Abrasive tool

Abstract

To provide a polishing tool used in a machine tool and capable of providing a uniform processing surface by imparting motion irregularly combining revolution and rotation to a polishing member even without having a friction connecting part.SOLUTION: A polishing tool 100 gripped by a rotation spindle 310 of a machine tool 300 has a first rotation axis A by rotation of the rotation spindle 310 and a second rotation axis B eccentric from the first rotation axis A. The polishing member 60,70 attached to the tip of the rotation portion connected to the revolution portion rotated by the rotation spindle 310 via the bearing 32 and the gap 52 without having a mechanical transmission mechanism can process a uniform processing surface on the workpiece by performing a motion in which the revolution around the first rotation axis A and the rotation around the second rotation axis B are irregularly combined.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing tool that is attached to a rotating spindle of a machine tool. [Background technology]

[0002] Machine tools often use cutting tools such as end mills and face mills attached to their rotating spindles to finish the surfaces of metal workpieces. The end mill or face mill leaves arc-shaped machining marks called cutter marks. Furthermore, if the width of the surface to be finished is greater than the tool's rotational diameter, the tool is moved laterally in the cutting direction without changing its position in the Z-axis (axial) direction. This is known as multi-pass machining, and linear cutter marks are also left at the boundaries between passes. Modern machine tools and cutting tools are sufficiently accurate that cutter marks meet the surface roughness requirements for general applications, except for special applications such as sealing surfaces in high-vacuum and ultra-high-vacuum equipment. However, because these cutter marks are easily visible to the naked eye, they can be problematic from an aesthetic standpoint. In such cases, manual tools such as random sanders (described below) are often used to polish the surface.

[0003] Patent Document 1 discloses a so-called random sander tool, a manual polishing machine in which an abrasive such as sandpaper pressed against a workpiece revolves around a motor and rotates around an eccentric shaft to polish the workpiece. Patent Document 2 discloses a polishing tool primarily intended for mirror-finishing molds. This polishing tool can be attached to the rotating spindle of a machine tool and can be replaced using an automatic tool changer (ATC). Like the random sander tool disclosed in Patent Document 1, Patent Document 2 discloses a tool and processing method in which a grinding stone held on an output shaft revolves around an input shaft and rotates around an eccentric output shaft, so that even if abrasive grains protrude from other abrasive grains, the abrasive grains do not leave scratches on the workpiece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-046052 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-138962 Summary of the Invention [Problem to be solved by the invention]

[0005] The random sander tool described in Patent Document 1 is a manual tool that an operator holds by hand to polish a workpiece. Random sanders, by combining rotation and revolution irregularly, can produce a uniform surface without transferring the surface condition of the abrasive to the machined surface. However, polishing a workpiece with a handheld random sander requires the operator to either enter the machining chamber of the machine tool or remove the workpiece from the chamber. Either method requires the machine tool to be stopped, which is inefficient. Furthermore, the dust generated during polishing creates a poor working environment, requiring the operator to wear personal protective equipment such as safety glasses and a protective mask. Furthermore, if polishing is performed outside the machining chamber, the dispersed dust must be cleaned up. Furthermore, in the random sander described in Patent Document 1, the polishing pad is attached to a bearing via an adapter and connected to a revolving motor via the bearing, resulting in a small pressing force. Therefore, it is difficult for the operator to apply the appropriate pressing force to keep the pad rotating. This can lead to excessive pad pressure, which can cause the pad to stop rotating and result in an inconsistent surface, or conversely, insufficient pad pressure, resulting in insufficient polishing.

[0006] The tool described in Patent Document 2 allows for automatic tool change on a machine tool. It has an input shaft driven by the machine tool's rotating spindle, an output shaft connected to the input shaft by a frictional connection, and an eccentric output shaft with an adjustable eccentricity. The grinding wheel is held on the output shaft, and similar to the random sander described in Patent Document 1, the grinding wheel held on the output shaft rotates and revolves irregularly, resulting in a uniform machined surface. Because the frictional connection transmits power from the input shaft to the output shaft, forcing the grinding wheel to rotate, there is no instability in the rotation of the output shaft. Unlike Patent Document 1, the tool can be used for polishing without operator intervention, all the way to the end. However, the input and output shafts of this tool are connected by a frictional connection consisting of a large-diameter portion and a rubber ring. The rubber ring wears due to friction, so it requires periodic replacement to limit its lifespan. Even with periodic replacement, there is a problem: the rubber ring may break during polishing, preventing proper polishing.

