JP2022157641A - Die casting device and die cast manufacturing method - Google Patents

Abstract

To provide a die casting device which can verify an internal quality, which cannot be discovered from outer appearance, in real time, and a die cast manufacturing method.SOLUTION: A die casting device 10 comprises: a position sensor 40 which detects a position of a plunger 17; a head side pressure sensor 41 and a rod side pressure sensor 42 that detect an injection pressure in a sleeve 15; and a controller 50 which controls an extrusion force of the plunger 17. The controller 50 detects a peak pressure of the injection pressure which the plunger 17 generates in a pressure increasing process after completion of injection, detects a position of the injection when the injection pressure reaches the peak pressure, and performs cast product fault occurrence prediction according to an increased pressure distance that the plunger 17 has moved from the injection position after the peak pressure.SELECTED DRAWING: Figure 1

Description

The present invention relates to a die casting apparatus and a die casting manufacturing method.

A die casting apparatus molds a product following the shape of the cavity by injecting molten metal into a cavity formed inside after the fixed die and the moving die are matched. The molten metal extruded from the injection device fills the cavity through the gate. Since the inside of the cavity is filled with gas (air), the cavity is preliminarily opened with a gas venting passage, and by filling the cavity with molten metal, the internal gas is pushed out into the gas venting passage and released to the atmosphere from the gas venting passage. ing.

Generally, in aluminum alloy castings, it is known that during casting, internal voids (porosity) are generated due to solidification shrinkage, centering on the portion where the solidification rate of the molten metal filled in the mold is the slowest. For example, when a member to which compression pressure is applied, such as a cylinder block of an internal combustion engine, is made of an aluminum alloy casting, pressure leakage is likely to occur when the cavities are concentrated and connected to each other. Therefore, in order to improve the yield as a product, it is necessary to suppress the occurrence of blowholes of a scale that leads to pressure leakage.

Patent Document 1 describes a position sensor that detects the position of a plunger that is slidable in a sleeve that communicates with a mold, an injection pressure sensor that detects the injection pressure applied by the plunger to a molding material in the sleeve, and a control device. and the control device includes a gate arrival point specifying unit that specifies a gate arrival point in time when the plunger reaches a predetermined gate arrival time position as injection progresses, based on the detection value of the position sensor; a filling start time identifying unit that identifies a filling start time at which the injection pressure exceeds a predetermined filling start pressure as the injection progresses within a predetermined monitoring period including the gate arrival time based on the detected value of the pressure sensor; , is described. The injection device described in Patent Document 1 is said to be able to suitably specify the start of filling of the molding material.

In Patent Document 2, there is a recess measurement unit that measures the amount of recesses generated in the appearance feature part of the surface of the casting, and the correlation between the amount of recesses generated measured by the recess measurement unit and the amount of blowholes generated inside the casting. and an estimating unit for estimating the amount of blowhole occurrence based on the relationship. The blowhole tendency management device described in Patent Document 2 is said to be capable of estimating the amount of blowhole occurrence in a short period of time and with high accuracy.

JP 2019-150861 A Japanese Patent Application Laid-Open No. 2016-68100

However, in the apparatuses of Patent Documents 1 and 2, although the casting conditions are managed, it cannot be said that the management conditions and the traceability of defective products have been established.
In terms of the conditions for certain defective products, they are discharged (discarded) by a die-cast machine, but the current situation is that even products that meet these conditions are outflowing as defective products. One of the reasons why the quality of high-pressure die-cast products cannot be established is that they cannot be detected from the casting conditions.
Not only the injection conditions, but also the cooling conditions of the mold, the amount of mold release agent applied, the dilution ratio, the amount of injection lubrication applied, etc. are stored as much data as possible. Attempts have been made to extract it, but the results have not been satisfactory.

One of the causes of blowholes is insufficient pressurization due to the fact that the pressure is not transmitted to the product even when the die casting apparatus is pressurizing normally.
Also, the method of detecting the pressure inside the mold is possible in experiments, etc., but it is not durable for mass production and cannot be used at present.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a die-casting apparatus and a die-casting manufacturing method that enable real-time verification of internal quality that cannot be detected from the appearance.

In order to solve the above problem, the die casting apparatus according to claim 1 comprises a fixed mold and a movable mold, and a plunger sliding inside a sleeve in a cavity formed by the fixed mold and the movable mold. A die-casting device that injects molten metal by an extrusion force to form a cast product, comprising position detection means for detecting the position of the plunger, injection pressure detection means for detecting the injection pressure in the sleeve, and the plunger and a control device for controlling the extrusion force of the plunger, wherein the control device detects the peak pressure of the injection pressure generated in the pressure increasing process after the injection of the plunger is completed, and when the injection pressure reaches the peak pressure and detecting the injection position of the case, and predicting the occurrence of defects in the cast product according to the pressure increase distance that the plunger has moved from the injection position after the peak pressure.

According to the present invention, it is possible to provide a die-casting apparatus and a die-casting manufacturing method that enable real-time verification of internal quality that cannot be detected from the outside.

It is a figure showing the whole die-casting machine composition concerning the embodiment of the present invention. It is a figure explaining the injection process and injection waveform of the die-casting apparatus which concern on embodiment of this invention. FIG. 3 is a diagram showing the notation of each part of the injection process and the injection waveform of FIG. 2 in the form of a table of terms; It is a figure explaining the position of speed curve, pressure curve, and injection in the injection process of the die-casting device concerning the embodiment of the present invention. 5 is an enlarged view showing the velocity curve, pressure curve, location of injection, and peak pressure location for the injection process of FIG. 4; FIG. 4 is a flowchart showing a die casting pressure transmission failure determination process of the die casting apparatus according to the embodiment of the present invention; It is a figure which shows the example of actual measurement of the die-casting pressure transmission failure determination of the die-casting apparatus which concerns on embodiment of this invention. It is a flowchart which shows the die-casting pressure transmission failure determination process of the die-casting apparatus of the modification of embodiment of this invention.

