JPH04147798A - Method and device for removing crack of molding in powder molding press - Google Patents

Abstract

PURPOSE:To prevent the cracking of a molding by previously determining the difference in compression strain quantity between respective lower punches in a pressuring stroke and vertically moving the respective lower punches according to the difference in the strain quantity, thereby maintaining the specified relative positions. CONSTITUTION:The molding W is made into a circular columnar shape stacked with disks. The differences between the respective heights of a 1st step part W1, 2nd step part W2, and 3rd step part W3 are designated as h. The packing depths of the powder to be compressed are respectively set at 6h, 4h, 2h. The upper punch 4 is lowered by 3h, the 1st lower punch 11 is lowered by 2h and the 2nd lower punch 12 is lowered by 1h in the state of fixing the 3rd lower punch 13 from the point of the time when the upper punch 4 is lowered to arrive at the front surface 1A of the die. The molding W is extruded from the die 1 upon completion of pressurization. The differences between the strain quantities delta1, delta2, delta3 are previously determined and the respective lower punches 11, 12, 13 are vertically moved according to the differences in the strains, by which the specific relative positions of the respective lower punches 11, 12, 13 are maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a powder molding press, and more particularly to a method and apparatus for removing a crank during ejection of a molded product.

(Prior Art) As a conventional powder molding press, there is one shown in FIG. 17, for example. That is, an upper punch 100 and a plurality of lower punches 101, 102, 10 arranged concentrically.
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, the occurrence of cracks 108 at the boundaries between the stepped portions 106 and 107 was a major problem.

There are various possible reasons for this, but when the molded product 105 is pulled out after pressing, each of the lower punches 101, 102, 1
The strain amount of 03 is released, and this strain amount is applied to each lower punch 101,
The difference between 102 and 103 was a major factor. That is, compressive strain occurs in each of the lower punches 101, 102, 103 due to the molding pressure during pressurization. This amount of distortion is proportional to the length of the lower punches 101, 102, 103, so as shown in FIG.
The amount of distortion a in No. 3 is the largest, and the following is the amount of distortion a in No. 3. 1st lower punch 1
The amount of distortion a N* a l becomes smaller in the order of 02 and 101. Then, when the upper punch 100 is lifted when extracting the molded product 105, the pressure on the molded product 105 is released, and each of the lower punches 101, 102, and 103 is strained by an amount aI+a! i
It grows by 83 minutes. This amount of elongation is the third lower punch 1
03 is large, the molded product 105 is cut into the third lower punch 10.
3, it will be partially pressed and extruded, and a crack will occur at the boundary with the second lower bunch 102.

Therefore, conventionally, in order to equalize the amount of distortion of each lower punch 101, 102° 103, each lower punch 101, 102.
Holder parts 101A, 102A, 103A that support 03
The relative positioning of each lower bunch 101, 102° 103 at the time of extraction was performed by changing the rigidity of the lower bunches 101, 102 and 103 by making the parts with less strain weaker and the parts with more strain stronger. However, each time, each lower punch 101, 102, 103 and each lower punch holder part 101A, 102A.

It is necessary to disassemble 103A and process it, and there are limits to its adjustment, which is the most difficult part.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to eliminate cracks in a powder forming press by absorbing the difference in the amount of strain caused by pressurization of each lower bunch at the time of extraction. An object of the present invention is to provide a method and device for removing cracks from molded products.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses an upper punch and a plurality of lower punches assembled concentrically to move the powder in the mold upward and downward. In a method for removing the crank of a molded product in a powder molding press, in which a molded product is molded by applying pressure, and then the upper punch is released from the molded product to extract the molded product from the mold, the amount of compressive strain of each lower punch during the pressurization process is The difference in the amount of strain is determined in advance, and when the pressure applied to the molded product is released after the pressurization is completed, each lower punch is moved up and down according to the difference in the amount of strain determined above. It is characterized by keeping the relative position of each lower punch end face that contacts the molded product constant.

