JPH07115234B2 - Method of correcting pressure position in powder molding press - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a powder molding press,
The present invention relates to a method for correcting a pressurizing position for improving the thickness accuracy of a powder molded product in the pressurizing direction.

[0002]

2. Description of the Related Art The processing accuracy of a molded product in a conventional powder molding press is controlled as follows.

A first method is a method of removing a defective product by measuring a thickness dimension after extracting a molded product for which molding has been completed from a mold and judging whether the product is good or bad.

The second method is to correct the pressure position after the next cycle by controlling the tendency after measuring the dimension of the molded product.

The third method is a method of providing a mechanical stopper for controlling the amount of pressurization to a predetermined size in a portion closer to the mold.

A fourth method is a method of forming a closed loop by a pressure drive mechanism and a position sensor attached to a portion closer to the mold, and controlling the pressure drive mechanism by servo control.

[0007]

In the powder molding press, in order to stably obtain both sides of a certain size, the positioning accuracy of the pressure drive mechanism is important, and how to deal with the powder filling variation. Was the biggest problem.

That is, even if the positioning by the pressurizing drive mechanism is operating normally, the mold position can be changed due to the deflection change of the die set, the pressurizing drive mechanism, the frame, etc. accompanying the load change due to the variation of the powder filling amount. It varies with each molding cycle.

However, in the first conventional method, the quality of the dimension is determined after the completion of the pressurizing step, and only the products are selected, and the occurrence of defective products cannot be dealt with.

Further, in the second method, even if an attempt is made to feed back the judgment result, since the pressurizing position is corrected by the trend control after the next cycle, it is not possible to deal with the variation in powder filling, which causes a problem. Contributes little to the solution of.

In the third method, the above-mentioned deflection is absorbed by the stopper so as to reduce the influence on the mold position, and although some effect can be seen, the variation per molding cycle still remains.

Further, there is a new problem that the stopper must be replaced and the height of the stopper must be adjusted every time the target molded product is changed and the dimension of the molded product is further adjusted.

Therefore, as a fourth method, a method is conceivable in which a portion as close as possible to the mold is constituted by a closed loop to suppress the mold position fluctuation due to the deflection of the mold, tool set, frame and the like. Method 4 is theoretically the best technology among the existing technologies.

However, when the fourth method is adopted, the following various problems occur.

First, since the powder molding press generally has a large die height and a large stroke of the pressure drive mechanism, the deflection generated in the closed loop becomes large,
If an attempt is made to improve the positioning accuracy by incorporating the amount of deflection as a deviation into a closed loop, vibration will occur, making molding impossible.

Further, since the load during pressurization is large, the weight of the pressurizing drive mechanism and the sliding resistance of the pressurizing drive mechanism are large,
It affects the closed loop control and the operation delay becomes large. Also, vibration and noise are likely to occur.

In particular, in the most common tool set type powder molding press, if the tool set is also included in the closed loop control, the clearance between the press body and the tool set tends to cause vibration.

In order to eliminate the occurrence of vibration, the loop range must be retracted from the vicinity of the mold or the control gain (sensitivity) must be lowered, which eventually results in a decrease in positioning accuracy.

Further, in order to reduce the above-mentioned deflection, it is considerably costly to increase the rigidity of each portion such as the frame or to reduce the sliding resistance until the effect is exhibited.
Furthermore, new inventions and technological developments are needed.

The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to stabilize a non-defective product having high dimensional accuracy without being affected by the variation in powder filling amount. It is an object of the present invention to provide a method for correcting the pressing position of the powder molding press for obtaining it.

[0021]

In order to achieve the above object, in a method of correcting a pressing position in a powder molding press of the present invention, a mold is driven by a pressing drive mechanism to move the powder.
Pressurization stop position before the end pressurization stop position
Pressurize with a pressure sensor, and the position sensor provided near the mold detects the pressure stop position in front of the mold and stops the target pressure.
It is characterized in that a position arrival shortage amount with respect to a position is calculated, and a pressurizing drive mechanism is driven based on the calculated position arrival shortage amount to correct pressure.

