JP7271160B2 - Cutting device and cutting method - Google Patents

Description

The present disclosure relates to a cutting apparatus and a cutting method suitable for use in, for example, spot boring.

2. Description of the Related Art As a joint structure provided with a flange surface of a large structure, for example, an inner casing of a steam turbine has a structure divided into upper and lower parts. A plurality of fastening bolts are used to connect the upper and lower inner compartments. In order to insert these fastening bolts, a large number of fastening holes are provided in the flange portion of the inner compartment. Each fastening hole is formed with a countersunk portion in which the head of the fastening bolt is accommodated. When forming the counterbore portion, a boring machine is used to perform reverse counterbore processing (see Patent Document 1 below).

Japanese Utility Model Laid-Open No. 62-58103

As an example of back spot boring using a boring machine, for example, insert a processing tool with a cutting tool into a fastening hole and rotate it to feed the cutting edge in the axial direction of the fastening hole while keeping the machining diameter constant. are being processed. When cutting, the rotating cutting edge is in contact with the machining surface in the radial direction, and the machining tool is long, so the cutting resistance applied to the machining tool increases, causing the blade to vibrate. It is necessary to select the cutting conditions so that the machining accuracy does not deteriorate. In addition, there is a problem that it takes time and effort to replace and adjust the cutting tool with the cutting edge worn out.

In Patent Literature 1, a plurality of cutters are attached to an eccentric disk connected to a large-diameter arbor to increase rigidity and improve cutting speed.
However, in Patent Document 1, it is essential to use a large-diameter arbor in order to increase rigidity. There is a problem that it takes a long time to process. Moreover, if the diameter of the arbor is reduced in order to machine the smaller diameter pilot hole, there is a problem that the rigidity of the arbor is lowered. If the rigidity decreases, there is a risk that vibration (chatter) will occur when the cutting resistance to the workpiece increases, resulting in a decrease in machining accuracy.

The present disclosure has been made in view of such circumstances. The object is to provide a processing method.

A cutting device according to an aspect of the present disclosure includes a face plate attached to a main shaft that rotates around a rotation axis, and a slide portion attached to the face plate via a slide portion, and radially with respect to the rotation axis. An eccentric bar having an eccentric longitudinal axis and a mounting piece that detachably accommodates a cutting tool at the tip of the eccentric bar , the slide portion being provided on the face plate and used during cutting for spot boring and, without moving in the direction of the rotational axis, the eccentric bar is moved in the radial direction of the face plate to enable slide adjustment for cutting in the radial direction .

A cutting tool detachably accommodated in an attachment piece attached to the tip of an eccentric bar attached to the face plate countersinks the pilot hole. That is, as the eccentric bar is slid in the radial direction by the sliding portion, the cutting tool is sent in the radial direction to perform the counterboring. Since the cutting tool can be slid in the radial direction for cutting, it is possible to reduce the cutting resistance compared to cutting by sending the cutting tool in the machining direction while keeping the cutting tool in contact with the workpiece in the radial direction. As a result, it is possible to improve the machining speed while maintaining the machining accuracy by reducing the vibration of the cutting tool and the eccentric bar.
As the cutter, for example, a carbide tip is used.

A cutting method according to an aspect of the present invention includes: a face plate attached to a main shaft that rotates about a rotation axis; A cutting method using an eccentric bar having an eccentric longitudinal axis and a mounting piece that detachably accommodates a cutting tool at the tip of the eccentric bar, wherein the sliding portion is used during cutting to perform counterboring. and a sliding step of performing cutting in the radial direction by sliding the eccentric bar in the radial direction of the face plate without moving it in the direction of the rotation axis.

A cutting tool attached to the tip of the eccentric bar counterbores the pilot hole. That is, as the eccentric bar is slid in the radial direction, the cutting tool is sent in the radial direction of the rotation axis to perform the spot boring. In this way, since cutting can be performed by sliding in the radial direction, the cutting resistance is lower than when cutting is performed by sending a cutting tool having a long cutting edge that enables cutting in the radial direction in the processing direction while keeping it in contact with the workpiece. can be reduced. As a result, it is possible to improve the machining speed while maintaining the machining accuracy by reducing the vibration of the cutting tool and the eccentric bar.
The cutting tool may be one that can perform cutting at the tip of the cutting edge, and for example, a cemented carbide tip is used.

Furthermore, in the cutting method according to the aspect of the present invention, the slide step is performed multiple times through a Z-axis movement step of moving in the rotation axis direction.

After moving in the Z-axis direction, which is the rotation axis direction, the slide process is performed multiple times. Accordingly, cutting resistance can be optimized by adjusting the depth of cut in the Z-axis direction.

