Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
  • B23H9/14—Making holes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
  • B23H7/02—Wire-cutting
  • B23H7/08—Wire electrodes
  • B23H7/10—Supporting, winding or electrical connection of wire-electrode
  • B23H7/101—Supply of working media
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2200/00—Details of cutting inserts
  • B23B2200/36—Other features of cutting inserts not covered by B23B2200/04 - B23B2200/32
  • B23B2200/3618—Fixation holes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2226/00—Materials of tools or workpieces not comprising a metal
  • B23B2226/12—Boron nitride
  • B23B2226/125—Boron nitride cubic [CBN]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B2226/00—Materials of tools or workpieces not comprising a metal
  • B23B2226/31—Diamond
  • B23B2226/315—Diamond polycrystalline [PCD]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H2200/00—Specific machining processes or workpieces
  • B23H2200/20—Specific machining processes or workpieces for making conical bores
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H5/00—Combined machining
  • B23H5/04—Electrical discharge machining combined with mechanical working
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
  • B23H7/02—Wire-cutting

Definitions

• PCBN polycrystalline cubic boron nitride
• PCD polycrystalline diamond
• the method produces a plurality of tool inserts from a body of polycrystalline superhard material, in particular polycrystalline diamond and polycrystalline cubic boron nitride on top of a tungsten carbide/cobalt composite substrate, having major surfaces on each of opposite sides thereof.
• the method includes the step of simultaneously producing at least two holes in the body, each hole generally extending from one major surface to the opposite major surface.
• the holes are produced by using a laser machine, wire electrical discharge machine and electrical discharge grinding machine.
• the body is severed between the holes along with the relief angles to produce the plurality of tool inserts.
• An advantage of the method includes the minimization of the use of electrical discharge grinding of the entire profile of the hole.
• the inserts manufactured meet ISO standards regardless of the grade of superhard material. Also, a plurality of electrodes is not required, thereby maximizing the disc utilization. Severance of insert with the relief angle minimizes the finish tool-grinding to be performed on the insert.
• desirable cutting inserts include those tools in which the edges are superhard and processes such as brazing in the manufacture of the finished insert are eliminated.
• This requirement is partially fulfilled by fully solid inserts formed from a homogenous monolithic body of superhard materials. Normally, these inserts allow cutting edges on both the top and bottom surfaces of the insert, contributing to the economic benefit of their use. In other words, they tend to be used mostly in "negative" geometries where the side faces of the inserts are perpendicular to both the top and bottom of the insert.
• a solution to these problems is an insert with an integral clamping hole.
• Such an insert also increases the number of usable edges from a single tip to tips at every corner on the top face. It also allows for more compactness.
• the integral clamping hole allows more inserts to be stacked for a given diameter, because of the room gained by eliminating top-clamps. A greater number of inserts in the cutter would allow greater feed-rate of cutting and consequently greater productivity.
• an insert with an integral clamping hole dictates that the amount of superhard material to be ground is of the order of the insert dimensions itself, likely resulting in higher grinding cost and time.
• steps are required to reduce this cost: 1 ) the raw insert presented to the tool- grinder is as close to the final desired shape and dimensions as feasible; and 2) the amount of grindstock on the insert is reduced down to the depth of subsurface damage caused by insert severing processes such as WEDM and laser. To achieve this, the manufacturing process to produce this raw insert is designed to eliminate all geometrical form errors.
• the three key geometrical criteria are a) perpendicularity of the axis of the integral clamping hole to the insert top, b) concentricity of the through- hole to the inscribed circle of the insert and c) proximity of edge damage on the through-hole entrance. Criteria a) and b) are important to ensure that the amount of grindstock on each side of the insert is the same. Criterion c) is important to ensure that an adequate amount of superhard material is available for incorporating a suitable chamfer and/or hone to the cutting edge and the integrity of the insert itself. Both a) and b) may be eliminated if the operation of severance of the insert and finishing of the through-hole are performed in the same setup on the same WEDM machine. Criterion c) may be eliminated if the process of obtaining the profile of the hole involves only WEDM and not electrical discharge with an electrode.
• Figure 1 is an isometric view of a disc of polycrystalline ultra-hard material illustrating an embodiment.
• Figure 2 is an isometric view of the embodiment in Figure 1 showing the process of severance of individual inserts from the pattern of holes in the ultra-hard polycrystalline disc.
• Figure 3 is an isometric view of a single insert severed from the body.
• Figure 4 is the cross-sectional view of the insert in Figure 3.
• Figure 5 is a photograph comparing the insert an embodiment to an insert formed from alternative techniques which involved incorporation of a hole after the insert was cut from the parent body.
• Figure 6 is a photograph comparing the insert of an embodiment to an insert without the top-taper showing edge degradation due to the electrical discharge grinding process performed directly on the superhard surface of the body.
• Figures 7(a) through Figures 7(d) show a sequence of steps of production of an embodiment.
• Figure 7(a) shows the parent body and axis of hole-location;
• Figure 7(b) shows the body with the pilot-hole cut with the laser machine;
• Figure 7(c) shows the finishing of the through-hole and cutting the top-taper and
• Figure 7(d) shows the finishing of the countersink.
• Figure 8 shows the process of severing entrapped conical internal part in several radial fragments.
• Hole refers to a cylindrical or non-cylindrical opening into and through an object.
• Counterink refers a non-conical curved enlargement below the entrance of a hole.
• WEDM wire electrical discharge machine
• EDG electrical discharge grinding machine
• Laser laser machine
• Hard-layer refers to the portion of the thickness of the insert comprising of the ultra-hard material.
• Carbide-layer refers to the portion of the thickness adjacent the hard- layer.
• Pilot-Hole refers to the initial hole, smaller in diameter to the final required cylindrical through-hole, allowing the wire of the WEDM to pass through.
• Inscribed Circle refers to the hypothetical circle such that it is either tangent to the all sides of the insert, if the insert is polygonal or coincides with the boundary of the insert, if the insert is round.
• Superhard material refers to a material that has a Knoop hardness of at least about 4000. This includes sintered polycrystalline diamond and other diamond, diamond-like materials, cubic boron nitride and wurzitic boron nitride.
• An embodiment includes a method of making a plurality of tool inserts from a body of ultra-hard material which has major surfaces on each of opposite sides thereof, includes the steps of producing a plurality of spaced holes and countersinks in the body, each hole generally extending from a first major surface to the opposite second major surface.
• the ultra-hard material will generally be polycrystalline diamond (PCD) or polycrystalline CBN (PCBN) and may be bonded to a substrate such as a cemented carbide substrate.
• the ultra-hard material bonded to a substrate is defined as the body.
• the holes and countersinks will generally extend through both the polycrystalline ultra-hard material and the substrate. Severing between the holes to produce the inserts will also extend through both the polycrystalline ultra-hard material and the substrate.
• the body will generally take the shape of a disc whose diameter may range in size from about 50 mm to about 65 mm or more.
• the pilot-holes may be produced using a laser machine which penetrates the surface exposed to it and drills a through-hole in the material underneath.
• the opening is then profiled to shape using a wire electrical discharge machine and an electrical discharge grinding machine.
• the body is carried from laser machine, wire electrical discharge machine and electrical discharge grinding machine without loss of coordinate references so that the holes and countersinks can be produced without loss of concentricity.
• polycrystalline ultra-hard material has a major surface 12 and an opposite major surface 14. At least one pilot-hole or a plurality of pilot-holes 16 may be produced in the body 10. The holes extend from the major surface 12 to the opposite major surface 14.
• a plurality of tool inserts is then produced by severing inserts from the body 10, e.g. using EDM cutting or laser cutting, along the lines 18 (see Figure 2). This results in 49 tool inserts, each with a polygonal or curvilinear shape, being produced. Each insert has a centrally located through-hole or countersink 16 extending through it. Each insert is thus capable of being clamped to a tool holder using a screw or pin lock clamping means.
• the thickness of the inserts may range from about 1 .5 mm to about 5.0 mm with through-hole diameters ranging from about 2.15 mm to about 8.0 mm having a through-hole diameter tolerance of about +/- 0.02 mm and a concentricity of less than about 0.02 mm or about 0.02 mm.
• the inscribed circle of the insert may be about 0.02 mm.
• a finished tool insert is shown in Figure 3 and comprises a layer 12 of polycrystalline ultra-hard material bonded to a substrate, typically a cemented carbide substrate, 14.
• a through-hole or countersink 16 extends from the top surface of the layer 12 to the bottom surface of the substrate 14.
• the hole or countersink 16 has a wider diameter at the top surface resulting in a recess which can accommodate the head of a screw.
