GB2231289A - Thread grinding machine for relief grinding of thread-cutting tools - Google Patents
Thread grinding machine for relief grinding of thread-cutting tools Download PDFInfo
- Publication number
- GB2231289A GB2231289A GB8909296A GB8909296A GB2231289A GB 2231289 A GB2231289 A GB 2231289A GB 8909296 A GB8909296 A GB 8909296A GB 8909296 A GB8909296 A GB 8909296A GB 2231289 A GB2231289 A GB 2231289A
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- GB
- United Kingdom
- Prior art keywords
- workpiece
- engagement
- grinding wheel
- pick
- rotation
- 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.)
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Classifications
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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
- B24B3/00—Sharpening cutting edges, e.g. of tools; Accessories therefor, e.g. for holding the tools
- B24B3/18—Sharpening cutting edges, e.g. of tools; Accessories therefor, e.g. for holding the tools of taps or reamers
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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
- B24B3/00—Sharpening cutting edges, e.g. of tools; Accessories therefor, e.g. for holding the tools
- B24B3/02—Sharpening cutting edges, e.g. of tools; Accessories therefor, e.g. for holding the tools of milling cutters
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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
- 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
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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
- 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
- B24B49/10—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 involving electrical means
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
Description
THREAD GRINDING MACHINE The invention relates to thread producing
apparatuses, and more specifically, it deals with metal cutting machines for thread cutting by means of a grinding wheel, more particularly, with thread grinding machines.
A thread grinding machine according to the invention is used for cutting teeth of multiple-blade cutting tools such as taps, hobs, single-thread milling cutters, form cutters having teeth inbetween flutes, which have relieved profile and may extend along a helical line or circle. In addition to that at least one tooth may be located at one flight of the helical line or one circle, the flutes being either straight or helical.
The relieved profile of the teeth of multiple-blade tools is known to keep profile of the teeth and constant relief angle upon regrinding. With the relieved profile of a tooth, projection of its outer edge on a plane drawn perpendicularly to the axis of a tool is most frequently in the form of Archimedean spiral. For produ- cing a relieved profile of teeth in multiple-blade to ols, a relieving mechanism is provided in thread grinding machines. The relieving mechanism comprises a cam having Its profile in the form of Archimedean spiralq which is operatively connected to a rotation drive. Du- ring one revolution of the cam of the relieving mechanism a desired reliev ed tooth profile is formed on each of the surfaces of a workpiece disposed between the edges of flutes. The member of machined surfaces on which the relieved profile is f oined is equal to the number of f lu- tes. With a single flute, the machined surface is disposed between the edges of this flute. With a larger number of flutes, the machined surface is disposed between the edges of adJaced flutes.
In carrying out the teeth relieving operation, it is important to ensure a timely engagement of the relieving mechanism. It is desired that at the initial moment of machining, when the cam of the relieving mechanism is in the initial position, the cam rotation drive be turned on when one of the surfaces of the workpiece dispo- sed between the edges of flutes comes in touch with a grinding wheel. It should be noted that the grinding wheel should come in touch with this surface inan.immediate vicinity to the edge of the flute on the side of the back rake or true rake of the tooth of a multiple- blade tool depending on direction of rotation of the workpiece. Untimely turning on of the rotation drive of the cam of the relieving mechanism when the grinding wheel comes in touch with other portions of the workpiece surface may result in a major change in relieved profile of the tooth thereby lowering yield of normalgrade parts.
Various devices and means are provided in thread grinding machines aimed at ensuring a desired orientation of one of the workpiece surfaces located between the edges of flutes with respect to the grinding wheel when they come in touch with each other at the initial moment of machining.
