JPS6114926A - Discrimination between non-deffective and defective of molded part - Google Patents

Abstract

PURPOSE:To accurately discriminate between the non-defective and defective of molded part by a method wherein the value of gap ideal for obtaining non-defective part is set in advance and a certain range is given to the time required to reach said value of gap. CONSTITUTION:A gap measuring device 7 is attached between a fixed mold mounting platen 1 and a fixed mold 2 in order to measure the gap responding to mold clamping force. Being the ideal value of gap denoted by G, the times to reach G are different from one another at every shot. Further, the lower limit value of said times to reach G for obtaining the non-defective is denoted by t1 and its upper limit value by t2. When the set value of gap G is reached within the range t1-t2 at a shot, the shot produces a non-defective part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The industrial field of application of the present invention is the field of injection molding devices such as injection molding machines and die casting machines.

[Prior art] Injection molding equipment abuts a fixed mold and a movable mold, injects molten resin or metal at a predetermined pressure into a cavity formed on the abutting surfaces of both molds, and molds the mold according to the shape of the cavity. This is a device that molds products.

In such injection molding equipment, the quality required for molded products has gradually become more precise, and more and more molded products are required to have submicron dimensional accuracy, surface roughness, or optical homogeneity.

On the other hand, although the performance of injection molding equipment has improved in terms of the sophistication and precision of the injection control system, it has not fully achieved its purpose in molding high-quality molded products as mentioned above. However, the current situation is that there still occurs a considerable number of defective molded products.

In order to determine whether a high-quality molded product is good or bad, not only is a sophisticated inspection measuring instrument required, but also a large number of man-hours are required for inspection.

Therefore, methods for determining the quality of various molded products have been proposed.

One of them is a method of determining the quality of a molded product by measuring the factors that cause variations in molding conditions during molding and viewing the measured data.

For example, the measured values of fluctuation factors such as cushion stroke, molten material temperature, injection speed, and injection pressure are compared with the standard upper limit value and adjustment value, and if it is within the standard value range, it is a good product, and if it is outside the standard value range, it is a defective product. This is the method to do so.

However, in practice it is extremely difficult to determine what is within the reference value range. The reason is as follows.

Even if each of the above-mentioned fluctuation factors is controlled to a constant value using an advanced and highly accurate control method, it will still fluctuate due to the influence of external disturbances.

Therefore, it is actually impossible to determine the range of variation that will result in a good product by leaving one variation factor and keeping the other variation factors constant and comparing the value of that variation factor with the quality of the molded product.

In reality, while all the fluctuation factors are fluctuating, the fluctuation range of each fluctuation factor that will result in a good product is determined.

However, although it is known that the product was defective under certain conditions, it is not known which variable factor was the cause.

In other words, many variable factors act synergistically to produce defective products.

If there are few fluctuation factors, it is possible to set a certain degree of reliable fluctuation range through trial and error, but since there are extremely many fluctuation factors in injection molding, it is necessary to make adjustments to the set fluctuation range. It is not possible to determine whether the quality is good or bad with a high degree of reliability.

Therefore, several methods for determining the quality of a product can be considered that require comprehensive quality determination based on the behavior of the molten material within the mold cavity.

For example, measuring the pressure of molten material in a mold cavity,
There is a method of setting a standard value for a molded product to be a good product.

[Problems that the invention attempts to resolve] However, when such a method is adopted, the following problems arise.

First, there is a problem in that the mounting position of the sensor for detecting the pressure of the molten material is limited.

That is, the mounting position of the sensor is limited by the influence on the appearance of the molded product, and is also limited by the machining of the sensor mounting hole in the mold.

Therefore, there are some molds that are difficult to judge whether they are good or bad because the sensor cannot be installed in an effective position.

The second problem is that when replacing the mold, it is necessary to attach and detach the connecting portion of the sensor.

This is the case when sensors are specially installed on all molds.
It also increases costs.

Therefore, if the sensor is shared by all molds for economical reasons, the sensor itself must be attached and removed when replacing the molds.

In other words, on the one hand, it is extremely unbalanced to try to automate the determination of whether a product is good or bad using an advanced system, and at the same time rely on humans to attach and detach sensors and connect parts.

In addition, as mold change operations are streamlined using mold setup devices and mold clamp devices, and automatic mold change devices are introduced, the presence of sensors for detecting the pressure of molten material has become a major bottleneck. Become.

In addition, there is a method that focuses on the deformation of the mold due to the pressure of the molten material in the mold cavity during the injection process, and attempts to measure the opening amount of the parting surface of the mold using a sensor, but in this case, However, there is an inconvenience in that it requires time and effort to attach and detach the sensor when replacing the mold.

