JP2022090725A - Quality management method for die cast product - Google Patents

Abstract

To provide preventive management by the change prediction of casting quality and life prediction till mechanical loss by detecting a subtle change in the initial state before a step in which a casting defect or mechanical loss is generated.SOLUTION: A timing of detecting a change in the sliding resistance between a plunger tip and an injection sleeve is suitably selected from a state in which a molten metal is not present and a state in which a molten metal is present in accordance with the purpose of quality management. Further, the sliding resistance is calculated and digitized from a control command value of an injection control device having high resolution powder and quality discrimination is performed, and further, the number of times of quality discrimination is counted to increase prediction precision and to ensure preventive management.SELECTED DRAWING: Figure 3

Description

The present invention relates to a quality control method for a cast product in a die casting machine or the like.

In casting by a die casting machine, the molten metal supplied to the inside of the injection sleeve is injected and filled into the mold cavity by the forward operation of the plunger tip set to a predetermined injection speed and casting pressure.

However, the injection sleeve is heated by the high-temperature molten metal and thermally deformed, the sliding resistance between the injection sleeve and the plunger tip increases, and the movement of the plunger tip may become unstable. Further, the sliding resistance may fluctuate greatly due to the adhesion of the molten metal residue obtained by solidifying the molten metal into the injection sleeve. Further, due to the wear of the plunger tip, the gap between the plunger tip and the injection sleeve becomes large, the insertion of the molten metal increases, and the accumulation of the molten metal residue is promoted, and as a result, the sliding resistance may fluctuate even more.

These large fluctuations in sliding resistance result in fluctuations in injection speed and casting pressure, causing the molten metal to undulate during injection filling, inducing casting defects such as air entrainment (mixed voids), hot water wrinkles, and hot water circulation. do. In addition, the molten metal residue accumulated in the injection sleeve is peeled off and mixed with the molten metal, which causes new casting defects such as cavities and foreign matter contamination.
Furthermore, due to frequent casting defects and increased wear of the plunger tip and injection sleeve, which hinders the normal operation of the die casting machine, the casting operation is stopped due to restoration work such as parts replacement, and productivity is greatly reduced. (Loss of opportunity).

Here, since the starting point of casting defects, opportunity loss, etc. is the change in the sliding resistance between the injection sleeve and the plunger tip, it is proposed to accurately detect the change in the sliding resistance. Furthermore, it is desirable to combine the prediction of changes in casting quality and the prediction of life until opportunity loss, which leads to quality control (preventive management) that stabilizes the quality of cast products and obtains stable operation of casting operation.
For example, in Patent Document 1 and Patent Document 2, changes in sliding resistance are detected from changes in the operating hydraulic pressure (casting pressure) of a hydraulic cylinder or the like that controls a plunger tip in the injection filling process. Further, Patent Document 3 states that a change in sliding resistance is detected from a change in the moving speed (injection speed) of the plunger tip in the injection filling process.

Special Publication No. 60-292 Japanese Unexamined Patent Publication No. 3-32460 Japanese Unexamined Patent Publication No. 2-306667

In order to realize preventive management by predicting changes in casting quality and life prediction up to mechanical loss, it is preferable to detect changes in sliding resistance at the timing according to the purpose.
For example, in the preventive management of casting defects such as cavities and foreign matter contamination, the plunger tip and the injection sleeve come into direct contact with each other as the detection timing in order to accurately grasp the formation, accumulation and peeling of the molten metal residue. It is correct to do it without molten metal. That is, the injection filling process is completed, and the plunger tip is retracted within the range of the retracting operation in preparation for the next shot.
Further, even when the degree of wear of the plunger tip or the injection sleeve is grasped, it can be detected with high accuracy by performing the detection timing within the range of the retracting operation of the plunger tip in the state where there is no molten metal.
On the other hand, the detection timings shown in Patent Documents 1 to 3 are said to be performed within the range of the forward operation of the plunger tip for injecting and filling the molten metal into the mold cavity. Due to the presence of the molten metal, it contains disturbance factors such as thermal deformation of the injection sleeve due to the high temperature molten metal, heating softening of the molten metal residue, and the weight of the molten metal, so that the inspection accuracy of only the molten metal residue is greatly reduced. This is an unfavorable condition for preventive management of casting defects such as cavities and foreign matter contamination.

In addition, in the preventive management of casting defects such as air entrainment, hot water wrinkle defects, and hot water circulation defects caused by fluctuations in the injection speed and casting pressure in the injection filling process, the timing to detect is the plunger tip in which the molten metal exists. It is correct to do it within the range of forward movement.
Here, in the detection means shown in Patent Documents 1 to 3, it is assumed that the detection is performed at the timing of the forward movement of the plunger chip having the molten metal, but the sensor is arranged and arranged in the drive unit such as the hydraulic cylinder corresponding to the downstream of the control. It is said that fluctuations in injection speed and casting pressure will be measured based on the signal information from the sensor. Therefore, it is difficult to completely solve problems such as errors due to temperature changes in hydraulic oil and false positives due to sensor failure. Furthermore, when the injection speed and casting pressure fluctuate, the quality of the cast product has already fluctuated, and it cannot be said to be preventive management.

The present invention has been made in view of the above problems, and a small change in sliding resistance, which is an initial state before the stage where casting defects and opportunity loss occur, is caused by the backward operation and forward operation of the plunger tip. Quality control of castings in die casting machines, which aims to preventive management by combining prediction of changes in casting quality and prediction of life up to machine loss by selecting and detecting the detection timing according to the purpose. It's about the method.

The present invention presents the present invention as a first means for solving the above problems.
The molten metal is supplied to the inside of the injection sleeve at the standby position after the retracting operation of the plunger tip placed in the injection sleeve, and the injection filling of the molten metal is completed in the mold cavity at the injection completion position after the forward operation of the plunger tip. It is a quality control method for die-cast castings.
A detection section is set within the moving range of the retracting motion of the plunger tip, and the sliding resistance between the plunger tip and the injection sleeve in the detection section is continuously collected and compared with the sliding resistance at the time of casting a good product collected in advance. A sliding resistance discriminating device for discriminating the quality of the sliding resistance for each shot during actual casting is provided, and the quality of the actual cast product for each shot is discriminated based on the evaluation result of the sliding resistance discriminating device. ..
According to the first means described above, preventive management can be performed by accurately predicting changes in casting quality and signs of opportunity loss by directly detecting sliding resistance in the absence of molten metal.

The present invention is, as a second means for solving the above-mentioned problem, in the first means.
The detection section will be in the range from the injection completion position to the standby position.
According to the above-mentioned second means, by accurately detecting the state of the molten metal residue in the injection sleeve and the wear state of the plunger tip and the injection sleeve, preventive management of casting defects such as cavities and foreign matter contamination can be performed, and suddenly. Preventive management can be ensured to avoid machine loss due to production suspension.

The present invention, as a third means for solving the above problem, in any one of the first or second means.
The sliding resistance is to be a control command value of the electrically controlled hydraulic servo valve system that controls the forward movement and the backward movement of the plunger tip.
According to the above third means, disturbance factors such as oil temperature changes and sensor failures are eliminated, and even small changes in the initial state before the stage where mechanical abnormalities such as casting defects and wear occur are accurately detected. Therefore, the accuracy of preventive management can be improved.

The present invention, as a fourth means for solving the above problem, in any one of the first or third means.
Further, the collection of sliding resistance in the forward operation of the plunger tip is provided, and the detection section is arbitrarily set within the range of the injection completion position starting from the standby position.
According to the fourth means, by detecting the sliding resistance in the presence of the molten metal, it is possible to prevent and manage casting defects such as air entrainment, hot water wrinkle defects, and hot water circulation defects caused by the injection filling operation.

The present invention relates to any one of the first to fourth means as a fifth means for solving the above problem.
The sliding resistance discriminating device displays the position of the plunger tip in the detection section and the control command value as a waveform, and obtains the total area of the waveform that deviates by superimposing the good product waveform at the time of good product casting and the casting waveform at the time of actual casting. The purpose is to determine the quality of the actual cast product for each shot by comparing with the determination reference area set in advance.
According to the fifth means, the prediction accuracy can be improved and the preventive management can be performed with high accuracy by quantifying the change of casting quality and the sign of opportunity loss. Furthermore, by identifying the abnormal part of the injection sleeve and making planned arrangements for replacement parts by predicting the replacement time, it is possible to minimize the mechanical loss due to the sudden suspension of production.

The present invention relates to any one of the first to fifth means as a sixth means for solving the above problem.
When the quality of the actual casting is judged to be negative, the sliding resistance discriminator issues a caution alarm and starts accumulating the number of caution alarms. At the same time, it is to send a danger warning.
According to the sixth means, the quality of the cast product is stabilized and the casting is performed by separating the cast product for each shot (non-defective product, inspection required product, defective product) and quantifying the change in casting quality and the sign of opportunity loss. Preventive management of stable operation can be performed.

According to the present invention, it is possible to accurately detect subtle changes in the initial state before the stage where casting defects and opportunity loss occur, and based on the detection results, the signs of changes in casting quality and opportunity loss are quantified. The predicted quality control method ensures that the quality of the casting is stabilized and the preventive control of the stable operation of the casting operation is ensured.

It is a conceptual diagram of the injection device of the die casting machine of this invention. It is a waveform diagram which shows the sliding resistance in a plunger tip retracting operation. It is a processing flow diagram in a plunger chip retreat operation. It is a waveform diagram which shows the sliding resistance in the plunger tip forward movement. It is a flow diagram of the process in the plunger tip retreat operation. It is a block diagram of the sliding resistance discriminating device.

Embodiments of the present invention will be described in detail with reference to the drawings.
(Outline configuration of die casting machine)
The die casting machine 1 shown in FIG. 1 has a fixed mold 2 supported by a fixed plate (not shown), a movable mold 3 supported by a movable plate (not shown) and capable of advancing and retreating with respect to the fixed plate 2, and injection of molten metal. The device 10 includes an injection control unit 20 that controls the operation of the injection device 10, and a sliding resistance discriminating device 30 that includes a part of the processing module of the injection control unit 20.
A cast product is manufactured by injecting and filling molten metal such as aluminum or an aluminum alloy toward the mold cavity 4 between the fixed mold 2 and the movable mold 3 by the injection device 10.

(Injection device)
The injection device 10 includes an injection sleeve 11 to which molten metal is supplied to the inside, a plunger tip 12 capable of advancing and retreating with respect to the injection sleeve 11 inside the injection sleeve 11, a plunger rod 13 connected to the plunger tip 12, and a plunger. It is provided with a drive source such as a hydraulic cylinder 14 that is connected to the rod 13 to drive the plunger tip 12.
Regarding the movement of the plunger tip 12 of the injection device 10, the movement toward the side F near the mold cavity 4 is defined as "forward movement", and the movement toward the side B far from the mold cavity 4 is "backward movement". , The completion position of the retracting motion of the plunger tip 12 is defined as the “standby position BE”, and the completion position of the forward motion of the plunger tip 12 is defined as the “injection completion position FE”. That is, the plunger tip 12 advances and retreats in the front-rear direction D1 between the standby position BE and the injection completion position FE.

(Injection sleeve)
The injection sleeve 11 is a cylindrical body that is horizontally supported in a state of projecting rearward from a fixed plate (not shown). The axial direction of the injection sleeve 11 coincides with the front-rear direction D1. The front side of the injection sleeve 11 penetrates the fixing plate so as to communicate with the mold cavity 4, and is fastened to a predetermined position of the fixing mold 2.
The rear side of the injection sleeve 11 is provided with a pouring port 15 having a through hole. While the plunger tip 12 is waiting at the standby position BE, molten metal is poured into the inside of the injection sleeve 11 from a hot water supply device or the like (not shown) through the pouring port 15.
The injection sleeve 11 is provided with a cooling mechanism (not shown) including a flow path through which a cooling medium such as water flows, if necessary. Further, in order to prevent wear damage of the plunger tip 12, stabilize the sliding state, suppress adhesion of molten metal residue, and the like, it is preferable to apply a lubricant to the sliding surface of the injection sleeve 11 and the plunger tip 12.

(Plunger tip)
The plunger tip 12 has a columnar shape in which the molten metal in the injection sleeve 11 is pushed forward and injected and filled in the mold cavity 4, and has an appropriate gap from the injection sleeve 11. That is, the molten metal does not leak, the injection sleeve 11 and the plunger tip 12 do not stick to each other, and the gap is precisely adjusted so that the plunger tip 12 can smoothly advance and retreat. The plunger rod 13 is an intermediate body that connects the plunger tip 12 and the hydraulic cylinder 14, and transmits the drive of the hydraulic cylinder 14 to the plunger tip 12.
Further, the plunger tip 12 is provided with a water cooling mechanism including a flow path through which a cooling medium such as water flows.

(Injection control device)
The injection control device 20 is connected to the hydraulic cylinder 14 and controls the drive of the hydraulic cylinder 14 to control the forward movement or the backward movement of the plunger tip 12 via the plunger rod 13. In particular, the forward operation of the plunger tip 12 is an operation of injecting and filling the molten metal in the injection sleeve 11 into the mold cavity 4, and is therefore an important operation that directly affects the quality of the cast product.
The injection filling operation includes the forward speed (injection speed) of the plunger tip 12 set in multiple stages and the filled mold cavity 4 in order to accurately fill the molten metal in the injection sleeve 11 into the mold cavity 4. It is composed of casting pressures set in multiple stages in order to accurately cool and solidify the molten metal inside. Therefore, it is preferable to use as the injection control device 20 a control device equipped with an electrically controlled hydraulic servo valve system that is optimal for high-precision control of injection speed and casting pressure set in multiple stages.

(Sliding resistance discriminator)
The sliding resistance discriminating device 30 calculates the sliding resistance of the plunger tip 12 and the injection sleeve 11 from the information of the control command value of the injection control device 20 that controls the drive of the hydraulic cylinder 14, and determines the quality. .. As shown in FIG. 2, the sliding resistance discrimination device 30 includes a signal input unit 31, a waveform display unit 32, a detection section setting unit 33, a calculation unit 34, a discrimination unit 35, and an alarm transmission unit 36.

Here, a sensor is placed in a drive unit such as a hydraulic cylinder located downstream of the control, and based on the signal information from the placed sensor, fluctuations in injection speed and casting pressure are measured to detect changes in sliding resistance. It is difficult to completely solve problems such as error due to temperature change of hydraulic oil and false detection due to sensor failure by the above means (casting detection). Furthermore, when the injection speed and casting pressure fluctuate, the quality of the cast product has already fluctuated, and it cannot be said to be preventive management.

On the other hand, in the present invention, by using the control command value of the injection control device 20 which is the most upstream of the control, it is possible to realize highly accurate change of the sliding resistance without problems such as error and false detection. .. In addition, by being able to accurately detect even minute changes in sliding resistance at the stage before the abnormal phenomenon of fluctuations in injection speed and casting pressure occurs, it is possible to detect early before the stage where mechanical abnormalities such as casting defects and wear occur. Preventive management can be performed at the stage of.

Further, the timing for detecting the sliding resistance in the series of operations of the casting operation is set in advance by the sliding resistance discriminating device 30.
For example, in preventive management of casting defects such as cavities and foreign matter contamination, there is a high probability that the plunger tip 12 and the injection sleeve 11 will come into direct contact with each other in order to accurately grasp the formation, accumulation and peeling of the molten metal residue. It is assumed that it is detected in the absence of. Further, even when grasping the degree of wear of the plunger tip 12 and the injection sleeve 11, it is preferable that there is no molten metal. That is, it is correct to set the range of the retracting operation of the plunger tip 12 in preparation for the next shot after the injection filling process is completed.
Further, in the preventive management of casting defects such as air entrainment, hot water wrinkle defect, and hot water circulation defect caused by fluctuations in injection speed and casting pressure in the injection filling process, gold is generated by the forward operation of the plunger chip 12 in the state where the molten metal is present. It is set within the range of injection filling of the molten metal into the mold cavity 4.
In this way, by detecting changes in sliding resistance at the timing according to the purpose, preventive management by predicting changes in casting quality and life prediction up to machine loss is ensured.

(Waveform of sliding resistance: during backward movement)
A procedure for detecting sliding resistance at the timing of the retracting operation of the plunger tip 12 and performing preventive management will be described with reference to FIGS. 3 and 4.
FIG. 3 shows the waveform of the retracting motion of the plunger tip 12 after finishing the injection filling and preparing for the next casting shot. When the signal input unit 31 of the sliding resistance discriminating device 30 receives the control command value of the injection control unit 20, the waveform display unit 32 displays it as a control command value waveform.
On the horizontal axis of the waveform, either the position of the plunger tip 12 or the elapsed time from the start of retreat can be selected. For example, when it is desired to identify an abnormal portion of the injection sleeve 11, it is preferable to select the position of the plunger tip 12. The range from the injection completion position FE of the plunger tip 12 to the standby position BE is displayed.

The vertical axis of the waveform is the control command value of the injection control device 20, and represents the sliding resistance between the plunger tip 12 and the injection sleeve 11 in the retracting operation.
Here, by using the injection control device 20 as a control device equipped with an electrically controlled hydraulic servo system, the resolution of the control command value from the injection control device 20 becomes high, and even a small change in sliding resistance can be detected with high accuracy. can. As a result, even a small change in the initial state before the stage where an abnormal phenomenon such as a casting defect or wear occurs can be accurately detected, so that it is possible to accurately predict a change in casting quality and a life until mechanical loss.
The electrically controlled hydraulic servo system is a control device capable of precisely controlling the flow rate of hydraulic oil in a hydraulic device such as a hydraulic cylinder. The flow rate control of the hydraulic oil is performed at the position of the adjustment rod called the spool, and the position of the spool is driven by the connected servomotor.
Therefore, as the control command value 20, the "spool position control current value" for the servomotor that drives the spool position is used. Alternatively, if the control device has a function of monitoring the position of the spool, it is preferable to select "spool monitor display value" for the control command value 20.

The broken line of the waveform in FIG. 3 is the waveform of the sliding resistance (reference value waveform 301) at the time of casting a non-defective product collected in advance. In FIG. 3, it is represented by a single broken line for easy understanding, but waveform data at the time of casting a plurality of non-defective products may be accumulated and represented within the range at the time of casting a non-defective product including the upper and lower limits. Alternatively, the waveform data when a casting defect occurs may be used as a limit value, and this limit value or the limit value may be multiplied by a safety factor to show a safety range in which a good product casting is surely obtained. Alternatively, the data acquired during no-load operation after maintenance such as disassembly and cleaning may be used.

Next, from the waveform displayed by the waveform display unit 32, the range for evaluating the sliding resistance according to the purpose is set by the detection section setting unit 33 as the detection section 302.
For example, in the case of preventive management of casting defects such as cavities and foreign matter contamination, the range in which molten metal residue that causes casting defects may be generated, deposited and peeled off is set. That is, since there is a possibility that the entire range in contact with the molten metal in the injection sleeve 11 is possible, it is preferable to set the entire range from the injection completion position FE to the standby position BE.
Further, when performing preventive management by detecting damage such as local wear in the injection sleeve 11 or loosening of mechanical parts of the injection device 10 including the hydraulic cylinder 14 and the plunger rod 13, from the injection completion position FE. It is preferable to set the entire range of the standby position BE. If the abnormal part is known in advance, it is possible to narrow down the setting to a local range including the abnormal part.

The solid line of the waveform shown in FIG. 3 is the waveform of the sliding resistance of the backward operation in one shot of the actual casting during continuous operation (waveform 303 during actual casting). By overwriting and displaying the reference value waveform 301 and the reference value waveform 301, the presence or absence of the deviation between the reference value waveform 301 and the actual casting waveform 303 and the degree of the deviation become clear.
The calculation unit 34 uses a method such as binarization processing to sum up the areas of the dissociated portions of the overwritten waveform in the range of the detection section 302 set by the detection section setting unit 33 (enclosed by the shaded areas in FIG. 3). The area) is quantified as the deviation area 303a, and the data is transmitted to the discrimination unit 35.
The determination unit 35 receives the data transmitted from the calculation unit 34, compares it with a preset determination reference area, determines whether the quality of the cast product of one shot of actual casting is good or bad, and predicts the quality of the cast product of the next shot. I do. During continuous operation, by continuously performing this information processing flow, quality discrimination and quality prediction of the cast product for each actual casting shot during continuous operation are continuously performed. As a result, changes in casting quality can be converted into data, and changes in casting quality after the next shot can be predicted and life can be predicted up to mechanical loss.

Here, the determination reference area is an area obtained by accumulating waveform data at the time of casting a plurality of non-defective products and multiplying the area having a width indicated by the upper and lower limits at the time of casting a non-defective product by a safety factor. Alternatively, it is an area indicating a safety range in which a good product casting is surely obtained by multiplying this limit value or the limit value by a safety factor with the waveform data when a casting defect occurs due to the peeling of the molten metal residue as a limit value. That is, it is before the state where casting defects such as cavities and foreign matter mixed in the molten metal residue have already occurred, or the state where there is a suspicion of mechanical loss in the injection device such as the plunger tip 12 or the injection sleeve 11. By making a judgment at the time of a slight change in the stage, it is possible to prevent an abnormal situation such as a mixture of defective products with non-defective products or suspension of production.

Further, the discrimination unit 35 can predict the quality of the cast product of the next actual casting shot by using the data of the maximum value 303b of the deviation between the reference value waveform 301 and the actual casting waveform 303. For example, the waveform when a clear casting defect or mechanical loss occurs is set as the reference value waveform 301, and when it is detected that the maximum value 303b exceeds the maximum value of the reference value waveform 301, the discriminating unit 35 suddenly Abnormality can be instantly identified as a situation occurs, and fatal machine loss such as production suspension can be prevented. Alternatively, the average value of the upper and lower limits at the time of good product casting obtained by accumulating data at the time of casting a plurality of good products is set as the reference average value 303c, and the number of times that the numerical value of the waveform of one shot of actual casting exceeds the standard average value 303c is counted. By doing so, it is possible to predict the tendency of fluctuations in the quality of the cast product and the life of the casting to mechanical loss.

(Processing flow: Backward operation)
FIG. 4 shows a processing flow of the sliding resistance discriminating device 30 in the retracting operation of the plunger tip 12. When the casting of the injection filling is completed, the hydraulic cylinder 14 is driven by the injection control unit 20, the plunger tip 12 starts the retreating operation at a set speed, and the retreating operation stops when the plunger tip 12 reaches the standby position BE. ..

The control command value from the injection control unit 20 in the entire range from the backward start (injection complete position FE) to the backward stop (standby position BE) is displayed as a waveform on the waveform display unit 32 via the signal input unit 31 (waveform measurement). ). The waveform of the detection section 302 set by the detection section setting unit 33 is extracted, digitized by the calculation unit 34, and then discriminated by the discrimination unit 35 (waveform analysis).

The discrimination unit 35 performs a two-step discrimination process. In the first-stage discrimination process, for example, the deviation area 303a is calculated by comparing the two waveforms of the reference value waveform 301 and the actual casting waveform 303 in the range of the detection section 302 (analysis result B1). The analysis result B1 is compared with the preset determination reference area (reference value A1), and if A1 ≦ B1, it is determined that “inspection is required”, and the information of the determination result is sent to the alarm transmission unit 36. At the same time that the alarm transmitting unit 36 emits an alarm, the counting of the number of alarm signals from the discriminating unit 35 is started.
In addition, the inspection required is a slight change in sliding resistance that makes us hesitate to clearly predict the quality of the casting of the next shot, and the casting is temporarily stored and the next shot. After confirming the discrimination result, the quality is judged again.
When the determination result of the determination unit 35 is A1> B1, the cast product is stored as a non-defective product determination C1 and continuous casting is continued.

Further, in the alarm transmitting unit 36, if the counted alarm number E1 is compared with the preset reference number D1 and D1 ≦ E1, the alarm transmitting unit 36 transmits the abnormality determination G1 and the continuous casting operation. (Second stage discrimination process).
This abnormality determination G1 indicates that the probability of obtaining a good product is extremely reduced even if continuous casting is continued, and the casting conditions for injection filling such as injection speed and casting pressure are reviewed, and the injection sleeve 11 is used. It is suggested that the injection device 10 including the plunger tip 12 and the like should be cleaned and maintained. Alternatively, there is a high probability that a fatal mechanical loss such as a failure of the injection device 10 will occur, which suggests that maintenance measures such as parts replacement are required at an early stage.
In this way, stable production can be continued by predicting small changes in casting quality and injection equipment by counting the number of alarms, and systematically readjusting the casting conditions and performing simple maintenance of the injection equipment. In addition, it is possible to predict the occurrence of fatal mechanical loss such as failure of the injection device, which ensures preventive management such as advance arrangement of replacement parts.
Here, the reference number of times D1 is preferably set in combination with the reference value A1 depending on the content of the required preventive management. For example, when the highest priority is to stabilize the casting quality, the reference value A1 is strict and the reference number D1 is set small.
If the discrimination result of the discrimination unit 35 is D1> E1, continuous casting is continued, but the cast product is temporarily stored as an inspection required, and the quality is judged again after the discrimination result of the next shot is confirmed. ..

(Sliding resistance waveform: forward movement)
A procedure for detecting sliding resistance at the timing of the forward movement of the plunger tip 12 and performing preventive management will be described with reference to FIGS. 5 and 6.
FIG. 5 is a waveform of overwriting of sliding resistance in the injection filling process. Since the waveform display, arithmetic processing, and the like from the control command value are the same as those in FIG. 3, the parts different from those in FIG. 3 will be mainly described.
On the horizontal axis of the waveform, either the position of the plunger tip 12 or the elapsed time from the start of injection can be selected. The standby position BE is the position of the plunger tip 12 for pouring the molten metal into the injection sleeve 11 from the pouring port 15. Further, the injection completion position FE is a forward position where the plunger tip does not advance any further after the injection filling process is completed.
The vertical axis of the waveform is the control command value of the injection control device 20, and represents the sliding resistance between the plunger tip 12 and the injection sleeve 11 in the forward operation. The difference from FIG. 3 is the sliding resistance including the state in which the molten metal flows in the injection sleeve 11 and the mold cavity 4 due to the forward movement of the plunger tip 12 in the state where the molten metal is present in the injection sleeve 11. expressed. As a result, a small change in the sliding resistance of the injection filling process represents a slight change in the quality of the cast product related to the injection filling process, and preventive management can be performed by predicting the change in casting quality. Furthermore, the accuracy of preventive management is improved by using the control command value of the electrically controlled hydraulic servo system.

As shown in FIG. 5, the injection filling step is a combination of a range of injection speed control that combines low-speed injection and high-speed injection, and a range of high-pressure filling casting pressure control that increases the filling pressure and reliably compensates for the solidification shrinkage of the molten metal. It is common.
The broken line of the waveform shown in FIG. 5 is the waveform of the sliding resistance (reference value waveform 401) at the time of casting a non-defective product collected in advance. In FIG. 5, it is represented by a single broken line for easy understanding, but waveform data at the time of casting a plurality of non-defective products may be accumulated and represented within the range at the time of casting a non-defective product including the upper and lower limits. Alternatively, the waveform data when a casting defect occurs may be used as a limit value, and this limit value or the limit value may be multiplied by a safety factor to show a safety range in which a good product casting is surely obtained.

The detection section 402 is selected and set according to the purpose of detection and the like. For example, when casting defects related to the injection flow of the molten metal such as air entrainment, hot water wrinkle defects, and hot water circulation defects become problems, two sections of low-speed injection and high-speed injection are set. Further, when it is desired to grasp the cooling and solidification process of the molten metal such as cavities and sink marks, it is preferable to set two ranges of high-speed injection and high-pressure filling. If it is desired to confirm all defects including foreign matter contamination, the entire range from the standby position BE to the injection completion position FE may be set. In FIG. 5, the section of low-speed injection in which the fluctuation of the sliding resistance is likely to be large and the casting defect is likely to be induced is set as the detection section 402.

The solid line of the waveform shown in FIG. 5 is the waveform of the sliding resistance of the forward movement in one shot of the actual casting during continuous operation (waveform 403 during actual casting). By overwriting and displaying the reference value waveform 401 and the reference value waveform 401, the presence or absence of the deviation between the reference value waveform 401 and the actual casting waveform 403 and the degree of the deviation become clear.
The calculation unit 34 uses a method such as binarization processing to sum up the areas of the dissociated portions of the overwritten waveform in the range of the detection section 402 set by the detection section setting unit 33 (enclosed by the shaded area in FIG. 5). The area) is quantified as the deviation area 403a), and the data is transmitted to the discrimination unit 35.
The determination unit 35 receives the data transmitted from the calculation unit 34, compares it with a preset determination reference area, determines whether the quality of the cast product of one shot of actual casting is good or bad, and predicts the quality of the cast product of the next shot. I do. During continuous operation, by continuously performing this information processing flow, quality discrimination and quality prediction of the cast product for each actual casting shot during continuous operation are continuously performed. As a result, changes in casting quality can be converted into data, and changes in casting quality after the next shot can be predicted and life can be predicted up to mechanical loss.

Here, the determination reference area is an area obtained by accumulating waveform data at the time of casting a plurality of non-defective products and multiplying the area having a width indicated by the upper and lower limits at the time of casting a non-defective product by a safety factor. Alternatively, it is an area indicating a safety range in which a good product casting is surely obtained by multiplying this limit value or the limit value by a safety factor with the waveform data when a casting defect due to injection filling occurs as a limit value. That is, in a state where the casting quality has already been affected by fluctuations in the injection speed and casting pressure, or in an injection device such as a plunger tip 12 or an injection sleeve 11 due to thermal deformation of the injection sleeve or rubbing against molten metal residue. By making a judgment at the time of a slight change in the stage before the suspected mechanical loss, it is possible to prevent abnormal situations such as mixing of defective products with non-defective products and suspension of production. Can be done.

Further, the discriminating unit 35 can predict the quality of the cast product of the next actual casting shot by using the data of the maximum value 403b of the deviation between the reference value waveform 401 and the actual casting waveform 403. For example, the waveform when a clear casting defect or mechanical loss occurs is set as the reference value waveform 401, and when it is detected that the maximum value 403b exceeds the maximum value of the reference value waveform 401, the discriminating unit 35 suddenly Abnormality can be instantly identified as a situation occurs, and fatal machine loss such as production suspension can be prevented. Alternatively, the average value of the upper and lower limits at the time of non-defective casting obtained by accumulating data at the time of casting a plurality of non-defective products is set as the reference average value 403c, and the number of times the value of the waveform of one actual casting shot exceeds the standard average value 403c is counted. By doing so, it is possible to predict the tendency of fluctuations in the quality of the cast product and the life of the casting to mechanical loss.

So far, the range of low-speed injection has been described as the detection section 402, but the same applies even if the range of the detection section is changed. The entire range from low-speed injection to high-pressure filling may be collectively determined. Alternatively, the determination can be made by classifying each range, and prioritizing the determination in consideration of the form of casting defects, concerns about mechanical loss, and the like.

(Processing flow: During forward operation)
FIG. 6 shows a processing flow of the sliding resistance discriminating device 30 in the forward operation of the plunger tip 12. The molten metal is poured into the injection sleeve 11, and the plunger tip 12 starts from the state of waiting at the standby position BE.
When the injection filling process starts, the hydraulic cylinder 14 is driven by the injection control unit 20, and the plunger tip 12 moves forward at the set injection speeds and casting pressures of low speed injection, high speed injection, and high pressure filling, and the mold cavity 4 When the injection filling of the molten metal into the inside is completed, the forward operation of the plunger chip 12 is stopped at the injection completion position FE.

The control command value from the injection control unit 20 in the entire range from the injection start (standby position BE) to the injection stop (injection completion position FE) is displayed as a waveform on the waveform display unit 32 via the signal input unit 31 (waveform measurement). ). The waveform of the detection section 302 set by the detection section setting unit 33 is extracted, digitized by the calculation unit 34, and then discriminated by the discrimination unit 35 (waveform analysis).

The discrimination unit 35 performs a two-step discrimination process. In the first-stage discrimination process, for example, the deviation area 403a is calculated by comparing the two waveforms of the reference value waveform 401 and the actual casting waveform 403 in the range of the detection section 402 (analysis result B2). The analysis result B2 is compared with the preset determination reference area (reference value A2), and if A2 ≦ B2, it is determined that “inspection is required”, and the information of the determination result is sent to the alarm transmission unit 36. At the same time that the alarm transmitting unit 36 emits an alarm, the counting of the number of alarm signals from the discriminating unit 35 is started.
The inspection required is a slight change in sliding resistance that makes it hesitant to clearly judge the quality of the cast product. The cast product is temporarily stored, and after confirming the judgment result of the next shot. The quality is judged again.
When the determination result of the determination unit 35 is A2> B2, the cast product is stored as a non-defective product determination C2, and continuous casting is continued.

Further, in the alarm transmitting unit 36, if the counted alarm number E2 is compared with the preset reference number D2 and D2 ≦ E2, the alarm transmitting unit 36 transmits the abnormality determination G2 and the continuous casting operation. (Second stage discrimination processing).
This abnormality determination G2 indicates that the probability of obtaining a good product is extremely reduced even if continuous casting is continued, and the casting conditions for injection filling such as injection speed and casting pressure are reviewed, and the injection sleeve 11 is used. It is suggested that the injection device 10 including the plunger tip 12 and the like should be cleaned and maintained. Alternatively, there is a high probability that a fatal mechanical loss such as a failure of the injection device 10 will occur, which suggests that maintenance measures such as parts replacement are required at an early stage.
In this way, stable production can be continued by predicting small changes in casting quality and injection equipment by counting the number of alarms, and systematically readjusting the casting conditions and performing simple maintenance of the injection equipment. In addition, it is possible to predict the occurrence of fatal mechanical loss such as failure of the injection device, which ensures preventive management such as advance arrangement of replacement parts.
Here, the reference number of times D2 is preferably set in combination with the reference value A2 depending on the content of the required preventive management. For example, when the highest priority is to stabilize the casting quality, the reference value A2 is strict and the reference number D2 is set small.
If the discrimination result of the discrimination unit 35 is D2> E2, continuous casting is continued, but the cast product is temporarily stored as an inspection required, and the quality is judged again after the discrimination result of the next shot is confirmed. ..

In addition to the above, the configurations listed in the above embodiments can be selected or appropriately changed to other configurations as long as the gist of the present invention is not deviated.

1 Die casting machine 2 Fixed mold 3 Movable mold 4 Mold cavity 10 Injection device 11 Injection sleeve 12 Plunger tip 13 Plunger rod 14 Hydraulic cylinder 15 Pouring port 20 Injection control device 30 Sliding resistance discrimination device 31 Signal input unit 32 Waveform display Section 33 Detection section setting section 34 Calculation section 35 Discrimination section 36 Alarm transmission section 301, 401 Reference value waveform 302, 402 Detection section 303, 403 Actual casting waveform 303a, 403a Difference area between the reference value waveform and the actual casting waveform 303b , 403b Maximum value of waveform during actual casting 303c, 403c Average value of reference value waveform

Claims (6)

The molten metal is supplied to the inside of the injection sleeve at the standby position after the retracting operation of the plunger tip arranged in the injection sleeve, and the molten metal is injected and filled in the mold cavity at the injection completion position after the forward operation of the plunger tip. It is a quality control method for die-cast castings.
A detection section is set within the moving range of the retracting operation of the plunger tip, and the sliding resistance between the plunger tip and the injection sleeve in the detection section is continuously collected, and the sliding during casting of a non-defective product collected in advance. Equipped with a sliding resistance discriminating device that discriminates the quality of sliding resistance for each shot during actual casting compared to resistance.
A quality control method for die-cast cast products, which determines the quality of the actual cast product for each shot based on the evaluation result of the sliding resistance discriminating device.
The quality control method for a die-cast cast product according to claim 1, wherein the detection section is within a range from the injection completion position to the standby position.
The quality control method for a die-cast cast product according to claim 1 or 2, wherein the sliding resistance is a control command value of an electrically controlled hydraulic servo valve system that controls a backward operation or a forward operation of the plunger tip.
The quality control of the die-cast cast product according to any one of claims 1 to 3, further comprising collecting the sliding resistance in the forward operation of the plunger tip within the range from the standby position to the injection completion position. Method.
The sliding resistance discriminating device displays a waveform of the position of the plunger chip and the control command value in the detection section, and superimposes and dissociates the good product waveform at the time of good product casting and the casting waveform at the time of actual casting. The quality control method for a die-cast cast product according to any one of claims 1 to 4, wherein the total area of the waveform is obtained and compared with a preset determination reference area to determine whether the quality of the actual cast product is good or bad for each shot. ..
When the quality of the actual casting is determined to be negative, the sliding resistance determination device sends a caution alarm and starts accumulating the number of caution alarms. The quality prediction method for a die-cast cast product according to any one of claims 1 to 5, wherein the die casting product is stopped and a danger alarm is issued.

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