JPH0647200B2 - Method and device for removing cracks of molded product in powder molding press - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a powder molding press, and more particularly to a method and apparatus for removing cracks when ejecting a molded product.

(Prior Art) As a conventional powder molding press, there is, for example, one shown in FIG. That is, the upper punch 100 and a plurality of lower punches 101, 102, 10 arranged concentrically with each other.
3, the powder in the mold 104 is pressed vertically to form a stepped molded product 105 as shown in FIG.

When molding such a stepped molded product 105, it was a big problem that a crack 108 was generated at the boundary between the stepped portions 106 and 107.

There are various possible reasons for this, but each of the lower punches 101, 102, 1 is removed when the pressure applied by the upper punch 100 is released when the molded product 105 is withdrawn after the completion of pressurization.
The strain amount of 03 is released, and the strain amount of each lower punch 101,
The big difference is that the difference between 102 and 103 is large. That is, compressive strain is generated in each of the lower punches 101, 102, and 103 due to the molding pressure during pressurization. Since this distortion amount is proportional to the length of the lower punches 101, 102, 103, as shown in FIG.
The strain amount a _{3 of 3} is the largest, and the second and first lower punches 1
The strain amounts of 02 and 101 become smaller in the order of a ₂ and a ₁ . And
When the upper punch 100 is lifted when the molded product 105 is pulled out, the pressure on the molded product 105 is released and the lower punches 10
₁ , 102 and 103 extend by the strain amounts a ₁ , a ₂ and a ₃ . Since the amount of elongation is large in the third lower punch 103, the molded product 105 is partially pressed and extruded only by the third lower punch 103, and a crack is generated at the boundary with the second lower punch 102. Will end up.

Therefore, conventionally, in order to make the strain amount of each lower punch 101, 102, 103 the same, each lower punch 101, 102, 1
03 supporting holders 1001A, 102A, 103
By changing the rigidity of A, the part with less distortion amount is weakened and the part with more distortion amount is strengthened, and each lower punch 101, 10 at the time of extraction
The relative position was 2,103. But,
It is necessary to disassemble and process the lower punches 101, 102, 103 and the holder parts 101A, 102A, 103A of the lower punches each time, and there is a limit to the adjustment, which is the most troublesome place.

The present invention has been made to solve the above-mentioned problems of the prior art, and its object is a powder molding press that absorbs a difference in strain amount due to pressurization of each lower punch at the time of extraction to remove cracks. To provide a method and an apparatus for removing cracks of a molded article in the above.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, an upper punch and a plurality of lower punches concentrically assembled to each other vertically move powder in a mold. In a method for removing cracks in a molded product in a powder molding press that presses to mold the molded product and then removes the molded product from the mold, find the difference in the amount of compressive strain between each lower punch in the pressing process. When the pressurizing force applied to the molded product is released after the completion of pressurization, each lower punch is moved up and down according to the difference in the strain amount obtained in advance, and each lower punch is brought into contact with the molded product. It is characterized in that the relative positions of the punch end faces are kept constant.

Further, it is effective to correct the vertical movement amount of the lower punch according to the amount of strain generated in the lower punch due to the frictional resistance when the molded product is taken out.

On the other hand, the molded product ejection control device of the powder molding press of the present invention is a hydraulic cylinder that drives each of the lower punches, a storage unit that inputs a difference in compression strain amount of each of the lower punches in advance, Drive control means for driving and controlling each of the hydraulic cylinders when the pressure applied to the molded product is released after completion of pressurization, with the difference in the amount of compressive strain as a control target value. To do.

(Working) The method for removing cracks in the molded product in the powder molding press having the above-described structure is such that the lower punches are moved up and down when releasing the pressing force according to the difference in the strain amount of the lower punches. Keeps the position constant and prevents cracks in the molded product.

Further, in the crack removing device for molded articles of the present invention,
The hydraulic cylinder is controlled by the drive control means so as to eliminate the difference in strain amount between the lower punches.

