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FP7

HIRESEBM Report Summary

Project ID: 286762
Funded under: FP7-SME
Country: Sweden

Final Report Summary - HIRESEBM (High resolution electron beam melting)

Executive Summary:
The HiResEBM project was a partnership between EU SMEs and RTD providers with the aim of developing an electron beam melting (EBM) additive manufacturing process to enable the fabrication of high resolution medical implants with optimised porous structures directly from metal powder.
Currently the design of some medical implants with porous structures is limited by production technologies not being able to implement complex 3D structures with high enough resolution of the porous structure.
These complex structures are used to improve the initial fixation strength and the long term osteointegration properties of implants which lead to better quality of life for the patients. However, many patients undergo revision surgery within five years of receiving the original implant.

Project Context and Objectives:
HiResEBM was a partnership between EU SMEs and RTD providers with the aim of developing an electron beam melting (EBM) additive manufacturing process to enable the fabrication of high resolution medical implants with optimised porous structures directly from metal powder, nominally titanium Grade 5 and CoCr steels.
The objective of HiResEBM was to produce an efficient manufacturing process that will allow any designed porosity to be incorporated into any part of an implant – giving complete freedom to design the ‘optimum’ implant. The consortium was composed of several companies with resources and experiences in different fields relating to the technical barriers to be overcome during the project, such as:
• Expertise in electron beam gun design, to produce a new high precision EBM system.
• R&D experience in additive manufacturing with fine powders.
• Coating processes used for the medical implant market.
The ever increasing mean population age and the prevalence of degenerative bone diseases means that the demand for implants is going to increase significantly and place an even greater burden on our EU health care systems.
By introducing new manufacturing technology and improving the revision rates it was calculated that savings of the order of 240M Euro a year are possible.
Current EBM systems are capable of producing thousands of parts per year and are able to recycle unused powder for further processing.
Currently the design of medical implants with porous structures is limited by current production technologies inability to implement complex 3D structures. These complex structures are used to improve the initial fixation strength and the long term bone ingrowth (osseointegration) properties of implants which lead to better quality of life for the patients. However, many patients undergo revision surgery within five years of receiving the original implant, due to loosening of the implant in the bone due to osteolysis.
In order to improve longevity of the joints between implants and bones it is necessary to encourage (osseointegration) into the implant, which can be achieved by creating porous fine scale 3D features on the implant, thus making a joint which will last much longer. While this approach is widely adopted in implants there were two key barriers limiting the effectiveness of this approach:
1 Limitations of existing manufacturing techniques do not allow the optimum porous surface to be incorporated into implant(s).
2 Current production methods for the best attempt at porous surface structures are inefficient and thus economically less attractive.
HiResEBM aimed to overcome these two barriers by:
“Developing an efficient manufacturing process that allowed any designed porosity to be incorporated into any part of an implant – giving complete freedom to design the “optimum implant”.”
The improved implant was manufactured by direct layer-by-layer fabrication from powder form by developing a process known as additive manufacturing. This was based on an existing electron beam fabrication system made by Arcam. This system was already used to manufacture implants such as acetabular cups. However, in order to deliver an optimised porous structure for the next generation of implants, the resolution of features needed to be improved as well as the surface finish.