Next, a die-casting apparatus and a die-casting manufacturing method according to embodiments of the present invention will be described in detail with appropriate reference to the drawings. This embodiment is an example applied to a high pressure die casting machine. In addition, in each figure, the same code|symbol is attached|subjected to the common part and the overlapping description is abbreviate|omitted.
(embodiment)
FIG. 1 is a diagram showing the overall configuration of a die casting apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the die casting apparatus 10 includes a fixed mold 11, a movable mold 12, and a cavity 13 formed between the fixed mold 11 and the movable mold 12 as a mold.
The fixed mold 11 is provided with a molten metal supply portion 14. The molten metal supply portion 14 includes a tubular sleeve 15, a molten metal supply port 16 opening at the upper portion of the base end side of the sleeve 15, and the sleeve 15. and a plunger 17 as a press member that can freely move back and forth and slides along the inner peripheral surface of the. The plunger 17 has a plunger tip 17a slidable in the sleeve 15 in the front-rear direction, and a plunger rod 17b having a tip fixed to the plunger tip 17a.

The tip of the sleeve 15 communicates with the runner 18 . A runner 18 extends inside the movable mold 12 and is connected to the cavity 13 through a gate 19 . The gate 19 introduces into the cavity 13 the molten metal (hereinafter referred to as the molten metal 20 ) made of aluminum or an aluminum alloy extruded from the sleeve 15 which is the molten metal injection part.
A molten metal 20 is supplied into the sleeve 15 from a ladle 21 through a molten metal supply port 16 , and the molten metal 20 is injected into the cavity 13 through a gate 19 by pushing out a plunger 17 .

(Injection drive unit 30)
Plunger 17 is actuated by injection drive 30 .
The injection drive unit 30 is of a hydraulic type, and has an injection cylinder 32 that drives the plunger 17 and an injection control drive unit 33 that supplies hydraulic fluid (oil, for example) to the injection cylinder 32 . Specifically, the injection drive unit 30 includes an injection piston 31, an injection cylinder 32, and an injection control drive unit 33 for executing the injection/filling process, a pressure boosting piston 34 for executing the pressure boosting process, and a large-diameter piston. , a piston rod 37 , and a connecting portion 38 that mechanically connects the plunger rod 17 b and the piston rod 37 .
The injection control drive unit 33 supplies hydraulic fluid to the injection cylinder 32 and the like. The pressure increase control drive unit 36 supplies hydraulic fluid to the pressure increase cylinder 35 and the like.

Specifically, the injection control drive section 33 and the pressure increase control drive section 36 are hydraulic devices. The hydraulic system includes, for example, a tank for storing hydraulic fluid, a pump (hydraulic pressure source) capable of delivering hydraulic fluid from the tank, an accumulator (hydraulic pressure source) capable of discharging the accumulated hydraulic fluid, and these and injection cylinders 32, and a plurality of valves (not shown) for controlling the flow of hydraulic fluid in the plurality of flow paths.

In this hydraulic device, the hydraulic fluid contained in the tank is supplied by the pump to the accumulator through the corresponding flow path and the corresponding valve, thereby accumulating pressure in the accumulator. Further, for example, the injection piston 31 moves forward by supplying the hydraulic fluid from the accumulator to the head-side chamber 32h via the corresponding flow path and the corresponding valve. In addition, the corresponding valve is a pressure-compensated flow control valve (flow rate adjustment valve) and also a servo valve. The speed of the plunger 17) is controlled.
Further, pressure is increased by the pressure increasing piston 34 by supplying hydraulic fluid from the accumulator to the rear side chamber 32e via the corresponding flow path and the corresponding valve.

An oil chamber is formed between the injection piston 31 and the pressure boosting piston 34, and predetermined pressurized oil is supplied to the injection control drive section through openings 32a and 35a in the injection cylinder 32 and the pressure boosting cylinder 35, respectively. 33, and is supplied from a drive unit 36 for pressure increase control.

A piston rod 37 is arranged within the injection cylinder 32 . The inside of the injection cylinder 32 is divided into a rod-side chamber 32r on the side from which the piston rod 37 extends and a head-side chamber 32h on the opposite side. By selectively supplying hydraulic fluid to the rod-side chamber 32r and the head-side chamber 32h, the injection piston 31 slides in the injection cylinder 32 in the front-rear direction.

The injection cylinder 32 and the pressure-increasing cylinder 35 are cylindrical bodies having a circular internal cross-sectional shape, and the pressure-increasing cylinder 35 is formed to have a larger diameter than the injection cylinder 32 .

The booster piston 34 has a small-diameter portion 34a that can slide inside the rear end portion of the injection cylinder 32 (the head-side chamber 32h in the illustrated example), and a large-diameter portion 34b that can slide inside the booster cylinder 35. is doing. The inside of the pressure increasing cylinder 35 is partitioned into a front chamber 35f on the side of the injection cylinder 32 and a rear chamber 35e on the opposite side by the large diameter portion 34b.

Therefore, when the front side chamber 35f is depressurized, the pressure intensifying piston 34 moves backward due to the difference between the working area of the small diameter portion 34a in the head side chamber 32h and the working area of the large diameter portion 34b in the rear side chamber 35e. It is possible to apply a higher pressure to the hydraulic fluid in the head-side chamber 32h than the pressure received from the hydraulic fluid in the side chamber 35e. As a result, the pressure increasing cylinder 35 exhibits a pressure increasing function.

