JPH0655297A - Method and device for compression controlling in powder molding press - Google Patents

Abstract

PURPOSE:To prevent a die from breaking by precisely managing a compression amount or surely preventing the interference of a punch and a step part in a cavity of a die. Further, to prevent the die from breaking by surely preventing the interference of the punch and the step part even in an idling time. CONSTITUTION:In a powder molding press of a hydraulic system or a screw system, the press is once 'stopped before the compression is finished, and then advanced to the final compression after confirming the compatibility of the compression force at one stop time. Further, the compression control of the punch 4 and the die 1 is made to a closed circuit control between a ram on which the punch 4 is connected and a die plate 2 by which the die 1 is supported, and the distance between the one time stopped top end of the punch 4 and the step part 16a of the inner circumference of the cavity 3 is set larger than the deflection amount of the punch 4 and the die plate generating due to the max. compression force to be applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control method and apparatus for a powder molding press.

[0002]

2. Description of the Related Art Conventionally, ceramics, cermet,
Various cutting tool chips made of cemented carbide are manufactured using a powder molding press. A positive type throw-away tip is an example of such a cutting tool tip. The positive type of the throw-away tip is a cutting tool tip 100, 1 such as a triangle, a quadrangle, or a rhombus as shown in FIG.
01, and the outer peripheral shape is not a straight shape but a conical shape. The portion corresponding to the conical edge is a straight portion a, and the dimension of this straight portion a is extremely small and is molded to about 10 microns.

[0003]

However, since the powder filling is a so-called slicing method in which the powder is filled into the holes of the mold using a feeder that slides on the plate surface of the die plate, the powder filling amount varies. Occurs.

In the conventional molding, for example, in the case of a mechanical press, the pressing force is about 10 tons, and the deflection of the machine and the die are about 1 mm in total. Therefore, if the powder filling amount is small, the pressing force will be small, the deflection will be small, and there will be a problem that the upper punch will enter the hole of the mold by that much, and the molding size will vary, and in extreme cases, the tip of the upper punch Interferes with the tapered step of the mold, resulting in damage to the mold.

Therefore, the straight portion a of the molded product is taken in an unnecessarily large amount, and the unnecessary portion is removed by polishing in the post-process after sintering, which not only requires an extra material, but also the post-process is troublesome and the productivity is high. There was a problem that was bad.

There is also a problem that the die is always damaged when the blank is driven to operate the press without adding the powder.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for controlling the pressure of a powder molding press capable of controlling the dimensions of a molded product more precisely. And to provide a device.

Another object of the present invention is to reliably prevent interference between the punch and the step inside the hole of the mold when molding a positive type or a similar shaped molded product of a throw-away tip. To prevent damage.

Further, it is to prevent the die from being damaged even when the blank is hit.

[0010]

In order to achieve the above object, the method for controlling the pressure of a powder molding press of the present invention comprises a mold having a stepped portion on the inner circumference of a hole filled with powder. The punch is inserted into the hole of the die to pressurize the powder. At the end of the pressurization, the step is completed in the state where the step inside the hole of the die and the punch are close to each other so as not to interfere with each other. In the pressurization control method for hydraulic or screw type powder molding presses, control is performed by temporarily stopping before pressurization and confirming that the pressurizing force at the time of stop is proper and then proceeding to final pressurization. It is characterized by doing.

Further, the pressurization control between the punch and the die is a closed circuit control between the ram to which the punch is drivingly connected and the die plate on which the die is supported. It is effective to set the distance between the inner circumference of the hole and the step portion to be larger than the amount of deflection of the punch and die plate caused by the maximum applied pressure.

It is preferable to confirm whether or not the applied pressure is appropriate a plurality of times before the final pressurization.

Further, the pressure control device for the powder molding press of the present invention is a mold in which a step portion is provided on the inner periphery of the hole for filling the powder, and the powder filled by being inserted into the hole of the mold. And a hydraulic or screw type driving means for relatively driving between the die and the punch to press the powder, and the die at the end of pressurization. In the pressure control device of the powder molding press, which terminates the pressing in a state in which the step inside the hole and the punch are close to each other so as not to interfere with each other, the pressing amount detecting means for detecting the pressing amount of the powder by the punch. And a pressing force detecting means for detecting the pressing force of the powder by the punch, and when the pressing amount detected by the pressing amount detecting means reaches a predetermined value, the pressing operation by the punch is temporarily stopped. , The pressure at the time of suspension to the pressure detection means Detection is performed, the detected pressure is compared with a preset pressure, and if the detected pressure is equal to or higher than the preset pressure, it is confirmed that the pressure is appropriate and the final pressurization is performed. And a control means for controlling the driving means.

