JP2003275846A - Sand mold for casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sand mold for casting which has light weight and obtains a cast product having high precision of the shape and the dimension and can efficiently manufacture in small consumption of the molding sand at a low cost. <P>SOLUTION: At least one of sand mold members 1-3 is composed of a laminated molding material laminatedly formed in order as binding hardened layers by irradiating the molding sand layer with laser beam into each layer when a three-dimensional model is sliced in parallel into plurality of layers. Then, hollow parts 10, 20A, 20C, 30, having non-pouring spaces in the, sand mold members 1-3, are formed and gas venting holes communicating with the outer part of the mold from the hollow parts 10, 20A, 20C, 30, are arranged. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand mold for casting used for producing metal castings such as aluminum castings.

[0002]

2. Description of the Related Art In sand mold casting, conventionally, a product type wooden mold is manufactured, the mold sand in which the wooden mold is arranged is filled with mold sand and hardened, and the wooden mold is removed. A method has been adopted in which a sand mold is used as a mold, a molten metal is poured into the mold, and after cooling and solidification, the sand mold is disassembled and a cast product is taken out. Then, in the casting method, the gravity method of injecting the molten metal into the inside of the mold from the gate on the upper surface of the mold, and placing the mold on a holding furnace having a pouring port opened above,
There is a low pressure system in which the molten metal inside is poured into the mold from the pouring port through the pouring port on the lower surface of the mold by applying pressure to this holding furnace, but in any case, the volume due to the cooling and solidification of the molten metal inside the mold Because of contraction, risers are commonly provided to supplement this contraction volume. Further, in the mold applied to the gravity method, since the sprue is opened upward, the sprue is often used also as the feeder.

For example, the sand mold shown in FIG. 10 is an aluminum alloy air surge tank T for an automobile engine shown in FIG.
It is used for casting by the gravity method of
It is composed of an upper mold 61 and a lower mold 62, and a core 63 forming an internal space of the air surge tank T. Then,
The gates 61a and 61b provided on the upper die 61 are also used as feeders, and are long in the vertical direction and expand to the inlet side, that is, the upper side in order to secure the molten metal volume as the feeder and to obtain the feeder pressure by the potential energy. It is set in a diametrical form. Reference numeral 64 is an air vent hole provided in the upper mold 61, and AL is a poured aluminum alloy. Although not shown, the upper die 61 in this case is provided with a feeder corresponding to the tank constituent portion 51 of the air surge tank T, in addition to the sprues 61a and 61b. The hot water also has a shape that expands to the upper side.

[0004]

By the way, conventionally, the sand mold for casting has a simple rectangular box shape irrespective of the shape of the object to be cast, in view of the processing cost when manufacturing it from a wooden mold. Although it is general, because of this, there are many unnecessary meat parts from the viewpoint of casting functions such as strength, the weight is so large that it requires a great deal of labor and energy for handling, and the amount of mold sand used for mold manufacturing is also large. There was a problem that it would increase. In particular, in the case of a spout that also serves as a feeder and an upper die in which the feeder is set to be long in the vertical direction, the vertical thickness becomes large, so that the weight and the sand consumption of the mold increase.

On the other hand, in casting, distortion of the casting mold during pouring may cause cracking of the casting mold or deterioration of the shape and dimensional accuracy of the cast product. The larger the heat capacity, the larger the temperature difference between the vicinity of the pouring space and the distant portion at the time of pouring, so that distortion due to the difference in the degree of thermal expansion easily occurs. Particularly in casting using a core, for example, a core having a large diameter difference between a thick portion and a thin portion, or a bulky portion (tank constituent portion) having a large volume such as the core 63 used for casting the air surge tank T. When the core has a large difference in heat capacity depending on the part, such as the one in which the shaft-shaped part (tube structure part) is connected to the core, it is easy to cause damage to the core itself and uneven thickness of the cast product. was there.

[0006] In view of the above situation, the present invention is a casting sand mold, which is easy to reduce in weight, can obtain a casting product with high shape and dimensional accuracy, and can be manufactured efficiently at low cost with low sand consumption. It is intended to provide you with what you can.

[0007]

In order to achieve the above object, a sand mold for casting according to the invention of claim 1 is provided with at least one sand mold member 1 to 3 if indicated by reference numerals in the drawings.
However, each layer when the three-dimensional model is sliced in parallel into a number of layers is formed by a layered product M which is sequentially layered as binding hardening layers P _{1 to} Pn by irradiating the mold sand S layer with the laser beam L, Hollow portions 10, 20A to 20C, 30 serving as non-pouring spaces are formed in the sand mold members 1 to 3, and vent holes 4 and 5 communicating from the hollow portions 10, 20A to 20C, 30 to the outside of the mold are formed. It is configured to be provided.

