Deep spinning of sheet metals

Abstract

Spinning of sheet metals into cylindrical cups is an important sheet metal forming process for its advantages of flexible tooling and very small forming loads. The most challenging aspect in this process is its low formability due to wrinkling formation in the free flange. In this work, a new deep spinning process with roller set aided with blank-holder of constant clearance is proposed aiming to suppress the wrinkling formation in the deformation zone. Experimental work on annealed and hard aluminum sheet metals is carried out to assess the new process. The proposed spinning process has shown rapid increase in the formability of the sheet metals as the roller feed increases. On the other hand, significant increase in the roller feed worsens the formability of sheet metals in conventional spinning. The Limiting Spinning Ratios, LSRs; or the blank to mandrel diameters ratios, have increased from 1.75 using the conventional spinning to 2.40 using the deep spinning with annealed aluminum sheets in one pass. Also, the LSRs have increased from 1.67 using the conventional spinning to 2.24 using the deep spinning with hard aluminum sheets in one pass. New failure modes of flange jamming and wall fracture have been presented and discussed. In addition, the formability limitations, thickness strains, and spun cup form features at different process parameters are experimentally investigated and discussed. Further, a finite element model for the new process is presented and verified showing the limitation of the available shell elements offered by ANSYS Mechanical APDL in modeling the new process.