a superplastic forming apparatus and method for forming a sheet of material at an elevated temperatures into a workpiece having a complex geometry . the process takes advantage of a mechanical forming step , which draws material along a major axis to form a first preform . upon completion of the first mechanical forming step , a second , initial superplastic forming step ask on the first preform to create a second preform having a plurality of channels or grooves located thereon . the grooves or channels function to draw additional material prior to the second or final gas forming step , which completes the forming process by driving the material against a forming surface . accordingly , the method and apparatus function to reduce forming time and eliminate thinning and wrinkling of the sheet material during the forming process .