[0014]

According to the method of controlling the pressure of the powder molding press of the present invention, the pressing operation is temporarily stopped before the end of the pressing, and it is confirmed whether the pressing force has an appropriate magnitude. The pressurization operation is restarted and the pressurization is finally performed. If the pressure is not appropriate, no further pressure is applied. It is safer to perform this confirmation operation several times.

Further, if the pressing force is not appropriate and the process of extracting the molded product is started, the punching and the die are extracted without interference, and if an error signal is issued at this time,
The product can be rejected as defective.

Further, since the relative drive control between the die and the punch is closed circuit control, the amount of deflection at the time of pressurization is only the relation between the punch and the deflection of the die plate supporting the die. The amount is small, and in consideration of this amount, if you allow a little more than this amount of deflection and pause for a moment, in the worst case, the punch will not be It does not interfere with the step on the inner circumference of the hole of the mold, and the mold is not damaged.

Further, according to the pressure control device of the powder molding press of the present invention, the temporary stop position of the punch is detected by the pressurization amount detection means, and the control device includes the drive means for relatively driving between the die and the punch. Stop. Then, the pressing force detecting means detects the pressing force at that time, compares it with a preset pressing force, and when the detected value is equal to or more than the setting pressing force, restarts the driving of the driving means by the control device and finally. Pressurize.

Further, when the detected value is smaller than the set pressing force, the driving of the driving means is stopped and the final pressurization is not performed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. FIG. 4 shows a dual pressure type powder molding press to which the method and apparatus for controlling the pressure of the powder molding press according to an embodiment of the present invention are applied.

This powder molding press is roughly composed of a mold 1 and
Die plate 2 supporting this mold 1 and holes 3 of the mold 1
It has an upper punch 4 and a lower punch 5 inserted from above and below, and the die plate 2 is fixed to a machine frame 6.

On the other hand, the upper punch 4 is supported by an upper punch plate 7, and the upper punch plate 7 is connected to an upper ram 9 driven by an upper cylinder 8 which is a hydraulic drive means.

The lower punch 5 is the lower punch plate 1
The lower punch plate 10 is connected to a lower ram 12 driven by a lower cylinder 11.

Then, the upper punch 4 and the lower punch 5 are
The powder 13 filled in the holes 3 of the mold 1 is driven by the lower cylinders 8 and 11 from above and below to be pressed into a predetermined shape.

Even in this embodiment, the molded product will be described by taking as an example the case of molding positive type cutting tool tips 100 and 101 having a tapered outer periphery which is inclined in an inverted conical shape as shown in FIG. It shall be.

That is, the hole 3 of the die 1 is a straight large-diameter hole 14 into which the upper punch 4 is inserted, a straight small-diameter hole 15 into which the lower punch 5 is inserted, and the large-diameter hole 14 and the small-diameter hole. It is composed of a taper hole 16 connecting between 15.

Between the upper punch plate 7 and the die plate 2, a linear sensor 17 for the upper ram serving as a pressurizing amount detecting means is mounted. The displacement amount of the ram 9 is detected, and the pressure amount X of the upper punch 4 is calculated from the displacement amount of the upper ram 9.

A lower ram linear sensor 18 is mounted between the lower punch plate 10 and the die plate 2, and the lower ram linear sensor 18 allows the lower ram 1 to move.
The moving amount of 2 is also detected.

The drive of the upper ram 9 is controlled by the upper ram linear sensor 17 under closed circuit control, that is, closed loop control.

FIG. 6 shows the upper ram 9 and the lower ram 12.
2 shows a control circuit for driving and controlling the. That is, the hydraulic pressure supplied from the hydraulic pressure source circuit 201 to the upper cylinder 8 is controlled by the hydraulic servo valve 202, and the displacement amount detected by the upper ram linear sensor 17 is controlled by the computer 207.
The position of the upper ram 9 is accurately controlled by feeding back to 3.

Upper punch plate 7 and die plate 2
The linear sensor 17 for the upper ram, which is mounted in between, should be as close to the upper punch 4 and the die 1 as possible.

Similarly, the lower ram 12 is also controlled by closed loop control, in which the hydraulic pressure supplied from the hydraulic pressure source circuit 204 is controlled by the hydraulic servo valve 205, and the lower ram linear sensor 18 is used. Servo controller 2 detects the displacement of lower ram 12
By feeding back to 06, the control position of the lower ram 12 is accurately controlled.