The injection cylinder 32 is arranged coaxially with respect to the plunger 17 . The piston rod 37 is connected to the plunger 17 via a connecting portion 38 . The injection cylinder 32 and the boosting cylinder 35 are fixedly provided to a mold clamping device (not shown) or the like. Movement of the injection piston 31 relative to the injection cylinder 32 advances or retracts the plunger 17 (plunger tip 17 a ) within the sleeve 15 .

(Position and speed detection of plunger 17)
A position sensor 40 (position detection means) for detecting the position of the plunger 17 is installed on the plunger rod 17b, and outputs a position detection signal S-1 to a controller 50 (control device). A position sensor 40 detects the position of the piston rod 37 relative to the injection cylinder 32 and indirectly detects the position of the plunger 17 . For example, the position sensor 40 may be fixedly provided on the piston rod 37 and constitute a magnetic or optical linear encoder together with a scale portion (not shown) extending in the axial direction of the piston rod 37. A laser length measuring device that measures the distance to a member fixed to the piston rod 37 may be used.
The position sensor 40 and the controller 50 can obtain (detect) the speed of the plunger 17 by differentiating the detected position of the plunger 17 .

(Calculation of pressure applied to molten metal 20 by plunger 17)
The injection cylinder 32 is provided with a head side pressure sensor 41 (injection pressure detection means) for detecting the pressure in the head side chamber and a rod side pressure sensor 42 (injection pressure detection means) for detecting the pressure in the rod side chamber. , and outputs detection signals S-2 and S-3 to the controller 50. FIG.
The head-side pressure sensor 41 and rod-side pressure sensor 42 of the injection cylinder 32 detect the pressure applied by the plunger 17 to the molten metal, such as the pressure (injection pressure) applied by the plunger 17 to the molten metal 20 when injecting the molten metal 20 into the cavity 13, for example. is used to indirectly detect The controller 50 controls the detection value of the head side pressure sensor 41, the detection value of the rod side pressure sensor 42, the pressure receiving area in the head side chamber 32h of the injection piston 31, the pressure receiving area in the rod side chamber 32r of the injection piston 31, the plunger 17 The pressure applied by the plunger 17 to the molten metal 20 can be calculated based on the area of contact with the molten metal.

(controller)
The controller 50 includes a CPU 51 , a memory 52 , an input circuit 53 and an output circuit 54 .
The CPU 51 reads a control program stored in ROM or EEPROM (Electrically Erasable Programmable Read-Only Memory), which is an electrically rewritable non-volatile memory, expands it in RAM, performs injection control, and manages die casting forging conditions. The program 52a is executed to predict failure occurrence (see FIG. 6). The CPU 51 outputs a control signal (control command) for controlling each part through an output circuit 54 based on an input signal inputted through the input circuit 53 .
The memory 52 is composed of a ROM, a RAM, an EEPROM, etc. containing programs for various processes. The memory 52 includes an external storage device such as a hard disk drive (HDD). The memory 52 stores control programs including a die casting forging condition management program 52a.

The controller 50 detects the peak pressure of the injection pressure generated in the pressure increasing process after the plunger 17 completes the injection, detects the injection position when the injection pressure reaches the peak pressure, and stops the plunger 17 at the peak pressure. Later, the occurrence of defects in the casting product is predicted according to the pressure increase distance moved again from the injection position. The distance that the plunger 17 moves again from the injection position after the peak pressure is the pressure increase distance that the plunger 17 advances following solidification shrinkage during cooling of the molten metal 20 .

The controller 50 predicts the occurrence of defects when the pressure increase distance that the plunger 17 has moved again from the injection position after the peak pressure is greater than or equal to the solidification shrinkage distance preset based on the solidification shrinkage rate of the molten metal. conduct.
The controller 50 determines that a defect including blowholes has occurred when the pressure increasing distance is less than the solidification shrinkage distance preset based on the solidification shrinkage rate of the molten metal.
If the pressure increase distance is less than a preset solidification shrinkage distance based on the solidification shrinkage rate of the molten metal, or if the pressure increase distance is equal to or greater than a predetermined abnormality determination value, an abnormality is detected. It is determined that
The controller 50 predicts the occurrence of defects in the cast product according to the pressure increase distance that the plunger 17 moves again within a predetermined time from the injection position after the peak pressure.

The input circuit 53 receives an input signal from an input device 55 such as a keyboard or a mouse, a position signal S-1 from the position sensor 40, a signal S-2 from the head side pressure sensor 41, and a signal from the rod side pressure sensor . S-3 is entered.
The output circuit 54 outputs a signal (for example, a display signal for displaying on the display section 56) for outputting the prediction result and the like. Further, the output circuit 54 has a driver for driving a pump electric motor provided in a hydraulic device (not shown) that constitutes the injection control drive section 33 and the pressure increase control drive section 36. A control signal to the electric motor and an opening/closing drive signal to each valve are output via this driver.

(Overview of Die Casting Operation of Die Casting Device 10)
2A and 2B are diagrams for explaining the injection process and the injection waveform of the die casting apparatus 10. FIG. The horizontal axis of FIG. 2 indicates the time t, and the right side indicates later time. The vertical axis on the left side of FIG. 2 indicates the injection speed (the speed of the plunger 17), and the higher the value, the higher the value. The vertical axis on the right side of FIG. 2 indicates the injection pressure (plunger position), and indicates that the higher the position, the closer to the fixed mold 11 and the movable mold 12 .
The velocity curve shows the change in injection velocity over time. A pressure curve shows the change in injection pressure over time.

