CN110936285A - Grinding machine and grinding method - Google Patents

Grinding machine and grinding method Download PDF

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Publication number
CN110936285A
CN110936285A CN201910891708.3A CN201910891708A CN110936285A CN 110936285 A CN110936285 A CN 110936285A CN 201910891708 A CN201910891708 A CN 201910891708A CN 110936285 A CN110936285 A CN 110936285A
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CN
China
Prior art keywords
grinding
workpiece
pressure
clamping force
chuck
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201910891708.3A
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Chinese (zh)
Inventor
疋田雅也
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JTEKT Corp
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JTEKT Corp
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Filing date
Publication date
Application filed by JTEKT Corp filed Critical JTEKT Corp
Publication of CN110936285A publication Critical patent/CN110936285A/en
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B5/00—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor
    • B24B5/02—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work
    • B24B5/04—Machines or devices designed for grinding surfaces of revolution on work, including those which also grind adjacent plane surfaces; Accessories therefor involving centres or chucks for holding work for grinding cylindrical surfaces externally
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/02—Lapping machines or devices; Accessories designed for working surfaces of revolution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/005—Control means for lapping machines or devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/005—Control means for lapping machines or devices
    • B24B37/013—Devices or means for detecting lapping completion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/27—Work carriers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B41/00—Component parts such as frames, beds, carriages, headstocks
    • B24B41/007—Weight compensation; Temperature compensation; Vibration damping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B41/00—Component parts such as frames, beds, carriages, headstocks
    • B24B41/06—Work supports, e.g. adjustable steadies
    • B24B41/061—Work supports, e.g. adjustable steadies axially supporting turning workpieces, e.g. magnetically, pneumatically
    • B24B41/062—Work supports, e.g. adjustable steadies axially supporting turning workpieces, e.g. magnetically, pneumatically between centres; Dogs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B47/00—Drives or gearings; Equipment therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B47/00—Drives or gearings; Equipment therefor
    • B24B47/22—Equipment for exact control of the position of the grinding tool or work at the start of the grinding operation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/02—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent
    • B24B49/04—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent involving measurement of the workpiece at the place of grinding during grinding operation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/16—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation taking regard of the load
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B51/00—Arrangements for automatic control of a series of individual steps in grinding a workpiece

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Grinding Of Cylindrical And Plane Surfaces (AREA)
  • Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)

Abstract

The invention provides a grinding machine. A grinding machine (1) is provided with: a workpiece support device (10) that rotates a workpiece (W) about an axis; a grinding wheel (20) for grinding a workpiece (W); a feed drive device (60) that feeds at least one of the grinding wheel (20) and the workpiece support device (10) in a direction in which the grinding wheel (20) and the workpiece support device (10) are relatively moved toward and away from each other; a feed control unit (140) that controls the feed drive device (60) and that reduces the feed speed of at least one of the grinding wheel (20) and the workpiece support device (10) in accordance with the progress of grinding by the grinding wheel (20); and a chuck control unit (150) which controls the clamping force of the chuck (14b) on the workpiece (W) and reduces the clamping force from the first pressure (P1) to the second pressure (P2) when or after the feed speed is reduced.

Description

Grinding machine and grinding method
Technical Field
The invention relates to a grinding machine and a grinding method.
Background
During grinding by the grinding machine, the workpiece is supported on both sides in the axial direction. In this regard, japanese patent application laid-open No. 2018-24026 discloses a technique in which one end of a workpiece is supported by a headstock center and the other end of the workpiece is supported by a tailstock center. Further, japanese patent application laid-open No. 2018-24026 discloses a technique of suppressing deflection of a workpiece due to a tip pressing force by making the tip pressing force of a tailstock at the time of finish polishing smaller than the tip pressing force of the tailstock at the time of rough polishing.
Here, when the surface of the workpiece is polished, the stress remaining in the workpiece is released. In contrast, when the end of the workpiece is clamped by the chuck on the grinding machine, the workpiece is restrained from being bent due to the stress release of the workpiece, and the workpiece is bent by releasing the chuck.
In this regard, in conventional grinding, the grinding machine once loosens the chuck after finishing rough machining, and the workpiece is bent due to the stress relief of the workpiece. Then, the grinding machine re-clamps the workpiece by the chuck with a pressure smaller than that during rough machining so as to support the workpiece in a state where the workpiece is bent, and performs finish machining, thereby improving the machining accuracy of the machined workpiece. In this case, however, it is necessary to stop the grinding process while performing unclamping and reclamping of the chuck, and therefore cycle time efficiency is lowered.
Disclosure of Invention
The invention aims to provide a grinding machine and a grinding method which can maintain the machining precision of a workpiece and improve the cycle time efficiency.