In this embodiment, the step 16a at the boundary between the tapered hole 16 and the large diameter hole 14 inside the die 1 and the upper punch 4 are close to each other at the end of the pressurization so as not to interfere with each other. Pressurization is finished.

FIG. 1 shows a schematic structure of a pressurizing control device for the powder molding press. This pressurizing control device is a linear presser for the upper ram as a pressurizing amount detecting means for detecting a pressurizing amount. A sensor 17, a pressing force detecting load cell (strain gauge) 19 as a pressing force detecting means for detecting the pressing force, and an amount of pressurization detected by the upper ram linear sensor 17 and the pressing force detecting load cell 19. And a control means 20 for controlling the pressurization of the upper punch 4 based on the applied pressure.

At the end of pressurization, the step 16a at the boundary between the large diameter hole 14 and the tapered hole 16 in the hole 3 of the die 1 and the upper punch 4 are close to each other by a dimension a so as not to interfere with each other. Pressurization is completed with.

As the pressing force detecting means, various detecting means such as a piezoelectric element, a minute displacement meter, a hydraulic damper, etc. can be used in addition to the load cell.

The pressing force detecting load cell 19 is attached to a portion of the machine where the strain is generated, and the change in resistance when the strain is applied is taken out and converted into a pressing force. In the example of FIG. 4, it is attached to the outer periphery of the upper ram 9, but it may be attached to the upper punch 4 as shown in FIG. In addition, as shown in FIG.
May be detected.

FIG. 5 shows a circuit diagram of the control means.

That is, the amplifier 301 that amplifies the detection signal from the load cell 19 for detecting the pressing force, and the peak hold circuit 3 that holds the peak value of the amplified detection signal.
02, the digital setters 303 and 304 for setting the pressure force obtained in advance, and the digital setters 303 and 30
Digital-to-analog converters 305, 30 for converting the digital signal set by 4 into an analog signal
6, comparators 307 and 308 for comparing the analog signal of the set pressurization force converted by the digital-analog converters 305 and 306 with the analog signal of the detected pressurization force held by the peak hold circuit 302, and the comparator 307. , 308, and first and second contact points 309 and 310 that are switched according to the output signal. The value held by the peak hold circuit 302 is displayed on the digital display 311.

The minimum applied pressure at the first contact 309 is
The maximum pressure is determined at the second contact point 310.

It is appropriate if the applied pressure at the first contact 309 exceeds the set value to become the A contact and the applied pressure at the second contact 310 remains at the A contact. In other cases, give a signal to stop the machine or bounce the product.

The pressure display at this time does not need to have the second contact 310, and the purpose can be achieved by outputting a signal when the pressure is low. The setting of the maximum pressing force by the second contact 310 is
This is to repel a molded product having an excessively large powder filling amount and an excessively large size.

Next, the molding process by the powder molding press having the above-mentioned structure will be described with reference to the process chart of FIG. 2 and the flow chart of FIG.

First, as shown in FIG. 2 (a), the powder 13 is put into the feeder 21, and after the feeder 21 escapes, a pressurizing step is started, and pressure is applied by the upper and lower punches 4 and 5, and FIG. When the pressurization is completed, the process is temporarily stopped as shown in (see steps 1 to 3).

This temporary stop position is the amount of deflection of the area outside the closed loop control range when the maximum pressing force is applied, that is, the contraction of the upper punch 4 and the die plate 2 when the final pressing force P0 is applied. It is set to be larger than the amount of deflection. This amount may be calculated, or may be actually measured by actually applying force.

Then, the pressing force Px is measured by the pressing force detecting load cell 19 attached to the upper ram 9 to confirm whether the pressing force is proper or not, and the preset pressing force value Pxo or more is inputted. 2C, the process proceeds to the next final pressurizing step, and after pressurization is completed, the product is extracted as shown in FIG. 2D (see steps 4 to 6).

That is, the set pressure Pxo and the detected pressure P
If x is compared and the detected pressure Px is low, powder 13
Therefore, the upper punch 4 enters too much and interferes with the step portion 16a of the inner periphery of the hole 3 of the die 1.

On the other hand, if it is not within the proper range,
As shown in FIG. 2 (e), the upper punch 4 and the lower punch 5 are raised to extract the product (see step 7), and an error signal is displayed to reject the product as a defective product.

FIG. 7 shows a withdrawal type powder molding press to which the pressure control method and apparatus of the present invention are applied. This powder molding press has basically the same configuration as the powder molding press shown in FIG. 4, and the same components will be denoted by the same reference numerals. The powder molding press will support the lower punch 5. The lower punch plate 10 is fixed to the machine frame 6, and the die plate 2 is driven by the lower ram 12.

