US 3555741 A
Description (OCR text may contain errors)
Jan. 19, 1971 Filed March 4, 1968 R. S. HAHN GRINDING MACHINE 3 Sheets-Sheet I FEED CROSS SLIDE CYLINDER l6 POSITION ELECJzg-lEYDRAULlC L5 TRANSDUCER \TT' ERROR p n lo SIGNAL i f 25 \J '8 CROSS suns I WHEELHEAD/ 24 I IQE PSQ H JKHNG DYNAMOMETER 23 MOTOR DASHPOT fizz FIG. I
ROBERT s. HAHN Jan. 19, '1971 Filed March 4, 1968 INPUT FIG. 4
R. s. HAHN GRINDING MACHINE ELECTROHYDRAULIC CROSS VALVE LVDT BENTLEY 3 Sheets-Sheet 2 FIG. 3
9 POSITIONING MOTOR METER RELAY Jan. 19, 1971 R. s. HAHN 3,555,741
GRINDING MACHINE I Filed March 4, "1968 5 SheetS -Sheet 5 LARGE WHEELHEAD .002- AND SPINDLE @s o3? SMALL WHEELHEAD .OOI- AND SPINDLE TAPER (IN/IN) AND DEFLECTION (IN) FORCE LBS.
- 3,555,741 GRINDING MACHINE" Robert S.:Hahn, Northhoro, -Massr,-assignor.ztoiThe Heald Machine Company, Worcester, ;Mass,,;a corporation of Del war Filed Mar ,4, 19.68, Ser, N p I p pint. Cl. B24b49/00 i Tafi i c o -I i I This inventio'n'relates to a* grinding machine" and, more particularly, to 'apparatus "for generating -'a surface'of revolutionby the abrasive method including-a proxitriit'y gage mounted in the"wheelhead ofi the macliirie and-gem erating a signal indicative of grindingfo'rce; 19!
1 BA KG IJND. r renewa s;
In the operation of a grinding:machinejjthereafemauy advantages 'to be obtained byre'gulating' the force between the abrasivewheel' and-thewverrpieeern inter-nal grindin (where 'the abra's'ive'whee1 is iiioiinted'oii-a cantilever spindle), the wheelhead spind le when loaded nderg'oes a radial and 'an angular d'efiectioni The ailgula'rf deflection causes taper, if not compensated for, and tii' radial de- 'flecti'ori causes chan es in bor'e s'izeZ- ThQ resence of these elastic effects complicates' t ratio arid theset np and this" is partieular'ly true if he feed-rate "'g-ifinder. rThat is to' say, even it the 'operation oi;- the vg'rindin'gi machine is perfect at a given forcer' the'se defiect ions'mpsetufthe relationships, so that'- precise ffcontrol iof- -finishedcsire and tapei'becor'nes irnpbssiblei SinceLtlie advantages controlled-force grinding are best realized by shifting frorn one I force" level to a notheig it" can :be-r sebmthat the: change, in angular and radial deflection "interfere witlr precisencom trol 0fsize and tapers l hese and. otheri difiiclilties :expera ienc'ed. with :theprior; ar tr devicesihave been 'obviatetlwinfia novel mannerby the present invention: 7 1:.
It is," therefoie, 'an-J ou-tstandingobject of the nvention -to-' provide a grinding machine arranged aso thatichanges in the g'rinding force do nofcausersizeco filnsh stoole changes or'taper-changes't; he an" "N Ii T. 1,
Another object of this invention is the provislo .of-.=:a grinding machine iiforsuse' in-t generating-.gaiisur facfi, operation 1 of the .ma'chinesbeing greatlytsimplifie i A F further 'ohjectrof the present:-:invention isat wision:of--a.,gr inding machi-nein which Lanmnskill man :need not beiconcerned agboutzspindle; dfifin for readjusting for both size and taperjzifte ehanging the grinding force.
It is another object.of the'rinstant iinv-ention to provide a grinding machine inwhich the grindir g ,force can be changed as the wheel wears m1 mall siz ,"'thereby m .taining the proper cutting 'act T new wheels as wellas usedsrna le A'still furtherobjectof'the' 'iir'ventr ag'r'inding'machine in whicli"-'the'grindi g changed to compensatefor wheel. dnlling,, and/or,yaria; L tions in workpiece "gr'indabilitywithbiifideterioration-bf other finished workpiece factors.