• the method of producing at least one hole or countersink in a body includes the steps shown in Figures 7a through 7d. As shown in Figure 7a, a body 28 is affixed to a dedicated fixture having a holder and a pallet which position and orient the body relative to each other with high accuracy.
• Identical pallets are installed in each of the 3 machines laser, WEDM and EDG.
• the dedicated fixturing also ensures a high level of perpendicularity between the hole-axis and the insert top surface.
• At least one pilot-hole 28 is formed using a laser to produce the body 30 from 28.
• the laser may be a LASAG laser manufactured by Lasag Lasers, Buffalo Grove, IL.
• the pilot-hole extends from the first major surface 12 to the opposite second major surface 14 of the body 10.
• a straight hole 26 and top taper 22 are formed using a WEDM to obtain the body 32.
• the EDG forms a curved non-conical countersink surface 24 to obtain the body 34. Note that in this step, the EDG erodes only the carbide substrate ending in surface 14. Finally, the body is severed along the lines 18 of Figure 2 on the WEDM as shown in along the surfaces 18 forming the relief of the insert.
• the method minimizes the use of electrical discharge grinding of the entire profile of the hole, since different grades of PCD and PCBN offer different resistances to electrical erosion.
• the body is carried from machine to machine without loss of references so that position and orientation in each machine is maintained. This obviates the need for a plurality of electrodes as mentioned above. A plurality of electrodes most likely entails that the electrodes be spaced more than the individual inserts can be in the body, resulting in reduced body utilization. This portability feature in the current method is also useful for part scheduling for each machine, allowing different machines to work concurrently. Concentricity and perpendicularity of the hole are accurate to the order of the positioning accuracies of the WEDM.
• the conical part formed inside the hole while forming surface 22 (Figs. 7c and 7d) and the finished insert itself is ejected upwards by suitably positioning and adjusting the nozzles of the WEDM.
• the top nozzle is made to shut-off automatically and the bottom nozzle is made to increase in pressure so that, without the risk of electrical shorting, the entrapped pieces are ejected. Electrical shorting results in excessive downtime and operator intervention.
• a short circuit due to the entrapped conical portion may also be avoided by the cutting the conical part in segments so that each of the segments or fragments are smaller than the cylindrical portion of the through-hole 26 (Figs. 7c and 7d). This would allow the fragments to fall down through the hole by gravity thereby
• the method has a number of advantages in producing tool inserts capable of being used in a screw or pin lock arrangement. Maximal accuracy is obtained in the location of the locking hole relative to the cutting point, both in manufacture and application of the insert. As cutting tool materials are used for precision machining, accuracy is extremely important in obtaining optimum performance.
• Figure 5 illustrates the accuracy in concentricity achieved with the present method. High accuracy in concentricity is necessary to minimize the grind-stock to be allowed on the insert for finish-grinding. Lower the grind- stock, lesser the grinding costs and time encumbered.
• the insert obtained with the present method is in strict conformance to ISO standards for inserts with partly cylindrical holes. See ISO 6987:1998 "Indexable hard material inserts with rounded corners, with partly cylindrical fixing hole— Dimensions”.
• Figure 6 shows the superior edge quality of the entrance achieved with the present method over alternative method.
• the EDG process does not erode the hard-layer, it is left intact from the WEDM process which creates the surface 22. Hence, the hard-layer does not suffer extra damage due to the EDG process.
• a related benefit to the process design in the present method is that the tapered surface of the screw fastening the insert to the tool-holder rests only the carbide countersink below surface 22. Therefore, the hard-layer is not subjected to added stresses due to the fastening action itself, which may hamper tool-performance.
• a plurality of cutting inserts as illustrated by Figure 3 and Figure 4 were produced from a disc comprising a layer of polycrystalline CBN with a high content of CBN bonded to a cemented carbide substrate.
• the disc was held in dedicated fixturing to transport between the laser, WEDM and EDG.
• Machining time was three minutes per hole. Thereafter, the disc was severed along sever lines between the 18 holes to produce cutting inserts, each of the type illustrated by Figure 3 and Figure 4. Severing was achieved using WEDM.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Cutting Tools, Boring Holders, And Turrets (AREA)

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Citations (5)

• 2011
  • 2011-12-22 RU RU2013135718/02A patent/RU2013135718A/ru not_active Application Discontinuation
  • 2011-12-22 WO PCT/US2011/066717 patent/WO2013112117A1/fr not_active Ceased

Patent Citations (5)

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