The upper ram linear sensor 17 'is mounted between the upper punch plate 7 and the fixed lower punch plate 10. Further, in place of the lower ram linear sensor 18, a die linear sensor 18 ′ is mounted between the lower punch plate 10 and the die plate 2. Since what is actually required is between the upper punch plate 7 and the die 1, the computer determines the upper ram 9 and the die 1 based on the detection lengths from the upper ram linear sensor 17 'and the die linear sensor 18'. The amount of pressurization may be calculated by calculating the interval, and the linear sensor 17 for the upper ram 17 may be provided between the upper punch plate 7 and the die 1.
It is also possible to arrange ′ and detect the amount of pressurization directly.

FIG. 8 shows a pressurizing step of the powder molding press of this withdroal method. As in the case of both pressure methods, first, as shown in FIG.
3 is filled in the hole 3 of the die 1, and then the die plate 2 and the upper punch 4 are lowered at a predetermined speed difference to pressurize the powder 13 as shown in FIG. 8 (b). When the fixed amount is reached, the operation is temporarily stopped, the pressing force is detected by the load cell 19 for detecting the pressing force, and it is confirmed whether the pressing force is within the set range.
If it is within the set range, the final pressurization is performed as shown in Figs. 8 (c) and (d), and the product is removed. If it is outside the set range, the final pressurization is performed as shown in Fig. 8 (e). Instead, the die plate 2 is lowered and the upper punch 4 is raised to extract the product.

In this embodiment, a cutting tool tip such as a positive type throw-away tip has been described as an example of the molded product, but the present invention is not limited to such a cutting tool tip and powder molding of various similar shapes is possible. Can be applied.

Further, the present invention is not limited to such a positive type shape, and the pressure molding of a molded product such as a cutting tool chip having a straight outer periphery should be temporarily stopped just before the final pressure completion position. It is also possible to confirm the applied pressure and control so as to perform the final pressurization when appropriate. In such a case, there is no step on the inner circumference of the hole in the die, and there is no risk of damage to the die even if the amount of punch inserted into the hole is large, but there is variation in the dimension of the molded product due to variations in the filling amount. In particular, it is possible to reject defective products when the filling amount is small and the prescribed size is not reached.

Further, although the hydraulic press has been described as an example in this embodiment, the present invention can be similarly applied to a screw press. In the case of a screw type press, for example, a ball screw is used, and if this ball screw is controlled by a servomotor, it can be precisely controlled as in this embodiment.

[0054]

EFFECTS OF THE INVENTION The present invention has the above-mentioned structure and action. The pressurizing operation is temporarily stopped before the pressurization is completed, and it is confirmed whether or not the pressurizing force has an appropriate magnitude. Since the pressurization operation is restarted and the pressurization is finally performed,
There is no risk of the punch interfering with the stepped portion of the inner periphery of the hole of the mold due to the variation in the powder filling amount, and damage to the mold can be reliably prevented.

Further, when the applied pressure is not appropriate, the extraction process is started without further pressurization, and if an error signal is issued at this time, the product can be rejected as a defective product and the productivity is improved. be able to.

Further, by making the relative drive control between the die and the punch a closed circuit control, it is only necessary to consider the deflection amount only for the relation between the die and the punch plate, and a slightly larger amount than this deflection amount is expected. In the worst case, there is no risk of the punch interfering with the step on the inner circumference of the hole in the die, even if the pressurizing operation is performed without powder entering in the worst case. Does not cause damage to the mold.

It is safer to confirm the applied pressure several times before the final pressurization.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing the configuration of a pressure control device for a powder molding press according to an embodiment of the present invention.

FIG. 2 is a process diagram showing a pressure control process of the powder molding press of the present invention, where FIG. 2 (a) is a powder filling process, FIG. 2 (b) is a temporary stopping process, and FIG. 2 (c). Is a final pressurizing step, FIG. 7D is a regular extraction step, and FIG. 8E is a schematic cross-sectional view showing a defective extraction step.

FIG. 3 is a flow chart showing a procedure of pressure control of the powder molding press of the present invention.

FIG. 4 is a schematic configuration diagram of a powder molding press to which the present invention is applied.

5 is a circuit diagram showing an example of pressing force detection means of the powder molding press of FIG.

FIG. 6 is a drive control circuit diagram of the powder molding press of FIG. 4.

FIG. 7 is a schematic configuration diagram of a withdrawal type powder molding press to which the method and apparatus for controlling the pressure of the powder molding press of the present invention is applied.

