JP5412537B2 - Method for producing thin-walled cylindrical metal member with bottom - Google Patents

Description

  The present invention relates to a method for producing a thin-walled cylindrical metal member such as a core pin (core pin) used for a die casting die, for example.

Generally, a core pin (core pin) fixed to a die casting die is used to form a hole such as a bolt hole in a die cast product. The core pin is a metal round bar, and there is a core pin in which a cooling hole is formed along the central axis, and a solid pin in which no cooling hole is formed. The following Patent Document 1 discloses a core pin in which a cooling hole is formed.
The use of the core pin in which the cooling hole is formed is advantageous in that the shrinkage nest generated in the die-cast product can be moved away from the core pin position.

On the other hand, when supplying coolant such as water to the cooling hole of the core pin, it is performed by inserting a pipe into the cooling hole. However, when the hole diameter of the cooling hole is small, the pipe diameter becomes small and the pipe is clogged. Is likely to occur. In addition, the gap between the cooling hole and the outer periphery of the pipe becomes narrow, and clogging is likely to occur. When such clogging occurs, the core pin cannot be cooled, and seizure or the like occurs, increasing the defect rate of the die-cast product. Therefore, it is preferable to increase the pipe diameter by increasing the diameter of the cooling hole to avoid clogging of the pipe and to increase the cooling effect by increasing the coolant flow rate.
However, conventionally, the thickness of the core pin in which the cooling hole is formed is set to 1 mm or more, and it has not been sufficiently studied to increase the diameter of the cooling hole by reducing the thickness. This is because, since the core pin has a long shape, it has been considered that it is difficult to reduce the wall thickness to less than 1 mm.

  Therefore, a method for manufacturing a thin-walled cylindrical metal member that enables thinning processing is disclosed in Patent Document 2 below.

Japanese Patent Laid-Open No. 9-1313 JP 2009-90444 A

  However, when a workpiece W having a large shaft diameter (for example, an outer diameter of 20 mm or more) is to be cut using the manufacturing method disclosed in Patent Document 2, a connection portion between the workpiece W and the jig 20 (more specifically) Is caught when the one end surface of the jig 20 on the side to which the workpiece W is connected is inserted (inserted) into the narrowest part (the place having the smallest diameter) of the guide bush of the Swiss type automatic lathe. In addition, the jig 20 may not be able to advance in the axial direction.

  The present invention has been made in view of the above-described circumstances, and one end surface of a jig collides with a guide bush of a Swiss-type automatic lathe during cutting, and the workpiece and the jig cannot be sent out in the axial direction. It is an object of the present invention to provide a method for manufacturing a thin-walled cylindrical metal member that can prevent (avoid) this and improve productivity.

In order to achieve the above object, the present invention provides the following means.
The thin-walled cylindrical metal member manufacturing method of the present invention forms a center hole by cutting along the center axis of a work having a constant outer diameter and being a long metal solid round bar. Then, a hole forming step is performed to form a bottomed hole so that the bottom of the workpiece has a bottom, and then the workpiece is cut so that the outer diameter on the tip side of the workpiece is reduced, thereby thinning the tip side. A thinning step is performed, and during the thinning step, a filling member is inserted into the bottomed hole formed in the hole forming step, one end side of the workpiece is extended, and the workpiece is connected And a fixing step of fixing a jig having a reduced diameter portion formed over a predetermined distance from one end surface to the workpiece and attaching the jig to a chuck of a lathe.

  In the method for manufacturing a thin-walled cylindrical metal member, it is more preferable that the reduced diameter portion is provided between 20 mm and 60 mm along the axial direction from the one end face.

Since the bottomed hole is formed in the solid round bar having a constant outer diameter before the thinning process for cutting so that the outer diameter on the tip side of the workpiece is reduced, it has high rigidity. A bottomed hole can be accurately formed in the workpiece. In addition, since cutting is performed on a workpiece having high rigidity, thermal deformation due to processing heat can be reduced, and a bottomed hole can be formed with high accuracy.
The dimension to be thinned by the thinning process is, for example, less than 1.0 mm, preferably 0.7 mm or less when the workpiece length is about 200 mm to 350 mm, and 1 for example when the workpiece length is about 400 mm. .5 mm, preferably 1.3 mm or less.
Examples of the material of the thin-walled cylindrical metal member include alloy tool steel such as SKD (for example, SKD61), free-cutting steel, brass, copper, stainless steel (SUS), and the like.
The “long shape” means, for example, one having a length of 5 times or more, preferably 10 times or more the diameter of the thinned tip.
The present invention is particularly suitable for manufacturing a core pin used in a die casting mold, which will be described later, and a cooling bush for cooling a die casting mold.

