JPH0716795A - Powder molding press - Google Patents

Abstract

PURPOSE:To provide the powder molding press which lessens the movement of powder as far as possible by changing the force of fluid pressure cylinders for supporting movable punches during the pressurizing stroke, prevents the generation of the crack of molded goods and makes it possible to obtain the molded goods having high accuracy. CONSTITUTION:The powder molding press in which the plural punches are partly 4, 6 supported as movable punches by the fluid pressure cylinders 17, 18 is provided with a pressure control means 19 for increasing the fluid pressures of the fluid pressure cylinders 17, 18 according to progression of pressurization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage powder molding press for molding a stepped molded product.

[0002]

2. Description of the Related Art A conventional powder molding press for molding a stepped molded product of this kind has a structure as shown in FIG. 9, for example.

That is, the lower first and lower second punches 101 and 102 and the lower third punch 10 corresponding to each step of the molded product.
3 of which, among these, the lower first punch 1 and the lower second punch 10
1, 102 are supported by the first and second fluid pressure cylinders 104 and 105 as movable punches, and the lower third punch 103
Is fixed. On the other hand, the upper punch 106 is connected to the upper ram of the press (not shown), and the die plate 107 is fixed to the lower ram (not shown) via the yoke plate 108.

The lower first and second punches 101 and 102 are movable by the first and second fluid pressure cylinders 104 and 105, but the upper limit position is regulated by the filling adjusting device 109, while the lower limit position is set. Are regulated by the stopper 110.

The first and second fluid pressure cylinders 104, 1
Reference numeral 05 denotes an air pressure cylinder, which has a circuit configuration shown in FIG. 10 and is filled with a constant air pressure in a direction of extending the cylinder through the pressure reducing valve 112. The air pressure supports the first and second punches 101 and 102. ing.

The pressing process will be described with reference to the drawings. As shown in FIGS. 9 (a) and 9 (b), when the upper punch 106 is lowered to compress the powder 111, first, the lower first Punch 1
01 The pressure of the powder on the upper part increases. Therefore, as shown by the arrow, the powder falls from the upper part of the lower first punch 101 to the upper part of the lower second punch 102, and the force applied to the lower first punch 101 causes the force of the first fluid pressure cylinder 104 supporting the lower first punch 101. When the force becomes larger than the force, the lower first punch 101
Goes down.

Next, as shown in FIG. 9 (c), the upper punch 1
When both 06 and the lower first punch 101 descend, the force applied to the lower second punch 102 increases, and as indicated by the arrow, the upper part of the lower second punch 102 to the upper part of the lower third punch 103 is slightly increased. While the powder falls on the bottom second punch 102
When it becomes larger than the force of the second fluid pressure cylinder 105 supporting the upper punch 106, the upper punch 106, the lower first and second lower punches 10,
1,102 descends.

In this pressurizing stroke, the first and second fluid pressure cylinders 104 and 105 contract, but the tank 11 in the circuit is
By 3, the increase in air pressure is suppressed to a minimum,
The air pressure is kept substantially constant regardless of the strokes of the first and second fluid pressure cylinders 104 and 105 (FIG. 10).
(See (a) and (b)).

Further, as shown in FIG. 9 (d), when the upper punch 106 is lowered, the powder density is increased, and at this time, the lower first and second punches 101 and 102 are moved to the first and second fluid pressure cylinders. When it is supported by 104 and 105,
The powder returns from the upper part of the lower third punch 103 to the lower second and first punches 102, 101 side in reverse.

When the upper punch 106 descends, as shown in FIG.
As shown in (e), the lower first and second punches 101, 102
Then, the stopper 110 hits and the pressurization ends.

Then, as shown in FIGS. 10 (c) and 10 (d),
The contraction sides of the first and second fluid pressure cylinders 104, 105 are also filled with air pressure via the pressure reducing valve 114, the air pressures on the rising side and the falling side are balanced, and the process proceeds to an extraction process (not shown).

[0012]

However, in the case of the prior art, if the first and second fluid pressure cylinders 10 are used.
When the force of 4, 105 is weak, the powder falls little in the initial stage of pressing shown in FIGS. 9A to 9C, but the powder rises up to the intermediate stage of pressing shown in FIG. 9D. This becomes large, and this movement of the powder causes cracks 114 to occur at the corners of the product, as shown in FIG.

