WO2015091615A1 - Surface finishing of components - Google Patents

Surface finishing of components Download PDF

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Publication number
WO2015091615A1
WO2015091615A1 PCT/EP2014/078170 EP2014078170W WO2015091615A1 WO 2015091615 A1 WO2015091615 A1 WO 2015091615A1 EP 2014078170 W EP2014078170 W EP 2014078170W WO 2015091615 A1 WO2015091615 A1 WO 2015091615A1
Authority
WO
WIPO (PCT)
Prior art keywords
component
slurry
container
particles
surface finishing
Prior art date
Application number
PCT/EP2014/078170
Other languages
French (fr)
Inventor
Jagjit Sidhu
Andrew David Wescott
Jeffrey Paul Sargent
Original Assignee
Bae Systems 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 GB201322402A external-priority patent/GB201322402D0/en
Priority claimed from EP13275321.1A external-priority patent/EP2886247A1/en
Application filed by Bae Systems Plc filed Critical Bae Systems Plc
Publication of WO2015091615A1 publication Critical patent/WO2015091615A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
    • B24B1/04—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes subjecting the grinding or polishing tools, the abrading or polishing medium or work to vibration, e.g. grinding with ultrasonic frequency
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B31/00—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor
    • B24B31/06—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving oscillating or vibrating containers
    • B24B31/064—Machines or devices designed for polishing or abrading surfaces on work by means of tumbling apparatus or other apparatus in which the work and/or the abrasive material is loose; Accessories therefor involving oscillating or vibrating containers the workpieces being fitted on a support

