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Bulk molding compound / sheet molding compound
Rotec uses SMC or BMC technology essentially for the production of Backing Rings (Loose Flanges) in diameters 10 through 400 mm.
Compression moulding using SMC is a high-volume process that employs expensive but very durable steel moulds. Sheet moulding compound (SMC), is a composite sheet material made by sandwiching chopped fiberglass between two layers of thick resin paste. The SMC is cut into smaller sheets and is assembled (specific dimensions and number of layers) on a heated mould. The mould is closed and clamped, and 30 to 80 bar pressure is applied. Material viscosity drops and the SMC flows to fill the mould cavity. After cure, the mould is opened and the part is removed.
BMC is a dough like material (often referred to as DMC rather than BMC) which combines the resin and chopped fiberglass in a random manner. Moulds and moulding technologies are similar to those required for SMC. Both materials may contain not only glass reinforcement and resin, but also, depending upon the application, various additives such as fillers, shrink control agents, pigments and curing agents.
It is important top note that Rotec does not mould the holes in any type of flange but drills the flanges after production. When moulding the flanges with holes the resin tends to separate from the fiberglass reinforcement in the immediate area around the hole with a resulting low glass content and subsequent weakness at this crucial point.