Electrohydraulic trimming with scrap cutting
Publication Date: 2014-Jan-17
The IP.com Prior Art Database
The present invention relates to the technology of trimming of sheet metal parts. Modern production is utilizing wide variety of materials for interior panels, exterior panels and structural parts, such as Deep Drawing Quality Steels, Drawing Quality Steels, Bake-hardenable Steels, Dual Phase Steels, Boron Steels, and Aluminum Alloys. Where mild steels originally dominated, more lightweight materials are currently being employed. These materials are bringing variety of technological problems due to different material properties. One of the problem areas is trimming operation for body panels stamping technology. In existing practice, trimming is shearing off extra material from drawn panel. In many cases, trimming is being done in two or three steps, due to the necessity to cut scrap and some complicated geometries of the parts being trimmed. Trimming dies usually incorporate the sharp upper trim steel, sharp lower trim steel, and clamping pad (as shown in Fig. 1). Majority of Advanced High Strength Steels have much higher strength, and therefore require significantly larger forces for trimming dies. Typically to accomplish good quality trimmed surface, the clearance between the shearing edges should be below 10% of the material thickness. High mechanical loads on the die may result in its insufficient stiffness, especially for high strength material, and opening of the clearance during the trimming process. Such performance was observed in production trim dies, where geometrical clearance between the cutting edges, measured without the blank in place, was corresponding to the die design recommendations. In the meantime, stamped parts had visible burrs, which indicated that the die has excessive clearances. Another issue with trimming of AHSS materials is increased die wear, and specifically increased wear of trimming edges, which supposed to be sharp. This phenomenon leads to both increased clearance and decreased sharpness of the shearing edges.
One of the previously suggested solutions  is to use elastic scrap support to prevent the material bending and generating burrs (Fig.2). This solution lowered the requirements to accuracy of alignment of the upper and lower trim steels. Practical usage of this idea indicated that it works better for perpendicular trimming. However, scrap removal in this case becomes complicated, since trimmed off pieces of metal may stay on the elastic support. Solution  was successfully implemented for trimming of aluminum fenders and decklids and door panels where trimming was conducted with the cutting angle of approximately 15 degrees. For large cutting angles up to 60 degrees, this technology stops working due to increased angle of the lower trim steel significantly above 90 degrees. Existing industrial solution for trimming with large cutting angles is to employ the cam mechanism which would provide the upper trim steels coming perpendicular to the surface of the blank being trimmed....