JPH08225809A - Extrusion of plastic mixture - Google Patents

Abstract

PURPOSE: To provide an extruded product with excellent straightness in an extruding method in which a material to be extruded is introduced from the side. CONSTITUTION: In an extruding method in which a material to be extruded is introduced from the side to a duct part of the upstream side of extrusion dies 5, the aspect ratio of the duct is regulated to >=3. In the extruding method in which a rotatable mandrel 3b is provided in the dies or the duct, the mandrel 3b is rotatably supported by a bearing 6 provided in the material to be extruded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for extrusion-molding a plastic kneaded body, and particularly for introducing a kneaded body into a duct portion upstream of a die because of having a mandrel. And extruding an extruded body for a tool or the like having at least a pair of spiral small holes represented by a so-called oil hole twist drill having cutting oil supply holes.

[0002]

2. Description of the Related Art A twist drill with an oil hole is provided with a pair of small holes spirally connected around an axis, but is difficult to manufacture and high in cost as described below. The material for twist drills with oil holes, which is manufactured from ingots, is a short rod-shaped material that has two straight holes that are symmetrically parallel to the axis on both sides of the axis, and then has the desired cross-sectional shape. It is manufactured by drawing the drawn material until it reaches the size, and then mechanically twisting the drawn material so that the hole becomes a predetermined lead. In the case of the powder metallurgy method, a powder kneaded body such as a high speed tool steel is extruded into a green having a pair of straight holes by an extrusion molding method, then sintered, and mechanically similarly to the ingot material. A method of applying a twist to form a spiral small hole is used.

However, a method of mechanically twisting after obtaining a material having straight holes as described above is as follows.
There is a problem in that the cost increases because it requires a process until the material is obtained and an expensive twisting device is required. For this reason, in the powder metallurgy method, it has been proposed to mold the powder into a spiral small hole in a green state. That is, Japanese Unexamined Patent Publication No. 61-227101 and Japanese Unexamined Patent Publication No. 1-156405 disclose a forming method in which a material for a drill having a spiral small hole is obtained by imparting a twist simultaneously with extrusion.

The applicant of the present invention also provides a method for twisting and extruding a sintering material for forming a twist hole as it is formed, and a twisting extruder and an extrusion method for a sintering material for obtaining a twist hole and a twist groove. Furthermore, by rotating a mandrel having a spiral twist pin, an extrusion method and an apparatus for obtaining a twist hole without forcing a twisting motion on a material to be extruded have been developed.
6305, JP-A-2-034702, JP-A3-1.
No. 07401 was filed. Furthermore, special table flat 6-50
As shown in FIG. 4, No. 8301 is a shell-shaped filamentous material support body 2 in which the tip is in the hole cavity of the nozzle 22 and the end is the opening side of the nozzle.
By providing 6, the inner cavity of the nozzle 22 and the support 2
6 and an annular space 32 is formed between them, and the filamentous material 29 is attached to an appropriate position on the shell-like surface of the filamentous material support 26, and has a twisted inner hole for pumping the plastic kneading body through the annular space 32. We are proposing a die for rod manufacturing.

[0005]

Among the methods of extruding while giving a twisting motion to the extruded body, the method described in, for example, the above-mentioned Japanese Unexamined Patent Publication No.
Although there are methods such as those found in 1-227101 and JP-A-1-156405, these methods are intended to impart a twisting motion to a material to be extruded by means of a twist groove formed in the inner diameter of a die. However, in these methods, the material to be extruded which is extruded in the central portion of the cross section among the materials extruded in the inner diameter of the die in the axial direction, despite the presence of the outer peripheral side portion which undergoes the twisting motion by the twist groove. Since it is going straight, the entire cross section of the extruded material cannot fit the twist groove of the inner diameter of the die.Therefore, the lead of the spiral small hole of the formed sintering material is larger than the lead of the twist groove of the inner diameter of the die. However, there is a problem that the die becomes twisted and grooved on the outer periphery of the molded body.