[Means for solving the problems] In the present invention, in order to solve the above problems,
A gap measuring device is installed to measure the minute gap between the mold mounting plate and the mold, and a signal is emitted when the gap measurement value during the injection process becomes equal to a preset gap value.
On the other hand, a method was adopted in which the time from the start of injection to the generation of the signal was measured, and if the measured time value fell outside a preset time range that would result in good molding, a molding defect signal would be generated. .

Alternatively, you can set the injection time until a good product is formed, measure the gap value between the mold mounting plate and the mold when this set time is reached, and set this measured gap value beforehand. A method was adopted that generates a molding defect signal when the gap value is outside the range.

[Function] By adopting such a method, handling of the mold becomes easy, and manual work is not required when replacing the mold.
A sufficiently reliable method for determining the quality of molded products can be obtained.

Example Hereinafter, details of the method of the present invention will be explained with reference to the drawings.

[First Embodiment] FIGS. 1 to 8 illustrate a first embodiment of the present invention, and FIGS. 2 to 6 schematically show an injection molding apparatus.

In FIGS. 2 to 6, the reference numeral l indicates a fixed mold mounting board, on one side of which a fixed mold 2 is fixed, and on the other side an injection unit 3 is mounted. 3a is a nozzle.

Also, what is indicated by code 4 is a movable mold mounting board, and the movable mold 5
is fixed.

Reference numeral 6 indicates a tie bar, and 6a indicates a tie bar nut.

Further, a gap measuring device 7 is installed between the fixed mold mounting plate l and the fixed mold 2. This gap measuring device 7 is connected to the nozzle 3a of the injection unit and
It is located near the.

This gap measuring device 7 is configured to be able to electrically read the amount of mechanical displacement of a rod or the like, for example, like a differential transformer.

Incidentally, the gap measuring device 7 may be mounted on the movable mold mounting plate 4 as shown in FIG.

Next, the mold clamping operation of the injection molding apparatus having the above structure will be explained.

First, by a mold clamping device (not shown), a movable mold mounting plate (hereinafter referred to as a movable plate) 4 is fixed together with a movable mold 5.
The fixed mold 2 and the movable mold 5 come into contact with each other as shown in FIG.

In this state, no mold clamping force is acting, and no deflection occurs in the fixed mold mounting plate (hereinafter referred to as fixed plate) 1 and the movable plate 4.

The final process of mold clamping starts from this state, and when the mold clamping is complete,! As shown in Figure s3, a tensile force corresponding to the mold clamping force acts on the tie bar 6, and the fixed mold 1i11 is sandwiched between the fixed mold 2 and the tie bar nut 6a, causing deflection.

As a result, a gap is created between the fixed mold 2 and the fixed platen l, and this gap is measured by the gap measuring device 7.

When the mold clamping is completed, the molten material is injected into the mold cavity from the injection unit 3 side through the nozzle 3a.

When the filling of the molten material into the mold cavity is completed, the fixed mold 2 bends due to the pressure of the molten material as shown in FIG. Leave.

In this state, as shown in FIG. 4, the stationary mold 2 is biased toward the stationary plate 1, and the gap between it and the stationary plate 1 becomes small. This gap change is measured by a gap measuring device 7.

In addition, since the movable platen 4 side also bends during mold clamping, a gap measuring device may be provided on the movable platen 4 side as well to measure the gap between it and the movable mold 5.

FIG. 7 shows changes in the actual gap measurement values obtained by the gap measuring device 7.

@7 In Figure 7, the mold is touched at a point indicated by the symbol a, mold clamping is completed at point b, and injection starts at point 0.

Then, a predetermined injection pressure is maintained, and the injection pressure is lowered just before the filling of the molten material into the mold cavity is completed.

During this period, the gap between the fixed platen 1 and the fixed mold 2 reaches its maximum value.

When the filling is completed, the injection pressure becomes the minimum at point d, and the injection-secondary pressure is switched to the injection-secondary pressure.

At this point d, the gap between the fixed plate 1 and the fixed metal yA2 during the injection process takes a minimum value.

Then, secondary injection pressure is applied from point d, and after a predetermined time, the injection pressure is released at point e.

From this point on, the gap increases and plasticization starts at point f.

Then, plasticization is completed at point g, cooling is completed at point h, mold opening starts at point i, and mold opening is completed at point j.

In this way, one cycle of molding operation is completed.

Note that FIG. 1 is an enlarged view of section P in FIG. 7.

By the way, the above-mentioned injection molding apparatus is controlled by a control circuit as shown in FIG.

In FIG. 8, reference numeral 8 denotes a gap value setting device, which sets a gap value suitable for a range in which a molded product, which will be described later, is a good product.