Furthermore, it is effective to modify the amount of vertical movement of the lower punch depending on the amount of distortion that occurs in the lower punch due to frictional resistance during extraction of the molded product.

On the other hand, the molded product extraction control device for a powder molding press of the present invention includes: a hydraulic cylinder for driving each of the lower bunches; a storage means for inputting in advance a difference in compressive strain amount of each of the lower punches; and drive control means for controlling the drive of each of the hydraulic cylinders when the pressurizing force applied to the molded product is released after completion of pressurization, using the difference in the amount of compressive strain as a control target value. do.

(Function) The method for removing the crank of the molded product in the powder forming press configured as above is to move each lower punch up and down when releasing the pressing force according to the difference in the amount of distortion of each lower punch. Prevents cranking of the molded product by keeping the position constant.

Moreover, in the molded product crack removal device of the present invention,
A hydraulic cylinder is controlled by a drive control means so as to eliminate the difference in the amount of strain between each lower punch (Embodiment) The present invention will be described below based on an illustrated embodiment. First, a case will be described taking as an example a case in which a molded product W which is narrowed in two stages as shown in FIG. 1(e) is molded.

The molded product W is a cylindrical product in which large, medium, and small disks are stacked coaxially, and from the large diameter side to the small diameter side, the first... Second. It has third step portions W, , W, , W,.

The molding is carried out by compressing the powder 3 filled in the die 1 as a mold using an upper punch 4 and a lower bunch 10, as shown in FIGS. 1(a) to (C). In this embodiment, the die 1 is also moved downward as the upper punch 4 is moved downward. The lower punch 10 is fitted with the first punch concentrically. Second. It is divided into third lower punches 11, 12, and 13. The first lower punch 11 is located at the outermost position, and the upper punch 4
The first stage portion W of the molded product W is compression-molded between the molded product W and the molded product W.

The second lower punch 12 is located in the middle, and compression molds the second step W of the molded product W between it and the upper bunch 4.

The third lower punch 13 is located at the center, and compresses and forms the third step W with the upper bunch 4.

In the case of powder molding, the compression amount is about 2 times the vertical dimension, so to simplify the explanation, the dimensional relationship of the molded product W is shown from the first step WI to the third step WI. Step W
If the total height up to 3 is 3h, the height from the second step W2 to the third step W3 is 2h, and the height of the third step W is h, then the filling depth of the powder to be compressed is As shown in FIG. 1(a), the die top surface IA is based on the third punch 13.
The depth to the first lower bunch 11 is set to 6h, the depth to the first lower bunch 11 is set to 2h, and the depth to the second lower bunch 12 is set to 2h. From the point when the upper punch 4 is lowered and reaches the die upper surface IA, or from the point when it enters the die 1 a little and pressurization starts, the upper punch 4 is lowered by 3h with the third lower punch 13 fixed, and The first lower punch 11 is lowered by 2h, and the second lower punch 12 is lowered by Ih. 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 this embodiment, the upper punch 4 and the first . The speed ratio of the second lower punch 11.12 is determined by changing the speed ratio of the second lower punch 11.
, Wx, and Ws are set to the same ratio of compression amounts.

When the pressurization is completed (see FIG. 1(C)), the upper bunch 4 is raised, the die 1 is lowered, and the first. Second. The molded product W is extruded from the die l by the third lower punches 11, 12, and 13.

Then, when pressurizing, each first. Second. Third lower punch 11.1
2.13 Distortion amount δ1. δ8. The difference in δ is determined in advance, and each lower punch is adjusted according to the difference in the amount of distortion.
3 of the molded product W by moving it up and down. Second. 3rd step W
, , W, , each lower punch 11, 12.13 in contact with W,
The relative position of the end faces of the is kept constant. In this illustrated example, the third lower punch 13 is fixed, and the first... 2nd lower punch 11°1
2 is moved up and down. That is, 1st. The respective distortion amounts of the second and third lower punches 11, 12, and 13 are set to δ1. δ2
．． δ, and δ, 〈δ, 〈δ, then the second lower bunch 1
2 is moved upward by the difference in strain amount (δ, -δt) with the third lower punch I3, and the first lower bunch 11 is moved up by the difference in strain amount (δ, -δI) with the third lower punch 13. Raise, upper bunch 4
When the pressure is released, the first Second. Third punch 11,1
2. All 13 are the third lower punch 13 from the pressurization completion position
is moved upward by the same amount as the distortion amount δ3. therefore,
Each 1st. Second. While keeping the relative position of the third lower punch 11, 12.13 constant, each step W+, Wt of each molded product W,
Ws is pushed up, and each step W,,W,.

