JPH08281756A - Operation control method for injection molding machine - Google Patents

Abstract

PURPOSE: To prevent the generation of a defective product accompanied by a change of environment by setting a condition having the intermediate value of the population in a trial molding test of a reference good product molding condition pattern to a molding condition and altering the molding condition when the physical quantity thereof is ready to deviate from a good product molding range so that the physical quantity becomes the center of the good product molding range. CONSTITUTION: An injection process and a dwelling process are separately provided with respect to each of reference good product molding conditions A and a plurality of molding condition patterns B changed in the setting of a screw position, an injection speed, an injection time or dwelling pressure little by little are set before and behind each of the reference good product molding conditions A. Next, a molding test is conducted at every molding condition patterns B and conditions generating good and bad products are classified to establish the popullation of good product molding patterns. The molding conditions of upper and lower limit values are determined from a good product molding condition range on the basis of the data thereof and the intermediate value thereof is selected as the optimum molding condition. The molding condition is altered on the basis of the physical quantity exerting effect on quality among the values measured during molding by various sensors to obtain a good product range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control method for an injection molding machine for molding a plastic product.

[0002]

2. Description of the Related Art Conventionally, in injection molding of molten resin,
The horizontal axis is the position or time of the injection screw, the vertical axis is the forward speed or pressure of the injection screw, and the filling step of filling the molten resin into the mold cavity at high speed, and the filling cavity inside the mold cavity after the molten resin is filled. Injection control is performed by a pressure-holding process that applies pressure to the resin, and in many cases, the filling process sets the pressure adjustment valve of the hydraulic circuit to high pressure, and based on the elapsed time from the start of injection or the forward position of the injection screw. The opening of the flow control valve is set to change over time so as to change the speed in multiple stages, or is set to change according to the stroke position of the injection screw, and by adjusting the flow control valve, the piston of the injection cylinder, that is, The injection speed of the injection screw is controlled to fill the molten resin into the cavity at a high speed so that the resin in the cavity does not entrap air. After the molten resin is filled in the cavity, the flow control valve is fixed to a relatively small opening, and the pressure control valve adjusts the hydraulic pressure to perform a pressure-holding process. The opening of the pressure control valve is changed so that a predetermined pressure can be applied to the filled molten resin, and the molten resin cools in the cavity, causing the resin to shrink, and the shape and dimensions of the product are the dimensions of the cavity shape. The error is prevented from occurring and a large residual stress is not generated inside the product.

In FIG. 10, the molten resin is injected from the screw head front portion 22 of the injection molding machine 20 through the nozzle portion 4 into the mold 1.
It shows a state immediately before injection filling into the cavity 8 formed by 0a and 10b. After that, the injection process is started,
Hydraulic oil enters the injection cylinder 16 from the head side 16a of the injection cylinder 16 and advances the screw 1 to transfer the molten resin of the nozzle portion 4 into the cavity 8. After the cavity 8 is filled with the molten resin, a pressure-holding step is performed, and a pressure is applied to the resin in the front portion 22 of the screw head while supplementing the contraction amount due to the cooling and solidification of the resin. What kind of resin inflow velocity pattern and pressure pattern should be used to inject and fill the molten resin in such an injection process and a pressure-holding process, respectively, depends on the quality of the resin molded product molded in the mold. It depends, and in general, as mentioned above,
For example, in the injection process, as shown in FIG. 13, the screw position and the screw advancing speed are set, and in the pressure holding process, as shown in FIG. 14, the elapsed time and the holding pressure (oil pressure or resin pressure) are set. I am trying to set it in relation to.

In determining such a velocity pattern or pressure pattern, the operator tries to grasp the molding conditions under which a good product can be stably obtained with good reproducibility, and various combinations of various molding conditions are used. I have been trying to get the desired result by trial and error. In addition to these trial-and-error methods, recently, an attempt is being made to grasp desirable molding conditions with a certain degree of accuracy by a simulation method for in-mold flow analysis of resin making full use of computer technology. On the other hand, if the environment (outside air temperature) of the place where the molding is performed with the injection molding machine, the state of the machine (friction coefficient, etc.) or the state of the resin (melt viscosity, etc.) changes, defective products will occur even if molding is performed under the same conditions. Therefore, a quality inspection step for inspecting the molded product after molding is provided to judge whether the quality of the molded product is acceptable or not. When defective products start to appear, the molding is stopped and the molding conditions are set again.

