GB2501511A

GB2501511A - Cutting tool with internal mql supply

Info

Publication number: GB2501511A
Application number: GB1207265.8A
Authority: GB
Inventors: Wei-Ming Sim; David Gaudillere
Original assignee: Airbus Operations SAS; Airbus Operations Ltd
Current assignee: Airbus Operations SAS; Airbus Operations Ltd
Priority date: 2012-04-26
Filing date: 2012-04-26
Publication date: 2013-10-30
Also published as: GB201207265D0

Abstract

A cutting tool (1) comprising a body (2) configured for attachment to a tool holder and defining a cutting zone having at least one cutting edge (6), wherein the body includes at least one first passage (12) for delivering a supply of oil, and at least one second passage (7) for delivering a supply of compressed gas, the first and second passages being adapted to be fluidly connected to respective oil and compressed gas supplies (13, 8) external to the cutting tool, and wherein the first passage and the second passage meet at a mixing chamber (15) adjacent an exit (11) in the cutting zone such that the oil and compressed gas, in use, form an atomised oil mist which is ejected from the exit for minimum quantity lubrication (MQL) or near-dry machining (NDM) operations. The cutting tool may be an end mill. Also, a machine tool with the cutting tool, and a method of machining, whereby oil and compressed gas are supplied separately to the cutting tool where they are mixed adjacent to an exit to the cutting zone before being ejected from said exit.

Description

CUTTING TOOL

FIELD OF THE INVENTION

The present invention relates to a cutting tool for minimum quantity lubrication (MQL) or near-dry machining (NDM) operations, a machine tool with the cutting tool, and to a method of machining.

BACKGROUND OF THE INVENTION

Machining of metallic materials is commonly performed using a machine tool including a cutting tool. Various machine tools are known for performing machining opcrations including turning, milling, drilling, boring, reaming, threading, ctc. The cutting tool is normally held in the machine tool by a tool holder on the end of a spindle. Cutting tools can operate in one, two or three dimensions, and in single or multiple axes.

Thc cutting tool has a cutting zone including at Icast onc cutting cdgc. Cooling thc cutting edge is important, particularly for machining some metallic materials such as titanium alloys where the cutting temperature may be as high as 850 degrees Celsius.

Various cooling strategies have been devised by machine and cutting tool manufacturcrs to cool the cutting edge to minimise tool wear, increase productivity and reduce costs. These cooling strategies include high pressure coolant, liquid nitrogen, or oil mist delivery to the cutting edge.

Using an atomised oil mist is more commonly known as minimum quantity lubrication (MQL) or near-dry machining (NDM). MQL has as its aim to supply only the minimal quantity of lubricant required to minimise friction from building up at the cutting edge of the tool. This improves and lengthens the life of the tool, increases productivity by reducing the number of machined parts that require reworking, reduces mess and subsequent clean-up and disposal compared with wet lubricants, significantly reduces airborne lubricant particles so improving heath relevant environmental impacts and further minimising mess. MQL also produces dry workpieces as well as dry chips, which provides cost savings since it is no longer necessary to clean the workpiece or chip. High-performance MQL systems can generate an oil mist with droplet diameters of less than one micron, and with amounts of lubricant less than approximately 50 mI/h, depending upon the machining method, machine tool and workpiece material.

Delivery of the atomised oil mist to the cutting zone is achieved by various means, falling into two general categories -internal and external MQL delivery. External MQL delivery typically uses a nozzle on a snake arm with the nozzle exit disposed near the cutting zone. The MQL nozzle is configured with an oil supply through a central tube under compressed air flow. An oil mist is created when the compressed air contacts the oil supply. The compressed air breaks the oil first into ligaments then forms droplets at a later stage. The droplets are eharacterised by droplet distribution, diameter and velocity. The oil mist is therefore created in the nozzle and by appropriately positioning and orienting the nozzle, the oil mist is directed towards the cutting zone. External MQL delivery suffers the drawback that positioning the nozzle is difficult to ensure effectively delivery of the oil mist.

More recently, internal MQL delivery has been proposed in which the oil mist is created in a mixing chamber and the oil mist must travel through the spindle, tool holder and the cutting tool to reach an exit adjacent the cutting edge. However, the length of the path along which the oil mist must travel significantly degrades the effectiveness of the oil mist due to turbulence and adhesion to surface walls of the path and navigating tight corners. These losses negatively affect the quality of the oil mist exiting the cutting tool in the cuffing zone.

