JPS6326233A - Forming method for casting mold - Google Patents

Abstract

PURPOSE:To obviate the contact of cavity edges with each other and the consequent failure thereof at the time of mating by forming projecting parts to the superposed surface of a cope or drag except the cavity edge thereof to form a slight spacing between the cope and the drag at the time of forming the cope or drag. CONSTITUTION:A metallic mold 6 provided with a pattern 6a of a cam shaft is disposed between a cope box 7 and a drag box 8 and after a molding flask 7a is formed, molding sand 9 is forcibly fed from above into the drag box 8 to form the drag 10. The molding flask 7a is then turned upside down and air vent plugs 11 ... on the surface of the mold 6 are sunk in the sand down to the prescribed depth; thereafter, the molding sand 9 is force-fed into the cope box 7 to form the cope 12. The mold 6 is removed in succession and again the cope 12 is superposed on the drag 10. Since the projecting parts 14 ...are formed on the bottom surface of the cope 12, the slight spacing 16 is formed between the superposed surfaces of the cope 12 and the drag 10 when the cope box 7 and the drag box 8 are removed. The contact of the cavity edge parts with each other at the time of mating and the consequent failure thereof are thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a sand mold molding method for casting, for example, a camshaft in a vehicle engine.

(Prior Art) Most of conventional camshafts and the like of vehicle engines are cast using sand molds, especially at the time of prototyping.

Hereinafter, the structure of a sand mold used for conventional casting of camshafts will be explained with reference to FIGS. 5 to 7.

In FIG. 5, 1 is a sand mold. This sand mold 1 is formed of a lower mold 2 and an upper mold 3 superposed on the upper part of this lower mold 2.

A cavity 4 is provided between the upper mold 3 and the lower mold 2 to form the outline of the camshaft.

As shown in FIG. 6, this cavity 4 is formed so that a plurality of camshafts can be cast at once. The upper mold 3 has a sprue (not shown).

The lower mold 2 is provided with a runner, etc. (not shown), so that molten metal can be poured into the cavity 4.

In the sand mold 1 as described above, a model is placed in a mold frame (not shown) and molding sand 1a is filled, after which the upper mold 3 and the lower mold 2 are separated and the model is extracted to form the cavity 4.

It has a step of overlapping the upper mold 3 and the lower mold 2 again.

When performing the above-mentioned process, the cavity 4 may be damaged as shown in FIG. 7. That is, when the upper mold 3 and the lower mold 2 are overlapped, the edges 5 of the cavity 4 may come into contact and be damaged.

Then, the edge portions 5 which are damaged and collapsed remain inside the cavity 4, and since the metal is poured in this state, a camshaft with no product value may be cast.

(Problems to be Solved by the Invention) As described above, when the upper and lower molds of the conventional sand mold are overlapped, the mutually contacting edges of the cavities collide and collapse, and the mold is cast as is.

There is a disadvantage that the defective rate increases.

This invention was made in view of the above circumstances.

This is a mold making method that aims to reduce the defective rate of products by preventing the edges from colliding with each other when the upper and lower molds are overlapped, thereby preventing damage to the cavity.

[Structure of the invention]

(Means and effects for solving the problem) This invention has the following features:
The mold with the model installed inside is filled with foundry sand, and then
The model is extracted from the mold to form a cavity. Then, when molding the upper mold or the lower mold, a convex part is formed on the overlapping surface excluding the edge of the cavity, and a minute gap is formed between the upper mold and the lower mold. The present invention provides a mold making method that prevents the edges from coming into contact with each other when the molds are overlapped, thereby preventing damage to the cavity.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

In FIG. 1, 6 is a mold, and a model 6a having the outline of a camshaft is provided in the center of the mold. An upper frame 7 and a lower frame 8 are arranged at the upper and lower parts of the mold 6 to form a mold frame 7a. At this time, the upper frame 7 is located at the lower part of the mold 6, and the lower frame 8 is located at the upper part.

Then, molding sand 9 is forcibly fed into the lower frame 8 from above using compressed air to form a lower mold 10 as shown in FIG. 2.

Next, the upper frame 7 and the lower frame 8 containing the mold 6 are turned upside down and the third
The positional relationship is as shown in the figure. At this time.

An upper frame 7 having a certain distance from the model part 6a of the mold 6
The air vent plug 11 provided on the surface of the mold 6 facing the side is sunk approximately 0.5 mm.

This air vent plug 11 is for removing air, etc. when the molding sand 9 is forcibly fed toward the mold 6 by compressed air. The structure has a slit that allows only air to pass through without passing through the molding sand 9, and is embedded in the surface of the mold 6.

By force-feeding the molding sand 9 from above into the upper frame 7 as described above, the upper mold 12 is formed into a state as shown in FIG. 3. At this time, since the air vent plug 11 is sunk approximately 0.5 mm into the mold 6, a plurality of air vent plugs protrude approximately 0.5 mm from the lower surface of the upper mold 12, that is, the surface in contact with the lower mold 10. Convex portions 14... are formed.

Thereafter, the mold 6 is removed by separating the upper mold 12 and the lower mold 10, and the upper mold 12 is again placed on top of the lower mold 10 to form a cavity 13, and the upper frame 7 and the lower frame 8 is removed and the state shown in FIG. 4 is obtained.

The above-mentioned upper mold 12 and lower mold 10 are formed by the mold making method explained above.
Since the convex portions 14 are provided therebetween, a minute gap 16 is formed between the overlapping surfaces of the upper mold 12 and the lower mold 10. Therefore, the edge 1 in the cavity 13
5 faced each other without contact.

It can prevent damage to the mold due to collision.

This makes it possible to manufacture stable molds.

Productivity can be significantly improved compared to conventional mold making methods.

Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, an air vent plug is used to form a convex part on the upper mold, but the present invention is not limited to this. Any material that forms a minute gap between the overlapping surfaces of the mold and the lower mold may be used.

〔Effect of the invention〕

As explained above, according to the present invention, since the convex portion is provided between the upper mold and the lower mold, a minute gap is formed between the overlapping surfaces of the upper mold and the lower mold, and the edge of the cavity There is no risk of damage to the mold as there is no contact between the two. Therefore, the product defect rate can be significantly reduced.

Further, since the convex portion is molded simultaneously with the molding of the upper mold or the lower mold, the above-mentioned effects can be obtained without increasing the number of man-hours required during conventional mold manufacturing.

[Brief explanation of the drawing]

Figures 1 to 4 are cross-sectional views showing an embodiment of the mold making process of the present invention, Figures 5 to 7 are conventional examples, Figure 5 is a side view of the sand mold, and Figure 6 is a side view of the sand mold. V in Figure 5
A cross-sectional view of the l-VI line portion, Figure 7 is the ■- in Figure 5.
■It is a sectional view of the line part. 6a... Model, 7a... Formwork, 9... Foundry sand, 1
0...Lower mold, 12...Upper mold, 13...Cavity, 14...Convex portion, 15...Edge, 16...Minute gap. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Cause Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In the mold manufacturing method in which a model is placed in the main frame, the mold is filled with molding sand, and then the mold is pulled out to form a cavity, the edge of the cavity is A mold casting method characterized by forming a convex part on the overlapped surface excluding the part, and forming a minute gap between the upper mold and the lower mold.