(Example) Below, this invention is demonstrated based on the Example shown in figure. First, a case where a molded product W that has been drawn in two stages as shown in FIG. 1 (e) is molded will be described as an example. Molded product W is large,
It is a columnar product that is made by stacking medium and small discs coaxially, and is the first, second, and third steps from the large diameter side to the small diameter side.
It has W ₁ , W ₂ and 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, as shown in FIGS. 1 (a) to (c). In this embodiment, the withdrawal method is used in which the die 1 is moved downward together with the downward movement of the upper punch 4. The lower punch 10 is divided into first, second and third lower punches 11, 12 and 13 which are concentrically fitted to each other. The first lower punch 11 is located on the outermost side, and compression-molds the first step W ₁ of the molded product W together with the upper punch 4. The second lower punch 12 is located in the middle, and the second stage W ₂ of the molded product W is compression molded with the upper punch 4. The third lower punch 13 is located at the center, and the third step W ₃ is compression-molded with the upper punch 4.

In the case of powder molding, the compression amount is generally about 1/2 of the vertical dimension. Therefore, in order to simplify the description, the dimensional relationship of the molded product W from the first step W ₁ The total height to the third step W ₃ is 3h, the height from the second step W ₂ to the third step W ₃ is 2h, and the height of the third step W ₃ is h.
Then, the filling depth of the powder to be compressed is, as shown in FIG. 1 (a), the die upper surface 1A with reference to the third punch 13.
To 6 h, the depth to the first lower punch 11 is 4 h, and the depth to the second lower punch 12 is 2 h. Then, as shown in FIG. 1 (b), the third lower punch 13 is fixed from the time when the upper punch 4 is moved down to reach the die upper surface 1A or when the pressure is started by slightly entering the die 1. In this state, the upper punch 4 is lowered by 3 h, the first lower punch 11 is lowered by 2 h, and the second lower punch 12 and 1 h are lowered. 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 speed ratios of the upper punch 4 and the first and second lower punches 11 and 12 are set to the final step portions W ₁ and W.
It is set to the same ratio as the ratio of the compression amounts of ₂ and W ₃ .

When the pressurization is completed (see FIG. 1 (c)), the upper punch 4 is raised and the die 1 is lowered to form the molded product W by the first, second, third lower punches 11, 12, and 13. Push out from die 1.

Then, at the time of pressurization, each of the first, second and third lower punches 11, 1
The difference between the strain amounts δ ₁ , δ ₂ , and δ ₃ generated in Nos. 2 and 13 is obtained in advance, and the lower punches 11, 12, 1 are selected in accordance with the strain amounts.
3 is moved up to form the first, second, and third step portions W ₁ , W of the molded product W.
The relative positions of the end faces of the lower punches 11, 12, and 13 that come into contact with ₂ and W ₃ are kept constant. In this illustrated example, the third lower punch 13 is fixed, and the third lower punch 13 is fixed.
The first and second punches 11 and 12 are moved up and down in accordance with the amount of distortion. That is, the first, second, third lower punch 1,
The strain amounts of 12 and 13 are δ ₁ , δ ₂ and δ ₃ , respectively,
When δ ₁ <δ ₂ <δ ₃ , the second lower punch 12 is moved upward by the difference in strain amount (δ ₃ −δ ₂ ) from the third lower punch 13,
The difference in the amount of strain between the first lower punch 11 and the third lower punch 13 (δ
₃₋ δ ₁ ) and when the pressure by the upper punch 4 is released, all of the first, second, and third punches 11, 12, and 13 are distorted from the pressing completion position to the third lower punch 13. Move upward by the same amount as the amount δ ₃ . Therefore, the step portions W ₁ , W ₂ , W _{3 of} each molded product W are pushed up while keeping the relative positions of the first, second, and third lower punches 11, 12, 13 constant,
There is no risk of cracks forming between the steps W ₁ , W ₂ , W ₃ .

2 (a) to 2 (c) show a pressurizing method according to another embodiment of the present invention, and this example is a case of a double pressure system 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.

Then, the strain amount δ of the first lower punch 11 and the second lower punch 12
The difference (δ ₂ −δ ₁ ) between ₁ ′ and δ ₂ ′ is calculated in advance, and when the pressure applied to the molded product W is released after the pressurization is finished, the first lower punch 11 is By moving up by δ ₂ −δ ₁ , the relative positional relationship between the end faces of the eleventh and second lower punches 11, 12 is made constant.

Next, FIG. 4 to FIG. 13 show a specific device configuration of the powder molding press of the present invention.

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

Further, the second lower punch 12 is fixed to the second punch plate 32 via the second punch adapter 22, and the third punch 1
3 is fixed to a fixing plate 33 fixed to the press body 7 via a third punch adapter 23.

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

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. Pillar 60,60
Are connected via.