W02009/135660 describes a machine tool in which an oil channel and an air path meet at a mixing chamber within a tool holder. An oil mist is created in the mixing chamber, which is discharged into the tool having channels for delivery of the oil mist to the cutting zone at the distal end of the tool.

SUMMARY OF THE INVENTION

A first aspect of the invention provides a cutting tool comprising a body configured for attachment to a tool holder and defining a cuffing zone having at least one cuffing edge, wherein the body includes at least one first passage for delivering a supply of oil, and at least one second passage lbr delivering a supply of compressed gas, the first and second passages being adapted to be fluidically connected to respective oil and compressed gas supplies external to the cutting tool, and wherein the first passage and thesecondpassagemeetadjacentanexitinthecuttingzonesuchthattheoiland compressed gas, in use, lbrm an atomised oil mist which is ejected from the exit for minimum quantity lubrication (MQL) ornear-dryniachining (NDM) operations.

A further aspect of the invention provides a machine tool including the cutting tool of the invention.

A further aspect of the invention provides a method fbr minimum quantity lubrication (MQL) or near-dry machining (NDM) operations, comprising providing separate supplies of oil and compressed gas to a cutting tool having a cutting zone with at least one cutting edge, and mixing the oil and the compressed gas within the cutting tool adjacent an exit in the cutting zone such that the oil and compressed gas %rm an atomised oil mist which is ejected from the exit.

The invention is advantageous in that the atomised oil mist can be formed within the cutting tool immediately adjacent the cutting zone such that the atomised oil mist can travel a short, substantially uninterrupted distance to the cuffing edge. This contrasts with the prior art solutions where the oil mist is required to navigate a long and/or winding path with obstructions that degrades the quality of the oil mist, leading to sub-optimal MQL or NDM machining.

The cutting tool body may include a plurality of the first and/or second passages. In particular, a plurality of thc passagcs may be provided whcrc thc tool includes a plurality of cuffing cdgcs. Rcspcctivc ones of thc first and sceond passagcs may mcct adjacent respective exits in the cutting zone. The exits may be disposed adjacent rcspcctivc cutting edges.

One or more of thc first and/or second passages may be arc branched. This may bc particularly advantageous whcrc thc tool includcs a plurality of cutting cdgcs, each with respective fluid passages, where the branches make it possible to minimize the number of discrete fluid entry points into the tool.

The body may include a central inlet fluidically connected to a plurality of the first passages. The first passages may each extend substantially linearly. Alternatively they may be kinked or winding, as desired. Linear passages may be preferred so as to reduce fluid flow losses, but linear passages may not be convenient to package within some tool designs.

The body may include a plurality of inlet ports fluidically connected to a plurality of the second passages.

The first and second passages may be arranged to meet at a shallow angle, e.g. of less than 30 degrees. Preferably, this angle is less than 15 degrees.

The trajectory of the atomised oil mist from the exit(s) may be directed uninterrupted towards an adjacent respective cutting edge.

The cutting tool may be adapted for machining operations including turning, milling, drilling, boring, reaming and threading, or others as will be appreciated by those skilled in the art. The cutting tool may be an end mill, or a boring/turning tool for

example.

The machine tool may include a spindle coupled to a tool holder for holding the cutting tool.

The machine tool may include means external to the cutting tool for supplying oil and a compressed gas, separately. For example, the machine tool may include a supply of oil external to the cutting tool and fluidieally coupled to the first passage(s) within the tool, and a supply of compressed gas external to the cutting tool and Iluidically coupled to the second passage(s) within the tool. The maching tool may further include an actuator, a frequency generator and a liquid flow adjuster for feeding an amount of oil from the supply to the cutting tool.

The machining method may further include the steps of metering the flows of compressed gas and oil delivered to the cutting tool.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a side view of an end mill in accordance with a first embodiment of thc invcntion; Fiurc 2 illustratcs a cross scction vicw of thc cnd mill of Figurc 1; Figure 3 illustrates a schematic plan view of the end mill of Figure 1; Figure 4 illustrates a side view of a drill in accordance with a second embodiment of the invention; Figure 5 illustrates a side view of another end mill in accordance with a third embodiment of the invention; Figure 6 illustrates a side view of a turning/boring tool in accordance with a fourth embodiment of the invention Figure 7 illustrates schematically a machine tool including the end mill of Figure 1 coupled to a spindle via a tool holder, and an external source for delivering separate supplies of compressed air and oil to the end mill.

