JP7775391B1 - polishing tools - Google Patents

Abstract

A polishing tool is provided that is used in a machine tool and can give a polishing member a motion that irregularly combines revolution and rotation without having a frictional connection portion, thereby obtaining a uniform machined surface.
[Solution] A polishing tool (100) is held by a rotating spindle (310) of a machine tool (300), and has a first axis of rotation (A) caused by the rotation of the rotating spindle (310) and a second axis of rotation (B) eccentric to the first axis of rotation (A). The polishing members (60, 70) are attached to the tip of a rotating part that is connected to an orbital part that rotates with the rotating spindle (310) via a bearing (32) and a gap (52) without a mechanical transmission mechanism. The polishing members (60, 70) perform a movement in which revolution around the first axis of rotation (A) and rotation around the second axis of rotation (B) are irregularly combined, thereby enabling the workpiece to be machined with a uniform machined surface.
[Selected Figure] Figure 1

Description

The present invention relates to a polishing tool that is attached to the rotating spindle of a machine tool.

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. If the width of the surface to be finished is greater than the tool's rotational diameter, the tool's Z-axis (axial) position is not changed, but a pick feed is applied to move it laterally relative to the cutting 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, the surface is often polished using a manual tool such as a random sander, as described below.

Patent Document 1 discloses a so-called random sander tool, a manual polishing machine that polishes a workpiece by pressing an abrasive such as sandpaper against the workpiece and rotating it around an eccentric shaft while being driven by a motor. 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). Similar to the random sander tool disclosed in Patent Document 1, the tool disclosed in Patent Document 2 has a grinding stone held on an output shaft that revolves around an input shaft and rotates around an eccentric output shaft. This tool and processing method discloses that, even if abrasive grains protrude from other abrasive grains, the abrasive grains do not leave scratches on the workpiece.

Japanese Patent Application Laid-Open No. 2002-046052 JP 2014-138962 A

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, 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 by polishing creates a poor working environment, requiring operators to wear personal protective equipment such as safety glasses and a protective mask. Furthermore, if polishing is performed outside the machining chamber, the scattered 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 motor that revolves via the bearing, resulting in a small pressure margin. This makes it difficult for the worker to apply the appropriate amount of pressure to keep the pad rotating, and the pad may be pressed too hard, causing it to stop rotating and preventing a uniform polished surface, or conversely, not being pressed enough to achieve sufficient polishing.

The tool in Patent Document 2 allows for automatic tool replacement on a machine tool. It has an input shaft driven by the machine tool's rotating spindle, an eccentric output shaft connected to the input shaft by a frictional connection, and an eccentric output shaft with an adjustable eccentricity. A grinding wheel is held on the output shaft. As with the random sander tool in Patent Document 1, the grinding wheel held on the output shaft moves through an irregular combination of rotation and revolution, 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 all processes, from tool replacement to polishing, without operator intervention. 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 reduce its lifespan. Even with periodic replacement, there is a problem: the rubber ring may break during polishing, preventing proper polishing.

The technical objective of this invention is to solve these problems of the prior art, and to provide a polishing tool that has no frictional connection parts, requires almost no maintenance, and can stably impart revolution and rotation to the polishing tool on a machine tool, thereby producing a uniform machined surface.

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 mounted on 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 rotatable about the second axis; a polishing member that is attached to the connecting member so as to have a gap with the eccentric member and rotates together with the connecting member about the second axis; and an injection member that is provided on the eccentric member and injects fluid that is supplied from the rotating spindle through the tool holder and the tool shank into the gap; and when the rotating spindle rotates, the polishing member revolves around the first axis and rotates about its own axis.

The polishing tool of the present invention provides a gap between the eccentric member and the polishing member, making it easy to adjust the pressure of the polishing tool against the workpiece without the need for replaceable parts such as rubber rings that act as frictional connections. This allows the machine tool to stably produce an irregular combination of rotation and revolution, resulting in a uniform machined surface.

1 is a cross-sectional view of an abrasive tool of the present invention. FIG. 1 is a schematic diagram of a machine tool equipped with a polishing tool. This is a cross section taken along line III-III in FIG.

Abrasive tools according to embodiments will be described below with reference to the accompanying drawings. Similar or corresponding elements will be given the same reference numerals, and duplicate explanations will be omitted. The scale of the drawings may be changed to facilitate understanding.