The first and second hydraulic cylinders 40, 50 are doughnut-shaped having through holes 44, 54 along the central axis, and are punched through the through holes 44 of the first hydraulic cylinder 40 at the front stage close to the die 1 and the second punch at the rear stage. The second punch 12 is fixed to the plate 32. In this embodiment, the second punch adapter 22 is reciprocally inserted in 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. At the same time, it is slidably inserted into the through hole 221 of the second punch adapter 22. Furthermore, the through hole 2 is also formed inside the third punch adapter 23.
31 is provided, and the core rod 6 and the core rod holder 6A are inserted into the through hole 231.

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

FIG. 12 shows a position where the upper punch 4 descends and pressurizes the powder, while the first and second lower punches 11 and 12 also complete the pressurization at the specified positions.

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

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 pulling down yoke 34, and is controlled by a cam or a hydraulic cylinder on the press body side.

Then, at the time of pressure forming shown in FIG. 12, distortion occurs in each part of the machine due to the forming load.
1 is a first linear scale 701 for the movement between the first punch plate 31 and the fixed plate 33, and a second lower punch 1
2 measures the position of the movement between the second lower punch plate 32 and the fixed plate 33 with the second linear scale 702, so that the servo controller 74 automatically adjusts the value so that it is a constant value even if there is distortion. The relative positions of the first and second punch plates 31, 32 and the fixed plate 33 are controlled to be constant.

Also, as a matter of course, in order to accurately control the positions of the first, second, and third lower punches 11, 12, and 13, it is necessary to accurately position the die plate 30 and the upper punch 4 as well. is there. For that purpose, the actual positions of the upper punch 4 and the die plate 30 are detected using a linear scale or the like as in the case of the first and second punch plates 31 and 32, and the upper ram 55 and the lower punch 55 are moved using a servo controller or the like. Feedback control may be performed on the hydraulic cylinder that drives the ram 35.

Originally, the first, second and third lower punches 11, 1 in the die 1
There is no problem if the positions of 2 and 13 are relatively seen, but this is not possible due to the structure. Therefore, a portion where the sensor does not work, for example, in FIG. 4, the first lower punch 11 and the eleventh punch adapter 21, the second lower punch 12 and the second punch adapter 22, and the third lower punch 13 and the third punch adapter 23 are shown. However, the lengths of the punch and the adapter are the same as those of the third, second and first lower punches 13, 12, 11
And the third, second and first punch adapters 23, 22, 2
Since it is long in the order of 1, the strain amount is also 3rd, 2nd, 1st lower punch 1
It becomes smaller in the order of 3, 12, and 11.

In this embodiment, the first lower punch 11 and the first punch adapter 21, the second lower punch 12 and the second punch adapter 2, and the third punch
The strain amounts of the lower punch 13 and the third punch adapter 23 are calculated, and the difference between the strain amounts is calculated and stored.

For example, the distortion amount of the first lower punch 11 and the first punch adapter 221 is 0.5 [mm], the distortion amount of the second lower punch 12 and the second punch adapter 22 is 0.8 [mm], and the third lower punch 1
If the distortion amount of 3 and the third punch adapter 23 is set to 1 [mm], the third lower punch 13 is fixed and does not move. Therefore, when the pressing force is released, the first lower punch 11 has 1-0.5 = 0.5 [ mm],
The second lower punch 12 may be lifted by 1-0.8 = 0.2 [mm].

Further, although the third lower punch 13 is fixed in this embodiment, the first lower punch 11 is fixed and the second lower punch 12 is fixed.
0.8-0.5 = 0.3 [mm], the third lower punch 13 is 1-0.5 = 0.
It may be lowered by a value of 5 [mm].

In this case, the third lower punch 13 is also driven by a hydraulic cylinder or the like provided separately.

These operations are performed, for example, as shown in FIG. 14, by the first and second linear scales 7 as the position measuring means.
01, 702, the computer 71, the servo controller 74, and the hydraulic servo valve 72. However, it is not limited to the hydraulic servo valve, and various valves such as an analog proportional control valve and a digital valve can be used.

The target positions of the first and second punch plates 31, 32 in each process are input to the computer 71, and the actual positions are detected by the position detecting means and fed back to compare the control target value with the detected value. The hydraulic servo valve 7 via a servo controller 74 as a drive control means.
2 is operated to drive and control the first and second hydraulic cylinders 40 and 50. Hydraulic pressure is supplied to the hydraulic servo valve 72 from various hydraulic pressure source circuits 73.