In the sand mold for casting having the above construction, the sand mold members 1 to
Since 3 has hollow portions 10, 20A to 20C and 30, the weight of the sand mold member is reduced and the consumption of the mold sand is reduced, and the temperature difference of the entire sand mold members 1 to 3 at the time of pouring is small due to the reduction of the heat capacity. Therefore, distortion is less likely to occur. Then, since the air in the hollow portions 10, 20A to 20C, 30 can enter and exit through the ventilation holes 4, 5,
There is no effect on the mold due to expansion and contraction due to temperature changes before and after pouring. Further, the sand mold members 1 to 3 are the laser beams L.
Since it is a three-dimensional model in which thin layers of sand that have been bound and hardened by the heat of are laminated and integrated, the hollow parts 10, 2
It is possible to freely set 0A to 20C, 30 and easily discharge and remove the uncured sand S filling the hollow portions 10, 20A to 20C, 30 after modeling from the ventilation hole 4.

According to a second aspect of the present invention, in the casting sand mold of the first aspect, the hollow portions 10, 20A to 20C, 30 are provided.
The thickness of the circumference is set to 20 mm or more. In this case, the sand mold members 1 to 3 are hollow parts 10 and 2
Even if it has 0A to 20C and 30, sufficient strength as a mold is secured.

According to a third aspect of the present invention, in the sand mold for casting according to the first or second aspect, the sand mold member is an upper mold 1 having gates 6A, 6B or / and feeders 7 which are open upward. . In this case, the upper mold 1 has the sprues 6A and 6B.
Or / and the vertical thickness must be increased by forming the feeder port 7, but the hollow portion 10 can reduce the weight.

According to a fourth aspect of the invention, in the sand mold for casting according to the first or second aspect, the sand mold member is the core 3. In this case, the core 3 has a shape in which the size varies depending on the parts, such as a shaft shape in which the diameter difference between the thick portion and the thin portion is large, or a shape in which the shaft portion is connected to a large volume lump portion. However, since the entire wall thickness can be averaged by the hollow portion 30, the difference in heat capacity between the portions becomes small, and the entire portion has a uniform temperature during pouring, so that no distortion occurs.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a sand mold for casting according to the present invention will be specifically described below with reference to the drawings.

The casting sand mold shown in FIG. 1 is used for casting the aluminum alloy air surge tank T for an automobile engine shown in FIG. 9 by the gravity method, and includes an upper mold 1 and a lower mold 2. And a core 3 forming an internal space of the air surge tank T. The upper mold 1, the lower mold 2, and the core 3 are all manufactured by a layered molding method using molding sand as a molding material.

The air surge tank T to be cast is a J-shaped tank which communicates with the central portion of the tank 51 and a horizontally long open tank component 51 which is connected to a manifold member with a branch pipe (not shown) to form a closed tank. And a projecting edge portion 51 for connection on the periphery of the opening of the tank portion 51.
and a square flange portion 5 for connecting to the throttle port of the engine on the outer periphery of the tip of the curved pipe portion 52.
2a, and a reinforcing plate portion 53 that connects the tank 51 and the curved pipe portion 52.

Corresponding to the inner shape of the air surge tank T, the core 3 has a substantially τ shape in which the tank space forming portion 3a and the curved pipe space forming portion 3b are integrated, and the entire width of the tank space forming portion 3a. It has a substantially rectangular baseboard 31 and a short-axis type baseboard 32 extending from the curved pipe space forming portion 3b.
As shown in FIG. 4, the inside is a hollow portion 30, and the hollow portion 30 sets the entire thickness to a substantially equal thickness. A vent 30a communicating with the hollow portion 30 is provided on the end surface of the skirting board 32.

The upper mold 1 is provided with two sprue gates 6A and 6B which are open upward, three riser spouts 7 and an air vent hole 8, and, as shown in FIGS. Child 3
The recess 11 that houses the upper half of the core and constitutes the mold space, and the baseboard receiving portions 11a and 1a corresponding to the baseboards 31 and 32 of the core 3.
1b and each fitting protrusion 23 of the lower mold 2 (see FIGS. 1 and 8)
It has a fitting recess 12 that fits properly. The inner spaces of the sprues 6A and 6B are set to have a shape that is long in the vertical direction and has a diameter that is expanded upward so as to also serve as a feeder.
And the sprue 6B communicates with the runner facing the skirting board 32 of the core 3 when assembled. Further, the triple riser gates 7 are widened to the upper side, and the air surge tank T in the mold space
And communicates with a position corresponding to the tank constituent part 51.

