JPH03161145A - Method and apparatus for vibration for packing molding sand - Google Patents

Abstract

PURPOSE:To enable molding sand packing having high density by selecting phase difference at initial stage and ratio of numbers of vibration in a vibrator of vertical and horizontal direction vibrations and uniformly packing the molding sand in a flask. CONSTITUTION:Lissajous's figure shows various shapes with the ratio of vibrations and phase difference in two harmonic vibrations vibrating mutually at the right angle direction. In this Lissajous's figure, the vibration locus where the vibration is applied to the whole direction and is considered to be the most available for packing the molding sand, is selected. Synthetic condition at this time, is 2:1 the ratio of numbers of vibration and 90 deg. the phase difference at the initial stage. Further, by adjusting ratio of amplitudes, this can be reformed into the ideal shape. A vibrating table having structure fitting a vibrator 3 applying the vibration toward vertical direction to a vibrating table 2 hung with a spring 1 and a vibrator 4 applying the vibration toward two directions at the right angle of the vertical and horizontal directions, is used. By this method, the packing of molding sand into side hole and recessed part as turning a bowl over in a pattern for self-curing sand molding and lost foam casting can be easily executed at high density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a vibrating table for use in disappearing model casting or self-hardening sand molding.
The present invention relates to a vibration method and a vibration device for filling molding sand in which an ideal vibration trajectory of molding sand is obtained by adjusting the horizontal frequency ratio.

[Conventional technology]

The most attractive feature of the vanishing model casting method, which has become increasingly popular in recent years, compared to the traditional casting method is that it uses dry sand, and the molding process is extremely simple compared to the traditional cavity casting method. However, in this vanishing model casting method, the foam model is buried in the molding sand in the center of the flask without being deformed, and the generated gas is allowed to escape sufficiently without causing any wall movement of the foam model when molten metal is poured. It is necessary to fill the gap with molding sand.

For this reason, the molding sand is filled using a vibrating table as shown in FIG. Specifically, there are two types of vibration tables: one is a vibration table 2 suspended from a spring 1, and the other is a vibration table with a vibrator 3 attached thereto for applying vibration in the vertical direction; It is often used. In this case, for a single-axis vertical vibration table,
Since the movement of molding sand in the horizontal direction is small, it is impossible to fill the horizontal holes of a foam model with molding sand, and generally a three-axis simultaneous vibration device that vibrates in two directions, vertical and horizontal, is used. It is what is used.

[Problem to be solved by the invention]

However, in such devices, it is necessary to completely fill the surrounding area with molding sand without deforming the foam model, so a three-axis simultaneous vibration device is often used. Even if the molding sand is accurately buried in the molding sand, the filling of the molding sand into the horizontal holes and various deformed concave surfaces in the model will be uneven, resulting in casting defects, and furthermore, the molding will not be able to be cast without deforming the foamed model. Even if it is buried in sand, the walls of the foam model will move when molten metal is poured, making it impossible to obtain a cast product with uniform precision. For example, as shown in Figures 2 and 3, two vibrations that are perpendicular to each other and have the same frequency, X = Sia
ωt, Y=S+m( (IJ t+θ) This is a typical example of the vibration trajectory that occurs when combining
2XYCOSθ=Sia”θtonari, ■)θ=π/2,
When 3π/2, X2 + Y2 = 1 ■) When θ=0, 2π, x-y=o ■) When θ=π, x+y=o ■) When θ=π/4,..., X2-, / This is also the vibration locus of the foundry sand when it is vibrated by these vibrators with −2XY+Y2=1. It is clear that when the initial phase difference φ is fixed to 01π and 2π, there is no effect of simultaneous excitation in two axes. For this reason, vertical
There are points that need to be improved, such as searching for an optimal vibration excitation method by variously converting the horizontal vibration acceleration.