Referring to Figure 1, an example of a polishing tool of the present invention is illustrated. In Figure 1, the polishing tool 100 is held by a rotating spindle 310 of a machine tool 300 via a tool holder 200 that holds the tool shank 10. The polishing tool 100 also includes the tool shank 10, which rotates about a first axis A with the rotation of the rotating spindle; 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 this 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.

The eccentric member 20 has an adjustable eccentricity and is fixed to the tool shank 10 by an eccentric member retainer 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 below) is always free to rotate via the bearing 32 without coming into contact with the rotating portion. The elastic member 42, a coil spring, is positioned between the connecting member 30 and the pad 60, with the bolt 40 passing through its center, and serves as a cushion. While a coil spring is shown as an example of 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 recess 64 are spaced apart so that the gap 52 remains constant even when the elastic member 42 and pad 60 are deformed. Details will be described later.

Referring to Figure 2, a machine tool (e.g., a vertical machining center) 300 comprises a bed 302 as a base fixed to the floor of a factory or the like; a table 320 movable in the X-axis direction (perpendicular to the plane of the paper in Figure 2) on the top surface of the bed 302 and on which a workpiece W is fixed; a column 304 fixed to the rear end of the bed 302 (perpendicular to the plane of the paper in Figure 2, toward the back); 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 has an ATC unit 330, enabling automatic tool change. In addition, the machine tool 300 has an NC unit (not shown) that performs the controls required for a machining center, such as issuing operation commands to the servo motors that act as feed devices for each of the X, Y, and Z axes, rotation commands to the rotating spindle 310, and tool change commands to the ATC unit 330.

The above-mentioned components of the machine tool 300 are enclosed by a splash guard 400, and machining is carried out 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 workpiece W or the tip of 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.

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 fluid flow rate and/or pressure can be adjusted manually or by command from an NC device. The high-pressure air supplied to machine tool 300 is supplied to the rotating spindle 310 and then to tool holder 200 through tool holder fluid passage 202. While the tool holder fluid passage 202 is illustrated as being of the through-spindle type that passes through the inside of the rotating spindle, it may also be of the tool-through type that passes through a well-known positioning block (not shown) that does not rotate with the rotating spindle.

The polishing tool 100 is supplied with fluid 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. The tool shank fluid passage 12 has a throttle 14, which allows the flow rate of fluid supplied to the injection member 50 to be adjusted.

Referring to Figure 3, fluid supplied to the injection member 50 is ejected from the injection nozzle 54 as shown by the arrow. The ejected fluid passes through the gap 52 and presses against the pressure-receiving surface 62 provided in the recess 64 of the pad 60. In Figure 3, the injection nozzle 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 nozzle 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 Figure 1). The polishing element 70 is disc-shaped like the pad 60, and can be removed and replaced from the pad 60. The polishing element 70 can be selected from sandpaper, waterproof abrasive paper, abrasive buffs, etc., depending on the desired surface condition.

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.

The rotating part is connected to the revolving part via bearings 32 and gap 52 without a mechanical transmission mechanism, so the rotation speed is not controlled, unlike the revolution speed, which can be controlled by an NC device. Furthermore, when it comes into contact with the workpiece's machining surface, it slows down due to friction, but this friction varies depending on factors such as the original rotation speed, the contact area with the machining surface, the type of abrasive used in the polishing element 70, and the pressing force against the workpiece, causing the rotation speed to change 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 allows for a uniform machined surface to be obtained without transferring the surface condition of the polishing element 70 to the machined surface.

In this way, the polishing tool 100 attached to the rotating spindle 310 operates, and the workpiece W and 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 flat surfaces; the flexibility of the pad 60 makes it possible to polish surfaces with a fairly 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.

Furthermore, since revolution is not transmitted to the rotating part as described above, even if the polishing tool 100 continues to be revolved around the first rotation axis A by the rotating spindle 310, if the friction between the workpiece W and the polishing element 70 becomes large, the rotation will stop and only the rotation by the rotating spindle 310 will remain. In this case, the surface condition of the polishing element 70 will be directly transferred to the processed surface, which is not desirable. Therefore, it is necessary to properly set several elements described below to prevent the rotation of the polishing tool 100 from stopping.

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, which is changed by the eccentric member 20, the type of polishing element 70 used, the rolling resistance of the bearing 32, the mass of the rotating part, and the pressing force of the polishing tool 100 against the workpiece W. These are determined through preliminary processing, taking into account the material of the workpiece W, the contact area between the polishing element 70 and the processing surface (i.e., the size of the polishing element 70), the condition of the surface before processing, and the desired surface condition. 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 cutting of the polishing tool 100 in the Z-axis direction.

The amount of cut in the Z-axis direction is difficult to adjust; if the amount of cut is too small, the workpiece W and polishing element 70 will not come into contact and polishing will not be possible, while if the amount of cut is too large, the pressing force will increase, causing excessive friction and stopping the rotation of the polishing element 70. However, because the polishing tool 100 has a flexible elastic member 42 and pad 60, it 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, there is a gap 52 between the injection member 50 and the recess 64, so revolution is not transmitted to the rotating part.

The gap 52 is provided so that the injection member 50 and the recessed portion 64 do not come into contact with each other, as it does not transmit the revolution to the rotating portion. Specifically, the gap 52 is provided so that the injection member 50 and the recessed portion 64 do not come into contact with each other, even when the flexible elastic member 42 and the pad 60 are elastically deformed to their maximum (either by compression or tension). Also, as mentioned above, in order to polish a work surface that is inclined with respect to the second rotation axis B, the gap 52 is provided so that the injection member 50 and the recessed portion 64 do not come into contact with each other, even when the multiple elastic members 42 are individually deformed.

Fluid supplied from the main rotation axis 310 is injected into the gap 52 from the injection port 54 provided in the injection member 50. As shown in Figure 3, if 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, 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, generating pressure on the pad 60. Depending on the shape of the pressure-receiving surface 62, the pressure generated at this time assists rotation around the second rotation axis B.

When the injection port 54 is parallel to the second rotation axis B and the pressure-receiving surface 62 is located 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 polishing elements 70 against the workpiece W.

In either of the above configurations, the fluid can assist the pressing force of the revolving part against the workpiece W or the rotation. 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 using valve 344, and can therefore be used as one of the elements for adjusting the rotation speed of polishing tool 100 after it has been attached to machine tool 300.

In addition, regardless of which of the above configurations is used, the fluid sprayed from the spray member 50 prevents the gap 52 from becoming clogged with chips or dust. This maintains proper rotation of the revolving part and the rotating part, eliminating instability caused by excessive or insufficient pressure being applied to the abrasive material against the workpiece.

The polishing element 70 can be made with a variety of commercially available abrasives, such as sandpaper, waterproof abrasive paper, and polishing buffs, to suit the material of the workpiece W and the desired surface to be polished. Furthermore, this polishing is performed within the splash guard 400 and is sucked in by the mist collector 412, preventing dust from scattering and deteriorating the factory environment, and eliminating the need for workers to wear additional personal protective equipment. In addition, the coolant nozzle 414 supplies coolant to desired points, such as the workpiece W or the tip of the polishing tool 100, and coolant can also be supplied to the entire processing chamber 410 as a ceiling shower, washing away dust and facilitating cleaning after polishing.

While a preferred embodiment of the present invention has been described, the present invention is not limited to this, and various modifications and improvements are possible within the scope of the present invention as defined in the claims. For example, in the embodiment described above, the machine tool 300 is a vertical machining center with three orthogonal axes: X, Y, and Z. However, the present invention is not limited to this. For example, the machine tool may be a four-axis vertical machining center in which the table 320 has a rotatable C-axis, or in which the table 320 is equipped with a rotary table and has a B-axis. It may also be a five-axis vertical machining center with a swivel axis on the rotating spindle side. Similarly, the machine tool may be a horizontal machining center with various axis configurations.

In the previously described embodiment, the fluid supplied to the polishing tool 100 is high-pressure air generated by the compressor 340, but it may also be coolant liquid supplied from a pump (not shown) installed in a coolant tank. The key is to prevent dust from accumulating in the gap 52 and to apply pressure to the pressure-receiving surface 62.

REFERENCE SIGNS LIST 10 Tool holder 20 Eccentric member 30 Connecting member 32 Bearing 42 Cushioning member 50 Injection member 60 Pad 70 Polishing element 100 Polishing tool 200 Tool holder 300 Machine tool 310 Rotating spindle

Claims (3)

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;
an injection member provided on the eccentric member and configured to inject fluid supplied from the rotation spindle through the tool holder and the tool shank into the gap;
wherein, when the rotation main shaft rotates, the polishing member revolves around the first axis and rotates around the second axis. The tool described in claim 1, further comprising an elastic member between the connecting member and the polishing member that is displaceable in the second axial direction. 2. The polishing tool according to claim 1 , 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.