GB2184381A - Machine tools - Google Patents

Machine tools Download PDF

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Publication number
GB2184381A
GB2184381A GB08700631A GB8700631A GB2184381A GB 2184381 A GB2184381 A GB 2184381A GB 08700631 A GB08700631 A GB 08700631A GB 8700631 A GB8700631 A GB 8700631A GB 2184381 A GB2184381 A GB 2184381A
Authority
GB
United Kingdom
Prior art keywords
tool
permanent magnet
magnet member
machine tool
movable permanent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08700631A
Other versions
GB2184381B (en
GB8700631D0 (en
Inventor
Roger Harvey Slee
Peter Thomas Booth
Christopher Paul Compton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AE PLC
Original Assignee
AE PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB838316428A external-priority patent/GB8316428D0/en
Priority claimed from GB838325295A external-priority patent/GB8325295D0/en
Application filed by AE PLC filed Critical AE PLC
Priority claimed from GB08415331A external-priority patent/GB2142860B/en
Publication of GB8700631D0 publication Critical patent/GB8700631D0/en
Publication of GB2184381A publication Critical patent/GB2184381A/en
Application granted granted Critical
Publication of GB2184381B publication Critical patent/GB2184381B/en
Expired legal-status Critical Current

Links

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
    • B23Q15/00—Automatic control or regulation of feed movement, cutting velocity or position of tool or work
    • B23Q15/007—Automatic control or regulation of feed movement, cutting velocity or position of tool or work while the tool acts upon the workpiece
    • B23Q15/013—Control or regulation of feed movement
    • B23Q15/02—Control or regulation of feed movement according to the instantaneous size and the required size of the workpiece acted upon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B29/00—Holders for non-rotary cutting tools; Boring bars or boring heads; Accessories for tool holders
    • B23B29/04—Tool holders for a single cutting tool
    • B23B29/12—Special arrangements on tool holders
    • B23B29/125—Vibratory toolholders
    • 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
    • B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
    • B23Q1/25—Movable or adjustable work or tool supports
    • B23Q1/26—Movable or adjustable work or tool supports characterised by constructional features relating to the co-operation of relatively movable members; Means for preventing relative movement of such members
    • B23Q1/34—Relative movement obtained by use of deformable elements, e.g. piezoelectric, magnetostrictive, elastic or thermally-dilatable elements
    • 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
    • B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
    • B23Q1/25—Movable or adjustable work or tool supports
    • B23Q1/26—Movable or adjustable work or tool supports characterised by constructional features relating to the co-operation of relatively movable members; Means for preventing relative movement of such members
    • B23Q1/34—Relative movement obtained by use of deformable elements, e.g. piezoelectric, magnetostrictive, elastic or thermally-dilatable elements
    • B23Q1/36—Springs
    • 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
    • B23Q5/00—Driving or feeding mechanisms; Control arrangements therefor
    • B23Q5/22—Feeding members carrying tools or work
    • B23Q5/28—Electric drives
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/182—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by the machine tool function, e.g. thread cutting, cam making, tool direction control
    • G05B19/184—Generation of cam-like surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B2260/00—Details of constructional elements
    • B23B2260/108—Piezoelectric elements
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/41—Servomotor, servo controller till figures
    • G05B2219/41352—Alternative clamping dilation of piezo, caterpillar motion, inchworm
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/41—Servomotor, servo controller till figures
    • G05B2219/41354—Magnetic, thermal, bimetal peltier effect displacement, positioning
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/50—Machine tool, machine tool null till machine tool work handling
    • G05B2219/50053—Machine non circular, non-round cross section, hexagonal, rectangular

Abstract

In the machine tool, the tool 31 is moved using a signal representing a required profile of the surface being machined. This signal is fed to a D.C. linear motor, which converts the signal into a corresponding linear movement which is transmitted to the tool 31 supported in the movable permanent magnet 28 of the motor. Such machine tools can be used for producing workpieces which are non-circular in cross- section and/or which are barrelled or tapered along their length. The motor has positioning means for applying to the magnet 28 a restoring to datum position force, the means incorporating diaphragms connected to the magnet. <IMAGE>