On the other hand, the first and second fluid pressure cylinders 104,
When the force of 105 is strong, the powder drops largely in the initial stage of pressing, but since each step is pressed in a state of being hardened to some extent, the movement of the powder in the intermediate step of pressing is small, The above-mentioned problem of crack generation is small. However, FIG.
As shown in (b), variations in the density of the molded product become large, so that the product size in calculation will change significantly during sintering.

As described above, the first and second fluid pressure cylinders 1
The adjustment of the force of 04 and 105 was delicate and difficult to adjust. In addition, the force of the first and second fluid pressure cylinders 104 and 105 must be changed depending on the shape of the molded product.

The present invention has been made to solve the above-mentioned problems of the prior art, and the purpose thereof is to:
By changing the force of the fluid pressure cylinder that supports the movable punch during the pressure stroke, the movement of the powder is minimized to prevent the occurrence of cracks in the molded product and to achieve a highly accurate molded product. It is to provide a powder molding press that can be obtained.

[0016]

In order to achieve the above object, in the present invention, at least one of the upper punch and the lower punch is composed of a plurality of punches. In a powder molding press, a portion of which is supported by a fluid pressure cylinder as a movable punch, pressure control means for increasing the fluid pressure of the fluid pressure cylinder in accordance with the progress of pressurization is provided.

[0017]

According to the present invention, the force of the fluid pressure cylinder supporting the movable punch is increased as the pressure stroke progresses. The difference in the pressing force at the point becomes small, and the movement of the powder becomes as small as possible.

[0018]

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

FIG. 1 shows a tool set type powder molding press to which a powder molding press control method according to an embodiment of the present invention is applied.

The tool set 1 comprises a die plate 3 having a die 2 filled with powder, a lower first punch plate 5 arranged below the die plate 3 and holding a lower first punch 4, and a lower first punch plate 5. A lower second punch plate 7 arranged below the first punch plate 5 and supporting a lower second punch 6;
Fixed plate 9 fixed to the frame 8 of the press body
And a yoke plate 11 arranged below the fixed plate 9 and connected to the die plate 3 via a tie rod 10. The tie rod 10 is slidably inserted into the lower first punch plate 5 and the lower second punch plate 7. Further, the lower end of the core rod 13 fitted to the inner circumference of the lower third punch 12 is fixed to the yoke plate 11.

On the other hand, the upper punch 14 is connected to an upper ram 16 of the press via an upper punch plate 15, and is vertically reciprocally driven by the upper ram 16.

A first fluid pressure cylinder 17 for supporting the lower first punch 4 is provided between the lower first punch plate 5 and the lower second punch plate 7, and the lower second punch plate 7 and the fixed plate are also provided. A second fluid pressure cylinder 18 for supporting the lower second punch 6 is mounted between the two. Then, these first and second fluid pressure cylinders 17, 1
Pressure control means 19 is provided for increasing the fluid pressure of No. 8 in accordance with the progress of pressurization.

Although the first and second punches 4 and 6 are movable up and down, their upper limit positions are restricted by the first and second filling adjusting devices 40 and 41 as in the conventional example. The lower limit position is restricted by the first and second stoppers 42 and 43.

FIG. 2 shows the first and second fluid pressure cylinders 1 described above.
7 and 18 show control circuits.

The first and second fluid pressure cylinders 17 and 18 are provided in pairs, and are connected to the pump 20 via check valves 19 and 19. Further, a relief flow passage 22 is provided by branching from a flow passage 21 between the pump 20 and the first and second fluid pressure cylinders 17 and 18, and the relief flow passage 22 serves as a pressure control means capable of adjusting the relief pressure. A relief valve 23 capable of pressure control is provided. As the relief valve 23, a proportional electromagnetic relief valve, a digital relief valve, or the like can be used.

The relief valve 23 increases the relief pressure of the first and second fluid pressure cylinders 17 and 18 during the compression stroke as the pressurization stroke progresses. Whether to increase the pressure linearly or quadratically with the passage of time, and to what extent the minimum pressure and the maximum pressure are set, are determined by looking at the non-defective product at the time of molding.