There is no risk of cracks forming between W.

Figures 2 (C) show a pressurizing method according to another embodiment of the present invention, and this example is a case of a double-sided system in which the die 1 is fixed.The molded product W' is as described above. Unlike the embodiment, the first and second lower punches 11' are two-stage cylindrical molded products having only a first step W-' and a second step W2'.

12' and the upper bunch 4 are compression molded.

Then, the amount of strain δ between the first lower punch 11 and the second lower bunch 12
, ' and δ,' (δ8-δl) is determined in advance, and when the pressure applied to the molded product W is released after the pressurization is completed, the first lower punch 11 is pressed 6. -61 up for each 1st. The relative positional relationship between the end faces of the second lower punch 11 and 12 is kept constant.

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

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

The lower punch 10 includes a first lower punch 11, a second lower punch 12, and a third lower punch, which are fitted concentrically around the core rod 6.
It is composed of a lower punch 13, and a first lower punch 11.
is a movable first punch via the first punch adapter 21.
It is fixed to the plate 31. On the other hand, the second lower bunch 1
2 is fixed to a movable second punch plate 32 via a second punch adapter 22.

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

The rod 8 connecting the die plate 30 and the pull-down yoke 34 is connected to the first rod 8. 2nd punch plate 31.32
and is inserted through the fixed plate 33 via the bushing 9, so that the respective plates 31, 32 and 33 can reciprocate relatively in parallel to each other. 1st. The second punch 11.12 is the first punch. The second hydraulic cylinder 40.50 operates the first hydraulic cylinder. 2nd hydraulic cylinder 40.5
0 are arranged in series, the first . The second punch plate 31.32 has the first punch plate. It is operatively connected coaxially with the second lower bunch 11 and 12.

The first hydraulic cylinder 40 is arranged between the first punch plate 31 and the second punch plate 320, the second hydraulic cylinder 50 is arranged between the fixed plate 33 and the second punch plate 32, and each hydraulic cylinder 40.50 is arranged between the fixed plate 33 and the second punch plate 32. Pillar 60.60
are connected via.

1st. The second hydraulic cylinder 40.50 has a donut shape with a through hole 44.54 along the central axis, and is inserted into the second punch plate 32 at the rear stage through the through hole 44 of the first hydraulic cylinder 40 at the front stage near the die I. A bunch 12 is fixed. In this embodiment, the second punch adapter 22 is inserted into the through hole 44 in a fluid-tight manner so that it can freely reciprocate.

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 fixed plate 33 via the third punch adapter 23, but the third punch adapter 23 is inserted into the through hole 54 of the second hydraulic cylinder 50 in a fluid-tight manner so as to be able to reciprocate. At the same time, it is also slidably inserted into the through hole 221 of the second punch adapter 22. Furthermore, there are also through holes 23 inside the third punch adapter 23.
1 is provided, and a core rod 6 and a core rod holder 6A are inserted into this through hole 231.

Figures 11 to 13 show each forming process in the press shown in Figure 1, and Figure 11 shows the filling process.
The upper ram 5 is raised and the upper bunch 4 is above the gouging hole 2, and the die plate 30 is pulled down by the yoke 34 and the lower ram 3.
5 in the filling position. Furthermore, the first lower punch 11,
The second lower bunch 12 is the first. 2nd hydraulic cylinder 40.50
is in the filling position.

FIG. 12 shows that while the upper bunch 4 is descending and pressurizing the powder, the first. The second lower punches 11 and 12 are also at the specified position, at which pressure has been completed.