[0005]

However, some non-defective molding conditions obtained from trial and error such as several trial shots are as shown in FIG. 15 and FIG.
It is only one non-defective molding condition pattern within the range sandwiched between the upper and lower limits of the non-defective molding range, and if this non-defective molding condition pattern is close to the upper or lower limit of the non-defective molding condition range. However, if there is any environmental change or disturbance that affects various molding conditions, there is a risk that it will easily deviate from this range and become non-defective molding conditions. The drawback is that the formation of non-defective products as planned is hindered, resulting in the molding of defective products. Also, if there are large changes in the environment or machine conditions or resin conditions, it is inevitable that defective products will occur.Therefore, a quality inspection process is provided after molding to determine whether the quality is acceptable or not, and defective products are subsequently molded. In that case, the molding must be stopped and the conditions must be set again, resulting in a deterioration in productivity and an increase in cost.

[0006]

[Means for Solving the Problems] By solving the above problems, the optimum molding conditions for non-defective molding in actual molding operation are set so that defective products do not appear even if some environmental changes occur,
In addition, in order to automatically correct the molding conditions when the occurrence of defective products is unavoidable due to a large environmental change, in the present invention, a resin material that has fluidity by heating or pressurizing means is substantially sealed. This is an operation control method for an injection molding machine that repeatedly press-molds into a mold cavity to repeatedly produce molded products, and sets the molding conditions for forming a non-defective product in the conditional molding test that is performed prior to the actual molding operation. A plurality of molding condition patterns in which one or more are selected as standard conforming product molding conditions and at least one or more condition setting values are changed for each of the one or more standard conforming product molding conditions. A molding condition pattern that a good product is formed as a result of performing a trial shot molding test on all the created molding condition patterns and judging the quality of the molded product. To form a population consisting of only over emissions,
A molding condition pattern of the upper limit value and a molding condition pattern of the lower limit value is obtained from the population, and the molding condition pattern of the intermediate value of the molding condition pattern of the upper limit value and the lower limit value is used as the molding condition during actual operation. , A plurality of physical quantities related to the test conditions are measured during the trial molding test of the molding condition pattern, and the physical quantity that influences the quality of the quality is selected by collating it with the result of the quality judgment, and the good product of the physical quantity is selected. After setting the molding range and calculating the relationship between the selected physical quantity and the molding condition, when the selected physical quantity is likely to deviate from the non-defective molding range during actual operation, the selected physical quantity Based on the relationship between the molding conditions and the molding conditions, the molding conditions were changed so that the physical quantity was in the center of the good product molding range. Further, in the second invention, instead of the conditional molding test, at least one standard conforming product molding condition is set based on the CAE technique.

[0007]

In the present invention, one or a plurality of molding conditions for forming a good product are grasped by the condition setting performed prior to the actual molding operation or the simulation method by the CAE technique, and this is used as the standard good product molding condition. In addition, based on this, a plurality of molding condition patterns in which the condition setting values are slightly changed are created. And
A quality test is performed by performing a trial molding test for each of them, and the molding condition pattern and the lower limit value that become the upper limit value of the condition setting value from the population that picks up only the molding condition pattern that forms a good product Then, the molding condition pattern is obtained. Then, a molding condition pattern that takes an intermediate value between these two upper limit values and lower limit condition values is used as the molding condition during actual operation. On the other hand, when carrying out the trial molding test with the plurality of molding condition patterns, a plurality of physical quantities are measured, and one or a plurality of physical quantities that affect the quality are selected by collating with the quality judgment result. After determining the non-defective product range value, the relationship between the physical quantity and the molding condition is calculated. If the actual operation is performed under the molding conditions obtained by the above method,
It is unlikely that the product will be defective even if it changes due to environmental changes that occur during actual operation, and if physical quantities that affect quality are monitored, even if the physical changes tend to deviate from the good product range, From the relationship between the physical quantity obtained by the method and the molding condition, if the molding condition is corrected so that the physical quantity is in the center of the non-defective product range, the occurrence of defective products can be prevented.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 11 relate to an embodiment of the present invention, FIG. 1 is an explanatory view of optimum molding conditions in an injection process, FIG. 2 is an explanatory view of optimum molding conditions in a pressure holding process, and FIG. 3 is a molding condition pattern in an injection process. 5 is an explanatory view of setting, FIG. 4 is an explanatory view of molding condition pattern setting in the pressure holding step,
6 is a flow chart showing the setting procedure and control method of the optimum molding conditions, FIGS. 6 to 8 are explanatory diagrams showing the correlation between the measured physical quantity and quality and the good product, and FIGS. 9 to 10 show the correlation between the selected physical quantity and the molding condition. FIG. 11 is an explanatory diagram showing that the molding condition is changed in response to the change in the selected physical quantity.