Basically, the pressure rise of the powder pressed between the fixed lower third punch 12 and the upper punch 14 is the same, that is, about the same as the force per unit area applied to the lower third punch 12. Ideally, the pressure should be set to increase.
However, if a fluid pressure cylinder that can withstand the pressing force of the ram is used, the size of the equipment will be increased and the cost will be increased. Further, in reality, even if the pressures of the first and second fluid pressure cylinders 17 and 18 are considerably low, a good product can be obtained without cracks. Therefore, it is possible to obtain a good product with the size of the cylinder used in the current press. Is enough.

Also, the first and second fluid pressure cylinders 1
Regarding the pressure control of 7 and 18, besides using the pressure control relief valve, the discharge flow rate from the fluid pressure cylinder may be controlled by the flow rate control valve, and the supply pressure from the pump 20 is controlled. Alternatively, the fluid pressure of the first and second fluid pressure cylinders 17 and 18 may be changed according to the progress of pressurization.

As described above, by changing the passage of time and the relief pressure according to the size of the product, it is possible to set the movement of the powder as small as possible throughout the entire pressurizing process.

FIG. 3A shows a configuration example of the controller C of the relief valve 23. In this example, as shown in FIG. 3B, for example, the rotational displacement of the spindle 24 of the mechanical press is read by the encoder 25, and the relief pressure of the relief valve 23 is changed based on this signal.

That is, the controller C has a power supply 2
6, connected to the setting device 27 and the encoder 25,
The controller C drives a setting unit 28 in which the relationship between the displacement amount of the main shaft (corresponding to the pressurization stroke) and the control pressure is preset and stored by the setting unit 27, the power supply unit 29, and the actuator of the relief valve 23. The drive unit 30 is provided. Then, based on the input signal from the encoder 25, the relief valve 23 is drive-controlled so that the relief pressure corresponds to a predetermined stroke position.

The pressures of the first and second fluid pressure cylinders 17 and 18 may be continuously increased, or may be increased stepwise as shown in FIG. 3 (c). In the illustrated example, the number of stages is five, but it may be more or less depending on the precision of the molded product. In the illustrated example, the pressure is increased almost in proportion to the stroke, but it is considered that the applied pressure rapidly increases before the end of pressurization, so it is preferable to increase the pressure correspondingly. However, the pressure needs to be adjusted according to the size of the molded product.

The press is not limited to the mechanical type and the hydraulic type. In the case of the hydraulic press, the same result can be obtained by changing the pressure using a timer instead of the encoder.

Further, it is needless to say that the present invention is not limited to the tool set type press as in the present embodiment, and can be applied to a platen type press which cannot be removed from the press body.

FIG. 4 shows the pressure stroke of the apparatus of this embodiment.

FIG. 4A shows the filling state. That is, the feeder 32 fills the die 2 with a predetermined amount of powder. The filling depth of the lower first and second punches 4 and 6 is determined by the first and second filling devices 40 and 41 that regulate the vertical position.

FIG. 4B shows the upper punch 14 in contact with the powder filled in the die 2.

FIG. 4C shows the upper pressurization state. When the upper punch 14 is lowered to pressurize the powder, the lower first
The pressing force of the powder above the punch 4 increases. At this point, the first and second punches supporting the lower first and second punches 4 and 6 respectively.
The force of the fluid pressure cylinders 17 and 18 is set to be weak,
When the pressing force of the powder becomes larger than the supporting force of the first and second fluid pressure cylinders 17 and 18, the lower first punch 4 moves down.
The movement of the powder can be suppressed as much as possible because the pressure is lowered when the pressure is small.

FIG. 4 (d) shows a state in which both the upper punch 14 and the lower first punch 4 are lowered, and at this point, the lower second punch 4 is moved.
The pressure of the punch 6 increases. Then, when the supporting force by the second fluid pressure cylinder 18 becomes larger, the upper punch 14, the lower first and lower second punches 4, 6 are lowered.

Then, as shown in FIG. 4 (e), when the upper punch 14 is further lowered, the density of the powder is further increased.

Since the supporting force of the first and second fluid pressure cylinders 17 and 18 is increased in proportion to the increase of the pressurizing force, the lower first, second and third lower punches 4, 6 and 12 are made. The pressure is kept almost the same.

FIG. 4 (f) shows the pressurizing end position.

That is, the upper punch 14 is lowered and the lower first and second punches 4 and 6 are moved to the first and second stoppers 42 and 43.
The pressurization ends when it comes into contact with.

4 (g) to 4 (i) show the extraction process.

