JPH0976320A - Automatic setting method for injection molding speed condition of injection mold machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To previously analyze a resin pressure in a mold cavity by flow analysis of a melt resin by a form model of a molding without providing a resin pressure sensor in a mold and computing and correcting an injection speed so as to eliminate a difference between the resin pressure and a previously set pressure. SOLUTION: In an injection mold machine which molds a desired molding by injecting a melting material into a mold cavity 20 by movement of a screw 12, a reference pressure of the melting material to be injected into the cavity is set as a function of an elapsed time from start of injection process or the moved distance of the screw. A form model of a molding is previously divided into elements, and flow analysis of the melting material is performed by a finite element method and a boundary element method so as to analyze the resin pressure in the cavity. Within a range where the resin pressure differs from the reference pressure, from the relationship between the calculated pressure and the reference pressure, the resin pressure in the mold cavity is obtained by computing a correction value of the injection speed so as to eliminate the difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of automatically setting an injection molding speed condition of an injection molding machine.

[0002]

2. Description of the Related Art In a filling process of an injection molding machine, a control method has been proposed for improving the quality of a molded product by feeding back the detected resin pressure in a mold to a preset pressure to control the injection speed. There is.

FIG. 11 shows a schematic construction of an injection molding speed control device of an injection molding machine which carries out such a conventional control method. That is, in FIG. 11, reference numeral 10 is an injection cylinder, 12 is a screw, 14 is a barrel,
16 is a nozzle, 18 is a gate, 20 is a mold cavity,
22 is a hydraulic unit provided for the injection cylinder 10 for controlling the injection speed of the screw 12, 24 is a screw position detector for detecting the moving position of the screw 12, and 26 is the hydraulic unit 22. And a control device 28 for controlling the mold cavity 2
The resin pressure sensor for detecting the resin pressure within 0 is shown respectively.

In the injection molding speed controller thus constructed, the pressure of the molten resin (resin pressure) in the mold cavity 20 is detected by the resin pressure sensor 28, and this detected pressure is fed back to the controller 26. , The injection speed of the screw 12 is controlled. In this case, when the resin pressure in the mold cavity 20 detected by the resin pressure sensor 28 is higher than the pressure set in advance during the filling process, the filling speed is automatically reduced by a predetermined calculation, and An automatic deceleration control of the filling speed that controls an excessive increase in resin pressure is achieved. The molding method of the injection molding machine using such an injection molding speed control device is effective in reducing the size of the mold, reducing the weight of the molding machine, reducing the size of the molding machine, and improving the quality of the molded product.

[0005]

However, in the above-mentioned injection molding speed control device, when performing automatic deceleration control of the filling speed by feedback of the resin pressure in the mold cavity, the resin pressure in the mold cavity is detected. Therefore, it is necessary to attach a resin pressure sensor to the mold.

Therefore, it is not only costly to perform processing for attaching the resin pressure sensor to all the target molds for performing such automatic deceleration control, but also the shape of the molded product and There is a problem that the resin pressure sensor cannot be provided at a desired position depending on the shape of the mold. In addition, it is often difficult to process a part of an existing mold to mount the resin pressure sensor.

Further, also in the setup work for exchanging the mold, it is necessary to attach and detach the resin pressure sensor and its wiring every time the mold is attached to and detached from the injection molding machine, which is a complicated work and the working time is increased. There is a difficulty to do.

Therefore, an object of the present invention is to analyze the resin pressure in the mold cavity in advance by analyzing the flow of the molten resin according to the shape model of the molded product without providing a resin pressure sensor on the mold. An object of the present invention is to provide an injection molding speed condition automatic setting method for an injection molding machine, which can calculate and correct an injection speed so as to eliminate a difference between a pressure and a preset pressure.

[0009]

In order to achieve the above object, the method for automatically setting the injection molding speed condition of an injection molding machine according to the present invention is performed by injecting a molten material into a mold cavity by moving a screw. In an injection molding machine for molding a molded product, the reference pressure of the molten material injected into the cavity is set as a function of the elapsed time from the start of the injection process or the moving distance of the screw, and the shape model of the molded product is set in advance as an element. Divide and analyze the flow of the molten material by the finite element method, boundary element method, etc., analyze the resin pressure in the cavity, and calculate the calculated pressure and the reference pressure in the range where the resin pressure exceeds the reference pressure. It is characterized in that the correction value of the injection speed is calculated and obtained so as to eliminate the difference from the relationship of.

In this case, an injection molding speed condition corresponding to a plurality of resin temperatures, which is set by the above-mentioned automatic setting method of the injection molding speed condition of the injection molding machine, is prepared, and the resin temperature at the time of molding is adjusted. The injection molding speed conditions can be switched and used.

