PhD Programmes within the main programme

As part of the Metal Printing SIP we aim at educating 3 PhD candidates in different professional disciplines at NTNU; Powder metallurgy, production engineering, and electrostatics. Our strategy is to include the PhD candidates as participants of the research team of the appurtenant work packages. Consequently, the PhDs will be able to develop a close relevance to the SIP as a whole, and the researchers may benefit from the intensive work that a PhD work implies. The PhD candidates will be localised nearby the research team they participate in. A brief introduction to the 3 PhD programs follows:

Powder metallurgy science
The metal printing process shall ideally produce a dense component with full structural integrity in a short time. This will require a very efficient sintering process that will give a high density within less than a second. The sintering process should ideally work for both metallic and ceramic powders of different compositions. It is not known whether such a process exists. A PhD program will therefore be directed towards this problem. The goal of this PhD program is to give a theoretical and experimental basis for the selection of an optimal sintering process for metal printing.

The program will include a literature survey of different sintering processes and sintering mechanisms with particular emphasis on rapid sintering. Different sintering processes like electric contact sintering, liquid phase sintering and plasma spark sintering will be studied, both theoretically and experimentally in order to elucidate if thin layers can be sintered within short times. The influence of powder composition and process parameters, such as layer thickness, powder size distribution, temperature etc will be investigated. The program will be conducted in close co-operation with the other activities within the SIP program.

Production engineering
At NTNU in 1994, a basic R&D has been started developing the unique Metal Printing Process (MPP), which resulted in the PhD thesis of Bakkelund [4] and Karlsen [2] and several other publications. Seen from the recent state of the art, the MPP is ranking as a world-class manufacturing technology [3]. The PhD programme is aimed to get this approach from the laboratory phase moved over to industrially usable implementations. That also makes a more abstract modelling and optimisation of the entire production engineering process chain necessary.

In close co-operation with the on-going research work at SINTEF the PhD programme is intended to provide suggestions and realisations for process modelling & optimisation of the entire process chain. Subtasks of current interest may be:

Develop a working pilot solution (demonstrator) for the MPP, which unites the two process steps (layer fabrication, layer consolidation) into one single system with computer support for process control and automation.
Powder particle morphology and size investigations for stair-stepping effect investigations and accuracy improvements
Pressure control system development
Costs/benefit analysis
User-friendly process organisation
Computer-aided control operation system assuring repeatability, experience-based process optimisation and self-optimising quality control loops

Electrostatics and power supplies
As discovered in previous PhD studies, an accurate deposition of powder is difficult for various types of powder used simultaneously. This PhD programme should therefor focus on optimal design of the electrostatic part of the machine. Furthermore, a study of a better power supply for the sintering process is needed. Depending on the properties of the materials to be used the method of heating and pressing may have to be shifted, and variable power-frequency-voltage must be evaluated. The study must take in to consideration the effect on the sintering process from the deposition automation and effective support generation by the deposition of different powders in one layer under avoiding the mutual contamination. This also includes the effect of different power supplies and electrostatic fields on the layer shape (edge) accuracy. Improving investigations on particle placements under gravity and electrostatic forces during the deposition and sintering phase should be included.