JPH04358815A - Method for controlling temperature of mold for injection molding - Google Patents

Abstract

PURPOSE:To provide a method for controlling the temp. of a mold for injection molding wherein flow condition of a resin in the mold is not different each other on every shot when molding is performed. CONSTITUTION:The max. value of the amt. of mold opening when a resin is filled in a cavity 23 is measured. When the max. value of the amt. of mold- opening corresponding to the mold temp. 24.3-25.7 deg.C where a good molded item can be obtd. becomes out of a range of 40-60mum, the amt. of cooling water circulating in the mold 1 is controlled.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of an injection mold.

0002

[Prior Art] Conventionally, in injection molding, the nozzle of an injection molding machine is brought into contact with a fixed mold, and a movable mold is opened and closed with respect to the fixed mold, and when the movable mold is closed, Generally, the cavity formed during this process is filled with molten resin, and after cooling, the movable mold is opened and the product is taken out. In this process, the fixed mold and the movable mold are cooled by circulating cooling water whose inlet temperature is constant, while the temperature of the nozzle of the injection molding machine is raised and controlled by a heater. and,
Heat transfer from the nozzle to the mold occurs continuously. In this case, since the heat capacity of the mold is larger than that of the nozzle, a phenomenon occurs in which the temperature changes in a long-cycle temperature fluctuation pattern on the mold side. Due to this phenomenon, the resin flow state during molding differs from shot to shot, and the quality of the molded product changes. For example, if the mold temperature is higher than the target, burrs will occur on the parting surface, and if the mold temperature is lower than the target, there will be a short shot and resin filling will be insufficient.

0003

[Problem to be solved by the invention] The problems of this conventional method are as follows.
Even if you try to solve the problem by simply increasing the cooling capacity of the mold, the temperature drop at the nozzle will become large, and if you increase this heating capacity, this heat transfer will return to the mold.
In the end, the problem basically cannot be solved.

The present invention solves the above-mentioned conventional problems and provides a method for adjusting an injection mold to a predetermined temperature so that the resin flow state during molding does not vary from shot to shot. The purpose is to

[0005]

[Means for Solving the Problems] The present invention provides an injection mold in which a cavity for forming a molded product is provided between a fixed mold and a movable mold, and a cooling means is provided inside the cavity. A method for controlling the temperature of an injection mold, which measures the amount of mold opening between a fixed mold and a movable mold when filling resin into the mold, and adjusts the cooling amount of a cooling means based on the maximum value of the mold opening amount. , and an injection mold in which a molded product forming cavity is provided between a fixed mold and a movable mold, and a cooling means is provided inside the fixed mold when filling the resin into the cavity. Compare the maximum value of the mold opening amount between the moving mold and the moving mold with a pre-designed appropriate standard mold opening amount,
This is a temperature control method for an injection mold in which a cooling amount change signal is sent when the maximum value of the mold opening amount deviates from the standard mold opening amount to adjust the cooling amount.

[0006]

[Operation] Measures the maximum amount of mold opening between the fixed mold and the movable mold when filling the resin into the cavity. When a good molded product is obtained, the mold opens a certain amount. The mold temperature can be controlled during molding by knowing the constant mold opening amount that allows a good molded product to be obtained, and by adjusting the cooling amount of the mold cooling means at the point when the mold is outside of that range. The temperature can be adjusted to a predetermined temperature.

Furthermore, the maximum value of the mold opening amount between the fixed mold and the movable mold when filling the resin into the cavity is compared with an appropriate standard mold opening amount designed in advance, and the maximum value of the mold opening amount is determined. It becomes possible to automatically adjust the appropriate mold cooling amount by detecting the point in time when the mold opening amount deviates from the standard mold opening amount.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below by way of embodiments with reference to the drawings. FIG. 1 is a front view showing an embodiment of the method for controlling the temperature of an injection mold according to the present invention.

Reference numeral 1 denotes an injection molding machine, and a nozzle 11 for injecting resin is provided at the tip. 2 is a mold,
It consists of a fixed mold 21 and a movable mold 22, between which a cavity 23 for molding a molded product is formed, and the fixed mold 21 is provided with a sprue 24. The fixed mold 21 and the movable mold 22 each have a cooling water circulation path 2 therein.
11 and 221 are provided. The cooling water circulation path 211 of the fixed mold 21 is connected to the fixed mold cooling water temperature controller 3 by a cooling water feed pipe 32 provided with a flow rate adjustment valve 31 and a cooling water return pipe 33. Fixed mold 21
A displacement meter 5 is provided on the outer surface of the movable mold 22 side to measure the amount of mold opening between the fixed mold 11 and the movable mold 12 during resin injection molding into the cavity 23. is provided with an amplifier 6. The cooling water circulation path 221 of the movable mold 22 is connected to the movable mold cooling water temperature regulator 4 by a cooling water feed pipe 42 and a cooling water return pipe 43 provided with a flow rate adjustment valve 41 . Fixed mold 21
The nozzle 11 of the injection molding machine 1 is in contact with the inlet of the sprue 24 .

The space between the fixed mold 21 and the movable mold 22 is closed, and resin is filled into the cavity 23 through the nozzle 11 of the injection molding machine 1. Fixed mold 21 during resin filling
The displacement meter 5 measures the amount of mold opening between the movable mold 22 and the movable mold 22, and the amplifier 6 reads the maximum value of the mold opening amount. and,
Compare the maximum value of the mold opening amount with the range of the mold opening amount that has been determined to be appropriate in advance, and if it is outside the range,
By adjusting the amount of opening of the flow control valves 31 and 41, the amount of cooling water flowing into the cooling water circulation path 211 of the fixed mold 21 and the cooling water circulation path 221 of the movable mold 22 is adjusted. The temperature of the movable mold 22 is finely adjusted.

FIG. 2 shows an example of the relationship between the mold opening amount and the mold temperature. In Fig. 2, the mold temperature is 24.3°C when the resin is almost insufficiently filled into the cavity 23.
The maximum value of the mold opening amount corresponding to the following is less than 40 μm, and the mold temperature is 24.3 to 25.7 °C to obtain a good molded product.
The maximum value of the mold opening amount corresponding to 40 to 60 μm is 40 to 60 μm, and the maximum value of the mold opening amount corresponding to a mold temperature of 25.7° C. or higher, which is on the verge of burr generation, is 61 μm or more.

Based on this measurement result, when the maximum value of the mold opening distance corresponding to the mold temperature of 24.3 to 25.7°C in which a good molded product can be obtained is outside the range of 40 to 60 μm, the flow rate The amount of opening of the control valves 31 and 41 is adjusted to adjust the amount of cooling water flowing into the cooling water circulation path 211 of the fixed mold 21 and the cooling water circulation path 221 of the movable mold 22. The temperature of the mold 22 will be finely adjusted.

FIG. 3 shows the relationship between the mold opening amount and the valve opening amount. When the maximum value of the mold opening amount is within the range of 40 to 60 μm, the opening amount of the flow control valve 31 is maintained as it is. When the maximum value of the mold opening amount exceeds 60 μm, the opening amount of the flow control valves 31 and 41 is adjusted to 1.2 times. Further, when the maximum value of the mold opening amount becomes less than 40 μm, the opening amount of the flow rate regulating valves 31 and 41 is adjusted to 0.8 times.

FIG. 4 is a front view showing another embodiment of the method for controlling the temperature of an injection mold according to the present invention. In addition to the embodiment shown in FIG. 1, a computing device 7 is connected to the amplifier 6 of the displacement meter 5, and the computing device 7 is connected to the flow rate regulating valves 31, 41.

FIG. 5 is a block diagram of the control circuit of this embodiment. The central processing unit CPU70 includes a displacement measurement unit 71.
, reference mold opening amount setting section 72, comparison section 73, display section 74,
Valve opening device section 76 via valve opening signal transmitting section 75
is connected.

FIG. 6 is a flowchart showing an example of a valve opening operation controlled by a program in the central processing unit CPU70. In step S1, injection molding machine 1
The resin is injected into the cavity 23 of the mold 2 to fill the cavity 23 with the resin.

In step S2, the maximum value of the mold opening amount between the fixed mold 21 and the movable mold 22 is measured by the displacement meter 5. In step S3, the comparison unit 73 determines whether the maximum value of the measured mold opening amount is outside the range of mold opening amounts set in advance in the reference mold opening setting unit 72.

It is determined whether the maximum value of the measured mold opening amount is outside the range of the reference mold opening amount by repeating the operations of step S2 and step S3. Step S
In step 4, the valve opening signal transmitting section 55 transmits a signal when the valve opening amount falls outside the range of the standard mold opening amount.

In step S5, the valve opening device section 76
The opening amount of the flow rate regulating valves 31 and 41 is adjusted at . The operations of steps S1 to S5 are repeated throughout injection molding to adjust the temperature of the mold during molding.

When 2000 office equipment parts were manufactured by injection molding according to this example, there were 20 defective parts at the start, 0 burrs, 0 underfilling, the number of good parts was 1980, and the good product efficiency was It was 99%.

On the other hand, when 2000 of the same office equipment parts were manufactured by injection molding using the conventional method, 20 had poor starts, 80 had burrs, 90 had insufficient filling, and 10 had other defects. The number of good products is 1800.
Good product efficiency was 90%.

[0022]

[Effect] The method for controlling the temperature of an injection mold of the present invention has the above-described structure, so that the mold opening between the fixed mold and the movable mold is prevented when filling the resin into the molded product forming cavity. Based on the maximum value of the amount, the cooling amount of the mold cooling means can be adjusted to obtain a good molded product, and the mold temperature can be adjusted to a predetermined temperature.

[0023] Since the temperature control method for an injection mold of the present invention is configured as described above, the maximum value of the mold opening amount is compared with an appropriate standard mold opening amount designed in advance, and the mold opening amount is By determining the point in time when the maximum opening amount deviates from the standard mold opening amount, it becomes possible to automatically adjust the appropriate mold cooling amount.

[Brief explanation of drawings]

FIG. 1 is a partially longitudinally sectional front view illustrating an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the mold opening amount and fixed mold temperature in one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the amount of mold opening and the amount of valve opening in one embodiment of the present invention.

FIG. 4 is a partially longitudinally sectional front view illustrating another embodiment of the present invention.

FIG. 5 is a block diagram of a control circuit according to another embodiment of the present invention.

FIG. 6 is a flowchart showing an example of a valve opening operation controlled by a program in a central processing unit CPU according to another embodiment of the present invention.

[Explanation of symbols]

1 Injection molding machine 2 Mold 3 Fixed mold cooling water regulator 4. Mobile mold cooling water regulator 5 Displacement meter 6 Amplifier 7 Arithmetic machine 11 Nozzle 21 Fixed mold 22 Moving mold 31, 41 Flow rate adjustment valve 211, 221 Cooling water circulation path

Claims (2)

[Claims] Claim 1: In an injection mold in which a cavity for forming a molded product is provided between a fixed mold and a movable mold, and a cooling means is provided inside the mold, the fixation during filling of the resin into the cavity is performed. A method for controlling the temperature of an injection mold, characterized by measuring the amount of mold opening between a mold and a movable mold, and adjusting the amount of cooling of a cooling means based on the maximum value of the amount of mold opening. [Claim 2] In an injection mold in which a cavity for forming a molded product is provided between a fixed mold and a movable mold, and a cooling means is provided inside the mold, the fixation during filling of the resin into the cavity is performed. The maximum value of the mold opening amount between the mold and the moving mold is compared with the appropriate standard mold opening amount designed in advance, and a cooling amount change signal is issued when the maximum value of the mold opening amount deviates from the standard mold opening amount. A method for controlling the temperature of an injection mold, characterized by transmitting a signal and adjusting the amount of cooling.