Known in the art is a thread grinding machine for making taps having at least two flu.tes the machine comprises a bed supporting a worktable having two supports for a workpiece, at least one support being operatively connected to a worlpiece rotation drive which is operatively connected to a mechanism ensuring reciprocations of the worktable along the axis of rotation of the workpiece, and a wheelhead carrying a grinding wheel and its rotation drive, the wheel-head being operatively connected to its reciprocation drive ensuring re- ciprocations in a direction perpendicular to the axis of rotation of the worlpiece, which is operatively connected to a relieving mechanism connected, via a clutcht to the workpiece rotation drive and having a cam for setting up the relieved profile of each surface of the workpiece located between the edges of workpiece flutes by rotation of the cam. The machine also has a means for orienting the workpiece at the moment it comes in touch with the surface of the grinding wheel when the cam of the relieving mechanism is in the initial position. The tap blanks have at least two flutes and a shank with flats having their faces which are Dairwise parallel. In particular, the shank is formed as a square in the cross-section. One of the flats of the shank is strictly oriented with respect to one the flutes for the whole lot of taps being machined.
The means for orienting the workpiece at the initial moment of machining when its surface comes in touch with the grinding wheel is in the form of a holder in- sertable in a loading device of the thread grinding machine. The holder is in the form of a rod having square -section receptacles provided axially thereof for receiving the shanks of the tap blanks.Orientation of the tap blanks is ensured by placing them in the holders in one and the same position i.e. the flats and flutes should be positioned identically with respect to the rod axis. This orientation means for blanks calls for accuracy of orientation of flats of the shank with respect to flu- tes for the whole lot of blanks. In addition, the preparatory operation before installation of the workpieces in the holders results in an increased cost of taps.
Also known in the art is a universal thread grinding machine for machining blanks of various multiple- blade tools such as taps. hobs and special cutters having at least one flute, comprising a bed having a work -table provided with two supports for a workpieces, at least one support being operatively connected to a work -piece rotation drive which is operatively connected to a mechanism ensuring reciprocations of the worktable along the axis of rotation of the workpiece and a wheel -head carrying a grinding wheel with its rotation drive, the wheelhead being operatively connected to a drive ensuring its reciprocations in a direction perpendicu- lar to the axis of rotation of the workpiece, and relieving mechanism which is opertively connected, to the workpiece rotation drive via a clutch coupled with and a means for orienting the workpieces at the initial mo- ment of workpiece machining when it comes in touch with the grinding wheel when a cam of the relieving mechanism setting up the relieved profils of each surface of the workpiece located between the edges of fluts during its rotation is in the initial position.
The means for orienting the workpiece is in the form of a faceplate attached to an end face of a spindle of the workpiece ion drive, the faceplate functioning as a clutch of the relieving mechanism and workpiece rotation drive. The faceplate has a base, a rotatable part and a driver member,, the faceplate ensuring an operative connection between the spindle, workpiece and the relieving mechanism cam through a collar rigidly secured to the workpiece.
The orientation of the workpiece is a preparatory step which is carried out manually by the operator to ensure engagement of the edge of a flute with the surface of the grinding wheel when the relieving mechanism cam is the initial position by varying angular po- sition of the rotatable part of the faceplate with respect to the base and visually determining position of the workpiece. The angular position of the workpiece may be varied by rotating it in the collar without changing position of the rotatable part of the facepla- te with respect to the base.
It can take from two to five minutes to orient the workpiece, the setting time depending on the operator's skill. Readjustment of the orienting means and setup of the initial position of the workpiece are required for each new lot of tool blanks being machined. The accuracy of orientation of the workpiece also depends on the operator's skill. All this substantially lowers productivity of the thread grinding machine.
It is an object of the invention to enhance productivity of a thread crinding machine by reducing time needed for setting up a workpiece in the desired position before machining.
