JPH08258105A - Molding quality discriminating method for injection molding machine - Google Patents

Abstract

PURPOSE: To provide a method for discriminating the molding quality of an injection molding machine in which a defective product generated due to the certain disturbance during operation is automatically discovered and excluded from the products. CONSTITUTION: The method for discriminating the molding quality of an injection molding machine comprises the steps of selecting molding conditions for forming a non-defective product by a condition generating molding test as a reference non-defective product molding condition, forming a plurality of molding condition patterns in which at least one condition set values are varied in each pattern, and forming a population made only the molding condition pattern for forming a non-defective product as the result of discriminating the quality of the molding by executing a trial test for the patterns. The method further comprises the steps of obtaining the molding condition patterns of the upper and lower limit values from it, setting the intermediate value of the upper and lower limit values as the molding conditions at the time of real operation, selecting a physical amount for exerting influence on the propriety of the quality from a plurality of physical amounts at the trial molding test, setting the non-defective product molding range, and then regarding the molding at the time when the physical amount exceeds the non-defective product molding range at the time of the real operation as the defective product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product quality judgment 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. 11, the screw position and the screw advancing speed are set, and in the pressure holding process, as shown in FIG. 12, 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 of the injection molding machine changes, or if disturbance is applied during operation, the quality of the molded product may change and defective products may be generated. Therefore, inspect the molded product after molding. A quality inspection process was provided to determine whether the quality of the molded product was acceptable.

[0005]

However, some of the good product molding conditions obtained from trial and error such as several times of trial hitting are, for example, as shown in FIG. 13 and FIG. It is only one non-defective molding pattern in the range sandwiched between the upper and lower limits, and if this non-defective molding pattern is close to the upper or lower limit of the range of non-defective molding conditions. If there is any environmental change or disturbance that affects various molding conditions, there is a possibility that it will easily deviate from this range and it will not be a good product molding condition.In such a case, formation of a good product as planned However, there is a problem in that the product is impeded, resulting in the molding of a defective product. In addition, a quality inspection process must be provided after molding so as to prevent defective products from being mixed in the shipped products, resulting in deterioration of productivity and increase in cost.

[0006]

[Means for Solving the Problems] By solving the above problems, optimum molding conditions for molding good products in actual molding operation are set so that defective products do not appear even if some disturbance occurs, and In order to determine product quality, in the present invention, molding of an injection molding machine for repeatedly producing molded products by fluid-pressing a resin material having fluidity by heating or pressurizing means into a substantially closed mold cavity A method for determining product quality, in which one or more molding conditions for forming a non-defective product are selected as a reference non-defective product molding condition by a conditional molding test that is performed prior to the actual molding operation. Alternatively, a plurality of molding condition patterns in which at least one condition setting value is changed for each of a plurality of standard conforming molding conditions are created, and all the created molding condition patterns are created. A molding group consisting of only molding condition patterns is formed in which a good product is formed as a result of the quality test of the molded product by performing a trial molding test, and the molding condition pattern of the upper limit value and the lower limit value are formed from the population. Of the molding condition pattern of the upper limit value and the lower limit value, and the molding condition pattern of the intermediate value of the molding condition pattern of the upper limit value and the lower limit value as the molding condition during the actual operation, and the test condition at the time of the trial molding test of the molding condition pattern. After measuring a plurality of physical quantities relating to the above, selecting a physical quantity that influences the quality of the quality by collating it with the quality judgment result, and setting a non-defective molding range of the physical quantity, and then selecting the actual quantity during the actual operation. A molded product in a shot in which a physical quantity deviates from the molding range of the good product is regarded as a defective molded product. 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
For each of them, a trial molding test is performed to determine the quality, and from among the population that picks up only the molding condition patterns that form good products, the molding condition pattern and the lower limit value that are the upper limit of the condition setting value A molding condition pattern that satisfies 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. , The value range of the non-defective product is determined. If the actual operation is carried out under the molding conditions obtained by the above method, it will not be a defective product even if the environmental changes mixed up during the actual operation make it difficult to monitor the physical quantity that affects the quality. Even if such disturbances occur and the occurrence of defective products cannot be avoided, the quality is automatically judged and defective products are excluded from the good products.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 9 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, and FIG.
6 is a flowchart showing a procedure for setting optimum molding conditions, FIG.
8 is an explanatory diagram showing the correlation between the measured physical quantity, quality and the non-defective product range, and FIG. 9 is an explanatory diagram showing the correlation between the non-defective product range of the selected physical quantity and the quality of the molded product.

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. Understanding the optimum molding conditions.
Further, even when it is unavoidable that a defective product is formed due to a sudden disturbance, it can be automatically judged as a rejected product and eliminated. That is, it is intended that the molding rate of non-defective products can be made extremely high and the quality judgment can be automatically performed. The detailed procedure will be described below.