  Further, by inserting the filling member, the rigidity of the workpiece is increased during the thinning process, the deformation of the workpiece can be suppressed during processing, and further thinning is possible.

  Furthermore, since the jig extending one end side of the workpiece is fixed to the workpiece and this jig is attached to the lathe chuck, the lathe can be processed to the vicinity of the one end side of the workpiece. Thereby, material can be used without waste.

  Furthermore, since one end portion of the jig is provided with a reduced diameter portion, one end surface of the jig hits a guide bush of, for example, a Swiss-type automatic lathe during cutting, and feeds the workpiece and the jig in the axial direction. It is possible to prevent (avoid) that it becomes impossible to improve the productivity, and to improve productivity.

  In the method for manufacturing a thin-walled cylindrical metal member, it is more preferable that the thin-walled cylindrical metal member is a core pin used in a die casting die.

  The bottomed hole formed in the core pin can be used as a cooling hole for cooling by supplying a coolant such as water. According to the manufacturing method of the present invention, since the core pin can be thinned, the cooling effect is increased, the shrinkage nest generated in the die cast product can be moved away from the core pin position, and the yield of the die cast product can be improved. .

  According to the present invention, it is possible to prevent (avoid) that the one end surface of the jig hits the guide bush of the Swiss-type automatic lathe and cannot feed the workpiece and the jig in the axial direction during cutting, There is an effect that productivity can be improved.

It is a sectional side view which shows the state which attached the core pin to the metal mold | die for die casting. It is the side view which showed the core pin. It is the figure which showed the manufacturing method of the core pin concerning one Embodiment of this invention. It is the figure which showed the modification of the thinning process. It is a sectional side view which shows the state which attached the jig and the workpiece | work to the lathe. It is the figure which showed the modification of the connection method of a jig and a workpiece | work.

A reference embodiment of a method for producing a thin-walled cylindrical metal member according to the present invention will be described with reference to the drawings.
In this embodiment, a core pin (core pin) used for a die casting mold will be described as an example of a thin-walled cylindrical metal member. First, after explaining the usage form of the core pin and the shape of the core pin, the manufacturing method of the core pin will be described.

  FIG. 1 shows a core pin 1 fixed to a die casting die 3. The tip portion (right side in the figure) 1a side of the core pin 1 protrudes into the mold 3 and is immersed in bath water during die casting production. A center hole is formed in the core pin 1 from the base end portion (left side in the figure) 1b along the center axis thereof, and a cooling hole 1c having a bottom portion at the tip end portion 1a is formed as a bottomed hole. Is formed. A cooling water supply pipe 5 is inserted into the cooling hole 1 c along the central axis of the core pin 1.

  Cooling water is ejected from the tip 5a of the cooling water supply pipe 5 toward the bottom of the cooling hole 1c (that is, the tip 1a of the core pin 1). The other end of the cooling water supply pipe 5 is connected to the cooling water supply pipe 7. A cooling device main body (not shown) is provided on the upstream side of the cooling water supply pipe 7. The cooling water ejected from the tip 5a of the cooling water supply pipe 5 collides with the bottom of the cooling hole 1c, reverses the flow direction, and flows in the cooling hole 1c toward the base end 1b. When the cooling water flows in this way, the core pin 1 is cooled from the inside by receiving the heat transferred through the wall portion of the core pin 1. The cooling water that has flowed toward the base end 1b flows into the connecting pipe 9 connected to the base end 1b of the core pin 1, and is guided to a cooling device main body (not shown) through the cooling water return pipe 11. .

  As described above, since the die casting manufacturing process is performed while supplying cooling water into the core pin 1, seizure of the core pin 1 can be prevented and the shrinkage nest generated in the die cast product can be moved away from the position of the core pin 1.

FIG. 2 shows the shape of the core pin 1. Note that the shape of the core pin shown in the figure is merely an example, and the present invention is not limited to this shape.
The core pin 1 includes a large diameter portion 12 located on the base end portion 1b side, a small diameter tapered portion 14 located on the distal end portion 1a side and having a smaller diameter than the large diameter portion 12, and the large diameter portion 12 and the small diameter tapered portion. 14 and a small-diameter straight portion 16 continuously connected to the small-diameter tapered portion 14.

The diameter of the large diameter portion 12 is, for example, 13 mm, and the diameter of the small diameter linear portion 16 is, for example, 4.1 mm. The small diameter taper portion 14 is 4.1 mm on the base end portion 1b side, and has a taper shape that tapers toward the tip. The taper angle is set to 1 °, for example. The tip of the small-diameter tapered portion 14, that is, the tip 1a of the core pin 1 is processed to have a spherical shape.
The length of the core pin 1 is 250 mm. The large diameter portion 12 has a length of 25 mm, the small diameter linear portion 16 has a length of 203 mm, and the small diameter tapered portion 14 has a length of 22 mm.