DETAILED DESCRIPTION OF EMBODIMENT(S)

Figure 1 illustrates an end mill 1 for attachment to a spindle 20 of a machine tool via a tool holder 30 (shown in Figure 7) for use in machining metallic materials, including in particular, though not exclusively, aluminium and/or titanium alloys. The end mill 1 includes a body 2 having a proximal end 3 for attachment to the tool holder 30 and a distal end defining a cutting zone 4 (a "pocket") having a plurality of replaceable cutting teeth S each defining a respective cutting edge 6.

In the example depicted in Figure 1, the end mill 1 is a shell end mill including four cutting teeth 5. However, it will be appreciated that the detailed design of the end mill 1 and the number of cutting teeth 5 may be varied according to detailed design considerations, and in particular the number of cutting teeth may be any number including I. The cutting teeth may be fixed or replaceable, and may take a variety of shapes.

As with a conventional end mill, the body 2 of the end mill I includes a plurality of fluid passages 7 (for liquid andlor gas) fluidically coupled to a supply 8 from thc spindle 20 of the machine tool. The spindle typically has a central aperture for delivering a fluid to the end mill via the tool holder 30. In a conventional end mill, these fluid passages 7 may be used for delivery of flood coolant, or liquid nitrogen to the cutting zone 4. The fluid passages 7 are typically formed by micro drilling or electrical discharge machining (EDM).

Each fluid passage 7 has an inlet opening 9 disposed within a recess 10 formed in the proximal end 3 of the body 2. Each of the fluid passages 7 has an exit aperture 11 disposed immediately adjacent a respective one of the cutting teeth 5. As best shown in Figures 2 and 3, the fluid passages 7 are generally linear and extend from the leading end towards the distal end of the body 2 of the end mill 1 along an axis slightly inclined with respect to the axis of the spindle. However, it will be appreciated that the fluid passages 7 need not be strictly linear and may be kinked, for example, as influenced by factors such as the tool geometry.

The fluid passages 7 are therefore similar to those provided in a conventional end mill known in the prior art. However, in this embodiment the fluid passages 7 are arranged to supply compressed air, or other compressed gas, that is delivered to the end mill I via the spindle 20. As best shown in Figure 3, the compressed gas supplied from the spindle 20 into the recess 10 in the proximal end 3 of the body 2 is turned from a direction substantially parallel with the longitudinal axis of the spindle to flow generally radially outwardly across the recess 10 and then into the inlets 9 of the respective fluid passages 7. This arrangement promotes a generally uniform flow of the compressed gas through each of the fluid passages 7.

Unlike the conventional end mill, the end mill 1 has, in addition to the fir st set of fluid passages 7, a second set of fluid passages 12. The fluid passages 12 include entry holes 13 in the proximal end 3 of the end mill 1. Tn this particular embodiment, two entry holes 13 are provided, although it will be appreciated that any number of entry holes 13 may be provided including one. Each of the fluid passages 12 is associated with a respective one of the fluid passages 7 and are arranged such that each fluid passagc 12 opcns in to a rcspcctivc fluid passagc 7 adjaccnt thc cxit 11.

As bcst shown in Figurc 2, thc fluid passagcs 12 arc gcncrally linear and approach their respective fluid passage 7 at a shallow angle, e.g. less than approximately 30 dcgrccs, and prcfcrably lcss than 15 dcgrccs. Thc fluid passagcs 12 havc a smallcr borc diamctcr than thc fluid passagcs 7 and arc typically crcatcd in thc body 2 by a similar method such as micro drilling or EDM.

The fluid passages 12 are arranged to deliver a supply of neat oil lubricant from a source external to the machine tool via channels formed in the spindle 20 and tool holder 30 to the entrance holes 13. Since in this embodiment the number of entrance ho Ics 13 is fcwcr than thc numbcr of cutting tccth 5 thc fluid passagcs 12 arc branchcd at junctions 14.

