US3813823A

US3813823A - End mill grinder

Info

Publication number: US3813823A
Application number: US00232520A
Authority: US
Inventors: J Southland
Original assignee: OMARK WINSLOW CO
Current assignee: OMARK WINSLOW AEROSPACE TOOL CO US; OMARK WINSLOW CO
Priority date: 1969-06-25
Filing date: 1972-03-07
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04

Abstract

A complete installation is provided for grinding cutters, especially and typically, end mills, by machine controlled operations. The installation has three separate stations which, when all are used, provide maximum flexibility in the shape imparted to the end mill, accuracy of grind, and the ability to repeat or duplicate a particular grind on a series of duplicate cutters. The only manual operations are loading and unloading the end mills at each of the stations; and consequently the grinding of the mill is accomplished rapidly and at low cost.

Description

United States Patent 1 1 1111 3,813,823

Southland 1 June 4, 1974 [54] EM) MILL GRINDER 2,795,091 6/1957 Umbdenstock 51/225 [751 lnvemo" Southland, Arcadlai 3.073.076 1i196 51/ 2 45 Callf- 3,117,399 1/1964 Schoeppell... 51/225 3,365,843 1/1968 ROblnSOn ..51/225 [73] Ass'gnee' Oma'k Aemspace Tool 3,397,492 8/1968 Wilson 51/96 3,680,262 8/1972 Aydelott ..5l/288X [22] Filed: Mar. 7, 1972 Primary Examiner-Donald G. Kelly [211 App! 232520 I Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Related US. Application Data I Voit & Osann, Ltd.

[63] Continuation of-Ser. No. 836.467, June 25, 1969. i

v [57] ABSTRACT [52] 51/94 51/95 I A complete installation is provided for grinding cutters, especially and typically, end mills, by machine [51] Int. Cl B241) 3/06 controlled Operations The installation has three Sepa [58] Field of g 2 i gi gggf rate stations which, when all are used, provide maxi- 237 mum flexibility in the shape imparted to the end mill,

accuracy of grind, and the ability to repeat or dup1i [56] References c cate a particular grind on a series of duplicate cutters. UNITED STATES, PATENTS The only manual operations are loading and unloading 253,890 2/1882 Rogers. 51/97 the end mills at each of the stations; and consequently 767,387 8/]904 Chard I 5 1/97 R the grinding of [he is accomplished and at 2.332,5 l0 10/1943 Franzen l cost 2.42l.358 5/l947 Sneva I 2.484.590 10/1949 Rocheleau 51/225 36 Claims, 33 Drawing Figures /0.D i I asberv {Te/fever PATENTEDJUH 4mm 3. 13323 I sum 112 0F 11 Mag;

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PMENTEDJUN 41914 $813523 saw 05 I]? n JANE/V706 PATENTEDJuu 4 1914 sum as or u 1 END MILL GRINDER This is a continuation of application Ser. No. 836,467, filed June 25, 1969.

BACKGROUND OF THE INVENTION The present invention relates generally to grinders for shaping or sharpening cutters for machine tools, and more especially to equipment of this type for grinding end mills, either sharpening old ones or grinding new ones from blanks.

Heretofore, grinding end mills in this way has been done by hand with the aid of jigs and fixtures. These mechanical aids steady the hand of the operator, but nevertheless known procedures depend largely upon the personal skill and experience of the particular operator. When the grinding is basically a manually controlled operation, the product of such known procedures suffers from unpredictable inaccuracies, and this in turn leads to a lack of uniformity in the'product. As in most hand operations as compared with machine performed operations, the relative cost of sharpening a mill is greater when it is done by hand than by machine.

Modern mass production techniques have led to the widespread use of multiple-spindle machine tools of many varieties. A milling machine may have several spindles, for example three, each working on a separate part and all operating simultaneously so that three different work pieces are being machined at once. In other types of machine tools, a plurality of cutters are sequentially engaged with a work piece.

A further step in mass production technique has led to the operation of machine tools by numerical controls, typically a punched tape which feeds through a reader and causes the machine to perform all of the several cutting operations in the proper sequence withoutcontrol by a machine operator. Multiple-spindle machine tools operated by numerical controls place a premium on having all cutting tools exact duplicates of one another so that they all operate exactly alike and, importantly, have the same useful cutting life.