[0022]

The final positioning error of the mold is minimized by applying a predetermined amount of pressure to the pressing stop position in front of the mold and correcting and pressing the amount of insufficient arrival of the mold relative to the target pressing position. You can stay.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

FIG. 1 shows a first embodiment of a powder molding press to which the method for correcting the pressing position of the powder molding press of the present invention is applied.

In the figure, reference numeral 1 denotes the entire powder molding press, and in general, a press body 2, a tool set 3 assembled to the press body 2, an upper punch 4 of the tool set 3 and a die body 8 are vertically moved. It is composed of upper and lower drive mechanisms 6 and 7 which constitute a pressure mechanism for driving.

The press body 2 is composed of an upper frame 21, a lower frame 22, and left and right column portions 23 connecting the upper frame 21 and the lower frame 22. The tool set 3 is mounted between the upper frame 21 and the lower frame 22, and is fixed to the pedestal portion 24 at the upper end of the lower frame 22.

The tool set 3 includes a die plate 31 and
An upper punch plate 32 arranged above the die plate 31, a lower punch plate 33 arranged below the die plate 31, and a lowering plate 34 arranged further below the lower punch plate 33 are provided. There is.

The upper and lower punch plates 32 and 33, which constitute a die, are coaxially fixed with the upper and lower punches 4 and 5, and the upper and lower punches 4 and 5 are provided in the center of the die plate 31. It is adapted to be inserted into the hole 9 of the mold body 8 from above and below.

A connecting rod 35 slidably inserted into a through hole 33a formed in the lower punch plate 33.
The pull-down plate 34 and the die plate 31 are integrally connected to each other with the die plate 31 and the pull-down plate 34 integrally moved up and down. In addition, the guide rod 36 which is vertically installed on the die plate 31 and extends upward.
Is slidably inserted into a guide hole 32a provided in the upper punch plate 32, and the upper punch plate 32 is vertically moved in parallel with the die plate 31 via the guide rod 36.

On the other hand, as the upper and lower drive mechanisms 6 and 7, screw pressing mechanisms are adopted in this embodiment.

The upper drive mechanism 6 includes an upper nut 62 rotatably supported on the upper frame 21 via a bearing 61.
An upper screw shaft 63 screwed to the upper nut 62, a servo motor 65 with an encoder 64 arranged adjacent to the upper nut 62, and a rotational driving force of the servo motor 65 transmitted to the upper nut 62. Power transmission means 66 such as a gear mechanism. The lower end of the upper screw shaft 63 is located at the upper punch plate 32 of the tool set 3.
It is connected and fixed by a holding plate 67.

The lower drive mechanism 7 includes a lower nut 72 rotatably supported on the lower frame 22 via a bearing 71.
A lower screw shaft 73 screwed into the lower nut 72, a servo motor 75 with an encoder 74 arranged adjacent to the lower nut 72, and a rotational driving force of the servo motor 75 transmitted to the lower nut 72. And a power transmission means 76 such as a gear mechanism. Then, the upper end of the lower screw shaft 73 is connected and fixed to the pull-down plate 34 of the tool set 3.

When the upper screw shaft 63 is moved downward to pressurize the powder 11, an upward pressure reaction force acts on the bearing 61 mounting portion of the upper nut 62 with which the upper screw shaft 63 is screwed. , The pedestal portion 24 of the lower frame 22 to which the lower punch plate 33 is fixed via the lower punch 5, and the die plate 3
A downward pressure reaction force acts on the bearing 71 mounting portion of the lower screw shaft 73 via the mold 8 of 1, the lowering plate 34, and the lower screw shaft 73.

A position sensor 10 for detecting the pressure position of the upper punch 4 is provided between the upper punch plate 32 and the lower punch plate 33 of the tool set 3. The position sensor 10 is provided closer to the upper punch 4 so as not to be affected by bending of each part. Although the illustrated example is attached to the tool set 3, it may be attached to the upper punch 4, the lower punch 5, the die itself such as the die body 8. In this embodiment, for example, a linear scale sensor is used as the position sensor 10, and the pressure position of the upper punch 4 is detected by detecting the interval between the upper and lower punch plates 32, 33.