Definitions

  • This invention relates to the surface finishing of components, in particular to the surface finishing of components having awkward shapes which make mechanical polishing difficult and more particularly to such components made by an additive manufacturing (AM) process.
  • AM additive manufacturing
  • Additive manufacturing is being promoted as bringing about the next manufacturing revolution.
  • This technology enables the fabrication of components of very complex design, including designs that can have enclosed cavities and interlocking parts.
  • the technology is particularly suited to high value parts, low batch manufacturing, and mass customisation.
  • this technology is suitable for aerospace components, components for ships, for radar structures and dishes, etc.
  • limitations to the application of AM technology are the result of typical surface roughness of AM components. This roughness can affect the dynamic mechanical properties of the component.
  • Components can currently be sand blasted or computer numerically controlled (CNC) machined to overcome these limitations.
  • CNC machining is expensive and sand blasting does not always provide the tolerances and control required.
  • a method of surface finishing a component including the steps of surrounding the component with a liquid slurry containing particles of hardness at least as great as a surface of the component to be surface finished and agitating the slurry with acoustic waves to cause the particles to vibrate back and forth with sufficient energy to abrade the surface of the component for the required surface finish.
  • This invention thus provides to an easy-to-use process for improving the surface finish of typical AM components and which is equally suitable for polishing open surfaces and enclosed surfaces and cavities.
  • the slurry and component may be contained in a container and at least one acoustic transducer may be placed in contact with a surface of the container and vibrated against that surface.
  • the surface is likely to be an outer surface of the container.
  • the vibration frequency is preferably high and more preferably in the ultrasonic range. This has the advantage that surface finishing will be faster than with a lower frequency. Also, the resulting surface finish may be smoother, is so desired.
  • the acoustic waves may be formed at varying frequency. Also, for similar reasons, the position of the at least one acoustic transducer may be varied, during surface finishing.
  • the position and/or orientation of the component may be varied during surface finishing.
  • the component may be rotated within the container, during surface finishing, for example on a carousel.
  • Time taken for the surface finishing will vary according to the degree of surface finishing, e.g., polishing, required, also the efficiency of the process.
  • the time taken may be a number of hours.
  • the method of the invention may be carried out at room temperature but heating due to the ultrasonic energy created may raise the operating temperature. Suitable cooling may be applied if necessary, for example if a particularly temperature-sensitive plastics material is being surface finished.
  • ALM components may be generally limited to a size of approximately 250mm. This will increase with time and development of the ALM process.
  • Any shape of component may be treated by the method of the invention, so long as the slurry can gain access to the surface required to be treated.
  • components including hollows and cavities such as pipes, components with complex joints such as fluid pipes through aircraft and submarines, ventilation and air conditioning systems piped through aircraft, components with internally movable parts such as ball joints, one piece hinges, may be surface finished by the method or apparatus of the invention.
  • apparatus for surface finishing a component including a container for the component, slurry in the container, the slurry containing particles of hardness at least as great as that of a surface of the component to be surface finished, at least one acoustic transducer coupled to the slurry, the acoustic transducer being arranged to agitate the particles in the slurry whereby to surface finish the component.
  • the figure shows a metal container in the form of a circular tank 1 .
  • the tank is filled with slurry 2 and has a pair of movable acoustic transducers 3, 4 rotatably attached to an outside surface 5 thereof.
  • an example component in this case an adjustable spanner 6 mounted on a rotating carousel 12.
  • the spanner 6 is complex in construction and has open surfaces 7, cavities 8 and interlocking parts 9, 10.
  • the tank 1 is shown as circular but may be other shapes, where more suitable.
  • a circular tank has the benefit of enabling easy movement of transducers 3, 4 around the tank, in use.
  • the slurry 2 is made from a chemically inert liquid, here water, and polishing particles (not separately shown). Polishing particles must be selected for their size and hardness, for the component being treated. Their hardness needs to be as great, or greater than, the material of the component 6 and to be sufficiently small as to form a suspension in the liquid. Larger particles may be used for rough polishing and smaller particles may be used for a finer polish.
  • hard polishing particles for the slurry are garnet, tungsten carbide and aluminium oxide. Other materials of hardness which is selected for the hardness and type of the surface to be polished may also be used.
  • typical ALM-produced materials to be surface finished are a titanium alloy, Ti6A14V and aluminium alloys.
  • suitable materials typically made by ALM are steels and nickel alloys.
  • the method of the invention is not limited by the material of the component. Plastics, for example laser sintered plastics such as nylon and other thermoset and thermoplastics, are equally suitable for surface finishing by this method.
  • acoustic waves are transmitted from the acoustic transducers 3, 4 which cause the polishing particles to move back and forth in the liquid to locations determined by positions of acoustic nodes and antinodes. Abrasive action between the polishing particles and the surface of the component 6 leads to surface polishing taking place.
  • Acoustic frequency is determined by the requirement for sufficient particle movement; by the size of the polishing particles relative to the wavelength of the ultrasound, and by the acoustic impedance difference between the chemically inert medium (water here) and the particles.
  • Particles such as garnet, tungsten carbide and aluminium oxide, with a size comparable to the acoustic wavelength, will result in a large scattering cross section.
  • Attenuation of the signal within the water depends upon the particle volume fraction; the acoustic frequency, and the particle size and type. In order to provide sufficient particle excitation within the tank and to overcome attenuation, a judicious choice of frequency and power levels is required in order for the required degree of particle excitation to reach all required areas of the component.
  • Acoustic powers of several tens or hundreds of watts are envisaged, with frequencies of typically 10MHz - 100MHz for wavelengths of approximately 150 to 15microns in water.
  • the transducers 6 may be continuously scanned across frequencies. However, if selected areas, only, of the component 6 are to be polished then standing waves can be deliberately generated by using fixed frequencies.
  • Transducers 3, 4 could also be coupled from the bottom 1 1 and a top (not shown) of the tank. This will further increase acoustic field coverage and may enable an increase in the power coupled into the slurry.
  • the tank 1 needs to be full of the slurry, in order for the acoustic waves from a transducer coupled to the top to be effectively transmitted into the slurry.

Abstract

There is provided apparatus and a method for surface finishing a component (6) which may be manufactured by additive layer manufacturing and may be of awkward shape. The apparatus includes a container (1) for the component, slurry (2) containing polishing particles and acoustic transducers (3, 4) mounted on the container and acoustically coupled to the slurry. The acoustic transducers are arranged to agitate the particles in the slurry whereby to abrade and surface finish the component.