[Means to solve the problem]

The present invention was created in view of the current situation, and
In order to reduce the stress applied to the foam model when filling with foundry sand, the initial phase difference of the vibrator and the frequency ratio of vertical and horizontal vibrations were adjusted to obtain a vibration trajectory that moves the filling sand in all directions with little force. The aim is to achieve this purpose by adjusting.

[For production]

The curve shown in FIG. 4 is generally called a Lissajous figure, and takes on various shapes depending on the vibration ratio and phase difference between two harmonic vibrations vibrating at right angles to each other.

From this Lissajous figure, a vibration locus in which vibration is applied in all directions and is considered to be most useful for filling with foundry sand is selected and shown in FIG. The synthesis condition at this time is a frequency ratio of 2
:1, initial phase difference is 90°. Furthermore, the shape can be improved to an ideal shape by adjusting the amplitude ratio.

〔Example〕

To explain one embodiment of the present invention, since the amount of vibration and the dynamic structure of the sand grain layer of the flask are considered to be the evaluation value of the fluid filling ability of the foundry sand, the relationship with the excitation force of the vibration table, etc. As shown in Figure 6, the influence of frequency on the relationship between the excitation force of the vibration table and the amount of vibration of objects buried in sand is If the condition is gentle, the amount of response to the excitation force is not sufficient.

In addition, the convection-like flow becomes the most intense and the amount of expansion becomes the maximum.2. An abnormality was observed near OG. However, from 0.5G, which is the starting point of settling of the sand grain layer, to 1.0 G, which is the starting point of flow.
Up to G, the respective vibration amounts were the closest, and the response situation was good. From the above results, the practical excitation force range (0
．． 8 to 1.5G), it is considered that approximately the same vibration is applied to the sand grain layer from the vibration table. Therefore, it is considered that the vibration locus caused by the vibration table and the vibration locus of the filling sand are almost the same within the practical excitation force range, and therefore it is determined that the movement of the filling sand can be adjusted by the movement of the vibration table. For this reason, when the vibration table is vibrated under the conditions shown in Figure 5, with a vibration ratio of 2:1 and an initial phase difference of 90°, the vibration is uniaxial (up and down) as shown in Figure 7.
Compared to the excitation, the final amount of sand settling was high with a short excitation time.

〔Effect of the invention〕

According to the present invention, by selecting the initial phase difference and frequency ratio of vertical vibration and vibration in two horizontal directions, it is possible to obtain an ideal vibration trajectory for sand filling. It is extremely useful because it allows easy filling of molding sand into side holes and recesses where the bowl is turned upside down in models for molding and investment casting, making it possible to fill the sand with high density.

[Brief explanation of the drawing]

Figure 1 is a schematic structural diagram of a conventional vibration table, Figure 2 is a diagram of the influence of phase difference on the vibration trajectory when horizontal and vertical vibrations are combined, and Figure 3 is due to biaxial vibration. Figure 4 shows unfavorable vibration trajectories for a vibration table; Figure 4 shows various phase differences and frequency ratios; Figure 5 shows preferred vibration trajectories for a vibration table with two-axis vibration; Figure 6
The figure shows the amount of vibration between the vibration table and the object buried in the sand, and FIG. 7 shows the relationship between the vibration time and the amount of sand settling. Ikenagacho Tokai ゛l゛' Fig. 1 Fig. 2 I2l Fig. 3 Figure 5 Figure 7 Excitation time, min Relationship between salting time and sand settlement Figure 6 Number of castles, Ilz Raccoon equipment shape: 5Qx50x5 City Acrylic Position: 100 order from the sand bottom

Claims (2)

[Claims] (1) A vibration method for filling molding sand, characterized in that the molding sand in the flask is uniformly filled by selecting the initial phase difference and frequency ratio of the vibrators in vertical vibration and two horizontal directions, respectively. . (2) A vibration device for filling foundry sand, characterized in that an optimum vibration trajectory can be obtained by selecting the initial phase difference and frequency ratio of the vibrators in vertical vibration and two horizontal directions.