Therefore, as shown in FIGS. 2 and 7 and 8, a hollow portion 10 is formed inside the upper mold 1. The hollow portion 10 constitutes a non-pouring space separated by a meat portion 13 with respect to a recess 11 serving as a mold space, baseboard receiving portions 11a and 11b, sprues 6A and 6B, riser spout 7, and air vent hole 8. And the ventilation holes 4 provided at a plurality of locations on the peripheral wall portion 1a.
Communicates with the outside of the mold.

The lower mold 2 has, on the upper surface thereof, a recess 21 for accommodating the lower half of the core 3 and forming a mold space, and a baseboard 3 of the core 3.
Baseboard receiving portions 21a and 21b corresponding to 1 and 32, the sprue 7
The arc-shaped recess 22 that constitutes the runner communicating with A, and the truncated conical projections 23 and 2 for positioning with the upper mold 1
3, small recesses 24, 24 that serve as a weir connecting the recess 21 and the arc-shaped recess 22, and a groove 25 extending from the end surface of the skirting board receiving portion 21b to the mold peripheral edge are formed.

Further, as shown in FIGS. 3 and 7 and 8, inside the lower mold 2, a recess 21 and baseboard receiving portions 21a, 21 are provided.
The hollow portion 20 serving as a non-pouring space, like the hollow portion 10 of the upper mold 1, is provided in three regions outside the portion where b and the arcuate recess 22 are formed.
A, 20B and 20C are formed. Then, these hollow portions 20A, 20B and 20C are respectively provided with the peripheral wall portion 2
The vent hole 4 provided in a communicates with the outside of the mold.

In order to manufacture the upper mold 1 and the lower mold 2 and the core 3 by the above-mentioned additive manufacturing method, first, a design model is sliced in parallel on a computer into a number of layers P ₁ to Pn having a thickness of 150 to 250 μm. Data of each cross-section pattern at the time of doing is created, this data is input to the controller of the additive manufacturing apparatus, and the sliced layers are automatically generated by the modeling apparatus by the molding sand S (see FIGS. 2 and 3) of the molding material. Layers are formed one by _one from the bottom layer P ₁ . In addition, this mold sand S
In general, a resin coated sand in which the surface of sand particles is coated with a thermosetting resin component (for example, a mixture of a main resin such as phenol resin and a curing agent such as hexamethylenetetramine) as a binder is used.

2 and 3 are schematic vertical cross-sectional side views showing an example of the additive manufacturing apparatus. In the layered modeling, as shown in FIG. 2, a base plate 43 is placed on an elevating table 42 arranged in a box-shaped modeling frame 41, and a horizontal movement of a recoater 44 causes one layer of the mold sand S to be parallel sliced. It is placed on the base plate 43 with a thickness, and the surface of this mold sand S layer is irradiated with the laser beam L along the sectional pattern of the lowermost layer P ₁ . As a result, the thermosetting resin component on the particle surface of the mold sand S is melted by the heat of the laser beam L and undergoes a hardening reaction, and adjacent sand particles are bound to each other through the hardened resin, and the entire irradiation area is integrated. A first layer (bottom layer) P ₁ having a two-dimensional pattern formed of a thin layer of the binding and hardening mold sand S is formed. Then, the elevating table 42 is lowered by the thickness of the one layer, and the mold sand S is newly placed with a thickness corresponding to the one layer, and the laser beam L is irradiated in the same manner to bind and harden the layer corresponding to the second layer P _2. After that, by successively lowering the elevating table 2 one layer at a time and repeating the supply of the mold sand S and the irradiation of the laser beam L in the same manner, all the layers sliced in parallel are finally obtained as shown in FIG. A layered product M in which P _{1 to} P _n are laminated and integrated is formed. In FIG. 6, the upper mold 1 is shown as the layered product M.

