Abstract: A mold tool (16) for forming a trim covered foam substrate of a seat assembly comprises an upper mold cast (18) defining an upper mold surface (19) and a lower mold cast (20) defining a lower mold surface (2). A split line (28) is defined adjacent to the upper and lower mold surfaces between the upper mold cast and the lower mold cast when the mold casts are in facing mating engagement forming a mold cavity (22) therebetween. A plurality of heat lines (24) extend through the upper (18) and lower (19) mold casts adjacent the respective upper and lower mold surfaces for heating the mold cavity (22). A cooling line (30) extends through at least one of the upper and lower mold casts adjacent the split line (28) for cooling the split line of the mold tool.