Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q11/00—Accessories fitted to machine tools for keeping tools or parts of the machine in good working condition or for cooling work; Safety devices specially combined with or arranged in, or specially adapted for use in connection with, machine tools
  • B23Q11/0042—Devices for removing chips
  • B23Q11/005—Devices for removing chips by blowing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0692—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by a fluid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
  • B05B1/34—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to influence the nature of flow of the liquid or other fluent material, e.g. to produce swirl
  • B05B1/3402—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means designed to influence the nature of flow of the liquid or other fluent material, e.g. to produce swirl to avoid or to reduce turbulencies, e.g. comprising fluid flow straightening means

Definitions

• This invention relates to metal working operations such as turning, milling, facing, thread ⁇ ing, boring and grooving, and, more particularly, to a method and apparatus for performing such metal working operations at high speeds with improved chip control.
• a cutting tool which includes a tool holder and one or more cutting inserts each having a top surface termi ⁇ nating with one or more cutting edges.
• the tool holder is formed with a socket within which a cutting insert is clamped in place.
• the leading or cutting edge of an insert makes contact with the workpiece to remove material therefrom in the form of chips.
• a chip comprises a plurality of thin, generally rectan ⁇ gular-shaped sections of material which slide relative to one another along shear planes as they are sepa ⁇ rated by the insert from the workpiece.
• This shearing movement of the thin sections of material relative to one another in forming a chip generates a substantial amount of heat, which, when combined with the heat produced by engagement of the cutting edge of the insert with the workpiece, can amount to 1500°-2000°F, or higher.
• the causes of failure of the cutting inserts employed in prior art machining operations are abrasion between the cutting insert and workpiece, and a problem known as cratering. Cratering results from the intense heat developed in the formation of the chips and the frictional engagement of the chips with the cutting insert. As the material forming the chip is sheared from the workpiece, it moves along at least a portion of the exposed top surface of the insert.
• flood cooling One method commonly employed to cool the cutting area is known as flood cooling which involves the spraying of a low pressure stream of coolant toward the insert and workpiece.
• a nozzle disposed several inches above the :ting tool and workpiece directs a low pressure stream of coolant toward the workpiece, tool holder, cutting insert and on top of the chips being produced.
• the primary problem with flood cooling is that it is ineffective in actually reaching the cutting area.
• the underside of the chip which makes contact with the exposed top surface of the cutting insert, the cutting edge of the insert and the area where material is sheared from the workpiece, are not cooled by a low pressure stream of coolant directed from above the tool holder and onto the top surface of the chips. This is because the heat in such cutting area is so intense, i.e., on the order 2000°F or higher, that a heat barrier is produced which vapor ⁇ izes the coolant well before it can flow near the cutting edge of the insert.
• coolant in the form of an oil-water or synthetic mixture at ambient temperature, is directed onto the top surface of the insert toward the cutting area without sufficient velocity to pierce the heat barrier surrounding the cutting area.
• the coolant fails to reach the interface between the cutting insert and workpiece, and/or the area on the workpiece where the chips are being formed, before becoming vaporized.
• no heat is dissipated from the cutting area to prevent cratering.
• failure to remove heat from the cutting area creates a significant temperature differential between the cutting edge of the insert which remains hot, and the rear portion of the insert which is cooled by coolant, thus causing thermal failure of the insert.
• a failure to effectively reduce temperature in the cutting area results in a number of disadvan ⁇ tages and limitations in machining operations. As discussed above, high temperatures cause insert failure. This directly affects production speed in several ways. In order to reduce temperatures, the machine tools must be run at lower speeds, reduced depths of cut and reduced feed rates, each of which lowers productivity. If speeds are increased, the downtime of the machine tool increases because the inserts must be replaced more frequently. The less time the insert is in the cut, the lower the produc ⁇ tivity of a given machine tool. Overall productivity is therefore limited by the useful life and perfor ⁇ mance of the cutting inserts which have historically lagged far behind the operating speeds of machine tools.
• Chip breaker grooves extend inwardly from the exposed top surface of the insert, and are spaced from the cutting edge.
• the chip breaker groove engages chips as they are sheared by the cutting edge from the workpiece, and then turn or bend them upwardly from the exposed surface of the insert so that the chips tend to fracture.
• 4,621,547 discloses a tool holder in which the clamp or cap which secures the insert to the tool holder is formed with a coolant delivery passageway for directing coolant at high speed toward the cutting edge of the insert. Coolant is accelerated within the clamp or cap and is preferably discharged at a speed of greater than about 250 feet per second in an effort to pierce the heat barrier developed in the cutting area and flow beneath the chips being formed from the workpiece.