8 shows a pressing step of the withdrawal type powder molding press of FIG. 7, where FIG. 8 (a) is a powder filling step, FIG. 8 (b) is a temporary stopping step, and FIG. 8 (c). Is a final pressurizing step, FIG. 7D is a regular extraction step, and FIG. 8E is a schematic cross-sectional view showing a defective extraction step.

9 (a) is a plan view showing an example of a positive type of a throw-away tip as a molded product, FIG. 9 (b).
6A is a cross-sectional view of FIG. 7A, FIG. 7C is a plan view showing another example of the throw-away tip, and FIG. 6D is a cross-sectional view of FIG.

[Explanation of symbols]

1 die 2 die plate 3 hole 4 upper punch 5 lower punch 6 machine frame 7 upper punch plate 8 upper cylinder (driving means) 9 upper ram 10 lower punch plate 11 lower cylinder 12 lower ram 13 powder 14 large diameter hole 15 small diameter hole 16 Tapered hole 16a Stepped portion 17 and 17 'Linear sensor for upper ram (pressurizing amount detecting means) 19 Load cell for pressing force detection (pressurizing force detecting means) 20 Control means

Claims (8)

[Claims] 1. A method of controlling the pressure of a hydraulic or screw type powder molding press in which a punch is inserted into a hole of a die to pressurize the powder filled in the hole, and the powder is temporarily stopped before the end of the pressurization. Then, the method for controlling the pressure of the powder molding press is characterized in that after confirming that the applied pressure at the time of temporary suspension is proper, the process proceeds to the final pressing. 2. The die according to claim 1, wherein a step portion is provided on the inner periphery of the hole of the die, and when the pressurization is completed, the step portion and the punch are brought close to each other so as not to interfere with each other. A pressure control method for a powder molding press. 3. The method for controlling the pressure of a powder molding press according to claim 1, wherein when the pressing force at the time of temporary stop is not appropriate, the process proceeds to the molding product extracting step and at the same time an error signal is issued. 4. The pressurization control between the punch and the die is closed circuit control between a ram to which the punch is drivingly connected and a die plate on which the die is supported. The pressure control method for a powder molding press according to claim 1 or 2, wherein the distance between the inner periphery of the hole and the step is larger than the amount of deflection of the punch and die plate caused by the maximum applied pressure. 5. The pressure control method for a powder molding press according to claim 1, wherein confirmation as to whether or not the applied pressure is appropriate is performed a plurality of times before final pressing. 6. A die having a hole filled with powder, a punch for pressurizing the powder filled in the hole of the die, and a hydraulic type for relatively driving between the die and the punch. Alternatively, in a pressure control device for a powder molding press, comprising a screw type driving means, a pressure amount detection means for detecting a pressure amount of the powder by the punch, and a pressure force for detecting a pressure force of the powder by the punch. When the amount of pressurization detected by the detection unit and the amount of pressurization detection unit reaches a predetermined value, the pressing operation by the punch is temporarily stopped, and the pressing force at the time of temporary stop is set by the pressing force detection unit. The detected pressure is compared with a preset pressure, and when the detected pressure is equal to or higher than the preset pressure, it is confirmed that the pressure is appropriate and the final pressurization is performed. Control hand for controlling hydraulic or screw drive means A pressure control device for a powder molding press, comprising: a step. 7. A die having a stepped portion on the inner circumference of a hole filled with powder, a punch for pressurizing the powder filled in the hole of the die, and a die and a punch. And a hydraulic or screw drive means for driving the powder, and at the end of pressurization, the step inside the hole of the die and the punch are close to each other so as not to interfere with each other, and the powder is terminated. In a pressurizing control device for a molding press, a pressurizing amount detecting means for detecting a pressurizing amount of powder by the punch, a pressurizing force detecting means for detecting pressurizing force of the powder by the punch, and a pressurizing amount detecting means. When the detected pressurization amount reaches a predetermined value, the pressurizing operation by the punch is temporarily stopped, the pressurizing force at the time of the temporary stop is detected by the pressurizing force detecting means, and the detected pressurizing force is preset. The detected pressure is set by comparing A powder molding press comprising: a control means for controlling the hydraulic or screw type drive means so as to confirm that the pressure is appropriate when the pressure is equal to or higher than the pressure and to proceed to final pressurization. Pressure control device. 8. The relative drive control between the die and the punch is a closed circuit control for feeding back the detected pressurization amount detected by the pressurization amount detection means to control the target pressurization amount, and temporarily stopping the punch tip. The pressurization control of the powder molding press according to claim 6 or 7, wherein the distance between the mold and the step on the inner circumference of the hole of the die is set to be larger than the amount of deflection of the punch and the die plate caused by the maximum applied pressure. apparatus.