MXPA99000190A - Indexable insert router - Google Patents

Abstract

A high-speed end-milling router (10) for ramping entry into a workpiece has plate-like hard metal cutting inserts (28) fitted in pockets (30) milled in chip gullet surfaces (24) to present the insert at a desired axial rake angle and with radially inwardly and outwardly facing cutting edges (34, 36, 38, 40). Each insert is secured in its pocket by two countersink headed machine screws (43, 43) whose holding power against centrifugal dislodgement of the insert is reinforced by a projection (46) from the seating surface (48) of the pocket extending into a blind recess (44) molded in the undersurface (41) of the insert.

Description

INDEXABLE INSERT BREATHER Description This invention relates to milling machines, and more especially to milling machines which are, in effect, high-speed end mills of high metal removal capacity, such as those used to manufacture integral skeleton frames for aircraft components from of plates or ingots of aluminum alloy by milling. Background of the Invention In this demanding service, where the tools are brought to their limits, a 2-inch boring machine that rotates at 20,000 rpm will be driven at feed rates to extract the maximum energy available from the spindle, in some cases at feed rates up to 400 inches per minute when using machine spindles capable of 100 horsepower. The high rates of metal removal and the high centrifugal forces encountered are not in themselves the most rigorous aspect of such high-speed milling, which occurs rather when the entrance to the work piece is blocked by ramp formation, of which such tools must be capable. That is, the tool must be able to enter the work piece by axial penetration of its surface without prior preparation of the work piece by drilling. This is accomplished by feeding the rotary tool both axially and laterally, either simultaneously or alternately in repetitive steps, procedures that require a cutting ability of each cutting insert in both radial directions, ie outward and inward. The last cutting action, using the cutting bore that looks radially inward of the insert, results in a reaction to the cutting force on the insert whose radial component is outward, acting in an additive manner to the centrifugal force without the benefit of any inwardly directed, compensating component of the cutting edge facing outward, which is under vacuum at the half revolution during which it cuts the cutting edge which faces inward. If the ramp feeding is aggressive, the added load on the seal of the insert can be substantial, increasing the danger of separation of the insert from the tool body at high speed. Insofar as the problem has been recognized by the state of the art, it has been satisfied by forming the inserts and insert cavities of the tool body with interlinkable projections and integral recesses, respectively, in one case a projection similar to keel in the insert that is received in a cut milled in the seat surface of the cavity. However, such measures are difficult to control in manufacturing, and stress the hard metal projections of the insert in a manner in which that material is not the most suitable to withstand. Accordingly, it is the object of this invention to provide a simple, easily manufactured, interlock reinforcement, from the attachment of the inserts to heavy duty, high speed burying machines, to enable them not only to withstand the high centrifugal forces encountered, but also also the added force on the inserts of the insert that result from the entrance by ramp formation towards the work piece. SUMMARY OF THE INVENTION In chippers according to the invention, the plate-like inserts are secured in their respective cavities by two counter-recessed head seals associated with the counter-depressed surfaces of two transverse holes of the inserts, and the underside or the seat surface of the insert is recessed in the form of a blind hole placed between the two retainer holes. A mating projection of the seat surface of the insert cavity of the chisel body seats itself in the recess with