Optimised polishing media - a new approach
Lead Research Organisation:
University of Huddersfield
Department Name: Sch of Computing and Engineering
Abstract
This project aims to prove the feasibility of polishing a variety of surfaces, using a new combination of enhanced polishing slurries, tools and tool-motions.
The ultimate objective is to generate significant commercial advantage in both the rate of material removed (economics of production), and the ability to remove mid spatial frequencies (ripples) on surfaces (quality of production). If this work is successful, we hope to attract a manufacturer of specialist polishing slurries to engage with a subsequent phase of development, and ultimately bring a new range of slurries to market.
The research has potential to benefit a wide range of applications that require precision surface-finishing, including optics, prosthetic joint-implants, bearing surfaces, turbine blades and moulds¨s. Relevant sectors embrace defence, aero-space, medical, consumer, instrumentation, and Science Base.
The ultimate objective is to generate significant commercial advantage in both the rate of material removed (economics of production), and the ability to remove mid spatial frequencies (ripples) on surfaces (quality of production). If this work is successful, we hope to attract a manufacturer of specialist polishing slurries to engage with a subsequent phase of development, and ultimately bring a new range of slurries to market.
The research has potential to benefit a wide range of applications that require precision surface-finishing, including optics, prosthetic joint-implants, bearing surfaces, turbine blades and moulds¨s. Relevant sectors embrace defence, aero-space, medical, consumer, instrumentation, and Science Base.
Publications
Li H
(2019)
Mid-spatial frequency removal on aluminum free-form mirror.
in Optics express
Walker D
(2019)
Fully automating fine-optics manufacture - why so tough, and what are we doing?
in Journal of the European Optical Society-Rapid Publications
| Description | The purpose of this project was to investigate non-Newtonian polishing slurries - that is, abrasive suspensions that stiffen under shear forces. We created such slurries using two different non-Newtonian media. However, we failed to find significant removal in practical trials. These trials used a Zeeko CNC polishing machine, where an inflated rubber-membrane, covered with polishing cloth, is rotated and pressed against the workpiece surface, to give a localised "spot of action". This lack of removal remained the case for a variety of polishing conditions. Very late - we had a breakthrough. The polishing bonnet was lifted off the work-piece surface, leaving a gap of a fraction of a mm. Remarkably, and unexpectedly, we then saw significant and useful material removal. Apparently, the shear forces were drawing the stiffened slurry through the gap, requiring no physical contact of the tool. The result is a completely novel process, which we are calling n-MRF (non-magneto rheological finishing). We are currently investigating this in more detail, from the perspectives of measuring rheological properties of the fluids, computer modelling of the process, and experimental determination of removal rate, and removal of mid-spatial-frequencies, in preparation for a patent filing. That is why we are not publishing this invention yet. |
| Exploitation Route | This is a process with no contact between a physical tool and the workpiece surface, avoiding issues of tool-misfit on aspheric and freeform surfaces. The experimental programme was severely hampered, first by the strategic re-location of our laboratory from the OpTIC Centre in N. Wales to the Daresbury campus, which (following negotiation with OpTIC) resulted in the loss of key equipment needed for the research. This is now mostly replaced, with final items on order. However, after the relocation, COVID then intervened severely limiting access to the new lab. The work has been resumed and, subject to the final stages of experimental characterisation, we foresee applications in optical manufacturing, the mould and die sector, and other complex surfaces such as turbine blades and prosthetic joint implants. We are currently in discussion with the ASTEC group at Daresbury about applications in polishing RF cavities for accelerators. The prospective end-users are thus in scientific research and advanced manufacturing. These applications will require a secure supply of specialist slurries, and we will be contacting polishing consumable manufacturer Kemet Ltd as a prospective licenser of the technology, and partner in its further development. However, this must await finalisation of on-going experimental work, and patent protection. A paper and PhD thesis are in preparation subject to protecting IP. |
| Sectors | Aerospace, Defence and Marine,Chemicals,Digital/Communication/Information Technologies (including Software),Energy,Healthcare,Manufacturing, including Industrial Biotechology,Other |
