JP2013166179A - Molding method for sand mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for a sand mold, which can rapidly mold facing sand to a necessary thickness by hand, without requiring a special skill.SOLUTION: In a molding method for a sand mold, facing sand 3 and back sand 4 are sequentially put with respect to a model 2. The facing sand 3 is put under the condition that a plurality of markers 10 of marks of thickness of the facing sand 3 are installed on the model 2, and after putting of the facing sand 3 is finished, the plurality of markers 10 are removed. Each of the markers 10 includes: a needle-shaped tip 12 stuck to the model 2; a column 11 connected to the tip 12; and a blade 15 protruding in a direction crossing the column 11. A connection part of the tip 12 and the column 11 preferably is made as a step 14 such that the column 11 has a larger dimension than the tip 12.

Description

  The present invention relates to a method for forming a sand mold used for casting.

In the sand mold making method, as shown in FIG. 6, the skin sand 3 and the back sand 4 are put in order in the model 2 arranged inside the casting frame 1 and the base 5, and then dried and cured. Then, the model 2 is removed, and a sand mold is completed. Casting is obtained by casting the molten metal into the gap from which the model has been removed and solidifying it.
As the skin sand 3, sand having a particle size smaller than that of the back sand 4 is used in order to prevent seizure on the casting. When the thickness of the skin sand 3 is too thin, the burn-in preventing effect is reduced. On the other hand, if the skin sand 3 is too thick, the air permeability is lowered, so that it is difficult for gas generated during casting to escape to the outside through the skin sand 3 and the back sand 4. This gas is generated by the burning of the resin binder contained in the foundry sand and the entrainment accompanying the fluctuation of the molten metal surface. Then, a part of this gas stays in the casting, and as a result, a surface defect due to the gas defect occurs in the casting. Thus, it is important to manage the thickness of skin sand.

Sand mold molding is mainly manual labor, but in the case of a sand mold of a casting having a complicated shape (model), a high level of skill is required for molding while adjusting the thickness of the skin sand 3. When self-hardening sand is used as the foundry sand, it is not easy to accurately adjust the thickness of the skin sand 3 because there is a restriction that molding must be completed in about 1 to 2 hours.
Under such circumstances, Patent Document 1 proposes a method for quantitatively and automatically introducing skin sand and back sand in order to put the skin sand into a uniform thickness.

JP 2003-136194 A

However, although Patent Document 1 is effective for a model having a flat surface, a sand skin layer and a back sand layer having a uniform thickness cannot be obtained for a model having irregularities (or undulations). This is because the casting sand is centrifugally projected.
SUMMARY OF THE INVENTION An object of the present invention is to provide a sand mold making method that can quickly handle sand skin to a required thickness without requiring special skills.

The present invention made for this purpose is a sand mold forming method in which skin sand and back sand can be put in order with respect to the model, and a plurality of markers serving as markers for skin sand thickness are installed on the model. It is characterized in that the skin sand is filled in the state, and the plurality of markers are removed after the filling of the skin sand is finished.
According to the molding method of the present invention, since the sand is put in a state where a plurality of markers serving as thickness marks are installed on the model, the sand skin can be quickly obtained to a necessary thickness even without special skills. Can be managed.

The marker according to the present invention includes a needle-like tip pierced by a model, a support column connected to the tip, and a marker body protruding in a direction crossing the support column, and the connecting portion between the tip and the support column has a large size of the support column It is preferable to be a step.
By making the tip into a needle that pierces the model, it is only necessary to manually insert and remove the marker from the model and remove the marker from the model, so the burden of molding work can be minimized. .
Moreover, the depth at which the tip of the marker pierces the model can be regulated by making the connecting portion between the tip and the column a step having a large size of the column. By doing so, the distance from the model surface to the marker body can be made the same for any marker.

  According to the molding method of the present invention, after a plurality of markers are removed, when voids remain in the portion of the skin sand where the markers existed, it is preferable to fill the voids with separately prepared skin sand.

  According to the molding method of the present invention, since the sand is put in a state where a plurality of markers serving as thickness markers are installed on the model, the sand skin can be quickly obtained to a necessary thickness even without special skills. It can be managed.

