JPS63194847A - Method and device for manufacturing mold - Google Patents

Abstract

PURPOSE:To obtain even a complicated mold with high productivity at low cost by forming a green-sand mold by pressurizing and compressing a casting sand with maintaining the inside of a mold frame where the cast and for self- hardening mold is filled up in a pressure reducing state, thereafter, hardening it by gas. CONSTITUTION:The pressure reducing and concurrently releasing device 51 holding a pattern plate 1 is fed with a casting sand 25 in a fixed amt. at the lower part of a casting sand packing device to perform an uniform packing inside a mold frame 5. Thereafter, the device 51 is ascended to bring the mold frame 5 into contact with a pressurizing device 31. In this state, the upper faces of the mold frame 5 and casting sand 25 are covered by a flexible film 37 and the casting sand 25 is shut off from the upper space. The inside of the mold frame 5 is made in pressure reducing state by sucking via a vent hold 1a and piping 59 from the lower side of the pattern plate 1 and the casting sand 25 is stamped by working a sand rammer 34 to form a green-sand mold in uniform density. A self-hardening mold is obtd. by passing a gas through this green-sand mold.

Description

[Detailed description of the invention] B. Industrial application field The present invention relates to a mold manufacturing method and an apparatus therefor.

Conventional technology For molds with complex shapes or molds in which multiple cold metals are placed close to each other, the fluidity of the molding sand is insufficient when green sand is used to form the mold, and the molding sand cannot be used in a sufficient amount. As a result, the resulting cast product is likely to have defects such as "scooping" and "washing" due to insufficient mold strength. In the case of large molds, green molds do not have enough strength to withstand the pressure of the molten metal injected into them, and the resulting large cast products suffer from "stretching" due to the lack of strength of the mold, in addition to the defects mentioned above. dimensional defects are likely to occur. Therefore, shell molds are often used for complex-shaped molds or molds in which a plurality of chilled metals are arranged close to each other, and self-hardening molds are often used for large-sized molds.

Shell molds require high mold material costs.Self-hardening molds take time to harden after molding, and if you try to shorten the hardening time, the pot life after mixing the molding sand will shorten, making molding difficult. There is a problem that the work becomes difficult. Among self-hardening molds, for example, in the CO2 process, water glass is used as a binder, and after molding, carbon dioxide gas is passed through the mold to shorten the mold due to the reaction between the water glass and carbon dioxide gas. However, for complex or large molds, it is difficult to distribute carbon dioxide gas to all parts of the mold, making it difficult to harden the mold uniformly and requiring a long time to harden. There are other problems.

C.8 Purpose of the Invention The present invention has been made in view of the above circumstances, and includes:
The purpose of the present invention is to provide a mold manufacturing method and an apparatus therefor, which can be performed with high productivity and low cost even in complex molds, molds in which a plurality of cold molds are arranged close to each other, or large molds. .

20 Structure of the Invention The first invention of the present invention is to fill a mold flask set in a model holding means in which a model is arranged, with self-hardening molding sand,
While maintaining the mold flask filled with this molding sand in a reduced pressure state, the molding sand is pressurized and compressed to form a green mold, and then the molding sand is passed through a vent in contact with the green mold. The present invention relates to a mold manufacturing method in which a gas is passed through a green mold and the green mold is hardened by the gas.

A second aspect of the present invention provides a molding sand filling means for filling molding sand into a molding flask set in a mold holding means in which a model is disposed; pressure reduction means for pressurizing the molding sand filled in the mold flask; gas supply means for passing gas through the green mold compressed and molded by the pressurization; hardening by the gas. a mold release means for separating the mold from the model holding means, a vent hole for allowing the gas to pass through the raw mold is provided so as to be in contact with the raw mold, and the molding sand is filled with molding sand. means, the pressure reduction means, the pressurization means, the gas supply means, and the mold release means are movable relative to the model holding means so as to face the model holding means. Related to manufacturing equipment.

E. EXAMPLE Hereinafter, the present invention will be specifically explained by taking as an example a mold for a chilled camshaft in which a chilled metal is arranged in the cam nose part.