FIG. 13 shows that as the upper punch 4 rises, the die plate 30 and the first... This is the extraction completion position where the second lower punches 11 and 12 have descended to extract the molded product.

That is, the upper punch 4 is driven by the upper ram 5, and is determined by a cam or hydraulic cylinder on the press body side. The die plate 30 is also driven by a lower ram 35 that drives the pull-down yoke 34, and is controlled by a cam or hydraulic cylinder on the press body side.

During pressure forming shown in FIG. 12, distortion occurs in various parts of the machine due to the forming load.
1 uses the first linear scale 701 to measure the movement between the first punch plate 31 and the fixed plate 33, and the second lower punch 1
2, since the position of the movement between the second lower punch plate 32 and the fixed plate 33 is measured by the second linear scale 702, it is automatically adjusted by the servo controller 74 to maintain a constant value even if there is distortion. The relative positions of the second punch plate 31, 32 and the fixed plate 33 at each part are controlled to be constant.

Originally, the first one in die 1. Second. 3rd lower bunch 11.12
．． If you look at the position of 13 relatively, there is no problem at all, but it is not possible due to the structure.Therefore, in the part where the sensor does not work, for example in Fig. 4, the first lower punch 11 and the first punch adapter 21
．． Second lower punch 12 and second punch adapter 22. Furthermore, it is necessary to make the amount of distortion of the third lower bunch 13 and the third punch adapter 23 approximately the same, but the lengths of the punch and the adapter are the same as those of the third lower bunch 13 and the third punch adapter 23. Second. The first lower bunch 13, 12°11 and the third. Second. Since the first punch adapter is longer in the order of 23 degrees and 22.21 degrees, the amount of distortion is also greater than that of the third punch adapter. 2nd degree first lower punch 13,
12.11.

In this embodiment, the first lower punch 11 and the first punch adapter 21. Second lower punch 12 and second punch adapter 22. The amount of distortion of the third lower punch 13 and the third punch adapter 23 is calculated, and the difference between the amounts of distortion is calculated and stored.

For example, the amount of distortion of the first lower punch 11 and the first punch adapter 21 is 0.5 [m], and the amount of distortion of the second lower punch 12 and the second punch adapter 22 is 0.8 [m].
3 and the amount of distortion of the third punch adapter 23 is 1 [kaku], the third lower punch 13 is fixed and does not move, so when releasing the pressing force, the first lower punch 11 is 1-0.5 = 0.5
[Kaku J, 2nd lower punch 12 is 1 0.8 = 0.2 [
m] Just pick it up.

Further, in this embodiment, the third lower bunch 13 is fixed, but the first lower punch 11 is fixed, the second lower punch 12 is fixed at 0.8-0.5 = 0.3 [am], and the third The lower punch 13 may be lowered by a value of 1-0.5 = 0.5 [m].

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

These operations are performed, for example, as shown in FIG. 14, by the first . 2nd linear scale 7
01,702, a computer 71, a servo controller 74, and a hydraulic servo valve 72. However, this is not limited to hydraulic servo valves, and various valves such as analog proportional control valves and digital valves are used. be able to.

The computer 71 has the first information in each process. 2nd punch play) 31.32 target position is input, the actual position is detected by the position detection means and fed back, the control target value and the detected value are compared, and the servo controller as the drive control means Hydraulic servo valve 72 via 74
to drive and control the first and second hydraulic cylinders 40 and 50.

The hydraulic servo valve 72 is supplied with hydraulic pressure from various hydraulic power sources j373.

Above 1. 2nd punch play) The target position of 31.32 is the 1st punch play. This is the position where the difference in the amount of strain between the second lower punch If, 12 and the third lower bunch 13 is added to the pressurization completion position.