[0007] The present invention has as its technical object to solve the problems of the prior art, and aims to provide a polishing tool that has no frictional connection part, requires almost no maintenance, and can stably impart revolution and rotation to the polishing tool on a machine tool, thereby obtaining a uniform machined surface. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, according to the present invention, there is provided a polishing tool for polishing a workpiece, which is attached to a tool holder that is replaceably attached to a rotating spindle of a machine tool, the polishing tool comprising: a tool shank that is attached to the tool holder and rotates together with the rotating spindle about a first axis; an eccentric member that is attached to the tool shank and has a second axis that is parallel to and eccentric to the first axis; a connecting member that is attached to the eccentric member via a bearing and is rotatable about the second axis; and a polishing member that is attached to the connecting member with a gap between it and the eccentric member and rotates together with the connecting member about the second axis; and when the rotating spindle rotates, the polishing member revolves around the first axis and rotates about its own axis. [Effects of the Invention]

[0009] According to the polishing tool of the present invention, a gap is provided between the eccentric member and the polishing member, so that the pressing force of the polishing tool against the workpiece can be easily adjusted without using a replaceable part such as a rubber ring as a frictional connection. This allows a stable irregular combination of rotation and revolution to be provided, thereby enabling a uniform machined surface to be obtained by the machine tool. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an abrasive tool of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a machine tool equipped with a polishing tool. [Figure 3] This is a cross section taken along line III-III in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a polishing tool according to an embodiment will be described with reference to the accompanying drawings. Similar or corresponding elements are designated by the same reference numerals, and duplicated explanations will be omitted. For ease of understanding, the scale of the drawings may be changed.

[0012] FIG. 1 illustrates an example of a polishing tool according to the present invention. In FIG. 1, the polishing tool 100 is held by a spindle 310 of a machine tool 300 via a tool holder 200 that holds a tool shank 10. The polishing tool 100 also includes the tool shank 10, which rotates about a first axis A when the spindle rotates; an eccentric member 20 having a second axis B that is parallel to and eccentric with the first axis A; a connecting member 30 attached to the eccentric member 20 via a bearing 32 and rotatable about the second axis B; a disk-shaped pad 60 attached to the connecting member 30 via four bolts 40; and a polishing element 70 affixed to the pad 60. In the present invention, the pad 60 and the polishing element 70 are collectively referred to as the polishing member. The tool holder 200 conforms to the standard of the spindle taper of the spindle 310, and has a shape such as a 7 / 24 taper BT shank or a 1 / 10 taper HSK shank.

[0013] The eccentric member 20 has an adjustable eccentricity and is fixed to the tool shank 10 by an eccentric member holder 24. The eccentric member 20 and bearing 32 are fixed by an injection member 50. The injection member 50 fits into a recess 64 in the pad 60, with a gap 52 between them. This gap 52 ensures that the revolving portion (described later) is always free to rotate via the bearing 32 without contacting the rotating portion. An elastic member 42, made of a coil spring, is disposed between the connecting member 30 and the pad 60, with a bolt 40 passing through its center, and serves as a cushion. While a coil spring is illustrated as the elastic member 42, it may also be a disc spring or a cylindrical elastomer. The pad 60 itself has a certain degree of flexibility and functions as a cushion together with the elastic member 42. The injection member 50 and the recess 64 are spaced apart so that the gap 52 remains constant even when the elastic member 42 and the pad 60 are deformed. Details will be described later.