First, when the upper punch 14 rises to start the withdrawal and the die 2 is at the same position as the lower first punch 4,
The first stopper 42 comes off.

When both the die 2 and the lower first punch 4 are lowered to the same position as the lower second punch 4, the second stopper 43 is removed from the lower second punch 6, and the die 2 and the lower first punch 4 are removed. 4 and the lower second punch 6 descend to the same position as the lower third punch 12, and the extraction is completed.

In this extraction process, the filling pressure of the first and second fluid pressure cylinders 17 and 18 is lowered.

In this embodiment, the stepped molded product as shown in FIG. 1B has been described as an example, but the molded products 50, 51 as shown in FIG. 5 can be similarly applied. .

FIG. 6 shows an example of the structure of the upper punch 53 in the case of molding the molded product 51 having the step portion 52 on the outer periphery of the upper surface as shown in FIG. 5B.

That is, as for the upper punch 53, a plurality of punches, that is, the upper first and the upper second in the illustrated example, are used similarly to the lower punch.
The upper first punch 54 on the outer peripheral side is a movable punch supported by the upper first fluid pressure cylinder 56. In this example,
Also for the upper second punch 55, the upper second fluid pressure cylinder 57 is used.
However, the present invention is applied to the upper first fluid pressure cylinder 56. Further, in the illustrated example, the upper second fluid pressure cylinder 57 is pneumatically actuated to move the upper first fluid pressure cylinder 57.
The fluid pressure cylinder 56 is hydraulically driven.

Since the structure of the lower punch is as described in the above embodiment, the following description will be focused on the upper punch 53, and the lower punch is the same as that of the above embodiment. The reference numerals are given and the description thereof is omitted. The control circuit of the upper first fluid pressure cylinder 56 includes a first electromagnetic switching valve for switching the supply of the fluid pressure to the upper first fluid pressure cylinder 56 between the pressure source 58 and the upper first fluid pressure cylinder 56. 59 and the upper first fluid pressure cylinder 56
There is provided a pressure controllable relief valve 60 as a pressure control means for increasing the fluid pressure in accordance with the progress of pressurization.

Between the upper second fluid pressure cylinder 57 and the pressure source 61, there are provided second and third electromagnetic switching valves 62, 63 for switching the vertical movement of the upper second fluid pressure cylinder 57.

The upper limit positions of the upper first and second upper punches 54 and 56 are restricted by the upper end walls of the upper first and second fluid pressure cylinders 56 and 57.

Reference numerals 66 and 67 in the figure are release mechanisms for the stoppers 42 and 43 in the process of extracting the molded product after the completion of pressurization.

FIG. 7A shows a filling state. That is, the third electromagnetic switching valve 63 is energized, the first and second electromagnetic switching valves 59, 62 are de-energized, and the upper first fluid pressure cylinder 5
Hydraulic pressure is applied to 6 and air pressure is applied to the lower portion of the upper second fluid pressure cylinder 57. The upper first punch 54 moves downward and is positioned at the lowermost position by the hydraulic pressure of the upper first fluid pressure cylinder 56, and this dimension A can be adjusted by the adjusting nut 69 provided in the upper first fluid pressure cylinder 56. Is.

On the other hand, the lower first and second lower fluid pressure cylinders 6
By the air pressure of 4,65, the lower first and second punches 4,6
Is raised to a predetermined position and is filled with powder.

The transfer process is shown in FIGS. 7 (b) and 8 (a).

FIG. 7B shows a transfer start state, in which the upper first punch 54 comes into contact with the powder, and at the same time, the first transfer rod 71 comes into contact with the upper surface of the first fluid pressure cylinder 64. In this first fluid pressure cylinder 64, the lower first punch plate 5 and the piston rod 64a are fixed to the fixed plate 9, and the first transfer pin 72 is projectingly provided at the tip of the piston rod 64a.

In this embodiment, the transfer is to move the powder between the lower first punch 4 and the upper first punch 54. The protrusion amount S1 of the upper first punch 54, the first transfer rod 70, and the first transfer Distance from pin 72 S1 '
Are adjusted to the same size. Further, the distance S2 between the second transfer rod 71 and the lower second fluid pressure cylinder 65 at this time is set to the same dimension as S1 or a dimension larger than that. The lower second fluid pressure cylinder 65 is fixed to the lower second punch plate 7, the piston rod 65a is fixed to the fixed plate 9, and the second transfer pin 73 is projectingly provided at the tip of the piston rod 65a. These first and second transfer rods 70 and 71 are supported by a pneumatic cylinder (not shown).