A grinding machine according to one aspect of the present invention includes: a workpiece support device which has a chuck for clamping one end of a workpiece and a support part for supporting the other end of the workpiece and rotates the workpiece around an axis; a grinding wheel for grinding the workpiece; a feed driving device that feeds at least one of the grinding wheel and the work support device in a direction in which the grinding wheel and the work support device relatively approach or separate from each other; a feed control unit that controls the feed drive device to reduce a feed speed of at least one of the grinding wheel and the workpiece support device in accordance with a progress of grinding by the grinding wheel; and a chuck control unit that controls a clamping force of the chuck on the workpiece, and reduces the clamping force from a first pressure to a second pressure smaller than the first pressure when or after the feed speed is reduced.
In addition, a grinding machine is used as a grinding method according to another aspect of the present invention, and the grinding machine includes: a workpiece support device which has a chuck for clamping one end of a workpiece and a support part for supporting the other end of the workpiece and rotates the workpiece around an axis; a grinding wheel for grinding the workpiece; and a feed driving device that feeds at least one of the grinding wheel and the work support device in a direction in which the grinding wheel and the work support device relatively approach or separate from each other. The polishing method includes: a rough machining step of performing rough grinding of the workpiece by the grinding wheel; a finish machining step of performing finish machining by the grinding wheel on the workpiece subjected to the rough grinding in a state where a feed speed of at least one of the grinding wheel and the workpiece support device is lower than the rough machining step; and a first clamping force reduction step of reducing a clamping force of the chuck on the workpiece from a first pressure to a second pressure smaller than the first pressure at the end of the rough machining step or in the finish machining step.
According to the grinding machine and the grinding method of the above aspect, the chuck control unit reduces the clamping force when or after the feed speed is reduced. As a result, the workpiece supported by the workpiece support device is bent by the stress release. The grinding machine can improve the machining accuracy of the machined workpiece by grinding the workpiece supported by the workpiece support device in a state where the workpiece is bent.
That is, the grinding machine and the grinding method can grind a workpiece supported by the workpiece support device in a state where a bend due to stress relaxation occurs while avoiding unclamping and reclamping of the workpiece by the chuck. Therefore, the grinding machine and the grinding method can improve cycle time efficiency while maintaining the machining accuracy of the workpiece.
Drawings
Fig. 1 is a plan view of a grinding machine in an embodiment of the present invention.
Fig. 2 is a block diagram of the control device.
Fig. 3 is a flowchart showing a polishing process executed by the control device.
Fig. 4 is a graph showing a relationship between a time of decrease in the feed speed of the grinding wheel and a time of decrease in the clamping force of the chuck on the workpiece.
Fig. 5 is a graph showing a relationship between a time of decrease in the feed speed of the grinding wheel and a time of decrease in the clamping force of the chuck on the workpiece in the first modification.
Fig. 6 is a graph showing a relationship between a time of decrease in the feed speed of the grinding wheel and a time of decrease in the clamping force of the chuck on the workpiece in the second modification.
Fig. 7 is a graph showing a relationship between a time of reduction of the polishing load and a time of reduction of the clamping force of the chuck against the workpiece in the third modification.
Detailed Description
Next, an embodiment to which the grinding machine and the grinding method of the present invention are applied will be described with reference to the drawings. First, a grinding machine 1 as an embodiment of the present invention will be briefly described with reference to fig. 1.
As shown in fig. 1, the grinding machine 1 is a wheel slide type grinding machine that performs grinding while rotating a cylindrical workpiece W. The grinding machine 1 mainly includes: the machining center includes a bed 2, a work support device 10, a grinding wheel 20, a grinding wheel head 30, a table 40, a table drive device 50, a feed drive device 60, a coolant supply device 70, a dimension measurement device 80, and a control device 100 (see fig. 2).
The bed 2 is a part serving as a base of the grinding machine 1. An operation panel 3 for inputting various parameters related to the grinding conditions and the like is provided on the bed 2, and the operation panel 3 is operated by an operator. The work support device 10 rotates a long work W formed in a cylindrical shape about an axis while supporting both end portions in the axial direction (the left-right direction in fig. 1). The workpiece support device 10 mainly includes a headstock 11 and a tailstock 12.
The headstock 11 rotatably supports one axial end side (the right end in fig. 1) of the workpiece W. The headstock 11 includes: a headstock body 13 as a housing; a main spindle 14 rotatably supported by the headstock body 13 and movable in the Z-axis direction; and an active moving device 15 that moves the active spindle 14 in the Z-axis direction. Further, the headstock 11 is provided with a main drive motor 11a that rotationally drives the main drive shaft 14. The main spindle 14 is provided with a spindle center 14a as a support portion for supporting an end surface of the workpiece W on one axial end side, and a chuck 14b for clamping an outer peripheral surface of the workpiece W on one axial end side. The chuck 14b includes: a chuck body mounted on the main drive shaft 1; a plurality of claws provided rotatably or slidably to the chuck body; and a cylinder device for opening and closing the plurality of claws. The chuck 14b clamps or unclamps the workpiece W by moving the tips of the plurality of jaws in the radial direction.
