JPH07106473B2 - Method and apparatus for controlling pressure of powder molding press - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a powder molding method, and more particularly to a method and apparatus for controlling the pressure of a powder molding press to obtain a stepped molded product.

(Prior Art) A conventional stepped molded article of this type is pressure-molded as shown in FIG. 16, for example. That is, at the filling position where the raw material powder 101 is filled in the mold 100, the mold 10
The 0, first, and second lower punches 104, 105 are in a state of being lifted by the air cylinder (see FIG. 11A). Next,
By the pressing force of the upper punch 102, the first through the powder 101
A force is applied to the second lower punches 104 and 105 to lower them, and the second lower punches 104 and 105 come into contact with a stopper (not shown) to complete the pressurization. Then, the compression force of each step 111 is adjusted by setting the air pressure of the air cylinder to an appropriate value during the pressurizing stroke.

(Problems to be Solved by the Invention) However, in the case of the above-described conventional technique, the upper punch 102 is moved from the state shown in FIGS.
Pressurization of the powder is started by the
The density of the first step portion 111 between the lower punch 104 and the upper punch 102 increases, and at the same time, the powder of the first step portion 111 becomes the second lower punch 1
It drops on the second step 112 between 05 and the upper punch 102. Upper punch
When the pressing force of 102 exceeds the filling force of the first lower punch 104,
As shown in FIG. 3D, the upper punch 102 and the first lower punch 104.
Simultaneously descends. Further, as shown in (e) of the figure, the upper punch 102 and the first and second lower punches 104, 105 hit the stoppers to complete the pressurization, but before that, the powder in the second step portion 112 becomes the third. It falls on the third step portion 113 between the punch 106 and the upper punch 102.

As described above, conventionally, as the pressurization proceeds, the powder is solidified while moving from the first step portion 111 to the second step portion 112 and further to the third step portion 113, so that the first step portion 111 and the second step portion 112 are solidified. Cracks at the corners of the corners and at the corners of the second step 112 and the third step 113
4 may occur.

Also, unlike the calculated filling depth, it is necessary to adjust the amount of pressurization, so time and molding technology were required to obtain a good product.

The present invention has been made to solve the above-mentioned problems of the conventional art, and its object is to provide a powder molding method capable of uniformly pressing each step of a stepped molded article,
Therefore, it is intended to prevent the occurrence of cracks in the molded product and to facilitate the setting by eliminating the adjustment of the filling depth and the air pressure of the air cylinder.

(Means for Solving the Problem) In order to achieve the above object, in the present invention, at least a lower punch of the upper and lower punches for pressurizing the powder filled in the die holes of the mold from above and below is used. When dividing into a plurality of lower split punches and filling the powder into the die hole, the ratio of the powder filling depth from the upper surface of the die to the lower split punches is determined by each of the stepped molded products to be molded. A powder molding press that sets substantially the same ratio as the height dimension of the stepped portion and simultaneously compresses the plurality of powder portions by an upper punch and a plurality of lower split punches to form each stepped portion of a stepped molded product. This is a pressure control method, and the ratio of the compression speed, which is the rate of change of the amount of compression of each powder portion with respect to time, during the entire pressing process from the start of pressing the powder to the completion of pressing is the final molded product. So that the ratio is approximately the same as the height dimension of each step of By controlling the moving speeds of the upper punch and the lower split punches, a plurality of powder portions sandwiched between the upper punch and the lower split punches are constantly maintained at the same degree of compression during the entire pressing process. To do.