The target positions of the first and second punch plates 31 and 32 are the first and second lower punches 11 and 12 and the third lower punch 13, respectively.
It is the position where the difference in the amount of strain between and is added to the pressurization completion position.

Further, by observing the state of the cracks generated in the molded product W, it is possible to know where the amount of strain is large, so that the amount may be adjusted. In this way, each lower punch 11, 12, 13
The cracks can be removed only by correcting the input value of the difference in the strain amount of, and the adjustment of each part can be performed very easily. In this regard, in the past, each lower punch, punch adapter, etc. were disassembled one by one, the punch adapter, etc. were shaved and assembled to change the rigidity, and a trial punch was performed to check if cracks occurred. Had to be disassembled and readjusted, which required enormous effort. According to the present invention, such an adjustment work only requires changing the input set value, and the adjustment work is dramatically simplified.

As a special example, FIG. 3 illustrates a case where the amount of the molded product W'extracted is large and the friction between the die 1 and the molded product W'is large. When the friction is large as described above, the force applied to the first lower punch 11 when the molded product W ′ is ejected is about the same as when pressing. Therefore, even if the strain amounts are the same for the first, second, and third lower punches 11, 12, 13, when the die 1 lowers, the first lower punch 11
Only the first and second lower punches 12 and 1 are distorted due to compression.
Since it is pushed up only by 3, the clutch may be generated as shown in FIG. 3 (b).

Therefore, in this case, the first, second, and third lower punches 1
If the ratio of the strain amounts of 1, 12, 13 is 2: 1: 1,
When the pressing force is released after the pressurization is completed, a gap is formed between the second and third lower punches 12 and 13 and the molded product W '. Then, when the first lower punch 11 contracts during extraction, the second and third lower punches 12 and 13 can be extracted without pushing up the molded product W '. Thus, it is difficult for the mechanical powder molding press to make the first lower punch 11 twice as much as the second and third lower punches 12, 13, and the hydraulic type is preferable. .

Thus, in the above case, the first lower punch 11 may be pushed up by the difference between the first lower punch 11 and the second and third lower punches 12, 13.

In this embodiment, the die set is driven and controlled by a donut-shaped cylinder to eliminate the influence of the deflection of the lower punches and the punch adapter. However, as shown in FIG. 15, the hydraulic cylinders 40 ', 50' are provided. Can be similarly applied to a structure in which the punch plates are attached to both sides of each punch plate 31 ', 32'. Also in this case, the displacement amounts of the first and second punch plates 31 'and 32' are measured by the first and second linear scales 701 and 702, and the same feedback control is performed as shown in FIG. That is,
First punch adapter 2 on first punch plate 31 '
The difference in strain amount between 1'and the first lower punch 11 'and between the second punch adapter 22' and the second lower punch 12 'is input to the computer in advance, and the strain is generated when the pressure is released after pressurization. The first and second hydraulic cylinders 4 so as to absorb the difference in quantity.
0'and 50 'are driven and controlled.

Further, in each of the above-described embodiments, the so-called hydraulic press in which each lower punch is driven and controlled by hydraulic pressure has been described as an example, but the present invention is not limited to the hydraulic press, and for example, in the conventional mechanical press shown in FIG. 17, each punch plate is used. The mechanical stoppers 110 ', 111' receive the pressure applied to the first, second, third lower punches 101, 102, 10
3 and each punch adapter 101A, 102A, 103
The deflection amount of A may be controlled by a hydraulic cylinder.

In the above embodiment, the difference between the total strain amounts of the lower punches 11, 12, 13 and the punch adapters 21, 22, 23 is set as the control target, but in short, the first, the second, and the second in the die hole 2, respectively.
The sum of the strain amounts of the members that affect the tip positions of the third lower punches 11, 12, and 13 is the control target.

In addition, in the above-mentioned embodiment, the steps are all formed in a convex shape, but a molded product having a concave step as shown in FIG. 16 can be similarly formed.

Further, in the above embodiment, the extraction of the molded product pressed by the withdrawal method has been described as an example, but the pressing method is not limited to this, and for example, "Powder Metallurgical Press Term" JPMA4 of the Japan Powder Industry Association Standard. -198
It is needless to say that the present invention can be applied to extraction of a molded product that has been pressed by various pressing methods described on pages 31 to 35 of No. 7, and various pressing methods.