It is a further object of the invention to provide an internal grinding machine using a plurality of different grinding force levels wherein compensation is made for radial and angular deflection with changes in force.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.
3,555,741 Patented Jan. 19, 1971 SUMMARY OF THE INVENTION head or workhead and developing a signal indicative of grinding force, and a control receiving the signal and using it to regulate the relative movement between the workhead and the wheelhead.
BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which: FIG. 1 is a schematic plan view of a grinding machine embodying the principles of the present invention,
; FIG. 2 is a perspective view of a wheelhead incorporated in the machine.
:FIG. 3 is a horizontal sectional view of the machine taken on the line III-III of FIG. 2,
FIG. 4 is a schematic view of a control aparatus incorporated in the machine, and
- FIG. 5 is a graph showing the variation of spindle deflection with force in the case of two typical grinding spindles.
'DESCRIPTION OF THE PREFERRED EMBODIMENT t o'f'theworlcpiece in the well-known manner.
"Also mounted on the base is a cross-slide 14 arranged for-sliding transversely of the axis of the workpiece under the" impetus of a feed cylinder 15 which is operable under hydraulic pressure to provide a predetermined level of force in'grinding'. A position transducer 16 is an instrument of the LVDT type which gives an electrical signal indicative of the position of a movable core. Mounted on the cross-slide for pivotal movement about an axis 17 is afwheelhead 18.' The wheelhead is provided with a cantilever spindle 19 which carries on its outer end an abrasive Wheel'Q-l arranged for the generation of a bore inthe workpiece 13. w. Thel'cross-slide .14 is connected to'the base by a dash- 'p'ot 22 wh ich .assu'resagainst erratic movement thereof. Atthe outer end of the wheelhead 18is located an angular adjustingmotor 23 which operates on the wheelhead througlia bal1..Srew.-24. Connected in the hydraulic line lea li ng to the feed cylinder 15 is an electro-hydra-ulic valve 2 5,wh ich is capable of varying the pressure in the teed' cylinder in accordance with an error signal introduced to'the valve.
FIG S. 2 and 3 show the manner in which a proximity gagefzti associated with the wheelhead 18 and the spindle 19. A signal lead 2 7 extends away from the w eelhea'd and is'bonn'ected 'to a non-contacting position "t'r'an'sduce'r,"such' asthe Bentley pickup 28. This equipment is associated with a slinger 29 which surrounds the spindle of the wheelhead as it emerges from the wheelhead. Extending around the slinger is a bronze sensing ring 31 which is fixed to the slinger which, in turn, is fixed to the spindle in the wheelhead. The ring 31 has an outer cylindrical surface 32 and the sensing element of the Bentley pickup '28 lies closely adjacent to this surface. The pickup has the characteristic of giving an electrical signal proportional to the closeness that its senser lies to a ere given surface. Since the spindle 19 is mounted in bearingstlttin the wheelhead, any deflection either radial or angular in the spindle will result in a change in distance between the surface 32 and the senser of the Bentley pickup 28, thus resulting in a change in electrical signal on the lead 27.
Referring to FIG. 4, it can be seen that a signal proportional to the actual grinding force is compared with a reference signal and the error is fed to the electro-hydrari lic valve 25. This valve, in turn, supplies pressure to the feed cylinder of the cross-slide, thereby producing the desired grinding force at the wheel. FIG. 4 is a block diagram of this system. The input voltage is also fed to the positioning motor 23 causing the wheelhead to be swiveled by the proper amount to exactly nullify the angular deflection of the wheel. In order to make the workpiece size independent of grinding force, the feedback signal from the Bentley pickup 28 (the wheelhead dynamometer) is subtracted from the LVDT transducer 16 signal from the cross-slide 14 and is fed to a meter relay 33. The meter relay fires at a given voltage level so that, as higher forces are used, the cross slide has to move grinders whose operation .isgreatly simplified. An unskilled workman does not have to concern himself about spindle deflections and he does not have to readjust the machine for both size and taper after changing the grinding force. Moreover, thergrinding force can be changed as the wheel becomes'smaller due to wheel wear and this permits friaintaining the proper cutting action and surface finish fo'r'new wheelsofinitial Wheeldia'meter' as well as for used wprndown wheels of smaller diameteriIt makes it possible to'change the g'rinding-force to compensate for wheel dulling and for variations in workpiece grindability, For instance, some workpieces grind much slower than others, even in the same batch ofworkpieces.
