, wherein the cavity and the resin flow path are divided into a plurality of symmetric blocks around the sprue, and the analysis and correction are performed on the resin flow path in a single block. Mold making method. 4. When molding is performed using the created test die and the resin filling state in each cavity is measured, it is necessary to measure the resin filling state from a molded article molded by changing the resin filling amount. The method for manufacturing a mold according to claim 1, wherein: 5. The sprue, the main runner, and the gate among the shape data of the resin flow path to the cavity are fixed input values, and the shape data of the sub-runner is a parameter. Mold making method.