It is a figure which shows typically the procedure of the molding method by this embodiment, (a) shows a mode that the marker was stabbed into the model, (b) after skin sand was put, (c) is a marker. Shown after extraction. It is the elements on larger scale of each state of (a), (b), (c) of FIG. It is a front view which shows the marker used by this embodiment. It is a figure which shows two examples of how to stab a marker to the corner part vicinity of a model. The modification of this embodiment is shown, (a) shows the example which hangs a rope to the adjacent marker installed in the model, (b) has shown the example which connected the marker with the rope before stabbed into a model. . It is sectional drawing which shows the sand type | mold with skin sand and back sand.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
In the present embodiment, as shown in FIG. 1, a sand mold in which skin sand 3 and back sand 4 are sequentially formed on a model 2 placed in a casting frame 1 formed on a base 5 by manual handling. Relates to the molding method. However, the back sand 4 may be thrown into the back sand 4 using mechanical means and then handed over. This molding method includes a marker installation step (FIGS. 1A and 2A), a skin sand layer formation step (FIGS. 1B and 2B), and a marker removal step (FIG. 1C). ), FIG. 2 (c)) and a back sand layer forming step and a mold surface shaping step, which are not shown, and characterized in that the skin sand 3 is formed on the model 2 on which the marker 10 has been previously installed. It is.
Known elements can be widely applied to the model 2, the skin sand 3, and the back sand 4, but polystyrene foam can be used as the model 2, and self-hardening foundry sand can be used as the skin sand 3 and the back sand 4. Regardless of the type of skin sand 3 and back sand 4 used in this embodiment, known self-hardening foundry sand can be widely used. Similarly, a wide variety of known resins can be used for the kind of binder. Furthermore, as the material of the model 2, other types such as wood can be widely used.

[Marker installation process]
In this step, the marker 10 is placed on the model 2 arranged in the casting frame 1 formed on the base 5. The marker 10 serves as a mark for the thickness for handling the skin sand 3 in the skin sand layer forming process which is the next process.
The markers 10 are installed at a plurality of locations on the model 2. Since the marker 10 is intended to mark the thickness of the skin sand, the orientation, number, and position of the marker 10 are set so that this purpose can be achieved. The marker 10 is erected along the direction in which the skin sand 3 is inserted from the surface of the model 2. That is, if the surface of the model 2 is along the horizontal direction, the marker 10 is installed along the vertical direction, and if the surface of the model 2 is along the vertical direction, the marker 10 is installed along the horizontal direction.
When the interval between the adjacent markers 10 is too wide, it becomes difficult to carry out the maintenance while maintaining the thickness of the skin sand at the thickness indicated by the marker 10 at the central portion of the interval far from the marker 10. On the other hand, when the interval between the adjacent markers 10 is narrow, the difficulty of maintaining the thickness is eliminated, but the number of markers 10 to be installed increases, so that the labor for installing the markers 10 and the markers later The trouble of removing 10 increases. The marker 10 is installed in consideration of this point. Considering the ease of work, it is preferable to install the markers 10 at equal intervals, but this does not limit the present invention.

The marker 10 in this embodiment is provided with the column-shaped support | pillar 11, the blade | wing 15, and the handle 16 as shown in FIG.
The support 11 is formed with a needle-like tip 12 for fixing the marker 10 to the model 2. Since the diameter of the column 11 is larger than the diameter of the tip 12, the step 14 is formed at the connecting portion between the tip 12 and the column 11. The step 14 has a function of restricting the marker 10 from being inserted into the model 2 more than necessary when the marker 10 is stabbed into the model 2 and the tip 12 is stabbed against the surface of the model 2. Fulfill.
The blade (marker body) 15 is provided at a position away from the step 14 by a predetermined distance. In the present embodiment, a pair of blades 15 are provided so as to protrude perpendicularly to the support column 11 in opposite directions. The distance from the step 14 is determined so that the blade 15 becomes a mark of the required thickness of the skin sand 3 when the marker 10 is installed on the model 2.
When installing the marker 10 on the model 2 or when removing the skin sand 3 after forming, the operator grasps the handle 16 to work.
Although the manufacturing method of the marker 10 is not ask | required, it can manufacture, for example as a resin integral molding by injection molding. Moreover, the marker 10 can also be produced by bending the wire.
In addition, since the thickness t (FIG. 2) of the skin sand 3 is usually constant, it is sufficient to prepare a necessary number of markers 10 having the same shape and size, but the thickness of the skin sand 3 differs depending on the part. When doing so, the marker 10 according to it is prepared.

  In order to stab the marker 10 near the corner portion of the model 2, a pair of blades 15 as shown in FIG. 4B, in addition to the marker 10 being stabbed perpendicularly to the surface of the model 2 as shown in FIG. May be provided so as to be orthogonal to each other, and the marker 10 may be tilted by 45 degrees on the surface of the model 2 and pierced in the corner C. At this time, as shown in FIG. 4 (b), the blade 15 is desirably arranged with an angle with respect to the support 11 according to the angle of inclination.

[Skin layer formation process]
If the required number of markers 10 is installed in a required location, the skin sand 3 prepared separately is prepared. The skin sand 3 is laminated in order from the side close to the model 2, but when the laminated thickness approaches the height of the blade 15 of the marker 10, the operator is concerned about the height of the blade 15. Manipulate skin sand 3. If the skin sand 3 is laminated up to the height of the blade 15 over the entire area of the model 2, the handling of the skin sand 3 is finished.

