| Rotational molding or rotomolding is a relatively slow process that is capable of making large one-piece hollow plastic objects at a cost lower than most other plastic molding processes.
The rotational molding process starts with a closed split mold. The molding compound, usually a thermoplastic in the form of pellets or granules, is pre-measured and loaded into the molding chamber. The chamber is then sealed and mounted on a multi-axial rotation station. The chamber is heated and the compound inside is melted. Preferably, the molten material has low viscosity and can be distributed easily. The rotation station begins to rotate slowly on multiple axes simultaneously such that the molten material is evenly coated on the internal surfaces of the mold while the temperature continues to drop in a controlled manner. The rotation and cooling continue until the molding compound solidifies. The mold can then be opened and the finished part is released.
The rotational speeds, heating and cooling rates need to be carefully controlled throughout the process. Unlike other common plastic molding methods, such as injection, extrusion, and compression moldings, there is no external pressure applied during the entire molding process. Again, this is a very slow process and each cycle usually takes about an hour or more.
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- One-piece product design reduces or eliminates assembly cost.
- Allows complex mold split lines.
- Allows molded threads and mold-in inserts.
- Allows a wide range of surface finishes (textured, smooth, or polished).
- Very little waste in material.
- Low residual stresses. There are thermal stresses during the cooling process but (almost) no forming stresses because no external pressure is ever applied.
- Tooling is less expensive. Due to its low pressure operation, the wall thickness of the molding chamber can be thinner than those for other molding methods.
- Suitable for both low-volume prototypes and high-volume production runs.
- Slow production speed. It usually takes about one hour to finish a cycle, as opposed to just a few seconds for a typical injection molding process.
- Lower precision.
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ReplyDeleteOnce the plastic has been molded, it is cooled completely. Once the cooling is complete, the rotomolded product can be easily removed. This is a critical step in the manufacturing process. You also may find your ideal details about molds for rotational molding on www.grangerplastics.com.
ReplyDeleteThermoforming Machine is the machine which uses the Thermoforming Process to produce smaller plastics objects. The plastic used to make objects is stretched over a mould using vacuum.
ReplyDelete