FIG. 3 is a diagram showing the notation of each part of the injection process and the injection waveform of FIG. 2 in the form of a table of terms. Reference characters a to p in FIG. 2 correspond to reference characters a to p in FIG. 3, respectively.
The low speed injection time a is the time during which the injection piston 31 moves at a low speed.
The high-speed injection time b is the time during which the injection piston 31 moves at high speed.
The low-speed injection acceleration time c is the time from when the injection piston 31 starts to move until it reaches the set low-speed injection speed.
The high-speed injection acceleration d is the time required to reach the set high-speed injection speed from the low-speed injection speed.

The charging pressure rise time e is the time from when the injection piston 31 completes filling the cavity 13 with the molten metal 20 until the pressure applied to the injection piston 31 reaches the accumulator set pressure.
The pressure increase time lag f is the time from when the injection piston 31 completes filling the cavity 13 with the molten metal 20 to when the injection piston 31 starts to move.
The pressure increase time g is the time from when the pressure increase piston 34 starts to move until it reaches the pressure increase output from the filling output.
The pressure increase time h is the time from when the injection piston 31 completes filling the cavity 13 with the molten metal 20 to when the pressure increase piston 34 completes its operation.

The low speed injection pressure i is the pressure within the injection piston 31 when the injection piston 31 is moving forward at low speed.
The high speed injection pressure j is the pressure applied to the injection piston 31 during high speed injection.
The filling completion pressure k is the pressure in the injection cylinder 32 before the injection piston 31 completes filling the cavity 13 with the molten metal 20 and the injection piston 31 starts moving.
The boost pressure l is the pressure in the injection piston 31 when the injection piston 31 has completed its movement.
The boosting surge pressure m is the surge pressure generated in the injection piston 31 when the boosting piston 34 starts moving.

The low speed injection speed n is the jet speed of the first stage in the injection process.
High injection speed o is the highest injection speed during the injection process.
The high speed average injection speed p is the average speed at which the injection piston moves at high speed.

The die casting apparatus 10 sequentially performs low-speed injection (time points t0 to t1), high-speed injection (time points t1 to t2), pressure increase (time points t3 to t4), and pressure holding (after time point t4). A series of operations from low-speed injection to holding pressure may be called one shot.

<Low speed injection: t0 to t1>
In the initial stage of injection, air entrainment by the molten metal 20 is suppressed by performing low-speed injection (see t0 to t1 in FIG. 3) in which the plunger 17 is advanced at a relatively low speed.
Immediately before the start of low-speed injection, the die casting apparatus 10 is in the state shown in FIG. That is, the injection piston 31 and the boosting piston 34 of the injection cylinder 32 are positioned at initial positions such as the retraction limit. The position D of the plunger 17 at this time is indicated by position D0 in FIG. 4 described later.

The controller 50 determines whether or not a predetermined injection start condition is satisfied, and starts low-speed injection when it is determined that the condition is satisfied. Specifically, the controller 50 opens the corresponding valve to supply the working fluid from the accumulator to the head side chamber 32h, and opens the corresponding valve to allow the working fluid to be discharged from the rod side chamber 32r. The conditions for starting injection include completion of mold clamping of the fixed mold 11 and movable mold 12 and completion of supply of the molten metal 20 to the sleeve 15 by the ladle 21 .

The speed of the plunger 17 during low-speed injection is feedback controlled based on the speed of the plunger 17 detected by the position sensor 40, for example.
The speed of the plunger 17 is, for example, a constant slow injection speed. The value of the low speed injection speed is appropriately set by the operator via the input device 55 . The injection pressure during low-speed injection is maintained at a relatively low pressure because the injection speed is relatively low.

<High-speed injection: t1 to t2>
Subsequently, high-speed injection (see t1 to t2 in FIG. 3) is performed to move the plunger 17 forward at a relatively high speed, so that the molten metal 20 is rapidly injected into the fixed mold 11 and the movable mold without delaying the solidification of the molten metal 20. It is filled in mold 12 .
When a predetermined high-speed switching condition is satisfied, the controller 50 switches the speed of the plunger 17 to a high-speed injection speed higher than the low-speed injection speed to perform high-speed injection. Specifically, the controller 50 increases the opening of the corresponding valve while supplying the hydraulic fluid from the accumulator to the head-side chamber 32h following the low-speed injection. The injection pressure during high speed injection is higher than the injection pressure during low speed injection.

The high speed switching condition is, for example, that the plunger 17 has reached a predetermined high speed switching position D1 (see FIG. 4). The controller 50 may determine whether the high-speed switching condition is satisfied based on the detected value of the position sensor 40 or the elapsed time from the start of injection.

When control is switched from low-speed injection to high-speed injection during high-speed injection (time points t1 to t2), the injection pressure rises once, then drops, rises again, and drops again. After that, as the molten metal 20 fills the fixed mold 11 and the movable mold 12, the injection pressure rises rapidly. The injection speed also decreases once after switching to high-speed injection and before the end of high-speed injection.

<Deceleration injection: t2-t3>
When the cavity 13 is filled with the molten metal 20 to some extent, the plunger 17 receives reaction force from the filled molten metal 20 and is decelerated, while the injection pressure rises sharply as shown in FIG. To go. Appropriate deceleration control may be performed, such as reducing the opening of the corresponding valve when a predetermined deceleration start condition is satisfied, such as when the plunger 17 reaches a predetermined deceleration position. Deceleration control mitigates the impact at the time of completion of filling.

