JPH05212497A - Method for improving flatness of mold - Google Patents

Abstract

PURPOSE:To prevent the generation of mold breakage at the corner part of a cavity in a mold and casting flash, to reduce the man-hours of the finishing work in the casting and to improve the casting yield and the flatness of the parting surface of the molds in order to reduce the cost. CONSTITUTION:A recessed part 3 having (t)=0.5-3mm and (h)=10-40mm ((t) and (h) are shown in the figure) is formed at the end part of the molding flask 4, and after the end part forming the recessed part 3 is abutted on the upper surface of the pattern base plate 2 and placed, the molding sand 5 is filled up and the molding work, such as mold clamping, is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the flatness of a mold-matching surface (a parting surface).

[0002]

2. Description of the Related Art Conventionally, a casting mold is mounted on a table of a molding machine by mounting a model surface plate on which either an upper mold forming model or a lower mold forming model is arranged. After placing the frame and charging the molding sand into the molding frame, the molding sand is compressed by the squeeze head of the molding machine and the mold is clamped, and then the model is extracted. After making the molds with and, the lower mold is placed with the parting surface facing upwards, and the upper mold is covered with the parting surface facing downwards.

However, the flatness of the parting surfaces of the upper mold and the lower mold after molding is caused by springback of the molding sand compressed by mold clamping in addition to insufficient rigidity of equipment such as model surface plate and casting frame. Is not good, and the central portion is usually about 0.5 to 1.2 mm higher than the peripheral portion. Thus, the flatness of the parting surface is not good, and when the upper mold and the lower mold, which are convex, are combined with each other, the cavity 8 formed by the upper mold 6 and the lower mold 7 as shown in FIG. Out of the perimeter of the parting plane, it is hit by matching the mold (upper mold 6 and lower mold
The corner portion 6a of the upper die 6 or the corner portion 7a of the lower die 7 or both of the corner portions 6a, 7a
The mold is broken.

When pouring into the cavity 8 of the mold where the mold has broken, flash occurs at this portion, and a lot of man-hours are required for casting finish such as grinding removal of the flash. In order to prevent the occurrence of flashing due to mold breakage around the cavity 8 on the parting plane, conventionally, as shown in FIG. Was attached. Although not shown, this R was formed by mounting a model on a model surface plate, then attaching a small-diameter R to the root of the model with resin or the like, and molding this.

[0005]

However, in the case where the corners on the parting surface of the cavity are rounded as described above, the mold breakage at the time of mold matching is reduced and the occurrence of a large flash is reduced. Although there is an effect, since the R portion of the mold is formed as a protruding portion in the cast product after pouring, a large number of casting finishing steps are required to grind and remove this portion. The present invention aims to provide a method for improving the flatness of the mold parting surface in order to solve the above conventional problems and prevent or reduce the mold breakage of the parting surface corner of the mold cavity. To do.

[0006]

The present invention has been made as a result of various experiments in order to achieve the above-mentioned object, and its constitution is such that a recess having a depth of 0.5 to 3 mm is formed on the inner wall surface near the end. A casting frame formed from 10 to 40 mm from the end is placed on the upper surface of the model surface plate on which the model is arranged, with the end having the recess formed in contact therewith, and casting sand is placed in the casting frame. It is characterized in that molding is performed after filling.

[0007]

When molding is performed after the mold clamping is completed and the pressing force for clamping the mold is removed, the compressed molding sand does not spring back to the parting surface side, and the recess formed in the molding frame. Spring back to the side. Therefore, the parting plane can obtain a considerably high degree of flatness.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is a cross-sectional view showing a state during molding of an upper mold, FIG.
[Fig. 3] is a perspective view of a model in the example.