FIG. 2 shows a control block diagram of the powder molding press of FIG.

The control system is roughly composed of a positioning control system 100 as positioning means for the pressing position and a correction control system 110 as position monitoring means for monitoring the pressing position.

The positioning control system 100 includes a control command system 10
1, the servo controller 102, and the servo amplifier 10
3, the above-mentioned servo motor 65, and encoder 64
The servo controller 1 detects the rotation amount of the servo motor 65 by the encoder 64.
A closed loop that feeds back to 02 is configured, and the drive of the servo motor 65 is controlled based on the target pressurization position information commanded by the control command system 101.

Then, the driving force of the servo motor 65 is transmitted to the upper punch 4 as a mold through the drive transmission system 105 such as the upper nut 62, the upper screw shaft 63, the tool set 3 and the like.

Instead of the encoder 64 of the positioning control system 100, a sensor may be provided in the drive transmission system 105 and the amount of movement thereof may be feedback-controlled. For example, the sensor may be installed on the upper frame 21 and the upper punch plate 32.
The nut 6 may be provided between them to detect the amount of movement of the upper punch plate 32 or the upper screw shaft 63, or may be provided on the upper surface of the upper frame 21 to detect the amount of movement of the upper screw shaft 63.
The rotation amount of 2 may be detected, and the rotation amount of the gear of the power transmission means 66 may be detected. In short, a sensor is provided at a portion where the driving amount of the upper drive mechanism 6 can be detected. You can leave it.

Further, the correction control system 110 as a position monitoring means for monitoring the position of the upper punch 4 includes the position sensor 10
And a signal processing comparator 104 for processing the pressure position signal detected by the position sensor 10. Then, the signal processing comparator 104 calculates the position arrival shortage amount with respect to the target pressurization position of the upper punch 4, and inputs the data of the position arrival shortage amount to the control command system 101 of the positioning control system 100 as a control target to perform servo control. The motor 65 is driven and controlled. Although the position sensor 10 is provided closer to the upper punch 4 as described above, it does not detect the movement of the upper punch 4 itself, but rather, for example, the upper screw shaft 63 of the drive transmission system 105. Alternatively, the movement amount of the upper punch plate 32 or the movement amount of the upper punch 4 such as the rotation amount of the upper nut 62 or the gear of the power transmission means 66 may be detected.

Next, the pressing process of the powder molding press of this embodiment will be described.

This embodiment is an example in which the pressing position of the upper punch 4 is positioned by the servo motor 65 and the encoder 64 via the upper screw shaft 63. In the figure, the position sensor 10 is arranged near the upper punch 4. The distance between them is detected, and is corrected by the servo motor 65 so that the height of the molded product becomes h dimension.

Generally, the target pressurizing position information is the product thickness, but a slightly different value may be set due to various factors such as springback. In this embodiment, in order to calculate the position arrival shortage amount, as shown in FIG. 3D, the position to be stopped is the pressure stop position before the h dimension.
h ′, and the shortage amount Xα (Δa) for that position, and h
The amount of movement Δh remaining up to the dimension is added to obtain the correction amount.
It h '' is a mold aiming at the pressure stop position h'in front
Is the pressure stop position in front of you when
It

First, as a target pressurizing position information of the upper punch 4, a pressurizing stop position h'in front and a pressurizing target h corresponding to the product thickness are given to the control command system . Servo controller 102, servo amplifier 103, a servo motor 65, and the positioning control system 100 from the encoder 64,
Rotate the upper nut 62 by a predetermined amount to move the upper punch 4
To move . The positioning control system 100 includes an upper nut 6
2 is rotated by a predetermined amount under dynamic on screw shaft 63, the hand performs by inserting the upper punch 4 into the bore 9 of the mold body 8 pressurization step
Stop at the previous pressurization stop position h ' (FIGS. 3A and 3B)
reference). The closed loop range of the positioning control system 100 is set to a range that is not affected by the bending of the press body 2.