Also, a mold having a die hole having a large-diameter hole portion opening upward, a small-diameter hole portion opening downward, and a step portion at the boundary between the large-diameter hole portion and the small-diameter hole portion, and a large-diameter An upper punch inserted into the hole portion and a lower punch inserted into the small diameter hole portion are provided, and when filling powder into the die hole, a filling depth from the upper surface of the die to a step portion of the die hole and The ratio of the filling depth from the upper surface of the die to the lower punch is set to the same ratio as the ratio of the height dimension of each step of the stepped molded product to be formed, and the powder filled in the die hole is Of which, the powder portion sandwiched between the upper punch and the step portion on the inner periphery of the die hole is compressed by the upper punch and the step portion, and the powder portion sandwiched by the upper punch and the lower punch is compressed by the upper punch and the lower punch. A method for controlling the pressure of a powder molding press, which molds each step of a stepped molded product, comprising: During the entire pressurization process from the start of pressurization to the completion of pressurization, the upper punch and the lower punch are sandwiched between the upper punch and the lower punch. The mold, so that the ratio of the amount of compression of the powder portion to the compression speed, which is the rate of change over time, is the same as the ratio of the height dimension of each step of the final molded product,
By controlling the moving speed of the upper punch and the lower punch, the powder part sandwiched between the step part of the upper punch and the die hole and the powder part sandwiched between the upper punch and the lower punch are controlled during the entire pressing process. It is characterized by maintaining the same degree of compression.

Further, the pressure control device of the powder molding press of the present invention includes a die having a die hole filled with powder, an upper punch for pressurizing the powder in the die hole from above, and an inside die hole. Lower punch for pressing the powder from below from below, an upper ram for driving the upper punch, a lower ram for driving the die, and a fluid pressure cylinder for driving the lower split punch. A position detecting means for detecting the position of the lower split punch, a pressure source for supplying a pressure fluid to the fluid pressure cylinder, and a flow rate of the pressure fluid supplied from the pressure source to control the movement of the lower split punch. A flow rate control valve for controlling the speed and a control target speed of each lower split punch during the pressurizing process, and a step difference of the control target speed and the lowering speed of the upper punch, each step portion of the stepped molded product to be formed. The height dimension ratio of the The position control means sequentially detects the position of each of the lower split punches to calculate the actual speed of the lower split punches, and eliminates the deviation from the set control target speed. And a control means for controlling the descending speed of each lower split punch by issuing a correction signal to the.

(Operation) According to the pressure control method of the powder molding press having the above-described configuration, at least the lower punch is divided into a plurality of pieces, or a step portion is provided in the die hole, so that the powder filled in the die hole is
A plurality of powder portions are compressed in the axial direction at a predetermined speed, and the ratio of the compression speed, which is the rate of change of the compression amount of each powder portion with respect to time, during the compression process from the start of compression to the completion is always Since the height dimension ratio of each step portion of the stepped molded product to be molded is controlled to be the same ratio, the compressibility of the powder is maintained uniform at any stage of the pressurizing process,
There is no powder transfer between each powder part.

Further, according to the pressure control device of the powder molding press of the present invention, the moving speed of each lower split punch during the pressing process is always controlled to the predetermined control target speed by the position detection means and the control means. . Therefore, the powder portion sandwiched by the upper punch and the lower split punches is always compressed at the same ratio as the height dimension ratio of each step portion of the stepped molded product to be molded.

(Example) Below, this invention is demonstrated based on the Example shown in figure. First, a molded product W drawn in two stages as shown in FIG. 1 (e).
The case of molding will be described as an example. Molded product W is large,
It is a columnar product that coaxially stacks medium and small discs. From the large diameter side to the small diameter side, the 1st, 2nd, 3rd step W ₁ , W ₂ ,
Has W ₃ .

The molding is performed by compressing the powder 3 filled in the die 1 as a mold by the upper punch 4 and the lower punch 10. In this embodiment, the die 1 is moved together with the lower movement of the upper punch 4. It is carried out by a downward withdrawal method. The lower punch 10 is the first, second, and third lower punches 11, 12, 13 as lower split punches that are concentrically fitted.
It is divided into two parts. The first lower punch 11 is located on the outermost side, and the powder portion is axially compressed between itself and the upper punch 4 to form the first step portion W1 of the formed product W. The second lower punch 12 is located in the middle, and the powder portion is axially compressed between itself and the upper punch 4 to form the second step W2 of the formed product W. 3rd lower punch
13 is located at the center, and the powder portion between the upper punch 4 and the upper punch 4 is axially compressed to form the third step W3.