' shown and described, but-'it is desired to include all such further to produce the same bore size. The gains K and K are set to match the deflection characteristics of the wheelhead. With the above system, both the bore size and taper become independent of the grinding force, i.e., programmed changes in grinding force do not affect the bore size or the straightness of the bore.
FIG. 5 is interesting in giving the general picture of the radial and angular deflection in a large and small wheelhead and shaft as the force changes at the grinding wheel. It can be seen, for instance, that a 10 pound force change will cause a little over .0001" change in deflection which means .0002" in diameter change and will result in .0002"/inch taper, so that inaccuracies introduced by relatively small changes in force can be quite appreciable. It can be seen that by use of the present apparatus it is no longer necessary to worry about spindle deflections. It is possible, then, to change the grinding force from one value to another during the grinding cycle Without afi'ecting size or taper. This can lead to the concept of programmed force profiles as inputs to the control system.
asproperly come withinthe scopeclaimed.
The inVentiOn -having-been thus described, what-is claimed as new and desired to secure by Letters Patent is:
1. A-grinding machine, comprising a a M (b) a workhead mounted 'onthe base and adapted to .t pp a OI P Q w (c);-.a wheelhead-mounted ontthe base and including 1 1a rotatablespindle with an abrasivewheel,
- d) a hydraulic cylinder for ,b ringing,ahouta :desired One can have the force built up along some curves, such as the one illustrated in FIG. 4 and to die out along an:- other curve. If the buildup takes place too fast, wheel breakdown can occur during rounding up. If it happens too slowly, of course, it adds to the cycle time. It is, therefore, quite desirable to have complete control of this force profile or the force changes which takeplace during the grinding cycle. Similarly, we may wish the force to die out along some curve and not to spark out at a rate determined bythe spindle stiffness which may consume excess time; at the present time, it is usual practice to terminate the grinding cycle by a sparkout' which uses only the accumulated forces due to the deflection of the spindle to cause grinding. It would be possible, therefore,
grinding force; 7 J a; (e) lj;a-va;lve forcontrolling the; flow of fluid to. the ,2 y i v c v --(f.) .a iproximitygage mounted so as to develop a signal indicative ofgrindingforceand v I ,f 4-! ,(g) a control receiving theelectrical signal derived from ithe proximity-gage and ,comparing.it; with a rnaster signal indicativeaof thedesired force, the error sigi nal derived from the comparison being usedto adjust the valve .for brin gingkabo'utthe desired grinding forc'e..-.,L1l 1' r p 2-.-:A..;'grinding machine as recited in' claim 1,'wherein the rQXimity'L'gage consists. of a ring mounted on the spindle and an felectrical proximity element. mounted in theiwheelhe'adzand having a sensing memberlyingadjacent the cylindrical surfaceof the ring.
33A grinding machine as: recited-in claim .2, wherein the-input signal 'of de'sired force level also operates a positioning motor which brings about angular adjustment of the position of the wheelhead relative to the axis of the workpiece. t I
LIA-grinding machine as recited-in claim .1, wherein an electricahmeasuringelement derives asignaliindicative ofthe relative position; between the workhea'dsand thewheelhe ad-and feeds thatcsig'naliinto the said control that complete information about the optimum force profile could be punched onto IBM punch cards and this card used as an input to the grinding machine to control the force cycle. 1
It can be seen, then, that the present apparatus permits changes in grinding force to take place without causing for regulating the relative 'movementbetween the work head and the wheelhead v References Cited" N TED ST S 212 5. ,4
2,801,502 ..8/19 5l7 v Blood ;et a1, 1'2,'. 6' ,8. 1 Dunigan. 3,344,569; 967. Lillie