The cam nose of the camshaft comes into sliding contact with the rocker arm or tappet during operation of the internal combustion engine, so wear resistance is required.The cam nose is chilled (rapidly solidified) using a chiller to create a hard white cast iron surface layer. Cast iron camshafts are often used. When a large number of camshaft models are pasted together in order to increase productivity, the cooling elements disposed in the cam nose portion of the mold come close to each other and the distance between them becomes narrow, causing the problem described above. In this example, this problem is solved as follows.

FIG. 1 is a schematic front view showing the operation of a depressurizing and mold releasing device, which will be described later.

The decompression and mold release device 51 is operated by a drive device (not shown).
It is fixed to a support stand 80 attached to a rotation shaft 81 that rotates 80 degrees, and on the support stand 80 fixed to the rotation shaft 81,
Two depressurizing/mold releasing devices 51 are located symmetrically with respect to a center line (not shown) of the rotating shaft 81 at positions (1) and (2), respectively. By means of bars 82 and 83 that pass through the support base 80 and are moved up and down by a drive device (not shown), the decompression/mold release device 51 is raised or lowered in a predetermined process, and can be moved up and down between ■ and ■ and between ■ and ■. It is.

■The upper part is the molding sand filling device 11 and the pressurizing device 51.
are installed in sequence, and gas supply device 4 is installed above positions ◎ and ■.
1 is provided.

2 to 8 are schematic sectional views showing the manufacturing process of a mold for casting a chilled camshaft. Generally, a camshaft is provided with a plurality of cams, and the cam nose of each cam faces in a predetermined radial direction of the camshaft. The cam part shown is cut away.

FIG. 2 fa) shows a state in which a chiller 4 is placed on the cam nose portion of the model 3 on the pattern plate 1, and a mold flask 5 is placed on the peripheral edge of the pattern plate 1.

The pattern plate 1 is held on a decompression/mold release device 51.

FIG. 2 (bl is a partially enlarged view of FIG. 2(a)), where the model 3 and chiller 4 on the pattern plate 1 are not present.
The ventilation hole 1a with the air vent 2 arranged on the upper end and the die-cutting pin 57 with the support part 57a on the upper end are positioned at the ■ position by the rise of the bar 82 in FIG. 1, and the molding sand is filled as shown in FIG. It is located below the device 11.

The decompression/mold release device 51 includes a sand filling plate 24 in which the upper opening 5a of the mold flask 5 is located at the lowest part of the molding sand filling device 11.
It is positioned so as to match the opening 24a of. A predetermined amount of foundry sand is stored in a sand hopper 12, and is introduced into a kneading machine 15 by opening a bottom portion 13 that can be opened and closed by operating an air cylinder 14, where it is kneaded by a screw 16 that is rotated by the drive of a motor M1. .

Note that predetermined amounts of the binder and curing agent, which will be described later, are added to the kneader 15 when casting sand is introduced into the kneader 15.

The above binder contains a thermosetting resin (e.g. furan-based or phenolic resin) and an acid curing agent (e.g. organic sulfonic acid).
use. The kneaded foundry sand 25 is transferred to the air cylinder 1
When the bottom cover 18 is opened by 9, the sand is thrown into the sand filling hopper 20 via the chute 17. Hopper 2
A piston rod 23a of an air cylinder 23 is attached to the hopper 20.
moves along the guide rail 22. At this time, the molding sand 25 is transported from the hopper 20 to the mold flask 5 and the sand filling plate 24 by the screw 21 driven by the motor M2.
The inside of the opening 24a is uniformly filled.

Next, the sand filling plate 24 is slightly raised by a drive device (not shown) and extracted from the molding sand 25, and then the air cylinder 23 is driven to move the hopper 20, the guide rail 22,
The kneader 15 and sand hopper 12 are moved from a position above the mold flask 5 to the left in the figure and removed.