In the case of powder molding, the compression amount is generally compressed by about 1/2 in the vertical dimension. Therefore, in order to simplify the description, the dimensional relationship of the molded product W is set to the height of the third step W3. Size 3
Assuming that the height of the second step W2 is 2h and the height of the first step W1 is h, the filling depth of the powder to be compressed is as shown in Fig. 1 (a). The depth to the die upper surface 1A is set to 6h based on 3 punches 13, and the depth to the first lower punch 11 is set.
4h, and the depth to the second lower punch 12 is set to 2h. Based on the die upper surface 1A, the first lower punch 11
Filling depth up to 2h, filling depth up to the second lower punch 12
The filling depth up to 4 h and the third lower punch 13 is 6 h, and the ratio is the same as the ratio of the height dimension of each step W1, W2, W3 of the molded product W to 1: 2: 3. Then, as shown in FIG. 1 (b), the third lower punch 13 is fixed from the time when the upper punch 4 is lowered to reach the die upper surface 1A or when the pressure is started by slightly entering the die 1. State, lower the upper punch 4 by 3h, lower the first lower punch 11 by 2h, and lower the second punch.
Decrease by 12 and 1h. The die 1 is lowered together with the upper punch 4 from the time when the primary upper pressing by the upper punch 4 is completed.

In the case of this embodiment, the upper punch 4 and the first and second punches
The speed ratio of the lower punches 11 and 12 is set to the same ratio as the ratio of the final compression amounts of the respective step portions W ₁ , W ₂ and W ₃ . That is, the first stage W ₁ is finally compressed by 1h, the second stage W ₂ is finally compressed by 2h, and the third stage W ₃ is finally compressed by 3h. , The speed of the upper punch 4 is V _A , the speed of the first lower punch 11 is V _B , and the speed of the second lower punch 12 is V _C , V _A : V _B : V _C = 3: 2: 1 Was set.

However, this speed ratio can be adjusted not only when it is completely the same, but also by a predetermined amount so as to obtain an optimum pressurization state.

Here, if v is based on V _C , V _A = 3v, V _B = 2v, V _C
= V, the compression amount of each step after t [s] is the first step
W ₁ is (V _A −V _B ) × t = vt, and the second step W ₂ is (V _A −V _C ) × t
= 2vt, and the third stage portion W ₃ becomes V _A × t = 3vt. That is, v, 2v, 3v is the compression speed which is the rate of change of the amount of compression of the powder portion corresponding to each step W1, W2, W3 with respect to time,
The height ratio of each step W1, W2, W3 is the same ratio as 1: 2: 3.

Then, looking at the compression degree at this time, the first step W ₁ is vt /
(6h-4h) = vt / 2h, the second step portion W ₂ is 2vt / (6h-2h) = 2vt
/ 4h = vt / 2h, and the third stage portion W ₃ has 3vt / 6h = vt / 2h, and the degree of compression is the same. Therefore, in the entire pressurization process from the start of pressurization to the completion of pressurization, the 1st, 2nd, 3rd
Cause all stepped portion W _1, W _2, W ₃ is pressurized to a uniform density, the movement of a conventional powder due to the difference in the pressurized state of extend the draft section W _1, W _2, W ₃ as It is possible to mold a green compact having a uniform structure.

Further, since the pressure can be uniformly applied in this manner, each step W ₁ , W ₂ ,
The filling depth of W ₃ is basically a calculated value, and the setting becomes easy.

FIGS. 2 (a) to 2 (c) show a pressing method according to another embodiment of the present invention, which is a case of a double-pressing method in which the die 1 is fixed. 'The above embodiment unlike the first step portion W _1' molded product W 'only the two-stage cylindrical molded article, first, second lower punch 11' and the second step portion W _2, 12 ' And is compression-molded by the upper punch 4.

