Laser hardened trimming tools: wear test and geometry evaluation

The higher product requirements (reduced weight, increased safety, lower emissions…) have meant that a larger number of car body parts must be made in advanced high strength steels. With a reduced lifecycle of a car model from 7 to 5 years this leads to a need for reducing the manufacturing cost and lead time for the tool and die design and manufacturing. The main purpose of this investigation is to establish cost- and lead-time reducing guidelines for selection of tool concepts (choice of die materials, hardening methods and geometry) for different production volume scenarios with respect to sheet materials quality (MS-UHSS) and thickness, without increased die maintenance costs. In this study the cutting edge geometry has been evaluated in respect to the cutting edge radius and the angle of the upper tool. Experimental testing together with FE simulation has been used. Results show that an angle of 93° on the upper cutting edge initially can reduce the cutting work by 14%. Results also shows that by using a cutting edge radius of 80µm, the tool “wear in phase” can be more controlled. Wear test up to 150 000 strokes have been made to evaluate different tool concepts using laser hardened cast iron, cast steel and wrought steel as die material. Sheet material tested was 220RP, DP600, DP800, 700MC and DP1000, with a thickness of t=2mm. The result leads to recommendations for industrial verification. Results among other recommendations are: laser hardened EN-JS-2070 up to 500 000 parts against 220RP and Sleipner up to 1 500 000 parts against 1000DP.