JPS599248B2 - Dies for extrusion processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an extrusion die for extruding parts having a threaded shape.

Conventionally, extrusion processing has been applied to processing long objects with uniform cross sections such as wire, pipe, L-shape, and U-shape, and the only example of application for parts with threaded shapes is drills for drilling metal holes. It's all you can see.

In this drill, since the helix angle of the cutting teeth relative to the center axis of the drill is a gentle angle of about 32 degrees, processing can be performed using a normal extrusion method with a fixed die.

However, when it comes to parts with a larger twist angle,
The material nine bars are deformed and do not fully fill the threaded portion of the die, and due to this lack of thickness, the desired twist angle cannot be obtained.

In other words, only a gentle twist angle can be obtained.

Although this limit depends on the shape of the part and is not constant, it is approximately 34° to 35° for the drill-like shape.

As a solution to the above-mentioned problems, a method has been proposed in which the desired shape is obtained by rotating the die in accordance with the extrusion speed. This requires a synchronization mechanism for the rotational angular velocity of the die and the rotational angular velocity of the die, making the device complex and expensive as a whole.

Therefore, the present invention proposes a die that enables extrusion processing of parts with a large twist angle using a combination of an ordinary extrusion press and a fixed die.

That is, as mentioned above, when extruding a drill, extrusion processing is performed using a conventional method using a die having a shape corresponding to the shape of the drill. The reason for success lies in the small twist angle, and when extruding parts with a large twist angle using the die of this invention, the material is not transformed into the final shape all at once. The purpose is to accumulate machining in areas where deformation is not possible, and finally obtain the desired part.

Embodiments according to the present invention will be described below with reference to the drawings.

Figure 1 shows an example of a part to be extruded using the die according to the present invention, and the twist angle specified in the text is about 45° at the bottom and about 55° at the top. It is something.

2 to 4 show an embodiment according to the present invention, FIG. 2 is a plan view, FIG. 3 is an axial sectional view, and FIG. 4 is an axial sectional view at the boundary between the introduction part and the parallel part. ing.

The introduction section referred to here refers to the part of the die that gradually increases the twist angle until the required twist angle is reached, and the parallel part refers to the part of the die that completes the molding with a predetermined twist angle. ing.

Here, the symbols representing the length of each part will be explained.

Let l' be the length of the introduction region where the helix angle gradually increases at the die inlet, and l be the length of the parallel part where the helix angle is constant.

The hole diameter at the entrance of the die is D', which is the cross-sectional profile at the parallel part of the die, and the tip diameter (maximum diameter is D1).

As mentioned above, since the desired helix angle is large, the die is provided with a region l' that gradually increases the helix angle, as shown in FIG. 1) The value must be greater than or equal to the value determined by formula.

Further, the length l of the parallel portion following the introduction portion is defined by equation (2).

When these values are not satisfied, underfilling and lead errors occur, and the desired shape cannot be obtained.

The locus of the portion corresponding to the outer edge of the molded product in the die shape shown by equations (1) and (2) above is shown on the left side of FIG. 3.

In other words, the twist angle gradually increases at the introduction part,
In the parallel part, the twist angle is constant at the maximum value.

Furthermore, in Fig. 3, the relationship between the outermost diameters D' and D of the profile at the die inlet and outlet is as follows, since it is necessary to narrow down the material to prevent underfilling of the processed product. I need.

This will be explained in more detail based on FIGS. 5 to 8.

In Figures 5 and 6, the horizontal axis represents the parallel length of the die, and the index represents the ratio of the helix angle of the product to the helix angle provided on the die.
Even if the cross-sectional area of the blade that forms the thread is small and the twist angle is small, the die shape B (the cross-sectional area of the blade is narrow,
Even if the helix angle is large), the product helix angle and the die helix angle match only when the index k is 1 to 2.