By way of example, assume a milling machine having three cutters and it is known that a given number of work pieces can be milled before the cutters become dull and require replacement. In a numerically controlled machine, the tape is then punched to schedule a complete retooling of all spindles after a given number of pieces have passed through. However, if one cutmore adverse results are possible. Because of the different sizes or shapes of the cutters, all of the products are 1 not precise duplicates of each other and therefore may not be interchangeable. This can lead to a large percentage of rejects with an obvious increase in cost of parts.

Another common result of this situation is that one cutter becomes dull before the other two. This results in the dull cutter breaking, causing a premature shutdown of the machine. In addition to the unnecessary and costly down time caused by an unscheduled tool change, the useful life of all the cutters in the machine is diminished since they must all be changed or replaced at the same time. Furthermore, an unscheduled stoppage of this character oftentimes results in much more time being required to place that particular machine back in operation than is true of stoppage at properly scheduled intervals.

Consequently, it becomes a general object of the present invention to provide an installation of novel construction for originally grinding or resharpening machine tool cutters. such as end mills, capable of producing cutters that are precise duplicates of one another.

It is also an object of the present invention to provide an installation for sharpening or initially grinding end mills which is capable of maximum flexibility in the sizes and shapes of end mils handled andthe shapes of the'cutting surfaces ground on the mills.

A further object of the present invention is to provide an installation capable of grinding cutters in which all operations are carried out by machine, and manual operations are limited to loading and unloading the grinding units, and in which grinding operations are performed more rapidly, more accurately, and with lower cost than has heretofore been possible.

. SUMMARY OF THE INVENTION The above and other objects and advantages of the present invention have been achieved in a cutter grinding installation comprising three separate but similar grinding stations, each station comprising a grinding wheel, a tool holder, and mounting means of novel construction for supporting and moving the tool holder and a cutter therein over a predetermined path with respect to the grindwheel to perform certain grinding operations at each station. The first and third stations are provided with grindwheels having a cylindrical grinding surface while the second station differs in having the grindwheel with at least one and preferably two circumferential ridges. All three stations are very similar in appearance since many common parts are used in the basic structures, although each station has certain unique features. In order to make maximum use of common parts, some movements or parts at any of the stations may be superfluous; but the presence or absence of such parts is normally a matter of choice.

The first station is a radius and outside diameter grinder adjustable to grind any desired cutting surface on an end mill from a ball grind to a straight grind with a flat end surface on the cutter or with any desired degree of radius in between. In the first station, the tool holder is mounted in a work head which includes a motor for continuously rotating the tool holder while the cutter is in contact with the grindwheel.

At the second station, a gash is cut at the base of each land of a radiused or ball end mill. For this purpose the workhead is also provided with an indexing mechanism to'index the drill by rotating the drill about its axis in increments determined by the number of flutes on the cutter and means to lock the cutter in each grinding position.

At the third station, the primary and secondary relief angles are ground on each land. Consequently, the

work head is here also provided with indexing and lock mechanism similar to that at the second station. Means for setting the desired angles are provided. The cutter in the work head then turns about its own. axis in contact with a tooth rest to grind the desired relief angle on each land in proper sequence.

In general, each station is constructed with reference to X, Y, and Z principal geometric axes that, generally speaking, lie respectively in one of three mutually perpendicular planes. When in position for initiating the grinding operation, these three axes intersect at a common point; and in some operations the three axes are mutually perpendicular, while for other grinding operations certain of the machine elements initially corresponding with said geometric axes may be moved into oblique positions.

The vertical Z axis and the horizontal X axis are established by major machine elements, but these machine elements are each independently movable to obtain the necessary flexibility of three-dimensional movement required for proper grinding of the cutters.

