Plant layout for the process

A typical design of such a unit is shown in Fig. 4.44. According to this method, the start and finish of mixing and, consequently, the time of feeding the mold are exactly determined by the location 

The molds in a RIM-process plant are located in a separate assembly, which has devices for opening and clamping a mold and, in some cases, for changing it. The pressure in the RIM-process is considerably lower than in traditional injection molding of thermoplastics thus, the requirements for the mold material are less rigid. Molds may be made from aluminum or reinforced plastics, since high-strength steel is not necessary. 

Removal of the article from the mold is lengthy process because anti-adhesive lubricants have to be sprayed on the on a mold surface before every injection, in an operation that takes up to 25 - 30% of the full cycle. In reactive molding of polyurethane-based compounds, internal lubricants are used in combination with surface coatings. This allows us to remove articles from a mold many times with a single coating treatment. One of the compounds used as an internal lubricant is silicon-organic liquids. 

Molding plants are universal and can be used for processing a wide range of materials, including polyamides, polyurethanes, epoxy resins, and other RIM-formulations. To give some idea of the technical capabilities of RIM-machines main technological features of a Krauss-Maffei (Germany) unit, known as NBC-RIM-s/ar-40 machine, are listed below. 

This installation is built on the modular principle. Component output is measured by a gear counter, and there are various possibilities for programming the operating cycle of the unit. 

---