Foaming technology in long glass fiber filled materials

A method of making a foamed part, comprising:

• introducing a glass fiber filled polymeric material to a hopper of an injection molding machine, wherein the glass fibers have a pre-molding length;
• melting the glass fiber filled polymeric material to form a melt;
• pressurizing a plasticizing unit of the injection molding machine with a blowing agent, wherein a seal is located between a rotating part and a fixed part of the plasticizing unit, the seal between a screw shaft and a plasticizing cylinder at an end of the screw shaft of the plasticizing unit to prevent loss of blowing agent;
• sealing the plasticizing unit with an airlock mounted between the plasticizing cylinder of the injection molding machine and the hopper to homogenize the melt and the blowing agent;
• increasing a pressure of the blowing agent and increasing a back pressure of the injection molding machine to homogenize the melt and the blowing agent, wherein the screw shaft is in a screw and is under a pressure with a relatively flat pressure profile to prevent breakage of the glass fibers;
• and
• forming the foamed part;
• wherein a post-molding length of the glass fibers in the foamed part is greater than or equal to a post-molding length of glass fibers in a similarly dimensioned foamed part made without pressurizing the plasticizing unit due to glass fiber breakage caused by shear stress during homogenizing of the melt and the blowing agent.