The active movement device 15 includes: a slider 15a, a slider drive 15b, and a floating joint 15 c. The slider 15a is provided movably in the Z-axis direction with respect to the bed 2. Further, a guide rail 15d extending in the Z-axis direction is provided on the upper surface of the bed 2, and the slider 15a is guided by the guide rail 15d to move in the Z-axis direction. The slider driving device 15b is a screw feeding device that feeds the slider 15a in the Z-axis direction. The floating joint 15c connects the slider 15a and the drive spindle 14, and the drive spindle 14 moves in the Z-axis direction in accordance with the movement of the slider 15a in the Z-axis direction, allowing the rotation of the drive spindle 14 with respect to the joint 15 c.
The tailstock 12 mainly includes: a tailstock body 16 as a housing; a driven spindle 17 supported by the tailstock body 16 to be rotatable and movable in the Z-axis direction; and a driven moving device 18 that moves the driven main shaft 17 in the Z-axis direction. The tailstock 12 is provided with a driven motor 12a that rotates a driven spindle 17. Further, the driven spindle 17 is provided with a tailstock center 17a as a support portion for supporting an end surface of the other end side (end portion on the left side in fig. 1) in the axial direction of the workpiece W.
The driven movement device 18 includes: a slider 18a, a slider drive 18b, and a spring 18 c. The slider 18a is provided movably in the Z-axis direction with respect to the bed 2. Further, a guide rail 18d extending in the Z-axis direction is provided on the upper surface of the bed 2, and the slider 18a is guided by the guide rail 18d to move in the Z-axis direction. The slider drive device 18b is a screw feed device that feeds the slider 18a in the Z-axis direction with respect to the bed 2.
The spring 18c is disposed between the slider 18a and the joint 18 e. When the slave moving device 18 moves the slider 18a in a direction to approach the workpiece W, the slave spindle 17 is moved in a direction to approach the workpiece W while compressing the spring 18 c. The driven movement device 18 is provided with a stopper rod 18f that connects the slider 18a and the joint 18e, and when the slider 18a moves in a direction away from the workpiece W, the joint 18e moves in a direction away from the workpiece W (Z-axis direction) together with the driven spindle 17 while following the slider 18a while allowing rotation of the driven spindle 17.
Further, the workpiece support device 10 can suppress the occurrence of deflection of the workpiece W due to the center supporting force by adjusting the center supporting force from the main spindle center 14a and the tailstock center 17a by using the master moving device 15 and the slave moving device 18.
The grinding wheel 20 grinds the workpiece W supported by the workpiece support device 10. The wheel head 30 is provided with a wheel shaft member 31 and a wheel motor 32. The wheel spindle member 31 is supported rotatably about a rotation axis parallel to the Z axis with respect to the wheel head 30, and the grinding wheel 20 is provided rotatably integrally with the wheel spindle member 31 with respect to one end of the wheel spindle member 31. The grinding wheel motor 32 rotates the grinding wheel shaft member 31 via the belt and belt pulley mechanism 33 to rotate the grinding wheel 20.
A grinding wheel cover 34 for covering the grinding wheel 20 is provided on the upper surface of the grinding wheel holder 30. The grinding wheel cover 34 prevents the coolant supplied from the coolant supply device 70 to the grinding wheel 20 from scattering. The grinding machine 1 is provided with a grinding load detector 35 for detecting the current value of the wheel motor 32. That is, the grinding machine 1 detects the current value of the grinding wheel motor 32 as the grinding load, thereby detecting the grinding load generated when the grinding wheel 20 grinds the workpiece W.
The table 40 supports the wheel head 30. The table driving device 50 is a screw feeding device that feeds the table 40 in the Z-axis direction with respect to the bed 2. The feed driving device 60 is a screw feeder that feeds the wheel head 30 in the X-axis direction with respect to the table 40. In the grinding machine 1, the grinding wheel base 30 is fed in the X-axis direction with respect to the table 40, whereby the workpiece W supported by the workpiece support device 10 can be relatively moved toward and away from the grinding wheel 20. The feed drive device 60 is provided with an encoder 61 (see fig. 2) for detecting the position of the wheel slide 30 in the X-axis direction.
The coolant supply device 70 includes a coolant storage tank 71, a pump 72, and a coolant nozzle 73. The coolant reservoir tank 71 and the pump 72 are provided in the bed 2, and the coolant nozzle 73 is attached to the grinding wheel cover 34. The coolant supply device 70 pumps the coolant stored in the coolant storage tank 71 by a pump 72 and sends the coolant to a coolant nozzle 73 connected to the pump 72 by a pipe. The dimension measuring device 80 is provided on the upper surface of the bed 2. The dimension measuring device 80 is used for measuring the outer diameter of the workpiece W.
The control device 100 includes: a workpiece rotation control section 110, a grinding wheel rotation control section 120, a traverse control section 130, a feed control section 140, a chuck control section 150, and a tip support control section 160.