such a clearance so as to link the wall of the recess when the insert retainers deform under the applied loads, serving to reinforce the seals only when sufficient deflection of the seals occurs and without interfering with the proper seating of the insert by being secured in place by its seals. DESCRIPTION OF THE DRAWINGS The preferred embodiment of the invention is illustrated in the accompanying drawings, in which: Figure 1 is an elevational view of the milling machine of the invention; Figure 2 is a bottom view thereof; Figure 3 is a side view, partly in sections, to show an important aspect of the invention; Figure 4 is a series of four orthogonal views of the indexable cutting insert of the invention, the view (a) showing the tilt angle face, the view (b) being a side view, the view (c) showing the face of settlement, and the view (d) being an end view of the insert; and Figure 5 is a sectional view of a workpiece in relation to the burr of the invention, shown in fragmentary elevation after removal of a depression milled in the work piece by the so-called ramp formation input of the tool rotating DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE PREFERRED EMBODIMENT The milling machine 10 of the invention, in the preferred form, is shown in its entirety in figures 1, 2 and 3. The milling machine comprises two essentially cylindrical sections, integrally connected, namely a sugar cane. traction 12 and a cutting head 14. The traction rod is configured for attachment linkage by a so-called HSK adaptation attachment, not shown, which in turn is designed to be handled and placed on the spindle of a machine head by a changer automatic tools For its adjustment within the adaptation, the shank 12 is rotated with a cut-out 16 in its connection with the integral cutting head 14 so that the shank can be milled cylindrically true. The shoulder 18 of the cutting head is similarly milled flat and truly perpendicular to the axis 20 of the tool, since these surfaces are the surfaces of the tool location with respect to the aforementioned adaptation, and through them to the high speed equipment in which the tool must be dynamically balanced for use at 20,000 rpm. The cutting head 14, in the illustrated tool diameter, is slightly larger in diameter than the shank 12. At its free end, its corner is rounded, and an axial depression 22 in the shape of a truncated cone is converted into the face of end to provide free space for entry by ramp formation of the router to a workpiece at the angle OI indicated in Figure 1 and again in Figure 5. Identical, diametrically opposed chip slivers 24 are milled in the cutting head so as to provide a flat surface 26 disposed at a desired axial inclination angle ß of the two cutting inserts 28 which are seated in recesses 30 milled in the flat surface 26 of each chip throat. Cutting coolant is fed from the spindle of the machine head to the cutting area of the router 10 through an axial hole 31 which serves as a fluid conduit. The cutting inserts 28 of sintered hard metal (WC) are shown separately in the four views of the group of figure 4, figure 4 (a) showing that larger face constituting the side of inclination angle 32 of the insert, which takes the form of an elongated, flat plate of plant usually rectan¬ # gular. Two diagonally opposed corners are removed to provide diagonal cutting edges 34, which look radially inward when mounted on the cutting head 14 by indexing each in turn to the cutting position by turning the insert end-to-end. The diagonally opposite corners 36 remaining can have radii, as shown, or left square, as indicated at the bottom end of Figure 4 • (a), or round to a greater or lesser radius than the one shown, depending on the work requirements. In any case, the insert 28, in any of its indexed positions, minimally provides the inwardly facing cutting edge 34 mentioned above, an end or lower cutting edge 38, and a side cutting edge 40, the latter two being joined by the rounded or circular cutting edge 36 in the "cutting inserts selected for milling in fillet of blind holes or cavities.

