JPH0340658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold clamping safety device for a direct pressure die casting machine.

Conventionally, as this type of mold clamping safety device, for example, the first
There is a structure shown in the figure. To give an overview of this, 1 is a moving platen, 2 is a base platen, 3 is an upper mold, 4 is a lower mold, and 5 is a limit switch mounting plate, and this limit switch mounting plate 5 is attached to the base platen 2 via a bracket 6. There is. Further, 7 is a striker guide, and this striker guide 7 is attached to the moving platen 1 via a bracket 8, and the striker guide 7 includes a striker 9 for mold matching and a striker 10 for mold clamping. are fixed by a striker position adjusting screw 11 and a striker fixing screw 12, respectively. Furthermore, a screw 13 for fine adjustment of the mold clamping striker position is provided between each striker 9 and 10.

According to the above structure, the upper die 3 is first aligned with the lower die 4 by its own weight, and the die alignment limit striker 9 is adjusted using the position adjustment screw so that the limit switch 14 for detecting the die alignment position is turned ON at that position. Adjust at 11. At this time, the fixing screw 12 shall be loosened.

Next, when mold clamping pressure is applied, the tie bars 15 will be extended by about 2 mm. At this time, the position of the mold clamping limit striker 10 is adjusted using the fine adjustment screw 13 so that the mold clamping position detection limit switch 16 is turned on, and the fixing screw 12 is further tightened.

By setting the limit switches 14 and 16 as described above, an interlock is established to confirm the completion of mold clamping. In other words, moving platen 1 after mold clamping pressure is applied.
The position of the mold is detected by the limit switch 16 for detecting the mold clamping position.For example, if the mold thickness of the upper and lower molds increases due to foreign matter such as burrs being caught, the limit switch 16 is activated.
If it turns OFF, stop injection immediately,
Prevents molten metal and high temperature air from blowing out from the parting surface of the mold.

However, according to the above mold clamping safety device,
Displacement due to thermal expansion of the mold is not taken into account, so if the mold thickness increases due to thermal expansion as the number of shots increases and the temperature of the mold rises,
Due to this increase in mold thickness, the position of the mold clamping striker 10 attached to the moving platen 1 is raised compared to when the mold is cold, so that the above-mentioned burrs etc. do not get caught. Regardless, the limit switch 16 for mold clamping position detection is ON.
It will become impossible to operate. Experience shows that this phenomenon always occurs at least once before the mold temperature reaches a steady state, and each time it occurs, it is necessary to fine-tune the position of the mold clamping limit striker 10, which causes the automatic operation of the die-casting machine. This has become one of the major factors hindering this.

In view of the above points, this invention checks the variation in mold thickness (die height) due to thermal expansion of the mold every one molding cycle (one shot), and when the value exceeds the allowable set value, The purpose of this method is to immediately stop injection, assuming that a foreign object such as a burr has been caught, thereby eliminating the influence of a temperature rise in the mold on the accuracy of mold position detection.

That is, in the present invention, as shown in FIG. 3, the position of the moving platen 1 after the mold clamping pressure is generated is detected by the linear scale sensor 20 and stored in the storage device 29 for each molding cycle.
The arithmetic circuit 30 calculates the difference in the position of the moving platen 1 between the (n+1)th and (n+1)th times. Then, the comparison circuit 33 compares this calculation result with a set tolerance value preset in the setting device 28, and if the calculation result exceeds the tolerance value, it is determined that a foreign object such as a so-called burr has been caught. Output circuit 3
2 outputs a stop signal, thereby immediately stopping the injection.

Hereinafter, more specific embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.
As shown in the figure, a linear scale sensor 20 is disposed as a bridge between the fixed platen 17 and the moving platen 1 via brackets 18 and 19, and the sensor body 21 is connected to the fixed platen 17 and the sensor rod 22. One end of each is fixed to the moving platen 1. This linear scale sensor 20 is connected to a microcomputer 23, and the microcomputer 23 has a
20 linear scale sensors per molding cycle
Data regarding the position of the moving platen 1 after the mold clamping pressure is generated, which is detected in the mold clamping pressure, is digitally input. Then, the microcomputer 23 stores the position of the moving platen 1 after the generation of the previous mold clamping pressure, calculates the difference between the position of the moving platen 1 after the generation of the next mold clamping pressure,
It controls the injection operation of the injection cylinder 24 to be stopped only when the value exceeds a preset allowable value. In addition, 25 in FIG. 2 is a mold clamping ram, 26 is a casting sleeve, and 27 is an injection plunger.

Here, the above tolerance value is set by the setting device 28 as shown in FIG. 3, but this tolerance value can be arbitrarily set variably as necessary, and It is designed to be digitally and visually displayed on the display 31 together with the calculation result value of 1.

Next, the operation of the above device will be explained in relation to FIG. 3 as well as a flowchart (FIG. 4) for executing the control.