Next, the bar 82 in FIG. 1 further rises, and the decompression/mold release device 51 supporting the mold flask 5 rises, and as shown in FIG. to confront each other. A housing 32 to which a number of sand drummers 34 are attached is attached to the piston rod 33a of the air cylinder 33 fixed to the beam 33b, and a coil spring 36 is attached to the lower side wall of the housing 32 so as to surround the guide pin 35. is,
An abutment plate 37a is attached to the lower end of the coil spring 36 to sit on the edge of the mold flask 5, and a flexible membrane (for example, a thin plate of soft rubber) 37 is attached to the abutment plate 37a so as to cover the molding sand 25. installed on.

As described above, the depressurization/mold release device 51 is raised and the edge of the mold flask 5 supported thereon comes into contact with the contact plate 37a, so that the upper surfaces of the mold flask 5 and the molding sand 25 become flexible. membrane 37
The inside of the molding sand 25 is shielded from the upper space.

In this state, the inside of the suction box 54 of the decompression/mold release device 51 located below the pattern plate 1 is opened through the exhaust hole 54a.
, suction and pressure reduction with a pressure reduction pump 60 via piping 59,
The inside of the mold flask 5 is brought into a reduced pressure state through the ventilation hole 1a and the vent hole 2 (see FIG. 2(b)).

When the sand rammer 34 is driven while maintaining the above-mentioned reduced pressure state, the foundry sand 25 shown in FIG. is formed. Since a large number of sand rammers 34 are arranged, narrow portions are sufficiently pounded and hardened, the green mold 38 has a uniform density, and the mold after hardening becomes uniformly elastic. During this pressurization, the exhaust port 54a of the suction box 54
Since the pressure inside the suction box 54 is reduced by the pressure reducing pump 60, the air coexisting with the foundry sand 25 shown in FIG. 4 is discharged via the air vent 2 and the ventilation hole 1a shown in FIG. The density of the green mold 38 increases, making the mold even stronger after hardening. The flexible membrane 37, the suction box 54, the exhaust hole 54a, the piping 59, and the vacuum pump 60
The pressure reducing means 39 is constituted by this.

When the green mold 38 is formed, the air cylinder 33 is driven, and the pressurizing device 31 is raised and returned to its original position.
The bar 82 in FIG. 1 is lowered, and the decompression/mold release device 51 that supported the mold flask 5 is returned to its original state and placed on the support stand 81. Next, the support stand 81 rotates 180°, and the decompression/mold release device 51 changes its position from the ■ position to the ■ position, and another depressurization/mold release device 151 located at the ■ position is moved to the vertical position. Then, a green mold is formed through the same steps as described above.

The decompression/mold release device 51, which is placed with the green mold 38 and is located at the ◎ position in FIG. and raw mold 38
is pressed against the gas supply device 41 from below.

The gas supply device 41 is composed of a gas introduction part 42 having a gas blowing port 42a, an outer peripheral wall 43 and an inner peripheral wall 44 attached below the gas introduction part 42, and the outer peripheral wall 43
are a canopy 43a, a side wall 43b, and a canopy 43a and a side wall 43b.
and a bellows 43c located between the mold flask 5 and the side wall 43b is configured to abut against the upper end of the mold flask 5. When hot air of 50 to 170°C is sent from the gas blowing port 42a,
The hot air is guided into the space 46 between the outer peripheral wall 43 and the inner peripheral wall 44, the bellows 43c extends and the side wall 43b comes into pressure contact with the mold flask 5, and the space between the gas supply device 41 and the mold flask 5 is kept airtight. The hot air flows through the exhaust port 54a and the air vent 1a by the vacuum pump 6o, and the heat of this hot air hardens the binder in the raw mold 38, forming a self-hardening mold 47A. The above-mentioned pressure reduction can also be done via a vent provided in the mold flask, as in the case of green mold forming described above, but in this case, the gas is sufficient to reach all parts of the green mold. Consideration must be given to the plan so that it is supplied to the public.

Next, the bar 83 shown in FIG. 1 is lowered, and at the same time, the depressurization/mold release device 51 is separated from the gas supply device 41 and lowered, returning to the position (2) and placed on the support base 80.

Next, or at the same time as the lowering, the depressurizing/releasing device 51 is operated to release the self-hardening mold 47A from the mold flask 5 and pattern plate 1.