Here, it is affected by the deflection of the press body 2.
If the closed loop range is exceeded, the positioning control system 1
Even if the feed amount of the upper drive mechanism 6 by 00 is the same,
Upper and lower punches 4, 5 due to variations in filling of powder 11
The load acting on the tool fluctuates, and the deflection of the tool set 3, the upper drive mechanism 6, the lower drive mechanism 7, the column portion 23 of the press body 2 and the like fluctuates. It fluctuates.

Therefore, the position sensor 10 detects the actual pressurizing stop position h ″ before the upper punch 4, and the information of the detected actual pressurizing stop position h ″ before the signal is processed by the signal processing comparator 104. Signal processing at the pressurization stop position in front
Dimensional error Δa with respect to position h'and target pressurization stop position
Pressing the actual front by adding the remaining movement amount to h
A position arrival shortage amount Δh with respect to the stop position h ″ is calculated.

Then, the calculated dimensional error Δh is input to the control command system 101 as a corrected pressurization amount, a control command is newly given from the control command system 101, and correction correction is performed as shown in FIG. Apply pressure to correct the dimension of the molded product.

By this correction pressurization, a molded product having a predetermined size can be obtained even if the powder filling amount varies.

This series of correction positioning can be repeated several times.

That is , the pressurization stop position h ″ before the upper punch 4 with respect to the dimension of the molded product is detected by temporarily stopping in the middle of the pressurizing step, and an error from the desired size at that time is detected. The correction process to perform the correction pressurization corresponding to
By setting multiple pressure stop positions in front,
It is also possible to end the pressurization by changing the target pressurization stop position and repeating the correction pressurization several times.

In the above description, the case where the pressurization stop position of the upper punch 4 is corrected has been described as an example. However, depending on the shape of the molded product, the stop position of the die body 8 is detected and the servo motor 65 is used to move the die. It is also possible to correct the position of the mold body 8.

FIG. 4 shows a second embodiment of the powder molding press to which the present invention can be applied. Hereinafter, the same components as those in the first embodiment will be described with the same reference numerals.

In the second embodiment, a crank mechanism is used as the upper and lower pressure mechanisms 26 and 27 instead of the screw pressure mechanism.

The upper drive mechanism 26 includes a crankshaft 261 swingably supported by the upper frame 21, and a connecting rod 262 connecting the crankshaft 261 and the upper ram 263.
And an encoder 26 for driving the crank shaft 261.
4 and a servo motor 265.
The upper ram 263 is the upper punch plate 3 of the tool set 3.
It is connected and fixed to the No. 2 by a holding plate 267. Also in this embodiment, the drive transmission system 105 is used instead of the encoder 264.
It is also possible to provide a sensor at and to perform feedback control of the movement amount. For example, a sensor
1 may be provided between the upper ram and the upper ram to detect the position of the upper ram 263, and the swing angle of the crank shaft 261 may be detected. It may be detected, and in short, a sensor may be provided at a site where the drive amount of the upper drive mechanism 6 can be detected.

The lower drive mechanism 27 has a crankshaft 271 swingably supported by the lower frame 22, and a connecting rod 272 connecting the crankshaft 271 and the lower ram 273.
And an encoder 27 for driving the crankshaft 271
4 and a servo motor 275.
The lower ram 273 is the lowering plate 3 of the tool set 3.
4 is connected and fixed. The servo motors 265, 2
For 75, it does not matter whether or not a speed reducer is provided.

Then, the crank shaft 261 is swung by the servo motor 265, and the upper ram 2 is moved through the connecting rod 262.
Move 63 up and down.

The rest of the configuration is the same as that of the first embodiment, so its explanation is omitted. Further, the control block diagram is also the same as that of the first embodiment shown in FIG. 2, and therefore its explanation is omitted.

FIGS. 5 (a) and 5 (b) show an example in which an adjusting mechanism is attached to the press shown in FIG. That is, by providing such an adjusting mechanism, even if the pressing position of the upper punch or the die is changed, the pressing can be ended near the bottom dead center where the force is most exerted against the torque of the servo motor.