The invention essentially resides in that in a thread grinding machine for machining multiple-blade tools having at least one flute, a bed has a worktable provided with two supports for a workpiece and a wheel head; at least one of the supports is operatively connected to a work-piece rotation drive which is operatively connected to a mechanism ensuring reciprocations of the worktable along the axis of rotation of the workpiece: a grinding wheel and its rotation drive is carried by the wheelhead and the wheelhead is operative -ly connected to its reciprocation drive in a direction perpendicular to the axis of rotation of the workpiece; the workpiece rotation drive is connected to a relieving mechanism via a clutch which is connected to a means for orienting the workpiece at the initial mo- ment of machining when it comes in touch with the surface of the grinding wheel when a cam of the relieving mechanism, the rotation of which sets up the relieved profile of each surface of the workpiece located bet- ween edges of flutes, is in the initial position; the means for orienting the workpiece at the initial moment of machining when it comes in touch with the surface of the grinding wheel when the cam of the relieving mecha nism is in the initial position comprising: a series circuit including a pick-up for sensing engagement of the grinding wheel with the workpiece, a converter for converting electrical signals of the engagement pick-up into pulse signals, each pulse signal corresponding to the engagement of the grinding wheel with a surface of the workpiece located between the edges of fluts. the converter being electrically coupled to a controlled clutch, a control unit for controlling engagement of the controlled clutch forming a control signal following any signal but first from the engagement pick-up electric signal converter.
It is preferred that the unit for controlling engagement of the controlled clutch in a thread grinding machine comprise a pulse counter for counting pulses each of which corresponds to the engagement of the grinding wheel with the workpiece surface located between the edges of flutes, a digital campaxator having an input connected to the pulse counter, and a pulse count setter connected to another input of the digital comparator.
It is profitable that a thread grinding machine,in which the workpiece rotation drive has at least two rotation speeds, be provided with a workpiece speed pickup connected to an auxiliary input of the converter converting electric signals of the engagement pick-up into pulse signals, which comprises a series circuit including a bandpass amplifier having an input for receiving a signal from the pick-up sensing engagement of the grinding wheel with the workpiece, a detector, a low-pass filter and an analog comparator and a series circuit including a detector having an input for receiving a signal from the workpiece speed pick-up, an amplifier and a variable current stabilizer having an out- put connected to the input of the analog comparator.
In a thread grinding machine according to the in vention, the unit for controlling engagement of the controlled clutch, which forms a control signal follo wing any signal but first from the converter of elect ric signals of the engagement pick-up ensures at the initial moment of machining an automatic setting of the blank of any tool in the desired position irrespective of its initial position during installation of the sup ports.
At the initial moment the first engagement of the grinding wheel with the workpiece most frequently occ urs at a random point of the workpiece surface between flutes, no control signal being fed from the engagement control unit to the controlled clutch. The second enga gement of the grinding wheel with the workpiece and each following occurs at the edge of the flute. and a control signal is fed from the engagement control unit to the controlled clutch, the clutch is engaged to cau- se movement of the relieving mechanism cam. Thus a blank of any multiple- blade tool is in the desired po sition at the initial moment of engagement of the relieving mechanism, namely, at the moment of any but first engagement of the grInding wheel with the work piece.
This allows time needed for machining each workpiece to be substantially reduced as substantially no time is needed for carrying out the step of orientation of the workpiece before machining is started thereby enhancing productivity of the thread grinding machine. It should be noted that accuracy and orientation time depend neither on the type of a tool being machined, nor on the number and position of flutes, nor e15 ven on the operator's skill.
In carrying out machining of various types of multiple-blade tool blanks with one and the same feed during the first pass no readjustment and setting up of the orientation means is required.
Universality of the means for orienting the workpiece according to the invention makes it possible to use simple devices for loading workpieces.
The cost of providing both universal and automatic thread grinding machines with the orienting means according to the invention is minimal.
The invention will now be described in detail with reference to specific embodiments illustrated in the accompanying drawings, in which:
Figure 1 shows a simplified kinematic diagram of a thread grinding machine having an engagement control unit for a controlled clutch according to the inventi- on; Figure 2 is a block-diagram of a means for orien ting a workpiece at the initial moment of machining when it comes in touch with a grinding wheel, accor ding to the invention; Figure 3 shows a workpiece and a part of a grin- ding wheel to illustrate their relative position when the grinding wheel comes in touch with an end face of the workpiece; Figure 4 is ditto of Figure 3. when the grinding wheel is located in front of a flute; Figure 5 is ditto of Figure 3, when the grinding wheel is in touch with the edge of a flute on the side of the true rake of a tool tooth; Figure 6 is ditto of Figure 3, when the grinding wheel is in touch with the edge of a flute on the side of the back rake of a tool tooth.