Furthermore, the cutting method according to an aspect of the present invention includes chamfering and/or finishing of corners using the cutting tool after performing the sliding step.

The corners are chamfered in the slide process. As a result, a chamfered portion (for example, an R-shaped portion) can be formed at the corner of the counterbore. By continuously performing the sliding process and the chamfering process in this way, it is possible to reduce the processing time.
Also, after performing the sliding process and the chamfering process, the finishing process is performed. When performing the finishing process, the same cutting tool as used in the sliding process and the chamfering process can be used, so that the processing time can be shortened.
The finishing process includes finishing of the bottom surface and side peripheral surface of the counterbore.

Since processing is performed while feeding in the radial direction by the slide portion, processing time can be shortened when counterboring a large number of fastening holes while maintaining processing accuracy.

It is the side view which showed the inner compartment. FIG. 2 is a plan view of the inner compartment of FIG. 1; It is a perspective view showing the main part of the horizontal boring machine. Figure 3 is a side view of the eccentric bar and holder of Figure 2; It is a partial cross-sectional side view showing a slide mechanism. FIG. 4 is a plan view showing a state in which the carbide tip is positioned at a predetermined diameter at the start of back spot facing. FIG. 10 is a plan view showing a state in which a counterbore is processed by a sliding process; FIG. 10 is a plan view showing a state in which chamfering is performed; It is the top view which showed the state which performs finish machining.

An embodiment according to the present invention will be described below with reference to the drawings.
In the following description, the positional relationship of each component described using the terms "upper" and "lower" indicates the vertically upper side and the vertically lower side, respectively.

FIG. 1A shows, for example, an inner casing 1 as a joint structure provided with a flange surface of a large-sized structure to be machined by a horizontal boring machine (cutting device) according to this embodiment. The inner casing 1 constitutes a part of a low pressure casing of a low pressure steam turbine for power generation. The inner casing 1 is made of iron such as SS400 and has a cylindrical shape, and a low-pressure turbine (not shown) is accommodated therein.

The inner casing 1 has a split structure in which a plane including the axis of the cylindrical shape is a split plane, and has an upper half portion 1a and a lower half portion 1b. Each of the upper half portion 1a and the lower half portion 1b is provided with flange portions 2a and 2b projecting radially outward with respect to the axis of the cylindrical shape at positions corresponding to the mating surfaces of each other.

Fastening holes 3a and 3b into which fastening bolts (not shown) for fastening and fixing the upper half portion 1a and the lower half portion 1b of the inner casing 1 are inserted are formed in the flange portions 2a and 2b. The fastening hole 3a formed in the upper half portion 1a includes a pilot hole 3a1 penetrating downward to serve as a mating surface, and a counterbore 3a2 located above the pilot hole 3a1 and having an enlarged diameter from the pilot hole 3a1. It has The counterbore portion 3a2 accommodates the head portion of the fastening bolt.
The pilot hole 3a1 has a diameter of, for example, φ50 mm or more and φ90 mm or less, and the counterbore portion has a diameter of φ90 mm or more and φ150 mm or less, for example.

The fastening hole 3b formed in the lower half portion 1b is a bottomed hole that is formed from the upper part, which is the mating surface, toward the lower part. A female screw corresponding to the fastening bolt is formed on the inner peripheral surface of the fastening hole 3b.

As shown in FIG. 1B, a large number of fastening holes 3a and 3b are formed at predetermined intervals in the longitudinal direction of the flange portions 2a and 2b. The number of fastening holes 3a and 3b is not limited to that of this embodiment, and is appropriately set according to the size of the inner compartment 1. As shown in FIG.

FIG. 2 shows a main part of the horizontal boring machine 7. As shown in FIG. In this embodiment, the inner casing 1 is placed upright with its axis in the vertical direction, and the fastening hole 3a is counterbored by a horizontal boring machine 7 so as to boring in the lateral direction (horizontal direction). done. The counterbore processing is performed as reverse counterbore processing for processing the machined surface (back surface) on the opposite side as seen from the horizontal boring machine 7 .

A main shaft 8 of the horizontal boring machine 7 has a substantially cylindrical shape and rotates around a central axis CL1 extending in the Z-axis direction. The main shaft 8 is rotationally driven by an electric motor (not shown). The rotation speed of the main shaft 8 is controlled by a control section (not shown). Further, the main shaft 8 can be moved in the Z-axis direction (specifically, in the horizontal direction) as indicated by an arrow A1 by a control unit (not shown).