The object of the present invention is to provide a highly reliable product which is capable of continuously molding a non-defective product without error even if an unexpected environmental change or disturbance that occurs during actual operation is encountered, without fail. It is to grasp the optimum molding conditions and control the operation. Further, even when the environment changes greatly and the occurrence of defective products cannot be avoided, it is necessary to automatically detect it and appropriately correct the molding conditions to continue molding good products. That is, it is intended that the molding rate of non-defective products can be made extremely high, and the molding conditions can be modified according to changes in the environment. The detailed procedure will be described below.

FIG. 5 is a flow chart showing a procedure for setting the optimum molding conditions and automatically correcting the molding conditions in accordance with the environmental change during the actual operating operation. This is referred to as a standard conforming product molding condition) and one or more of them are set. The standard non-defective molding conditions are determined by performing conditional molding tests based on past molding performance data and experience, or by making full use of the CAE technology-based resin flow simulation simulation method. To do.

After the first stage work is completed, each of the plurality of standard conforming product molding conditions is divided into an injection process and a pressure-holding process, with the standard conforming product molding condition as the center, and the screw positions before and after that. A plurality of molding condition patterns are set by gradually changing the condition settings such as injection speed, time, and holding pressure. 3 and 4 show examples of molding condition patterns set in the injection process and the pressure holding process, respectively.

In order to confirm which condition can mold a non-defective product with respect to the plurality of molding condition patterns thus obtained, in the next step, each molding condition pattern is actually A molding test is carried out, and a quality judgment work is carried out to distinguish between conditions under which a good product was molded and conditions under which a defective molded product was produced. As a result of the above, the population of only molding condition patterns that can reliably mold the remaining good products by excluding the molding condition patterns that caused defective products is determined, and the good product molding condition range is determined based on the information of this population,
From the range, the molding conditions having the upper limit and the molding conditions having the lower limit are determined. FIG. 1 and FIG. 2 are actual examples showing a non-defective molding range and its upper limit and lower limit in the injection process and the pressure holding process, respectively.

As described above, since the molding conditions for the non-defective molding range and the upper and lower limits are determined, the optimum molding conditions to be actually adopted are determined. In the present invention, the optimum molding conditions are shown in FIG. The conditions (intermediate value conditions) corresponding to the intermediate values shown in 2 are selected as the optimum molding conditions.

On the other hand, when molding with a plurality of molding condition patterns, a plurality of physical quantities during molding are measured by various sensors, and the quality judgment result is collated with one or a plurality of physical quantities that affect quality. Select and determine the good product range. FIG. 6 is an example in which the physical quantity to be measured is the most advanced position of the screw, and acceptable products and rejected products are formed in each molding condition pattern. Since good products are formed in the range of 10 mm to 20 mm, the most advanced position of the screw is judged to be a physical quantity that affects quality, and the physical quantity is selected as a physical quantity for quality judgment, and the good product range value is from 10 mm. It is determined to be 20 mm. Fig. 7 shows an example in which the physical quantity to be measured is the "resin temperature at the time of completion of filling" and the quality results for each molding condition pattern are collated. However, since this physical quantity has no correlation with the molding quality, it does not affect the molding quality. It is judged not to exist. In addition, FIG. 8 shows an example of the measured physical quantity being the “integral value at the screw position of the resin pressure”. This is selected as the physical quantity that affects the quality of the molded product, and the non-defective product range is 750 to 800 kgf / cm ^2.・ It becomes mm.

Next, a physical quantity that affects the quality of the molded product is selected.
Regarding the selected one, the relationship with the molding conditions is obtained. Figure
In No. 9, the physical quantity is the most advanced position of the screw and the molding condition is the holding pressure.
This is an example of a time integrated value.
Shape condition) 100 kgf / cm²・ If you increase sec
The relationship that the screw most advanced position (physical quantity) is reduced by 5 mm
It has become. Moreover, in FIG.
2 mm / sec), the resin pressure screw
Integrated value (physical quantity) at the position is 20 kgf / cm ²・ Mm
You can see it grows.