After extruding with a twist groove on the outer circumference, it is obstructed in bending correction and outer diameter polishing as a pre-process of forming a chip removal groove of a drill by grinding etc. However, there is a problem that the yield is reduced. Further, if the lead of the spiral small hole is disturbed, the spiral small hole will be opened in this groove at the time of forming a chip removing groove as a drill. Especially when it is attempted to increase the single length of the extruded material in order to improve productivity, the risk of this opening increases. Further, in Japanese Patent Laid-Open Nos. 1-96305 and 2-034702, a twist fin is arranged at the center of the inner diameter of the die in the axial direction, and the material to be extruded is made to work together with the twist groove of the inner diameter of the die. It is given a twist. However, even though these are improved, sufficient twist cannot be imparted due to the rectilinear action of the material to be molded flowing in the central portion of the cross section, and thus the lead of the spiral small hole of the molded sintering material is not After all, it is larger than the lead of the inner diameter spiral groove and also varies.

Further, in the method of Japanese Patent Laid-Open No. 3-107401, as shown in FIG. 3, the material to be extruded is formed into a spiral chamber 10a,
The material to be extruded is not forcedly rotated while being press-fitted into the duct portion upstream of the die from 10b, but the mandrel is rotated to suppress the variation of the lead. However, there is a problem that the mandrel with the twist pin is eccentric due to the lateral pressure when the material to be extruded is introduced from the side (spiral chamber), and the small hole position shifts. Since the inflow state of is not uniform on the entire circumference, this effect extends to the extrusion opening, and the molded body already bends when it exits the extrusion die, or when bending occurs due to the difference in shrinkage during sintering, etc. It turned out to be a problem.

Further, in the method according to the above-mentioned Japanese Patent Publication No. 6-508301, the filamentous material lays down due to the flow of the plastic material fed through the annular space 12, and the molded article is spirally wound at a predetermined radial position. Tests have shown that no holes are formed. In view of the above problems, the present invention, in the extrusion of introducing the material to be extruded from the side, such as bending and particle density difference, the cross-section non-uniformity of the extruded material and spiral small holes,
An object of the present invention is to provide a method for extruding an extruded material with high lead accuracy and without eccentricity.

[0009]

Means for Solving the Problems The present inventor has conducted various studies in order to obtain an extruded material having high uniformity and an extruded material having spiral small holes with high lead accuracy, and as a result, upstream of the extrusion die. If the method of introducing the extruded material into the side duct part from the side is adopted, the motion state of the extruded material is averaged as it goes downstream from this introduction point, and it becomes almost constant after a certain position. I found it. And its position is the slenderness ratio, where D is the diameter of the duct and L is the length.
It was found that the L / D was at a position of approximately 3 or more.
Therefore, by providing the die extrusion opening after this position, it is possible to prevent the occurrence of bending or the like. In this case, for example, when the mandrel is provided by the method of Japanese Patent Laid-Open No. 3-107401, the mandrel becomes long and the mandrel is easily displaced by the lateral pressure.

The extrusion pressure for extruding the material to be extruded from the opening of the die is related to the amount of the binder added, but is generally very high. Therefore, conventionally, it was considered difficult to practically rotate and support a mandrel or the like by a bearing while the material to be extruded was filled, because the bearing was damaged due to the entry of the material into the bearing. . The inventor intentionally tried to install a bearing because the mandrel becomes long and easily displaced from the shaft center by setting the slenderness ratio L / D ≧ 3 as described above. As a result, it was found that the intrusion of the kneaded material into the inside of the bearing was nothing but anxiety. That is, the mandrel can be rotatably supported by the bearings provided in the duct or the extrusion die portion, and the eccentricity of the mandrel can be prevented.

Therefore, the first invention of the present application is an extrusion method for extruding a plastic kneading body to be extruded through an extrusion opening of a die, wherein the plastic kneading body to be extruded is laterally connected to a duct portion upstream of the extrusion die. It is introduced, and the slenderness ratio from the center of this introduction part to the exit of the die is 3.0.
A second aspect of the present invention is a method for extruding a plastic kneading body characterized in that the pin portion connected to the end of the rod-shaped mandrel in a spiral shape is extruded from an extrusion die existing in an extrusion opening. In the extrusion method for extruding a kneaded body, the mandrel is rotatably supported by a bearing provided in the extruded plastic kneaded body, which is an extrusion method for a plastic kneaded body.