In this case, set the speed of each punch to V _A ′ for the upper punch 4,
If the first lower punch 11 ′ is V _B ′ and the second lower punch 12 ′ is V _C ′, the ratio is set to V _A ′: V _B ′: V _C ′ = 1: 0: 1, and the upper punch is also set. 4 is the top surface of die 1
The speed ratio may be controlled during the entire pressurization process in which pressurization is completed from the time when 1A is reached or a time when it is slightly entered, that is, the time when pressurization is started.

Also in this embodiment, it is assumed that the compression is 1/2, and the first step W ₁ ′
Assuming that the height of the molded product of 1 is h and the height of the second step W ₂ ′ is 2 h, the filling depth is 2 h for the first step W ₁ ′ and 4 h for the second step W ₂ ′, Assuming that the velocity is V _A ′ = V _C ′ = v, the compression degree after t [s] from the pressurization start point is vt / 2h for the first step W ₁ ′ and the second step W
₂ ′ is 2vt / 4h = vt / 2h, which means that it is always pressurized with a constant degree of compression.

FIGS. 3 (a) to 3 (c) show a pressurizing method according to still another embodiment of the present invention, showing a case where the die 1 is stepped even in the withdrawal method. Also in this embodiment, the stepped type as the molded product W ″ will be described. There is one lower punch 10 ″, and the second step W ₂ ″ is compressed between the lower punch 10 ″ and the upper punch 4. It And die 1
The first step W ₁ ″ is compressed between the step 1 </ b> B and the upper punch 4.

In this case, when the speed of the upper punch 4 is V _A ″, the speed of the die 1 is V _B ″, and the speed of the lower punch 10 ″ is V _C ″, A ″: B ″: C ″ = 2: 1: It may be set to a ratio of 0 (fixed).

Also in this embodiment, it is assumed that the compression is 1/2, and the first
The height of the step W ₁ ″ molded product is h, and the height of the second step W ₂ ″ is 2h
Then, the filling depth is 2 h for the first step W ₁ ″ and 2 h for the second step W ₂ ″.
There is 4h, the velocity _{V A "= 2v, V B} " When = v, the compression rate after t [s] from the pressurization start point, the first step portion W ₁ "is (V _A" -V _B ″) t / 2h ＝ vt / 2h, the second step W ₂ ″ is (V _A ″ −V
_C ″) t / 4h = 2vt / 4h = vt / 2h, and it is possible to pressurize uniformly with a constant degree of compression.

In each of the above embodiments, the upper surface of the molded product is a flat surface. However, the upper surface also has a stepped shape, and the upper punch may be divided and pressure-controlled as in the lower punch as shown in FIG. Good. Further, the pressure control shown in FIGS. 1 and 2 may be performed using the stepped die 1 as shown in FIG. 3, or various pressure controls may be performed.

Next, FIG. 4 to FIG. 13 show a concrete device configuration of the pressure control device of the powder molding press of the present invention. This device can be applied to any of the above pressurizing methods.
It is suitable when the molded product W shown in the figure is pressure-molded.

T indicates a tool set, which includes a die 1 having a rough die hole 2, and an upper punch 4 and a lower punch 10 for pressing the raw material powder 3 filled in the die hole 2. The upper punch 4 is attached to the upper ram 5,
The upper punch 4 is inserted into the die hole 2 and the powder 3 is pressed by the vertical movement of.

The lower punch 10 is composed of a first lower punch 11, a second lower punch 12, and a third lower punch 13, which are concentrically fitted around the core rod 6, and the first lower punch 11 is the first. It is fixed to a movable first punch plate 31 via a punch adapter 21.

Further, the second lower punch 12 is fixed to the second punch plate 32 through the second punch adapter 22, and the third punch 13 is the third punch.
It is fixed to a fixed plate 33 fixed to the press body 7 via a punch adapter 23.