Further, the injection molding speed conditions corresponding to a plurality of resin viscosities, which are set by the above-mentioned automatic setting method of the injection molding speed condition of the injection molding machine, are prepared, and the injection molding is performed according to the resin viscosities at the time of molding. The speed condition can be switched and used.

Furthermore, by giving the flow analysis result of the molded product as input data in the initial condition setting routine of the control program of the injection molding machine, the injection molding speed condition automatic setting method of the injection molding machine described above is set. It is also possible to provide a subroutine for setting the injection molding speed condition to automatically set the injection molding speed condition from the flow analysis result of the molded product.

Furthermore, by giving the flow analysis result of the molded product as input data in the initial condition setting routine of the control program of the injection molding machine and detecting the resin temperature at the time of molding, the above-mentioned injection molding is performed. It is also possible to provide a subroutine to set the injection molding speed condition set by the automatic injection molding speed condition setting method of the machine and automatically set the injection molding speed condition from the flow analysis result of the molded product and the resin temperature during molding. Is.

Then, the flow analysis result of the molded product is given as the input data in the initial condition setting routine of the control program of the injection molding machine, and the resin viscosity at the time of molding is detected, thereby making the injection molding machine described above. It is also possible to provide a subroutine to set the injection molding speed condition set by the method for automatically setting the injection molding speed condition, and to automatically set the injection molding speed condition from the flow analysis result of the molded product and the resin viscosity at the time of molding. is there.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of an automatic method for setting an injection molding speed condition of an injection molding machine according to the present invention will be described in detail below with reference to the accompanying drawings.

That is, in the present invention, when setting the injection molding speed condition, the reference pressure of the molten material injected into the injection mold is set as a function of the elapsed time from the start of the injection process or the moving distance of the screw. At the same time, a flow analysis is performed in advance using the shape model of the molded product including the sprue and runner, and from the analysis result of the resin pressure in the mold, in the range where there is a difference from the reference pressure, the calculated pressure and the reference pressure are calculated by the fluid dynamic theory. The injection molding speed condition is automatically set by calculating the correction value of the injection speed so as to eliminate the difference between

In the injection molding of resin material,
When performing a flow analysis (simulation) of the molten resin in the mold cavity, divide the shape model of the molded product into minute elements and use the numerical analysis methods such as the finite element method, the boundary element method, the difference method, and the FAN method. Therefore, a method of calculating a fluid motion equation, a continuity equation, an energy equation, and the like is generally used.

In such a method for analyzing the flow of the molten resin in the mold cavity, the resin temperature, the mold temperature and the filling speed are input and calculated as the selection of the resin to be used and the operating conditions of the molding machine. , Resin filling progress (time)
As shown, the total filling time is divided into an arbitrary number, the isochronous diagram created by connecting the arrival positions of the resin to be filled at each time with a line, the equal pressure diagram created for the pressure, Similarly, it is well known that the isothermal lines and the like created with respect to the temperature can be obtained by required calculations, respectively (Japanese Patent Publication No. 4-69851).

[0019]

EXAMPLE 1 (A) mold resin pressure Figure 1 by flow analysis of the molten resin, the stroke of the screw 12 in the barrel 14 at a required molded article of the injection process (injection process step),
4 shows the relationship of the progress of the filling of the molten resin in the mold cavity 20 (filling progress step). The present embodiment can be implemented by applying the above-mentioned injection molding speed control device shown in FIG. 11, and therefore, in FIG. 1, the same components as the above-described device configuration shown in FIG. Are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this case, the resin pressure in the mold cavity 20 (hereinafter, abbreviated as in-mold resin pressure) obtained by the flow analysis of the molded product by the mold cavity 20 and the mold at the observation reference point A and thereafter. The relationship between the internal resin pressure and the stroke of the screw 12 is as shown in FIG. 2, for example.

(B) Melt injected into the mold cavity
Reference Pressure of Material In FIG. 2, the resin pressure in the mold rises from the time when the molten resin reaches the observation reference point A of the resin pressure in the mold, and shows a state in which it increases with the progress of filling. Therefore, if the resin pressure in the mold rises excessively, the mold clamping force of the mold will be insufficient,
There are problems such as burrs on the molded product, damage to the core, and deformation of the molded product due to residual stress. For example, in the case shown in FIG. 2, the resin pressure inside the mold for preventing the above-mentioned defects from occurring in the molded product, that is, the reference pressure is 13 MPa at the reference point A.
When set to, the resin pressure in the mold in the 6 to 10 section close to the completion of filling exceeds the reference pressure (13 Mpa).