There are two general adjustment methods: a method for adjusting the distance between the ram and the punch, and a method for adjusting the distance between the crankshaft and the ram.

FIG. 5A shows a method of adjusting the distance between the ram and the punch, which is an adjusting screw portion 26 fixed to the upper punch plate 32.
6 is screwed into the upper ram 263, and the adjustment screw portion 266
The phase angle of the crankshaft 261 when pressure is applied by the upper punch 4 can be adjusted to near the bottom dead center by adjusting the amount of screwing in.

FIG. 5 (b) shows a method for adjusting the distance between the crank shaft and the ram. The adjusting screw portion 276 fixed to the lower ram 273 is screwed into the connecting rod 272 connected to the crank shaft 271 to adjust the adjusting screw portion 276. The amount of screwing in is adjusted.

Next, FIG. 6 shows a third embodiment of the powder molding press to which the present invention can be applied. Hereinafter, the same components as those in the first embodiment will be described with the same reference numerals.

In this example, both pressure systems are used. As the upper and lower pressure drive mechanisms 16 and 17, upper and lower fluid pressure cylinders 163 and 173 are used instead of the screw pressure mechanism of the first embodiment.
Upper and lower servo valves 165 and 175 and lower encoder 1
The upper punch 4 and the lower punch 5 are positioned by the upper and lower pistons 168 and 178 at 64 and 174, respectively.

Then, upper and lower position sensors 111 and 112 are provided both near the upper punch 4 and near the lower punch 5, and between the upper punch 4 and the die body 8 and between the lower punch 5 and the die body 8. By monitoring the distance, the height of the molded product is h1 and h2, respectively.
The upper servo valve 165 corrects the position of the upper punch 4, and the lower servo valve 175 corrects the position of the lower punch 5.

In the third embodiment, the die plate 131 of the tool set 13 is fixed to the pedestal portion 24 of the lower frame 21 of the press body 2, and the lower punch plate 133 is used.
And the pull-down plate 134 are integrally connected by a connecting rod 135.

A rotation stopper plate 137 is provided between the lower punch plate 133 and the pull-down plate 134, and the connecting rod 135 is inserted into the through hole 137a of the rotation stopper plate 137 to prevent the lower punch plate 133 from rotating. There is. The detent plate 137 is connected to the die plate 131 by a fixed rod 138.

An encoder 164 is mounted between the upper end of the piston rod 168a of the upper pressurizing drive mechanism 16 and the upper end surface of the upper fluid pressure cylinder 163, and positioning by the upper servo valve 165 is performed by the piston rod of the fluid pressure cylinder 16. The control of the movement amount of 168a is performed by forming a closed loop. Therefore, the deflection of the press body 2 and the tool set 13 is not included in this closed loop range.

On the other hand, the upper end of the piston rod 178a of the lower pressurizing drive mechanism 17 is connected and fixed to the pull-down plate 134, and the lower end of the piston rod 178a projects below the lower frame 22. This projecting end and the fluid pressure cylinder 17 A lower encoder 174 for detecting the feed amount of the piston rod 178a is provided between the lower encoder 174 and the lower end surface. Therefore, the closed loop range of the lower drive mechanism 17 does not include the influence of the bending of the press body 2 or the tool set 13.

Of course, the upper and lower encoders 164,
Instead of 174, for example, a sensor is provided between the upper and lower frames 21 and 22 and the upper punch plate 132 and the lowering plate 134 to detect the amount of movement of the upper punch plate 132 and the lowering plate 134 and perform feedback control. In other words, it is sufficient to provide a sensor at a site where the drive amounts of the upper and lower drive mechanisms 6 and 7 can be detected.

FIG. 7 shows a control block diagram of the powder molding press of the third embodiment.

That is, the positioning control systems 201 and 202
There are two systems of the upper servo valve 165 and the lower servo valve 175, and the correction control systems 211 and 212 also have the two systems of the upper and lower position sensors 111 and 112.