The workpiece rotation control unit 110 drives and controls the master motor 11a and the slave motor 12a to rotate and stop the rotation of the workpiece W supported by the workpiece support device 10. The grinding wheel rotation control unit 120 controls the driving of the grinding wheel motor 32 to rotate and stop the rotation of the grinding wheel 20. The traverse control section 130 drives and controls a table motor 51 provided in the table driving device 50 to move the table 40 in the Z-axis direction.
The feed control unit 140 drives and controls the feed motor 62 provided in the feed drive device 60 to feed the wheel stock 30 and the grinding wheel 20 in the X-axis direction. The feed control unit 140 includes a speed command unit 141 and a speed calculation unit 142. The speed command unit 141 sets a target feed speed of the wheel head 30 (hereinafter referred to as a "target feed speed"). The speed calculation unit 142 calculates the distance the wheel head 30 moves within a predetermined time by differentiating the position signal output from the encoder 61, and calculates the feed speed of the wheel head 30. The feed control unit 140 performs speed control of the feed motor 62 while performing feedback control of the feed speed so that the feed speed matches the target feed speed.
The chuck control section 150 controls the clamping force of the chuck 14b on the workpiece W. Specifically, the chuck 14b is provided with: a pump for discharging pressure oil; a switching valve selectively supplying pressure oil to a clamping chamber or a unclamping chamber of the cylinder device; and a pressure reducing valve that controls a pressure of the pressure oil, and the chuck control part 150 controls the clamping force by controlling the pressure of the pressure reducing valve. As described later, the chuck control unit 150 changes the clamping force from the chuck 14b according to the feed speed of the wheel slide 30. The center support control unit 160 controls the slide driving device 15b of the master moving device 15 and the slide driving device 18b of the slave moving device 18 to control the center support force from the spindle center 14a and the tailstock center 17 a.
Next, a polishing process performed by the control device 100 will be described with reference to fig. 3. The grinding process is a process executed when the grinding machine 1 grinds the workpiece W, and the feed control unit 140 reduces the feed speed of the grinding wheel 20 (wheel head 30) in accordance with the progress of grinding by the grinding wheel 20.
As shown in fig. 3, the grinding machine 1 performs a rough grinding step of roughly grinding the workpiece W, which has been subjected to the quenching treatment in advance, as a first process in the grinding process (S1). The grinding machine 1 performs grinding while measuring the outer diameter of the workpiece W by the dimension measuring device 80, and performs a rough machining step (S1) until the outer diameter of the workpiece W reaches a preset finish grinding diameter.
When the outer diameter of the workpiece W reaches the finish grinding diameter, the grinding machine 1 shifts to a first finish grinding step (S2) for finish grinding the workpiece W. In the first finishing step (S2), the feed controller 140 reduces the target feed speed of the wheel slide 30 to be lower than the target feed speed in the rough machining step (S1). As a result, in the first finishing step (S2), the feed speed of the wheel head 30 is reduced to be lower than that in the rough machining step (S1), and the depth of cut is smaller than that in the rough machining step (S1). Next, the grinding machine 1 performs the first finishing process (S2) until the outer diameter of the workpiece W reaches the preset fine grinding diameter.
When the outer diameter of the workpiece W reaches the fine grinding diameter, the grinding machine 1 switches to a second finishing step (S3) of finely grinding the workpiece W. In the second finishing process (S3), the feed control unit 140 reduces the target feed speed of the wheel slide 30 to be lower than the target feed speed in the first finishing process (S2). As a result, in the second finishing step (S3), the feed speed of the wheel head 30 is reduced to be lower than that in the first finishing step (S2), and the depth of cut is smaller than that in the first finishing step (S2). Then, the grinding machine 1 performs the second finishing process (S3) until the outer diameter of the workpiece W reaches the preset finished diameter.
When the outer diameter of the workpiece W reaches the finished diameter, the grinding machine 1 shifts to a spark-less grinding step (S4) of spark-less grinding of the workpiece W. In the sparkless grinding step (S4), the grinding machine 1 rotates the grindstone 20 while stopping the feed of the wheel carrier 30.
Here, the workpiece support device 10 supports the end surfaces of the workpiece W on both axial sides by the spindle center 14a and the tailstock center 17a, and supports the outer peripheral surface of the workpiece W on one axial end side by the chuck 14 b. In this regard, since the spindle center 14a and the tailstock center 17a simply support both end surfaces of the workpiece W, the deflection of the workpiece W cannot be sufficiently suppressed during the grinding process while the grindstone 20 is brought into contact with the workpiece W.
In contrast, the chuck 14b has a larger contact area with the workpiece W than the spindle center 14a and the tailstock center 17a, and fixedly supports the workpiece W from the outer peripheral surface. Therefore, the displacement of the workpiece W is suppressed at least in the range where the outer peripheral surface is supported by the chuck 14 b. The chuck 14b can firmly support the workpiece W, thereby suppressing the workpiece W from being deflected. As a result, the grinding machine 1 can suppress the deflection of the workpiece W when performing the grinding process while strongly abutting the grindstone 20 against the workpiece W, and thus can improve the processing accuracy of the workpiece W.