• the heat produced by shearing material from the workpiece is transferred from the workpiece to the mixed phase coolant stream, thus converting the ice particles within the stream from solid to vapor phase.
• the ice parti ⁇ cles undergo an explosive, volumetric expansion which produces a force capable of assisting in the shearing the material from the workpiece, and of breaking such sheared material into minute particles.
• a nozzle apparatus adapted for use with machine tools of different configuration, which perform different machining operations, comprising a nozzle body having a nozzle insert which is mounted within an outlet passageway formed in the nozzle body at its intersec- tion with a coaxial, larger diameter inlet passageway connected to a source of coolant, e.g., a water-oil mixture.
• the nozzle insert is constructed to acceler ⁇ ate the stream of coolant received from the inlet passageway, and to induce the formation of shock waves in the course of passage of the coolant stream through the interior of a nozzle body.
• a portion of the nozzle body of this invention is constructed in accordance with the teachings of my Patent No. 4,830,280, the disclosure of which is incorporated by reference in its entirety herein.
• the inlet passageway formed in the nozzle body is adapted to connect to a source of conventional water-oil coolant through a supply line and pump.
• the outlet passageway is formed with a smaller diameter than the inlet passageway, and is coaxial with and intersects the inlet passageway forming a shoulder at such intersection.
• a donut-shaped recess is formed in such shoulder, and this recess is concentrically disposed about the nozzle insert carried within the outlet passageway in the nozzle body.
• the nozzle insert is formed with a throughbore having a radially inwardly tapering throat portion beginning at an angled inlet end of the throughbore, ' and a minimum diameter portion at approximately the midpoint of the throughbore.
• the throat portion and minimum diameter portion collectively form an the inlet section of the nozzle insert and are disclosed in Patent No. 4,830,280.
• the nozzle insert of this invention is modified to include a radially outwardly tapering outlet portion which extends from the midpoint of the throughbore to its outlet end.
• the inlet section of the nozzle insert is effective to accelerate the coolant from the inlet passageway in the nozzle body through the reduced diameter portion of the insert with minimal losses due to drag or turbulence.
• a portion of the coolant stream which flows into the inlet passageway of the nozzle body is made to enter the donut-shaped recess. This portion of the coolant stream is rotated within the recess in the same direction as the flow of coolant through the nozzle body.
• the rotating portion of the coolant within the recess impacts the outer boundary of the main body of coolant and func ⁇ tions to both guide and accelerate it into the inlet portion of the throughbore in the nozzle insert.
• the combined effect of the rotating coolant within the recess, and the radially inwardly tapering inlet portion of the throughbore, is to eliminate much of the turbulence and drag which can occur as the coolant stream moves from the larger diameter inlet passageway into the smaller diameter outlet passage- way.
• the coolant stream is efficiently accelerated from the inlet passageway to the outlet passageway, and its actual velocity at the reduced diameter portion of the throughbore in the nozzle insert more nearly approaches the theoretical velocity which would be obtained absent any losses due to drag or turbulence.
• the coolant stream is accelerated to a velocity in the range of about 1000 to 1200 feet per second (fps) in the area of the reduced diameter portion or midpoint of the throughbore in the nozzle insert. It is theorized that such acceleration of the coolant stream produces a condition wherein a shock wave can be produced in the coolant stream in which at least some portion of the dissolved gases therein, i.e., nitrogen, oxygen, carbon dioxide, etc. , are caused to evolve or escape from the stream and form bubbles.
• a shock wave can be produced in the coolant stream in which at least some portion of the dissolved gases therein, i.e., nitrogen, oxygen, carbon dioxide, etc.
• An important aspect of this invention is that the formation of the shock wave within the coolant stream is induced and enhanced by the pro ⁇ vision of an expansion chamber defined by the radially outwardly tapering outlet portion of the throughbore in the nozzle insert, and a larger diameter discharge tube which is inserted within the outlet passageway of the nozzle body immediately downstream from the nozzle insert.
• This expansion chamber provides for volu ⁇ metric expansion of the coolant stream as the dissolved gases evolve or escape from solution, and thus allows the shock wave formed within the throughbore of the nozzle insert to propagate downstream.
• the wall in the nozzle insert formed by ⁇ the radially outwardly tapering portion of the throughbore therein is preferably oriented at an included angle of about 8° with respect to the longitudinal axis of the throughbore to permit the coolant stream to expand radially outwardly to a sufficient extent to avoid undue damping or choking of the shock wave developed within the nozzle insert.
• the coolant stream including bubbles is transmitted from the expansion chamber downstream through the discharge tube of the nozzle body.
• the discharge tube has a constant diameter from the nozzle insert to its discharge outlet where the outlet passageway in the nozzle body terminates. It is theorized that while gaseous bubbles are allowed to form immediately downstream from the reduced diameter section of the nozzle insert, i.e., within the expansion chamber, these bubbles will tend to dissolve back into the coolant stream in the course of movement through the remainder of the discharge tube. It is believed that this occurs because the discharge tube functions to confine further expansion of the bubbles soon after they are allowed to form, causing the bubbles to burst or collapse and re-enter the coolant stream.
• the energy and velocity of the coolant stream created by the second shock wave is utilized to assist in the machining operation, i.e., the coolant stream is directed onto the top surface of the insert toward its cutting edge and functions to both cool the cutting edge and workpiece, and to assist in the breakage of chips into relatively small lengths or particles as material is removed from the workpiece.
• the coolant stream or jet emitted from the discharge outlet of the nozzle body is directed at an angle of about 20° upon the top surface of the insert and is oriented to cover the entire width of the chip being sheared from the workpiece.
• an air jet passageway is formed in the nozzle body having a discharge outlet which is oriented to direct pressurized air to this area on the workpiece.
• a source of pressurized air i.e., shop air, is preferably directed into a manifold and then through a line connected to the air passageway within the nozzle body.
• a small quantity of liquified gas such as liquified nitrogen, is introduced into the manifold with the pressurized air to reduce the temperature of the pressurized air prior to introduction into the air passageway of the nozzle body.
• a controller such as any commercially available personal computer or the like, which also controls the supply of coolant into the inlet passageway of the nozzle body.
• Fig. 1 is a partial isometric view, exag ⁇ gerated for purposes of illustration, showing a tool holder and cutting insert for performing a turning operation, including the apparatus of this invention;
• Fig. 2 is a cross sectional view taken generally along line 2-2 of Fig. 1; and Fig. 3 is an enlarged cross sectional view of a portion of the nozzle body illustrated in Fig. 2.
• FIG. 1 one present- ly preferred embodiment of the nozzle apparatus 10 of this invention is illustrated for use with a turning holder 12 performing a turning operation on a work ⁇ piece 14.
• the workpiece 14 is mounted in a chuck of a machine tool (not shown) which is adapted to rotate the workpiece 14 in the direction indicated in Fig. 1.
• a turning holder 12 is illustrated in Fig. 1, it should be understood that the method and apparatus of this invention is applicable for use in other machin ⁇ ing operations such as milling, boring, cutting, grooving, threading, drilling and others, and the turning operation illustrated is shown solely for purposes of describing the present invention.
• the turning holder 12 comprises a support bar 16 formed with a seat adapted to receive a cutting insert 18 having an upper surface 20 terminating with a cutting edge 22.
• the cutting insert 18 is secured within the seat of the support bar 16 by a clamp 24 of conventional design.
• the nozzle apparatus 10 is mounted with respect to the upper surface 20 of insert 18 to direct a high energy, high velocity coolant stream towaong the cutting edge 22 of insert 18 and the workpiece 14, as described in detail below.
• the nozzle . apparatus 10 is preferably carried on the turret of the machine tool (not shown) by mounting structure which is designed specifically for a partic ⁇ ular machine. Such mounting structure forms no part of this invention per se and is therefore ⁇ not described herein.
• the nozzle apparatus 10 comprises a nozzle body 26 formed with an inlet passageway 28 connected by a line 30 to a pump 32 which communicates with a supply of coolant 34.
• the pump 32 is connected to a controller 35 such as a personal computer, microprocessor or other closed loop controller, which, as described below, is opera ⁇ tive to control the flow of coolant into inlet pas- sageway 28.
• controller 35 such as a personal computer, microprocessor or other closed loop controller, which, as described below, is opera ⁇ tive to control the flow of coolant into inlet pas- sageway 28.
• the term "coolant" as used herein is meant to refer to any one of a variety of commercially available liquid coolants employed in the machine tool industry which generally comprise a mixture of oil, water and other additives.
• the nozzle body 26 is also formed with an outlet passageway 36 which is coaxial with the inlet passageway 28.
• the outlet passageway 36 has a smaller diameter than the inlet passageway 28 forming a shoulder 38 where such passageways 28, 36 intersect.
• the nozzle body 26 is formed with an annular, donut-shaped recess 40 at the shoulder 38 formed by the intersection of the inlet and outlet passageways 28, 36.
• the recess 40 is formed with a generally U-shaped cross section, although it is contemplated that other cross sections could be employed for the purposes described below.