A thread grinding machine comprises a bed 1 (Figure 1) on which there is mounted a worktable 2 having two supports 3 and 4 in which a workpiece or a blank 5 of a multiple-blade tool is clamped. Workpieces or blanks 5 of multiple-blade tools such as taps, hobs and single-thread milling cutters have a cylindrical or conical surface in which at least one flute is provided to = in parallel with the workpiece axis or helically thereof. The number of flutes, depending on application of tbe tool, may range f rom one to twenty f our and even more 9 The support 3 is a headstock of a machine having a spindle 6 In which a center 7 is provided which has a collet chuck 8. The support 4 is a tailstock of the machine in which a centter 9 is provided. At least one of the supports 3, 4 is operatively connected to a workpiece rotation drive 10.
In this embodiment of the thread grinding machine, the support 3 is connected to the rotation drive 10.
The workpiece rotation drive 10 comprises an electric motor 11 which is mounted on the bed 1 and has a shaft which is connected, via a belt transmission 12, to a splined shaft 13 connected to the spindle 6 of the sup- port 3.
The worktable 2 is mounted for reciprocations along the axis of rotation of the workpiece 5 on the bed 1 and is connected to a worktable reciprocation drive 14, i. e. with a long feed mechanism.
The worktable reciprocation drive comprises a mo tion screw 15 mounted for rotation in the worktable 2 and running in parallel with the axis of rotation of the workpiece 5 the motion screw being in engagement with a nut 16 secured to the bed 1.
The workpiece rotation drive 10 is operatively con nected to the worktable reciprocation drive 14 by means of a gear train 17 with change gears, which is designed for setting up the desired thread pitch. The construetion of the gear train 17 is well known in the art of thread grinding machines. One of gears, 18. of the gear train 17 is connected to one end of the motion screw 15 and another gear, 19, is mounted on the splined shaft 13 of the workpiece rotation drive 10.
A wheel head 20 mounted on the bed 1 is operatively connected to a reciprocation drive 21 for reciprocations in a direction prependicular to the axis of rotation of the workpiece 5. The wheelhead reciprocation drive 21 comprises an electric motor 22 having a shaft connected to a pinion 23 meshing with a gear 24 which is rigidly connected to a nut 25 mounted for rotation about its axis in the wheelhead 20. The nut 25 is put on one end of a cross feed screw 26. The axis of the cross- feed screw 26 extends in a plane perpendicular to the axis of rotation of the workpiece 5. The other end of the cross feed screw 26 is axially movable in a support 27 attached to the bed 1. In this embodiment of the thread grinding machine, the wheelhead reciproca- tion drive 21 is operatively connected to a relieving mechanism 28. The relieving mechanism 28 comprises a roller 29 rigidly secured to the cross- feed screw 26 The roller 29 is in permanent contact with a cam 30 of the relieving mechanism 28. The cam 30 is mounted for rotation on a shaft 31 and has, as it is well known. a profile which is normally made in accordance with Archi medean spiral. Upon one revolution of the cam 30 of the relieving mechanism 28, a desired relieved profile of a 1 tooth is formed on each surface of the workpiece located between adjacent edges of flutes. With another known embodiment of a thread grinding machine, the relieving mechanism may be operatively connected to one or both supports for clamping the workpiece.
To ensure permanent contact between the roller 29 and the cam 30 of the relieving mechanism 28. the wheelhead 20 is pressed against the bed 1 by means of a tension apring 32 which is mounted in such a manner that its axis runs substantially in parallel with the cross feed screw 26.
The relieving mechanism 28 is connected to the workpiece rotation drive by means of a clutch which is in the form of a controlled clutch 33 having one clutch member mounted on the shaft 31 and the other clutch member mounted on one end of a shaft 34 of a gear train 35 of the relieving mechanism 28 having a group of change gears, one gear 36 being mounted on the other end of the shaft 34. Another gear 37 is mounted on the splined shaft 13 of the workpiece rotation drive 10.