In FIG. 1, reference numeral 1 is a model for molding an upper mold,
It is arranged at a predetermined position on the model surface plate 2. Reference numeral 3 denotes a recess formed on the entire inner wall surface in the vicinity of the end portion (lower end portion in FIG. 1) of the upper mold casting frame 4. Then, in molding the upper mold, the end on the side where the recess 3 is formed is brought into contact with the model surface plate 2 as shown in FIG. The molding sand 5 is charged from a sand hopper (not shown) provided in the upper part of the mold, and the molding sand 5 is surrounded by the molding sand 4 to surround the model 1.
Filled inside. The model surface plate 2 on which the model 1 is arranged is previously mounted on the table (not shown) of the molding machine.

When the filling of the molding sand 5 is completed, the molding sand is compressed by a squeeze head (not shown) of a molding machine, and after the mold is clamped, the mold is removed to complete the molding of the upper mold. Although the molding sand 5 compressed by die cutting springs back, it does not swell as in the conventional case on the parting surface, that is, the lower surface side in FIG. 1 as in FIG. I was able to improve the degree.

According to the above method, the dimensions shown in FIG. 2 (unit: m
m), using the model 1 of shape, and size 450 × 40
Depth t = 1.5 mm, width h = 30 mm from the end on the entire inner wall surface around the end of the casting frame 4 of 0 × 240 H (unit: mm)
Molding was performed by using the one in which the concave portion 3 was formed, and the flatness of the parting surface after die cutting was measured. The filling molding sand 5 has a water content of 3.0 to 3.3% and CB (compactivity) 35 to 4
It was 0%, and the molding surface pressure (MPa) was 1.1. In the same manner, molding was performed using the conventional casting frame 4 in which the recess 3 was not formed, and the flatness of the parting surface was measured.

The flatness was measured using an optical displacement sensor (accuracy ± 20 μm ± 1% of measured value). As a result, the flatness of the parting surface of the casting mold 4 in which the recess 3 is not formed has the maximum height h =
Although the convex shape is 0.40 mm, the method according to the present invention using the casting frame 4 in which the concave portion 3 is formed is a convex shape having a maximum height h = 0.05 mm as shown in FIG. The flatness was greatly improved in comparison.

As a result of various experiments, when t = 0.5 mm or more and h = 10 mm or more, the effect of absorbing springback and improving the flatness appears, but t = 3 mm,
It was found that when h = 40 mm is exceeded, the mold clamping in this portion is significantly deteriorated. Therefore, in the present invention, t =
It was set to 0.5 to 3 mm and h = 10 to 40 mm. Further, although the present embodiment describes the upper mold making, it goes without saying that the present invention is not limited to only the upper mold making, and the lower mold making has the same effect. .. Further, the concave portion 3 does not have to be formed on the entire inner wall surface of the casting frame 4, and may be formed only on a required portion of the inner wall surface depending on the shape of the model 1.

[0014]

As described above, according to the present invention, it is possible to remarkably improve the flatness of the parting surface of the mold, and the occurrence of mold breakage or flash in the corner part around the parting surface of the cavity of the mold. And the number of man-hours required for casting and finishing are reduced, the yield of casting is improved, and the cost of castings is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state during molding of an upper mold showing an embodiment of the present invention.

FIG. 2 is a perspective view of a model according to the embodiment.

FIG. 3 is a cross-sectional view of a mold showing a state where a conventional method is used for molding and matching the molds.

FIG. 4 is an enlarged cross-sectional view of a main part in a state where molds having corners with Rs are matched.

FIG. 5 is a view showing the flatness of the mold before improving the shape of the flask.

FIG. 6 is a view showing the flatness of the mold after improving the shape of the flask.

[Explanation of symbols]

 1 Model 2 Model surface plate 3 Recess 4 Mold frame 5 Foundry sand 6 Upper mold 7 Lower mold

Claims (1)

[Claims] 1. A depth of 0.5 to 3 m on the inner wall surface near the end.
A casting frame having a m-shaped concave portion formed from the end portion to 10 to 40 mm is placed on the upper surface of a model surface plate on which a model is arranged, with the end portion having the concave portion abutted thereon. A method for improving the flatness of a mold, which comprises performing molding after filling the molding sand with the molding sand.