JP2004090064A - Method for controlling temperature of die-casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling the temperature of a mold which prevents the thermal distortion of the mold, whereby the growth of burrs and flashes can be restrained. <P>SOLUTION: The invention relates to the method for controlling the temperature of the mold in a die-casting process. There is provided, near the periphery of the mold 1, a heating path 2 through which an electric heater or a heating medium is connected to the mold inside to control the temperature of the mold. The temperature of the mold is controlled by actuating a temperature controller 5 with an output from a control circuit 6 based on temperature information from a peripheral temperature sensor 3 and a product part temperature sensor 4 so that the temperature near the periphery of the mold is higher than that at the product part which is the center part of the mold when molten metal commences to flow into the product part (cavity) 11 by mold clamping. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of controlling the temperature of a mold in die casting in which a molten metal is injected and filled into a cavity formed by a fixed mold and a movable mold of a mold, and after the product is solidified, the mold is opened to take out the product.
[0002]
[Prior art]
In general, in die casting, in which a molten alloy such as Al, Zn, Mg, Cu, etc. is injected into a mold at a high speed and a high pressure and rapidly solidified, conditions such as a molten metal temperature, a casting time, and a casting pressure greatly affect the quality and defect rate of a product. In particular, at the start of casting in which the temperature of the mold is lower than a predetermined appropriate temperature, a run-out defect or the like often occurs. As a countermeasure for this, generally, a method of locally increasing the mold temperature of the product part (cavity part) of the mold by the residual heat by a mold temperature controller or a gas burner, or by test casting and the heat of the molten metal is used. Has been done.
[0003]
FIG. 5 shows one such conventional mold temperature control method. In FIG. 5, a mold 1 has two product parts (cavities) 11 filled with a molten metal, a runner part 12 which is a passage of the molten metal to the product part 11, and a biscuit part 13 which is a supply port of the molten metal. Is formed, and a heating medium path 2 connected to an external temperature control device 3 as a heating source is buried almost immediately below the product section 11 to locally control the temperature of the product section 11 of the mold 1. Can be ascended.
[0004]
However, conventionally, in the die casting, since a molten metal is filled in a product portion (cavity portion) arranged in a central portion of the mold 1, as shown in a surface temperature distribution of the mold in FIG. Heat is accumulated in the portion, and a temperature difference of about 150 ° C. occurs between the central portion and the outer peripheral portion of the mold 1. For this reason, as shown in FIG. 7 which is a cross section taken along the line AA in FIG. 6, the fixed mold 1A and the movable mold 1B of the mold 1 are easily thermally deformed into a convex shape, and burrs and flashes are easily generated. There was a problem.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a mold temperature control method capable of preventing deformation of a mold due to heat and suppressing generation of burrs and flashes. .
[0006]
[Means for Solving the Problems]
The present invention provides a mold temperature control method described in each claim as means for solving the above-mentioned problem.
In the mold temperature control method according to the present invention, an electric heater or a heating medium is provided near the outer periphery of the mold to provide a heating path for controlling the mold temperature by passing the heating medium into the inside of the mold. At the start of filling of the molten metal, the mold temperature is controlled so that the temperature near the outer peripheral portion is higher than the temperature at the product portion, which is the central portion of the mold. In addition, the fixed mold and the movable mold do not deform into a convex shape, and as a result, generation of burrs, flashes, and the like can be prevented.
[0007]
According to a second aspect of the present invention, there is provided a mold temperature control method, wherein a temperature sensor for measuring a mold temperature is arranged at least near a heating portion near an outer peripheral portion of the mold and near a product portion. Mold temperature can be controlled accurately.
According to a third aspect of the present invention, there is provided a method of controlling a mold temperature such that a temperature difference between a vicinity of an outer peripheral portion of a mold and a vicinity of a product portion is within a predetermined temperature range. And the deformation of the mold due to heat is controlled.