As shown in FIG. 7, the depressurization/mold release device 51
Air cylinder 53 provided inside and air cylinder 53
A push-up plate 56 is attached to the piston rod 53a, and a die-cutting pin 57 is attached to the push-up plate 56'. It is inserted into the through hole 1b of the pattern plate 1 placed on the suction box 54 that accommodates the raising plate 56, and the upper surface of the support part 57a of the die-cutting pin 57 is at the same height as the upper surface of the pattern plate 1 by the coil spring 58. The piston rod 53 is located when the air cylinder 53 is driven.
a rises relative to the pattern plate 1, the push-up plate 56 moves up using the guide pin 55 as a guide, the die-cutting pin 57 rises against the force of the coil spring 58, and the support part 57a cools down. The self-hardening mold 47A with the pad attached is extracted from the pattern plate 1 and the mold flask 5 and raised, and the self-hardening mold 47A is conveyed to a predetermined position by a grasping device (not shown).

A lower mold 47B of the self-hardening mold is made in the same manner as the upper mold 47A of the self-hardening mold, and when the two are combined, a self-hardening mold 47 for chilled camshaft casting is completed as shown in FIG. 8(a). The lower mold 47B is turned upside down during transportation.

As mentioned above, the cams of the camshaft are provided with their cam noses facing in a predetermined radial direction of the camshaft, and as shown in FIGS.
Figures 7 and 8 [al shows the cam nose part is the cutting surface 47
A cross section of the part facing upward from the upper mold is shown.

Fig. 8 (bl is a sectional view of the part where the cam nose part of the same mold 47 faces downward from the cutting surface 47a, the same figure f
c) is a sectional view of a portion of the same mold 47 in which the cam nose portion faces toward the cutting surface 47a.

In this example, the temperature of the foundry sand was 30°C, the amount of thermosetting resin was 0.8% based on the sand, the amount of acid curing agent was 40% based on the above thermosetting resin, and blown air was used. The temperature of is 15
0°C1 air blowing amount is approximately 30mN per unit square meter
/min, the thickness of the upper and lower molds allowed for rapid mold release.

In addition, the strength of the mold after release increases further by being kept at room temperature until pouring, and after 5 minutes, each part reaches 10 kg/c4 or more, which is important for obtaining high quality cast products. In particular, a good mold was obtained that was strong and had a high dimensional accuracy of 75X.

In this example, hot air is sent from the molding sand side and passed through the ventilation holes of the pattern plate to harden the mold, but in contrast, hot air is sent from the back side of the pattern plate through the ventilation holes. Alternatively, the resin may be passed through a mold to harden the mold.

FIG. 9 is a front view of a camshaft material obtained by pouring metal into the mold 47 of FIG. 8. The shaft 63 of the cam shaft 61 is provided with three journal nozzle portions 64, one sprocket wheel portion 65 and one eccentric cam portion 66 for the fuel pump, eight cam portions 62, and a cam nose portion 62a of the cam portion 62.
, 21 portions 62b on the opposite side are oriented upward, forward, backward, and downward with a phase difference of 90°.

Note that some foundry sand binders impair the fluidity of foundry sand, and if such binders are used, the screw 21 will become clogged in the foundry sand filling process shown in FIG. It may not be possible to execute smoothly. In such a case, a hopper 70 as shown in FIG. 10 can be preferably used instead of the sand filling hopper 20 shown in FIG. 3.

The hopper 70 is similar to the construction method, and the drive roller 72
The molding sand 25 is placed on a heald conveyor 71 driven by a belt conveyor 71, and is vibrated in substantially vertical and horizontal directions by pie breaks 70a and 70b. It passes through the gap 74 between them and is fed onto a lower pattern plate (not shown) as indicated by the arrow.

In this example, a common pressure reducing and mold releasing device is used for the pressure reducing means and the mold releasing means, but the pressure reducing device and the mold releasing device may be provided separately.

Although the above example is an example of manufacturing a mold for a chilled camshaft, the present invention is also applicable to cast products other than chilled castings.
In particular, good results can be obtained when applied to the production of molds for cast products having shapes that prevent clogging with foundry sand, and the production of large-sized molds.

