Compression molding is a high-volume process that employs expensive but very durable metal dies. It is an appropriate choice when production quantities exceed 10,000 parts. As many as 200,000 parts can be turned out on a set of forged steel dies, using sheet molding compound (SMC), a composite sheet material made by sandwiching chopped fiberglass between two layers of thick resin paste. To form the sheet, the resin paste transfers from a metering device onto a moving film carrier. Chopped glass fibers drop onto the paste, and a second film carrier places another layer of resin on top of the glass. Rollers compact the sheet to saturate the glass with resin and squeeze out entrapped air. The resin paste initially is the consistency of molasses (between 20,000 cps and 40,000 cps); over the next three to five days, its viscosity increases and the sheet becomes leather-like (about 25 million cps), ideal for molding.
Often identified with automotive body applications, sheet molding compound shows growing promise in a variety of other temperature- and weather-resistant applications.
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Resin specialist Cytec Industrial Materials develops a styrene-free vinyl ester for use by Continental Structural Plastics (CSP) in the manufacture of a compression-molded battery tray for the Chevrolet Spark electric car.Hybrid carbon fiber/glass fiber reinforcement Composites Technology
Quantum Composites has introduced its first hybrid carbon fiber/glass fiber material, suitable for compression molding in automotive, heavy truck, medical, sporting goods and industrial applications.Pinette to supply composites manufacturing system to Canadian center Composites Technology
France-based Pinette Emidecau Industries will supply a compression molding machine for research and development work at the National Research Council in Boucherville, Quebec, Canada.Dieffenbacher installs preform technology at Fraunhofer facility Composites Technology
The Dieffenbacher Preform Center will be installed at the Canada-based Fraunhofer Project Center and used to help develop carbon fiber composite structures manufactured using high-pressure resin transfer molding (HP-RTM).Fabrication methods Composites Technology
There are numerous methods for fabricating composite components. Some methods have been borrowed (injection molding, for example), but many were developed to meet specific design or manufacturing challenges. Selection of a method for a particular part, therefore, will depend on the materials, the part design and end-use or application.