Project Results:
The project was split into different work packages each aimed at fulfilling one or more of the projects objectives. Initial work packages are aimed at delivering the scientific objectives. Other work packages are focussed on developing strategies for dissemination of results and protection of foreground IP.
Initial work on the design of the new high intensity electron beam gun electrodes and gun column was performed by TWI Ltd. During the kick-off meeting the objectives for the project processing capability were clarified along with the requirements for intensity and working distance. In liaison with Arcam and Sparks the gun column requirements for electrical and mechanical connections was specified and the physical envelope of the gun column was also detailed. The system was specified at an acceleration potential of 60kV with a maximum power of 3kW. Following agreement of the specification, Sparks undertook manufacture of the high voltage power supply unit which was delivered for test at TWI on 15/01/2012.
Initial work was focussed on validating a model which was built of the existing electron gun used by Arcam in their EBM system. The model was built in Cobham’s Opera 2D and 3D analysis software.
Beam parameter characterisation tools were built up in the Opera program as scripts so that quantitative comparison of the beam qualities could be made. The 2D software was then used to model the design over the operating range of power, and different gun settings. New gun designs have been analysed in Opera 2D software and the beams generated by the models have been assessed using the beam characterisation tools developed.
Different geometries have been explored to provide a robust gun electrode design that can operate over the widest range of beam powers (0-3kW). Lenses and deflection coils which form the magnetic electron optics of the gun column were assessed through a combination of mathematical models of the optics, combined with magnetic finite element analysis provided by the Opera software suite (both 3D and 2D). TWI have, by using 3D FEA, analysed the current deflection coil design and have developed the measurement techniques to assess its performance. FEA modelling of the deflection coils was performed to minimise introduced beam aberration. Within this model it was also possible to derive the inductance of the coils and this was used to ensure a design development that can operate at high deflection frequencies with improved positional accuracy eg better than half the beam diameter.

Work on the selection and characterisation of new fine titanium powder was performed by AIMME.
A system which uses finer powder is required to reach the fine net structures of interest for medical use.
An initial study of commercially available powders was performed to identify an appropriate powder size and initial properties.
The study was focused on two types of Ti-6Al-4V: gas atomized (GA) and plasma atomized (PA) powder, both with a powder size distribution between 25 and 45 μm.
The first deliverable D2.1 for this work package was the establishment of safety protocols for fine powder handling. This specifies the protocols for storage, handling, and use of fine Ti-6Al-4V powder with a powder size distribution between 25 and 45 micrometres. It also specifies all safety issues such as hazard identification, first aid measures, handling and storage, operating clothing and equipment recommendations, etc.

The second deliverable, D2.2 “Evaluation of fine powder”, included all powder testing outside the EBM system. The powder was characterised from the point of view of chemical composition, size of fractions, flow, apparent density, morphology, and a metallographic study. Following the study an appropriate powder size distribution (25-45mm) was chosen to promote to the next stages of the research.
The modified powder delivery system (PDS) was development including testing of different variants of the PDS. The main objective is to improve the density of packed powder and the flatness of powder distributed over the build plate during each session of powder delivery. These two factors were principal indicators of good powder distribution both in cold powder distribution and in sintered powder after preheating. To achieve these aims, different solutions were tested until the end of work package two.
The project has developed a new prototype electron gun and a new prototype powder distribution system. The prototype electron gun did not sufficiently fulfil the demands for the project so instead a modified Arcam Q10 system was used to carry out the processing tests.
Processing trials of implant prototypes with higher resolution has been performed with promising results.
The project has also produced results that have resulted in new IP-protection of EBM technology.

Potential Impact:
The development of the high-resolution EBM system and the implementation of the HiResEBM project results can be used to create a new manufacturing method, to utilise optimised bone ingrowth structures. The HiResEBM project will result in improved implant performance – reducing the trend for requiring multiple surgeries, without significantly increasing cost to the health authority or patient.
Also the ever increasing mean population age, and the prevalence of degenerative bone diseases, means that the demand for implants is going to increase significantly and place an even greater burden on our EU health care systems.
Essentially the HiResEBM project aimed to develop a new manufacturing facility that has the potential to significantly reduce costs and lead to better quality of life for patients.
The project will lead to faster introduction of Additive Manufacturing equipment and processes for high resolution manufacturing of implants with trabecular structures. This will impact the possibility to improve on production of advanced implants with good osseointegration for longer lifetime in patients. It also has the potential of reducing the cost of such implants.

List of Websites:
The project website (www.hiresebm.eu) was kept up to date with information exchanged by the partners, in the partner only area.

Related information

Reported by

ARCAM AB
Sweden
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