Description

SURFACE FINISHING OF COMPONENTS
This invention relates to the surface finishing of components, in particular to the surface finishing of components having awkward shapes which make mechanical polishing difficult and more particularly to such components made by an additive manufacturing (AM) process.
Additive manufacturing is being promoted as bringing about the next manufacturing revolution. This technology enables the fabrication of components of very complex design, including designs that can have enclosed cavities and interlocking parts. The technology is particularly suited to high value parts, low batch manufacturing, and mass customisation. Thus this technology is suitable for aerospace components, components for ships, for radar structures and dishes, etc. Currently, limitations to the application of AM technology are the result of typical surface roughness of AM components. This roughness can affect the dynamic mechanical properties of the component. Components can currently be sand blasted or computer numerically controlled (CNC) machined to overcome these limitations. However, CNC machining is expensive and sand blasting does not always provide the tolerances and control required. According to a first aspect of the present invention, there is provided a method of surface finishing a component, the method including the steps of surrounding the component with a liquid slurry containing particles of hardness at least as great as a surface of the component to be surface finished and agitating the slurry with acoustic waves to cause the particles to vibrate back and forth with sufficient energy to abrade the surface of the component for the required surface finish.
This invention thus provides to an easy-to-use process for improving the surface finish of typical AM components and which is equally suitable for polishing open surfaces and enclosed surfaces and cavities. The slurry and component may be contained in a container and at least one acoustic transducer may be placed in contact with a surface of the container and vibrated against that surface. The surface is likely to be an outer surface of the container.
The vibration frequency is preferably high and more preferably in the ultrasonic range. This has the advantage that surface finishing will be faster than with a lower frequency. Also, the resulting surface finish may be smoother, is so desired.
In order to avoid regions on the component of over-polishing or under- polishing, the acoustic waves may be formed at varying frequency. Also, for similar reasons, the position of the at least one acoustic transducer may be varied, during surface finishing.
Further, to ensure even and consistent polishing of the component, the position and/or orientation of the component may be varied during surface finishing. In order to achieve this, the component may be rotated within the container, during surface finishing, for example on a carousel. Time taken for the surface finishing will vary according to the degree of surface finishing, e.g., polishing, required, also the efficiency of the process. Thus, the particular selected combination of material to be surface finished and slurry particles, the vibration power and frequency, the efficiency of coupling of the vibrations into the slurry and the shape of the component will all affect the time taken. The time taken may be a number of hours.
It will be appreciated that the method of the invention may be carried out at room temperature but heating due to the ultrasonic energy created may raise the operating temperature. Suitable cooling may be applied if necessary, for example if a particularly temperature-sensitive plastics material is being surface finished.
The method of the invention may be applied to any size of component. However, at present, ALM components may be generally limited to a size of approximately 250mm. This will increase with time and development of the ALM process. Any shape of component may be treated by the method of the invention, so long as the slurry can gain access to the surface required to be treated. Thus, in particular, components including hollows and cavities such as pipes, components with complex joints such as fluid pipes through aircraft and submarines, ventilation and air conditioning systems piped through aircraft, components with internally movable parts such as ball joints, one piece hinges, may be surface finished by the method or apparatus of the invention.
According to a second aspect of the invention, there is provided apparatus for surface finishing a component, the apparatus including a container for the component, slurry in the container, the slurry containing particles of hardness at least as great as that of a surface of the component to be surface finished, at least one acoustic transducer coupled to the slurry, the acoustic transducer being arranged to agitate the particles in the slurry whereby to surface finish the component. The invention now will be described by way of example with reference to the accompanying drawing which shows, schematically, apparatus according to the invention.
Referring to the drawing, the figure shows a metal container in the form of a circular tank 1 . The tank is filled with slurry 2 and has a pair of movable acoustic transducers 3, 4 rotatably attached to an outside surface 5 thereof. Inside the tank 1 is shown an example component, in this case an adjustable spanner 6 mounted on a rotating carousel 12. It will be noted that the spanner 6 is complex in construction and has open surfaces 7, cavities 8 and interlocking parts 9, 10. The tank 1 is shown as circular but may be other shapes, where more suitable. A circular tank has the benefit of enabling easy movement of transducers 3, 4 around the tank, in use.
The slurry 2 is made from a chemically inert liquid, here water, and polishing particles (not separately shown). Polishing particles must be selected for their size and hardness, for the component being treated. Their hardness needs to be as great, or greater than, the material of the component 6 and to be sufficiently small as to form a suspension in the liquid. Larger particles may be used for rough polishing and smaller particles may be used for a finer polish.
Examples of hard polishing particles for the slurry are garnet, tungsten carbide and aluminium oxide. Other materials of hardness which is selected for the hardness and type of the surface to be polished may also be used. For aerospace components, typical ALM-produced materials to be surface finished are a titanium alloy, Ti6A14V and aluminium alloys. Other suitable materials typically made by ALM, are steels and nickel alloys. However, it will be appreciated that the method of the invention is not limited by the material of the component. Plastics, for example laser sintered plastics such as nylon and other thermoset and thermoplastics, are equally suitable for surface finishing by this method.
In use, acoustic waves are transmitted from the acoustic transducers 3, 4 which cause the polishing particles to move back and forth in the liquid to locations determined by positions of acoustic nodes and antinodes. Abrasive action between the polishing particles and the surface of the component 6 leads to surface polishing taking place.
Acoustic frequency is determined by the requirement for sufficient particle movement; by the size of the polishing particles relative to the wavelength of the ultrasound, and by the acoustic impedance difference between the chemically inert medium (water here) and the particles. Particles such as garnet, tungsten carbide and aluminium oxide, with a size comparable to the acoustic wavelength, will result in a large scattering cross section. Attenuation of the signal within the water depends upon the particle volume fraction; the acoustic frequency, and the particle size and type. In order to provide sufficient particle excitation within the tank and to overcome attenuation, a judicious choice of frequency and power levels is required in order for the required degree of particle excitation to reach all required areas of the component. Acoustic powers of several tens or hundreds of watts are envisaged, with frequencies of typically 10MHz - 100MHz for wavelengths of approximately 150 to 15microns in water. In order to prevent standing waves and hence fixed locations of nodes and antinodes, which may cause abrasion/polishing only in selected areas, the transducers 6 may be continuously scanned across frequencies. However, if selected areas, only, of the component 6 are to be polished then standing waves can be deliberately generated by using fixed frequencies.
Moving the transducers 3, 4 around the tank 1 , as shown by the arrows, will also prevent the generation of standing waves and this technique may be used in combination with frequency variation.
Transducers 3, 4 could also be coupled from the bottom 1 1 and a top (not shown) of the tank. This will further increase acoustic field coverage and may enable an increase in the power coupled into the slurry. Clearly, the tank 1 needs to be full of the slurry, in order for the acoustic waves from a transducer coupled to the top to be effectively transmitted into the slurry.