The gear train 35 of the relieving mechanism 28 is set up in such a manner that the number of revolutions of the cam 30 of the relieving mechanism 28 per one revolution of the workpiece 5 be equal to the number of surfaces of the workpiece located between the flutes, taking into account position of the flutes.
A grinding wheel 39 operatively connected to its rotation drive 40 is mounted on a spindle 38 of the wheelhead 20. The wheel rotation drive 40 has an electric motor 41 which is connected. by means of a belt transmission 42, to the spindle 38 of the grinding wheel 39.
The clutch 33 is connected to a means for orienting the workpiece at the moment of initial machining when it comes in touch with the surface of the grinding wheel 39 when the the cam 30 of the relieving mechanism 28 is in the initial position.
The controlled clutch 33 may be in the form of any controlled clutch, e.g. an electromagnetic friction clutchl a hydraulically actuated friction clutch or any other known controlled clutch that can ensure coupling of shafts at substantially random relative position.
The means for orienting the workpiece at the initial moment of machining when it comes in touch with the sur face of the grinding wheel comprises a controlled clutch engagement control unit 43 electrically coupled to the controlled clutch 33.
The means for orienting the workpiece also comprises a pick-up for sensing the engagement of the grin--ding wheel with the workpiece connected to a converter 45 converting electric signals from the engagement pick-up to pulse signals each of which corresonnds to engagement of the grinding wheel with surfaces of the workpiece located between the flute edges, which is connected to an input of the controlled clutch engagement control unit 43 which forms a control signal following any signal but first from the converter 45.
k The pick-up 44 sensing engagement of the grinding wheel with the workpiece is in the form of a piezoelectric pick-up mounted directly on the center 9 of the support 4. Any other appropriate known pick-up may be used to f orm at its out-put a signal in response to engagement of the grinding wheel with the workpiece.
The thread grinding machine also comprises a pickup 46 sensing the initial position of the cam 30 of the relieving mechanism 28. The pick-up 46 sensing the ini tial position of the cam of the relieving mechanism is in the form of a contact switch mounted on the bed 1.
Rotation of the cam 30 of the relieving mechanism 28 is provided by the workpiece drive 10. An independent drive ( not shown in Figure 1) can be used for setting up the cam 30 of the relieving mechanism 28 in the initial position.
The controlled clutch engagement control unit 43 (Figure 2) forming a control signal following any signal but first from the engagement pick-up electric signal converter comprises a pulse counter 47 for counting pulses each of which corresponds to the engagement of the grinding wheel with a workpiece surface located between the edges of the flutes, a digital comparator 48 having an input connected to the pulse counter 47 for counting pulses each of which corresponds to the engagement of the grinding wheel with a surface located between the edges of the flutes, and a pulse count setter 49 for setting the number of pulses each of which corresponds to the engagement of the grinding wheel with the workpiece surface located between the edges of the flutes. connected to another input of the digital comparator.
When a piezoelectric pick-up is used as the pickup 44 for sensing engagement of the grinding wheel with the workpiece, the thread grinding machine having the workpiece drive 10 for several speeds comprises a workpiece speed pick-up 50 connected to an auxiliary input of the engagement pick-up electric signals to pulse sig- nals converter 45 which comprises a series circuit including a bandpass amplifier 51 having an input receiving a signal from the pick-up 44 sensing engagement of the grinding wheel with the workpiece, a detector 52, a low-pass filter 53 and an analog comparator 54 and a se- ries circuit including a detector 55 having an input re- ceiving a signal from the workpiece speed pick-up 50.an amplifier 56 and a variable current stabilizer 57 having an output connected to an input of the analog corapara tor 54.