Description

SPECIFICATION Machine tools The invention relates to machine tools for machining workpieces and in particular to machine tools for machining workpieces to have a non-cylindrical surface profile with relative rotation between a tool and the workpiece about a workpiece axis.
In a conventional machine tool, a tool is mounted on a tool holder which is carried on a slide moved by an electric motor via a lead screw. Such machine tools are capable of applying a wide range of cutting forces to a wide variety of workpieces.
It is a disadvantage of such conventional machine tools, however, that the inertia of the slide and the construction of the transmission by which the drive is transmitted from the motor to the slide limits severely the speed at which a rotating workpiece can be machined when the position of the tool has to be altered during machining. This is because, as the rotational speed of the workpiece is increased and/or as the speed of tool movement is increased, there is a speed at which the slide cannot react sufficiently quickly to positioning signals, so that the tool is not in a required position at a required time and so that the required profile is not machined. This is particularly true when the tool position is to be altered incrementally within a revolution of the relative rotation or between revolutions.
According to the invention, there is provided a machine tool for machining a workpiece to a non-uniform surface profile which requires machining movements of the tool within a revolution of relative rotation therebetween, and comprising a control system for producing from data supplied thereto, an electrical output signal which is a function of the required nonuniform surface profile of the workpiece being machined, a D.C. linear motor connected to the control system and in which the linear position of a movable permanent magnet member is determined by a magnetic field produced in stator coils of the linear motor by the electrical output signal from the control system, the movable permanent magnet member being connected to the tool to move the tool in accordance with said output signal, the tool and the workpiece being relatively rotatable about a workpiece axis.
Further novel features and/or combination of features of the invention will become apparent from the following description, given by way of example, of some embodiments of the machine tool, reference being made to the accompanying drawings in which: Figure 1 is a schematic diagram of a machine tool for machining workpieces to complex out-of-round shapes, Figure 2 is a perspective view of a first form of transducer for use with the machine tool of Fig. 1, the transducer being in the form of a D.C. linear motor, Figure 3 is a section of a tool positioning device suitable for use with the transducer of Fig. 2, and Figure 4 is a perspective view of a second form of D.C. linear motor for use as a transducer in the machine tool of Fig. 1.
Referring first to Fig. 1, the machine tool comprises a control system 12. A tool holder 14 carries a tool 15 for machining a rotating workpiece 16 rotated by a drive. The tool holder 14 is connected to a drive which moves the holder 14 in an axial direction along the workpiece 16 at a predetermined constant speed.
It will be appreciated, however, that the workpiece 16 could be stationary during machining and the tool 15 rotated around the workpiece 16 on a rotating head.
An angular sensor 17 produces a signal proportional to the angular position of the workpiece 16 during revolution and an axial sensor 19 produces a signal proportional to the axial position of the tool holder along the axis of rotation of the workpiece 16. These signals are provided as feedback to the control system 12.
The control system 12 is fed, from an input device, with data relating to a required profile of the surface of the workpiece 16. The control system produces a continuous electrical output signal whose amplitude is porportional to a required radius of the workpiece at a required time (i.e. at a required axial position along the workpiece). In the production of this signal, account is taken of the feedback signals from the sensors 17 and 18. The variable output signal is applied direct to a transducer 20 which produces a linear movement in accordance with the output signal. This movement is transmitted to the tool 15 to cause the tool 15 to move in accordance with the output signal. Accordingly, the profile of the workpiece will be machined in accordance with the profile signal.
It will be appreciated that the control system 12 may produce a signal whose amplitude varies within a revolution of the workpiece and/or whose amplitude varies between successive axial positions of the tool. Where there is variation of amplitude within a revolution, this may be a symmetrical variation in each half cycle or different variations in each half cycle or, indeed, in each quarter cycle or any other required variation. In this way, a machined workpiece, such as a piston or a bearing or a piston ring for an internal combustion engine, may be produced which is eiliptical in cross-section or part-circular or partelliptical in cross-section or any other required cross-sectional profile and which is additionally or alternatively barrelled or tapered or both along its axial length.
In addition, it is possible for the tool to machine a surface lying in a plane generally normal to the axis of rotation of the workpiece to provide a profile on said surface in which each point on said surface is a required axial distance from a reference plane.