(C) Relationship between in-mold resin pressure and injection speed As shown in FIG. 1, the stroke of the screw 12 in the injection process is divided into a required number of sections, and the injection speed in each section is constant. Shall be set. That is, an example of setting the stepwise injection speed in this case is shown in FIG.
Shown in

Generally, the viscosity characteristics of a molten resin when flowing are
It exhibits so-called non-Newtonian characteristics, and the relationship between its shear stress and shear rate can be approximated by the following equation (1).

[0024]

[Equation 1] However, τ: Shear stress due to the flow of molten resin φ (dv / dy, T): A constant indicating the viscosity characteristic of the resin (dv / dy): Shear rate T: Resin temperature Here, in the range of normal molding conditions. , Φ can be approximated by the following equation (2).

[0025]

[Equation 2] However, A: viscosity coefficient B: shear coefficient C: temperature coefficient Substituting equation (1) into equation (2), the following equation (3) is obtained.

[0026]

(Equation 3) Here, when the change of the resin temperature T in the mold during a certain filling step can be ignored and the variation of the resin temperature in the repeated molding cycle can be ignored, the above equation (3) is expressed by the following equation (4) ) Can be represented.

[0027]

(Equation 4) However, n and φ are constants indicating the viscosity characteristics of the resin. Therefore, the flow of the molten resin in the mold cavity is
Assuming a Hele-Shaw flow, the molten resin having this viscosity characteristic is filled with the molten resin in the mold cavity in the q-th section as shown in FIG. The flow velocity distribution in the flow direction cross section of the molten resin at this time is as shown in FIG. 5, and the flow velocity distribution v and the section pressure loss ΔP are respectively expressed by the following equations.

[0028]

(Equation 5)

[0029]

(Equation 6)

[0030]

(Equation 7) However, v: flow velocity at position y h: cavity thickness y: distance from center in cavity thickness direction ΔP: section pressure loss L: flow direction distance in section v ₀ : maximum flow velocity (at center in cavity thickness direction) Flow velocity) va: Average flow velocity From the equations (6) and (7), the following equation is obtained.

[0031]

(Equation 8) That is, when focusing on the required section i in the molding of the required molded product, the section pressure loss ΔP _i is proportional to the (1 / n) th power of the average flow velocity va _{i in} that section, as shown in the following equation (6). To do.

[0032]

[Equation 9] Further, the in-mold resin pressure P _q when the molten resin is filled in the q-th section at the reference point A in the p-th section in the mold cavity is
As shown in the following equation (10), it is the sum of the section pressure losses from the p-th section to the q-th section.

[0033]

(Equation 10) Furthermore, it is considered that the injection speed Q _q at the time of filling the molten resin in the q-th section and the average flow velocity va _{i in} each section are proportional to each other as shown in the following equation (11).

[0034]

[Equation 11] Therefore, the in-mold resin pressure P at the time of filling the molten resin in the q-th section at the reference point A in the p-th section in the mold cavity
_q, as shown by the following equation (12) and (13), is proportional to (1 / n) square of injection speed Q _q in filling of the molten resin of the q segment.

[0035]

(Equation 12) (D) Calculation of the correction value of the injection speed In consideration of the resin pressure in the mold, the above-mentioned calculated pressure Pc
_Assuming that the corrected injection speed in the range where _q is different from the reference pressure Ps _{q at} the reference point A is Q ′ _q , the above equation (13)
Therefore, the relation of the following equation is established.

[0036]

(Equation 13)

[0037]

[Equation 14]

[0038]

(Equation 15) Therefore, the equation (16) As is apparent from the Q _'q modified injection speed, the original injection speed Q _q, with respect to the ratio of the reference pressure Ps _q and calculates pressure Pc _q, which n th power You can ask for it.

That is, if Ps _q / Pc _q is less than 1, deceleration is corrected toward the reference pressure (resin pressure inside the mold) that does not cause a defect in the molded product, and conversely Ps _q / P
If c _q exceeds 1, the speed is corrected toward the reference pressure (the proper in-mold resin pressure lower than the limit in-mold resin pressure) in order to eliminate problems such as short shots due to insufficient in-mold resin pressure. .

(E) Calculation Example of Correction Value of Injection Speed Table 1 shows the conditions for flow analysis and injection speed correction calculation for a required molded product. Table 2 shows the results of the flow analysis and the correction calculation of the injection speed under the conditions shown in Table 1.