Means are provided for feeding the cutter toward and away from the grindwheel by swinging the Z axis in a short horizontal arc about a second vertical axis identified as 2:. The machine parts whose axis initially defines the X axis may be perpendicular to the Y axis in any station; but means may be provided to enable these X axis part to be swung in a horizontal are about the Z axis to a position other than perpendicular to the Y axis for some types of grinds. The Y axis is not represented by a tangible machine element and so may be regarded as being horizontal and movable vertically with the X axis to intersect the X axis at all times.

The nose of a ball end mill has the rake angle provided by grinding the side face of a land at the second station. The movement of the cutter is carefully controlled to grind a smooth surface on the nose of the cutter that blends without interruption into the relatively tangential face of the land along the side of the cutter. This side face ofthe land is then used as a guide or template which is engaged and followed by a tooth rest at the third station as the primary and secondary reliefangles are ground on the land.

The grindwheel is rotatably mounted to revolve about a vertical axis parallel to and spaced along the Y axis from the Z axis. The axis of the grindwheel is fixed during grinding operations but is adjustable to compen sate for wear of the grindwheel.

The cutter is mounted in a tool holder which, in turn, is mounted in a work head adapted to position the tool holder initially with the longitudinal axis of the cutter horizontal and in the Y-Z plane, or parallel thereto. Means are provided for swinging the tool holder and cutter about the X axis as necessary for various grinds. When the X axis is perpendicular to the Y axis, as at the first station, the cutter axis then moves in the Y-Z plane. Means are provided for turning the tool holder and cutter therein about the axis of the cutter, this means differing from station to station according to the function to be performed. At the first station, rotation of the tool is continuous during grinding; but at the other two stations this angular movement of the tool may be regarded as intermittent. Both the second and third stations have in common the indexing movement of the tool by the work head to advance the lands in succession into grinding position.

BRIEF DESCRIPTION OF THE DRAWINGS How the above objects and advantages, as well as others not specifically mentioned, are achieved will be better understood by reference to the following description and to the annexed drawings, in which:

FIG. I is a diagrammatic plan view showing the grinding system comprising three separate stations;

FIG. 2 is a front and side perspective of the grinder at station No. I, the grinders at stations No. 2 and No. 3 being substantially the same;

FIG. 3 is a side elevation of the machine of FIG. 2 with the upper portion of the housing broken away;

FIG. 4 is an enlarged view, taken from FIG. 3, of a part of the mechanism for imparting motion to the work head and the support column therefor;

FIG. 5 is a vertical section through the column supporting the work head taken on line 55 of FIG. 4;

FIG. 6 is a fragmentary vertical section showing the work head and the upper portion of the column supporting the work head, taken on line 6-6 of FIG. 3;

FIG. 7 is a combined plan view and section of the work head support at station No. 2 or No. 3 as if taken partially on line 7-7 of FIG. 6;

FIG. 7a is a fragmentary elevation similar to FIG. 6 showing the tooth rest employed at stations No. 2 and No. 3;

FIG. 8 is a plan view of the work head and motor at station No. 1, taken on line 8-8 of FIG. 6;

FIG. 9 is a vertical section through the work head and the tool holder taken on line 9-9 of FIG. 8;

FIG. 10 is a combined elevation and median section through the tool holder with a cutter in place in the'tool holder;

FIG. 11 is an enlarged fragmentary side elevation, viewed as in FIG. 3, of the mechanism for pivoting the work head (A rotation) about a horizontal axis;

FIG. 11a is a fragmentary side elevation similar to FIG. 11 at reduced scale showing the work head tilted forward to the initial or loading position;

FIG. 12 is a schematic view in perspective of the grindwheel, the work head, and the column on which the work head is mounted, together with the mechanism for producing the desired movements of the work head relative to the grindwheel, characteristic of all three stations;

FIG. 12a is a fragmentary perspective, similar to a portion of FIG. 12, showing the work head tilted forwardinto the initial orloading position;

FIG. 13 is a fragmentary side elevation of the end of a ball end mill;

Flg. I4 is an end or top plan view of the ball end mill of FIG. 13;

FIG. 15 is a diagram showing the geometric relationships of the several design axes and the directions of offset and movements of the cutter relative to the axes;

FIG. 16 is a series of three schematic views showing successive positions of an end mill while undergoing a radius and outside diameter grind at station No. l;

