Method of heat-trimming foam material

In a method of heat-trimming thermoplastic foam materials, the steps of:

• providing a mold in the form of two mold pieces of metal of high heat-conductivity in substantially vertical alignment with each other, said mold pieces having at least two aligned edges forming a trim guide,
• placing a sheet of foam material at oven temperature between said mold pieces of high heat-conductivity,
• providing a trim tool,
• heating the trim tool to a temperature at least high enough to melt the foam material,
• cooling the mold pieces to absorb the heat of melting of the foam material;
• moving the mold pieces of high heat-conductivity relative to each other to form the foam material to the form of the mold and pressurize the foam material along the portion to be trimmed,
• positioning the heated trim tool relative to the mold along the aligned edges thereof forming the trim guide,
• and trimming the piece of foam material along the trim guide by melting or vaporizing the portion of the foam material along the trim guide and stopping melting of the foam material along the trim guide by absorbing the heat of melting by the trim guide, and thereby preventing the formation of flash along the trimmed edge of the foam material.

In a method of heat-cutting thermoplastic materials the steps of:

• providing two mold pieces of metal of high heat-conductivity in vertical alignment with each other at least one edge of each piece forming a trim guide,
• moving at least one piece of metal toward the other to form a pressure exerting device and confine and pressurize the foam material along the region to be trimmed,
• providing a cutter,
• heating the cutter to a temperature at least high enough to melt the foam material,
• placing a sheet of foam material between the pieces of metal of high-conductivity forming the trim guide,
• moving the pieces of heat-conducting metal toward each other and pressurizing the piece of foam material along the portion to be trimmed, and maintaining the heat conducting metal cool enough to absorb the heat of melting to thereby provide a definite point at which melting stops,
• then bringing the heated cutter along the trim guide and trimming the piece of foam material along the trim guide by melting the foam material and stopping melting thereof at the edge of the trim guide by absorption of the heat of melting by the cooled trim guide.