[0014] Referring to FIG. 2, a machine tool (e.g., a vertical machining center) 300 includes a bed 302 as a base fixed to the floor of a factory or the like; a table 320, which is movable in the X-axis direction (perpendicular to the plane of the paper in FIG. 2) on the upper surface of the bed 302 and to which a workpiece W is fixed; a column 304 fixed to the rear end of the bed 302 (inward, perpendicular to the plane of the paper in FIG. 2); a Y-axis slider 306 movable in the Y-axis direction in front of the column 304; a spindle head 308 movable in the Z-axis direction in front of the Y-axis slider 306; and a rotating spindle 310 attached to the spindle head 308. The machine tool 300 also includes an ATC unit 330, which enables automatic tool change. Additionally, the machine tool 300 includes an NC device (not shown) that performs the control required for a machining center, such as issuing operation commands to servo motors, which are the feed devices for the X, Y, and Z axes, rotation commands to the rotating spindle 310, and tool change commands to the ATC unit 330.

[0015] The above-mentioned components of the machine tool 300 are enclosed by a splash guard 400, and machining is performed in a particularly sealed machining chamber 410. The splash guard 400 is equipped with a mist collector 412 for collecting mist, chips, and dust generated inside the machining chamber 410. It is also equipped with one or more coolant nozzles 414, which can supply coolant to desired points such as the tip of the workpiece W or the polishing tool 100, or can supply coolant to the entire machining chamber 410 as a ceiling shower. The supplied coolant is collected in a coolant tank (not shown), filtered, and reused.

[0016] In this embodiment, high-pressure air generated by compressor 340 is used as the fluid. The high-pressure air generated by compressor 340 is supplied to machine tool 300 via fluid piping 342. Fluid piping 342 is equipped with a valve 344, and the flow rate and / or pressure of the fluid can be adjusted manually or by commands from an NC device. The high-pressure air supplied to machine tool 300 is supplied to rotary spindle 310, and then supplied to tool holder 200 through tool holder fluid passage 202. Although the tool holder fluid passage 202 is illustrated as being of a through-spindle type that passes through the interior of the rotary spindle, it may also be of a tool-through type that passes through a well-known positioning block (not shown) that does not rotate together with the rotary spindle.

[0017] Fluid is supplied to the polishing tool 100 from the rotating spindle 310 via the tool holder 200. The fluid is supplied to the injection member 50 via the tool shank fluid passage 12 provided in the tool shank 10 and the eccentric member fluid passage 22 provided in the eccentric member 20. At this time, the tool shank fluid passage 12 has a throttle 14, which makes it possible to adjust the flow rate of the fluid supplied to the injection member 50.

[0018] Referring to FIG. 3, fluid supplied to the injection member 50 is injected from the injection port 54 as indicated by the arrow. The injected fluid passes through the gap 52 and presses against the pressure-receiving surface 62 provided in the recess 64 of the pad 60. In FIG. 3, the injection port 54 is provided perpendicular to the second rotation axis B and the pressure-receiving surface 62 is provided on a surface parallel to the second rotation axis B. However, the injection port 54 may be provided parallel to the second rotation axis B and the pressure-receiving surface 62 may be provided on a surface perpendicular to the second rotation axis B (i.e., a downward surface when referring to FIG. 1). The polishing element 70 is disc-shaped like the pad 60, and can be removed from and replaced with a new one. The polishing element 70 can be selected from sandpaper, waterproof abrasive paper, a polishing buff, or the like, depending on the desired surface condition.

[0019] The operation of this embodiment will be described below. As described above, after the surface of the workpiece W is machined using an end mill or face mill on the machine tool 300, the polishing tool 100 is attached to the rotating spindle 310 by the ATC unit 330. After the polishing tool 100 is attached, the rotating spindle 310 receives a rotation command from the NC device and rotates at a predetermined rotational speed. As the rotating spindle 310 rotates, the tool shank 10, the orifice 14, the eccentric member 20, the injection member 50, and the inner ring 32a of the bearing 32 (hereinafter referred to as the revolving part) of the polishing tool 100 begin to rotate (revolve) around the first rotation axis A. As a result, similar to the random sander tool of Patent Document 1, the connecting member 30, the outer ring 32b of the bearing 32, the bolt 40, the elastic member 42, the pad 60, and the polishing element 70 (hereinafter referred to as the rotating part) begin to rotate (spin) around the second rotation axis B in conjunction with the revolving part.

[0020] Because the rotating part is connected to the revolving part via bearings 32 and gap 52 without a mechanical transmission mechanism, the rotation speed is not controlled, unlike the revolution speed, which can be controlled by an NC device. Furthermore, friction slows the rotation speed when the rotating part comes into contact with the workpiece surface, but this friction varies depending on factors such as the original rotation speed, the contact area with the workpiece surface, the type of abrasive used in the polishing elements 70, and the pressing force against the workpiece, causing the rotation speed to vary even more irregularly. This results in an irregular combination of revolution around the first rotation axis A and rotation around the second rotation axis B, which prevents the surface condition of the polishing elements 70 from being transferred to the workpiece surface, resulting in a uniformly polished surface.

[0021] In this way, the polishing tool 100 attached to the rotating spindle 310 operates, and the workpiece W and the polishing tool 100 move relative to each other in response to commands from the NC device of the machine tool 300, polishing the surface of the workpiece W. The surface to be polished is not limited to a flat surface; the flexibility of the pad 60 makes it possible to polish a curved surface with a relatively large curvature. Furthermore, even if the surface is flat, it can be polished even if it is inclined to some extent toward the second rotation axis B by individually deforming the multiple (four in the example of Figure 1) arranged elastic members 42.

[0022] Furthermore, since the rotational part does not transmit revolution as described above, even if the polishing tool 100 continues to revolve around the first rotation axis A by the rotation spindle 310, if the friction between the workpiece W and the polishing elements 70 increases, the rotation will stop and only the revolution by the rotation spindle 310 will remain. This is not desirable because the surface condition of the polishing elements 70 will be directly transferred to the processed surface. Therefore, it is necessary to properly set several elements described below so that the rotation of the polishing tool 100 does not stop.

[0023] The factors that determine the rotation speed of the polishing tool 100 include the rotation speed of the spindle 310, the amount of eccentricity between the first rotation axis A and the second rotation axis B changed by the eccentric member 20, the type of polishing elements 70 used, the rolling resistance of the bearings 32, the mass of the rotating part, and the pressing force of the polishing tool 100 against the workpiece W. These are determined by performing preliminary processing, taking into consideration the material of the workpiece W, the contact area between the polishing elements 70 and the surface to be processed (i.e., the size of the polishing elements 70), the condition of the surface before processing, the desired surface condition, etc. However, of the factors listed above, only two can be adjusted after the polishing tool 100 is attached to the machine tool 300: the rotation speed of the spindle 310 and the pressing force, which is adjusted by the amount of cut of the polishing tool 100 in the Z-axis direction.

[0024] The amount of cut in the Z-axis direction is difficult to adjust because, if the amount of cut is small, the workpiece W and the polishing element 70 do not come into contact, preventing polishing. If the amount of cut is large, the pressing force increases, resulting in excessive friction and causing the polishing element 70 to stop rotating. However, the polishing tool 100 has a flexible elastic member 42 and pad 60, which can absorb some of the movement of the polishing tool 100 in the Z-axis direction. This widens the range of the amount of cut in the Z-axis direction required to maintain an appropriate pressing force, making adjustment easier. Furthermore, even when the elastic member 42 is in its most compressed state, the gap 52 between the injection member 50 and the recess 64 prevents the revolution from being transmitted to the rotating part.

[0025] The gap 52 is provided so that the revolution is not transmitted to the rotating part, and so that the injection member 50 and the recessed portion 64 do not come into contact with each other. Specifically, even if the flexible elastic member 42 and the pad 60 are elastically deformed (either by compression or tension) to the maximum, the injection member 50 and the recessed portion 64 do not come into contact with each other. Furthermore, as described above, in order to polish a work surface inclined with respect to the second rotation axis B, even if the multiple elastic members 42 arranged are individually deformed, the injection member 50 and the recessed portion 64 do not come into contact with each other.

[0026] Fluid supplied from the rotation main shaft 310 is injected into the gap 52 from the injection port 54 provided in the injection member 50. When the injection port 54 is provided perpendicular to the second rotation axis B and the pressure-receiving surface 62 is provided on a surface parallel to the second rotation axis B as shown in Figure 3, the injected fluid passes through the gap 52 and presses the pressure-receiving surface 62 provided in the recess 64 of the pad 60, generating pressure in the pad 60. The pressure generated at this time assists rotation around the second rotation axis B due to the shape of the pressure-receiving surface 62.

[0027] When the injection port 54 is provided parallel to the second rotation axis B and the pressure-receiving surface 62 is provided on a surface perpendicular to the second rotation axis B (i.e., the downward surface when referring to Figure 1), the injected fluid assists in pressing the pad 60 and the polishing element 70 against the workpiece W.

[0028] In either of the above forms, the fluid can assist the pressing force of the revolving part against the workpiece W or the rotation thereof. This allows the revolution of the revolving part to be adjusted to some extent by adjusting the flow rate and / or pressure of the fluid with valve 344, and therefore can be used as one of the elements for adjusting the rotation speed of polishing tool 100 after polishing tool 100 is attached to machine tool 300.

[0029] In addition, in either of the above forms, the fluid injected from the injection member 50 prevents the gap 52 from being clogged with chips or dust. This maintains the proper rotation of the revolving part and the rotating part, eliminating instability caused by excessive or insufficient pressing force of the abrasive material against the workpiece.

[0030] In addition, the polishing elements 70 can be made of a variety of commercially available abrasives, such as sandpaper, waterproof abrasive paper, and polishing buffs, and can be used to polish the workpiece W according to its material and the desired surface. This polishing is performed inside the splash guard 400 and is sucked in by the mist collector 412, preventing dust from scattering and worsening the factory environment, and eliminating the need for workers to wear additional personal protective equipment. Coolant can also be supplied to desired points, such as the workpiece W or the tip of the polishing tool 100, by using the coolant nozzles 414, and can also be supplied to the entire processing chamber 410 as a ceiling shower, washing away dust and facilitating cleaning after polishing.

[0031] While preferred embodiments of the present invention have been described, the present invention is not limited thereto, and various modifications and improvements are possible within the scope of the present invention as defined in the claims. For example, in the above-described embodiment, machine tool 300 is a vertical machining center having three orthogonal axes (X, Y, and Z). However, the present invention is not limited thereto. For example, the machine tool may be a four-axis vertical machining center having a rotatable C-axis in table 320, or a rotary table mounted on table 320 and having a B-axis. It may also be a five-axis vertical machining center having a swivel axis on the main rotary spindle side. Similarly, the machine tool may be a horizontal machining center having various axis configurations.

[0032] In the above-described embodiment, the fluid supplied to the polishing tool 100 is high-pressure air generated by the compressor 340, but it may be coolant liquid supplied from a pump (not shown) installed in a coolant tank. The point is that it is sufficient to prevent dust from accumulating in the gap 52 and to apply pressure to the pressure-receiving surface 62. [Explanation of symbols]

[0033] 10 Tool holder 20 Eccentric member 30 Connecting member 32 Bearings 42 Cushioning material 50 Injection member 60 pads 70 Polishing Elements 100 Polishing tools 200 tool holder 300 Machine tools 310 Rotating spindle

Claims

1. A polishing tool attached to a tool holder that is replaceably mounted on a rotary spindle of a machine tool and that polishes a workpiece, comprising: a tool shank attached to the tool holder and configured to rotate together with the rotation spindle about a first axis; an eccentric member attached to the tool shank and having a second axis parallel to and eccentric to the first axis; a connecting member attached to the eccentric member via a bearing and rotatable about the second axis; a polishing member attached to the connecting member so as to have a gap with the eccentric member and rotate around the second axis together with the connecting member; wherein, when the rotation main shaft rotates, the polishing member revolves around the first axis and rotates around the second axis.

2. 2. The tool of claim 1, further comprising a resilient member disposed between said connecting member and said abrasive member, said resilient member being displaceable in said second axial direction.

3. 2. The polishing tool according to claim 1, further comprising an injection member provided on the eccentric member for injecting a fluid supplied from the rotation spindle through the tool holder and the tool shank into the gap.

4. 4. The polishing tool according to claim 3, further comprising a pressure-receiving surface formed on the polishing member, the pressure-receiving surface being hit by the fluid ejected from the ejection member.

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