  After completion of the handling, the marker 10 is pulled out from the model 2 and the skin sand 3 and removed (FIG. 1 (c), FIG. 2 (c)). The self-hardening skin sand 3 is partially cured, but the marker 10 can be easily removed as long as a considerable time has not elapsed since the completion of the handling. On the other hand, since the skin sand 3 is partially cured, there is no fear that the skin sand 3 will collapse due to the withdrawal of the marker 10 unless extremely rough work is performed.

  When the marker 10 is removed, the portion of the skin sand 3 from which the support 11 has been pulled out remains as a gap P (left side of FIG. 2 (c)). Since this gap P has reached model 2, if it is left as it is, molten metal may be poured during casting. Therefore, the void P is closed by filling the void P with foundry sand (skin sand) S. The method of closing the gap by filling the skin sand 3 is the most preferable mode, but is not the only method in the present invention. A material having characteristics such as a melting point that can withstand casting can be used to close the gap. This material does not need to be granular, and the gap can be closed by filling the gap with a member having the same shape and size as the column 11 except for the needle-shaped tip portion 12.

[Back sand layer formation process]
When all the voids P are closed, the back sand 4 is put on the skin sand 3. Since this work should just follow what was performed conventionally, the concrete description here is omitted.

[Mold surface shaping process]
When the formation of the back sand 4 is completed, the base 5 and the model 2 are removed in order. Then, the mold surface that is in contact with the model 2 of the skin sand 3 is exposed. The mold surface is in contact with the molten metal (casting) during casting and affects the surface condition of the casting surface. Therefore, the mold surface is shaped. Furthermore, a sand mold is completed by applying a coating mold to the shaped mold surface.
Here, since the tip portion 12 of the marker 10 has pierced the model 2, a minute gap remains in the model 2. There is a risk of being filled with. Therefore, when the model 2 is removed, the foundry sand filling the voids of the model 2 protrudes from the cast surface, but is removed by shaping the mold surface.

As described above, according to the mold making method according to the present embodiment, the marker 10 indicating the thickness of the skin sand 3 is placed on the model 2, so that the skin sand 3 can be accurately put into the necessary thickness t. be able to.
Further, since the marker 10 is provided with a step 14 between the support 11 and the tip portion 12, when the tip portion 12 is stabbed into the model 2, the step 14 strikes the surface of the model 2 and deepens further. Is prevented. Therefore, if the marker 10 having the same shape and size is used, the distance from the surface of the model 2 to the blade 15, in other words, the thickness t of the skin sand 3 is constant regardless of the location of the marker 10 on the model 2. Can be.
Furthermore, since the tip end portion 12 has a needle shape, the marker 10 is very easy to install and remove from the model 2, so that an increase in the burden of molding work can be minimized.

  In addition, in the said embodiment, although the marker 10 was shown as a preferable form, as long as it becomes a mark of the thickness of the skin sand 3, the form will not be ask | required. In particular, instead of the blade 15, a ring-shaped rib is provided at the same position where the blade 15 is provided, or a color different from that of the support column is used as a mark.

Further, in the present embodiment, a plurality of markers 10 are installed on the model 2, but as shown in FIG. 5A, for example, the rope 17 can be hung over the height of the blade 15 of the adjacent marker 10. Then, since this rope 17 also becomes a mark of the thickness of the skin sand 3, the thickness control between the markers 10 becomes more reliable, and the number of markers 10 to be installed can be reduced.
In this case, as shown in FIG. 5B, the markers 10 can be connected with a rope 17 from the beginning. The rope 17 connects the markers 10 with the same length as the interval at which the adjacent markers 10 are installed. Then, if the rope 10 is stretched without slack and the marker 10 is installed on the model 2, the interval between the adjacent markers 10 can be accurately maintained, and the labor for installing the marker 10 can be saved while paying attention to the installation interval each time. .
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.
For example, the shape of the model 2 shown here is merely an example, and it goes without saying that the present invention can be applied to the model 2 having other shapes.
The same applies to the marker 10, and members that serve as marks for the thickness of the skin sand 3 can be widely applied to the present invention.

DESCRIPTION OF SYMBOLS 1 Cast frame 2 Model 3 Skin sand layer 4 Back sand layer 5 Base 10 Marker 11 Support | pillar 12 Front-end | tip part 14 Step 15 Blade | blade 16 Handle 17 Rope

Claims (4)

A sand mold making method that puts sand and back sand in order against the model,
In a state where a plurality of markers serving as marks of the thickness of the skin sand are installed on the model, the skin sand is put in,
After the loading of the skin sand is completed, the plurality of markers are removed.
A sand mold making method characterized by the above. The marker is
A needle-like tip pierced by the model, a column connected to the tip, and a marker body protruding in a direction intersecting the column,
The connecting portion between the tip and the column is a step having a large size of the column.
The sand mold making method according to claim 1. After removing a plurality of the markers, the void remaining in the skin sand is filled with separately prepared skin sand,
The sand mold making method according to claim 1 or 2. Connecting at least two of the markers with a rope,
The sand mold making method according to any one of claims 1 to 3.

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