When injections including low speed injections and high speed injections are performed, the high speed switching position is generally set to be the position when the melt 20 reaches the gate 19 . Further, when the molten metal 20 is filled in the fixed mold 11 and the movable mold 12, the injection speed drops sharply and the injection pressure rises sharply, as shown in FIG.

<Pressure increase: t3 to t4>
(see t1 to t2) of the molten metal 20) so that the fixed mold 11 and the movable mold 12 are quickly filled with the molten metal 20 without delaying the solidification of the molten metal 20, and then the pressure of the molten metal 20 is increased. A pressure increase (see t3 to t4 in FIG. 3) is performed.

The controller 50 determines whether or not a predetermined pressure increase start condition is satisfied, and if it is determined that the condition is satisfied, starts pressure increase. Specifically, for example, the controller 50 first opens the corresponding first valve when the first condition is satisfied. As a result, hydraulic fluid is supplied from the accumulator to the rear side chamber 32e, and the pressure boosting piston 34 starts moving forward. Next, when the second condition is satisfied, the controller 50 sets the degree of opening of the corresponding second valve to that for pressure increase. That is, the controller 50 ends speed control and starts pressure control. The discharge of the hydraulic fluid from the head-side chamber 32h is prohibited by the self-closing of the valve, which is a pilot type check valve. Through such operations, the injection pressure rises and reaches a predetermined casting pressure (final pressure).
As shown in FIG. 2, the injection pressure is kept constant while the pressure is increased.

<Holding pressure: t4~>
Holding pressure (see t4 onward in FIG. 3) is performed to maintain the increased pressure. This reduces sink marks on the molded product.
After increasing the pressure, the controller 50 keeps the injection pressure at the final pressure. During this time, the molten metal cools and solidifies. When the molten metal solidifies, the controller 50 stops the supply of hydraulic pressure from the accumulator to the rear side chamber 32e and ends the holding pressure. After that, the mold is opened and the casting product is extruded.
The outline of the die casting operation of the die casting apparatus 10 has been described above.

(Explanation of principle)
Casting conditions have been managed for a long time, but it cannot be said that the management conditions and the traceability of defective products have been established.
One of the reasons why the quality of die-cast products cannot be established is that the occurrence of blowholes, which cannot be detected by appearance, cannot be detected from the casting conditions.
Not only the injection conditions, but also the cooling conditions of the mold, the amount of mold release agent applied, the dilution ratio, the amount of injection lubrication applied, etc. are stored as much data as possible. Attempts have been made to extract it, but so far there has been no satisfactory result.
One of the causes of blowholes is defective pressurization due to the fact that the pressure is not transmitted to the product even when the die casting apparatus is pressurizing normally.

The method of detecting the pressure inside the mold is possible in experiments, but it is not durable for mass production and cannot be used at present.

In the 16 injection items (items a to p in FIG. 3) shown in FIGS. 2 and 3, pressure transmission to the die-cast product could not be detected. How much pressure is transmitted to the molten aluminum 20 was not controlled at all at the stage of mass production. The present invention determines how much pressure is transmitted to the molten aluminum 20 without adding a new detection member. Incidentally, how much pressure is applied to the molten metal 20 can be determined by providing an expensive sensor for detecting pressure on the mold. However, the sensor for detecting the high-temperature, high-pressure molten metal 20 is very expensive, has low durability, and becomes unusable after several tens of shots.

The inventors devised a technique for detecting pressure transmission to a die-cast product by calculating a new control value from injection data.

As shown in FIGS. 2 and 3, in die casting injection, there is a pressurization step after high speed injection. By this high-speed injection, the molten aluminum 20 is filled and then pressurized to crush the cavities. If the pressure transmission of the increased pressure is sufficient, the injection position moves slowly forward after the high-speed injection, and the pressure is transmitted to the product portion. In the slow advance, the molten metal 20 solidifies and shrinks as it cools, but at that time, the injection position (the position of the plunger 17) advances and follows. It was known that the injection position moved slowly forward, but no attention was paid to the amount of chasing (following amount).

The present inventors paid attention to the fact that the molten aluminum 20 shrinks when it solidifies, so that its volume is reduced to 0.92 (6/1000 reduction).

That is, the molten aluminum 20 solidifies and shrinks to reduce its volume to 0.92, and the injection rises by the amount of contraction and advances. For this reason, the amount equal to or greater than the amount of contraction becomes the boosting pressure transmission effect.

The 0.92 reduction in the amount of solidification shrinkage is balanced by slow advance of pressure increase. However, if the slow advance of the pressure increase is the same as the amount of solidification shrinkage, no pressure is transmitted to the molten metal 20 even if pressure is applied mechanically. It can be determined that it has not been transmitted. This makes it possible to determine whether the product is good or bad.
Although the slow advance distance has characteristics depending on each model, if the pressurized advance distance is equal to or less than the minimum amount of solidification shrinkage (6/1000), it can be determined as a defective product. According to actual measurements made by the present inventors, it has been found that a 0.92 reduction in the amount of solidification shrinkage requires an advance of about 2%.

Next, the effects of the die casting machine 10 configured as described above will be described.
FIG. 4 is a diagram for explaining speed curves, pressure curves, and injection positions in the injection process of the die casting apparatus 10 based on the above basic principle. FIG. 5 is an enlarged view showing the velocity curve, pressure curve, location of injection, and peak pressure location for the injection process of FIG. In FIG. 4, the physical quantities indicated by the horizontal and vertical axes are the same as in FIG. The horizontal axis of FIG. 4 indicates time t, and the right side indicates later time. The vertical axis on the left side of FIG. 4 indicates the injection speed (the speed of the plunger 17), and the higher the value, the higher the value. The vertical axis on the right side of FIG. 4 indicates the injection pressure and the position D of the plunger 17, and indicates that the higher the position, the closer to the fixed mold 11 and the movable mold 12. As shown in FIG. The velocity curve shows the change in injection velocity over time. A pressure curve shows the change in injection pressure over time. The thick dashed line in FIG. 4 indicates the change over time of the injection position, that is, the position D of the plunger 17. When the plunger 17 is at its most retracted position, the injection position is D=0.

