JP2008126308A - Pressure molding method and pressure molding apparatus - Google Patents

Abstract

The present invention proposes a technique capable of maintaining product dimensions with high accuracy even when there is a change in the temperature of the mold.
A temperature of a mold for performing pressure molding (mold temperature T) is detected by a temperature sensor 20, and pressurization of a cavity 5 formed by the mold is performed based on the temperature of the mold. A dimension L in the direction is to be set, and the dimension L is set by defining a stop position S at the time of pressurization of the mold (upper punch 3) moving in the pressurizing direction. I will do it.
[Selection] Figure 1

Description

  The present invention relates to a technique for improving product dimensional accuracy in pressure molding.

  2. Description of the Related Art Conventionally, in pressure molding such as powder molding, there is known a technique for providing a stopper for determining a stop position of a mold and ensuring accuracy of product dimensions (for example, refer to Patent Document 1). In this Patent Document 1, a punch that is movable with respect to a die is divided into a plurality of parts, and each part is mechanically stopped by a stopper plate, that is, a mechanism of a mechanical stopper is formed. It is said.

  By the way, especially in powder molding for producing sintered metal machine parts and the like, if molding is continued, the temperature of the die composed of dies and punches rises due to frictional heat generation, and the size of the die increases (heat expansion). For this reason, for example, the thickness of the product molded by pressing with the upper and lower molds decreases as the mold temperature increases. Conversely, when the temperature of the mold is lowered, that is, when the environmental temperature is low, the dimension of the mold is considered to decrease. In this case, the thickness of the product is equal to the temperature of the mold. It will increase with the decline.

If molding is continued without considering such a temperature change of the mold, as a result, the dimensional accuracy of the product varies, and a defective product that cannot obtain the specified dimensional accuracy is produced. It will be.
JP 2004-130348 A

  Therefore, the present invention focuses on the temperature change of the mold, and proposes a technique that makes it possible to maintain the product dimensions with high accuracy even when this temperature change occurs.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, as described in claim 1, the temperature of the mold for performing pressure molding is detected by a temperature sensor, and based on the temperature of the mold, the pressure in the pressurizing direction of the cavity formed by the mold is determined. The dimensions are to be set.

  In addition, as described in claim 2, the detection of the mold temperature by the temperature sensor is performed at least for each molding cycle by the mold.

  Further, as described in claim 3, the dimension of the cavity in the pressurizing direction is set by defining a stop position at the time of pressurizing the mold moving in the pressurizing direction. is there.

  According to a fourth aspect of the present invention, there is provided a temperature sensor for detecting the temperature of a mold for performing pressure molding, and a mold that moves in the pressurizing direction based on a detection value of the temperature sensor. The pressure molding apparatus includes a controller having a program for calculating a stop position, and a pressure device for stopping the mold at a stop position obtained by the controller.

  Further, as described in claim 5, the mold temperature is detected by the temperature sensor at least every molding cycle of the mold.

  According to the first and fourth aspects of the invention, the predetermined stop position of the mold is automatically corrected according to the change in the mold temperature, and the product thickness of the molded product is always within the range of the predetermined threshold value. be able to.

  Further, according to the inventions of claims 2 and 5, the mold temperature can be monitored in real time, and the mold stop position at the time of pressure molding is corrected according to the mold temperature immediately before molding. Can do. Therefore, the product dimensions can be maintained with high accuracy.

  According to the third and fourth aspects, since the stop position of the mold that is assumed to have already moved is corrected, the correction of the stop position is performed by software change without changing the apparatus configuration. It becomes possible.

Next, embodiments of the invention will be described.
As shown in FIG. 1, in the pressure molding apparatus 100 of the present embodiment, a die 4 is formed from a lower punch 2 that is inserted into the die 1 from the lower side, and an upper punch 3 that is also inserted into the die 1 from the upper side. Is configured. A cavity 5 surrounded by the die 1, the lower punch 2, and the upper punch 3 is filled with a powder material 10 and pressed so as to insert the upper punch 3 into the cavity 5. By doing so, the molded product 6 is manufactured. The dimension L in the pressurizing direction of the cavity 5 is determined by the product thickness M of the molded product 6.

  Further, as shown in FIG. 1, the upper punch 3 is fixed to the lower surface of a pressure plate 7 that moves in the vertical direction in the figure, and moves up and down integrally with the pressure plate 7. During the above-described molding, the pressure plate 7 moves downward so that the pressure molding by the upper punch 3 is performed.

  As shown in FIG. 1, the upper surface of the pressure plate 7 is connected to the lower end of the hydraulic rod 8, and moves up and down by the expansion and contraction of the hydraulic rod 8 driven by a hydraulic servo mechanism (not shown). It is said.

