Scientific and technical know-how for the deposition of FGM materials on the inner surface of an outer electrode was established. A new EPD technique was developed for depositing on the inner surface of an outer electrode. This was done because the main problem with deposition on an inner electrode is that the deposit has to be removed from the electrode after EPD and this has to be done without damaging. In normal atmospheric conditions, the deposit dries very quickly due to the fast evaporation of acetone, shrinks and causes cracking.
When depositing on the inner surface of an outer electrode, the outer cylinder, on which the powder is deposited, is closed at the bottom. The deposit will shrink during drying towards the centre electrode, thus away from the deposition electrode. Hence, cracking of the deposit during drying is easier to control since the deposit can shrink freely. Moreover, it is possible with this technique to produce a deposit without inner hole, by moving the inner electrode upward during EPD.
In order to upscale this technique to produce rods with a sintered length of 100mm (needed for drill blanks) a 3-D rigid positioning device was constructed. In this way, the vertical positioning and displacement of the electrode can be controlled very precisely. This device enables to control the vertical displacement of the electrode, maintaining an excellent alignment between inner and outer electrodes. Moreover, an electrode displacement of 15cm is possible. Within the constraints of the project defect free sintered rods up to 50mm in length were produced using this technique.