This set value and the actual value measured by the gap measuring device 7 are compared in the signal generating device 9, and when the two values are equal, a time signal is given to the time measuring device 10.

This timing device 1O starts timing upon receiving the injection start signal, stops timing in response to a timing signal from the signal generator 9, and inputs the actual measured time to the molded product quality determining device 11.

On the other hand, reference numeral 12 is a non-defective product range setting device that sets the upper and lower limits of the time range in which the molded product becomes non-defective, and inputs these to the non-defective product determination device 11 .

Next, the operation of this embodiment configured as above will be explained.

FIG. 1 shows an enlarged view of section P in FIG. 7, and shows changes in the gap value from the start of injection to the completion of filling the mold cavity with molten material.

Now, if the ideal gap value is G, the time it takes to reach this gap value G varies depending on each shot, and if the lower limit is tl and the upper limit is t2, then the gap value G set in this time range If it reaches the target, a good product will be obtained for that shot.

Therefore, the gap value set in advance by the signal generator 9 and the actual value measured by the gap measurement device 7 are compared, and if the two match, a timing signal is generated, and the timing device starts timing from the injection start signal. If the counting of lO is stopped and the actual measured time is input to the pass/fail discriminator 11, the pass/fail discriminator 11 issues a non-defective command if the actual measured time is between the times tl and t2 shown in FIG. If it falls outside of this range, a defective product directive can be issued.

In this way, the quality of the molded product can be reliably determined based on objective criteria.

[Second Embodiment] FIG. 9 explains a second embodiment of the present invention, in which, unlike the above-mentioned embodiments, the time range for reaching the ideal gap value is not set, and good products are obtained. A method is adopted in which a time T is set until the ideal gap value is reached, and when this time is reached from the start of injection, it is determined that a good product can be obtained if the gap value is within a certain range. .

In FIG. 9, the reference numeral 13 is a timer, which starts counting from the start of injection.

When the timer 13 counts up to a preset time T, a timeout signal is input to the pass/fail determining device 11.

The upper limit value g1 and the lower limit value g2 of the gap value are inputted to the quality determining device 11 from the non-defective product range setting device 12.

Therefore, when the timer 13 times out, the quality determining device 11 can issue a non-defective product command if the gap value is within a preset range, and can issue a defective product command in other cases.

In this way, good products can be determined by focusing on the gap value range.

Note that the gap setting value G is usually one layer or less, and the timer setting value is about 5 to 15 seconds.

[Effect] As is clear from the above explanation, according to the present invention, an ideal gap value that yields a good product can be set in advance, and the time taken to reach this gap value can be set within a certain range, or the ideal gap value can be set in advance. By setting the time it takes to reach a value and giving a certain range to the gap value at the time this time is reached,
Because we use a method to determine whether the product is good or not,
It is possible to accurately determine the quality of molded products using objective criteria.

[Brief explanation of drawings]

FIGS. 1 to 8 illustrate the first embodiment of the present invention, and FIG. 1 is a diagram illustrating changes in gap value, and FIGS.
Figure 4 is a side view explaining the deflection state of each part during the molding operation process, Figure 5 is an enlarged sectional view explaining the installation of the gap measuring device, and Figure 6 is the gap measuring device installed on the movable platen side. A side view of the state, Figure 1i47 is a diagram explaining the change in gap value during the molding process, Figure 8 is a block diagram of the control circuit, and Figure 9 is a block diagram of the control circuit explaining the second embodiment of the present invention. It is a diagram. l... Fixed plate, 2... Fixed mold, 3... Injection unit, 4... Movable plate, 5... Movable mold,
6...Tie bar. 7... Gap measuring device, 8... Gap value setting device, 9
... Signal generator, 10... Timing device, 11.
...Good/failure determining device, 12...Good product range setting device, 13
...Timer. Patent applicant: Ube Industries, Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (2)

[Claims] (1) A gap measuring device is installed to measure the minute gap between the mold mounting plate and the mold, and in the process of filling the mold cavity with molten material, the value measured by the gap measuring device is set in advance. A signal is emitted when the gap value becomes equal to the specified gap value, and the time from the start of injection until the signal is emitted is measured. A method for determining the quality of a molded product, characterized in that a molding defect signal is generated when the product is out of range. (2) A gap measuring device is installed to measure the minute gap between the mold mounting plate and the mold, a timer is installed to measure the time from the start of injection, and the injection time until a good product is formed is set. Measures the gap value between the mold mounting board and the mold when the set time is reached, and generates a molding defect signal if the measured gap value is outside the preset gap value range. A method for determining the quality of a molded product.