JPH105971A - Injection molding method in die casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely obtain molded products having the same quality even in the case of multi-cavity molding and to prevent formation of defective molded products by injecting after confirmation of almost the same gas as the gap at the time of casting of a molded product in the good mold clamping condition. SOLUTION: After completing the clamping process of the dies 2, 4, the gap Δa between the joining surfaces of the dies 2, 4 corresponding to plural pieces of die cavity parts 3, is measured. When the gap Δa deviates from a preset allowable range, the die clamping force of a clamping cylinder 10 for the dies is corrected and the dies are reclamped. Then, after confirming that the gap Δa is in the preset allowable range, the injection process of molten metal into a cavity 3 in the dies in executed. By this method, the unevenness in filling behavior of the molten metal into each cavity in the dies at each shot, is eliminated and the quality of the formed product in each shot is stabilized without any variation, and the qualities of plural pieces of formed products in the same shot are uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection flow press (hereinafter referred to as "injection") of a material having a relatively low melting point such as aluminum and aluminum alloy, or magnesium and magnesium alloy in a molten state, semi-solid state or solidified state. The present invention relates to an injection molding method of a molding device such as a die casting machine or a squeeze cast machine for obtaining a product having a desired shape, and in particular, forming a plurality of mold cavities of the same shape in one mold. In this case, a plurality of molded products having the same shape are molded simultaneously with the same shot, that is, the quality of each molded product based on the difference in the mold clamping situation when performing so-called “multiple take” (two take, three take, etc.). The present invention relates to an injection molding method for a die casting machine capable of obtaining a plurality of good, dense, and high-quality molded products every shot by eliminating variations.

[0002]

2. Description of the Related Art A die casting machine is, for example, a method in which an aluminum alloy or a magnesium alloy is heated in a melting furnace to a molten state (hereinafter referred to as a molten metal), poured into an injection cylinder 6 shown in FIG. This apparatus is capable of mass-producing aluminum alloy products and magnesium alloy products by repeatedly injecting the molten metal into the mold cavity 3 having a shape, cooling and solidifying the mold, mechanically opening the mold from the dividing surface, and taking out the product. When the direction of the injection piston 6A and the direction of the injection cylinder 6 (5 is called a sleeve) are horizontal, the horizontal direction is used, and when the direction is vertical, the vertical direction is called vertical casting.
In addition, the mold is split horizontally and the split surface of the mold is opened
The type in which the split surface of the mold opens horizontally and vertically is called vertical mold clamping. These combinations are referred to as a horizontal clamping horizontal casting type or the like, but the most common types are a horizontal clamping horizontal casting type (hereinafter referred to as a horizontal type) and a vertical clamping vertical casting type (hereinafter referred to as a vertical type).

In the case of the horizontal type, as shown in FIG. 11, there is a gas reservoir in the upper half of the sleeve 5 due to its structure, and when the injection piston 6A moves at a high speed, the gas in the upper part of the sleeve 5 is drawn into the molded product. The sealing results in a reduction in the mechanical strength of the product. Further, when heated, blisters (local swelling) are generated, so that heat treatment cannot be performed.
Furthermore, when the gas in the mold cannot escape in time, entrainment of the gas is inevitable. Then, when the molten metal is jetted at a high speed along the path (runner 7a and gate 7) from the sleeve 5 to the mold cavity 3, the gas in the mold is easily entrained. Therefore, the speed of the injection piston 6A is normally low when the tip of the molten metal passes through the sleeve 5 and the gate 7, and then increased in accordance with the shape of the mold. In addition, since injection must be completed before solidification, low-speed injection is also limited.

On the other hand, in the case of the vertical type, as shown in FIG. 12, gas during hot water supply easily escapes upward, so that entrainment of the gas in the sleeve 5 can be avoided. As a result, a high quality casting without gas entrainment in the gate 7 and the mold can be obtained. Therefore, the horizontal type is used to produce high-quality products by injecting at high speed, and the vertical type is used to produce high-quality products by injecting at low speed and sufficiently releasing gas. ing.

In general, the former method is called a die casting method (DC
Method), and the latter is called the squeeze cast method (SC method). In the die casting method and the squeeze casting method, the material is in a molten state, whereas in the thixocasting method, the material is in a semi-solid block shape. in recent years,
Some horizontal-type squeeze machines also perform low-speed injection. The biggest technical problem of these low-speed injection methods is how to determine the injection speed in order to prevent gas entrainment in the sleeve, gate and mold.

[0006] From the above, conventionally, in the die-casting method of horizontal clamping horizontal casting, in the initial stage of normal injection filling, low-speed injection with a gate speed of 0.5 to 2 m / s is performed.
After the tip surface of the molten metal passes through the gate, high-speed injection with a gate speed of 30 to 60 m / s is performed. On the other hand, in the squeeze method, the module in the sleeve (specific surface area per unit volume of the molten metal) is small, the temperature drop of the molten metal during injection filling is smaller than that of the die casting method, and the injection speed is low because the safety against solidification of the molten metal is high. Therefore, low-speed injection with a gate speed of 0.5 to 2 m / s is performed from the start of injection filling to the completion of injection filling,
That is why we have obtained high quality molded products.

[0007] Further, in the case of mass-producing a small product in such a die casting method or a squeeze method, a plurality of mold cavities having the same shape are formed in one mold, as shown in FIG. And one runner (runner)
In other words, a so-called "multiple molding" is also carried out in which the molten metal is guided to the above-mentioned plurality of mold cavities by branching from the gate and the gate to simultaneously form a plurality of molded products having the same shape in one shot.

[0008]

Incidentally, the mold clamping state of the mold is not always constant for each shot, and the gap between the fixed mold and the movable mold is such that the same mold clamping force is obtained for each shot. Every time the mold clamping cylinder is activated, it changes slightly. And, for example, even in a simple mold that simply moves the movable mold relative to the fixed mold, the gap differs every shot, and furthermore, a plurality of cores divided into several parts in the middle between the fixed mold and the movable mold. In a complex mold that moves forward and backward, there is a tendency that the difference in the gap between the mold mating surfaces every time is larger than a simple mold.

[0009] In particular, in the case of "multi-cavity", a plurality of mold cavities formed in the mold have the same shape,
Moreover, even if they are formed completely symmetrically, the mold clamping state is slightly different every time, and the quality (molded product weight, internal structure of the molded product, etc.) of the molded product formed by the same shot is different, which causes a problem in quality control. Had left.

On the other hand, in recent years, the demand for the quality of metal molded products has been increasing year by year. In order to obtain high quality and high precision molded products, the injection control system of the die casting machine has been becoming more sophisticated and higher in performance year by year. Although the precision has been improved, the moldings of all shots are still unable to reach the passing line at a high level that satisfies the requirements of high quality and high precision, and they are operating while generating considerable molding defects Is the current situation. Therefore, in order to prevent the occurrence of defective moldings and to improve the yield, the factors of variation in molding conditions (melt temperature, injection speed, injection pressure, etc.) during molding are measured, and the same molding is performed for each shot. In order to obtain a product having a high quality, we focus on the development of a device that enables the operation that can be performed every time, while grasping the preferable injection conditions.

However, as described above, with regard to the mold clamping state before the injection step, more specifically, the gap between the dies is not as important as the molding conditions described above. As shown in Japanese Patent Publication No. 1-12651, Japanese Patent Publication No. 1-12652, and Japanese Patent Publication No. 1-12633, in the case of a gap which seems to be abnormal,
Although an operation method for correcting the injection pressure in the injection step to cover the injection pressure has been proposed, there has been a problem that it is not possible to completely eliminate defective molded products which are considered to be caused by a gap abnormality. In the present invention, the cause of the abnormalities of the gap causes a molded article failure and the countermeasures against it is presented, and particularly in the case of "multiple molding",
It is intended to present measures for reliably obtaining molded articles of the same quality.

[0012]

In order to solve the above-mentioned problems, according to the present invention, in the first invention, a metal material having fluidity by heating or pressurizing means is made of a substantially hermetically sealed metal material. In the injection molding method of a die-casting machine, which is repeatedly press-fitted into a mold cavity, a plurality of same molded articles are formed by the same shot by holding a mold cavity for molding a plurality of molded articles of the same shape. In a method of injection molding a die casting machine, after the mold clamping step is completed, the gap between the joining surfaces of the molds corresponding to the plurality of mold cavities is measured. When the gap deviates from the preset allowable range, after correcting the mold clamping force of the mold clamping device of the mold and re-clamping, after confirming that each gap falls within the set allowable range. , The metal material And to implement the step of injecting into the mold cavity. Further, in the second invention, the allowable range of each gap in the mold joining surface is set in consideration of the gap at the end of mold clamping in injection molding of a good molded product obtained under the same injection conditions in advance. I made it.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, after the mold clamping step is completed for each shot, the gap between the joining surfaces of the respective dies corresponding to the plurality of dies cavity portions formed in the same dies. When the measured gap is within a preset allowable range, the injection process is directly performed to produce a desired molded product, and each measured gap value deviates from this allowable range. When the mold is closed, the mold clamping operation (mold opening and mold closing) is repeated, and when all the gap values are within the gap setting range, the molding is performed in the next injection step. This allowable range is set based on past performance values and experience values. Further, in the second invention, the allowable range of each gap is the same as the injection condition, the gap between the mold joining surfaces in a shot when a good molded product is obtained with the same molten metal (this is referred to as a reference shot). Set as a reference.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 9 relate to an embodiment of the present invention,
1 is a control system diagram of the die casting machine, FIG. 2 is a work process diagram of the die casting machine, FIG. 3 is a schematic configuration diagram of a visualization / flow test device based on a visualization model, and FIG. 4 is an explanatory diagram showing a visualization flow test result using a visualization model. , FIG. 5 is a longitudinal sectional view of an automobile wheel mold, FIG. 6 is a plan sectional view of an automobile wheel mold, FIG. 7 is an explanatory view showing a visualization flow test result by a visualization model, and FIG. FIG. 9 is a perspective view of a molded product (a set of two pieces) in the case of a plurality of pieces (two pieces).

As shown in FIG. 1, in the present invention, displacement sensors are provided at various points on a joining surface of a mold. In the example of FIG. 1, a simple horizontal mold clamping case is shown. Displacement sensors 52 and 62 and a target 54 are respectively provided above and below a joint surface (partition line: also called a parting line) between the fixed mold 2 and the movable mold 4. , 64 are provided, and a measurement signal of the gap Δa of the mold joining surface measured at the end of the mold clamping is input to the control device 20 via the amplifier 50. On the other hand, pressure signals on the head side and the rod side of the injection cylinder 6 are input to the control device 20 via the pressure detector 6B and the amplifier 30, and the output of the injection cylinder 6 is detected by the load sensor 6E. The radiation output signal is also input to the control device 20 via the amplifier 30. Further, a position signal of a position sensor 6D that detects the position of the piston rod 6a or the piston 6A of the injection cylinder 6 is input to the control device 20 via the display recording device 40. The control device 20 analyzes, compares, calculates, and determines the numerical information obtained as these various input signals and transmits an operation command intended by the operator to power means such as the injection cylinder 6 and the mold clamping cylinder 10. I do. In the present invention, in a die casting machine having a control system line configured as described above, in order to enhance the reliability of the quality of a molded product, a gap value measured at each part of a mold division surface is taken as one of injection conditions. In addition to other injection conditions such as melt temperature, injection pressure, injection speed, etc., it is decided to reflect on the operation.

In order to continuously mold high-quality molded products and to minimize the occurrence of defective molded products, it is important to investigate the cause of the occurrence of defective molded products. Similarly to the above, it was found that whether or not the gap between the mold joining surfaces at the time of completion of the mold clamping was appropriate had a great influence on the quality of the molded product. The details will be described below.

For example, as shown in FIG. 8, the applicant of the present invention has a mold having a “two-cavity” mold cavity for obtaining a pair of right and left molded articles of the same shape arranged symmetrically between the two molds. Molding in a mold, so-called "multi-take" molding,
In view of the fact that the molded article weight and quality of the left and right molded articles differ greatly in each shot, and that the tendency is reproducible, which has been a serious problem in quality control, various factors have been investigated to investigate these causes. I tried to consider. 9 is the same as FIG.
FIG. 6 is a perspective view of a molded product (before separation) in the case of two pieces in the mold of FIG. As a result, for example, the 2
During molding, the gates 7 and 7 and the molds leading to both mold cavities 3 and 3 are formed due to the fact that the gaps between the two molds in the degassing passages 8 and 8 corresponding to the individual mold cavities are not the same. It was determined that the product quality (molded product weight, molded product structure, etc.) of the two molded products was different due to the difference in the molten metal entry speeds into the cavities 3 and 3. In order to prove this, that is, to find out why the gap value of the mold joining surface has a large effect on the quality of the molded product, the flow behavior of the molten metal into the mold cavity in different mold-clamping conditions is On the other hand, an experiment to confirm this was planned and carried out under the hypothesis that it was a major factor impeding the production of uniform molded article quality. To grasp the actual flow phenomena, the model was simplified and a flow test was performed using a visualized plastic model. FIG. 3 shows a schematic configuration of a visualization / flow test apparatus, which is a transparent plastic model made of an acrylic resin (dimensions: width 100 mm × height 2).
(00 mm × 10 mm thick), water that is considered to have the same fluid properties as the molten metal at about 700 ° C. was flowed, the flow state was photographed with a high-speed camera, displayed on a CRT display screen, and printed out. Things.

FIG. 4 is a photograph in which water is flowed as a fluid through the above-mentioned flat plastic model, and the flow condition is photographed momentarily. The model is fastened with two front and rear plastic plate flanges with 13 bolts and nuts. In order to see the effect of the mold clearance (gap), FIG. 4 (a) when the bolt and nut are loosely tightened and FIG. The situation is slightly different. (In the case of FIG. 4A in which the bolts are loosely fastened, it is considered that there is more space by several μm than in the case of FIG. 4B in which the bolts are firmly fastened.) . In order to quantify the strength of bolt and nut fastening, the bottom 40m
The time required for the water filled to a height of m to descend to a height of 20 mm by natural flow was measured. As a result, the time was 35 seconds in FIG. 4A and 60 seconds in FIG. 4B. FIG. 4 (a)
It can be seen that the connection is looser than that in FIG. From the above results, it was found that the pressure inside the mold cavity changed due to slight differences in the gap between the mold joining surfaces, and the flow behavior changed slightly, which indicates that the quality of the molded product differs for each shot. It was clarified that one of the possible reasons is the difference in mold gap. Further, the results of subsequent experiments revealed that the larger the difference between the gaps, the more the flow behavior of the fluid flowing in the cavity changed. Furthermore, in comparison with a simple mold having only one pair of left and right or upper and lower pairs of molds, a complex mold in which a plurality of cores (cores) are interposed between the pair of left and right or upper and lower molds has a simpler structure. The difference in the gap between shots is greater each time than in a conventional mold, and the difference in the flow behavior is greater each time, resulting in a greater variation in the quality of the molded product.

FIGS. 5 and 6 show a vehicle wheel mold 70, in which a four-divided core 70C is provided between an upper mold 70A and a lower mold 70B to move back and forth from the outside toward the center.
In such a mold 70, not only one mold joining surface but also a plurality of mold joining surfaces are present, and a complicated joining state is formed. Therefore, a large gap occurs in the mold joining surface for each shot, and the molding The non-uniformity of the product quality between shots becomes large.

An experiment conducted to verify the above is shown in FIG. 7, in which a two-dimensional plastic model having a wheel shape is used, and water is supplied from below to above as a fluid with left and right gaps being different. I photographed the situation. 7A shows the case where the gate speed is 0.50 m / s, and FIG. 7B shows the case where the gate speed is 1.00.
It shows the case of m / s, and in any case, the situation where the symmetry of the flow was lost due to the difference between the left and right gaps was observed.

As a result of considering the flow test results using the plastic visualization model described above, the flow behavior of the molten metal in the mold cavity greatly changes due to a slight difference in the gap between the mold joining surfaces, which is a factor in the quality of the molded product for each shot. As a countermeasure, it was found that the mold was in the same state as when a good molded product was cast, that is, the gap was almost the same. Is considered to be the simplest and most reliable method. In particular, it has been confirmed that this is an extremely effective method for uniforming the quality of a plurality of molded products of the same shot in "multiple-shot". Therefore, in the present invention, in consideration of these points, the operation in the actual operation is performed according to the operation procedure of FIG. The setting of the allowable range of each of these gaps is set based on past actual values and experience values. It is further desirable that a shot in which a good molded product in the same lot is obtained is used as a reference shot, and an allowable range is set in consideration of the gap between the mold joining surfaces in the reference shot. According to various experimental results inside the applicant and operational experience with actual machines, the allowable range that is usually desirable as the gap between the mold joining surfaces is 0.10 mm to 0.12 mm.
Although the optimum range varies little by little depending on the type of the molten metal, the temperature of the molten metal, the size and shape of the mold, the injection speed, the injection pressure, and other injection conditions, it is important to understand the good tolerance of the same lot. Is desirable.

[0022]

As described above, according to the method of the present invention, a die-casting method for repeatedly producing a metal material having fluidity by means of heating or pressurizing by flow-pressing it into a substantially closed mold cavity. In a machine injection molding method, a die casting machine method for molding a plurality of same molded products by the same shot by holding a mold cavity for molding a plurality of molded products of the same shape in the mold. After the mold clamping process is completed, the gap between the joining surfaces of the molds corresponding to the plurality of mold cavities is measured, and when each gap deviates from a preset allowable range. After correcting the mold clamping force of the mold clamping device of the mold and re-clamping and confirming that each gap falls within the set allowable range, the metal material is introduced into the mold cavity. Execute the injection process Therefore, there is no variation in the filling behavior of the molten metal in each mold cavity for each shot, and the quality of the molded product is stable without changing for each shot, and the uniformity of the quality of a plurality of molded products of the same shot is achieved. In addition, the occurrence of defective molded products is prevented, the product yield is improved, and the productivity is improved. In addition, by monitoring the mold joining surface gap, when the gap is abnormally large, the presence and position of the molten metal inclusions interposed between the mold joining surfaces can be quickly detected. It can be removed and maintenance is improved.

[Brief description of the drawings]

FIG. 1 is a control system diagram of a die casting machine according to an embodiment of the present invention.

FIG. 2 is a work process diagram of the die casting machine according to the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a visualization / flow test apparatus using a visualization model according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a visualization flow test result using a visualization model according to an example of the present invention.

FIG. 5 is a longitudinal sectional view of a vehicle wheel mold according to the present invention.

FIG. 6 is a plan sectional view of a vehicle wheel mold according to the present invention.

FIG. 7 is an explanatory diagram showing a visualization flow test result by a visualization model according to an example of the present invention.

FIG. 8 is a front view of a fixed mold in a case of a multi-cavity (two-cavity) according to the embodiment of the present invention.

FIG. 9 is a perspective view of a molded product (a set of two pieces) in the case of a plurality of pieces (two pieces) according to the embodiment of the present invention.

FIG. 10 is an overall configuration diagram of a conventional molding apparatus.

FIG. 11 is a schematic longitudinal sectional view for explaining the injection filling state in a conventional molding apparatus.

FIG. 12 is a schematic longitudinal sectional view for explaining the injection filling state of a conventional horizontal clamping vertical casting type molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding apparatus 2 Fixed mold 3 Cavity 4 Movable mold 5 Sleeve 6 Injection cylinder 6A Piston 6B Pressure detector 6C Limit switch 6D Position sensor 6E Load sensor 7 Gate 7a Runner 8 Degassing path 10 Mold cylinder 20 Control device 30 Amplifier Reference Signs List 40 display recording device 50 amplifier 52 displacement sensor 54 target 60 amplifier 62 displacement sensor 64 target 70 automobile wheel mold 70A upper mold 70B lower mold 70C core 72 cavity 100 visualization / flow test apparatus 200 molded article △ a gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kosei Murakami 1980, Kogushi-jiki-oki, Ube City, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Machinery and Engineering Business Unit

Claims (2)

[Claims] 1. An injection molding method for a die casting machine in which a metal material having fluidity by heating or pressurizing means is flow-pressed into a substantially closed mold cavity and repeatedly produced. An injection molding method of a die casting machine for holding a mold cavity for molding a plurality of molded products and molding a plurality of the same molded products in the same shot, wherein the plurality of molded products are formed after a mold clamping process is completed. The gap between the joining surfaces of the molds corresponding to the individual mold cavities is measured, and when each gap deviates from a predetermined allowable range, the mold clamping force of the mold clamping device of the mold is corrected. After re-clamping and confirming that the respective gaps fall within the set allowable range, and then performing an injection step of the metal material into the mold cavity. 2. The allowable range of each gap on the mold joining surface is set in consideration of the gap at the end of mold clamping in injection molding of a good molded product obtained under the same injection conditions in advance. Molding method of die casting machine.