FIG. 8A shows the transfer end state.

That is, at the same time when the upper second punch 55 is inserted into the die 2, the first transfer rod 70 and the first transfer pin 72 come into contact with each other, and the first transfer rod 72 is cushioned by a pneumatic cylinder (not shown). . On the other hand, the lower first and second fluid pressure cylinders 64,
The lower first and lower second punches 4 and 6 supported in a floating state by 65 are pushed down to move the powder to the upper punch 53 side.

FIG. 8 (b) shows a press-molded state. In this pressurizing stroke, the relief pressure of the upper first fluid pressure cylinder 56 is applied by the relief valve 60 as in the above embodiment. Increase with the progress of. At the end of pressurization, the piston contacts the upper end wall of the upper first fluid pressure cylinder 56, and the lower first and second punches 4, 6 are also
It is positioned by the lower first and second stoppers 42 and 43 shown in FIG.

After the molding is completed, the first and second electromagnetic switching valves 5
9 and 62 are energized, the third electromagnetic switching valve 63 is de-energized,
The hydraulic pressure of the upper first fluid pressure cylinder 56 is returned to the tank by the relief valve 60.

On the other hand, the lower first and second fluid pressure cylinders 64,
Air pressure also enters the descending side of 65, and balances with the ascending side to prevent lifting of the floating lower first and second punches 4, 6.

FIG. 8C shows the upper first and second punches 54, 5
5 shows the ironing stroke of 5.

In this process, when the molded product 51 is pushed out of the die 2 to reduce friction, the upper second punch 5 is pressed.
The upper first and second punches 54 and 55 perform an ironing operation by the air pressure at the upper part of the upper part.

FIG. 8D shows the extruded state of the molded product. The molded product 51 is extruded from the die 2 by moving the die 2, the lower first punch 4 and the lower second punch 6.

[0068]

EFFECTS OF THE INVENTION The present invention has the above-described structure and action. Since the force of the fluid pressure cylinder is changed during the pressurizing stroke, the movement of powder during the pressurizing stroke is minimized. It is possible to prevent cracking of the molded product and obtain a highly accurate molded product.

[Brief description of drawings]

FIG. 1 (a) is a schematic configuration diagram of a main part of a powder molding press according to an embodiment of the present invention, and FIG. 1 (b) is a sectional view showing an example of a molded product.

FIG. 2 is a circuit diagram of first and second fluid pressure cylinders of the powder molding press of FIG.

3 (a) is a control block diagram of the relief valve of FIG. 2, FIG. 3 (b) is a diagram showing an encoder mounting structure in the case of a mechanical press, and FIG. 3 (c) is a relationship between stroke and pressure. It is a graph.

4 (a) to 4 (i) are explanatory views of a pressing process of the powder molding press of FIG.

5 (a) and 5 (b) are views showing a modified example of the stepped molded product.

FIG. 6 is a diagram showing a device configuration example in the case where a plurality of upper punches are used.

7 (a) and 7 (b) are views showing a filling and transfer starting process of the apparatus of FIG.

8 (a) to 8 (d) are views showing a transfer end, pressurization and extraction process of the apparatus of FIG.

9 (a) to 9 (e) are explanatory views of a pressing process of a conventional powder molding press.

10 (a) to 10 (d) are control circuit diagrams of a conventional fluid pressure cylinder.

11 (a) and 11 (b) are diagrams showing a crack generation state and a density variation state of a powder molded product.

[Explanation of symbols]

 1 Tool Set 2 Die 4 Lower 1st Punch 6 Lower 2nd Punch 12 Lower 3rd Punch 14 Upper Punch 16 Upper Ram 17 First Fluid Pressure Cylinder 18 Second Fluid Pressure Cylinder 19 Pressure Control Means 22 Relief Valve

Claims (1)

[Claims] 1. A powder molding press in which at least one of an upper punch and a lower punch is composed of a plurality of punches, and a part of the plurality of punches is supported as a movable punch by a fluid pressure cylinder, A powder molding press characterized in that a pressure control means for increasing the fluid pressure of a fluid pressure cylinder in accordance with the progress of pressurization is provided.