Developing a Bespoke Incremental Sheet Forming Machine for Cranioplasty

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


Cranioplasty is a surgical procedure for the repair of deformity of a human skull due to brain tumour, stroke or traumatic injuries. Among all available materials, titanium continues to be a main stream material used in cranioplasty surgeries because of its excellent biocompatibility, resistance to infection, excellent material properties and lightweight. However, in spite of the popular use of titanium in cranial reconstruction, there is a wide variety of methods including casting, manual shaping and rubber press forming commonly used in cranial plate manufacture. Even with the assistance of advanced CAD/CAM (computer-aided design and manufacture) and computed tomographic (CT) and magnetic resonance imaging (MRI) technologies, currently the process for manufacturing customised cranial plates by conventional methods normally takes up to two weeks to completion mainly due to the time required for the manufacture of dies and tools. Recent advances in 3D printing or additive manufacturing based techniques make it possible to complete the 3D printing of a cranial or a maxillofacial prosthetic part within several hours. However, there are still a number of impediments including material property and cost issues to be overcome before its wide clinical applications.

This project proposes a novel alternative solution for an even faster and more cost effective method for the manufacture of personalised cranial plates by using the incremental sheet forming (ISF) technique. Our recent work has shown that a typically large size cranial plate can be made satisfactorily by using the ISF process in 7~8 minutes rather than hours or days. This outcome has considerable implications in potential technological advances and economic benefits as well as improvement to quality of life. In this project we aim to develop the new ISF based cranioplasty manufacturing technique, to design and build a bespoke desktop ISF machine for cranial reconstruction with full CT/MRI and CAD/CAM software integration and ISF process automation. By using the developed bespoke ISF machine, we will conduct a series of ISF benchmark testing and cranial reconstruction pre-clinical trials of 3 demonstration case studies using the developed bespoke ISF machine. The project will demonstrate its technical viability, economic benefit and potential improvement of quality of life. By the end of the project we aim to achieve up to 95% manufacturing lead time reduction with associated cost benefits as compared to the conventional methods. We also plan to show that the bespoke ISF machine can be used as a new and viable medical device for cranial manufacturing and there is a niche market place for speedy commercial exploitation.

Planned Impact

The proposed project outcomes will not only benefit the involved project partners but also relevant research communities in ISF and materials processing technologies, UK's high value manufacturing and healthcare technology providers and SMEs as well as cranial and maxillofacial prosthesis end users. The following outlines the key impacts of the project:

Contribution to knowledge creation: The proposed research will develop in-depth understanding of the material deformation and failure mechanisms for ISF based titanium cranial manufacturing and to establish optimised operational windows with given material, size and dimensions of a cranial plate. Important research results are also expected from developing novel ISF machine concepts and reconfigurable tooling solutions as well as new computational methods for CT/MRI based cranial shape reconstruction and CAD/CAM software integration and ISF machine hardware automation. Positive outcomes will not only make a contribution to knowledge in ISF focused research but also demonstrate its viability and suitability for cranioplasty and maxillofacial related applications.

Impact on UK's high value manufacturing: The development of the bespoke ISF machine will require the integration of CT/MRI and CAD/CAM programming and ISF process for the niche application of cranioplasty and maxillofacial prosthesis. Successful development of the bespoke ISF machine will bring a step change to the current practice of largely skill based craftsmanship process to an integrated process design, optimisation and manufacturing automation. The implementation of the bespoke ISF machine to cranioplasty surgery will enhance its affordability and usability by NHS and private hospitals. The change in the ways of cranial reconstruction will have considerable impact to the capability and competiveness of UK's high value manufacturing in the healthcare technology sector in lead time reduction and associated cost savings. The commercialisation of such a machine will allow UK's high value manufacturing technology providers and SMEs to explore technical innovation and develop new business opportunities in the niche market.

Impact on quality of life: Conventional methods of cranial manufacturing are time consuming due to the need for the design and manufacture of necessary tools and dies. As a specific example of commonly used press forming technique, a number of steps are necessary in the design and manufacture of male and female dies/moulds before actual forming of the cranial plates. Without the need for specific tooling and dies, the bespoke ISF machine can be deployed to make cranial plates in significantly shorter time and reduced cost. By using the developed bespoke ISF machine, it is envisaged that up to 95% lead time reduction could be achieved from currently 10~14 days to 2~4 hours. Such a lead time and associated cost reduction will have a considerable impact to the quality of life especially in situations where urgent cranioplasty surgeries are needed as suggested in UCL NHS hospital's Statements of Support.

Impact on training and skills: In close collaboration with all project partners, this project will allow the involved researchers to have the opportunity to understand the industrial need and the current and future challenges and to develop specialist knowledge, skills for innovative solutions in the interdisciplinary fields of high value manufacturing and healthcare technologies. The experience gained from R&D and dissemination activities of the project will play an important part for them to become future generation of research leaders.


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Chen F (2016) Fracture characteristics of PEEK at various stress triaxialities. in Journal of the mechanical behavior of biomedical materials

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Chen F (2015) Flow characteristics and intrinsic workability of IN718 superalloy in Materials Science and Engineering: A

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Chen F (2016) A constitutive model of polyether-ether-ketone (PEEK) in Journal of the Mechanical Behavior of Biomedical Materials

Description Since the start of the project in October 2015, we have made considerable progresses in the following areas:

1) We have conducted extensive incremental sheet forming (ISF) testing using both single point and double side based ISF methods for manufacturing titanium cranial plates. These ISF tests allowed us to evaluate the formability and quality of incrementally formed titanium sheets. The results confirmed the feasibility of ISF based approach for cranial implant manufacturing and its benefits in much improved lead time and reduced cost.