• the outlet passageway 36 of nozzle body 26 is formed with internal threads to mount a nozzle insert 42 and a discharge tube 44.
• the nozzle insert 42 has a cylin- drical-shaped, threaded outer surface 46 and an hourglass-shaped throughbore 48.
• the shape of the inlet portion of throughbore 48 is determined experi ⁇ mentally, and. in accordance with the teachings of my U.S. Patent No. 4,830,280, the disclosure of which is incorporated by reference in its entirety herein.
• the inlet portion of throughbore 48 includes a rounded inlet end 52 which extends at least partially into the outlet passageway 28, and a throat portion 54 which tapers radially inwardly from the inlet end 52 to a minimum diameter designated D located at about the midpoint 56 of the throughbore
• this radially inwardly tapering throat portion 54 is determined empirically by experi- mentation, but it can generally be characterized as a smoothly tapering polynomial curve extending between the inlet end 52 of throughbore 48 and the diameter D at the. midpoint 56 of throughbore 48.
• This inlet portion of the throughbore 48 in the nozzle insert 42 thus forms a venturi, for purposes described below. It is estimated that the axial distance between the inlet 52 and midpoint 56 of throughbore 48 is approxi-. ately three times the diameter D of the throughbore 48 at midpoint 56. See Fig. 3.
• the discharge portion of the hourglass- shaped throughbore 48 of the nozzle insert 42 i.e., downstream from the midpoint 56, is characterized by a radially outwardly tapering discharge portion 58 extending from the midpoint 56 to the outlet end 60 of the nozzle insert 42. It has been determined experi ⁇ mentally that the wall of the throughbore 48 formed by this discharge portion 58 should be tapered at included angle « of about 8° measured between a line 62 extending parallel to the longitudinal axis of the throughbore 48, and a line 63 which extends from the midpoint 56 and is substantially coincident with such wall of throughbore 48 formed along the discharge portion 58. See Fig. 3.
• the axial distance of the discharge portion 58 measured between the midpoint 56 and the outlet end 60 of nozzle insert 42 is pref ⁇ erably on the order of about three times the minimum diameter D of the throughbore 48.
• the discharge tube 44 is threaded into the outlet passageway 36 of nozzle body 26 downstream from the nozzle insert 42 and has an end 47 which abuts the outlet end 60 of nozzle insert 42.
• the discharge tube 44 is cylindrical in shape and has a constant diameter D-,.
• the diameter D tripod of discharge tube 44 can be obtained with the following formula:
• the discharge tube 44 has a discharge end 64 located flush with the terminal end of the outlet passageway 36 which defines a discharge outlet 65.
• the axial length of the discharge tube 44 is on the order of about twelve times the smallest diameter D of the throughbore 48 of nozzle insert 42.
• the nozzle body 26 is formed with an air passageway 66 connected by a line 68 to a cooling manifold 70. See Figs. 1 and 2.
• This cooling manifold 70 is connected to a source of pressurized air 72, e.g., shop air, and a tank 74 of liquified gas such as liquified nitrogen.
• the controller 35 is operatively connected to the liquified gas tank 74 and manifold 70 to control their operation as described below.
• An initial objective in the operation of the nozzle apparatus 10 is to reduce turbulence and drag in the flow of the coolant stream to and through the inlet portion of the nozzle insert 42 in nozzle body 26 in order to assist in obtaining maximum energy and velocity of the coolant stream 78 which is ultimately ejected from the discharge outlet 65 of tube 44 toward the cutting insert 18 and workpiece 14.
• the nozzle apparatus 10 of this invention employs the teachings of my U.S. Patent No. 4,830,280 to transmit coolant from the supply 34 through pump 32 and line 30 into the inlet passageway 28, and then through inlet portion of nozzle insert 42 within the nozzle body 26.
• a relatively low velocity stream of coolant 78 e.g., on the order of about 20 to 40 feet per second, is directed from pump 32 through line 30 into the inlet passageway 28 of the nozzle body 26.
• a portion 80 of this coolant stream 78 flows into the annular, U-shaped recess 40 which is concentric to the nozzle insert 42. It is believed that the coolant 80 entering the recess 40 is made to rotate in the direction of the arrow shown in Fig. 3, i.e., in the same direction as the flow of the main body of the coolant stream 78 through nozzle body 26.
• the portion 80 of the stream within recess 40 impacts the outer surface 82 of the coolant stream 78 and functions to guide and accelerate the main body of the coolant stream 78 into the smoothly angled, rounded inlet end 52 of the hourglass-shaped throughbore 48 in nozzle insert 42.
• the shape of the angled inlet end 52, and the radially inwardly tapering, throat portion 54 of throughbore 48 cooperate to smoothly receive the main body of the coolant stream 78 which lessens the turbulence in the transition area between the larger diameter inlet passageway 28 and the smaller diameter outlet passageway 36 in nozzle body 26. This produces minimal losses due to drag or turbulence and results in improved efficiency. Because the throat portion 54 of throughbore
• this inlet portion of the nozzle insert 42 functions as a venturi to substantially accelerate the velocity of the coolant stream 78 in the course of passage from the inlet passageway 28 of nozzle body 26 into the nozzle insert 42.
• the velocity of the coolant stream 78 increases from about 20 to 40 feet per second within the inlet passageway 28 to a velocity on the order of about 1000 to 1200 feet per second at or about the midpoint 56 of throughbore 48 having the minimum diameter D .
• this shock wave and the production of bubbles 84, is induced and enhanced by the configuration of the discharge portion 58 of throughbore 48 immediately downstream from the mid ⁇ point 56 of nozzle insert 42 having the minimum diameter Do. That is, it is believed that the radially outwardly tapering configuration of the discharge portion 58 of throughbore 48, in combination with the larger diameter discharge tube 44 immediately downstream therefrom, provides an expansion section or chamber 86 which allows for volumetric expansion of the coolant stream as the bubbles 84 are formed.
• the high velocity coolant stream including air bubbles 84 is directed at an angle ⁇ of about 20° with respect to the upper surface 20 of cutting insert 18, and is oriented such that the top portion 89 of the coolant stream 78 is aimed at the cutting edge 22 of insert 18 while the remaining portion of the coolant stream 78 flows along the upper surface 20 of insert 18.
• This has the effect of directing the coolant stream beneath the' chips 87 being sheared from the workpiece 14 to help break them into relatively small lengths or particles.
• the distance at which the discharge outlet 65 is spaced from the insert 18 is sufficient so that the width of the coolant stream 78 covers the entire width of the chips 87 being formed. Such spacing can be obtained during operation of apparatus 10 by visual observation, but is typically on the order of about one inch or more.
• a jet 92 of pressurized air is discharged from the air passageway 66 in nozzle body 26 onto the area 88 of the workpiece
• the temperature of the air jet 92 may be reduced by combining a liquified gas such as nitrogen gas with the pressurized air in the cooling manifold 70. This reduced temperature air jet 92 is then directed through the air passageway 66 onto the area 88. Such reduction in the temperature of the workpiece 14 at area 88 assists in the breakage of chips 87 therefrom, which is particularly useful for harder materials.
• a liquified gas such as nitrogen gas
• the introduction of liquified gas into the cooling manifold 70 is controlled by the controller 35 as desired. It is contemplated that for many types of materials, no liquified gas would be required. For harder materials, the liquified gas can be combined with the pressurized air as needed, e.g., in pulsed intervals, to reduce the temperature of the pressur ⁇ ized air jet 92 and thus reduce the temperature in the area 88 of the workpiece 14 to the extent desired. Additionally, the controller 35 is operative to control the flow of coolant entering the nozzle body 26 in accordance with the requirements of a particular application.
• the nozzle body 26 is illus- trated in the Figs, as including a separate nozzle insert 42 and discharge tube 44.
• a separate nozzle insert 42 and discharge tube 44 may be removed from the outlet passageway 36 in nozzle body 26, and replaced with other nozzle inserts 42 and/or discharge tubes 44 having different dimensions to accommodate varying operating parameters such as different pump sizes and different coolant flow rates which may be required for different types of materials or machining operations.
• the nozzle body 26 could be integrally formed with the structure provided by the separate nozzle insert 42 and discharge tube 44.
• the discharge tube 44 could be eliminated and replaced by a constant diameter bore in nozzle body 26, and the hourglass-shaped throughbore 48 in the nozzle insert 42 could be machined directly into the nozzle body 26 using conventional machining techniques.
• a nozzle body 26 of this construction therefore, is considered to be within the scope of this invention.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Auxiliary Devices For Machine Tools (AREA)

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• 1991
  • 1991-08-27 WO PCT/US1991/006114 patent/WO1992004151A1/en not_active Application Discontinuation
  • 1991-08-27 JP JP3517812A patent/JPH06500959A/ja active Pending
  • 1991-08-27 EP EP19910918777 patent/EP0546117A4/en not_active Withdrawn
  • 1991-08-27 AU AU87663/91A patent/AU8766391A/en not_active Abandoned
  • 1991-08-27 CA CA002089065A patent/CA2089065A1/en not_active Abandoned

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