High-pressure molding, typically referred to as injection molding, solely uses machine pressure to fill a mold. Low-pressure molding uses both machine pressure and a chemical blowing agent to fill and pack the mold into the desired product shape. Low-pressure molding requires thicker wall sections in order to allow the foaming agent to expand. If the wall sections were too thin, the foaming agent wouldn’t have room to expand and the part would have solid wall sections like a high-pressure part. High-pressure molding uses thousands of pounds of pressure per square inch compared to low-pressure molding which only uses hundreds of pounds. The blowing agent works with the machine pressure to fill the mold. The blowing agent aids the fill and pack of the tool cavity so a smaller tonnage machine is required. Smaller machines save on machine costs.