The end of the fluid passage 7 nearest the exit 11 downstream of the opening with the fluid passage 12 therefore defines a mixing chamber 15. When the neat oil lubricant is fcd through thc fluid passagc 12 into thc flow of comprcsscd air in thc fluid passagc 7 the compressed air breaks the oil first into ligaments and then into droplets within the mixing chamber 15 so as to create an atomised oil mist which is ejected from the exit 11 directly towards the cutting edge 6 in the cutting zone 4. The action of forming the atomised oil mist is analogous to the mixing which occurs in a conventional cxtcrnal MQL nozzle. By varying thc flow ratc and prcssurc of thc compressed air and oil in the fluid passages 7, 12 respectively the oil mist parameters can be varied. These parameters may include, for example, the mean oil droplet size, velocity, distribution etc. Thc dcsign of thc mixing chambcr can bc changcd according to requirements. For example, it may be desirable that the mixing chamber 15 has a larger diameter than that of the remainder of the fluid passage 7. This would entail varying the diameter of the fluid passage 7 along its length. A larger mixing chamber may be more efficient.

Altcrnativcly, it may bc dcsirablc that thc mixing chambcr has a smaller diameter than fluid passage 7. These and other modifications will be appreciated by those skilled in the art.

Referring to Figure 2, the end mill I includes a fastener 16 for securing the end mill to thc tool holdcr 30. Whcn thc cnd mill 1 is sccurcd on thc tool holder thc fastcncr acts to block the open end of the end mill I so as to direct the compressed air flow 8 towards thc opcnings 9.

Figure 7 illustrates the end mill I coupled to the spindle 20 via the tool holder 30 and showing thc fluid supply connections to the end mill 1. An external supply 40 includes a pneumatic supply 41 for delivering a supply of compressed air 42 and a hydraulic supply 43 for delivering a supply of neat oil 44. The separate oil and compressed air supplies 42, 44 are coupled to the spindle 20 which includes a central passagc 21 for delivering the supply 8 of compressed air to the end mill 1. In addition, the spindle 20 includes one or more passages 22 for delivering the supply of oil 44 to the inlet openings 13 in the end mill 1.

The tool holder 30 couples the end mill 1 to the spindle 20 and as such includes corresponding passages for delivering the separate supplies ofoil and compressed air to the end mill 1. The central fluid passage 21 through the spindle 20 and the tool holder 30 may be of a conventional type used, for example, to deliver flood coolant to a conventional end mill. The additional fluid passage(s) 22 for delivering the separate supply of oil is a departure from this conventional arrangement. The respective hydraulic and pneumatic systems 41, 43 include a frequency generator and a liquid flow adjuster for supplying a metered amount of oil and compressed air to the cutting tool to achieve a desired atomised mist in the cutting zone.

Whilst in the embodiment described above the invention is described in relation to a shell end mill 1, it will be appreciated by those skilled in the art that the same principles may be applied to other cutting tools, such as drills, end mills and turning/boring tools. Figures 4 to 6 illustrate how the principles of the invention may be applied to some of these ahernative types of cutting tools and will be briefly discussed below. The detailed features of these various cutting tools that are commonly known in the art will not be repeated here so as not to obscure the clarity of the teaching of the invention.

Figure 4 illustrates a drill tool 51 having a cutting zone 52 at its distal end including at least one cutting edge, and is configured for attacbmcnt to a tool holder by its proximal end 53. The drill includes a central bore 54 through which a supply of comprcssed air 55 is delivercd through the centrc of thc tool to thc cutting zonc 52.

Onc or morc separate fluid passagcs 56 are also provided through the body of thc drill 51 for delivering a supply of oil to the distal end of the tool.

The oil and the compressed air are kept separated until they become mixed at the distal end of the tool where an atomised oil mist is formed immediately adjacent the cutting edge. The drill 51 may be coupled to a spindle in a machine tool via a tool holder, for example, in a conventional manner with appropriate adaptations, where necessary, for the supply of oil and compressed air in separate streams to the drill tool 51. Means for supplying the oil and compressed air may be similar to that described above with refereilce to Figure 7.

Figure 5 illustrates an end mill 61 which includes a cutting zone 62 having at least one cutting edge at its distal end and a body configured for attachment to a tool holder at its proximal end 63. The end mill 61 includes a first passage 64 for delivering a supply of compressed air via a plurality of branches 64a, 64b, 64c to each respective cutting edge in the cutting zone 62. One or more second passages 65 deliver a supply of neat oil so as to mix with the comprcssed gas adjacent an exit in the cutting zone such that the oil and compressed gas form an atomised oil mist which is ejected from the exit towards the respective cutting edges. The arrangement of the end mill 61 is similar in many respects to the shell end mill described with reference to Figures Ito 3.