As shown in FIGS. 4 and 5, the position of the plunger 17 (the stop position of the plunger 17) when the injection pressure in the sleeve 15 reaches the peak P is D2, and the time at this time is t11. Here, the trigger for this die casting pressure transmission failure determination is the injection pressure peak P, and the injection position is detected by taking data from the position of the plunger 17 .

As explained in the principle above, during injection, movement is observed within a predetermined time (eg, 5 seconds) after the peak pressure of the plunger 17 . The post-movement position within a predetermined time is D3, and the time at this time is t12.

After the plunger 17 completes injection, a peak pressure is generated when the pressure increasing process begins. That is, as shown in FIGS. 4 and 5, starting from time t11 when the injection pressure in the sleeve 15 is at peak P, the distance D3 moved in 5 seconds indicated by the thick line in FIGS. Calculate the volume of the part (see symbol q in FIG. 4).

FIG. 6 is a flow chart showing the die casting pressure transmission failure determination process of the die casting apparatus. This flow is a casting management program by the CPU 51 of the controller 50 in FIG. This flow is executed for each shot.
This program is started when the power of the die casting machine 10 is turned on.
The controller 50 detects the position of the plunger 17 in step S1.
The controller 50 detects (calculates) the speed of the plunger 17 in step S2.
In step S3, the controller 50 detects the peak P of the injection pressure with the head-side pressure sensor 41 (see FIG. 1) inside the injection cylinder 32. FIG.
In step S4, the controller 50 determines whether or not it has been ejected. If not ejected, return to START.
If so, the controller 50 detects the injection position in step S5. The injection position (see the thick dashed lines in FIGS. 4 and 5) is detected by a position sensor 40 (see FIG. 1).

In step S6, the controller 50 determines whether or not the injection pressure has reached the injection peak pressure. If the injection pressure does not reach the peak pressure (mold preheating and casting), the process returns to step S5.
When the injection pressure reaches the peak pressure, the controller 50 detects the injection position in step S7. The injection pressure until the injection pressure reaches the peak P takes various pressure curves depending on the casting conditions (the pressure curve in FIG. 4 is an example). However, no matter what pressure curve is taken, there is a peak P of the injection pressure (in injection, a heavy object is stopped rapidly, so the peak occurs due to inertia), so this injection pressure peak P is Can be used as a starting point.

Incidentally, in the conventional die casting apparatus, the speed curve and the pressure curve until reaching time t11 in FIG. There is no example of using data from time t11 to time t12 (up to the injection position), and the present inventors disclose it for the first time.

In step S8, the position (pressure increase distance) of the plunger 17 after a predetermined time (for example, 5 seconds) is detected.

In step S9, occurrence of blowholes is predicted based on the distance that the plunger 17 has moved after the peak pressure. Specifically, the controller 50 converts the distance (mm) moved again after the stop into volume, and determines that it is defective when the change in volume is 0.92 (6/1000) or less. However, since the slow-moving distance has different characteristics depending on the model, it is better to obtain the slow-moving distance of each model by actual measurement in advance, store it in the memory 52, and correct it using the correction value for each model. good.

A more detailed description will be given of the determination of defective products with a pressurization advance distance equal to or less than the amount of solidification shrinkage.
The following equations (1) to (3) are used as parameters.
Increased pressure distance = Injection movement distance for 5 seconds from peak injection pressure P (1)
Solidification shrinkage = casting weight x (1 - solidification shrinkage rate) (2)
Shrinkage follow-up = solidification shrinkage/injection cross section (3)
The increased pressure distance is detected from the injection position (the position of the plunger 17). The solidification shrinkage and shrinkage follow-up are obtained in advance by actual measurement.

Further, the formula (4) is obtained from the above formulas (1) to (3). An example of actual measurement using the pressing distance of formula (4) will be described later with reference to FIG.
Increased pressure distance - solidification shrinkage = increased pressure distance (4)

In this manner, the molten aluminum 20 solidifies and shrinks, so that the plunger 17 is pushed forward by an injection amount of 0.92 shrinkage. The amount of contraction or more becomes the boosting pressure transmission effect. In other words, when the plunger 17 does not move a distance exceeding the set distance, it can be determined that a defect including a blowhole has occurred.

Returning to the flow of FIG. 6, in step S10, the controller 50 determines whether or not the pressure increase distance is abnormally large (whether the pressure increase distance is equal to or greater than a predetermined abnormality determination value).
If the pressure increase distance is not abnormally large (S10: No), it is either <good product zone> or <blowhole zone> (see Fig. 7), and the <good product zone> or <blowhole zone> is determined. Therefore, in step S11, the controller 50 determines whether or not the pressure increase distance is equal to or less than the solidification contraction distance.

If the pressure increase distance is greater than the solidification shrinkage distance (S11: No), it is <non-defective product zone> (see FIG. 7), and in step S12, the controller 50 outputs a normal determination result and terminates the processing of this flow. .
If the pressure increase distance is equal to or less than the solidification shrinkage distance (S11: Yes), it is <blow zone> (see FIG. 7), and in step S13, the controller 50 outputs the blow hole prediction result and executes the processing of this flow. finish.
The normality determination result and the blowhole prediction result can be output to, for example, the display unit 56, output to a printer (not shown), external output via a communication unit (not shown), and saving of the prediction result to an external storage device. be.