A face plate 10 is attached and fixed to the tip of the main shaft 8 . The face plate 10 has a flat cylindrical outer shape. The center of the face plate 10 is attached so as to match the center of the main shaft 8 . As a result, the face plate 10 rotates about the central axis CL1 in the direction of the arrow A2. An eccentric bar 14 is attached to the face plate 10 via a holder 12 . A groove is formed at the tip of the eccentric bar 14, and a mounting piece 18 having a cemented carbide tip (cutting tool) 16 is fixed.

The holder 12 and the eccentric bar 14 are shown in FIG. The longitudinal axis CL2 of the eccentric bar 14 is offset from the center axis CL3 of the holder 12 by a predetermined distance. The eccentric bar 14 is fixed so as to rotate together with the holder 12 so as not to move relative to the holder 12 such as rotation.

The cemented carbide tip 16 is replaceably fixed to a plate-like mounting piece 18 projecting from the tip of the eccentric bar 14 in a direction perpendicular to the longitudinal axis CL2.

As shown in FIG. 2 , the base end of holder 12 is fixed to slide portion 20 of face plate 10 . The sliding portion 20 can be moved in the radial direction of the face plate 10 (arrow A3 direction: V direction) by a slide mechanism provided on the face plate 10 .

FIG. 4 shows a slide mechanism 22 for sliding the slide portion 20. As shown in FIG. The slide mechanism 22 is a screw feed mechanism. The slide mechanism 22 includes a nut 24 fixed to the slide portion 20 , a feed screw 25 screwed onto the nut 24 , and bevel gears 26 a and 26 b that transmit power to the feed screw 25 .

A gear 27 is provided at the upstream end of the bevel gear 26b (the right end in the drawing). A pinion 28 meshes with the gear 27 and is attached to a drive shaft 29 . The drive shaft 29 is rotatably supported by bearings 30 . Power is transmitted to the drive shaft 29 from a slide electric motor 33 via a feed shaft 31 and a positioning mechanism 32 . The positioning mechanism 32 determines the amount of movement of the slide portion 20 in the A3 direction, and is NC-controlled by a control portion (not shown).

In this manner, when a predetermined amount of movement is commanded by NC control from the control section, the amount of rotation of the feed screw 25 is determined by the positioning mechanism 32 . Then, power from the electric motor 33 for sliding according to the amount of rotation is transmitted to the feed screw 25 via the drive shaft 29, the pinion 28, the gear 27, and the bevel gears 26a and 26b. Rotation of the feed screw 25 allows the slide portion 20 fixed to the nut 24 to reciprocate in the direction A3, and allows the face plate 10 to rotate in the direction A2.

The control unit includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads out this program to a RAM or the like, and executes information processing and arithmetic processing. As a result, various functions are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

Next, a back spot boring method using the horizontal boring machine 7 configured as described above will be described. It should be noted that a series of machining steps described below are performed by NC control by a control unit. In addition, in a series of processes described below, machining is performed while the cemented carbide tip 16 is continuously used for roughing and finishing without the need to replace it.

As shown in FIG. 5A, the eccentric bar 14 is inserted so as to pass through the pilot hole 3a1 previously formed in the flange portion 2a (see FIG. 1), and the carbide tip 16 is attached to the back surface of the flange portion 2a (see FIG. 1). in the upper side of the paper surface). Then, by NC control by the control unit, the slide unit 20 is moved to a position corresponding to the predetermined diameter dimension of the counterbore portion 3a2 (see FIG. 1) during cutting, thereby moving and adjusting the radial position of the carbide tip 16. Cutting can be done while Further, by rotating the main shaft 8 (see FIG. 2) around the central axis CL1 and moving the main shaft 8 to the + side in the Z-axis direction (downward in the drawing) so as to pull in the carbide tip 16, The hard tip 16 is brought into contact with the flange portion 2a to start cutting the counterbore portion 3a2. Since cutting is performed at the tip of the cemented carbide tip 16, frictional heat during cutting can be reduced.

When cutting is started, as shown in FIG. 5B, the sliding portion 20 is moved and adjusted in the radial direction (V direction) by the slide mechanism 22, and cutting in the radial direction is performed (sliding step). When the cutting in the radial direction is completed, the Z-axis moving step is performed by moving the main shaft 8 to the + side in the Z-axis direction by a predetermined amount in the Z-axis direction. The amount of movement in the Z-axis direction is determined based on an appropriate cutting amount and the like, and is performed by NC control by the control unit. After performing the Z-axis movement step, the workpiece is again slid from the inside to the outside in the radial direction for machining. The sliding process and the Z-axis moving process are repeated multiple times. The number of repetitions is determined from an appropriate cutting amount and the like.

