In Jet Interferometry for Ultra Precise Electrolyte Jet Machining

Lead Research Organisation: University of Nottingham
Department Name: Faculty of Engineering

Abstract

Ultra-precision machining techniques permit the manufacture of the most high value components. Component complexity continues to develop and researchers are challenged to remove smaller volumes of material in a more precise manner while maintaining work piece integrity. Micro-machining, micro electrical discharge/electrochemical machining and high speed laser processes are now commonly used for micro component manufacture for the microelectronics, biomedical and aerospace industries. Electrolyte Jet Machining (EJM) is a newer process which is yet to be embraced in a meaningful way by these industries. The process itself has several attractive capabilities, such as the ability to process difficult to machine materials with no resulting thermal loading of parts and no induced residual stress. A particularly interesting aspect of the technology is that, with simple modifications, the process may also run in reverse as an additive manufacturing technique to precisely deposit materials.

The work to be undertaken here will make use of a custom built MkI prototype EJM tool at the University of Nottingham which was recently completed by the Investigators. As well as being able to perform material surface machining, this has unique capabilities and represents a significant advancement in terms of the state-of-the-art. The investigators have demonstrated a new functionality in terms of computer controlled signal generation which is capable of creating so called 'dial-up-surfaces' or surface manufacture against a specification for surface texture/morphology as opposed to surface roughness alone. Surface texture control within a machining process is notoriously difficult to achieve, commanding a premium price for high value components since surface condition often dictates performance. Typically, micro surface textures are of interest to several groups of researchers outside of engineering. These include biomedical researchers who study cell/surface interaction and aerodynamicists who look to enhance the performance of surfaces interacting with fluid flow.

To unlock the full potential of EJM, novel on machine instrumentation must be created. This instrumentation must allow fast, accurate, high precision process data to be collected to support real-time adaptive process control. It should also allow for on-machine surface metrology to be undertaken which is increasingly an essential requirement for successful industrial processes. For EJM to be successfully exploited in both a research environment, and critically as a viable production technology this novel set of process instrumentation must be investigated and then developed to allow accurate and timely metrology to be undertaken on the machine while the process is under way.

The instrumentation to be investigated here will be split into two key areas. Firstly, a novel form of in-jet laser interferometer will be designed and optimised for use with EJM. The sensor will provide high speed, high precision process control measurement data. This will allow the material removal rate of the process and the form of the material removal area directly in line with the jet to be measured. In addition a fibre optic arrangement will be included to allow beam delivery. Since stand-off distances are short within EJM this will be possible with a high brightness source (laser) to deliver a spot to the work piece. In addition to the in-jet laser two additional sensors will be deployed to the machine head, external to the jet. These will be custom designed single line coherence scanning interferometer devices, configured for single line based detection (to allow increased acquisition rates).

These techniques will allow the collection of disparate data sets in real-time which will be manipulated through control algorithms to perform online processing and adaptive machining. This represents a step change in the viability of this process for the production of complex and high value parts.

Planned Impact

The impact of this project will be felt in the development of a new manufacturing capability built upon Electrolyte Jet Machining. The development of new instrumentation will unlock new potential in this area. Enhanced capability will be first utilised as part of this project for collaboration with researchers outside of engineering who seek to enhance surface performance in both bioengineering and chemical processing. Furthermore industrial partners who have engaged in this project range from technology users (Precision Micro and Rolls-Royce) through to metrology machine makers (Taylor Hobson). Naturally work undertaken here will also contribute directly to the global research community within non-conventional machining, and optical metrology.

The domestic industrial and research need is significant. Augmentation of the EJM process is likely to have critical impact in industrial sectors of biomedical implants and aeroengine manufacture, stalwarts of the UK economy. Both areas make use of highly resistant engineering materials whose performance in service is safety critical. For this reason many thermal manufacturing processes (laser, EDM etc) cannot be used. Hence alternatives for precision finishing are essential. Furthermore, there are several key areas of interest (stay clean surface, expedited bone ingress) for which structured surfaces may enhance component performance in service. However, all processes used to create these must be validated. With the development of the instrumentation proposed here the way will be paved for EJM to be explored for these applications.

Industrial impact and pathway development will be achieved by a series of seminar sessions for which funding has been requested in this project. These will permit project partners and invitees external to project to receive a demonstration of this machining technique and the underpinning instrumentation. Funding has also been requested to allow the investigators to produce a series of specimens and provide accompanying process and metrology data as part of this activity. By targeting researchers from disciplines outside of engineering it is expected that highly interdisciplinary follow on activity will emerge from the final stages of this project. Between industrial collaboration and research facilitation there are a range of short term through to longer term impact routes associated with this project.

Reach into the academic community will be addressed through tradition routes of journal publication and disseminations at recognised international conferences. Efforts will be made to see that dissemination also takes place beyond traditional manufacturing outlets to ensure that exposure of the outputs from the project is maximised.

Publications

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Description To date the project (staffed by Mr Jonathon Mitchell-Smith (RA) and Mr Alistair Speidal (PhD student)) have made significant advances to the process which will be instrumented as part of this project.
Innovation here can be grouped into two principle areas; process innovation [JMS} and chemistry development {AS}.
Through process innovation new hardware has been built to accommodate the instrumentation that will be developed as part of this project. This has required the team at Nottingham to consider several head designs, stage configurations and electrolyte feed methods which all serve to govern the efficacy of the process.
Similarly with respect to chemistry development the team as been developing more appropriate methods of preparing electrolytes for the process. This is allowing for advanced surface control, hybridised subtractive and additive processing for high value components. This has garnered interest from within Rolls-Royce and is expected to progress at pace.

[2017] Over the last 12 months this project has gathered pace and investigators have welcomed numerous visitors from the aerospace, biomedical and tool industries to engage with the hardware. The machine build is progressing well and a number of publications have been produced. In addition further students (phd) are due to start in this area from September 17 alongside a recent UNICAS award which will allow biomedical scientists to make use of innovation made during this project. [2018] an IAA grant was awarded.
Exploitation Route Consistent with our impact plan the team has identified several routes to impact through engagement with industrial partners in the aerospace and metrology sectors. Regular visits are made as a matter of course between project partners and partner Universities to develop this.
Key advances to the process technology are allowing the potential of a real machine tool to be developed while the developments to the chemistry which underpins the process is key.

[2019] Our spin out company is now in progress and following 15 publications we are now demonstrating leadership internationally in this field.
Sectors Aerospace, Defence and Marine,Chemicals,Electronics,Energy,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description This project is approximately 10 months into a 3 year program however, there has been notable engagement with research partners both in academia and industry and particular interest has been expressed by Rolls-Royce. Our results have begun to be utilised by Hackert et al. (Germany) and Kunieda et al. (Germany) in their efforts to develop the EJM process. I have met with Prof Kunieda, UoT, on a number of occasions this calendar year and our work is feeding into the efforts of this group. Based on our initial work we are now developing a machine tool capability which incorporates our innovations. It is expected that we will produce a demonstrator machine tool mid 2016. [2019] We have now won two consecutive icure projects and it it highly likley we will spin out a company 'texturejet' in the next month. we have extensive interest from Rolls-Royce and a number of commercial partners.
Sector Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Impact Accelerator Account
Amount £56,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 04/2018 
End 12/2019