Claims

A method of surface finishing a component, the method including the steps of surrounding the component with a liquid slurry containing particles of hardness at least as great as a surface of the component to be surface finished and agitating the slurry with acoustic waves to cause the particles to vibrate back and forth with sufficient energy to abrade the surface of the component for the required surface finish.
A method according to claim 1 , in which the slurry and component are contained in a container and at least one acoustic transducer is placed in contact with a surface of the container and vibrated against the surface.
A method according to claim 2, in which the at least one acoustic transducer is placed in contact with an outer surface of the container.
A method according to claim 1 , 2 or 3, in which the acoustic waves are formed as ultrasonic waves.
A method according to any preceding claim, in which the acoustic waves are formed at varying frequency.
A method according to any of claims 2 to 5, in which the position of the at least one acoustic transducer is varied during surface finishing.
A method according to any preceding claim, in which the position and/or orientation of the component is varied during surface finishing.
A method according to claim 7, in which the component is rotated on a carousel, during surface finishing.
A method according to any preceding claim, in which the surface finishing particles of the slurry are selected according to the type of surface finish required for the component.
A method according to claim 9, wherein the surface finishing particles are selected to be of varying hardness and/or shape.
1 1 . Apparatus for surface finishing a component, the apparatus including a container for the component, slurry in the container, said slurry containing particles of hardness at least as great as that of a surface of the component to be surface finished, at least one acoustic transducer coupled to the slurry, the acoustic transducer being arranged to agitate the particles in the slurry whereby to abrade the surface of the component for the required surface finish.
12. Apparatus according to claim 1 1 , in which the at least one acoustic transducer is mounted to a surface of the container.
13. Apparatus according to claim 1 1 or 12, in which the at least one acoustic transducer is an ultrasonic transducer.
14. Apparatus according to claim 1 1 , 12 or 13, including means to move and/or rotate at least one of the at least one transducer and the component during surface finishing.
15. Apparatus according to claim 14, in which the rotational means includes a carousel upon which to mount the component, within the container.
16. Apparatus according to any of claims 1 1 to 15, in which the at least one transducer is operable at varying frequency.
PCT/EP2014/078170 2013-12-18 2014-12-17 Surface finishing of components WO2015091615A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB201322402A GB201322402D0 (en) 2013-12-18 2013-12-18 Surface finishing of components
GB1322402.7 2013-12-18
EP13275321.1A EP2886247A1 (en) 2013-12-18 2013-12-18 Surface Finishing of Components
EP13275321.1 2013-12-18

