JPH0494856A - Method for controlling cooling time to casting in die casting - Google Patents

Abstract

PURPOSE:To improve machine cycle and to improve the productivity by detecting inflection point of feeder head pressure at the time of acting the feeder head to measure feeder head effect acting to a molten metal of a plunger tip and using completing point of this feeder head effect to cooling time control. CONSTITUTION:Signal from a pressure measuring instrument 25 is transmitted to a feeder head effect measuring instrument 21 and completing timing for feeder head effect is decided with the feeder head effect measuring instrument 21 and this completing timing is outputted to a timer 24. Time-out signal in this timer 24 is transmitted to a die opening/closing control unit 26 and this die opening/closing control unit 26 executes die opening movement by feeding the oil pressure into a die opening side oil pressure hole 23 in die clamping cylinder 6 with this signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a casting cooling time control device in mold casting such as a die-casting machine. By controlling the casting cooling time (cure time) by determining the effect of feeding the molten metal with the plunger tip of the injection mechanism, stable quality of the cast product is ensured and the casting cycle is shortened.

[Prior Art] In mold casting such as a die-casting machine, the product casting is taken out from the mold when the temperature of the casting in the mold is determined by the solidification characteristics of the molten metal used (hereinafter referred to as ideal temperature). This must be done when the temperature has dropped to a certain temperature.

(11) If the product casting is taken out at a temperature higher than the ideal temperature mentioned above, the casting will not easily release from the mold, causing damage to the mold, and the distortion rate and shrinkage rate of the casting after taking out will be large. Dimensional accuracy is unstable, resulting in an increase in defective rates and wide variation in quality.Of course, if the mold is opened before the molten metal in the mold has completely solidified, the casting may burst or seize. .

(2) Conversely, if the casting is left in the mold indefinitely after the temperature of the casting inside the mold has fallen to the above-mentioned ideal temperature,
If the casting cycle time is increased unnecessarily, the number of pieces cast per hour will be reduced, resulting in disadvantages.

The most reliable way to determine whether the temperature of the casting inside the mold has fallen to the ideal temperature is to directly measure the casting inside the mold, but at present there is no suitable means for directly measuring this.

Therefore, conventionally, the starting point is the start of low-speed molten metal injection or the start of high-speed injection, and the time it takes for the molten metal injected into the mold to absorb heat in the mold, condense, and drop to the ideal temperature. was determined through preliminary tests such as mold release and quality stability, and a timer was set based on this time as a guideline for when to take out the casting.

For example, this was done in the manner shown in Figure 2.

FIG. 2 is a configuration diagram for explaining a casting method in a die-casting machine and a conventional method for controlling casting cooling time.

In FIG. 2, molten aluminum 17 is injected into a cavity 18 formed by a fixed mold 8 and a movable mold 9 from an injection sleeve 1o attached to the fixed mold 8, and into an injection cylinder 1.
After cooling, the mold is opened by moving the movable mold 9 to the left in the figure using a mold opening/closing device (not shown). Take out the molded aluminum product inside.

FIG. 2 shows a nearly intermediate step in the casting operation, and at the time of preparation for injection start, the piston rod lla of the injection cylinder 11 is located at the right end in the figure, and therefore the plunger tip llb is also located on the right side. The injection process begins by pouring molten metal 17 from the hot water supply port 10a provided at the right end of the injection sleeve 1o using a hot water supply ladle (not shown).

Further, in FIG. 2, an injection striker lid is connected by a coupling llc of a piston rod lla, and a limit switch 12a.

12b, the positions of the piston rod 11a and plunger tip llb are taken out as electrical signals.

That is, during preparation for injection, the piston rod 11a and the striker lid are at the right end, and the limit switch 12
b is at the position hit by the striker lid.

In addition, the limit switch 12a is located at the point where the cavity filling process begins, and when the striker lid passes this point, a signal is taken out from the limit switch 12a and a hydraulic system for high-speed injection, which is not disclosed, is operated. A large amount of pressure oil is introduced into the pressure oil flow port I9 of the injection cylinder 11,
It is designed for high-speed injection.

As described above, the timing for opening the mold in the prior art is determined by connecting the signal from the limit switch 12a in FIG. Generally, the cooling time is determined by this.

[Problems to be Solved by the Invention] However, in the conventional method using a timer that starts at the start point of low-speed molten metal injection or high-speed injection, Since the cooling rate characteristics of the molten metal in the mold depend on changes in the mold temperature (current mold temperature), it was necessary to set the timer time in consideration of changes in the molten metal temperature and the initial temperature in the mold casting cycle. .