2) We have developed and validated a modified Gurson-Tvergaard-Needleman (GTN) model, a micromechanics based damage model for the prediction of fracture in incremental sheet forming. It can be used as an essential tool for establishing optimum ISF processing windows for cranial implants.

3) We have developed a prototype cranial reconstruction and ISF process design software system that can be used to reconstruct cranial shape from CT/MRI data and to generate ISF tool path for ISF processing. Further development of this software system would ensure integrated design and rapid ISF manufacturing of cranial implants.

4) We have been successful in securing additional funding through the EPSRC Centre for Innovative Manufacturing in Medical Devices (EP/K029592/1) MeDe Fresh Idea fund in developing ISF process for manufacturing PEEK based cranial implants. A novel heat-assisted ISF device has now been developed with successful trials to form PEEK cranial plates.

5) Since the start of the EPSRC project, we have collaborated closely with our project partners in delivering the targeted research outcomes. In particular, we collaborated with Shanghai Jiaotong University in investigating the fundamental aspects of ISF and in developing the prototype software system. We collaborated with the Cranioplasty Unit, UCL in completing a pre-clinical case study of ISF based cranial implant manufacturing. We have been collaborating with University of Bournemouth in developing an Ordinary Differentiation Equation based approach for fast cranial shape reconstruction with promising initial results obtained.

6) In this reporting period, we published 27 articles in international journals (including 6 papers presented in international conferences) with an additional journal paper accepted for publication.

7) In September 2019, we were awarded by a Universtiy EPSRC Impact Acceleration Award (Impact Exploration Grant) with an amount of £7,358 award. The aim of this small grant is to carry out a market search for the need of affordable manufacturing of cranioplasty implant using flexible forming based technique and to engage with NHS hospitals and clinicians for possible pre-clinic case studies for possible clinic applications.

8) Janurary 2020, we have been successful in securing an EPSRC Future Composites Manufacturing Hub's Fleasibility Study Award, Incremental sheet forming of fibre reinforced thermoplastic composites (£49,651). The aim of this project is to investigate the feasibility and to explore the potential to incorporate incremental sheet forming and conventional thermoplastic moulding techniques as a new hybrid approach for manufacturing fibre reinforced thermoplastic composites for wide industrial applications.
Exploitation Route We are now working with Clinical Engineering at Nottingham University NHS Hospitals to develop a plan for more pre-clinical and potenially clinical trials of the ISF based approach form cranioplasty so we can fully assess its impact in patient experiences, cost and efficiency as compared with existing technologies for cranioplasty manufacturing.
Sectors Aerospace, Defence and Marine,Healthcare,Manufacturing, including Industrial Biotechology,Transport

Description Advisory board of NNUMAN (New Nuclear Manufacturing) Programme
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
Description EPSRC Peer College
Geographic Reach National 
Policy Influence Type Membership of a guideline committee
Impact To ensure high quality research that leads to impact.
Description Advanex Europe Ltd and Nottingham KTP partnership
Amount £151,800 (GBP)
Funding ID 510934 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 10/2017 
End 09/2019
Description EPSRC MeDe Fresh Ideas Fund
Amount £49,768 (GBP)
Funding ID EPSRC (EP/K029592/1) 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 06/2015 
End 05/2016
Description BU 
Organisation Bournemouth University
Department The National Centre for Computer Animation (NCAA)
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaboration has brought a new area of research to the project partner
Collaborator Contribution The collaboration with the project partner has produced promising results in using an ordinary differentiation equation (ODE) based approach for fast cranial shape reconstruction.
Impact Positive results have been obtained in using the ODE based approach for cranial shape reconstruction.
Start Year 2015
Description Delcam 
Organisation Delcam International
Country United Kingdom 
Sector Private 
PI Contribution Contribution to this collaboration has yet to be achieved.
Collaborator Contribution Contribution from the project partner has yet to be achieved.
Impact Direct outcomes from this collaboration have yet to be achieved.
Start Year 2016
Description Labman 
Organisation Labman Automation
Country United Kingdom 
Sector Private 
PI Contribution Close collaboration and contribution to the project partner has yet to start.
Collaborator Contribution Close collaboration and contribution by the project partner has yet to be achieved.
Impact Direct collaboration outcomes with this project partner have yet to be achieved.
Start Year 2016
Description SJTU 
Organisation Shanghai Jiao Tong University
Country China 
Sector Academic/University 
PI Contribution Contribution has been made in supporting the project partner's on-going work in ISF related research.
Collaborator Contribution Contribution has been made in developing new forms of ISF processes and in developing the prototype software system.
Impact The collaboration with the project partner has resulted in significant number of joint publications and development of the prototype software system.
Start Year 2015
Description UCL 
Organisation University College London
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaboration has made a contribution for the project partner with promising results of using ISF to manufacture cranial implants as an alternative route for cranioplasty.
Collaborator Contribution The project partner has made an important contribution in giving clinical advice in cranioplasty manufacturing and in providing a pre-clinical case study for cranial reconstruction and manufacturing using ISF technique.
Impact The on-going collaboration has resulted in a successful pre-clinical case study of ISF based manufacturing of cranial implant.
Start Year 2015
Title Cranial reconstruction for ISF 
Description This is a prototype software system that enables automated cranial shape reconstruction and ISF process design for ISF based manufacturing of cranial implants. 
Type Of Technology Software 
Year Produced 2015 
Impact This is a prototype software system, which needs further development for more advanced functionality and testing before its full implementation in clinical trials. 
Description Organisation of two special sessions in two international conferences (SheMet 2015 and ICNFT2015) as part of an EC Marire-Curie IRSES project 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact These special international conference sessions were organised to disseminate our research outcomes and encourage communication and connections of international researchers who are involved in flexible sheet forming focused research.
Year(s) Of Engagement Activity 2015