The core pin 1 is formed with a central hole as a cooling hole 1c along the central axis from the base end 1b to the front of the front end 1a. The tip 1a side of the cooling hole 1c does not penetrate, and a bottom 1d is provided. Thus, the cooling hole 1c is a bottomed hole. The diameter of the cooling hole 1c is 2.0 mm. An internal thread 18 is formed on the base end 1b side of the cooling hole 1c. With the female screw 18, the distal end (right side in FIG. 1) of the connection tube 9 shown in FIG. 1 is screwed to the core pin 1.
Since the diameter is small at the tip of the small diameter taper portion 14 of the core pin 1, the thickness at this position is the thinnest. The core pin shown in FIG. 2 has a thickness of about 0.7 mm.

FIG. 3 shows a method for manufacturing a core pin according to the present embodiment.
First, as shown in FIG. 3A, a workpiece W is obtained by cutting a metal solid round bar as a raw material by a dimension obtained by adding a predetermined length to the length of the core pin 1 as a product. As a cutting dimension, it is about 300 mm, for example. The material of the material is determined depending on the application, and examples thereof include alloy tool steel such as SKD (for example, SKD61), free-cutting steel, brass, copper, and stainless steel (SUS).
Next, as shown in FIG. 3B, the cooling hole 1c is processed so as to leave the bottom 1d at the distal end 1a by cutting from the base end 1b side with a gun drill (or drill) (hole). Forming step).
Next, as shown in FIG. 3C, the workpiece W processed as shown in FIG. 3B is installed on the Swiss type automatic lathe 50 shown in FIG. 5, and the outer shape of the workpiece W is cut. Specifically, the outer shape of the workpiece W is processed so that the small-diameter linear portion 16 and the small-diameter tapered portion 14 shown in FIG. Thereby, a thin part is formed in the small diameter linear part 16 and the small diameter taper part 14 by the side of the front-end | tip part 1a (thinning process).
In FIG. 5, reference numeral 51 denotes a parting tool, reference numeral 52 denotes a guide bush, reference numeral 53 denotes a collet chuck, and reference numeral 54 denotes a feeder finger chuck.

Next, the operational effects of the above-described core pin manufacturing method will be described.
In the manufacturing method according to the present embodiment shown in FIG. 3, a solid round bar having a constant outer diameter before the thinning step of cutting so that the outer diameter on the tip end 1 a side of the workpiece W is reduced; Since the cooling hole 1c is formed in the workpiece W, the cooling hole 1c can be accurately formed in the workpiece W having high rigidity. Moreover, since it cuts with respect to the workpiece | work W which has high rigidity, the thermal deformation by processing heat can be made small and the cooling hole 1c can be formed with sufficient precision.

Further, in the manufacturing method according to the present embodiment shown in FIG. 3, since the thinning process is performed after the hole forming process, the bending inspection of the outer shape of the workpiece W is not required. Since the cooling hole is formed in the workpiece W having high rigidity, most processed products are within the specifications. For a processed product that is out of specification, the subsequent thinning step is not performed, so that the manufacturing load can be suppressed.
Furthermore, according to the manufacturing method according to the present embodiment, processing can be performed with high accuracy, and the outer shape: φ4 × 350, the cooling hole size: φ3.1 × 347, the wall thickness: 0.45 mm, and the cooling hole runout accuracy: 0. It was confirmed that 05 could be processed.
Furthermore, if a hole is formed by measuring the shape by ultrasonic measurement, processing with a thickness of 0.2 mm is possible.

  In the thinning step, a round bar (filling member) may be inserted into the cooling hole 1c formed in the hole forming step, and the thinning step may be performed in this state. By inserting the round bar into the cooling hole 1c, the rigidity of the workpiece W is increased during the thinning process, the deformation of the workpiece W can be suppressed during processing, and further thinning is possible.