Furthermore, since the injection conditions during low-speed injection and high-speed injection are not necessarily constant during each injection, there are variations in the operating time during that time, and the mold opening start point is not always at the ideal point each time.

On the other hand, the current casting cycle time of a medium-sized die casting machine with a mold clamping force of 500 t to 630 t is about 40 seconds, of which the casting cooling time is generally about 10 seconds.

According to the above data, the casting cooling time that is included in the casting cycle time is 25%, but due to improvements in manufacturing technology for die casting machines and automatic machines surrounding die casting machines, the proportion of the casting cooling time that is included in the casting cycle time is increasing. Furthermore, this tendency can be said to be more pronounced for small-sized aircraft than for medium-sized aircraft.

Improving productivity as well as stabilizing quality has always been a major challenge for manufacturing companies, and we have developed methods to reduce variations in molten metal temperature, as mentioned in the prior art section, and methods for mold casting cycles. Although measures to stabilize the initial temperature have been gradually introduced, it is still not sufficient, and a long timer is set to take out the casting from the mold, allowing for a safety factor of about 10 to 20%. Generally speaking, this means that there is waste in the casting cycle.

Therefore, an object of the present invention is to find a method for controlling the casting cooling time that can follow variations in the temperature of the molten metal and changes in the initial temperature during the casting cycle of the mold, thereby ensuring stabilization of quality and reducing the casting cycle time. The aim is to shorten the time.

[Means for Solving the Problems] In order to solve these problems, the present invention continuously observes the movement state of the plunger depth of the injection mechanism in real time, and determines the timing at the completion of the molten metal feeding operation. A timer is provided that starts when this time is completed, and the casting is taken out when this timer time is completed.

Note that this timer time is the same as in the conventional technology, due to mold separation,
Determined through preliminary tests such as quality stability.

[Function] In the present invention, the completion of the feeder operation is determined by measuring the timing of casting removal control in the mold to measure the state in which the plunger tip of the injection mechanism acts on the molten metal, and the completion of this feeder effect is determined. Since it is used as the starting point, it is possible to follow changes in the temperature of the molten metal and the initial temperature of the mold casting cycle. Then, the safety factor for the timer setting time can be set to a small value.

Therefore, wasted time in the casting cycle can be reduced, and the number of pieces cast per hour can be increased.

[Embodiment] FIG. 1 is a block diagram for explaining one embodiment of the method for controlling the casting cooling period in die casting according to the present invention. In FIG. 1, parts with the same functions as those in FIG. 2 are given the same reference numerals, and detailed explanations are omitted.

In Fig. 1, 1 is a machine base, 2 is a fixed platen, 3 is a link housing, and 4 is a movable platen. A movable mold 9 is held.

Column 5 is four columns arranged parallel to each other.
Both ends are fixed to the fixed platen 2 and outside the link housing 3 by column nuts 5a.

6 is a mold clamping cylinder, and 7 is a toggle mechanism.

The mold clamping cylinder 6 is fixed to the link housing 3, and a piston rod 6a installed inside the mold clamping cylinder 6
The toggle mechanism 7 is expanded and contracted via the movable platen 4 so that the movable platen 4 can be moved closer to or retreated from the fixed platen 2.

An injection striker lid is connected to the piston rod lla of the injection cylinder 11 by a coupling llc, and a magnetic scale 11e is attached to the injection striker lid.A magnetic scale sensor 12e attached to the machine base l side measures the injection striker lid. It is now possible to measure the moving position.

On the other hand, there is a pressure measuring device 25 in the hydraulic circuit on the head end side of the injection cylinder 11, and the action of this pressure measuring device 25 makes it possible to measure the oil pressure during the feeder operation.

The signal from the pressure measuring device 25 is sent to the feeder effect measuring device 21, which determines the completion timing of the feeder effect, outputs this completion timing to the timer 24, and causes the timer 24 to time out. The signal is connected to the mold opening/closing control device 26, and the mold opening/closing control device 26 uses this signal to send hydraulic pressure to the mold opening side hydraulic port 23 of the mold clamping cylinder 6 to perform the mold opening operation.

In FIG. 1, 22 is a hydraulic port on the mold clamping side of the mold clamping cylinder 6, 16 is a ladle for supplying molten metal to the injection sleeve 10, 17 is a molten metal, and 18 is a mold cavity.