When the index k is less than 1, the product torsion angle is much smaller than the die torsion angle, and when k is smaller than 2, the product torsion angle is slightly smaller than the die torsion angle.

There is a close relationship between whether the product helix angle matches the die helix angle and the presence or absence of underfill, as described below.

In other words, when the index k is less than 1, there is insufficient restraining force to fill the material up to the top of the blade, resulting in underfilling, and k
From 2, it can be seen that in the case of a dog, the die is full of material, but the center part tends to advance more and the blade part untwists at the exit of the die, resulting in a lack of material in the upper part of the blade.

This has already been proposed by the present inventor in the patent application filed in 1982-1.
As specified in the specification of No. 10373.

In Fig. 7, the horizontal axis shows the outermost diameter D'/D of the profile at the inlet and outlet, and the vertical axis shows the outermost diameter of the formed product. Failure to do so will result in insufficient thickness at the outermost diameter of the molded product.

(The parallel part of the die is k = 1.5, and the diameter of the material is slightly smaller than D'.) In Figure 8, the horizontal axis represents the length of the introduction part of the die, and the vertical axis represents the filling rate (the cross-sectional area of the molded product). (ratio to mold cross-sectional area)
and molding force, which relate to die shape B.

The filling rate reaches 1,000 when k' is 1 or more,
Since the forming force increases rapidly when k' is 2 or more, a value of 1 to 2 is suitable for the index k'.

(The area that is not filled is the upper side of the blade to be molded.

) Next, FIG. 4 shows a view from above of the axis-perpendicular cross section of the boundary between the introduction part and the parallel part explained in FIG. It has become.

Therefore, the die according to the present invention may be manufactured as one piece, but since the degree of wear is different between the introduction part and the parallel part, the introduction part and the parallel part are manufactured separately and then combined to form a predetermined die. You can also do that.

In short, if a round bar material is extruded using the die according to the present invention, a screw-shaped part with a large twist angle can be easily obtained, making a great contribution to the industry.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an extruded part according to an embodiment of the present invention, FIG. 2 is a plan view showing an embodiment of the present invention, FIG. 3 is a sectional view taken along line mm in FIG. The figure is a sectional view taken along line IV-IV in FIG. Figure 5 is a diagram showing the experimental values of the relationship between the parallel length of the die and the product helix angle, Figure 6 is a diagram showing a part of Figure 5 enlarged, and Figure 7 is the profile exit diameter ratio. FIG. 8 is a diagram showing experimental values of the relationship between product diameter, and FIG. 8 is a diagram showing experimental values of the relationship between die introduction length, product filling degree, and molding pressure.

Claims (1)

[Scope of Claims] 1. A die used for extrusion T of a screw-shaped part with a large helix angle, which has an introduction part whose helix angle gradually increases and reaches the required helix angle, and which has the required helix angle and is capable of extrusion processing. and a parallel part in which a complete profile is formed to complete the above, and the length l' of the introduction part and the length l of the parallel part, where D: the maximum diameter of the profile part in the parallel part d: the profile in the parallel part The extrusion is characterized in that the diameter is equal to or larger than the value specified by the root diameter of the introduction part, and the relationship between the maximum diameter D' of the introduction part and the maximum diameter D of the profile part in the parallel part satisfies the following. Processing dies. 2. In dies used for extrusion processing of screw-shaped parts with a large helix angle, there is a die for the introduction part that has an introduction part whose helix angle gradually increases until it reaches the required helix angle, and a die that has the required helix angle and is capable of extrusion processing. A parallel part die having a parallel part with a complete profile to be completed is integrally joined together on the same axis, and the length l' of the introduction part and the length 4 of the parallel part are D: The maximum diameter d of the profile part in the parallel part shall be greater than or equal to the value specified by the root diameter of the profile part in the parallel part, and the maximum diameter D' of the introduction part and the maximum diameter D of the profile part in the parallel part. An extrusion die characterized in that the relationship satisfies the following.