FIG. 5 is a flow chart showing a procedure for automatically determining rejected products during actual operation by setting optimum molding conditions. Molding conditions for forming a good product first before the actual operation (this is a standard conforming product). One or more molding conditions are set. The standard non-defective molding conditions are determined by performing conditional molding based on past molding performance data and experience, or by making full use of a flow analysis simulation method of resin flow in a mold to which CAE technology is applied.
After finishing the work of the first stage, each of the plurality of standard conforming product molding conditions is divided into an injection process and a pressure-holding process, and the standard conforming product molding condition is centered around the screw position and the injection speed. , A plurality of molding condition patterns in which condition settings such as time, holding pressure, etc. are gradually changed are set. 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 among 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 limit value and the lower limit value are determined, the optimum molding conditions to be actually adopted are determined. In the present invention, the optimum molding conditions are shown in FIGS. 1 and 2. The conditions corresponding to the intermediate values (intermediate value conditions) 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 results are collated to select one or a plurality of physical quantities that affect quality. Then, determine the range of non-defective products.
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 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. 20 mm
Is determined. 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 pattern are compared, but this physical quantity has no correlation with the molding quality, so it does not affect the molding quality. Judged as something. Further, FIG. 8 shows an example of the measured physical quantity being the “integral value at the screw position of the resin pressure”, but 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 k.
It becomes gf / cm ² · mm.

As described above, after the optimum molding conditions, the physical quantity that influences the quality and the non-defective product range are obtained by a plurality of molding tests, the actual operation is started, but the intermediate value condition is set as the optimum molding condition. However, it is possible to perform molding without deviating from the molding range of non-defective products against environmental changes and unexpected disturbances, and as shown in FIG. 9, the physical quantity affecting quality is constantly monitored. Even if a defective product is generated due to a sudden disturbance that cannot be avoided, the defective product generation state can be detected and rejected as a rejected product. By molding the molded product by the method of the present invention, the non-defective product rate is remarkably increased, and the defective product can be excluded without providing the quality inspection process. 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 a new condition setting, which significantly impairs the productivity. However, in the present invention, the operation is continued under the molding condition that is most unlikely to cause defective products, and such troubles are rarely involved. Further, since the state (physical quantity) during molding is constantly monitored, even if a defective product occurs due to a sudden disturbance, it can be automatically judged and excluded. Therefore, the quality inspection process after molding is unnecessary, and the production cost can be greatly reduced.

[0015]

As described above, according to the method for judging the quality of a molded product of an injection molding machine of the present invention, the number of defective products is minimized, and a good product can be continuously produced continuously in a stable manner. Even if a defective product is generated, it is automatically judged and excluded, so that productivity is improved, maintenance property and driving operability are significantly improved, and the quality inspection step after molding can be eliminated.

[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 procedure for setting 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 the correlation between the non-defective product range of the selected physical quantity and the quality of the molded product according to the embodiment of the present invention.

FIG. 10 is an overall configuration diagram of a conventional injection molding machine.

FIG. 11 is an example of molding conditions in a conventional injection process.

FIG. 12 is an example of molding conditions in a conventional pressure-holding process.

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

FIG. 14 is an explanatory diagram of molding conditions in a conventional pressure holding process.

[Explanation of symbols]

 1 screw 2 check valve 3 barrel 4 nozzle (nozzle part) 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 conditions B Molding condition pattern L Lower limit condition S Non-defective molding range T Optimal molding condition U Upper limit condition

Front page continued (72) Inventor Masahiro Ushi Machine Works, Ube Machinery Co., Ltd.

Claims (2)

[Claims] 1. A method for determining the quality of a molded product of 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. By selecting one or more molding conditions for forming a non-defective product by a conditional molding test that is carried out in advance prior to the actual molding operation, and setting the standard non-defective product molding condition, the one or more standard non-defective product molding Create a plurality of molding condition patterns in which at least one condition setting value is changed for each condition, and perform a trial punch molding test for all the created molding condition patterns to judge the quality of the molded product. As a result, a population consisting of only the molding condition patterns in which non-defective products are formed is formed. A turn is obtained, and a molding condition pattern of an intermediate value of the molding condition patterns of the upper limit value and the lower limit value is used as a molding condition during actual operation, and a plurality of test conditions relating to the test-forming molding test of the molding condition pattern are performed. After measuring the physical quantity of each piece, selecting the physical quantity that influences the quality of the quality by collating it with the quality judgment result, and setting the non-defective molding range of the physical quantity, and then selecting the physical quantity during actual operation. A method for determining the quality of a molded product in an injection molding machine, in which a molded product in a shot that deviates from the good product molding range is regarded as a defective molded product. 2. The molded product quality judgment method for an injection molding machine according to claim 1, wherein at least one standard conforming product molding condition is set based on the CAE technique instead of the conditional molding test.