The edge surfaces of the insert move away from the cutting edges of the tilting angle face to the smaller but conformable, opposite major face 41, which is the seating surface of the insert. Edge surfaces that move away from the insert provide clearance behind the cutting edges for axial and radial feed of the tool, the free space angle on the diagonal edge surface behind the diagonal cutting edge facing inward 34 being less than those behind the other cutting edges to increase their resistance to dislocation of the upper end of the insert cavity by the centrifugal force when in the upper end position, not cutting (see figure 1). The insert 28 is molded with two transverse holes 42 in the long axis of the insert, which are equi-spaced from the ends of the insert, and counter-depressed from the inclination angle face 32 to receive a pair of retaining screws. counter-sunken head 43. Between the two holes 42 for the retaining screws, and generally on the long axis of the insert, a recess 44 in the form of a blind hole is molded on the seat surface 41 to receive a pin 46 which it projects from the seat surface 48 complementary to the insert cavity 30 of the cutting head. Returning to the cutting head 14, and especially to FIGS. 1 and 3, the insert cavity 30 is milled towards the flat surface 26 of the chip throat 24 so as to conform to the edge or free space surfaces of the edge of the chip. inactive side cut 40 and the inactive diagonal cutting edge 34. As best seen in Figure 1, the inactive or upper end of the insert fits like a wedge between the edge surfaces that conform the cavity that link the surfaces of lateral and diagonal free space of the insert, this last surface being restrained against movement radially outward by the peninsular extension 50 of the cavity wall. The retaining screws 43 are received in capped holes 52 that are generally or almost perpendicular to the seating surface 48 of the cavity. That is, the retaining screws use the "bent screw" principle of U.S. Patent No. 3,662,444, to Erkfritz, which is incorporated herein by reference. The axes of the screw holes are edged at about 2 ° in one direction to urge the lateral insert _ and firmly into engagement with the edge surfaces of the cavity, which appropriately positions the various cutting edges of the insert. By linking the counter-recessed head of the screw the counter-recessed surface of the hole in the insert, the screw shank is bent to maintain the push towards the sides of the insert against the walls of the cavity's location, as well as to hold the insert tightly on its seat surface 48. The transverse holes 42 of the insert are intentionally molded of excessive size to accommodate the bending of the screw, all the parts being dimensioned to maintain the bending tension on the screws within their elastic limits. In the case of the screws furthest from the free end of the cutting head, the direction of the lateral thrust is diagonally inward and upward, as shown by the arrow in Figure 1, so as to wedge the insert more securely between the facing surfaces of the opposite edge at the upper end of the cavity. The lateral thrust of the lower screw is directed radially inward, as also indicated by an arrow. Between the two screw holes 52 in the cutting head, a hole 54 is drilled and flaring perpendicular to the seating surface 48 of the cavity to receive the pin 46, preferably a rolling pin, in a tension fit. The pin 46 is driven from the cavity end of the hole 54 and allowed to protrude so as to seat itself in the depression 44 in the seat surface of the insert, preferably with lateral clearance not exceeding a total of 0.010 inches, of way not to interfere with the proper seat of the insert, as described. However, in case of additional deformation of the retaining screws, particularly the lowermost screws, under the centrifugal force and under the reaction to the additional radially outward cutting force at the diagonal cutting edge, directed inwards 34 during the Entrance by ramp formation to the work piece, illustrated diagrammatically in Figure 5, the pin 46 reinforces the retention screws by securing the insert in place. The maximum angle of ramp formation available is illustrated by the angle OI in Figures 1 and 5. It is the angle made with the cutting plane of the end cutting edges 38 by a line between the lower and upper ends, respectively, of the cutting edges facing inward, straight 34 of the opposing inserts of the cutter, assuming an axially inward feed at a rate calculated to cut to full depth of the cutting edges directed inwardly. Even if the ramp formation at a somewhat lower angle would be prudent to avoid clogging the free end of the cutter head in the workpiece, production milling tends to use cutting tools at maximum capacity. The input by ramping the work piece by helical interpolation is the technique illustrated in Figure 5. That is, the rotational axis of the tool is moved by means of numerical control in a circular path to a constant axial feed that determines the angle and inclination of the helical path, illustrated as being somewhat less than the maximum angle of ramp formation. Alternatively, the cutter can be advanced axially and in increments in an alternating cut and then fed laterally to achieve the same result. In another input mode, the reaction to the cutting force exerted by the inwardly directed cutting edge is additive to the centrifugal force, making it highly desirable to reinforce the retaining screws by securing the inserts in the insert cavities at high speeds and Short loads while ramp is formed. For this purpose, the inter-adjusting pin 46 is projected and the mating recess 44 in the seat surface of the cutting insert is provided according to the invention. It will be understood that although the invention has been illustrated in its application to a milling machine having two diametrically opposed slit throats and insert seats, it is equally applicable to scrapers of any number of inserts equally distributed around the periphery, or with other appropriate measures taken for the dynamic balance of the tool. In addition, the counter-sunk head screw used in the manner of the aforementioned Erkfritz patent is also preferred for simplicity.In order to secure the inserts in their cavities, other counter-recessed head seals are known which can provide lateral force as well as similarly directed normal which secures the insert in its cavity. Although a traction adjusting pin is the currently preferred form of projection from the insert surface of the insert cavity to reinforce the insert retainers, other devices, such as cap screws, fixed screws and tail pins of leg can reasonably be suggested as alternatives. Similarly, although the recess 44 on the underside of the insert is shown as a round hole, other forms of depression are functionally equivalent if they have radially opposed walls for solid bonding by projecting from the seating surface under operating conditions in both indexed positions of the insert. Depression forms that suffer from the least distortion by sintering, and having relative freedom of stress concentration are preferred. The characteristics of the invention that are believed to be novel and patentable are indicated in the following claims.