Then, the rod 8 connecting the die plate 30 and the pulling down yoke 34 is inserted through the first and second punch plates 31, 32 and the fixed plate 33 via the bush 9 so that the plates 31, 32, 33 are parallel to each other. It is designed to move back and forth relatively. The first and second punches 11 and 12 are operated by the first and second hydraulic cylinders 40 and 50. The first and second hydraulic cylinders 40 and 50 are arranged in series, and the first and second punches 11 and 12 are arranged. The plates 31 and 32 are operatively connected to the first and second lower punches 11 and 12 coaxially.

The first hydraulic cylinder 40 is arranged between the first punch plate 31 and the second punch plate 32, and the second hydraulic cylinder 50 is arranged between the fixed plate 33 and the second punch plate 32. Are connected via columns 60,60.

The first and second hydraulic cylinders 40, 50 have through holes 4 along the central axis.
Donut shape with 4,54, 1st in front of die 1
The second punch 12 is fixed to the second punch plate 32 at the subsequent stage through the through hole 44 of the hydraulic cylinder 40. In this embodiment, the second punch adapter 22 is reciprocally inserted into the through hole 44 in a liquid tight state.

The first hydraulic cylinder 40 has a cylinder tube 41 and a piston 42 inserted into the cylinder tube 41, and a piston rod 43 is connected to the first punch plate 31.

The second hydraulic cylinder 50 also includes a cylinder tube 51 and a piston 52, and one end of a piston rod 53 is connected to the second punch plate 32.

On the other hand, the third punch 13 is fixed to the fixing plate 33 via the third punch adapter 23, and the third punch adapter 23 is reciprocally inserted in the through hole 54 of the second hydraulic cylinder 50 in a liquid tight state. And the through hole of the second punch adapter 22.
It is also slidably inserted in 221. Further, a through hole 231 is also provided inside the third punch adapter 23, and the core rod 6 and the core rod holder 6A are inserted into the through hole 231.

11 to 13 show each forming step in the press of FIG. 1, and FIG. 11 shows the filling step, in which the upper ram 5 rises and the upper punch 4 is located above the die hole 2. The die plate 30 is in the filling position by the pull-down yoke 34 and the lower ram 35. Further, the first lower punch 11 and the second lower punch 12
Is in the filling position by the first and second hydraulic cylinders 40,50.

FIG. 12 shows that the upper punch 4 descends and pressurizes the powder,
The first and second lower punches 11 and 12 are also positions where the pressurization is completed at the specified positions.

FIG. 13 shows the die plate 30 as the upper punch 4 moves up.
And the first and second lower punches 11 and 12 are lowered to the extraction completion position where the molded product is extracted.

For example, as shown in FIG. 15, these operations are performed by a drive control means 70 that is configured by a combination of a position detection means 71 such as a linear sensor, a computer 72, a hydraulic flow rate adjusting valve 73, and a hydraulic pressure source circuit 77. Controlled by.

That is, the upper punch 4 is driven by the upper ram 5 and is determined by the cam or hydraulic cylinder on the press body side. The die plate 30 is also driven by the lower ram 35 that drives the pull-down yoke 34, and is controlled by a cam on the press body side or a hydraulic cylinder. In this embodiment, the first and second hydraulic cylinders 4
By controlling the speed of 0 and 50, the relative speed with respect to the upper punch 4 is determined.

The position detection means 71 detects the positions of the first punch plate 31 and the second punch plate 32, respectively, and between the fixed plate 33 and the first punch plate 31, and between the fixed plate 33 and the second punch plate 32. The position of the first and second punch plates 31, 32 with respect to the fixed plate 33 is converted into an electric signal and detected.

On the other hand, the computer 72 sequentially calculates the positions and speeds of the first lower punch 11 and the second lower punch 12 from the detection signals from the position detecting means 71, 71, and the step W of the molded product W. _The memory 75 for inputting and storing the target speed of the first and second punches 11, 12 preliminarily calculated from the dimensions of ₁ ... and the filling depth of the powder to be filled, and the target speed and the calculated speed are stored. The first and second hydraulic cylinders 4 should be compared to eliminate deviations.
A comparison unit 76 that issues a correction signal to the flow control valve 73 for 0, 50;
Is equipped with.