. FIG. 17 is a series of schematic views showing four successive positions of an end mill while undergoing gashing at station No. 2;

FIG. 17A is a fragmentary median section at the periphery of the grindwheel at station No. 2;

FIG. 18 is a series of schematic views showing four successive positions of an end mill while grinding relief angles at station No. 3;

FIG. 19 is a front elevation of the indexing type of work head at stations No. 2 and No. 3 tilted to initial or loading position;

FIG. 20 is a horizontal section through the indexing work head on line 20-20 of FIG. 19;

Claims

1. A mill grinder for machine tool cutters constructed with reference to X, Y, and Z geometric axes that are mutually perpendicular and intersect at a common point, comprising in combination: a frame; a grindwheel rotatably mounted on the frame to revolve about an axis parallel to and spaced from the Z axis; a work head including tool holding means, the tool holding means mounting a cutter in the work head for movement of the cutter about the longitudinal axis of the cutter; means mounting the work head on the frame for independent movement about the X axis and for movement along the Z axis with the axis of the cutter coincident with the Z axis; motor means for turning the tool holding means and the cutter about the axis of the cutter; motor means moving the work head to feed the cutter into and out of engagement with the grindwheel; motor means traversing the work head along the Z axis with the cutter axis coincident with the Z axis; and motor means for swinging the tool holder and cutter about the X axis.

2. A grinder for cutters according to claim 1 in which the tool holder and cutter swing about the X axis through an arc of substantially 90*.

3. A grinder for cutters according to claim 1 including means for forming said cutter with a plurality of circumferentially spaced flutes that define cutter teeth, and in which the Means for turning the cutter includes means to index the cutter by angular increments determined by the number of flutes on the cutter.

4. A grinder for cutters according to claim 3 which also includes a tooth rest engageable with the cutter, and in which the means for turning the tool holding means is reversible and rotates the cutter in one direction to index the cutter and rotates the cutter in the opposite direction against the tooth rest to grind a surface on a land of the cutter.

5. A grinder for cutters according to claim 1 in which the means for feeding the cutter into and out of engagement with the grindwheel includes means swinging the work head forward and back in an arc about an axis parallel to but offset from the Z axis.

6. A grinder for cutters according to claim 1 that also comprises means adjustably mounting the grindwheel on the frame for compensatory movement of the grindwheel axis toward and away from the Z axis and along the Y axis.

7. A grinder for cutters according to claim 1 including means adjustably mounting the work head on the frame for movement of said common point of intersection of the axes relative to the cutter along a locus lying at 45* to the Y axis.

8. A grinder for cutters according to claim 1 in which the means for turning the cutter includes motor means for rotating the cutter continuously while the cutter is in engagement with the grindwheel.

9. A mill grinder for machine tool cutters constructed with reference to X, Y, and Z axes that are mutually perpendicular and intersect at a common point, comprising in combination: a frame; a grindwheel rotatably mounted on the frame to revolve about an axis parallel to and spaced from the Z axis; a work head including tool holding means, the tool holding means mounting a cutter in the work head for movement of the cutter about the longitudinal axis of the cutter, said point of intersection of said X, Y and Z axes lying on the longitudinal axis of said cutter in the tool holder; means mounting the work head on the frame for independent movement about the X axis and along the Z axis; motor means for turning the tool holding means and the cutter about the axis of the cutter; motor means moving the work head to feed the cutter into and out of engagement with the gindwheel; motor means traversing the work head along the Z axis; and motor means for swinging the tool holder and cutter about the X axis.

10. A mill grinder for machine tool cutters constructed with reference to X, Y, and Z axes that are mutually perpendicular, comprising in combination: a frame; a grindhweel rotatably mounted on the frame to revolve about an axis parallel to and spaced from the Z axis; a work head including tool holding means, the tool holding means mounting a cutter in the work head for movement of the cutter about the longitudinal axis of the cutter; means mounting the work head on the frame for independent movement about the X axis and along the Z axis; motor means for turning the tool holding means and the cutter about the axis of the cutter; motor means moving the work head to feed the cutter into and out of engagement with the grindwheel; motor means traversing the work head along the Z axis; and motor means for swinging the tool holder and cutter about the X axis between an initial position in which the cutter axis is coincident with the Y axis and a subsequent position in which the cutter axis is coincident with the Z axis.

