This article introduces several limitations of rotomolding technique in detail.
1. Large energy consumption. The mould must be repeatedly subjected to alternatively changing temperature during the rotomoling cycles, so in general, the rotomolding process need more energy than other related process. In order to save energy, the jacketed rotomolding machine has been developed. The machine can directly heat or cool the material and reduce the energy consumption during the processing. However, the mold is still repeatedly subjected to the changing temperature and the energy consumption is still large.
2. Long processing cycle. During the process, the material is not withstand the strong external force and doesn’t go through the intense turbulent motion; the material is merely relying on the cavity surface of the mold. After the cavity surface is covered with molten plastic coating, the inner temperature will increase; the required heat will be transmitted through thermal conductivity. The thermal conductivity of the plastics is poor, therefore, the time of heating for rotomolding is quite long, usually need ten or twenty minutes or more, thus the processing cycle is long.
3. Great labor intensity. It is hard to realize mechanization and automation during the rotomolding process, usually need labors to finish the process; therefore, the rotomolding need more labor than other related process.
4. Less accurate dimensions of products. Besides the material, dimensions of rotomolding products are affected by other factors, such as the speed of cooling and the type and amount of release agent etc. Therefore, the accuracy of rotomolding products is difficult to control, and the rotomolding technique only can be applied in products like containers and toys, articles that have no special requirements for the dimensional accuracy.
