Page 15 - MetalForming December 2009

of the process, manual intervention can occur to easily introduce different requirements than might typically be expected. The urge to design as many straight-line segments into the blank contour, creating corner angles in order to simplify the blanking die, no longer is required. These blank shapes, intend- ed to simplify the blanking-die design, limit the ability to optimize raw mate- rial usage. Conversely, in accordance with the drawing or forming processes, laser cutting yields blank contours with adequate curvilinear features that can increase blank formability.
Automotive Trends: Higher-Strength Steels, Lower Volumes
The increased use of advanced-high- strength steels requires higher-tonnage blanking presses. Tools wear more quickly and the quality of the cut edge becomes an issue when the number of micro fractures that occur along the cut edges of the blank increases. These
micro fractures can develop into splits during forming. Laser blanking elimi- nates these issues, as material tensile and yield strength have little or no impact on laser-cutting speed, and there are no micro fractures produced during laser cutting.
Also, as automotive OEMs have decreased model volumes, the invest- ment required to manufacture a part can no longer be spread out over a large number of parts. This is where laser blanking shines, by eliminating the need for a dedicated tool. A typical blanking die, depending on its size and contour complexity, can cost as much as $250,000. If the annual production of a part is 300,000 units, the die adds near- ly $1.00 to the piece price of every part, not accounting for the value of the ini- tial time investment made prior to the actual manufacturing of the part. Man- ufacturing costs will include variable costs such as labor, utilities, consum- ables, repair, maintenance, and overhead and expenses related to production.
Operational Saving with Laser Blanking
Laser-blanking lines provide an oper- ational cost advantage over traditional blanking lines. They avoid the need to build a press pit, and certain configu- rations eliminate the need for a coil looping pit. Other avoided costs include those for high crane capacity and die- storage and die-change requirements.
Of course, laser cutting also pro- vides flexibility. Modification to the cutting program for a developed blank is one of the most identifiable flexible features. With laser cutting, the pro- gram can be modified with a simple 2D CAD software program. Costly changes that would take days to imple- ment with a die can be made at virtually no cost, and in only a few minutes of reprogramming time. Whereas the typ- ical nesting routine for mechanically blanked parts has many rules based on the type of punching or shearing used to cut inside the blanking die, laser cutting simplifies the process and expands the
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