Social Icons


Friday, September 3, 2010

Sheet Moulding Compounds (SMC)

SMC is a combination of chopped glass strands and filled polyester resin, in the form of a sheet. Processing of SMC by compression or injection moulding enables the production of bodywork or structural automotive components, and electrical or electronic machine housings in large industrial volumes. The process also penetrates sectors such as sanitary ware (baths) and urban furniture (stadium and cinema seating), etc.

The prepreg contains all the components needed for moulding the final part (resin, reinforcement, filler, catalyst, low profile additives, etc.) in a malleable and non-tacky sheet. Its characteristics allow it to fill a mould under the conditions of moulding temperature and pressure employed.

SMC prepreg is made from glass strands chopped to lengths of 25 or 50mm, sandwiched between two layers of film, onto which the resin paste has already been applied. The prepreg passes through a compaction system that ensures complete strand impregnation before being wound into rolls. These are stored for a few days before moulding, to allow the prepreg to thicken to a mouldable viscosity.

The main process for moulding SMC material is Compression moulding. The film is stripped off and the material is cut into suitable pieces. These are collated into piles of material, which are called the charge. This is positioning in the mould tool. Heated moulds are used and a compression pressure is applied. The base resin being a thermosetting material cures and
hardens. The part is ejected. Any flash is trimmed by the operator.

SMC Manufacturing