[0012]

According to the first invention of the present application, when the kneaded material to be extruded is introduced into the upstream portion of the extrusion die from the side, the flow state is not uniform with respect to the axial center of the duct immediately downstream thereof. As it goes downstream, it will be averaged,
Assuming that the inner diameter of the duct is D and the distance from the center of the introduction part to the die exit is L, and L / D is 3.0 or more, the effect of introducing the kneading body from the side can be almost ignored. This is because it was found that the extruded product has straightness and uniform shrinkage at the time of sintering by extruding from such a downstream portion.
From this, in the present invention, the slenderness ratio B is defined as follows and generalized. If the total internal surface area and the total volume (ignoring the existence of mandrels and bearings) of the die from the center of the inlet of the kneading body to the outlet of the die are S and V, respectively, and the same load average cross-sectional area A, A = V / L, B = S
/ A = S ・ L / V ≒ L / D

The second invention of the present application is based on the finding that, when a bearing is provided in the plastic kneading body, the bearing is not damaged by the intrusion of the plastic kneading body. It is applied to a rotating mandrel. Thereby, even in the case of extrusion in which the mandrel is provided along the axis of the screw of the above-mentioned JP-A-3-107401 or the extruder, the mandrel is rotatably supported by the bearing to prevent the eccentricity of the torsion pin due to lateral pressure, etc. It is possible to eliminate the deviation of the small hole position. In the extrusion of the extruded material with spiral small holes, the reason why the mandrel is rotated is to form the spiral small holes without violating the characteristics of the plastic kneading body which is going straight without rotating.
Therefore, it is not necessary to provide a twist groove or the like on the inner diameter of the die, a groove is not formed on the outer peripheral surface of the molded body, and the yield in post-processing can be improved. Further, since the molded body does not rotate, there is no variation in leads due to friction with the takeout tray.

[0014]

EXAMPLES The present invention will be described in detail with reference to Examples. (Embodiment) FIG. 1 is a sectional view showing an embodiment of a molding apparatus to which the first and second inventions of the present application are applied. In the present embodiment, the plastic kneading body as the extruded material is the mandrel 3b.
In order to prevent the increase of the length of the extrusion die 5, it is introduced into the duct (portion of diameter D) which is the upstream portion of the extrusion die 5 from the side by an extruder (not shown) as shown by the arrow. The extruder comprises a cylinder having a horizontal axis and a screw. A mandrel 3b around a horizontal axis passes through the spigot-shaped bearing 3c held by the die 3 and the die mounting die 7 and the corner wall surface of the elbow-shaped inner diameter of the die 3 and is not shown. It is rotationally driven by a drive device. An extrusion die 5 having an inner diameter of 12.6 mmφ is attached to the tip of the die mounting die 7, and a twist pin having an outer diameter of 2.08 mmφ, an interval of 6.28 mmφ and a lead of 56.7 mm is attached to the center of the extrusion die inner diameter. The attached yoke 6 is screwed into the tip of the shaft portion to form the mandrel 3b.

The inner diameter of the duct portion of this extruder is D =
The distance from the extension of the axial center of the extruder 1 to the outlet of the extrusion die was L = 180 mm, and L / D = 5.14. Remove the yoke 6 with the twist pin of the above-mentioned device from the shaft portion of the mandrel 3b,
After screwing a dummy bolt into the screw hole, the extruder is driven to add a powder having an alloy composition corresponding to AISI T15 after sintering and kneading it with a binder to add a material to be extruded as a plastic kneading body. The pressure was introduced and the mixture was extruded from the extrusion die 5, and the extruder 1 was adjusted so that the extrusion speed was 1020.6 mm / min. Subsequently, the variable motor 4b is driven to adjust the rotation of the mandrel 3b to 18 rpm, the extruder 1 and the variable motor 4a are stopped, the dummy bolt of the mandrel 3b is removed, and the yoke 6 with a twist pin is attached. Screw-in, again extruder 1 and variable motor 4
A was driven to perform extrusion molding. The extruded body was extruded to a predetermined length and cut to obtain a sintering material having an outer diameter of 12.8 mmφ, an inner diameter of 2.09 mmφ, a hole interval of 6.25 mm, and spiral hole leads of 56.9 mm to 57.3 mm. .