  As shown in FIG. 1, the lower punch 2 is installed on a base plate 9, and the pressure plate 7 is configured to move up and down with the base plate 9 side as a fixed side. The left side of FIG. 1 shows the state before the molding, in which the powder material 10 is filled into the cavity 5 with the upper punch 3 raised (upward position), and the upper punch is shown on the right side. 3 shows a state in which the molded product 6 is manufactured by lowering 3 and pressing the powder material 10. Note that the structure of the die such as the upper and lower punches is not limited to the example shown in FIG. 1. For example, the upper and lower punches may be divided into separate dies and formed in multiple stages.

  As shown in FIG. 1, a temperature sensor 20 is provided for measuring the temperature of the upper punch 3 when the upper punch 3 is in the raised position. In the present embodiment, the temperature sensor 20 is configured by a non-contact infrared sensor, and measures the temperature of the outer peripheral surface 3a of the upper punch 3.

  In addition to using such a non-contact type temperature sensor, it may be possible to provide a thermocouple inside the upper punch 3 or to use a contact type temperature sensor. It is desirable to apply an optimum temperature sensor as appropriate. Further, instead of measuring the temperature of the upper punch 3, the temperature of the lower punch 2 or the temperature of the die 1 may be measured, and the temperature of a portion that is located in the vicinity of the cavity 5 is measured. As a result, the effects of the present embodiment can be obtained.

  As shown in FIG. 2, the temperature of the upper punch 3 detected by the temperature sensor 20, that is, the mold temperature T is input to the controller 30. The controller 30 controls a hydraulic servo mechanism 40 that drives the upper punch 3 (pressure plate 7). Then, the controller 30 obtains a stop position S when the upper punch 3 is lowered (when pressurization is completed) based on the mold temperature T, and outputs information on the stop position S to the hydraulic servo mechanism 40. To do.

  For example, as shown in FIG. 3, the program refers to a table 50 that stores the mold temperature T and the stop position S corresponding to the mold temperature T, and stores the stop position in the hydraulic servo mechanism 40. S is output.

  In the case of the table 50 shown in FIG. 3, when the temperature detected by the temperature sensor 20 is 40 ° C. or higher and lower than 50 ° C., a predetermined stop position A is defined as the stop position S. . Further, the temperature of 40 ° C. or higher and lower than 50 ° C. is defined as the reference temperature.

  When the temperature is 30 ° C. or higher and lower than 40 ° C. with reference to the stop position A, the upper punch 3 is stopped at a position lower by 0.04 mm, and the temperature is lower than 30 ° C. The upper punch 3 is stopped at a position lower by 0.08 mm. Thus, when the detected temperature is lower than the reference temperature, it is considered that the upper punch 3 contracts and the vertical dimension (the dimension in the pressurizing direction) is shortened. The vehicle is stopped at a position lower than the reference stop position A (position advanced in the pressurizing direction). Thus, the thickness dimension of the molded product 6 is prevented from being changed in the increasing direction.

  On the other hand, when the temperature detected by the temperature sensor 20 is 50 ° C. or higher with the stop position A as a reference, the upper punch 3 is stopped at a position higher by 0.03 mm. Thus, when the detected temperature is higher than the reference temperature, it is considered that the upper punch 3 is thermally expanded and the vertical dimension (the dimension in the pressurizing direction) is increased, and therefore the upper punch 3 Is stopped at a position higher than the reference stop position A (a position returned to the pressurizing direction). Thus, the thickness dimension of the molded product 6 is prevented from being changed in a thinning direction.

  FIG. 4 shows the relationship between the number of moldings, the product thickness M (average value), and the mold temperature T. First, for the product thickness M, two threshold values TH1 and TH2 are set, and when the product thickness M exists between the two threshold values TH1 and TH2, the dimensional accuracy required for the molded product 6 is high. It can be cleared. The mold temperature T is shown to increase as the number of moldings increases.

  In FIG. 4, first, when the number of moldings is increased and N1 pieces are manufactured, and the mold temperature T rises and exceeds the temperature T1, the stop position A is corrected by the program to obtain an optimal stop. The position S is set, whereby the value of the product thickness M, which is decreasing and becomes thinner than the threshold value TH1, is increased in the next molded product. Similarly, in the state where N2 pieces are manufactured, even when the mold temperature T exceeds the temperature T2, the optimum stop position S is set by correcting the stop position A by the program, and from the threshold value TH1. Can be avoided.