In addition, in addition to using thermosetting resin as a binder and hardening the green mold with hot air, we also use the incure method, which hardens the binder resin with amine gas, for self-hardening molds.
The present invention is applicable.

Further, although the above example is an example of molding using a pattern plate, the present invention is similarly applicable to molding using a model holding means other than the pattern plate.

As described in detail, the present invention molds a green mold by pressurizing and compressing the mold flask filled with self-hardening molding sand while reducing the pressure. A highly green self-hardening mold is formed. Furthermore, since gas is passed through the vents in contact with the raw self-hardening mold to harden the raw self-hardening mold, the gas is sufficiently supplied to all parts of the raw mold. supplied to As a result, the molds obtained are uniformly strong, with or without cooling metal,
Irrespective of the shape of the cast product or the size of the mold, the resulting cast product is free from casting defects or dimensional defects due to insufficient mold strength, and the yield in manufacturing the cast product is improved. Moreover, since the mold is hardened in a short time, the productivity of molding is high.

[Brief explanation of the drawing]

The drawings all show embodiments of the present invention, and Fig. 1 is a schematic front view showing the movement of the depressurization/mold release device, and Fig. 2 (al shows the cooling metal and mold flask on the pattern plate). A sectional view showing the set state, Fig. 2 (bl is a partial enlarged view of Fig. 2 (al), Fig. 3 is a sectional view showing the state of filling with foundry sand, Fig. 4 is a drawing of the foundry sand (
Figure 5 is a cross-sectional view showing the state immediately before the molding process (pressurization, compression), Figure 5 is a cross-sectional view showing the completed green mold after the molding sand has been painted, and Figure 6 is the state in which the green mold is hardened by supplying hot air. Figure 7 is a cross-sectional view showing the state of mold release; Figures 8 (al, (b) and (C1) are cross-sectional views of the mold;
The figure shows the cast chilled cam shaft IR#'li1 figure
! FIG. 10 is a front view of the material surface tiγl, and FIG. 10 is a partial sectional view showing an example of a hopper for filling molding sand. In addition, in the symbols shown in the drawings, 1... Pattern plate 1a...
...Pattern plate ventilation hole 2...
・Air vent 3...Model 4...Cold metal 5...Mold flask 11...Cast sand Filling device 20.70...
...... Hopper 24 for filling molding sand...
...Mold sand plate 25...Molding sand 31...Pressurization device 33.53...Air cylinder 34...
...... Sand drummer 37 ...... Flexible membrane 38 ...... Raw mold 39 ...... Pressure reduction means 54 ... ...Suction box 41 ... Gas supply device 42 ... Gas introduction part 42a ... Gas blowing port 47 ...・・・
...Mold 47A...Top mold 47B...Bottom mold 51...Depressurization/mold release device 56...・
...Push-up plate 57...Mold-cutting bottle 57a...Mold support part 60 of the die-cutting bottle
......Decompression pump 61...Child cam shaft material.

Claims (1)

[Scope of Claims] 1. Filling molding sand for self-hardening molds into a molding flask set in a model holding means in which a model is placed, and maintaining the inside of said molding flask filled with this molding sand in a reduced pressure state. Meanwhile, the molding sand is pressurized and compressed to form a green mold, and then a gas is passed through the green mold through a vent in contact with the green mold, and the gas is used to form the green mold. A mold manufacturing method that hardens the mold. 2. a molding sand filling means for filling molding sand into a molding flask set in a mold holding means on which a model is arranged; a depressurizing means for reducing the pressure in the molding flask filled with the molding sand;
a pressurizing means for pressurizing the molding sand filled in the mold flask; a gas supply means for passing gas through the green mold compressed and formed by the pressurization; and a mold holding the mold hardened by the gas. a mold releasing means separated from the means, a vent hole for passing the gas through the green mold is provided so as to be in contact with the green mold, and the molding sand filling means, the depressurizing means, A mold manufacturing apparatus, wherein the pressurizing means, the gas supply means, and the mold releasing means are movable relative to the model holding means so as to face the model holding means.