Surface Finishing/Compression Molding SFC: The Valyi™ Process 1999-01-0850
A new approach (The Valyi™ Process) to an old process (compression molding) provides an economical route to the molding and Class “A” finishing of large thermoplastic parts in one step. In the process, a precut Class “A” film finish blank is placed over a mold cavity in a vertical press. Plastic melt is extruded onto the film and the press closed to mold the part. The Valyi™ Process, defined as a surface finishing/compression molding or SFC process, is similar to the textile back molding process in which plastic is deposited from a die onto a mold cavity and compression molded against a textile or other material held by the mold core1,2,3. In the SFC process, the melt, deposited directly on the film backing layer, heats the film finish and causes it to become pliable for forming. Positive air pressure may be supplied under the film finish for support as the film softens from heat transferred from the extruded plastic4.
Compression molding in general is accomplished at a much lower pressure than conventional injection molding. Molding (cavity) pressures for the SFC process are <<10 MPa (1450 psi) compared to >30 MPa (4350 psi) for injection molding. The in-mold application of the film finish achieves paint appearance and protection of paint without the environmental and cost impact of painting. Heating the film in the mold eliminates the pre-heat/thermoforming step used with film finish inserts and permits the use of thinner film finish constructions.