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.
Read complete article
GM is first automaker to use Class A CFRP parts from new pressure-press technology.Press-molding method emulates autoclave 3/1/2013 Composites Technology
Rubber tool insert avoids consolidation pressure “dead zones” and slashes cost.Class A CFRP body panels: Six-minute cure 3/1/2013 Composites Technology
Gurit CBS-based laminate/process combo mints parts with twice the thermal performance in one-sixth the time.Formulation flexibility: Direct-SMC 3/31/2012 Composites Technology
Consortium applies inline-compounding technology to reinvent sheet molding compound.Forged composites replace complex metal parts 2/29/2012 Composites Technology
Powerhouse manufacturer’s high-pressure compression molding process forms prepregged CFRP components with forged-metal properties.