The Solid Cast Polyurethane (PU) manufacturing process is widely preferred as the material of choice in applications where a high degree of load bearing, abrasion resistance and tear strength is important.
RIM (reaction injection molding) is widely preferred as the process of choice for applications such as automobile bumpers and panels as well as interior parts like dashboards and armrests. RIM is a popular production process in light duty industrial manufacturing due to the ease of production and reduction in raw material usage. However for heavy industrial applications RIM products do not have the strength and resistance of solid cast manufactured products.
RIM processes produce esthetically pleasing products, however, their durability and resistance to wear and tear is well behind solid cast products. Although similar materials are used in both processes, the cellular nature of RIM products, wherein, air is added to create the “reaction”, substantially reduce the ability of RIM products to withstand the rigors that cableguards and dropovers are subjected to in normal use.
If one were to cut open a RIM created product, it would look similar to a piece of Swiss cheese. There would be holes in the product due to air being introduced into the casting. Whereas a solid casted product does not have this quality and the end product is a more solid, dense part which has greater load bearing and tear strength.