Zircon oxide is an unusual material and convinces with its extraordinary characteristics such as high flectional strength (up to 1000Mpa), hardness (up to HV 10=11-12,5Gpa) as well as its corrosion resistance. Industrially, various products can already be produced , for example; kitchen knifes and cutting tools. For parts that are subject to thermo-mechanical strain, the automobile-, aviation- or steel industry also resorted to this material. Next to its physical properties, zircon oxide is bio-compatible. Therefore, it is also suitable for the medical technology (endoprophesis) and dentistry (dental crowns, implants etc.). Zircon oxide is regenerated as raw material in powder form and compacted under pressure into a green part (for example: dental ceramics).

In a subsequent heating process, the green part either obtains a basic solidity or the required physical properties. After the so-called presinter process (approx. 1100°C), a mechanical treatment of the green part is possible, however, only through the final sinter process (approx. 1700°C) the highest mechanical firmness can be achieved.

In a milling process, various shapes can be created out of the pre-sintered green part such as dental- fillings, crowns- or bridges. From this process derives the term ‘milling ceramics’. During the final sinter process the treated zirconium is subject to a shrinkage of about 20%. The shrinkage factor is pre-calculated as fixed size before the treatment of the ceramic material so that the treated zircon oxide part corresponds to the required measurements after sintering. Here, it is absolutely necessary to set the density in the green part in tight ranges in order to gain an even shrinkage in the entire press body.

The disadvantage of this method is the fact, that the green part does not show a precise dimensional accuracy. The cause for this circumstance is the unevenness in the flexible press form as well as differences in the bulk density of the powder which leads to a sagging in the green part surface. This means for the milling ceramics, that the reference surface must be restored through a mechanical refinishing process. This processing step as well as the costs for pre- and re-finishing treatment, by filling of the powder and removal of the green part out of the press form, have a disadvantage compared to other production methods. In addition, many processing steps are very expensive due to personnel- and time expenditure, because the latitude for automation is rather limited.

A manufacturer of zircon oxide parts for the dental ceramics contacted us with the request to conduct a feasibility study for the production of green parts by means of axial pressing.

Objective was, to produce saleable milling ceramics with homogeneous density and finished dimensions with the specific goal to increase the productivity significantly. After intensive testing, under consideration of tooling, development of suitable fill device, construction of a sensible sensor technology, and the ideal press program, the feasibility of KOMAGE-press systems were demonstrated. In a four-hour production cycle on the KOMAGE press, as many green parts were presses as with an isostatic press in a week.

For our customers this economical advantage was a clear and conclusive argument:

“saleable products with homogeneous density and high productivity – without any after-treatment!”