Also, if you look at the state of cracks that occur in the molded product W, you can see where the amount of distortion is large, so you can adjust the amount.
The crank can be removed simply by modifying the input value of the difference in the amount of distortion, making adjustment of each part extremely easy. In this regard, in the past, each lower punch and punch adapter etc. were disassembled one by one, the punch adapters etc. were shaved and reassembled to change the rigidity, and a trial punch was made to see if a crank occurred, and if a crank occurred, each part was reassembled. The equipment had to be disassembled and readjusted, which required a huge amount of effort. According to the present invention, such adjustment work can be performed simply by changing the input setting value, and the adjustment work has been dramatically simplified.

Further, as a special example, a case will be described with reference to FIG. 3 in which the amount of the molded product W' to be extracted is large and the friction between the die 1 and the molded product W' is large. If the friction is large as described above, the force applied to the first lower punch 11 when extracting the molded product W' becomes approximately the same as when applying pressure. Therefore, the amount of distortion is set to 1. Second. Even if the third lower punch 11, 12, and 13 are the same, when the die l is lowered, the first lower punch 11
Only the second one is compressed and distorted. Third lower punch 12.1
This means that only 3 is pushed up, and there is a risk that a crack will occur as shown in FIG. 3(b).

Therefore, in this case, the first. Second. 3rd lower punch 11
, 12.13, if the ratio of each strain amount is 2:1:1, when the pressurizing force is released after the pressurization is completed, the 2nd. 3rd lower punch 1
2.13 has a gap between it and the molded product W'. and,
When the first lower punch 11 contracts during extraction, the second. The third lower punch 1213 can extract the molded product W' without pushing it up. In this way, the first lower punch 11 is moved to the second lower punch 11. It is difficult to obtain twice the amount of deflection of the third lower punch 12, 13 with a mechanical powder molding press, so a hydraulic press is preferable.

In this way, in the above case, the first lower punch 11 is
．． It is sufficient to push up by the difference from the third lower punch 12.13.

In this embodiment, the die set is driven and controlled by a donut-shaped cylinder to eliminate the influence of deflection of each lower punch and punch adapter, but as shown in FIG. The same applies to those configured to be attached to both sides of each punch plate 31', 32'. In this case as well, the first. 2nd punch play) The displacement amount of 31', 32' is changed to 1st. Measurements are made using the second linear scales 701 and 702, and similar feedback control is performed as shown in FIG.
and the first lower punch 11', and the second punch adapter 22.
' and the second lower punch 12' are input into the computer in advance, and the difference in strain between the first and second lower punches 12' is absorbed when the pressure is released after pressurization. second hydraulic cylinder 40',
50'.

Further, in each of the above embodiments, explanation has been given by taking as an example a so-called hydraulic press in which each lower punch is driven and controlled by hydraulic pressure, but the invention is not limited to a hydraulic press. For example, in the conventional mechanical press shown in FIG. The mechanical stoppers 110' and 111' receive the pressure applied to the first. Second. Third lower punch 101, 102, 103
and each punch adapter l0IA, 102A, 103A
The amount of deflection may be controlled by a hydraulic cylinder.

In the above embodiment, the difference in the total amount of strain between each lower punch 11.1213 and the punch adapter 21.22.23 is controlled, but in short, each first... Second. The control target is the total amount of strain of members that affect the tip position of the third lower bunch 11, 12° 13.

In the above embodiment, all the step portions are formed in a convex shape, but a molded product having a concave step portion as shown in FIG. 16 can also be molded in the same manner.

Further, in the above embodiment, the extraction of a molded product that is pressed by the Withtroal method was explained as an example, but the pressing method is not limited to this. -1
It goes without saying that the present invention can be applied to the various pressurizing methods described on pages 31 to 35 of No. 987, as well as the extraction of molded products pressurized by various other pressurizing methods.

(Effects of the Invention) The present invention has the configuration and operation described above, and when the pressure applied to the molded product is released after the completion of pressurization, the Since each lower bunch is moved up and down to keep the relative position of each lower punch constant, it is possible to reliably prevent the molded product from cranking during extraction.

In addition, the adjustment work for removing cracks can be done by simply changing the input setting value for the difference in the amount of distortion between each lower punch, which eliminates the huge effort of disassembling and adjusting each lower bunch, adapter part, etc. as in the past. is no longer necessary, and work efficiency can be dramatically improved.