When injection is performed with a die-casting machine, low-speed injection is followed by high-speed injection, and molten metal 1 is poured into the mold cavity 18.
7 is filled, the pressure P acting on the molten metal 17 is
As shown in the figure, at this point to, -1, it suddenly rises. This is because the space inside the cavity 18 is almost completely eliminated by filling the cavity 18 with the molten metal. At this point t. Solidification of the molten metal begins in earnest from then, and the feeder action begins by continuing to apply injection pressure to the plunger tip flb. after that,
The metal pressure P begins to gradually increase, and in this process the molten metal almost completely solidifies.

Once the molten metal has almost completely solidified within the cavity 18, the solidified material begins to become rigid, and the metal pressure increases rapidly again. In this case, an inflection point A at time t1 when the pressure changes from the previous gradual pressure increase process to a rapid increase again is detected by pressure detection. Note that, once the metal pressure P rises rapidly and reaches the maximum pressure, it remains at a constant pressure thereafter.

On the other hand, time t. From then on, the plunger tip Ilb continues to move forward and performs the feeder operation, but once the inflection point A reaches the time t1, the stroke S of the plunger tip Ilb is generally as shown in Fig. 3. As shown by the solid line,
Although it gets a little bigger, it doesn't really get that big.

Therefore, in the present invention, when the inflection point A is reached, it is determined that the desired effect has been achieved. That is, the inflection point A is the apparent completion point of the feeder operation.

In the present invention, the timer 24 is started from the time t1 when the inflection point A is reached, and when the timer 24 times out, a mold opening command is issued and the mold opening is performed.

In this case, the state of the metal pressure changing from moment to moment can be checked by continuously measuring the pressure acting on the injection cylinder 11 using a pressure gauge.

Further, the set time of the timer 24 is determined based on experience and results of preliminary tests such as mold release and quality stability. The setting time of this timer 24 is usually about several seconds, for example, 5 seconds or less.

Generally, the forward stroke S of the riser member such as the plunger tip llb is as shown by the solid line in FIG. For example, it is possible to set in advance so that it increases linearly at a constant slope over time, and to control it so that it increases in a linear manner. In this case as well, the inflection point A is reached.

As another embodiment of the present invention, the oil pressure acting on the oil pressure port 19 of the injection cylinder 11 may be used to determine the feeder effect.

Similarly, the injection force acting on the piston rod lla can also be used.

In recent years, with the development of microcomputers, the riser effect measuring device 21 shown in Fig. 1 has been developed. It is also a good idea to integrate the timer 24 as a monitoring device, or to incorporate it as a mold opening/closing control device 26.

[Effects of the Invention] As explained above, in the casting cooling time control method according to the present invention, the riser effect acting on the molten metal of the plunger tip is determined by detecting the inflection point of the feeder pressure during the feeder action. The completion point of this riser effect is used to control the cooling time, so it is possible to follow changes in the temperature of the molten metal and the initial temperature of the mold casting cycle. Even if the operating time varies due to variations in the injection conditions during high-speed injection or high-speed injection, the time after the riser effect is achieved remains constant, so it is necessary to allow extra time for the cooling time to account for the error. Nor.

Therefore, the cooling time can be controlled with a smaller safety factor, that is, with less waste. This improves the machine cycle and improves productivity.

[Brief explanation of the drawing]

FIG. 1 is a front view showing one embodiment of a device for carrying out the present invention, FIG. 2 is a schematic explanatory diagram showing an example of a conventional device similar to the present invention, and FIG. 3 is a pusher according to the present invention. FIG. 3 is a diagram showing a hot water effect measurement state. 6... Mold clamping cylinder, 8... Fixed mold, 9... Movable mold, 10...
・Injection sleeve, 11...Injection cylinder, li
e... Magnetic scale, 12e... Magnetic scale sensor, 18... Cavity, 21... Boiler effect measuring device, 24... Timer, 25... ...Pressure measuring instrument, 26... Mold opening/closing control device, A...
...An inflection point. Patent applicant: Ube Industries, Ltd.

Claims (2)

[Claims] (1) A method for controlling the cooling time of a casting in mold casting, characterized in that the cooling time of the casting within the mold is controlled by determining the effect of a plunger tip of an injection mechanism or a feeder mechanism. (2) When controlling the cooling time of the casting in the mold by determining the riser effect, the mold cavity is filled with molten metal and the metal pressure increases rapidly, then gradually increases, and then , the inflection point when the pressure changes from this gradual pressure increase process to the process of rapid increase again is detected by pressure detection, and it is determined that a predetermined feeder effect has been obtained at this inflection point,
2. A method for controlling casting cooling time in mold casting according to claim 1, wherein a timer is started from the time when this inflection point occurs, and when the timer times out, a command to open the mold is issued.