JPH07100225B2 - Pressure pin timing control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling the timing of pressing a pressing pin, which is improved in the setting of the pressing timing of the pressing pin in the casting process of a die cast casting. is there.

(Prior Art) When a die cast casting is produced, when the molten metal injected into the cavity is cooled and solidified, the volume of the molten metal shrinks, which causes internal shrinkage in the cavity. These deficiencies deteriorate the finish shape of die cast products,
Alternatively, oil leakage or the like will occur, which will hinder the performance of the product. Therefore, measures have conventionally been taken to prevent this. The most common way to do this is
This is a method in which a pressure pin is provided in the vicinity of the cavity, and the pressure pin is projected into the cavity immediately before the molten metal injected into the cavity is solidified (as a related technique of this type, JP-A-59-156560). (See Japanese Laid-Open Patent Publication No. 58-9758).

(Problems to be Solved by the Invention) Among the methods of pressing the molten pin immediately before solidification by projecting the pressing pin into the cavity as described above, the technique disclosed in the former publication is The timing is controlled to be constant by a timer, and the technique described in the latter publication detects the temperature of the mold or the temperature of the molten metal in the cavity with a sensor and controls the temperature. In the former technique, the timing of pressurization may change due to the different solidification rate before the mold temperature rise at the start of casting, when the mold temperature is stable, and in the summer and winter, which may cause variations in product quality. There was a problem. On the other hand, the latter technique has a problem that it is difficult to grasp the relationship between the temperature of the mold or the temperature of the molten metal and the pressurization timing unless a considerable amount of data is accumulated. And there is a problem that the effect of pressurization is likely to be varied with the temperature of the mold and the temperature of the molten metal, and these elements do not correspond to each other, so that even if they are controlled, the effect of quality improvement cannot be obtained so much. .

The present invention has been made to solve these problems of the above-mentioned conventional technology, and is always calculated by calculating the pressurizing timing that can secure the necessary pressurizing stroke of the pressurizing pin. The purpose is to provide a method by which a good quality product can be obtained.

(Means for Solving the Problems) As a means for solving the above problems, the present invention is a die-casting method in which a pressure pin is pressed immediately before solidification of a die-cast casting, and the pressure stroke of the pressure pin is shot every shot. It is characterized in that the pressurizing timing at which a necessary pressurizing stroke can be secured is calculated from this measured value, and the subsequent pressurizing operation of the pressurizing pin is controlled by the pressurizing timing. This method of the present invention can be implemented by a microcomputer by building a predetermined program.

(Operation) Since the method of the present invention having the above-mentioned configuration calculates data for each shot and obtains the pressurizing timing in the subsequent die casting process from the value, it is possible to stably obtain a die casting product of constant quality at all times. It will be.

(Embodiment) Next, a pressurizing timing control method for a pressurizing pin according to the present invention will be described with reference to the drawings. In FIG. 1, 1 and 2 are die casting molds, and 3 is a cavity formed therebetween. A pressure pin 4 is provided inside the one die casting mold 2 toward the cavity 3, and the pressure cylinder 5 causes the pressure pin 5 to project and retract into the cavity 3. The pressure cylinder 5 has a hydraulic valve 6
Is connected, and the backward movement of the pressurizing pin 4 is controlled by the flow of hydraulic oil between the hydraulic power source 7 and the drain tank 8.

A potentiometer 9 is attached to the rear portion of the pressurizing cylinder 5, and is connected to a cylinder rod (not shown) inside the pressurizing cylinder 5, and its stroke, that is, the pressurizing pin 4 is connected.
Is converted into an electric output signal. The output side of the potentiometer 9 is connected to the microcomputer 10 so that the pressure stroke can be read. The microcomputer 10 measures the pressurization stroke, determines the optimum timing for the next chute, and issues a control signal to the hydraulic valve 6 that operates in the next chute.

To carry out the method of the present invention using the apparatus thus prepared, the following is performed. First, the die casting dies 1 and 2 are closed to form a cavity 3, and the cavity 3 is rapidly filled with molten metal. The molten metal at this time is used as a dummy.
After the molten metal is filled, the hydraulic pressure is supplied from the hydraulic valve 5 to the pressurizing cylinder 6 at a timing previously obtained from experience in the past, or when an appropriately determined time has elapsed, and the pressurizing cylinder 5 is operated to apply the pressure. The pressure pin 4 is projected into the cavity 3. Since the pressurizing pin 4 projects, the volume inside the cavity 3 is reduced, and the molten metal is in a filled state with no gaps, so that a good cast product can be obtained. At this stage, the stroke of the pressure pin 4 is checked so that the product is in the best condition.

In this way, the stroke of the pressurizing pin 4 is obtained so that the product is in the best condition, and the output signal of the potentiometer 9 at that time is taken into the microcomputer 10. The microcomputer 10 measures the pressurization stroke from the captured value, determines the optimum timing for the next shot, and feeds it back to the next shot.
Steps 11 to 16 in FIG. 2 are flowcharts showing the above procedure. Further, FIG. 3 shows the correlation between the pressurization stroke and the leak defect rate, and FIG. 4 shows the correlation between the pressurization stroke and the pressurization timing. The condition of the maximum value of the pressurizing stroke in FIG. 3 is from the maximum value when the pressurizing timing is 0 in FIG. 4 to the value indicated by the symbol A when 10 seconds have elapsed.

When the pressurizing timing of the pressurizing pin is actually controlled by the method of the present invention, it is possible to obtain the result that the defect rate and the variation in two different parts of a certain product are greatly different from the conventional method. I was able to. That is, whereas the conventional leak defect rate in one portion was 3.8%, the method of the present invention was 1.9%, and the variation method was 2.2% in the conventional method. , That by the method of the present invention was reduced to 1.6%, respectively. Further, the conventional leak defect rate in the other parts was 11.4%, whereas that in the method of the present invention was 3.9%, and the variation was 2.4%, while it was 4.1%. As a result, the lead time, which is the period from ordering to delivery, has been significantly improved. By the way, when 10 pressure pins were installed, the conventional one required 3 or 4 months,
With the method of the present invention, about two weeks was sufficient.

The reason why such excellent results are obtained is that the method of the present invention is, so to speak, a control method having a learning function, which can significantly reduce the labor required for condition determination of pressurizing timing. Because it was possible.

In the embodiment described above, the potentiometer was used to measure the pressurizing stroke of the pressurizing pin, but the measurement in the method of the present invention is not limited to this. Other measuring means such as an encoder may be used. In short, any device that can accurately measure the moving stroke of the pressure pin can be used. Further, the feedback to the next shot is not limited to the feedback from the previous shot, and the timing of the next shot may be determined from the pressurizing strokes of a plurality of past shots.

(Effects of the Invention) Since the present invention is the method for controlling the timing of pressing the pressure pin configured as described above, the protrusion control of the pressure pin can be accurately performed without any skill. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a system diagram showing a partial cross-section of equipment for implementing the method of the present invention, FIG. 2 is a flow chart diagram, and FIGS. 3 and 4 are graphs showing effects of the method of the present invention. 1,2 …… Die casting mold 3 …… Cavity 4 …… Pressure pin 5 …… Pressure cylinder 9 …… Potentiometer 10 …… Microcomputer

Claims (1)

[Claims] 1. In a die-casting method in which a pressure pin is pushed immediately before solidification of a die-cast casting, the pressure stroke of the pressure pin is measured every shot, and a pressure timing at which a required pressure stroke can be secured from the measured value. And controlling the subsequent pressurizing operation of the pressurizing pin according to the pressurizing timing.