In-situ process monitoring during the Selective Laser Melted Ti-6Al-4V porous biomaterials

by Professor Denis Dowling, Director, I-Form Advanced Manufacturing Research Centre, University College Dublin

Selective Laser Melting (SLM) allows for the creation of complex cellular structures, that possess favourable biological properties, these structures are known as porous biomaterials.

This presentation will provide an overview of the printing of cellular Ti-6Al-4V structures, using a production scale SLM system (Renishaw 500M).

During printing, in-situ process monitoring was carried out based on the use of photodiode (PD) measurements. These were used to obtain information relating to both the meltpool and the operational behavior of the laser. An advanced scanning technique was used to produce the cellular structures, whereby the laser processing parameters determined the strut dimensions.

In this study, the laser input energy was reduced by 33, 66 and 100%, at specific layers, within the cellular structures. It was demonstrated that both as the level of laser energy was decreased and / or the number of effected layers increased, there was a corresponding decrease in the load bearing strength of the porous structures.

Data generated based on the PD measurements during the processing of these structures was also compared to a data generated during the processing of control structures, for which there had been no decrease in laser energy.

A correlation was demonstrated between the reduction in load bearing strength of the structures and the difference between the control data’s and the build data’s PD signals. Indicating that through comparing build data to control data, valuable information relating to the structural integrity of the parts could be determined.

Interestingly, it was demonstrated that where no input energy was applied for 3 print layers, the cellular structures were still build successfully, albeit with a 33% reduction in compressive strength, compared to that obtained for the control structures.



What drives you?
Interest in finding out new things, in understanding them and where possible in translation them into a product or process.

Why should the delegate attend your presentation?
To find out how in-process monitoring can be successfully applied during the printing of metal alloys.

What emerging technologies/trends do you see as having the greatest potential in the short and long run?
Reliable methods of process monitoring combined with printed part performance data can facilitate process control.

What kind of impact do you expect them to have?
The ability to obtain in-process data in conjunction with data analysis, can hopefully help to facilitate the development of predictive process control techniques for additive manufacturing processes.

What are the barriers that might stand in the way?
Each printing process requires a deep understanding of the interaction between the processing conditions and resulting part performance. It thus requires a considerable effort to understand the ‘safe’ processing window for the production of high quality parts by additive manufacturing.

“Special quote”
The monitoring and control of additive manufacturing processes is critical for their wider adoption of this technology for the fabrication of medical devices.

About Denis Dowling

Denis has over 30 years’ experience in working in all aspects of materials science. He is the director of the I-Form Advanced Manufacturing Research Centre, who’s focus is on research into the application of digital technologies to materials processing. Denis specialist areas of interest are in additive manufacturing and in the plasma surface modification of materials. He has published over 180 papers in peer reviewed journals. Prior to joining University College Dublin, Denis worked in a state development agency called Enterprise Ireland. In addition to research activities he acted as a consultant assisting companies to develop their R&D activities.

About I-Form Advanced Manufacturing Research Centre, University College Dublin

University College Dublin is one of Europe’s leading research-intensive universities. At UCD undergraduate education, master’s and PhD training, research, innovation and community engagement form a dynamic spectrum of activity.

Today UCD is Ireland’s largest and most diverse university with over 30,000 students, drawn from approximately 124 countries. It actively promotes university life as a journey of intellectual and personal discovery through its highly innovative and flexible UCD Horizons undergraduate curriculum and is the most popular destination for Irish school-leavers.

UCD is Ireland’s leader in graduate education with approximately 7,000 graduate students, and almost 2,000 PhD students. Over 50% of UCD undergraduates progress to graduate studies.

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