As described above, after the optimum molding conditions, the physical quantity that affects the quality and the range of non-defective products, and the relationship between the physical quantity and the molding conditions are obtained by a plurality of molding tests, the actual operation is started. Since the value condition is set to the optimum molding condition, molding can be performed without deviating from the molding range of a good product even with a slight change in environment or unexpected disturbance. Also,
If you monitor physical quantities that affect quality during operation,
As shown in FIG. 11, even if the physical quantity (the screw most advanced position) is likely to deviate upward from the good product molding range due to a large change in environment, the molding condition is corrected (maintained) based on the previously obtained relationship between the physical quantity and the molding condition. By lowering the pressure), the generation of defective products can be avoided, and good products can be continuously molded in conformity with the environment. By molding a molded product by the method of the present invention, the rate of non-defective products is remarkably increased, and since it is possible to adapt to large environmental changes, stable non-defective product molding is possible. Although the present invention is applied to the injection molding machine, it is needless to say that the present invention may be applied to a die casting machine or a squeeze casting machine for molding a metal material.

Conventionally, when a defective product is generated during operation, the operator stops the operation of the machine and is obsessed with grasping the cause and preparing a countermeasure, that is, preparing for new condition setting, which significantly impairs productivity. However, in the present invention, the operation is performed under the molding conditions that are most unlikely to cause defective products, and when a defective product is likely to occur due to a large environmental change, stable molding conditions are automatically corrected, and The continuous production of non-defective products can greatly reduce the production cost.

[0018]

As described above, according to the operation control method for the injection molding machine of the present invention, the molding can be performed under the most stable molding conditions and can be adapted to the changes in the environment, so that the productivity is improved. The quality inspection process after molding can also be deleted.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of optimum molding conditions in an injection process according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of optimum molding conditions in a pressure holding step according to an example of the present invention.

FIG. 3 is an explanatory diagram of molding condition pattern setting in an injection process according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of molding condition pattern setting in the pressure holding step according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a setting procedure and a control method of optimum molding conditions according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a correlation between a measured physical quantity and a non-defective product range according to an example of the present invention.

FIG. 7 is an explanatory diagram showing the correlation between the measured physical quantity and the quality of the molded product according to the example of the present invention.

FIG. 8 is an explanatory diagram showing a correlation between a measured physical quantity and a non-defective product range according to an example of the present invention.

FIG. 9 is an explanatory diagram showing a correlation between selected physical quantities and molding conditions according to the embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a correlation between a selected physical quantity and molding conditions according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a change in the actual operation of the selected physical quantity according to the embodiment of the present invention and the corresponding change of the molding condition.

FIG. 12 is an overall configuration diagram of a conventional injection molding machine.

FIG. 13 is an example of molding conditions in a conventional injection process.

FIG. 14 is an example of molding conditions in a conventional pressure-holding process.

FIG. 15 is an explanatory diagram of molding conditions in a conventional injection process.

FIG. 16 is an explanatory diagram of molding conditions in a conventional pressure holding step.

[Explanation of symbols]

 1 screw 2 check valve 3 barrel 4 nozzle 8 cavity 10a fixed mold 10b movable mold 12 hopper 14 piston 16 injection cylinder 16a head side 18 screw head 20 injection molding machine 22 screw head front A standard good product molding condition B molding condition pattern L Lower limit condition S Good product forming range T Optimal forming condition U Upper limit condition

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Paper 1980, Okiyama, Ogushi, Ube, Yamaguchi Prefecture Ube Machinery Co., Ltd.

Claims (2)

[Claims] 1. An operation control method for an injection molding machine, wherein a resin material fluidized by heating or pressurizing means is flow-pressed into a substantially closed mold cavity to repeatedly produce a molded product, which comprises: One or more molding conditions for forming a non-defective product are selected as standard non-defective product molding conditions from the conditional molding test performed prior to the actual molding operation, and one or more standard non-defective product moldings are performed. Create a plurality of molding condition patterns in which at least one condition setting value is changed for each condition,
A molding test is performed on all the created molding condition patterns to determine the quality of the molded product. As a result, a good product is formed. A population consisting of only the molding condition patterns is formed, and the upper limit is selected from the population. The molding condition pattern of the value and the molding condition pattern of the lower limit value is obtained, and the molding condition pattern of the intermediate value of the molding condition pattern of the upper limit value and the lower limit value is used as the molding condition during the actual operation, and the molding condition pattern is tested. A plurality of physical quantities related to the test conditions are measured during the punching molding test, and the physical quantity that affects the quality of the quality by comparing with the result of the quality judgment is selected and the molding range of the good quantity of the physical quantity is set. After calculating the relationship between the selected physical quantity and the molding conditions, when the selected physical quantity is about to deviate from the non-defective molding range during actual operation, the -Option physical quantity and the operation control method of an injection molding machine to which the physical quantity from the relation between the molding conditions and changing the molding conditions such as the center of non-defective molded range. 2. The operation control method for an injection molding machine according to claim 1, wherein at least one reference non-defective molding condition is set based on the CAE technique instead of the conditional molding test.