In addition, when the workpiece W that has been subjected to the quenching treatment in advance is subjected to the polishing process, the surface of the workpiece W is polished, whereby the stress remaining in the workpiece W is released. In this regard, with respect to the workpiece W, which is likely to bend due to the release of internal stress, the workpiece W is restrained from bending due to the release of stress in a state where the workpiece W is firmly supported by the chuck 14 b. Therefore, the grinding machine 1 needs to perform grinding work in a state where the bending due to the stress relaxation occurs, and maintain the machining accuracy of the machined workpiece W.
In contrast, when the feed speed of the grindstone 20 (grindstone seat 30) is reduced, the chuck control unit 150 reduces the clamping force of the chuck 14b on the workpiece W. Thereby, a bend caused by the internal stress released by the rough grinding is generated in the workpiece W supported by the workpiece support device 10. The grinding machine 1 grinds the workpiece W supported by the workpiece support device 10 in a state where the workpiece W is bent. This enables the grinding machine 1 to improve the machining accuracy of the workpiece W after the grinding process.
Here, the relationship between the feed speed of the grindstone 20 (grindstone seat 30) and the clamping force of the chuck 14b will be described with reference to fig. 4. In the graph shown in fig. 4, the time when the rough machining step (S1) ends is t1, the time when the first finishing step (S2) ends is t2, the time when the second finishing step (S3) ends is t3, and the clamping force of the chuck 14b in the rough machining step (S1) is a first pressure P1.
As shown in fig. 4, in the rough machining step (S1), when the outer diameter of the workpiece W reaches the finish grinding diameter, the feed control unit 140 decreases the feed speed of the grinding wheel 20 (wheel slide 30) to shift from the rough machining step to the first finish machining step. Then, the chuck control unit 150 decreases the clamping force of the chuck 14b on the workpiece W from the first pressure P1 to the second pressure P2(P1 > P2) as the feed speed of the wheel slide 30 decreases (first clamping force decreasing step).
Here, the workpiece W subjected to rough grinding is subjected to bending caused by the release of internal stress. That is, the workpiece W subjected to the quenching treatment as a pretreatment for the polishing process is polished to relieve the stress remaining in the workpiece W. However, in a state where the workpiece W is clamped to the chuck 14b with a clamping force exceeding a certain value, the bending of the workpiece W caused by the release of the internal stress is suppressed.
In addition, the grinding machine 1 has a large depth of cut in the rough machining step, and accordingly, it is necessary to increase the clamping force of the chuck 14b to the workpiece W. On the other hand, the depth of cut in the first finishing step (S2) is smaller than the depth of cut in the rough machining step (S1), and the polishing load applied to the workpiece W is reduced. Therefore, in the first finishing step, the chuck control unit 150 reduces the clamping force of the chuck 14b on the workpiece W to be lower than that in the rough machining step (S1) while maintaining the clamping force required in the first finishing step (S2). Then, the grinding machine 1 performs finish grinding of the workpiece W supported by the workpiece support device 10 in a state where the workpiece W is curved.
In the first finishing step (S2), when the outer diameter of the workpiece W reaches the fine grinding diameter, the feed controller 140 decreases the feed speed of the grinding wheel 20 (wheel carrier 30) from the second pressure P2 to the third pressure P3(P2 > P3) in order to switch from the first finishing step (S2) to the second finishing step (S3) (second clamping force decreasing step). The chuck control unit 150 decreases the clamping force of the chuck 14b on the workpiece W as the feed speed of the grinding wheel 20 decreases. When the outer diameter of the workpiece W reaches the finished diameter, the feed control unit 140 stops the feed of the wheel head 30 to switch to the sparkless polishing step (S4). Then, the chuck control unit 150 further reduces the clamping force of the chuck 14b on the workpiece W as the feed speed of the wheel slide 30 decreases.
As described above, the grinding machine 1 reduces the clamping force from the chuck 14b in steps in multiple times. Therefore, the grinding machine 1 can reduce the amount of reduction in the clamping force at each time, and thus can suppress adverse effects (generation of grinding burn and the like) on the grinding process that are caused by the reduction in the clamping force.
As described above, when the feed speed of the grindstone 20 (the wheel carrier 30) is reduced, the chuck control unit 150 reduces the clamping force of the chuck 14b on the workpiece W. Therefore, the grinding machine 1 can generate a curve caused by stress relief in the workpiece W supported by the workpiece support device 10. The grinding machine 1 can improve the machining accuracy of the workpiece W after machining by grinding the workpiece W supported by the workpiece support device 10 in a state where the workpiece W is curved.
That is, the grinding machine 1 can grind the workpiece W supported by the workpiece support device 10 in a state where the workpiece W is bent by the stress relief while avoiding unclamping and reclamping of the workpiece W by the chuck 14 b. Therefore, the grinding machine 1 can improve the cycle time while maintaining the machining accuracy of the workpiece W.