When the layered molding is completed in this way, the molding frame 4
The whole one is removed from the lift table 42, and the uncured mold sand S is removed to take out the layered product M formed. At this time, the hollow part 10 of the upper mold 1, the hollow parts 20A to 20C of the lower mold 2, and the hollow part 30 of the core 3 are all filled with uncured mold sand S. Since S has a very high fluidity, it can be removed by flowing it out from the ventilation hole 4 in the upper and lower molds 1 and 2, and from the ventilation hole 30a in the core 3. The recoater 44 receives the mold sand S from the material supply device 47 arranged at both ends of the moving stroke, and horizontally moves while allowing the mold sand S to flow out from the slit-shaped opening 44a at the lower end. One mold sand S layer is formed by horizontal movement. Reference numeral 70 is a laser oscillator such as a carbon dioxide gas laser, and 71 is an XY scanner for controlling the irradiation direction of the laser beam L.

The obtained layered product M is weak in strength, leaving some unreacted parts in the thermosetting resin component binding the sand particles, and therefore the surface is usually first rubbed with a gas burner. Then, the surface layer portion is hardened, and the resin component is completely cured by performing a post-cure heat treatment in a heating furnace or the like for a predetermined time.

The upper and lower molds 1 of the layered product thus obtained
The core 2 and the core 3 are assembled as shown in FIGS. 7 and 8 to form a mold, and the molten metal AL of the aluminum alloy is poured into the mold space through the gates 6A and 6B, and the molten metal A is also supplied to the feeder port 7.
L is supplied and the molten metal AL is cooled and hardened. Note that FIG.
As shown in FIG. 3, the groove portion 25 provided on the upper surface of the lower mold 2 faces the ventilation hole 30a of the core 3 whose inner end is assembled, and when the upper mold 1 is fitted, the groove 25 is removed from the hollow portion 30 of the core 3. A ventilation hole 5 communicating with the outside is formed. Then, by pouring the molten metal AL, the inside of the hollow portion 10 of the upper mold 1 and the hollow portions 20A of the lower mold 2
The air in the hollow portion 30 of the core 3 in 20C rises in temperature and expands. The volume increase due to this expansion is discharged from the vent holes 4 and 5 to the outside of the mold, and the volume decrease due to cooling is also increased. It will be supplemented by the inflow of outside air from the vent holes 4 and 5,
There is no concern that the mold will be damaged by the internal pressure fluctuations of the hollow portions 10, 20A to 20C, 30.

The molten metal AL shrinks in volume as it cools and hardens.
A, 6B and the molten metal AL filled in the feeder 7 are replenished by entering into the mold space by their own weight. Thus, when the cooling and hardening of the molten metal AL is completed, the mold is disassembled and the intake surge tank T of the cast product is taken out. In addition, core 3
Can be easily removed from the hollow portion of the cast product by applying vibration to decompose it into sand particles.

In the sand mold for casting having the above construction, the upper and lower molds 1 and 2 and the core 3 are all hollow portions 10 and 20A to 20.
Since it has C and 30, it is extremely light in weight for its apparent size, and the labor and energy required for its handling are significantly reduced, and the upper and lower molds 1, 2 and the core 3
Since the decrease in the heat capacity reduces the overall temperature difference during pouring, distortion is less likely to occur. Above all,
The core 3 has a shape in which a tube space forming portion 3b having a curved shaft shape of varying thickness is integrated with a tank space forming portion 3a having a large volume. Since the entire wall thickness is averaged by the hollow portion 30 and there is almost no difference in heat capacity between the portions, the whole is brought to a uniform temperature during pouring, so that no distortion occurs. Therefore, the intake surge tank T of the obtained cast product has a uniform wall thickness of the tank 51 and the curved pipe portion 52 and has high shape and dimensional accuracy, and the upper and lower molds 1, 2 and 3 due to distortion at the time of pouring. The core 3 does not crack.

On the other hand, hollow portions 10, 20A to 20C, 30
Since the mold sand S removed from the above can be reused for molding, the mold sand consumption required for the mold production is reduced, the material cost is reduced accordingly, and resource saving can be contributed. In addition, since this sand mold for casting is manufactured by a layered manufacturing method in which thin layers of sand that have been binding and hardened by the heat of a laser beam are laminated and integrated to obtain a three-dimensional modeled object, the conventional manufacturing method is used. A mold for filling with mold sand and a wooden mold for the product are not required, and it can be manufactured extremely efficiently in a short time, and the area to be hardened by the laser beam L is reduced by the amount of the hollow portions 10, 20A to 20C, 30. However, since the time required to form each cured layer is shortened by that much, the manufacturing efficiency is improved even in the case of additive manufacturing.