[0008]
According to a fourth aspect of the present invention, there is provided a mold temperature control method in which a strain sensor for measuring a strain of a mold or a stress sensor for measuring a stress generated in a mold at the time of mold clamping is disposed in place of a temperature sensor for measuring a mold temperature. Therefore, instead of directly measuring the mold temperature, the deformation of the mold is predicted by measuring the strain of the mold or the stress generated in the mold, and the mold temperature is controlled. Thus, deformation of the convex shape of the mold is prevented.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a mold temperature control method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic overall configuration of a mold temperature control system for implementing a mold temperature control method according to an embodiment of the present invention. Reference numeral 1 denotes a mold composed of a fixed mold 1A and a movable mold 1B. The mold 1 includes a product section (cavity section) 11, a runner section (branch passage) 12, and a biscuit section (common passage) 13. Is fitted. In FIG. 1, two product parts 11 are formed, and a runner part 12 is formed so as to connect the biscuit part 13 and the two product parts 11. Therefore, when the mold 1 is clamped, the molten metal is filled from the biscuit portion 13 through the runner portion 12 into the product portion 11.
[0010]
A heating medium path (heating path) 2 for passing a heating medium through the inside of the mold 1 is embedded around the entire periphery of the mold 1, and the heating medium path 2 has a temperature of the heating medium. Is connected to an external temperature controller 5 for adjusting the temperature. Further, an outer peripheral temperature sensor 3 is provided near the heating medium path 2 near the outer peripheral portion of the mold 1, and a product temperature sensor 4 is also provided near the product portion 11 at the center of the mold 1. The outer peripheral temperature sensor 3 and the product temperature sensor 4 are connected to a control circuit 6, and temperature information of the outer peripheral portion of the mold 1 and temperature information of the product portion 11 are input to the control circuit 6. The control circuit 6 outputs based on the temperature information and controls the temperature adjusting device 5.
[0011]
In this case, an electric heater may be used as a heating source of the mold 1 instead of the heating medium. Further, a plurality of temperature sensors 3 and 4 may be provided on the outer peripheral portion and the product portion 11 instead of one each.
For example, the installation position of the outer peripheral temperature sensor 3 is set to a depth within 5 mm from the surface of the mold, and the heating medium path 2 provided in the outer periphery of the mold 1 is installed within 200 mm from the outer periphery of the mold. The temperature of the mold is controlled so that the temperature difference with the part falls within 0 to 100 ° C.
FIG. 1 shows either the fixed mold 1A or the movable mold 1B of the mold 1, and the heating medium path 2 is formed symmetrically in the other molds as shown. Similarly, an outer peripheral temperature sensor 3 and a product temperature sensor 4 are provided.
[0012]
FIG. 2 is a graph showing a mold temperature change in one cycle based on the mold temperature control method according to the embodiment of the present invention. The solid line indicates a temperature change at the outer peripheral portion of the mold, and the broken line indicates a temperature change at the product part of the mold. The vertical axis of the graph indicates mold temperature, and the horizontal axis indicates time. As can be seen from the graph, in the mold temperature control method of the present invention, the mold outer peripheral portion having a low mold temperature is actively heated by operating the temperature control device 5 in advance or during continuous casting, and the molten metal is heated. At the start of injection of the mold, the mold temperature is controlled such that the mold outer peripheral temperature Tb becomes higher than the mold product part temperature Ta (Tb> Ta). As the product part 11 is filled with the molten metal, the temperature of the product part 11 begins to rise rapidly due to the heat of the molten metal, and the temperature difference disappears. At the end of filling, the product part temperature Ta is higher than the outer peripheral part temperature Tb. (Ta> Tb). In the state of Ta> Tb, the cooling and setting of the product proceeds. After the product has completely set, the mold is opened and the product is taken out of the mold 1. When the product is taken out of the mold 1, the temperature of the product portion 11 decreases more rapidly, the temperatures of Ta and Tb are reversed again, and the temperature of the outer periphery of the mold is controlled so that Tb> Ta. The mold is clamped in this state. Thus, one cycle is completed, and this cycle is repeated. In this case, the temperature adjusting device 5 is controlled by the control circuit 6 such that the difference between the outer peripheral portion temperature Tb and the product portion temperature Ta is always within a certain temperature range (for example, 0 to 100 ° C.).