Then, as shown in FIG. 5C, when the final sliding process is performed from the inner peripheral side toward the outer peripheral side at the position corresponding to the bottom surface of the counterbore portion 3a2, the corner portion of the counterbore portion 3a2 is continuously moved. Chamfering is performed at a position corresponding to 3d (chamfering process). As the chamfering process, for example, an R process for forming a curved surface is performed. Chamfering is also performed by a slide process and a Z-axis movement process under NC control by the control unit. In this way, the transition from the sliding process to the chamfering process is performed continuously, and the cemented carbide tip 16 is not replaced.

Then, as shown in FIG. 5D, bottom surface finishing is performed while feeding the slide portion 20 in the radial direction so as to finish the bottom surface of the counterbore portion 3a2. Subsequently, the side peripheral surface is finished while feeding the cemented carbide tip 16 in the opposite direction of the Z-axis (upward on the paper surface) so as to finish the side peripheral surface of the counterbored portion 3a2. Specifically, as the finishing process, the feed speed of the cemented carbide tip 16 and the like are controlled so as to obtain a predetermined surface roughness.

According to this embodiment mentioned above, there exist the following effects.
The slide portion 20 slides the eccentric bar 14 in the radial direction during cutting. As a result, the workpiece is counterbored by feeding the carbide tip 16 in the radial direction. Since the cutting tool can be slid in the radial direction for cutting, it is possible to reduce the cutting resistance compared to cutting by sending the cutting tool in the axial direction while keeping the cutting tool in contact with the workpiece in the radial direction. As a result, by reducing the vibration of the carbide tip 16 and the eccentric bar 14, it is possible to improve the machining speed while maintaining the machining accuracy.

After moving in the Z-axis direction, the slide process is performed multiple times. Accordingly, cutting resistance can be optimized by adjusting the depth of cut in the Z-axis direction.

After performing the sliding process, the corners 3d were chamfered. As a result, a chamfered portion can be formed at the corner portion 3d of the counterbore portion 3a2, and the same cemented carbide tip 16 used in the slide process is used for chamfering. By continuously performing the sliding process and the chamfering process in this way, it is possible to reduce the processing time.

Following the chamfering process, we decided to perform a finishing process for finishing. When the finishing process is carried out, it is carried out by NC control by the control unit, so that the machining process can be shortened.

In the above-described embodiment, the processing of the counterbore portion 3a2 on the flange portion 2a of the inner casing 1 has been described as an example, but the present invention is not limited to this. In general, the present invention can be applied to the back spot facing of metal materials.

1 Inner casing 1a Upper half 1b Lower half 2a (Upper half) Flange 2b (Lower half) Flange 3a (Upper half) fastening hole 3a1 Pilot hole 3a2 Counterbore 3b (Lower half part) fastening hole 3d corner 7 horizontal boring machine (cutting device)
8 Spindle 10 Face plate 12 Holder 14 Eccentric bar 16 Carbide tip (cutting tool)
18 Mounting piece 20 Slide part 22 Slide mechanism 24 Nut 25 Feed screw 26a, 26b Bevel gear 27 Gear 28 Pinion 29 Drive shaft 30 Bearing 31 Feed shaft 32 Positioning mechanism 33 Slide electric motor CL1 (main shaft) center axis CL2 (eccentric bar )Longitudinal axis CL3 (Holder) center axis

Claims (4)

a face plate attached to a main shaft that rotates about the axis of rotation;
an eccentric bar attached to the faceplate via a slide and having a longitudinal axis radially eccentric to the axis of rotation;
a mounting piece that detachably accommodates a cutting tool at the tip of the eccentric bar;
with
The slide portion is provided on the face plate, and is configured to move the eccentric bar in the radial direction of the face plate without moving it in the direction of the rotation axis during cutting for spot boring , thereby performing cutting in the radial direction. A cutting device that enables slide adjustment for processing . a face plate attached to a main shaft that rotates about the axis of rotation;
an eccentric bar attached to the faceplate via a slide and having a longitudinal axis radially eccentric to the axis of rotation;
a mounting piece that detachably accommodates a cutting tool at the tip of the eccentric bar;
A cutting method using
A slide step of performing cutting in the radial direction by sliding the eccentric bar in the radial direction of the face plate without moving it in the direction of the rotation axis during cutting for spot boring by the slide portion. cutting method. 3. The cutting method according to claim 2, wherein said sliding step is performed a plurality of times through a Z-axis moving step of moving in said rotation axis direction. 4. The cutting method according to claim 3, further comprising a step of chamfering and/or finishing a corner using said cutting tool after performing said sliding step.

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