11. A mill grinder for machine tool cutters constructed with reference to X, Y, and Z axes that are mutually perpendicular, comprising in combination: a frame; a grindwheel rotatably mounted on the frame to revolve about an axis parallel to and spaced from the Z axis; a work head including tool holding means, the tool holding means mounting a cutter in the work head for movement of the cutter about the longitudinal axis of the cuttEr; means mounting the work head on the frame for independent movement about the X axis, along the X axis and along the Z axis; motor means for turning the tool holding means and the cutter about the axis of the cutter; motor means moving the work head to feed the cutter into and out of engagement with the grindwheel; motor means traversing the work head along the Z axis; motor means traversing the tool holder and cutter therein along the X axis; and motor means for swinging the tool holder and cutter about the X axis.

12. A grinder for cutters according to claim 11 in which the tool holder moves between an initial position with the tool holder axis parallel with the Y axis and a final position with the tool holder axis parallel with the Z axis after said swinging motion about the X axis.

13. A grinder for cutters according to claim 11 in which the tool holder positions the cutter axis initially parallel to but offset from the Y axis and after swinging about the X axis positions the cutter axis parallel to but offset from the Z axis.

14. A grinder for cutters according to claim 13 which also comprises means for traversing the cutter along the Z axis holding the cutter axis parallel to but offset from the Z axis.

15. A machine tool cutter grinder comprising in combination: a frame; a grindwheel and motor means driving the grindwheel mounted on the frame; a work head; a tool holder adapted to hold a cutter and rotatably mounted in the work head to turn the cutter about the longitudinal axis of the cutter therein; means mounting the work head on the frame, for controlled movement of the work head relative to the grind-wheel, said mounting means comprising a post having its longitudinal axis vertical and mounted for oscillation about its axis, said post having a laterally extending arm; a block pivotally connected to said post arm to swing relative to the post about a second vertical axis; and means pivotally connecting said work head to the block to move about a horizontal axis intersecting said second vertical axis; and motor means for swinging the work head and cutter about said horizontal axis.

16. A cutter grinder according to claim 15 that also includes means on the work head providing rectilinear movement of the tool holder and cutter relative to said block in horizontal and vertical directions.

17. A cutter grinder according to claim 16 in which the horizontal and vertical movements of the work head and cutter are respectively parallel to and perpendicular to said horizontal axis about which the work head is mounted on the block.

18. A cutter grinder according to claim 15 which also comprises means raising and lowering the post along its vertical axis.

19. A cutter grinder according to claim 15 that also comprises means for adjustably positioning the grindwheel toward and away from a cutter in the tool holder by movement in a direction parallel to a vertical plane containing the axis of revolution of the grindwheel and the axis of the cutter.

20. A cutter grinder according to claim 15 that also comprises motor means carried on the work head for continuously rotating the tool holder with the cutter in contact with the grindwheel.

21. A cutter grinder according to claim 15 that also includes indexing means on the work head that turn the cutter by angular increments in response to the number of flutes on the cutter.

22. A cutter grinder according to claim 21 that also includes means for keeping one land on a cutter in grinding engagement with the grindhweel during downward movement of the post along the first mentioned vertical axis.

23. A cutter grinder according to claim 15 that also comprises means for swinging the block and work head together about said second vertical axis.

24. An end mill grinder according to claim 23 in which the grindwheel is a shaped wheel having a circumferentially extending ridge. means mounting tHe work head on the frame for independent movement about the X axis, along the X axis and along the Z axis; motor means for turning the tool holding means and the cutter about the axis of the cutter; motor means moving the work head to feed the cutter into and out of engagement with the grindwheel; motor means traversing the work head along the Z axis; motor means traversing the tool holder and cutter therein along the X axis; and motor means for swinging the tool holder and cutter about the X axis.