[0013]
FIG. 3 is a diagram for explaining the surface temperature distribution of the mold 1 when the outer peripheral portion of the mold 1 is heated by operating the temperature adjusting device 5. In the figure, the higher the point density, the higher the temperature. As can be seen from this figure, the temperature of the outer peripheral part of the mold 1 (about 250 ° C.) is higher by about 50 ° C. than the temperature of the product part 11 which is the central part of the mold 1 (about 200 ° C.). I have.
[0014]
FIG. 4 is a cross-sectional view taken along the line AA of FIG. 3, and is a view for explaining thermal deformation of the molds of the movable mold 1B and the fixed mold 1A. As can be seen from this figure, when the temperature of the outer peripheral part of the mold 1 is higher than the temperature of the product part 11 which is the central part, the fixed mold 1A and the movable mold 1B are deformed into concave cross sections. That is, the fixed mold 1A and the movable mold 1B are deformed so that the outer peripheral portions of the mutually facing surfaces slightly protrude. Thereby, generation of burrs and flashes during casting can be prevented.
[0015]
In the above-described embodiment, the temperature sensors 3 and 4 are installed in the mold 1 to measure the mold temperature, and the temperature adjusting device 5 is controlled based on the measured temperature. A mold is provided with a strain sensor for measuring the strain of the mold or a stress sensor for measuring the stress generated in the mold at the time of mold clamping, and the control circuit 6 controls the temperature adjusting device 5 based on the measurement results. May be.
[0016]
As described above, in the present invention, by controlling the temperature of the outer peripheral portion of the mold, the temperature distribution of the mold can be stabilized, and the occurrence of burrs and flashes due to thermal deformation of the mold can be reduced. Can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall schematic configuration of a mold temperature control system for implementing a mold temperature control method according to an embodiment of the present invention.
FIG. 2 is a graph showing a mold temperature change by a mold temperature control method according to an embodiment of the present invention.
FIG. 3 is a diagram showing a surface temperature distribution of a mold according to the present invention.
FIG. 4 is a diagram illustrating thermal deformation of a mold according to the present invention.
FIG. 5 is a schematic diagram of a prior art mold temperature control system.
FIG. 6 is a diagram showing a surface temperature distribution of a mold according to the related art.
FIG. 7 is a diagram illustrating thermal deformation of a mold according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Die 1A ... Fixed mold 1B ... Movable mold 11 ... Product part (cavity part)
12 ... Runner part (branch passage)
2. Heating medium path (heating path)
3: outer peripheral temperature sensor 4: product temperature sensor 5: temperature adjusting device 6: control circuit

Claims (4)

Injection filling of a molten metal into a product part formed by a fixed mold and a movable mold of a mold, and a mold temperature control method in die casting in which the mold is opened and the product is taken out after solidification of the product,
In the vicinity of the outer periphery of the mold, a heating path for controlling the mold temperature by conducting an electric heater or a heating medium into the inside of the mold is provided. A mold temperature control method that controls the mold temperature such that the temperature is higher near the outer peripheral portion of the mold than at the portion. 2. The temperature sensor according to claim 1, wherein two or more temperature sensors for measuring a mold temperature are provided, one of which is arranged at a heating portion near an outer peripheral portion of the mold, and the other is arranged near a product portion of the mold. 3. The mold temperature control method according to 1. The mold temperature control method according to claim 2, wherein the mold temperature is controlled such that the temperature difference between the vicinity of the outer periphery of the mold and the vicinity of the product part is within a certain temperature range. 3. The method according to claim 2, wherein a strain sensor for measuring strain of the mold or a stress sensor for measuring stress generated in the mold at the time of mold clamping is arranged in place of the temperature sensor for measuring the mold temperature. The described mold temperature control method.

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