MANUFACTURING OF RUBBER MOLDINGS ORIENTED TO QUALITIES - MATERIAL - MOLDING - PROCESS

Increased quality requirements and a growing cost pressure are forcing Producers to manufacture to increasingly tight tolerances. This trend has Progressed right through to the mixing room with the development of different kneader control units. Two control concepts derived on this basis are Presented in this paper. The viscosity control concept is designed to smooth ot fluctuations in raw materials, particularly in the case of NR. Results, obtained on a laboratory and production scale, showed that the viscosity can bs kept within tight tolerances by this control system. The second concept makes a contribution towards increasing reproducibility by controlling the movements of the floating weight. In the processing of crosslinking moulding compounds the chemical reactions that take place are frequently a function of the temperature history. The temperature distribution itself is inhomogeneous over time and over the location of the geometry. The lack of knowledge about the process sequence frequently leads to shortcomings in production. A new numerical process is presented which, is seen to be extraordinary flexible in response of the chemical processes, that can be described, and their effect on the heat balance in the moulded part. In this way it is possible to establish heating times precisely and to optimise the thermal relationships in the mould. The injection moulding of high-quality elastomer parts requires a precise layout of the mould in rheological and thermal terms and also requires allowance for the reaction kinetics of the moulding compound. The CAD-MOULD-3D program system and the MESTRO-E stream line module can supply the data required for this. With the aid of this software, problem areas within components - such as welding lines and the strengths of these welding lines - can be precisely analysed and correlated with practical measurements, so that the welding line strength in other components can be estimated. Industry is currently endeavouring to have the quality inspection of finished parts, which is still a necessity today, replaced by the control of process parameters during moulded part production. In the context of this fourth section, an approach is presented, which makes it possible for statements to be made on the quality of moulded parts right at the production stage. The principle of the statistical method of experimentation is applied. This permits information to be obtained about the process being studied on a systematic basis and with a calculable outlay. Process data and quality characteristics are established, employing a statistical experiment design, and during evaluation, statistical process models are generated, which correlate the process parameters and the moulded part properties.