The precision with which the raw materials are fed into the weighing containers is largely responsible for the accuracy of the weighing itself and therefore for the maintenance of the tolerances specified in the batch recipe. The dosing equipment is specially chosen to suit the specific flow characteristics of each material. At the end of the dosing cycle special dosing screw feeders ensure that the specified dosing quantity is achieved exactly and there is no overrun.
The scales themselves are chosen according to the quantity of material to be weighed and the accuracy required. In most cases the weighing takes place in fixed containers fitted with industrial load cells. Dosing and analysis of the weighing data is carried out in the PLC utilising electronic weighing processors freely available on the open market. A metering band scale may also be used for particular raw materials. High precision systems have been developed for weighing minor components.
Effective batch mixing is of vital importance to the melting process. Best glass quality can only be achieved in the melter when the batch has the necessary homogeneity. Various mechanical mixers from a number of manufacturers are used, depending on the specific requirement. EME has developed a pneumatic mixer for use with very fine raw materials, which makes it possible to obtain excellent homogeneity with these materials without a dusting problem.