Figures 3, 4, 5, 6 show a workpiece 5 in the form of a tap blank having three flutes 58 and three surfa ces 59 of the workpiece 5. each being located between edges 60 and 61 of the flutes 58. The edge 60 is on the side of the true rake of the tool tooth and the edge 61 is on the side of the back rake of the tool. Arrows 'Ivy# and 11w11 show directions of rotation of the workpiece 5 and grinding wheel 39, respectively, and llell is the amount of feed of the grinding wheel 39.
The thread grinding machine functions in the following manner. First, in accordance with the number of flutes of the workpiece 5 (Figure 1) of the multipleblade tool, the gear train 35 of the relieving mechanism 28 is set up in such a manner that the number of revolutions of the cam 30 of the relieving mechanism 28 correspond to the number of surfaces of the workpiece 5 located between the flute edges. Then, with the enga ged controlled clutch 33, the cam 30 of the relieving mechanism 28 is rotated by the workpiece drive 10 to bring the cam to the initial position. The initial position of the cam of the relieving mechanism corresponds to a position of the wheelhead in which the grinding wheel is spaced from the axis of rotation of the workpiece substantially at a distance equal to maximum or minimum radius of tooth of the tool depending on di rection of rotation of the workpiece drive. In determining the initial position of the cam 30 of the relieving mechanism 28, it is necessary to take into account the speed of actuation of the controlled clutch 33.The moment at which the cam 30 of the relieving. mechanism 28 arrives at the initial position is sensed by the pickup 46 of the initial position of the can of the relieving mechanism 28, and a signal from the pick-up dee- nergizes the electric motor 11 of the workpiece rotation drive 10 and causes disengagement of the controlled clutch 33. An independent drive (not shown in Pigure 1) for rotation of the can of the relieving mechanism can bt used for bringing the cam of the relieving - is - mechanism back to the initial position.
The workpiece 5 is then installed in any position in the supports 3 and 4 and clamped in the centers 7 and 9. The reciprocation drive 21 of the wheelhead 20 is switched on for moving the wheelhead 20 through a feed stroke. The electric motors 41 and 11 of the grinding wheel rotation drive 40 and workpiece rotation drive 10, respectively, are switched on. and the workpiece 5 is through-feed ground.
At the limit position of the wheelhead 20, with the preset feed Ilell (Figures 3, 4, 5, 6) of the grinding wheel 39. the relative position of the workpiece 5 and grinding wheel 39 may differ. The first engagement of the grinding wheel 39 with the workpiece 5 most freque- ntly occurs at the end face of the workpiece 5 ( Figure 3) or at the edges 60 (Figure 5) or 61 (Figure 6) of the flute 58. When the grinding wheel 39 comes in touch with the workpiece 5, the pick-up sensing engagement of the grinding wheel with the workpiece, which is mounted on the support 4 records the workpiece oscillations occurring during grinding and transmits a signal to the input of the engagement pick-up electric signal to pulse signal converter 45, a signal from which goes to the input of the engagement control unit 43 of the controlled clutch forming a control signal following any signal but first from the converter 45. Thereforey a first signal from the engagement pick-up 44 is stored in the controlled clutch engagement control unit 43. The controlled 33 remains disengaged. Rotation of the workDic,: 5 n -1 continues. When the flute 58 (Figure 4) approches the grinding wheel 39, no engagement of the grinding wheel 39 with the workpiece 5 occurs, and there is no signal at the output of the pick-up 44 sensing engagement of the grinding wheel with the workpiece.
A second engagement of the grinding wheel 39 with the workpiece 5 occurs either at the edge 60 (Figure 5) or at the edge 61 (Figure 6). The second signal from the pick-up 44 sensing engagement of the grinding wheel with the workpiece is fed through the engagement pick-up electric signal converter 45 to the input of the controlled clutch engagement control unit 43 following which a control signal for engagement of the controlled clutch 33 is formed.
As a result of engagement of the controlled clutch 33, the kinematic chain of the relieving mechanism 28 is closed, and the cam 30 causes the wheelhead 20 to move to relieve the surface being machined which is located between the flutes. The controlled clutch 33 remains engaged during the entire cycle of machining of the workpiece 5. Therefore, the means for orienting the workpiece at the initial moment of machining when the grinding wheel comes in touch with the workpiece when the cam of the relieving mechanism is in the initial po- sition always ensures the correct position of the workpiece 5 or a blank of any multiple-blade cutting tool with respect to the grinding wheel 39 practically instantaneously so as to substantially increase producti- vity of the thread grinding machine.