If the pressure increase distance is abnormally large in step S10 (S10: Yes), it is <burr zone> (see FIG. 7), and in step S14, the controller 50 outputs a burr prediction abnormality result and executes the processing of this flow. finish.

FIG. 7 is a diagram showing an actual measurement example of the die casting pressure transmission failure determination of the die casting apparatus. The vertical axis indicates the pressing distance for each shot shown in Equation (4), and the horizontal axis indicates the number of shots with 20 shots as one unit. The example of FIG. 7 shows a casting example of 533 shots.
Based on the pressurization distance shown in Fig. 7, a <non-defective zone> corresponds to the case where the pressure increase distance is greater than the solidification shrinkage distance, and a <blow zone> corresponds to the case where the pressure increase distance is less than or equal to the solidification shrinkage distance. , and <Bali zone>, which corresponds to the case where the pressure increase distance is abnormally large.
In FIG. 7, the pressurized distance of 3.0 indicated by symbol r in FIG. 7 is the non-defective product line in the <non-defective product zone>. In each shot, the pressurized distance is a casting that generally satisfies the control conditions (not a defective product) (see step S12 "normality judgment result" in the flow of FIG. 6).

A pressurization distance of 0.0 indicated by symbol s in FIG. 7 is the defective product determination region (<blowhole zone>). This pressurized distance of 0.0 is an example when solidification shrinkage is assumed to be 0 in formula (3). For example, in FIG. 7, the increased pressure at shot numbers near 20, 58, and 96 (see symbol t in FIG. 7) falls within the defective product determination region, and is determined to be defective in increased pressure transmission (see FIG. 6). See flow step S13 "Blow hole prediction result"). In this case, the product is dispensed (excluded) as a defective product.
Here, when the increased pressure transmission failure occurs frequently in each shot, it is suspected that the injection parts are deteriorated, so measures such as replacement of the injection parts are taken. The non-defective product/defective product determination result shown in FIG. 7 is reflected in the outputs in steps S12, S13, and S14 of the flow in FIG.

In the actual measurement example of die casting shown in FIG. 7, when the pressure distance is large (for example, in the vicinity of shot 153) (see symbol u in FIG. 7), there is a possibility that molten aluminum leaks out of the mold and burrs occur. (Refer to step S14 "burr prediction abnormality result" in the flow of FIG. 6). The occurrence of burrs is caused by pressure release from the mold, and there is a possibility that the pressure is not transmitted to the product. In general, the hot water area is good, but the internal quality cannot be guaranteed. In other words, there is a possibility of poor pressure transmission to the product although the flow of hot water is good. In addition, as problems after burrs are generated, there are problems such as burrs being caught in the mold and causing mold collapse, defects being caused by being caught in the product, and burrs interfering with the air discharge inside the mold. It can also be used as a basis for making maintenance decisions.

[Modification]
FIG. 8 is a flow chart showing the die casting pressure transmission failure determination process of the die casting apparatus according to the modification of the present embodiment. Steps that perform the same processing as in FIG. 6 are denoted by the same reference numerals.
In FIG. 8, if the pressure increase distance is greater than the solidification shrinkage distance in step S11 (S11: No), occurrence of blowholes is predicted based on the distance that the plunger 17 moves after the peak pressure is reached in step S21.
In step S22, the controller 50 outputs the prediction result and terminates the processing of this flow.
If the pressure increase distance is abnormally large in step S10 (S10: Yes), or if the pressure increase distance is less than the coagulation contraction distance in step S11 (S14: Yes), the controller 50 outputs an abnormal result in step S23. to terminate the processing of this flow.
In this way, any method may be executed at any timing as long as it includes the step of predicting the occurrence of blowholes based on the distance that the plunger 17 has moved after the peak pressure.

[effect]
As described above, the die casting apparatus 10 of this embodiment includes the fixed mold 11 and the movable mold 12, and slides inside the sleeve 15 in the cavity 13 formed by the fixed mold 11 and the movable mold 12. A die-casting device that injects a molten metal 20 by an extrusion force of a plunger 17 to mold a cast product, and includes a position sensor 40 that detects the position of the plunger 17 and a head-side pressure sensor 41 that detects the injection pressure in the sleeve 15. and a rod side pressure sensor 42, and a controller 50 for controlling the pushing force of the plunger 17. The controller 50 detects the peak pressure of the injection pressure generated in the pressure increasing process after the plunger 17 reaches the peak pressure, and detects the peak pressure of the injection pressure. The injection position is detected when the injection pressure reaches the peak pressure, and after the plunger 17 stops, the occurrence of defects in the casting product is predicted according to the pressure increase distance moved from the injection position.

In the past, it was the current situation that defective products were generated by visual confirmation and pressure leak inspection after processing. The present invention enables verification of internal quality that cannot be discovered on the outside. That is, it is possible to predict the occurrence of blowholes without checking the cast product after machining. In addition, the occurrence of burrs can be detected and used as a criterion for inspection and maintenance of molds.

The ability to discover internal defects in the casting process has the following unique effects.
1. Since defective products can be found during production, countermeasures such as equipment can be taken on the spot, and the occurrence of defective products in subsequent processes can be reduced.

2. By discharging defective products, it is possible to reduce processing defects and prevent defective products from flowing to subsequent processes.

3. It is possible to improve the internal quality, and if the casting product is a vehicle part, it contributes to the prevention of oil leakage after delivery of the completed vehicle.

4. According to the present invention, by calculating a new control value from the injection data, occurrence of blow holes can be predicted without adding a new member. Therefore, it can be applied to general purpose at low cost.