Publications (1)

Publication Number Publication Date
WO2015091615A1 true WO2015091615A1 (en) 2015-06-25

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2545956A (en) * 2015-12-22 2017-07-05 Rolls Royce Plc Vibro-Polishing Arrangement
EP3659721A1 (en) * 2018-11-27 2020-06-03 Rolls-Royce plc Finishing a surface of a component made by additive manufacturing
FR3093018A1 (en) * 2019-02-25 2020-08-28 Psa Automobiles Sa ULTRASONIC ONE PIECE POLISHING PROCESS

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4171852A (en) * 1977-06-27 1979-10-23 Haentjens Walter D Propulsion of slurry along a pipeline by ultrasonic sound waves
JPS63185556A (en) * 1987-01-28 1988-08-01 Toshiba Corp Polishing device
US5531861A (en) * 1993-09-29 1996-07-02 Motorola, Inc. Chemical-mechanical-polishing pad cleaning process for use during the fabrication of semiconductor devices
US5895550A (en) * 1996-12-16 1999-04-20 Micron Technology, Inc. Ultrasonic processing of chemical mechanical polishing slurries
CN101344468A (en) * 2008-08-25 2009-01-14 浙江工业大学 Sound suspending polissoir for nanometer mechanics characterization sample

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4171852A (en) * 1977-06-27 1979-10-23 Haentjens Walter D Propulsion of slurry along a pipeline by ultrasonic sound waves
JPS63185556A (en) * 1987-01-28 1988-08-01 Toshiba Corp Polishing device
US5531861A (en) * 1993-09-29 1996-07-02 Motorola, Inc. Chemical-mechanical-polishing pad cleaning process for use during the fabrication of semiconductor devices
US5895550A (en) * 1996-12-16 1999-04-20 Micron Technology, Inc. Ultrasonic processing of chemical mechanical polishing slurries
CN101344468A (en) * 2008-08-25 2009-01-14 浙江工业大学 Sound suspending polissoir for nanometer mechanics characterization sample

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2545956A (en) * 2015-12-22 2017-07-05 Rolls Royce Plc Vibro-Polishing Arrangement
GB2545956B (en) * 2015-12-22 2018-03-07 Rolls Royce Plc Vibro-polishing arrangement
EP3659721A1 (en) * 2018-11-27 2020-06-03 Rolls-Royce plc Finishing a surface of a component made by additive manufacturing
CN111299592A (en) * 2018-11-27 2020-06-19 劳斯莱斯有限公司 Modifying a surface of a component prepared by additive manufacturing
US11123840B2 (en) 2018-11-27 2021-09-21 Rolls-Royce Plc Finishing a surface of a component made by additive manufacturing
CN111299592B (en) * 2018-11-27 2024-01-12 劳斯莱斯有限公司 Finishing the surface of a part made by additive manufacturing
FR3093018A1 (en) * 2019-02-25 2020-08-28 Psa Automobiles Sa ULTRASONIC ONE PIECE POLISHING PROCESS

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