Solid state forming of thermoplastic material

A method of solid state forming an article or thermoplastic material, said method comprising:

• heating a blank of said thermoplastic material to a temperature proximate to and below the temperature at which said material experiences a transition from its solid to its plastic phase;
• placing said blank heated at said temperature in an open mold between a rigid portion thereof displaceable relative to another rigid portion thereof, said blank having a surface area relatively smaller than the surface area of said mold and a volume relatively larger than the volume of the mold cavity defined when said mold is closed;
• maintaining said mold at room temperature;
• displacing one of said rigid portions of said mold relative to the other rigid portion of said mold at a relative velocity of at least 6.4 cm per second for impacting said blank and placing said blank under compressive strain and causing a substantial decrease in thickness of said blank;
• maintaining said blank in said mold under said compressive strain for less than 5 seconds for causing said blank to abruptly expand between said mold rigid portions and the material of said blank to flow and fill said mold cavity for forming said article, with the excess of said material exuding from said mold cavity forming a flash;
• allowing said article to cool sufficiently to remove from said mold without distorting said article;
• and
• removing said flash.