5. Since it is possible to determine how much pressure is being transmitted to the molten aluminum without providing an expensive sensor, it can be applied to general purposes at low cost.

Further, in the die casting apparatus 10, the controller 50 predicts the occurrence of defects when the pressure increase distance is equal to or less than the solidification shrinkage distance preset based on the solidification shrinkage rate of the molten metal.

Thus, if the pressure increase distance is less than or equal to the solidification shrinkage distance, there is a possibility that a defect will occur. By predicting the occurrence of defects with priority when there is a possibility of occurrence of defects, it is possible to speed up processing and effectively utilize processing resources. That is, real-time processing can be performed at a low cost, and occurrence of defects can be predicted in real time for each shot.

Further, in the die casting apparatus 10, the controller 50 determines that defects including blowholes have occurred when the pressure increase distance is equal to or less than the solidification shrinkage distance preset based on the solidification shrinkage rate of the molten metal.

Thus, it is assumed that an abnormality occurs when the pressure increase distance is equal to or less than the solidification shrinkage distance. Defective products such as the occurrence of blowholes can be determined in real time.

Further, in the die casting apparatus 10, the controller 50 determines that when the pressure increasing distance is equal to or less than the solidification shrinkage distance set in advance based on the solidification shrinkage rate of the molten metal, or is equal to or greater than a predetermined abnormality determination value, Judged as abnormal.

By doing so, it is possible to quickly predict product defects due to the occurrence of burrs, in addition to determining defective products such as the occurrence of blowholes.

Further, in the die casting apparatus 10, the controller 50 predicts the occurrence of defects in the cast product according to the pressure increase distance that the plunger 17 has moved within a predetermined time from the injection position after the peak pressure.

By doing so, it is possible to shorten the time until the prediction determination is completed by using the distance traveled within the predetermined time. In addition, since processing is completed in real time, it can be executed as background processing. Therefore, it is possible to improve the workability by shortening the time in the manufacturing process such as a manufacturing line.

The embodiments described above show examples of embodying the present invention. Therefore, the technical scope of the present invention should not be construed to be limited by these. This is because the present invention can be embodied in various forms without departing from its gist or its main characteristics.
For example, it can be similarly applied to a casting method having an injection function such as squeeze casting, hot chamber die casting, hybrid full casting, and the like.

REFERENCE SIGNS LIST 10 die casting device 11 fixed mold 12 movable mold 13 cavity 14 molten metal supply part 15 sleeve 17 plunger 17a plunger tip 17b plunger rod 18 runner 19 gate 20 molten metal (metal molten metal)
30 Injection drive unit 33 Injection control drive unit 36 Pressure increase control drive unit 40 Position sensor (position detection means)
41 head side pressure sensor (injection pressure detection means)
42 rod side pressure sensor (injection pressure detection means)
50 controller (control device)
P: Peak pressure position D3: Increased pressure distance S6: Step of detecting the peak pressure of the injection pressure generated in the pressure increasing process after the plunger completes injection S7: Steps of detecting the injection position when the injection pressure reaches the peak pressure S9, S21 A step of predicting the occurrence of defects in casting products according to the pressure increase distance that the plunger has moved from the injection position after the peak pressure

Claims (6)

A die-casting apparatus comprising a fixed mold and a movable mold, and molding a cast product by injecting molten metal into a cavity formed by the fixed mold and the movable mold by the extrusion force of a plunger sliding in a sleeve. and
position detection means for detecting the position of the plunger;
injection pressure detection means for detecting the injection pressure within the sleeve;
A control device that controls the pushing force of the plunger,
The control device is
detecting the peak pressure of the injection pressure generated in the pressure increasing process after the plunger completes injection, and detecting the injection position when the injection pressure reaches the peak pressure;
A die-casting apparatus, wherein, after the plunger reaches a peak pressure, a defect occurrence prediction for the cast product is performed according to a pressure increase distance that the plunger has moved from the injection position. The control device is
2. The die casting apparatus according to claim 1, wherein when the pressure increase distance is equal to or less than a solidification shrinkage distance preset based on the solidification shrinkage rate of the molten metal, occurrence of defects is predicted. The control device is
When the pressure increase distance is equal to or less than a solidification shrinkage distance set in advance based on the solidification shrinkage rate of the molten metal, it is determined that a defect including the occurrence of a blowhole has occurred. Die casting equipment as described. The control device is
Abnormal if the pressure increase distance is less than or equal to the solidification shrinkage distance preset based on the solidification shrinkage rate of the molten metal, or if the pressure increase distance is greater than or equal to a predetermined abnormality judgment value. The die casting apparatus according to claim 1, characterized in that it is determined that: The control device is
detecting the peak pressure of the injection pressure generated in the pressure increasing process after the plunger completes injection, and detecting the injection position when the injection pressure reaches the peak pressure;
2. The die casting apparatus according to claim 1, wherein, after the pressure reaches a peak, the plunger predicts the occurrence of defects in the cast product according to the pressure increase distance that the plunger has moved within a predetermined time from the injection position. A die-casting apparatus comprising a fixed mold and a movable mold, and molding a cast product by injecting molten metal into a cavity formed by the fixed mold and the movable mold by the extrusion force of a plunger sliding in a sleeve. A die casting manufacturing method of
The die casting device is
a step of detecting a peak pressure of the injection pressure generated in a pressure increasing process after the plunger completes injection;
detecting the position of the injection when the injection pressure reaches a peak pressure;
A die casting manufacturing method, comprising: predicting the occurrence of defects in the cast product according to the pressure increase distance that the plunger has moved from the injection position after the peak pressure.

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