A preform forming machine for producing a three-dimensional dry fiber preform may include a forming block assembly and a clamping plate assembly. The forming block assembly may have a forming table and a forming block and may be positionable in a series of forming block assemblies. The clamping plate assembly may have a clamping table and a clamping plate and may be positionable in a series of clamping plate assemblies arranged in opposing relation to the series of forming block assemblies. Each forming block may be configured to fold a ply stack over onto itself to form a web of a preform. Each clamping plate may be configured to clamp the ply stack to the forming table during the folding of the ply stack.