A new, flexible tool concept for rotary die stretch bending

Mitigating manufacturing risks for profile-type parts formed using stretch bending operations is a considerable challenge in the industry, due to the investments required to manufacture the tooling for these processes. Traditionally such tooling has been made by solid steel blocks machined to the desired shape. This paper introduces a new tool concept for stretch bending processes, utilizing an adjustable multipoint supported flexible spring steel plate as a bend die, applied on a double rotary turntable stretch bender. The capability of the tool is investigated through a proof-of-concept experiment, assessing whether the tool design is capable of creating bends with the same quality as bends made using traditional solid steel dies. Overall, the experiment shows promising results as it allows for creating a large variation of bending shapes with good dimensional quality with low tooling investment, although the interface between the spring steel plate end and the aluminum profile creates some minor scuffing marks. The initial investigation found a pooled standard deviation of 0.25mm over 3 bend shapes with 3 samples for each, which is promising for further development. In industrial applications, the proposed tool would enable cost-efficient experimenting using production-intent tooling in the early product development phase, which could also be utilized for pre-production qualification processes, low volume manufacturing and multi-variant products. © 2022