First, the bond components and abrasives are mixed and filled into a mold, either by a casting process in the case of clayey bonds or by a molding process (Fig. 3.11). Pressing compacts the material and produces the so-called “green body” which can be handled. The green body is dried and sintered. After that, the grinding wheel will be finished and undergoes quality control.
The proportion of grit, bond and pore volume defines the structure and hardness of a grinding tool (see Sect. 6.1 “Abrasive Layer Composition”). The right amount of bond components and grits are weighted and mixed. Even if the various ingredients have different size, density, form, and weight it has to be controlled that the mixture is homogenous and without agglomerations, so that the final abrasive tool has a homogeneous cutting edge distribution [BOTS05, p. 23]. Furthermore, the mixing process must not demix the components, induce changes in the mixture, or produce heat [TYRO03].
In the first step, the coarse particles are made sticky by mixing them in for example a water dextrose solution [MESP91, TYRO03]. The fine components are added afterwards and stick to the prepared coarse components [MESP91, TYRO03].
The lubrication has to be controlled to avoid aggregation [BOTS05, p. 23]. Aqueous phenolic resin binders are one example for temporary binders [HUZI00].
A common mixer type is the planetary mixer [MESP91]. As ingredients might change their viscosity and react chemically during this process an adequate mixing time is also of great importance [MESP91]. Standard mixing times of up to one hour are therefore quite common. To enhance tool quality, vitrified bondings can be granulated and sieved after mixing.