[0041]

[Table 1]

[0042]

[Table 2]

(F) Confirmation of Effect by Molding Test FIG. 6 shows the measurement results of the resin pressure in the mold at the reference point A when molding was carried out at the initial injection speed and the modified injection speed shown in Table 2 above. . In this case, at the initial injection speed, the reference pressure exceeds 13 Mpa after the 6th section of filling, but at the corrected injection speed, it is almost within the range of the reference pressure, and the method according to the present invention is effective. You can confirm that there is.

[0044]

Example 2 In a repeated molding cycle, when the temperature of the injected molten resin fluctuates, ex of the formula (3)
The value of p (CT) changes, the resin viscosity changes, and even under the same injection speed condition, the in-mold resin pressure at the reference point in the mold cavity has different values. Therefore, in this case, the injection molding speed conditions for various resin temperatures are obtained in advance by the methods shown in (A) to (F) of Example 1, and the injection is appropriately performed according to the resin temperature during molding. Molding can be performed by switching and setting the molding speed conditions.

In this case, for example, a resin temperature sensor may be provided in the nozzle portion, or a barrel temperature sensor may be used to obtain the relationship between the detected temperature of the barrel and the resin temperature during molding in advance. The resin temperature during molding can be easily detected.

[0046]

Example 3 In addition, due to variations in the quality of the raw resin,
In the repeated molding cycle, when the viscosity of the molten resin changes, the viscosity coefficient A of the above formula (3) changes and the resin viscosity also changes, and even under the same injection speed condition, the mold of the reference point in the mold cavity is changed. The internal resin pressure has different values.
Therefore, in this case, (A) to
By the method shown in (F), the resin pressure of the nozzle portion corresponding to various resin viscosities is obtained in advance, and the injection molding speed condition is appropriately switched and set according to the resin pressure of the nozzle portion at the time of molding, and molding is performed. be able to.

In this case, for example, by providing a resin pressure sensor in the nozzle portion, or by utilizing the screw driving oil pressure, the relationship between the screw driving oil pressure at injection and the resin pressure in the nozzle portion is obtained in advance. The resin pressure at the time of molding can be easily detected.

[0048]

[Fourth Embodiment] Further, from the flow analysis result given as input data in the initial condition setting routine of the control program of the control device of the injection molding machine, the results are shown in (A) to (F) in the first embodiment. By providing a subroutine for obtaining the injection molding speed condition according to the method, it is possible to provide the control device of the injection molding machine with a function of automatically setting the injection molding speed condition from the flow analysis result of the molten resin.

In this case, the function shown in the second and third embodiments can be further added.

[0050]

[Embodiment 5] The effect of suppressing the resin pressure in the mold under the injection speed conditions obtained in (A) to (D) in Embodiment 1 was subjected to a flow analysis on a required molded product and confirmed by a test using an actual machine.

(G) Conditions for Flow Analysis and Actual Machine Test Table 3 shows conditions for flow analysis and actual machine test. In addition,
As a molded product, a flat plate composed of the analytical model shown in FIG. 7 was used.

[0052]

[Table 3]

(H) Analytical result and effect of suppressing resin pressure in the mold As a result of injection molding under the injection speed condition according to the present invention based on the conditions shown in Table 3, as shown in FIGS. 8 to 10, as expected, It was possible to obtain the effect of suppressing the resin pressure in the mold. In the analysis, the resin pressure was adjusted by correcting the constant term of the resin viscosity data from the actual machine test result.

That is, the viscosity constant n of the resin used in the test is n = 2.74, but when n = 4 to 5 (see FIG. 10), the accuracy of suppressing the resin pressure in the mold is higher. It was confirmed that it could be improved. This is in the above formula (16),
It is considered that, while the change in the viscosity of the molten resin is ignored, the filling time is extended and the viscosity is increased due to the deceleration.

When the injection speed condition determined by the viscosity constant n = 2.74 is given and the same procedure is repeated again, as shown in FIG. Through the analysis, it was possible to obtain injection speed conditions that were within the target mold resin pressure.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the spirit of the present invention.

[0057]

As is apparent from the above-described embodiments, according to the method for automatically setting the injection molding speed condition of the injection molding machine according to the present invention, sprue can be preliminarily set without providing the resin pressure sensor on the mold. Analyze the resin pressure in the mold cavity by the flow analysis of the molten resin using the shape model of the molded product including the runner, and calculate and correct the injection speed so as to eliminate the difference between this resin pressure and the preset pressure. As a result, it is possible to easily achieve a reduction in mold size, a reduction in weight, a downsizing of a molding machine, an improvement in quality of a molded product, and the like.