(Effects of the Invention) The present invention has the above-described structure and action, and when the pressure applied to the molded product is released after the completion of pressurization, the difference in the strain amount of the lower punches obtained in advance is obtained. Accordingly, since the lower punches are moved up and down to keep the relative positions of the lower punches constant, it is possible to reliably prevent the cracking of the molded product at the time of extraction.

Since the adjustment work for removing cracks only needs to change the input set value of the difference in the amount of distortion of each lower punch, a huge amount of labor is required to disassemble and adjust each lower punch and the adapter section as in the conventional case. Is unnecessary, and workability can be dramatically improved.

[Brief description of drawings]

FIG. 1 shows a pressurization process when a method for removing cracks in a molded product in a powder molding press according to an embodiment of the present invention is applied to a withdrawal method, and FIG. 1 (a) is a sectional view of a main part at the time of filling. Figure, Figure (b) is a cross-sectional view of the main part at the start point of pressurization, (c) is a cross-sectional view of the main part at the completion of pressurization, (d) is a vertical cross-sectional view of the main part in the extracted state Figure (e) is a vertical cross-sectional view showing an example of a molded product, (f) is an enlarged cross-sectional view showing the distorted state of each lower punch exaggeratedly, and (a) to (d) of Fig. 2 show the present invention. FIG. 2 (e) is an enlarged sectional view showing exaggeratedly a distorted state of each lower punch, FIG.
(a) to (c) are longitudinal cross-sectional views of a main part showing a process of extracting a molded product when the present invention is applied to the extraction of a molded product having a large friction, and FIG. 4 is a powder whose pressure is controlled as shown in FIG. FIG. 5 is a vertical sectional view showing a tool set of a molding press, FIG. 5 is a sectional view taken along line VV of FIG. 4, and FIG. 6 is a sectional view taken along line VI-VI of FIG.
7 is a sectional view taken along the line VII-VII of FIG. 4, and FIG. 8 is a sectional view of FIG.
VIII-VIII sectional view, FIG. 9 is a sectional view taken along line IX-IX of FIG. 4, FIG. 10 is a sectional view taken along line XX of FIG. 4, and FIGS. 11 to 13 are dies of FIG. The pressurizing process of the set is shown in FIG. 11, at the time of filling, in FIG.
FIG. 14 is a vertical sectional view at the time of extraction, FIG. 14 is a control block diagram of each punch of FIG. 4, and FIG. 15 shows a tool set of a powder molding press according to another embodiment of the present invention. ) Is a vertical cross-sectional view, FIG. 16B is a horizontal cross-sectional view of the fixed plate portion, FIG. 16 is a vertical cross-sectional view showing a concave stepped molded product, FIG. 17 is a vertical cross-sectional view of a conventional powder molding press, FIG. 18 is an enlarged cross-sectional view showing a crack generation state by the conventional molding method. Explanation of symbols 1 ... die, 2 ... die hole 3 ... powder, 4 ... upper punch 5 ... upper ram, 6 ... core rod 10 ... lower punch, 11 ... first lower punch 12 ... first 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 71 …… Computer 74 …… Servo controller (drive control means) 701,702 …… First and second linear scales (measuring means)

Claims (3)

[Claims] 1. A powder which presses powder in a mold up and down by an upper punch and a plurality of lower punches which are concentrically assembled with each other to form a molded product, and the molded product is withdrawn from the mold. In the molding press, the difference in the compression strain amount of each lower punch in the pressurization process was calculated in advance, and when the pressurizing force applied to the molded product was released after the pressurization, the above-mentioned prediction was calculated. A method for removing cracks in a molded product in a powder molding press, characterized in that each lower punch is moved up and down in accordance with a difference in strain amount to keep the relative position of each lower punch end face abutting the molded product constant. 2. The method for removing cracks in a molded product in a powder molding press according to claim 1, wherein the vertical movement amount of the lower punch is corrected according to the amount of strain generated in the lower punch due to frictional resistance when the molded product is pulled out. 3. A powder which presses powder in a mold up and down by an upper punch and a plurality of lower punches which are concentrically assembled to each other to mold a molded product, and which removes the molded product from the mold. In the forming press, a hydraulic cylinder that drives each of the lower punches, a storage unit that predictively inputs a difference in compressive strain amount between the lower punches, and a difference between the compressive strain amounts as a control target value are added. A device for removing cracks in a molded product in a powder molding press, comprising: drive control means for driving and controlling each of the hydraulic cylinders when the pressure applied to the molded product is released after completion of the pressure.