As described above, the first and second lower punches 11 and 12 are hydraulically driven, and the speed of each of the first and second hydraulic cylinders 40 and 50 is increased by the upper punch 4.
By performing proportional control so that the ratio becomes constant with respect to the speed of, the pressurization control of the present invention can be realized with an extremely simple configuration. The speeds of the first and second hydraulic cylinders 40, 50 stored in the memory 75 are not limited to constant speeds, but are determined to have a constant ratio with respect to the speed of the upper punch 4, that is, the upper ram 5, In the case of a mechanical press using a cam, it is necessary to store it as a sinusoidal velocity pattern similar to that of the upper ram 5.

However, the present invention is not limited to the mechanical press, and is similarly applicable to a hydraulic press. In the case of a hydraulic press, the moving speeds of the upper ram 5 and the lower ram 35 are also the same.
The control may be performed in association with the moving speeds of the first and second hydraulic cylinders 40 and 50.

In addition, in the above-mentioned embodiment, all the step portions are formed in a convex shape, but a molded article having a concave step portion as shown in FIG. 14 can be similarly formed. The specific device configuration to which the present invention is applied is not limited to the one using a donut-shaped hydraulic cylinder as shown in FIGS.
As shown in FIG. 17, it can be applied to a tool set 202 in which hydraulic cylinders 200 and 201 are arranged in parallel, and a tool set having various other configurations.

Further, the present invention is not limited to hydraulic cylinders such as hydraulic cylinders and pneumatic cylinders, and various known drive mechanisms such as a ball screw or crank mechanism or a dog mechanism capable of speed control can be used.

(Effects of the Invention) The present invention has the above-described configuration and operation, and controls the speed at which each step of a stepped molded article is compressed to be the same ratio as the final compression dimension ratio of each step. Therefore, the compressibility of each step is made uniform at any point in the pressurization process, and it is possible to prevent the movement of the powder between the step parts due to the difference in the compressibility of each step as in the conventional case. The step can be evenly pressed to prevent the occurrence of cracks.

Further, since each step can be compressed uniformly, the powder filling depth can be easily set without considering the movement of the powder.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a pressurizing process and a molded product when a pressurizing control method for a powder molding press according to an embodiment of the present invention is applied to a withdrawal method, and FIGS. c) is a longitudinal sectional view of a main part showing a pressurizing stroke in which the present invention is applied to a double-press type, and FIG. 3 is an application of the present invention in a withdrawal method, showing a pressurizing stroke in a case where a die is stepped. 4 is a vertical cross-sectional view showing a tool set of the powder molding press in which pressure control of FIG. 1 is performed, FIG. 5 is a cross-sectional view taken along line VV of FIG. 4, and FIG. Fig. 4 is a sectional view taken along line VI-VI, Fig. 7 is a sectional view taken along line VII-VII of Fig. 4, Fig. 8 is a sectional view taken along line VIII-VIII of Fig. 4, and Fig. 9 is IX of Fig. 4. -IX sectional view, FIG. 10 shows a sectional view taken along line XX of FIG. 4, and FIGS. 11 to 13 show a pressing stroke of the die set shown in FIG.
FIG. 11 is a vertical sectional view at the time of filling, FIG. 12 is at the completion of pressurization, FIG. 13 is a vertical sectional view at the time of extraction, FIG. 15 is a control block diagram of each punch in FIG. 4, and FIG. Longitudinal sectional view showing the molded product,
16 (a) to 16 (e) are longitudinal sectional views of a main part showing respective steps of a conventional pressure control method for a powder molding press, and FIG. 17 is a general parallel cylinder type tool to which the present invention is applied. A set is shown, (a) is a sectional view taken along the line AA of (b), (b) is a plan view, and (c) is a plan view showing an example of the arrangement configuration of other cylinders. It is a figure. Explanation of reference numerals 1 ... Die, 2 ... Die hole 3 ... Powder, 4 ... Upper punch 5 ... Upper ram, 6 ... Core rod 10 ... Lower punch, 11 ... First lower punch 12 ... No. 2 lower punch, 13 …… third lower punch 35 …… lower ram 31,32 …… first and second punch plate 33 …… fixed plate, 30 …… die plate 40,50 …… first and second hydraulic pressure Cylinder 70 …… Drive control means, 71 …… Position detection means 73 …… Flow control valve, 74 …… Computing section 75 …… Memory