Therefore, according to the present invention, it is possible to save the labor and cost for the processing for attaching the resin pressure sensor to the mold, and the setup work for the mold replacement is not complicated. , Has the advantage that it can be achieved simply and quickly.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an injection molding machine showing a relationship between a screw and a mold cavity for carrying out an injection molding speed condition automatic setting method for an injection molding machine according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a resin pressure and a screw stroke at a reference point in the mold cavity shown in FIG.

FIG. 3 is a characteristic diagram showing a relationship between a screw position and an injection speed, which shows an example of setting an injection speed by the screw shown in FIG.

FIG. 4 is an explanatory diagram showing a state where the molten resin is being filled in the mold cavity shown in FIG. 1.

5 is an explanatory view showing a flow velocity distribution and a section pressure loss in a cross section in the flow direction of the molten resin in the mold cavity shown in FIG.

6 is a pressure characteristic diagram showing a measurement result of resin pressure at a reference point in a mold cavity when molding is performed at an initial injection speed and a modified injection speed in the injection molding machine shown in FIG.

FIG. 7 is an explanatory diagram showing an example of a flow analysis model.

8 is a pressure characteristic diagram showing an analysis calculation result of a resin pressure in relation to a filling rate at the time of injection molding in a mold cavity made of the flow analysis model shown in FIG.

9 is a pressure characteristic diagram showing the measurement result of resin pressure in relation to the filling time at the time of injection molding by the method of the present invention in the mold cavity made of the flow analysis model shown in FIG. 7.

FIG. 10 is a pressure characteristic diagram showing the same resin pressure measurement results as shown in FIG. 9 when the resin viscosity condition is changed.

FIG. 11 is a schematic explanatory diagram of an injection molding machine that performs automatic pressure reduction control of a filling speed by feedback of resin pressure in a mold cavity.

[Explanation of symbols]

 10 Injection Cylinder 12 Screw 14 Barrel 16 Nozzle 18 Gate 20 Mold Cavity 22 Hydraulic Unit 24 Screw Position Detector 26 Control Device 28 Resin Pressure Sensor

Claims (6)

[Claims] 1. In an injection molding machine for injecting a molten material into a mold cavity by moving a screw to form a desired molded article, a reference pressure of the molten material injected into the cavity is set from the start of the injection process. In addition to setting as a function of elapsed time or screw movement distance, the shape model of the molded product is divided into elements in advance, and the flow analysis of the molten material is performed by the finite element method, boundary element method, etc. to determine the resin pressure in the cavity. The injection molding machine is characterized by analyzing and calculating a correction value of the injection speed so as to eliminate the difference between the calculated pressure and the reference pressure in the range where the resin pressure exceeds the reference pressure. Injection molding speed condition automatic setting method. 2. An injection molding speed condition set by the method for automatically setting an injection molding speed condition of an injection molding machine according to claim 1, which corresponds to a plurality of resin temperatures, is prepared, and the temperature is adjusted according to the resin temperature at the time of molding. A method for automatically setting an injection molding speed condition of an injection molding machine, characterized in that the injection molding speed condition is switched and used. 3. An injection molding speed condition, which is set by the method for automatically setting an injection molding speed condition of an injection molding machine according to claim 1, corresponding to a plurality of resin viscosities is prepared, and the resin viscosity at the time of molding is adjusted. A method for automatically setting an injection molding speed condition of an injection molding machine, characterized in that the injection molding speed condition is switched and used. 4. The automatic injection molding speed condition setting method for an injection molding machine according to claim 1, wherein a flow analysis result of a molded product is given as input data to an initial condition setting routine of a control program of the injection molding machine. A method for automatically setting an injection molding speed condition for an injection molding machine, characterized in that a subroutine for setting an injection molding speed condition set in 1. is provided to automatically set an injection molding speed condition from a flow analysis result of the molded product. 5. The method according to claim 2, wherein the flow condition analysis result of the molded product is given as input data to the initial condition setting routine of the control program of the injection molding machine, and the resin temperature at the time of molding is detected. A subroutine for setting the injection molding speed condition set by the injection molding speed automatic setting method of the injection molding machine is provided to automatically set the injection molding speed condition from the flow analysis result of the molded product and the resin temperature at the time of molding. A method for automatically setting an injection molding speed condition of an injection molding machine, characterized by: 6. The method according to claim 3, wherein the flow analysis result of the molded product is given as input data to the initial condition setting routine of the control program of the injection molding machine, and the resin viscosity at the time of molding is detected. A subroutine for setting the injection molding speed condition set by the injection molding speed automatic setting method of the injection molding machine is provided to automatically set the injection molding speed condition from the flow analysis result of the molded product and the resin viscosity at the time of molding. A method for automatically setting an injection molding speed condition of an injection molding machine, characterized by: