JP5176100B2 - Detection method of burrs - Google Patents

Description

In the present invention, when a fluid substance such as a molten metal or a molten resin is injection-molded in a mold, or a substance such as a powder that exhibits a behavior similar to that of a fluid under pressure is supplied to the mold. The present invention relates to a method for detecting the occurrence of burrs when molding.

For example, burrs generated during injection molding occur on the mold dividing surface due to mold deformation at the time of molding, except when generated due to gaps formed on the mold dividing surface due to low processing accuracy of the mold. This occurs when a substance enters the gap or because the molding pressure is larger than the clamping pressure and the substance enters the gap generated by the opening of the mold dividing surface during molding. Therefore, in order to detect the occurrence of burrs, as described in Non-Patent Document 1, 1) a method of directly measuring the width of the gap near the tip of the mold dividing surface, 2) molding pressure inside the mold 3) There is a method of measuring the amount of distortion in the lower surface of the mold. Furthermore, 4) there is a method of collecting information (for example, injection pressure, screw position) from a molding machine during molding.

Yasuhiko Murata and two others, “Method for detecting occurrence of burrs in plastic injection molded products”, Mold Technology, July 2006, Vol. 21, No. 8, p. 128-129

However, in the method of directly measuring the width of the gap in 1), since it is necessary to attach a sensor to the mold and to process the signal line from the sensor, 2) measure the molding pressure inside the mold. This method has a problem that the pressure sensor is expensive, and it is necessary to perform processing for mounting the pressure sensor on the mold and taking out the signal line, so that it becomes an unrealistic method for production equipment. In the method 3) of measuring the distortion of the lower surface of the mold, the mold has holes for allowing the cooling medium to pass, mounting holes for various sensors, and ejector pins used for releasing the molded body from the mold. There are a lot of holes and many notches used for mold assembly and mold clamping, and there are many stress concentration parts in the mold. The generated stress concentration interferes with each other and the stress field generated in the mold and on the mold surface becomes very complicated. For this reason, if the strain sensor is not arranged at the optimum position, the measured strain amount is strongly influenced by the hole, and there is a problem that the strain amount associated with the occurrence of burrs cannot be measured. Finding an optimal position is very difficult. Furthermore, the method of collecting information from the molding machine during the molding in 4) is not necessarily linked with the information from the molding machine and the occurrence of burrs, and always detects the occurrence of burrs stably. There is a problem that can not be.

The present invention has been made in view of such circumstances, and an object thereof is to provide a method for detecting the occurrence of burrs that can easily and inexpensively detect the occurrence of burrs without being affected by the structure of the mold. To do.

The method for detecting the occurrence of burrs according to the present invention that meets the above-described object is a method for generating burrs when a movable mold is brought into close contact with a fixed mold and a material is supplied into a molding die held with a predetermined clamping force to perform pressure molding. In the method for detecting the occurrence of burrs,
Time when the said molding die clamping direction of displacement of the lower surface of the pressure molding the movable mold when the material fed into the molding die was measured, exceeds a reference value displacement of the lower surface is preset It is determined that burr has occurred.

Then, the displacement of the lower side can be determined by measuring the change in position with respect to the reference position of the lower surface of the movable mold.

In the detection method of burr generation according to claims 1 and 2, the displacement distribution generated in the molding die at the time of molding is not affected by the stress concentration portion existing in the molding die. It becomes easy to associate the displacement amount with the occurrence of burrs. As a result, it becomes possible to detect the occurrence of burrs due to variations in molding conditions during continuous molding.
In addition, since the displacement distribution of the molding die is not affected by the stress concentration part, the burr generation that can be judged from the numerical analysis results (displacement amount obtained by numerical analysis) and the burr generation in the actual molding die should be compared. Thus, the accuracy of numerical analysis results can be improved, and the amount of displacement can also be used as one of the indices when examining the reproducibility of the molding state. Furthermore, the numerical analysis model can be simplified, and an efficient and high-quality molding die can be designed in a short time.

In particular , since the mold is easily displaced in the mold clamping direction, measuring the displacement in the mold clamping direction of the lower surface of the movable mold makes it easy to cope with the occurrence of burrs.
Further, since the movable mold is easily displaced as compared with the fixed mold, the displacement can be easily and accurately measured by measuring the displacement of the lower surface of the movable mold.
In the method for detecting the occurrence of burrs according to claim 2, since the amount of change in position relative to the lower surface of the movable mold is measured, it is easy to install the measuring device, and the measurement can be performed accurately and easily.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is a schematic diagram showing the structure of a molding die to which the method for detecting burr occurrence according to one embodiment of the present invention is applied, and FIG. 2A is a movable obtained by numerical analysis in consideration of stress concentration. Explanatory diagram showing the displacement distribution in the mold clamping direction on the outer surface of the mold, (B) is an explanatory diagram showing the displacement distribution in the mold clamping direction on the outer surface of the movable mold obtained by numerical analysis without considering the stress concentration, FIG. 3 (A) is a graph showing the change behavior of the displacement in the clamping direction on the outer surface of the movable mold measured at the time of pressure molding, and (B) is the gap between the boundary surface of the fixed mold and the movable mold measured at the time of pressure molding. FIG. 4 is a graph showing the change behavior, and FIG. 4 is an explanatory diagram showing the relationship between the displacement of the movable outer surface, the holding pressure, and the occurrence of burrs.

As shown in FIG. 1, an injection mold 10, which is an example of a molding mold to which the method for detecting occurrence of burrs according to an embodiment of the present invention is applied, is fixed to a frame (not shown) of a molding machine. It has a fixed die 12 fixed via an attachment plate 11 and a movable die 16 attached via a plurality of spacer blocks 15 to a movable side attachment plate 13 provided on the frame of the molding machine. As a result, the movable mold 16 moves (lifts) with respect to the fixed mold 12 by the movement of the movable mounting plate 13. A space 14 is formed by a plurality of spacer blocks 15 between the movable die 16 and the movable side mounting plate 13.
Then, the injection mold 10 is formed by raising the movable mold 16 to be in close contact with the fixed mold 12 and holding it with a predetermined clamping force. A recessed portion 17 that opens downward is formed in the lower portion of the fixed mold 12, and communicates with the cavity 18 in a cavity 18 having a predetermined shape surrounded by the recessed portion 17 of the fixed mold 12 and the upper surface of the movable mold 16. By injecting the material at a predetermined pressure through the material supply path 18a and holding the pressure, the material can be formed into a predetermined shape.

Next, a burr generation detection method according to an embodiment of the present invention will be described.
As shown in FIG. 1, when the material supplied into the injection mold 10 is pressure-molded, the material in the cavity 18 causes the inner surface of the concave portion 17 of the fixed mold 12 and a part of the upper surface of the movable die 16 (recessed portion). A molding pressure (an injection pressure and a holding pressure that is subsequently applied) is applied to a region that covers 17 openings. For this reason, deformation occurs in the fixed mold 12 and the movable mold 16, and displacement occurs on the outer surface of the injection mold 10, that is, on the outer surfaces of the fixed mold 12 and the movable mold 16. On the other hand, due to the structure of the injection mold 10, the molding pressure acting on the cavity 18 is particularly acting in the mold clamping direction, and the injection mold 10 is easily displaced in the mold clamping direction. Further, when the fixed mold 12 and the movable mold 16 are compared, a part of the outer surface (lower side) of the bottom wall of the movable mold 16 is in contact with the space portion 14 and thus has a weak structure and is displaced. easy. Therefore, in order to grasp the behavior of the injection mold 10 during pressure molding, the displacement amount of the bottom wall outer surface of the movable mold 16 is effective.

2A and 2B show the results of numerical analysis performed to grasp the displacement behavior in the mold clamping direction on the lower surface of the movable mold 16. FIG. 2A shows a hole provided in the movable mold 16 for allowing a cooling medium to pass therethrough, a mounting hole for various sensors, a hole for an ejector pin used for releasing the molded body from the mold, and movable. The displacement distribution on the lower surface of the movable mold 16 when considering the stress concentration due to a plurality of holes and a large number of notches used when assembling and clamping the mold 16, (B) shows the case where the stress concentration is not considered. The displacement distribution on the lower surface of the movable mold 16 is shown. Comparing the displacement distribution states of (A) and (B), it can be seen that the influence of stress concentration does not appear in the displacement distribution. 2A and 2B, only the displacement distribution in the half region of the lower surface of the movable die 16 is shown because of the symmetry of the displacement distribution on the lower surface of the movable die 16.

Here, the displacement of the lower surface of the movable mold 16 is obtained, for example, by measuring the position change amount of the lower surface of the movable mold 16 with respect to the upper surface of the movable side mounting plate 13 which is an example of the reference position. Therefore, as shown in FIG. 1, an eddy current displacement sensor 19, which is an example of a displacement sensor, is mounted on a movable side mounting plate 13 via a fixed member 20 so as to be disposed in the space portion 14. The amount of change in the position of the lower surface of the mold 16 is measured.
On the other hand, since the displacement distribution on the lower surface of the movable die 16 is not affected by the stress concentration, the injection mold 10 at the time of pressure molding is obtained by obtaining the displacement at an arbitrary position in the lower surface of the movable die 16. Can be understood.

Accordingly, the result of measuring the displacement d ₁ in the mold clamping direction, for example, at the center of the lower surface of the movable mold 16 when an appropriate injection condition is set and pressure molding is performed with a constant molding pressure (also referred to as holding pressure). Is shown in FIG. Further, FIG. 3B shows a result of measuring a change in the gap d ₂ generated at the boundary portion (divided surface) between the fixed die 12 and the movable die 16 at the time of pressure molding with a gap sensor. Here, the displacement d ₁ and the gap d ₂ in the mold clamping direction are both based on the mold clamping (d ₁ = 0, d ₂ = 0). Incidentally, the gap d ₂ does not return to zero at the end pressure, due to the inability lost gap d ₂ also becomes 0 coercive pressure burrs generated in the gap d _2.

From FIGS. 3A and 3B, there is a good correspondence between the change behavior of the displacement d _{1 on} the lower surface of the movable die 16 and the change behavior of the gap d _{2 at} the boundary, and the absolute value of the displacement d ₁ It can be confirmed that the time when the value shows the maximum value coincides with the time when the gap d ₂ becomes the maximum. Here, it is clear from the burr generation mechanism that there is a clear correspondence between the change behavior of the gap d ₂ generated at the boundary between the fixed mold 12 and the movable mold 16 and the presence or absence of burr generation. Therefore, it is understood that there is a clear correspondence between the change behavior of the displacement d ₁ of the lower surface of the movable die 16 having a good correspondence with the gap d _{2 at the} boundary and the presence or absence of the occurrence of burrs.

Therefore, the fixed mold 12 and the movable mold 16 are loaded with a fixed clamping force to form the injection mold 10, and molding is performed while changing the holding pressure, and the occurrence of burrs is examined, and at the time of pressure molding The displacement d ₁ in the mold clamping direction on the lower surface of the movable mold 16 was measured. FIG. 4 shows the relationship between the maximum absolute value of the displacement d _{1 on} the lower surface of the movable die 16, the holding pressure, and the occurrence of burrs. FIG. 4 also shows the relationship between the maximum value of the gap d ₂ generated on the split surface between the fixed mold 12 and the movable mold 16, the holding pressure, and the occurrence of burrs.

From FIG. 4, when the holding pressure is low and a molded body having a predetermined shape cannot be obtained (in the case of a short shot), no burr is generated, and the maximum absolute value of the displacement d _{1 on} the lower surface of the movable die 16 and the boundary It can be seen that the maximum value of the gap d ₂ between the portions is small. On the other hand, when the holding pressure is increased, a molded body having a predetermined shape is obtained, but burrs are also generated at the same time, and the maximum absolute value of the displacement d _{1 on} the lower surface of the movable die 16 and the gap d _{2 at} the boundary portion It can be seen that the maximum value increases. Further, it can be seen that there is an appropriate molding region in which a molded body having a predetermined shape is obtained between the holding pressure for short shot and the holding pressure for generating burrs. In the case of FIG. 4, the range of the maximum value of the absolute value of the displacement d ₁ of the lower surface of the movable mold 16 in the proper molding region is less than 0.0025 mm. Therefore, for example, if 0.002 mm is set in advance as a reference value, the maximum value of the absolute value of the displacement d _{1 in} the mold clamping direction of the lower surface of the movable mold 16 is measured, and the obtained displacement value is It becomes possible to determine that burrs have occurred when the preset reference value is exceeded.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above-described embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included.
For example, although the displacement in the mold clamping direction on the outer side surface (that is, the lower side surface ) of the movable mold is measured with an eddy current type displacement sensor, a laser displacement meter or a differential transformer type displacement sensor can also be used.
Furthermore, in this embodiment, a displacement sensor (eddy current type displacement sensor) is attached to the reference position (movable side mounting plate) side, and the amount of change in position of the outer side surface (lower side surface of the movable die) of the molding die is measured. However, a displacement sensor may be attached to the outer surface of the molding die to measure the position change amount of the outer surface of the molding die with respect to the reference position.

It is a schematic diagram which shows the structure of the shaping die which applies the detection method of the burr | flash generation which concerns on one embodiment of this invention. (A) is explanatory drawing which shows the displacement distribution of the mold clamping direction in the outer side surface of the movable mold | die calculated | required by the numerical analysis which considered stress concentration, (B) is the movable type | mold calculated | required by the numerical analysis without considering stress concentration. It is explanatory drawing which shows the displacement distribution of the mold clamping direction in an outer surface. (A) is a graph showing the change behavior of displacement in the mold clamping direction on the outer surface of the movable mold measured during pressure molding, and (B) is the change in the gap between the boundary surface of the fixed mold and movable mold measured during pressure molding. It is a graph which shows a behavior. It is explanatory drawing which shows the relationship of the displacement of a movable type outer side surface, holding pressure, and burr | flash generation | occurrence | production.

10: injection mold, 11: fixed side mounting plate, 12: fixed type, 13: movable side mounting plate, 14: space part, 15: spacer block, 16: movable type, 17: recessed part, 18: cavity, 18a : Material supply path, 19: Eddy current displacement sensor, 20: Fixed member

Claims (2)

In the detection method of burr generation, which detects a burr generated when a material is supplied into a molding die held in contact with a fixed mold and held with a predetermined clamping force, and pressure molding is performed.
Time when the said molding die clamping direction of displacement of the lower surface of the pressure molding the movable mold when the material fed into the molding die was measured, exceeds a reference value displacement of the lower surface is preset A method for detecting the occurrence of burrs, characterized by determining that burrs have occurred in In the detection method of claim 1, wherein the burr, the displacement of the lower side, the detection method of the burr, characterized in that determined by measuring the change in position with respect to the reference position of the lower surface of the movable mold.

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