25. A grinder constructed with reference to X, Y, and Z axes that are mutually perpendicular and intersect at a common point for forming a cutter with a plurality of circumferentially spaced flutes that define cutter teeth comprising in combination: a frame; a grindwheel rotatably mounted on the frame to revolve about a vertical axis parallel to but spaced from the Z axis; a holder for holding a cutter to be ground; a work head mounting the cutter holder for turning movement about the axis of the cutter therein; means for mounting the work head on the frame and moving the work head both angularly and linearly with respect to the grindwheel, means for mounting the work head angularly about the X axis, and means for placing the cutter axis coincident with the Z axis.

26. A grinder for grinding the cutting end and the shank of a fluted end mill comprising, in combination: a frame; a power driven grindwheel supported by the frame, said grindwheel having an annular grind surface; a workhead supported on the frame, said workhead including a work holder mounting an end mill in said workhead for rotation on the longitudinal axis of the end mill; a drive motor for constantly rotating said end mill in said head on its said longitudinal axis; means for placing said workhead and end mill held therein relative to said grinding surface in a position with the cutting end of said end mill bearing against said annular grinding surface, and with the longitudinal axis of the end mill normal to said annular grinding surface at the point of engagement; means for effecting a movement of said workhead relative to said grinding surface, between said position and a second position, said movement comprising a relative swing of said end mill about a swing axis which is perpendicular to said longitudinal axis of said end mill and which intersects the end mill at a distance from the extremity of the cutter end of the end mill which is no greater than half the radius of the end mill, such swing being of an angular extent of the approximate order of a right angle; and means for translating said end mill along its longitudinal axis between said second position and still another position, in order to grind the shank of the end mill along the fluted length thereof.

27. The subject matter of claim 26, wherein a ball end mill is to be ground, and said swing axis intersects the longitudinal axis of the end mill, and wherein the point of intersection of said axes is located a distance from said extremity of the end mill substantially equal to the radius of the shank of the end mill, said swing axis being at right angles to the direction of said translation.

28. The subject matter of claim 26, wherein a flat end mill is to be ground, said swing axis intersecting the end mill substantially at the intersection of the flat cutter end of the end mill and the side surface of the shank thereof, and being at right angles to the direction of said translation.

29. The subject matter of claim 26, wherein the cutter end of the end mill is to be ground with a radius between its shank surface and cutter end which is less than that of the shank of the end mill, said swing axis intersecting a center point about which such radius is struck, being at right angles to the direction of said translation.

30. A grinder for end mill cutters, constructed with reference to mutually perpendicular Geometric reference axes X, Y and Z, comprising in combination: a frame in fixed relation to said X, Y and Z axes; a grindwheel rotatably mounted on the frame to revolve about an axis contained in the Y-Z plane; a workhead including holding means for an end mill cutter, said holding means mounting an end mill cutter for movement of the cutter about its longitudinal axis; means mounting the workhead relative to the frame for pivotal movement about an axis perpendicular to the Y-Z plane and in the vicinity of the X axis; means mounting the workhead relative to the frame for pivotal movement about said Z axis; means positioning the cutter holder on the workhead with its longitudinal axis in a plane offset from the X-Z plane; means for pivotally moving the workhead about said axis perpendicular to said Y-Z plane; and means for pivotally moving the workhead about said Z axis.

31. The grinder of claim 30, wherein said grindwheel axis is substantially parallel with said Z axis.

32. The grinder of claim 30, including also feed and retract means supporting said workhead and its mounting means for pivotal movement towards and from said grindwheel, about an axis parallel to said Z axis.

33. A cutter grinder as in claim 25 in which the work head mounting means also includes: means mounting the work head for feeding the cutter toward and away from the grindwheel by swinging movement about a vertical axis parallel to but offset from the Z axis.

34. A cutter grinder as in claim 25 which also comprises: a tooth rest engaging the cutter during grinding; and the work head includes means for turning the cutter in a direction to maintain contact of the cutter with the tooth rest during grinding.

35. A cutter grinder as in claim 34 in which the work head includes reversible motor means for turning the cutter to engage and disengage the tooth rest.

36. A cutter grinder as in claim 25 which includes means indexing the cutter by angular increments equal to the angle between successive flutes.