The tool holder can be made to have very low weight and inertia and is very closely coupled to the transducer 20. In view of this, it is possible to revolve the workpiece at high speed, for example up to or above 3,000 revolutions per minute while effecting a number of accurate changes of the radial position of the tool accurately within a revolution. For example, the tool may move up to 10,000 Hz with a maximum movement of 0.1 mum. This allows exceptionally high production rates to be achieved while maintaining dimensional accuracy Referring first to Fig. 2, there is shown a first form of the transducer 20 as a D.C. linear motor comprising a generally U-shaped fixed core 25 with the limbs of the U being of part-cylindrical shape about a common axis.
Stator coils 26 are wound on each of these limbs. A rod-like movable permanent magnet 28 is arranged between, and co-axially with, the part-cylindrical U-shaped limbs. An extension 29 of this rod-like member 28 is carried in a bearing, which may be formed by a pair of diaphragms 30 or may be a magnetic bearing or an air bearing. A tool 31 is carried at the end of the rod extension 29 remote from the stator coils 26.
This D.C. linear motor assembly is contained with a casing 32 which is carried on a tool slide 33 movable through a lead screw 34 and a motor (not shown). The D.C. linear motor is mounted so that the movable rod-like permanent magnet 28 extends in a direction normal to the axis of rotation 34 of a workpiece 35, here shown as a piston for an internal combustion engine. The slide 33 is arranged to be movable in a direction parallel to the axis of rotation 34 of the workpiece.
In use, the stator coils are connected to the control system shown in Fig. 1 with feedback being provided by sensors of the kind shown in Fig. 1. The workpiece 35 is rotated and the lead screw 34 rotated to move the tool 31 at a constant speed in an axial direction along the surface of the workpiece 35. The signals fed from the control system to the stator coils 26 cause the rod-like permanent magnet member 28 to move in the bearing to a position corresponding to the applied signal, so that the tool 31 is moved to an instantaneous required radial position to machine a required profile on the'workpiece.
The low inertia, high acceleration and high force of such a D.C. linear motor allow it to machine workpieces at high speed, with the tool position changing many times with a revolution of the workpiece.
The diaphragms 30 provide a tool positioning device which tends to return the tool 31 to a datum position in the absence of a positioning signal. One form of such a device is shown in more detail in Fig. 3. The device comprises a cylindrical housing 45 provided with end clamps 46 which clamp the outer peripheries of respective steel diaphragms 30, so that the diaphragms 30 lie in respective planes normal to the housing axis. A tool holder in the form of an elongate rod 47 is connected to the diaphragm 30 and is arranged with its axis 48 co-axial with the axis of the housing 45. One end of the tool holder 47 is provided with a tool mounting 49 while the other end of the tool holder may be connected to the movable permanent magnet member 28.
Alternatively, a linear motor may be provided within the housing 45 between the diaphragms 30. This comprises a stator 50 fixed to the housing and a slider 51 carried on the tool holder 47.
There may be more than two diaphragms 30; three, four or more diaphragms may be provided.
It will be appreciated that none of the tool forces, which may vary from 5 to 25 kg, are taken by the linear motor; all these forces are taken by the diphragms 30. This means that the linear motor does not have to be sufficiently large to damp out unwanted oscillations of the tool holder 47 during its movement; these are dealt with by the diaphragms 30.
Thus the inertia of the permanent magnet member 28 or the slider 51 can be kept to a minimum; so increasing the speed of the response.
In addition, it will be appreciated that since the force moving the tool holder 47 is applied magnetically, there are no frictional forces between the tool holder 47 and its drive which would tend to slow the response time of the tool actuator.
An alternative form of linear motor transducer is shown in Fig. 4. In this embodiment, a D.C. linear motor comprises a generally Ushaped fixed core 36 with stator coils 37 wound on each limb of the U. A flat permanent magnetic moving member 38 extends between the limbs of the U-shaped core and through the base of the U. This member 38 is supported at each of its ends by a plurality of flexible plates 39 carried on a base 40 and lying in planes normal to the length of the member 38, so that the member 38 has limited movement in the direction of its length and is subject to a restoring force from the plates 39 which tends to return the member 38 to a datum position. A tool holder 41 is mounted at one end of the permanent magnet member 38 and holds a tool 42. A flexible cover 43 extends around and over the linear motor to shield it from dust and metal chips.
In use, the D.C. linear motor of Fig. 4 is mounted on a slide in the same way as the linear motor of Fig. 2. The stator coils 37 are connected to the control system of Fig. 1 and the tool is controlled to machine a workpiece (not shown) in the same way as the tool of the embodiment of Fig. 2.