Claims (3)

[Claims] 1. At least a lower punch among upper and lower punches for pressurizing powder filled in a die hole of a die from above and below is divided into a plurality of lower divided punches, and the powder is filled in the die hole. At this time, the ratio of the powder filling depth from the die upper surface to each lower split punch is set to be substantially the same as the ratio of the height dimension of each step portion of the stepped molded product to be molded, Is a method for controlling the pressure of a powder molding press that simultaneously compresses the powder part of the powder with an upper punch and a plurality of lower split punches to mold each step of a stepped molded product. During the entire pressurizing process, the ratio of the compression speed, which is the ratio of the amount of compression of each powder part to the time, should be approximately the same as the ratio of the height dimension of each step of the final molded product. , The upper punch and each lower split punch are controlled to control the moving speed, Always upper punch and pressure control method of the powder molding press, characterized in that a plurality of powder portions sandwiched between lower divided punch to keep the same degree of compression. 2. A mold provided with a die hole having a large-diameter hole portion opening upward, a small-diameter hole portion opening downward, and a step portion at a boundary between the large-diameter hole portion and the small-diameter hole portion. An upper punch to be inserted into the large-diameter hole portion and a lower punch to be inserted into the small-diameter hole portion, and when filling the die hole with powder, a portion from the upper surface of the die to a step portion of the die hole The ratio between the filling depth and the filling depth from the upper surface of the die to the lower punch is set to the same ratio as the height dimension of each step of the stepped molded product to be formed, and the filling is performed in the die hole. Of the powder, the powder portion sandwiched between the upper punch and the step portion on the inner periphery of the die hole is compressed by the upper punch and the step portion, and the powder portion sandwiched by the upper punch and the lower punch is compressed by the upper punch and the lower punch. A pressure control method for a powder molding press, which comprises compressing and molding each step of a stepped molded article, During the entire pressurization process from the start of pressurization of powder to the completion of pressurization, the compression rate, which is the rate of change in the amount of compression of the powder part sandwiched by the step part of the upper punch and the die hole, with time, the upper punch and the lower punch. The mold, so that the ratio of the compression rate, which is the rate of change of the amount of compression of the powder part sandwiched by, with the compression rate is the same as the ratio of the height dimension of each step of the final molded product,
By controlling the moving speeds of the upper punch and the lower punch, the powder portion sandwiched between the step portions of the upper punch die hole and the powder portion sandwiched between the upper punch and the lower punch are always made to be the same during the entire pressing process. A method for controlling pressurization of a powder molding press, characterized by maintaining the degree of compression. 3. A die having a die hole filled with powder, an upper punch for pressing the powder in the die hole from above, and a plurality of lower parts for pressing the powder in the die hole from below. A lower punch divided into divided punches, an upper ram that drives the upper punch, a lower ram that drives the die, a fluid pressure cylinder that drives the lower split punch, and a position of the lower split punch is detected. Position detecting means, a pressure source for supplying pressure fluid to the fluid pressure cylinder, a flow rate control valve for controlling the flow rate of the pressure fluid supplied from the pressure source to control the moving speed of the lower split punch, The target speed of each lower split punch to be controlled during the pressure stroke,
The speed difference between the target speed and the lowering speed of the upper punch is set in advance so as to be the same as the height dimension ratio of each step portion of the stepped molded product to be molded, and the lower division is performed by the position detecting means. The position of the punch is successively detected, the actual speed of the lower split punch is calculated, and a correction signal is issued to the flow control valve so as to eliminate the deviation from the set target speed, and the lowering speed of each lower split punch. And a control means for controlling the pressure control device of the powder molding press.