At this time, the extrusion angle of the die 3 was horizontal. The molded body did not bend, and went straight on the take-out tray. Further, the molded body was cut into round slices, and the displacement of the inner diameter of the twisted hole was investigated. As shown in FIG. 2, the eccentricity was 0.03 mm / 2 = 0.15 mm in the X-axis direction of the molded body and 0. It was 02 mm, and could be easily put within 0.1 mm of the target. Use this sintering material in a reducing atmosphere for 4
After holding at 00 to 650 ° C. for 2 hours to remove the binder, vacuum sintering was performed at 1200 to 1250 ° C. for 2 hours. After sintering, the dimensions of each part were measured, and as a result, the outer diameter was 10.
4 mmφ (target 10.3 mmφ), inner diameter 1.7 mmφ
(Target 1.7 mmφ ± 0.08 mm), distance between holes 5.1
mm (target 5.12 mm ± 0.12 mm), the lead is 46.4 mm to 46.6 mm (target 46.2 mm ±
0.5mm) and the target size can be obtained,
Moreover, the bending could be reduced to about 1/3 of that of the conventional product.

[0017]

As described above, according to the first invention of the present application, a product having high straightness can be obtained in the extrusion method of laterally introducing the material to be extruded. Also, the second
According to the invention, it is possible to improve the positional accuracy of the mandrel, which directly and evenly shrinks during sintering to obtain a sintered product having high small hole positional accuracy and high straightness. You can As described above, the present invention facilitates the production of a twist drill material with an oil hole having a high dimensional accuracy by the extrusion molding method of powder metallurgy, and compared with the one accompanied with the twisting which is currently put into practical use. It realizes a significant cost reduction.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a molding apparatus of the present invention.

FIG. 2 is a diagram showing a measurement result of a twist hole position of a molded product molded by the method of the present invention.

FIG. 3 is a cross-sectional view showing an extrusion molding method and apparatus for a sintering material having a spiral hole according to the invention of JP-A-3-107401.

FIG. 4 is a diagram illustrating an extrusion molding die of Japanese Patent Publication No. 6-508301.

[Explanation of symbols]

3 bases, 5 extrusion dies, 6 twist pins with yaw
C, 7 Die mounting mold, 3b mandrel, 3c bearing, 10a inlet, 10b swirl chamber, 22 nozzles, 2
6 thread support, 29 thread, 32 annular space

Claims (4)

[Claims] 1. In an extrusion method of extruding a plastic kneaded material to be extruded through an extrusion opening of a die, the plastic kneaded material to be extruded is introduced laterally into a duct portion upstream of the extrusion die, and A method for extruding a plastic kneaded body, wherein the slenderness ratio from the center to the outlet of the die is 3.0 or more. 2. A die and a duct have a mandrel, one end of which reaches an extrusion opening, the other end of which extends further through an introduction part of a plastic kneading body, and which is rotationally driven from the other end side. The method for extruding a plastic kneading body according to claim 1, wherein the mandrel is rotatably supported by a bearing provided in the plastic kneading body. 3. The method for extruding a plastic kneading body according to claim 2, wherein the end portion on the extrusion opening side of the mandrel is a pair of spirally connected pins. 4. An extrusion method for extruding a plastic kneading object to be extruded from an extrusion die existing in an extrusion opening of a pin portion spirally connected to an end portion of a rod-shaped mandrel,
The extrusion method of a plastic kneading body, wherein the mandrel is rotatably supported by a bearing provided in the extruded plastic kneading body.