First, use the setting device 28 to set the allowable value L (approximately 0.1 to 0.5 mm) of mold thickness (die height) variation when a foreign object such as a burr is caught between the upper mold 3 and the lower mold 4. It is input to the RAM of the storage device 29. This allowable value is a value that takes into account the degree of safety such that molten metal does not spout out even if, for example, burrs or the like are caught. On the other hand, the mold thickness increases as the molding cycle (number of shots) is repeated until the mold temperature reaches a saturated state (FIG. 5) due to thermal expansion due to temperature rise of the mold.

After the above-mentioned mold matching and mold clamping, the first
The position H ₁ of the moving platen 1 after the mold clamping pressure is generated for the first time is detected by the linear scale sensor 20 and stored in the storage device 29 . After that, after going through each process of injection, mold opening, and product removal,
The next molding cycle begins again with the mold matching and mold clamping procedure, and the position _H2 of the moving platen 1 after the second mold clamping pressure is detected again by the linear scale sensor 20 and stored in the storage device 29. is memorized.

Next, the difference between the position H ₂ of the moving platen 1 detected for the second time and the position H ₁ detected for the first time.
H ₂ −H ₁ is calculated by the calculation circuit 30, and the calculation result is displayed on the display 31. Then, the comparison circuit 33 compares it with a set allowable value.

Here, if the calculation result is within the initially set allowable value for mold thickness variation, that is, H ₂ −H ₁ ≦L, an injection command is given and the above operation is repeated.
That is, if the difference between the position of the moving platen 1 after the nth mold clamping pressure is generated and the position of the moving platen 1 after the (n+1)th mold clamping pressure is generated is within the tolerance value, injection will be performed. Become.

On the other hand, if the above calculation result exceeds the initially set tolerance value, that is, if H ₂ − _{H 1} >L, it is determined that foreign matter has been caught, such as by a burr, and the output circuit 32 stops the injection. A signal is output and injection is stopped. In this case, after performing processing such as removing burrs, the microcomputer 23 is reset (interlock released), and the program pattern from the first time is followed again.

Here, looking at the relationship between the number of injections and die height variation, microscopically, the relationship between the two is almost linearly proportional as shown in Figures 5 and 6. For example, Assuming that the mold temperature reaches saturation after 50 shots (cycles), the average mold temperature is 100℃, and the cold mold thickness is 1m,
Since the coefficient of thermal expansion of the mold is approximately 10 ^-5 , the mold will expand by approximately 1 mm before the mold temperature reaches saturation. If the above-mentioned proportional relationship between the number of injections and the mold thickness is applied to this amount of elongation, the mold thickness will increase by about 0.02 mm per shot.

However, in the above embodiment, the nth and (n
+1) Since the difference in the position of the moving platen 1 is determined for the second time, it is possible to clearly distinguish between the elongation due to the thermal expansion of the mold and the increase in mold thickness due to foreign matter such as burrs, and therefore the thermal Unlike conventional methods, injection does not stop due to the elongation of the mold due to expansion.

In addition, by setting a separate program for confirming the mold alignment position in addition to the mold clamping limit position confirmation program, when changing the mold, you can simply initialize the allowable value using the setting device 28. No other operations are required.

As is clear from the above description, according to the present invention, it is possible to clearly distinguish mold thickness fluctuations caused by foreign objects such as burrs and mold thickness fluctuations caused by thermal expansion of the mold. Automatic operation will not be stopped due to thermal expansion.

In addition, while the conventional method required complicated limit switch adjustments when changing mold thickness, the present invention requires only the initial setting of the tolerance value, making it easy to adjust the limit switch when changing mold thickness. It also has the advantage of significantly improving performance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of a mold clamping safety device of a conventional direct pressure type die casting machine, FIG. 2 is an explanatory diagram showing an embodiment of the mold clamping safety device according to the present invention, and FIG.
The figure is also an explanatory diagram for explaining the circuit configuration, FIG. 4 is a flowchart for executing control by the above circuit, FIG. 5 is a characteristic diagram showing the relationship between mold thickness change and number of shots, and FIG. The figure is a partially enlarged view of FIG. 5. 1...Moving platen, 3...Upper mold, 4...
...Lower die, 17...Fixed plate, 20...Linear scale sensor, 23...Microcomputer, 2
8...Setter, 29...Storage device, 30...Arithmetic circuit, 33...Comparison circuit.

Claims (1)

[Scope of Claims] 1. A linear scale sensor that is disposed as a bridge between the fixed platen and the moving platen and detects the position of the moving platen after mold clamping pressure is generated in each molding cycle; a setting device for presetting an allowable value for the position; a storage device for storing position data of the moving platen after the n-th and (n+1)-th mold clamping pressure generation based on the output of the linear scale sensor; An arithmetic circuit that calculates the difference in the position of the moving platen after the n-th and (n+1)-th mold clamping pressure is generated, and compares the value of the difference obtained by the arithmetic circuit with the allowable value set by the setting device. A mold clamping safety device for a direct pressure die casting machine, comprising: a comparison circuit, and outputs a signal to stop injection when the value of the difference exceeds an allowable value.