In a yet ffirther embodiment, the end mill may bc a solid carbide end mill for high value items. The design of the end mill may be gellerally similar to that shown in Figure 5 but with a fixed grinding edge rather than replaceable cutting edges. A fixed grinding edge may be used instead of a replaceable cutting edge in any cutting tool of the invention.

Figure 6 illustrates a turning or boring tool 71 including a cutting zone 72 including a cutting edge 73 and a body 74 configured lbr attachment to a tool holder by its proximal end 75. The boring tool 71 includes a first passage 76!br delivering a supply of compressed gas and a separate second passage 77 fbr delivering a supply of neat oil. The oil and compressed gas meet first at a mixing chamber 78 adjacent the cutting edge 73. The oil and compressed gas form an atomised oil mist which is ectedfromanexit79immediatelyadjacentthecuthngedge73soastoejectthe atomised oil mist towards the cutting edge fix MQL or NDM operations.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

Claims 1. A cutting tool conqtising a body configured for attachment to a tool holder and defining a cutting zone having at least one cutting edge, wherein the body includes at least one first passage for delivering a supply of oil, and at least one second passage fbr delivering a supply of compressed gas, the first and second passages being adapted to be fluidically connected to respective oil and compresscd gas supplies cxtcrnal to the cutting tool, and whcrcin the first passage and the second passage meet adjacent an exit in the cutting zone such that the oil and compressed gas, in use, fbrm an atomised oil mist which is ejected from the exit lbr minimum quantity lubrication (MQL) or near-dry machining (NDM) operations.
2. A cutting tool according to claim 1, wherein the body includes a plurality of the first and/or second passages.
3. A cutting tool according to claim 1 or 2, wherein respective ones of the first and second passages meet adjacent respective exits in the cutting zone.
4. A cutting tool according to claim 3, wherein the exits are disposed adjacent respective cutting edges.
5. A cutting tool according to any preceding claim, wherein one or more of the first and/or second passages are branched.
6. A cutting tool according to any preceding claim, wherein the body includes a central inlet fluidically connected to a plurality of the first passages.
7. A cutting tool according to claim 6, wherein the first passages each cxtcnd substantially linearly.
8. A cutting tool according to any preceding claim, wherein the body includes a plurality of inlet ports fluidically eonncctcd to a plurality of thc second passages.
9. A cutting tool according to any preceding claim, wherein the first and second passages are arranged to meet at an angle of less than 30 degrees.
10. A cutting tool according to any preceding claim, wherein the trajectory of the atomised oil mist from thc exit(s) is directed uninterrupted towards an adjacent respective cutting edge.
II. A cutting tool according to any preceding claim, wherein the cutting tool is adapted for machining operations selected from the group comprising: turning, milling, drilling, boring, reaming and threading.
12. A cutting tool according to any preceding claim, wherein the cutting tool is an end mill.
13. A machine tool comprising a spindle, a tool holder and a cutting tool according to any preceding claim.
14. A machine tool according to claim 13, further comprising a supply of oil external to the cutting tool and fluidically coupled to the first passage(s) within the tool, and a supply of compressed gas external to the cutting tool and fluidically coupled to the second passage(s) within the tool.
15. A machine tool according to claim 14, further comprising an actuator, a frequency generator and a liquid flow adjuster for feeding an amount of oil from the supply to the cutting tool.
16. A method for minimum quantity lubrication (MQL) or near-dry machining (NDM) operations, comprising providing scparatc supplics of oil and compressed gas to a cutting tool having a cutting zone with at least one cutting edge, and mixing the oil and the compressed gas within the cutting tool adjacent an exit in the cutting zone such that the oil and compressed gas form an atomised oil mist which is ejected from the exit.
17. A method according to claim 16, further comprising metering the flows of compressed gas and oil delivered to the cutting tool.
18. A method according to claim 16 or 17, wherein the trajectory of the atomised oil mist from the exit is directed uninterrupted towards an adjacent respective cutting edge.
19. A method according to any of claims 16 to 18, whcrein the oil and compressed gas are delivered to the cuffing tool via a spindle and tool holder arrangement used to hold the cutting tool.