In the above-mentioned embodiment, the sand mold for casting used for casting the aluminum alloy air surge tank T for automobile engine is exemplified. However, the present invention is applicable to all sand molds for casting to obtain cast products in various forms. It goes without saying that it can be applied. Therefore, the shape and size of the hollow portion and the position of the ventilation hole in each sand mold member may be appropriately set according to the form of the mold space (pouring space), the thickness of the sand mold member, the required strength, and the like. Therefore, in order to secure general strength as a sand mold for casting, the wall thickness around the hollow portion may be set to 20 mm or more. Although it depends on the shape of the cast product, the sand mold can reduce the weight up to about 40% by providing such a hollow portion.

The molds to be applied include those without cores and those composed of sand-shaped members which are multi-divided into three or more pieces. Further, although the sand mold of the above-mentioned embodiment is used for the gravity type casting, the present invention is also applicable to the sand mold used for the low pressure type casting. However, in the additive manufacturing method, there is no need for die cutting, so it is possible to manufacture a sand mold in which the core is integrated with the upper mold or the lower mold, or a non-divided mold, that is, a sand mold with an internal mold space. The present invention can also be applied to these. Further, according to the size and shape of the casting, the casting sand mold of the present invention can have various settings of the number and arrangement of the sprue and the sprue, and the sprue does not also serve as the riser, and only the sprue serving as the riser is used. It is also possible to adopt a configuration without a feeder.

[0030]

According to the invention of claim 1, as a sand mold for casting, at least one sand mold member has a hollow portion serving as a non-pouring space, and a ventilation hole communicating from the hollow portion to the outside of the mold is provided. Therefore, it is extremely lightweight for its apparent size, the labor and energy required for its handling are significantly reduced, distortion is unlikely to occur, the wall thickness is uniform, and the shape and dimensional accuracy are high. It is possible to obtain a cast product, to prevent cracks due to distortion during pouring, to reduce the amount of mold sand used for mold manufacturing, to contribute to resource saving, and to provide a product that can be manufactured efficiently at low cost. .

According to the second aspect of the present invention, there is provided the above-mentioned sand mold for casting, which has sufficient strength as a mold since the circumference of the hollow portion has a certain thickness or more.

According to the invention of claim 3, in the above-mentioned sand mold for casting, the upper mold is provided with the gate or / and the feeder port which is opened upward, and is lightweight even if the vertical thickness is large.

According to the invention of claim 4, in the above-mentioned sand mold for casting, since the core has a hollow portion, distortion occurs at the time of pouring even if the external shape has different sizes depending on the parts. It is difficult to obtain a cast product with high thickness accuracy such as a pipe wall.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a sand mold for casting according to an embodiment of the present invention.

FIG. 2 is a cross-sectional plan view of an upper mold in the same sand mold for casting.

FIG. 3 is a cross-sectional plan view of a lower mold in the sand mold for casting.

FIG. 4 is a cross-sectional plan view of a core in the sand mold for casting.

FIG. 5 is a schematic vertical sectional side view showing an initial stage of manufacturing the sand mold for casting by the additive manufacturing method.

FIG. 6 is a schematic vertical sectional side view showing a final stage of manufacturing by the additive manufacturing method.

FIG. 7 is a vertical cross-sectional view at a sprue position showing a casting state by the casting sand mold.

FIG. 8 is a vertical cross-sectional view showing the casting state at a feeder port position.

FIG. 9 is a perspective view of an intake surge tank which is a casting product of the sand mold for casting.

FIG. 10 is a vertical cross-sectional view showing a state of casting by a conventional sand mold for casting.

[Explanation of symbols]

1 Upper mold (sand mold member) 10 Hollow part 2 Lower molds 20A to 20C Hollow part 3 Core 30 Hollow part 4,5 Vent holes 6A, 6B Gate 7 Feeder 8 Air vent M Laminated object L Laser beam P ₁ ~ Pn Binder hardened layer S type sand

Claims (4)

[Claims] 1. A laminate-molded article in which at least one sand mold member is formed by sequentially slicing a three-dimensional model into a number of layers in parallel as a binding hardening layer formed by irradiating a laser beam on the mold sand layer. A sand mold for casting, which comprises a hollow part which is a non-pouring space and which is provided with a vent hole which communicates with the outside of the mold from the hollow part. 2. The sand mold for casting according to claim 1, wherein the wall thickness around the hollow portion is set to 20 mm or more. 3. The casting sand mold according to claim 1 or 2, wherein the sand mold member is an upper mold having a gate or / and a feeder port opened upward. 4. The sand-shaped member is a core.
The sand mold for casting according to any one of 1.