  As described above, in this embodiment, as shown in FIG. 1, the temperature of the mold for performing pressure molding (mold temperature T) is detected by the temperature sensor 20, and based on the temperature of the mold, The dimension L in the pressurizing direction of the cavity 5 formed by the mold is set. The dimension L is set by pressing the mold (upper punch 3) moving in the pressurizing direction. This is set by defining the stop position S at the time.

  Further, in this embodiment, as shown in FIG. 1, a temperature sensor 20 for detecting a temperature of a mold for performing pressure molding (mold temperature T), and pressurization based on a detected value of the temperature sensor 20. A controller 30 having a program for obtaining a stop position S at the time of pressurization of the mold (upper punch 3) moving in the direction, and pressurization for stopping the mold at the stop position S obtained by the controller 30 The pressure forming apparatus 100 includes the apparatus (the hydraulic servo mechanism 40 and the hydraulic rod 8).

  According to this embodiment, the prescribed stop position A of the upper punch 3 is automatically corrected according to the change in the mold temperature T, and the product thickness M of the molded product 6 is always set to the prescribed threshold values TH1 and TH2. It can be made to fall within the range. In addition, since the stop position S is determined based on the mold temperature T detected by the temperature sensor 20, even if the temperature of the environment where the pressure molding apparatus 100 is installed is changed, this environment Can respond automatically to changes in temperature.

  Further, in this embodiment, the setting of the dimension L (see FIG. 1) of the cavity 5 in the pressurizing direction defines the stop position at the time of pressurization of the mold moving in the pressurizing direction, that is, the upper punch 3. According to this, since the stop position of the mold, which is assumed to be already moved, is corrected, the correction of the stop position is changed by software without changing the device configuration. Can be implemented. That is, the dimension L can be changed by moving the lower punch 2 in this embodiment, but in this case, a new mechanism for moving the lower punch 2 is required. In the present embodiment, it is possible to cope with this by simply changing the stop position S of the moving upper punch 3 in software, which is preferable in terms of cost, simplification of the apparatus configuration, and improvement of product quality. It becomes.

  In addition, the stop position S is automatically determined as described above, thereby reducing labor such as setting work by an operator, omitting adjustment work, reducing material loss by creating a prototype, Advantages such as shortening the working time associated with these can be obtained. Further, since the product thickness M of the molded product 6 can be kept within the prescribed thresholds TH1 and TH2, it is possible to maintain the product quality even when the number of production increases.

  Further, the detection of the mold temperature T by the temperature sensor 20 is performed at least every molding cycle by the mold, for example, whenever the upper punch 3 rises after pressurization, whereby the mold temperature is determined. Can be monitored in real time, and the mold stop position during pressure molding can be corrected in accordance with the mold temperature immediately before molding. Therefore, the product dimensions can be maintained with high accuracy.

  The above embodiment is particularly suitable for powder molding for producing highly accurate sintered metal machine parts and the like because the influence of the temperature change of the mold due to frictional heat generation is large. In addition, the technology of this embodiment can be expected to contribute greatly to improvement of product accuracy in powder molding in various industries such as powder molding press manufacturers, powder molded component manufacturers, and automobile manufacturers.

The figure shown about the Example of a pressure molding apparatus. The figure shown about the temperature sensor, controller, and hydraulic servo regarding control. The figure shown about the table which defined the setting of the stop position corresponding to the metal mold | die temperature memorize | stored in a controller. The figure shown about the relationship between the number of moldings, mold temperature, and product thickness.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dies 2 Lower punch 3 Upper punch 3a Outer peripheral surface 4 Mold 5 Cavity 6 Molded product 7 Pressure plate 8 Hydraulic rod 9 Base plate 10 Powder material 20 Temperature sensor 30 Controller 40 Hydraulic servo mechanism 100 Pressure molding device

Claims (5)

  A pressure molding method in which a temperature of a mold for performing pressure molding is detected by a temperature sensor, and a dimension in a pressing direction of a cavity formed in the mold is set based on the temperature of the mold. .   The pressure molding method according to claim 1, wherein the mold temperature is detected by the temperature sensor at least for each molding cycle of the mold.   The dimension of the pressurizing direction of the cavity is set by defining a stop position at the time of pressurizing the mold moving in the pressurizing direction. 2. The pressure molding method according to 2.   A controller having a temperature sensor for detecting the temperature of a mold for performing pressure molding, and a program for calculating a stop position at the time of pressurization of the mold that moves in the pressurizing direction based on a detection value of the temperature sensor And a pressure forming device for stopping the mold at a stop position required by the controller. The pressure molding apparatus according to claim 4, wherein the mold temperature is detected by the temperature sensor at least for each molding cycle of the mold.

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