In the present embodiment, the grinding machine 1 performs a grinding process on the workpiece W subjected to the quenching process. The internal stress remaining inside the workpiece W subjected to the quenching treatment may become large, and the curvature generated in the workpiece W at the time of stress relief may become large. In contrast, in the grinding machine 1, when the feed speed of the grindstone 20 (the wheel carrier 30) is reduced, the clamping force of the chuck 14b on the workpiece W is reduced. Therefore, the grinding machine 1 can improve the machining accuracy of the workpiece W. Further, since the stress remaining inside the workpiece W formed by forging is also large, the grinding machine 1 can improve the machining accuracy of the workpiece W even when the workpiece W formed by forging is ground.
Next, a modified example of the time period for reducing the clamping force from the chuck 14b will be described. First, a first modification will be described with reference to fig. 5.
As shown in fig. 5, in the first modification, the chuck control unit 150 decreases the clamping force of the chuck 14b on the workpiece W after a predetermined time has elapsed since the feed speed of the wheel slide 30 was decreased. That is, the polishing load applied to the workpiece W supported by the workpiece support device 10 may rise immediately after the feed speed of the wheel slide 30 decreases.
In contrast, after a predetermined time has elapsed from the end of the rough machining step (S1), that is, in the first finishing step (S2), the grinding machine 1 reduces the clamping force of the chuck 14b on the workpiece W from the first pressure P1 to the second pressure P2. Similarly, after a predetermined time has elapsed from the end of the first finishing step (S2), that is, in the second finishing step (S3), the grinding machine 1 reduces the clamping force of the chuck 14b on the workpiece W from the second pressure P2 to the third pressure P3.
In this way, the grinding machine 1 can stably hold the workpiece W by reducing the clamping force of the workpiece W after the feed speed of the grinding wheel 20 (wheel head 30) is reduced and waiting until the grinding load is surely reduced. As a result, the grinding machine 1 can suppress adverse effects on the grinding process that occur with a decrease in the clamping force.
Next, a second modification will be described with reference to fig. 6. As shown in fig. 6, when the rough machining process (S1) is completed and the feed speed of the grindstone 20 (grindstone seat 30) is reduced, the grinding machine 1 gradually reduces the clamping force from the chuck 14b from the first pressure P1 to the second pressure P2. Specifically, the chuck control unit 150 gradually decreases the clamping force of the chuck 14b on the workpiece W from the start of the first finishing process (S2) to the end of the second finishing process (S3). In this case, since the grinding machine 1 can suppress adverse effects on the grinding process caused by the reduction of the clamping force, the machining accuracy of the workpiece W can be improved.
In the second modification, the chuck control unit 150 reduces the clamping force from the chuck 14b at a constant rate, but the present invention is not limited to this, and the rate of reduction of the clamping force may be changed with the passage of time.
Next, a third modification will be described with reference to fig. 7. In the third modification, the grinding machine 1 detects a grinding load generated during grinding, and when the grinding load is reduced with a reduction in the feed speed of the grinding wheel 20 (wheel head 30), reduces the clamping force of the chuck 14b against the workpiece W. Here, as a method of detecting the polishing load, in the third modification, the current value of the wheel motor 32 detected by the polishing load detector 35 (see fig. 2) is regarded as the polishing load, and the chuck control unit 150 reduces the clamping force of the chuck 14b against the workpiece W when the value (current value) of the polishing load detected by the polishing load detector 35 is reduced. As another method of detecting the polishing load, a method of detecting the current values of the drive motor 11a and the feed motor 62 and regarding the detected values as the polishing load is exemplified.
Specifically, in the rough machining step (S1), when the outer diameter of the workpiece W reaches the finish grinding diameter, the feed control unit 140 decreases the feed speed of the grindstone 20 (the wheel carrier 30) to switch from the rough machining step to the first finish machining step. Accordingly, when the polishing load decreases as the feed speed of the wheel slide 30 decreases, the chuck control unit 150 decreases the clamping force of the chuck 14b on the workpiece W from the first pressure P1 to the second pressure P2.
In the first finishing step (S2), when the outer diameter of the workpiece W reaches the fine grinding diameter, the feed controller 140 decreases the feed speed of the grindstone 20 (the wheel carrier 30) from the second pressure P2 to the third pressure P3 in order to switch from the first finishing step (S2) to the second finishing step (S3). When the polishing load decreases with a decrease in the feed speed of the grindstone 20, the chuck control unit 150 decreases the clamping force of the chuck 14b on the workpiece W. When the outer diameter of the workpiece W reaches the finished diameter, the feed control unit 140 stops the feed of the wheel head 30 to switch to the sparkless polishing step (S4). Then, when the polishing load decreases with a decrease in the feed speed of the wheel slide 30, the chuck control unit 150 further decreases the clamping force of the chuck 14b on the workpiece W.
