In final thesis, the passage from two cavity to four cavity injection mold is presented for injection molding of protective board, which is used for protecting hydraulic valve from intrusion of dirt and is disposed when mounted. Due to the overuse of the two cavity injection mold and the needs of the contracting authority to lower the costs of the production, the passage from two cavity to four cavity injection mold was performed. The construction of the injection mold was already determined. In my thesis, I tried to determine technological parameters of injection molding and impact of the individual parameter on the quality of the product. The experiment was performed on the machine Argurb 350-90-270D. On the basis of theory and theoretical calculations for the used material (polyethylene), the construction of injection mould and practical experiments, I determined optimal parameters of injection molding. The chosen optimal parameters of injection molding partially deviated from theoretical calculations. Pressure and closing force had the biggest impact on the choice of the optimal parameters. According to results, all four pieces comply with the demands of the contracting authority. Due to the fact, that, with the optimal parameters, described in this thesis, the productivity was increased for about 67 %, the lowering of the price is possible in the following steps.
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