Next, the thinning process according to the embodiment of the present invention will be described with reference to FIG.
The thinning process shown in FIG. 4 is characterized in that processing is performed using a jig 20 that extends one end of the workpiece W.
As shown in FIG. 4A, the male screw portion 22 and the fitting portion 24 are formed on one end of the workpiece W after the hole forming step (see FIG. 3B). The male screw portion 22 and the fitting portion 24 are formed on the side to be the base end portion 1b of the core pin later.
On the other hand, the jig 20 has a round bar shape having substantially the same outer shape as the workpiece W. At one end (right side in the drawing) of the jig 20, a female screw portion 26 into which the male screw portion 22 of the workpiece W is screwed and a fitting hole 28 into which the fitting portion 24 is fitted are formed. Further, a reduced diameter portion 29 (FIGS. 4B and 4C) is provided at one end portion of the jig 20 that is inserted (inserted) into the narrowest portion (the portion having the minimum diameter) of the guide bush 52 shown in FIG. )) Is provided. The reduced diameter portion 29 is provided between 20 mm and 60 mm along the axial direction from one end face 20a (see FIG. 4B) of the jig 20 that contacts the workpiece W, and the other portion (reduced diameter portion 29). The outer diameter is slightly smaller (about 0.1 mm to 0.3 mm) than the outer diameter of the workpiece W before cutting. That is, when the contour of the workpiece W before cutting is extended toward the jig 20, the reduced-diameter portion 29 does not protrude outwardly from the contour of the extended workpiece W. (It does not protrude). In other words, the reduced diameter portion 29 is formed so that the reduced diameter portion 29 does not protrude from the contour of the workpiece W when the workpiece W before cutting is viewed from the end surface opposite to the side to which the jig 20 is connected. Yes.

In the thinning process, as shown in FIG. 4B, the male screw portion 22 and the fitting portion 24 of the workpiece W are connected to the female screw portion 26 and the fitting hole 28 of the jig and fixed. In this state, the other end of the jig 20 is fixed to the feeder chuck 54 (see FIG. 5) of the Swiss automatic lathe 50, and a thinning process is performed (FIG. 5 (c)).
After the thinning process is completed, for example, by cutting a large diameter portion of the workpiece W positioned in the immediate vicinity of the fitting portion 24, the male screw portion 22 and the fitting portion 24 of the workpiece W are removed, and predetermined processing is performed. To make a product (core pin).

As described above, the jig 20 that extends one end of the workpiece W is fixed to the workpiece W, and the jig 20 is attached to the feeder chuck 54 (see FIG. 5) of the Swiss type automatic lathe 50. Thus, it is possible to cut to the vicinity of one end side of the workpiece W. Thereby, material can be used without waste.
Moreover, since the reduced diameter part 29 is provided in the one end part of the jig 20, the one end surface 20a of the jig 20 collides with the guide bush 52 during a cutting process, and can send out the workpiece | work W and the jig 20 to an axial direction. It can be prevented (avoided) from becoming impossible, and productivity can be improved.

  In addition, the connection method of the jig 20 and the workpiece | work W is not limited to what was shown by FIG. For example, as shown to Fig.6 (a), after forming the fitting part 30 in the end of the workpiece | work W, forming the fitting hole 32 in the end of the jig 20, and fitting these ends, As shown in FIG. 6B, a knock pin hole 34 may be formed, and a knock pin 35 (see FIG. 6C) may be driven into the hole 34 for connection.

In the present embodiment, the core pin has been described as an example of a thin bottomed cylindrical metal member, but the present invention is not limited to this. For example, it can also be used for manufacturing a cooling bush for cooling a die casting mold.
Further, the present invention can be used when manufacturing a prototype of a product that is mass-produced by a drawing press. In the drawing press, it is common to manufacture using several molds, and it is not preferable to manufacture the mold for trial production because of cost. If the manufacturing method of this invention is used, since a thin-walled bottomed cylindrical metal member can be manufactured by cutting, a prototype can be manufactured and product confirmation can be performed with little investment. Further, even if the material is difficult to manufacture with a drawing press, the manufacturing method of the present invention has an advantage that it can be manufactured without depending on the material because it is a cutting process.

1 Core Pin 1a Tip 1b Base End 1c Cooling hole (center hole)
20 Jig 20a One end face 29 Reduced diameter part 50 Swiss type automatic lathe 54 Feeder finger chuck W Workpiece

Claims (3)

A center hole is formed by cutting along the center axis of a work having a constant outer diameter and being a long metal solid round bar, and the bottom has a bottom at the tip of the work Perform hole forming process to form holes,
Next, cutting is performed so that the outer diameter on the tip side of the workpiece becomes small, and a thinning process for thinning the tip side is performed,
During the thinning step, the filling member is inserted into the bottomed hole formed in the hole forming step, one end side of the workpiece is extended, and from one end surface on the side to which the workpiece is connected A method of manufacturing a thin-walled cylindrical metal member, comprising: an attaching step of fixing a jig having a reduced diameter portion over a predetermined distance to the workpiece and attaching the jig to a lathe chuck.   The method for producing a thin-walled cylindrical metal member according to claim 1, wherein the reduced diameter portion is provided between 20 mm and 60 mm along the axial direction from the one end surface.   The method for producing a thin-walled cylindrical metal member according to claim 1 or 2, wherein the thin-walled cylindrical metal member is a core pin used in a die casting die.

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