A die assembly including a first die with a first die surface and a first cutting rib extending from the first die surface. The first cutting rib includes a first cutting surface parallel to the first die surface. The first cutting rib includes a leg extending from the first die surface to the first cutting surface at a first obtuse angle. A second die includes a second die surface and a second cutting rib extending from the second die surface. The second cutting rib includes a second cutting surface parallel to the second die surface. The second cutting surface is generally parallel to and defines a cutting overlap with the first cutting surface at a cross-section taken through the first and second dies in a cutting position. The cutting rib includes a leg extending from the second die surface to the second cutting surface at a second obtuse angle.