Since the control procedure is exactly the same as that of the first embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

In the above embodiments, the case where the positioning control system of the pressurizing drive mechanism is closed loop control has been described as an example, but various control configurations such as open loop control and semi-closed control can be adopted.

FIG. 8 shows a control example in which the positioning control of the upper pressure drive mechanism 6 of FIG. 2 is open loop control.

This control system uses a pulse motor 365 instead of the servo motor 65 of the configuration shown in FIG. 2, and includes a control command system 301, a step controller 302, a pulse distribution / excitation circuit 303, and a pulse motor 365. The positioning control system 300 is constituted by

On the other hand, the mold pressing position correction control system 310
However, the position sensor 10 provided near the driving device or the mold
The configuration of the signal processing comparator 304 is similar to that of the above embodiment.

As a matter of course, the first and second embodiments can be of the double-press type as in the third embodiment. In this case, the lower drive mechanism 7 may be controlled in exactly the same way as the upper punch 5 shown in FIG.

Further, in the above embodiments, the case where the screw pressurizing mechanism, the crank mechanism, and the fluid pressure cylinder are used as the pressurizing drive mechanism has been described as an example, but this is merely an example, and other crank mechanisms are shown. As a similar example, it is needless to say that various pressure drive mechanisms such as a link mechanism such as a toggle and an elliptical gear mechanism can be applied.

[0079]

As described above, according to the present invention, the pressurizing drive mechanism is driven to the pressurizing stop position before the target pressurizing position, and the position sensor provided in the vicinity of the mold is used to drive the pressurizing mechanism. Detects the pressurization position of the mold and reaches the target pressurization position
Of the position reaching a deficiency of the mold is calculated, by applying the correction pressure to the insufficient amount, the final positioning error can be minimized, without such vibration as in the prior art arises,
It can be molded quickly and with high precision.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic structure of a powder molding press according to a first embodiment of a method for correcting a pressing position of a powder molding press of the present invention.

FIG. 2 is a control block diagram of the powder molding press of FIG.

3A and 3B schematically show a procedure for correcting the pressurization stop position of the apparatus shown in FIG. 1. FIG. 3A is a sectional view before pressurization, and FIG. 6C is a sectional view at the time of correction, FIG. 7C is a sectional view at the time of correction pressurization, and FIG. 7D is a view for explaining another correction amount setting method.

FIG. 4 is a sectional view showing the basic structure of a powder molding press according to a second embodiment of the present invention.

5 (a) and 5 (b) are cross-sectional views of essential parts when an adjusting mechanism is provided in the press of FIG.

FIG. 6 is a sectional view showing the basic structure of a powder molding press according to a third embodiment of the present invention.

FIG. 7 is a control block diagram of the powder molding press of FIG.

FIG. 8 is a block diagram showing another control configuration of the powder molding press.

[Explanation of symbols]

 1 Powder Molding Press 2 Press Main Body 21 Upper Frame 22 Lower Frame 23 Pillar 24 Pedestal 24 Tool Set 31 Die Plate 32 Upper Punch Plate 33 Lower Punch Plate 4 Upper Punch 5 Lower Punch 6 Upper Drive Mechanism 61 Bearing 62 Upper Nut 63 Upper Screw shaft 64 Encoder 65 Servo motor 66 Power transmission means 67 Holding plate 7 Lower drive mechanism 8 Mold body 9 Hole 10 Position sensor 11 Powder 100 Positioning control system 101 Control command system 102 Servo controller 103 Servo amplifier 104 Signal processing comparator 105 Drive transmission System 110 Correction control system

Claims (1)

[Claims] 1. A powder is driven by a pressure driving mechanism to drive a mold.
Pressurization stop position before the end pressurization stop position
Pressurize with a pressure sensor and detect the pressure stop position in front of the mold by a position sensor provided near the mold to calculate the insufficient position arrival amount for the target pressure stop position. Then, the method for correcting the pressurizing position in the powder molding press, characterized in that the pressurizing drive mechanism is driven to correct and pressurize based on the calculated insufficient position arrival amount.