The controlled clutch engagement control unit 43 (Figure 2) forms a control signal following any signal but first from the engagement pick-up electric signal converter 45. The pilse counter 47 counting pulses each of which corresponds to engagement of the grinding wheel with the surface of the workpiece counts the number of surfaces of the workpiece coming in touch with the grinding wheel, and the ordinal number of the signalfollowing which the control signal is formed is set up by the pulse count setter 49 setting the number of pulses each of which corresponds to engagement of the grinding wheel with the surface of the workpiece located bet -ween the edges of the flutes. This ordinal number de- pends on design of the workpiece (blank), e.g. on the provision of the starting taper. With the cylindrical outer periphery of the workpiece 5, a signal from the pick-up 44 with the second pulse gives the exact orientation of the workpiece 5 upon engagement of the cont- rolled clutch 33. If there is a starting taper on the workpiece, the exact orientation depends on the number of surfaces located between the flute edges on the starting taper which may range from three to ten.
When signals fed to the digital comparator 48 from the pulse counter 47 and pulse count setter 49 are equal to each other, a signal for engagement of the controlled clutch 33 is fed from the output of the digital comparator 48.
1 The signal fed from the grinding wheel engagement pick-up 44 mounted on one of the centers 9 (Figure 1) of the thread grinding machine is amplified in the engagement pick-up electric signal to pulse signal conver- ter 45 in the bandpass amplifier 51 (Figure 2) having its amplification band corresponding to forced oscillation frequencies of the center of the machine on which the pick-up 44 is mounted. The signal is then detected by the detector 52, filtered in the low-pass filter 53 jo and goes to the input of the analog comparator 54. At the same time, a signal is fed from the workpiece rotation speed pick-up 50 to the detector 55 of the engagement pick-up electric signal converter 45 wherein it is detected and then amplified in the amplifier 56 to go the input of the variable current stabilizer 57. The variable current stabilizer 57 connected to the output of the low-pass filter 53 forms a discharge circuit of the low-pass filter 53. The discharge time constant of the low-pass filter is inversely proportional to the magnitude of signal from the workpiece rotation speed pick-up 50. At any speed of rotation of the workpiece 5 (Figure 1), the signal arriving at the input of the analog comparator 54 (Figure 2) is integrated. The discharge time constant upon a change in the workpiece speed is automatically set up in such a manner that changes in the signal from the pick-up 50 sensing speed of rotation of the workpiece occurring upon a transition pro cess when the grinding wheel comes in touch with the workpiece do no result in a lowering of the signal level at the output of the low-pass filter 53. It should be noted that the pre-set value of the discharge time constant ensures a decrease in the signal level at the output of the low-pass filter 53 (Figure 2) below the actuation threshold of the analog comparator 54 before the next engagement of the grinding wheel 39 with the workpiece 5 after disengagement of the grinding wheel 39 (Figure 4) from the workpiece 5 when the grinding wheel 39 enters the flute. Therefore. the engagement pick-up electric signal to pulse signal converter 45 ac cording to the invention makes it possible to detect engagement of the grinding wheel 39 with the workpiece 5 substantially within the entire range of rotation speeds of the workDiece 5.