Claims (9)

1. A machine tool for machining a workpiece to a non-uniform surface profile which requires machining movements of the tool within a revolution of relative rotation therebetween, and comprising a control system for producing from data supplied thereto, an electrical output signal which is a function of the required non-uniform surface profile of the workpiece being machined, a D.C. linear motor connected to the control system and in which the linear position of a movable permanent magnet member is determined by a magnetic field produced in stator coils of the linear motor by the electrical output signal from the control system, the moveable permanent magnet member being connected to the tool to move the tool in accordance with said output signal, the tool and the workpiece being relatively rotatable about a workpiece axis.
2. A machine tool according to claim 1, wherein the D.C.linear motor includes a generally U-shaped core with a stator coil on each limb of the U and with the movable permanent magnet member extending between the limbs of the U.
3. A machine tool according to claim 1 or claim 2 and further comprising positioning means for applying a force to the movable permanent magnetic member tending to maintain the tool in a datum position, the tool moving from said datum position to required tool positions for machining the non-uniform surface profile.
4. A machine tool according to claim 3, wherein the positioning means comprises two diaphragms lying in respective spaced planes normal to the axis of the movable permanent magnet member and connected to the movable permanent magnet member so that the axis of said movable permanent magnet member is co-axial with axes of the diaphragms.
5. A machine tool according to claim 4, wherein the diaphragms are metal diaphragms.
6. A machine tool according to claim 4 or claim 5, wherein the movable permanent magnet member is surrounded by a fixed cylindrical housing co-axial therewith and the diaphragms have outer peripheries which are connected to the fixed housing.
7. A machine tool according to claim 3, wherein the tool positioning means comprise at least one gas bearing.
8. A machine tool according to claim 3, wherein the tool positioning means comprises a plurality of flexible plates lying in respective planes normal to the length of the movable permanent magnet member, the plates being connected between the movable permanent magnet member and the base.
9. A machine tool substantially as hereinbefore described with reference to any one of Figs. 1 to 4 of the accompanying drawings.
GB08700631A 1983-06-16 1984-06-15 Machine tools Expired GB2184381B (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB838316428A GB8316428D0 (en) 1983-06-16 1983-06-16 Machine tools
GB838325295A GB8325295D0 (en) 1983-09-21 1983-09-21 Tool actuators for machine tools
GB08415331A GB2142860B (en) 1983-06-16 1984-06-15 Machine tools

Publications (3)

Publication Number Publication Date
GB8700631D0 GB8700631D0 (en) 1987-02-18
GB2184381A true GB2184381A (en) 1987-06-24
GB2184381B GB2184381B (en) 1988-03-09

Family

ID=27262138

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08700631A Expired GB2184381B (en) 1983-06-16 1984-06-15 Machine tools

Country Status (1)

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GB (1) GB2184381B (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0328972A2 (en) * 1988-02-19 1989-08-23 The Cross Company Method and system for controlling a machine tool such as turning machine
US4990840A (en) * 1988-02-19 1991-02-05 The Cross Company Method and system for controlling a machine tool such as a turning machine
EP0429659A1 (en) * 1989-05-29 1991-06-05 Kabushikigaisha Sekogiken Driving system and controller therefor
EP0512867A2 (en) * 1991-05-10 1992-11-11 University Of Bristol Removing material from a workpiece
EP1001186A2 (en) * 1995-09-23 2000-05-17 Rovema Verpackungsmaschinen GmbH Apparatus for moving at least one component

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0328972A2 (en) * 1988-02-19 1989-08-23 The Cross Company Method and system for controlling a machine tool such as turning machine
EP0328972A3 (en) * 1988-02-19 1990-05-23 The Cross Company Method and system for controlling a machine tool such as turning machine
US4990840A (en) * 1988-02-19 1991-02-05 The Cross Company Method and system for controlling a machine tool such as a turning machine
EP0429659A1 (en) * 1989-05-29 1991-06-05 Kabushikigaisha Sekogiken Driving system and controller therefor
EP0429659A4 (en) * 1989-05-29 1992-08-26 Kabushikigaisha Sekogiken Driving system and controller therefor
EP0512867A2 (en) * 1991-05-10 1992-11-11 University Of Bristol Removing material from a workpiece
EP0512867A3 (en) * 1991-05-10 1993-03-03 University Of Bristol Removing material from a workpiece
EP1001186A2 (en) * 1995-09-23 2000-05-17 Rovema Verpackungsmaschinen GmbH Apparatus for moving at least one component
EP1001186A3 (en) * 1995-09-23 2000-06-28 Rovema Verpackungsmaschinen GmbH Apparatus for moving at least one component

Also Published As

Publication number Publication date
GB2184381B (en) 1988-03-09
GB8700631D0 (en) 1987-02-18

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19990615