| Description | IAC collaboration |
| Amount | € 14,458 (EUR) |
| Funding ID | AAM003825 |
| Organisation | Institute of Astrophysics of the Canary Islands |
| Sector | Academic/University |
| Country | Spain |
| Start | 08/2022 |
| End | 11/2022 |
| Description | Under the skin of polishing - from nano to macro |
| Amount | £522,021 (GBP) |
| Funding ID | EP/V029304/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 07/2021 |
| End | 12/2024 |
| Title | Non-Newtonian polishing media |
| Description | Invention of a completely novel technique for removing material in polishing and allied processes, requiring no contact between a physical tool and the workpiece. Subject to current characterisation, potentially highly-relevant to processing complex 'freeform' surfaces in several sectors. Therefore an enhancement to manufacturing capability. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2018 |
| Provided To Others? | No |
| Impact | Too early for impact - too early to disseminate. Need to complete on-going characterisation, and then patent beforehand. |
| Title | Data for polishing and associated processes |
| Description | Data on polishing, grolishing and metrology results for a wide range of removal technologies, and operating parameters, including deployment on CNC polishing machines and robots, and using both free and bound abrasives. |
| Type Of Material | Database/Collection of data |
| Provided To Others? | No |
| Impact | This data is the bedrock on which we are researching advanced ultra-precision surface techniques, and methods of process automation. It is also being used in processing real components, for example the primary and secondary mirrors for LOCUS. |
| Description | Kemet Ltd collaboration |
| Organisation | Kemet International |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | We assessed a competitor's polishing compound and found it crystallized out in use, causing damage to equipment. We introduced Kemet to the special needs of CNC and robotic corrective polishing using small tools and progressive tool-paths. This was very different from their previous experience using large lapping plates, where tool and part are always in full contact. We tested a particular Kemet abrasive optimised for bare-aluminium and provided results back. It proved highly effective, but too slow for small-tool corrective polishing. Kemet then developed a range of abrasives of different particle sizes, to increase removal rate. |
| Collaborator Contribution | Development of optimised polishing media. |
| Impact | Successful completion of LOCUS -CEOI project STFC IPS proposal submitted with Kemet, Feb 2020 Kemet launched new abrasive slurries for aluminium |
| Start Year | 2016 |
| Description | Non Newtonian Materials |
| Organisation | Sheffield Hallam University |
| Department | Materials and Engineering Research Institute (MERI) |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Development of tooling, and non-Newtonian polishing slurries, and conducting polishing trials. |
| Collaborator Contribution | As part of this research project (and as per the grant proposal) we have been working with Prof Andrew Alderson at Sheffield Hallam University - an expert in non-Newtonian materials. Huddersfield is employing him as a consultant. He is advising on these advanced materials and their action within polishing slurries. |
| Impact | Theory predicts that a non-Newtonian polishing slurry should harden as it is drawn under a precessed, rotating polishing bonnet, and then preferentially remove mid spatial frequency features from surfaces. Within this 9-month grant we have conducted experimental trials with different non-Newtonian slurries, in combination with advanced tool-paths, with inconclusive results. We are currently standing back and, with Prof Alderson, working to understand and interpret these results, We expect to conduct more trials with a view to diagnosing the physics of what is going on, and hopefully arrive at process parameters that demonstrate the positive effects of the non-Newtonian slurries. In response to this we are, in parallel, also considering non-Newtonian materials inside polishing bonnets. Whilst this has been done before using 'Silly Putty'( as reported by U. Arizona and used extensively by us), the new understanding from the STFC grant is expected to lead to alternative non-Newtonian materials in tools, with potentially superior performance. This in turn has led to the concept of actively stimulating non-Newtonian behaviour in a tool where, on the surface of the part, it should optimally be targeted. This is novel. These future developments are included as a work-package in our Programme Grant proposal, which is at the final stages of assessment by EPSRC. Sheffield Hallam is a partner in that proposal, and Prof Alderson is a Co-I. |
| Start Year | 2017 |