In this way, the grinding machine 1 reduces the clamping force from the chuck 14b in steps in multiple steps as the grinding load is reduced. Therefore, the grinding machine 1 can reduce the amount of reduction in the clamping force at each time, and thus can suppress adverse effects (generation of grinding burn and the like) on the grinding process that are caused by the reduction in the clamping force.
Further, since the grinding machine 1 reduces the clamping force from the chuck 14b as the grinding load decreases, it is possible to suppress an adverse effect on the grinding process accompanying the reduction in the clamping force from the chuck 14 b. Therefore, the grinding machine 1 can improve the machining accuracy of the workpiece W.
In the third modification described above, the case where the chuck control unit 150 reduces the clamping force when the polishing load is reduced has been described, but the chuck control unit 150 may reduce the clamping force after a predetermined time has elapsed from the reduction of the polishing load. In this case, the grinding machine 1 can stably hold the workpiece W by reducing the clamping force of the workpiece W after waiting for the grinding load to be surely reduced. As a result, the grinding machine 1 can suppress adverse effects on the grinding process that occur with a decrease in the clamping force.
In the third modification described above, the case where the chuck control unit 150 reduces the clamping force in a stepwise manner when the polishing load is reduced has been described, but the chuck control unit 150 may gradually reduce the clamping force from the chuck 14b from the first pressure P1 to the second pressure P2 when the polishing load is reduced. In this case, since the grinding machine 1 can suppress adverse effects on the grinding process caused by the reduction of the clamping force, the machining accuracy of the workpiece W can be improved.
The polishing load generated during the polishing process varies not only with the change in the feed speed of the grindstone 20 (grindstone seat 30), but also with the flow rate of the coolant from the coolant nozzle 73. Therefore, the grinding machine 1 can also reduce the clamping force from the chuck 14b when the coolant supply device 70 reduces the amount of coolant supplied.
The present invention has been described above based on the above embodiments and modifications, but it can be easily estimated that the present invention is not limited to the above embodiments and modifications, and various modifications and improvements can be made without departing from the scope of the present invention. For example, in the above embodiment, the description has been given by taking the case where the chuck 14b is provided only on the headstock 11 as an example, but the chuck 14b may be provided on both the headstock 11 and the tailstock 12.
In the above embodiment, the case where the outer diameter of the workpiece W is measured by the dimension measuring device 80 while the polishing process is performed, and the feed speed of the wheel slide 30 is reduced when the outer diameter of the workpiece W reaches the predetermined value has been described, but the present invention is not limited thereto. For example, the grinding machine 1 may perform the grinding process while detecting the relative position of the grindstone 20 (the wheel carrier 30) with respect to the workpiece support device 10 by the encoder 61, and reduce the feed speed of the wheel carrier 30 when the relative position of the grindstone 20 with respect to the workpiece support device 10 reaches a predetermined position (a position where the outer diameter of the workpiece W is the finish grinding diameter, or the finished diameter).
In the present modification, the case where the current value of the feed driving device 60 is regarded as the grinding resistance in the grinding machine 1 has been described, but the present invention is not limited to this. For example, if the power value of the feed driving device 60 changes according to the polishing resistance, the grinding machine 1 may regard the power value other than the current value as the polishing resistance, and perform the drive control of the feed driving device 60 based on the power value. Further, the power values other than the current value include a voltage value and electric power.
In the above-described embodiment, the case where the workpiece support device 10 is moved only in the X-axis direction with respect to the bed 2 has been described, but the grinding machine 1 may be configured to be provided with a guide device that guides the workpiece support device 10 in the X-axis direction with respect to the bed 2, and to be able to move the workpiece support device 10 in the direction of approaching and separating from the grinding wheel 20.
In the above embodiment, the description has been given of the case where the table driving device 50 and the feed driving device are screw feeding devices, but a spindle motor may be used instead of the screw feeding device. In the above embodiment, the description has been given taking the case where the grinding machine 1 is a grinder of a wheel slide traverse type as an example, but the present invention can also be applied to a grinder of a table traverse type.
In the present embodiment, the description has been given of the case where the chuck 14b clamps the one end portion of the workpiece W from the outer peripheral surface, but the chuck 14b may clamp the one end portion of the workpiece W formed in a cylindrical shape from the inner peripheral surface. Even in this case, the workpiece W is fixedly supported within the range clamped by the chuck 14b, and therefore, even if the internal stress of the workpiece W is released at the rough machining, the generation of the bend in the workpiece W can be suppressed.

Claims (16)

1. A grinding machine is characterized by comprising:
a workpiece support device which has a chuck for clamping one end of a workpiece and a support part for supporting the other end of the workpiece and rotates the workpiece around an axis;
a grinding wheel that grinds the workpiece;
a feed driving device that feeds at least one of the grinding wheel and the workpiece support device in a direction in which the grinding wheel and the workpiece support device relatively approach or separate from each other;
a feed control unit that controls the feed drive device to reduce a feed speed of at least one of the grinding wheel and the workpiece support device in accordance with a progress of grinding by the grinding wheel; and
and a chuck control unit that controls a clamping force of the chuck on the workpiece, and that reduces the clamping force from a first pressure to a second pressure smaller than the first pressure when or after the feed speed is reduced.
2. A grinding machine as claimed in claim 1 in which,
the chuck control unit changes the clamping force stepwise from the first pressure to the second pressure when an outer diameter of the workpiece reaches a predetermined value or when a relative position of the grinding wheel with respect to the workpiece support device reaches a predetermined position.
3. A grinding machine as claimed in claim 1 in which,
the chuck control unit changes the clamping force stepwise from the first pressure to the second pressure after a predetermined time has elapsed since the feed speed was decreased.
4. A grinding machine as claimed in claim 1 in which,
the chuck control unit gradually changes the clamping force from the first pressure to the second pressure when an outer diameter of the workpiece reaches a predetermined value or when a relative position of the grinding wheel with respect to the workpiece support device reaches a predetermined position.
5. A grinding machine as claimed in claim 1 in which,
the chuck control unit gradually changes the clamping force from the first pressure to the second pressure after a predetermined time has elapsed since the feed speed was decreased.
6. A grinding machine as claimed in claim 1 in which,
further comprising a grinding load detector for detecting a grinding load generated by grinding of the workpiece by the grinding wheel,
the chuck control unit may decrease the clamping force from the first pressure to the second pressure when the polishing load decreases with a decrease in the feed speed or after the polishing load decreases.
7. A grinding machine as claimed in claim 6 in which,
the chuck control unit changes the clamping force stepwise from the first pressure to the second pressure when the polishing load is reduced.
8. A grinding machine as claimed in claim 2 or 7 in which,
the chuck control unit changes the clamping force from the first pressure to the second pressure, and then further changes the clamping force from the second pressure to a third pressure smaller than the second pressure in a stepwise manner.
9. A grinding machine as claimed in claim 7 in which,
the chuck control unit changes the clamping force stepwise from the first pressure to the second pressure after a predetermined time has elapsed since the polishing load was reduced.
10. A grinding machine as claimed in claim 7 in which,
the chuck control unit gradually changes the clamping force from the first pressure to the second pressure when the polishing load is reduced.
11. A grinding machine as claimed in claim 7 in which,
the chuck control unit gradually changes the clamping force from the first pressure to the second pressure after a predetermined time has elapsed since the polishing load was reduced.
12. A grinding machine as claimed in any one of claims 1 to 7 in which,
and the grinding machine is used for grinding the workpiece subjected to quenching treatment.
13. A grinding machine as claimed in any one of claims 1 to 7 in which,
the grinding machine performs grinding processing on the workpiece formed by forging.
14. A grinding machine used in a grinding method includes:
a workpiece support device which has a chuck for clamping one end of a workpiece and a support part for supporting the other end of the workpiece and rotates the workpiece around an axis;
a grinding wheel that grinds the workpiece; and
a feed driving device that feeds at least one of the grinding wheel and the work support device in a direction in which the grinding wheel and the work support device relatively approach or separate from each other,
the grinding method comprises the following steps:
a rough machining step of performing rough grinding of the workpiece by the grinding wheel;
a finish machining step of performing finish machining by the grinding wheel on the workpiece subjected to the rough grinding in a state where a feed speed of the at least one of the grinding wheel and the workpiece support device is lower than the rough machining step; and
and a first clamping force reduction step of reducing a clamping force of the chuck on the workpiece from a first pressure to a second pressure smaller than the first pressure at the end of the rough machining step or in the finish machining step.
15. The grinding method according to claim 14,
the finishing process comprises:
a first finishing step of performing finishing grinding in a state where the feed speed is lower than the rough machining step; and
a second finishing step of performing fine grinding in a state where the feed rate is lower than the first finishing step,
the grinding method further comprises:
and a second clamping force reduction step of reducing the clamping force of the chuck at the end of the first finishing step or in the second finishing step.
16. The grinding method according to claim 14 or 15,
the grinding machine includes a grinding load detector that detects a grinding load generated by grinding of the workpiece by the grinding wheel,
the first clamping force reduction step reduces the clamping force from the first pressure to the second pressure when the polishing load is reduced with a reduction in the feed rate or after the polishing load is reduced.
CN201910891708.3A 2018-09-20 2019-09-20 Grinding machine and grinding method Pending CN110936285A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114800214A (en) * 2021-01-19 2022-07-29 富鼎电子科技(嘉善)有限公司 Polishing device

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Publication number Priority date Publication date Assignee Title
CN115592537A (en) * 2022-11-15 2023-01-13 福建卓航科技有限公司（Cn） Target drone part machining grinding device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114800214A (en) * 2021-01-19 2022-07-29 富鼎电子科技(嘉善)有限公司 Polishing device

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