[Brief explanation of drawings]

Figure 1 shows the pressurizing process when the method for removing cracks from a molded product in a powder molding press according to an embodiment of the present invention is applied to the Withtroal method, and Figure 1 (a) shows a cross section of the main part during filling. Figure 0)) is a cross-sectional view of the main part at the starting point of pressurization, (C) is a cross-sectional view of the main part when pressurization is completed, and (d) is a longitudinal cross-sectional view of the main part in the extracted state. Figure (e) is a longitudinal cross-sectional view showing an example of a molded product, Figure (f) is an enlarged cross-sectional view exaggerating the distortion state of each lower punch, and Figures A vertical cross-sectional view of the main part showing the pressurizing stroke applied to the push type, FIG. 2(e) is an enlarged cross-sectional view exaggerating the strain state of each lower punch, and FIGS. 3(a) to (C) are FIG. 4 is a vertical cross-sectional view of a main part showing the molded product extraction process when the invention is applied to the extraction of molded products with large friction, and FIG. Figure 5 is a cross-sectional view taken along the line V-V in Figure 4, Figure 6 is a cross-sectional view taken along the line Vl-Vl in Figure 4, and Figure 7 is a cross-sectional view taken along the line ■-■ in Figure 4.
8 is a sectional view taken along the line ■-■ in FIG. 4, FIG. 9 is a sectional view taken along the line IX-IX in FIG. 4, and FIG.
The X-ray cross-sectional views, FIGS. 11 to 13, show the pressurizing stroke of the gusset shown in FIG. 4, and FIG.
13 is a longitudinal cross-sectional view at the time of extraction, FIG. 14 is a control block diagram of each punch in FIG. 4, and FIG. 15 is a powder forming press according to another embodiment of the present invention. Fig. 16 is a longitudinal sectional view showing a concave stepped molded product, and Fig. 17 is a conventional one. FIG. 18 is an enlarged sectional view showing the occurrence of cracks due to the conventional molding method. Explanation of symbols 1...Die 2...Die hole 3...Powder 4...Upper punch 5...Upper ram
6... Core Rondo 10... Lower punch
11...First lower punch 12...Second lower punch
13...Third lower punch 35...Lower ram 31.32...First. Second punch plate 33...
Fixed plate 30...Die plate 40, 50
...First. Second hydraulic cylinder 71... Computer 74... Servo controller (drive control means) 701
, 702... 1st. 2nd linear scale (measuring means) (d) Figure (e) Figure 17 Figure 18

Claims (2)

[Claims] (1) An upper punch and a plurality of lower punches that are assembled concentrically with each other press the powder in the mold vertically to form a molded product, and then the upper punch is separated from the molded product and the powder is placed inside the mold. In the method for removing cracks from molded products in powder molding presses, in which molded products are extracted from When the pressure is released, each lower punch is moved up and down according to the difference in the amount of strain determined in advance to maintain a constant relative position of the end face of each lower punch in contact with the molded product. Method for removing cracks from molded products in powder molding presses. (2) The method for removing cracks from a molded product in a powder molding press according to claim 1, wherein the amount of vertical movement of the lower punch is adjusted in accordance with the amount of strain generated in the lower punch due to frictional resistance during extraction of the molded product. (3) The upper punch and a plurality of lower punches that are assembled concentrically with each other press the powder in the mold vertically to form a molded product, and then the upper punch is separated from the molded product and the powder is placed inside the mold. A crack removal device for a molded product in a powder molding press that extracts a molded product from a powder molding press includes: a hydraulic cylinder for driving each of the lower punches; and a storage means for previously inputting a difference in compressive strain amount of each of the lower punches. , drive control means for controlling the drive of each of the hydraulic cylinders when the pressurizing force applied to the molded product is released after completion of pressurization, using the difference in the amount of compressive strain as a control target value. Features: A device for removing cracks from molded products in powder molding presses.