Claims (6)

1. CLAIMS 1. A milling machine for high-speed milling of aluminum alloys to produce integral skeletal structures from ingot workpieces, having: a generally cylindrical cutting head, capable of rotating, having a generally conical recess centered at its free end and multiple flutes equally distributed around the periphery of said cutting head, each flute having a flat surface facing in the cutting direction of the cutter head and milled to provide there a cavity having therein a metal cutting insert. hard, plate-like, indexable end-to-end and replaceable; said insert being elongated in the axial direction of the cutting head and having opposite inclining and seating angled surfaces, said inclined angle surface having elongated cutting side edges, each fusing with an edge of opposite end cutting edges which extend generally radially from the cutting head and occupy the radially external portion of the end of the insert presented for cutting; the remaining portion of each end edge of the insert being presented for cutting away from its end cutting edge associated diagonally to the axis of rotation of the cutting head generally in accordance with the cross section of said recess to present a directed cutting edge radially towards the edge surfaces of said insert moving away from said cutting edges as free space surfaces; said insert, at its opposite end to said presented end being linked along the free space surface of the adjacent diagonal cutting surface and along its side edge surface opposite its edge cutting side presented by walls of conformation of its associated cavity which rise from its seating surface to receive the inactive end of the insert as a wedge between said shaping walls; said insert having two longitudinally spaced holes, centered between said cutting edges, spaced equidistantly from the end edges of the insert, extending through the insert between its inclination and seating surfaces, and counter-depressed from the first of these; a pair of counter-depressed head fasteners placed in said holes to secure each insert in its cavity; said insert also having a recess in its seating surface between said two transverse holes in mating register in both indexed positions with a projection protruding from the cavity seating surface; said projection having a slight free lateral space in said recess when the insert is secured in said cavity by said fasteners; and said free space being selected to bring said projection into engagement with the walls of said recess by the deformation of said fasteners under the forces acting radially outwardly on the insert, thereby reinforcing the fasteners which keep the insert in its cavity.
2. 2. The burr of claim 1, wherein the recess in the seating surface of the insert is a round, blind hole and the mating projection of the surface of the insert. • cavity seat is a bearing pin.
3. 3. The milling machine of claim 2, wherein the two fasteners securing the inserts in the cutter head cavities are machine screws slightly edged so as to be bent when bonding with the surface occurs. 15 counter-recessed transverse holes in the inserts, the most remote screws of the free end of the cutting head • being edged in and up towards the cutting head axis, the remaining screw being edged radially inward, and the inter-adjusting pin having a maximum 20 diametral free space of 0.010 inches in said blind hole.
4. 4. An indexable cutting insert for a high-speed end milling machine capable of entering by ramping a workpiece, comprising: a flat hard metal plate having a profile 25 elongate, generally rectangular, defined by cutting edges circumscribing a larger face of said insert constituting its inclination angle face in each of two indexable positions end to end of the insert; said cutting edges including lateral cutting edges, opposite, in the longer dimension of the insert, end cutting edges, opposite, in the short dimension of the insert, and diagonal cutting edges, diagonally opposite, each contiguous to an edge of end cutting and one of the lateral cutting edges; the opposite major face of the insert being the seat surface of the insert and more glued but conformable in profile to said face of inclination angle; all edge surfaces of said insert converging from said inclination angle face to said seating surface and providing the free space surfaces of said respective cutting edges; a pair of spaced holes which pass through said insert between their larger and counter-sunken faces from said inclination angle face, said holes each placed on the longitudinal center line of the insert and each equidistant from one end of the insert. insert and said insert also having on its seat surface a recess positioned midway between said transverse holes in said longitudinal center line for mating reception of a projection from the receiving surface of a host router.
5. 5. The insert of claim 4, wherein the blind hole is round. The insert of claim 4, wherein said tilting angle face at the intersection of adjacent end and side cutting edges is rounded, and said seating surface similarly, to provide a cutting edge of interconnecting thread between said edges. adjacent end and side cutting edges.