Claims (4)
1. A thread grinding machine for machining blanks of multiple-blade tools having at least one fluteg having a bed provided with a worktable with two supports for a workpiece and wheelhead, at least one support being operatively connected to a workpiece rotation drive which is operatively connected to a worktable reciprocation drive for reciprocations of the worktable along the axis of rotation of the workpiece; a grinding wheel with a rotation drive thereof carried by the wheelhead, the wheelhead being operatively connected to its reciprocation drive for reciprocations thereof in a direction perpendicular to the axis of rotation of the workpiece; the workpiece rotation drive being operatively connected; to a relieving mechanism via a controlled clutch which is connected to a means for orienting the workpiece at the initial moment of machining when the grinding wheel surfaces engages the workpiece when a can of the relieving mechanism is in the initial posi- tion, the rotation of the cam determining the profile of each surface of the workpiece located between edges of flutes thereof; the means for orienting the workpiece at the initial moment of machining upon engagement with the grinding wheel when the cam of the relieving mechanism is in the initial position comprises a series circuit including a pick-up sensing engagement of the grinding wheel with the workpiece. an engagement pickup electric signal to pulse signal converter, each pulse signal corresponding to engagement of the grinding wheel with a surface of the workpiece located between the flute edges, the converter being electrically coupled to the controlled clutch, and a controlled clutch engagement control unit forming a control signal following any signal but first from the engagement pick-up electric signal converter.
2.A thread grinding machine according to claim 1, wherein the controlled clutch engagement control unit comprises a pulse counter for counting pulses each of which corresponds to engagement of the grinding wheel with a surface of the workpice located between the flute edges, a digital comparator having an input connected to the pulse counter, and a pulse count setter con- nected to another input of the digital comparator.
3. A thread grinding machine as claimed in claim 1 or 2, wherein a workpiece rotation speed pickup is connected to an auxiliary input of the engagement pick-up electric signal to pulse signal converter which comprises a series circuit including a bandpass amplifier having an input receiving a signal from the pick-up sensing engagement of the grinding wheel with the workpiece, a detector, a low-pass filter, and an analog comparator and a series circuit including a detector having an input receiving a signal from the workpiece rotation speed pick-upg an amplifier and a variable current stabilizer having an output connected to the input of the analog comparator.
f -1 - 25
4. A thread grinding machine substantually as he. rein-above described with reference to% and as shown in the accomPanying drawings.
Published 1990 atThe Patent Office, State House, 66.71 I-IlghHolborn, London WC1R 4TP.Purther copies maybe obtalnedfrom The PatentOMce.
Sales Branch. St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray. Kent, Con. 1187 Sales Branch. St Mary Crav. OrDiniZton. Kent BR5 3RD. Printed bV MultlDlex technioues ltd. St MarvCraV. Kent. Con. 1187
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8909296A GB2231289A (en) | 1989-04-24 | 1989-04-24 | Thread grinding machine for relief grinding of thread-cutting tools |
| CH155389A CH678503A5 (en) | 1989-04-24 | 1989-04-25 | |
| DE19893914885 DE3914885A1 (en) | 1989-04-24 | 1989-05-05 | THREAD GRINDING MACHINE |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8909296A GB2231289A (en) | 1989-04-24 | 1989-04-24 | Thread grinding machine for relief grinding of thread-cutting tools |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8909296D0 GB8909296D0 (en) | 1989-06-07 |
| GB2231289A true GB2231289A (en) | 1990-11-14 |
Family
ID=10655622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8909296A Withdrawn GB2231289A (en) | 1989-04-24 | 1989-04-24 | Thread grinding machine for relief grinding of thread-cutting tools |
Country Status (3)
| Country | Link |
|---|---|
| CH (1) | CH678503A5 (en) |
| DE (1) | DE3914885A1 (en) |
| GB (1) | GB2231289A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007134496A1 (en) * | 2006-05-18 | 2007-11-29 | Xiaohua Xu | A processing machine for worm or lead screw |
-
1989
- 1989-04-24 GB GB8909296A patent/GB2231289A/en not_active Withdrawn
- 1989-04-25 CH CH155389A patent/CH678503A5/de not_active IP Right Cessation
- 1989-05-05 DE DE19893914885 patent/DE3914885A1/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007134496A1 (en) * | 2006-05-18 | 2007-11-29 | Xiaohua Xu | A processing machine for worm or lead screw |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8909296D0 (en) | 1989-06-07 |
| DE3914885A1 (en) | 1990-11-08 |
| CH678503A5 (en) | 1991-09-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |