Multi-point sandwich forming and its applications in manufacturing contraction of wind tunnel

Thickness of the petals for constructing contraction of low speed wind tunnel is larger and forming the petals is relatively difficult. Precision of manufacturing the petals makes more contribution on the quality of the air flow. Because the shape of these petals is different, it will increase the cost and lead time for manufacturing die set if traditional die forming is adopted. Hence, a new method of manufacturing curved surface in contraction of low speed wind tunnel is presented, which is the multi-point sandwich forming. The heights of adjusted pins in die set are determined by conversion of coordinate and discretized curved surfaces that belong to the contraction during this process. Before forming, the spring-back is predicted by numerical simulation to ensure the forming precision of the petal. After testing, the heights of pin need be adjusted again according to measurement results. Research shows that multi-point sandwich forming is suitable to form the workpieces with large radius of the curvature. Furthermore, more than two hundred hyperboloidal petals with different size and shape have been formed using this process with only one die set.