Incremental sheet metal forming characterized as increased flexibility and local plastic deformation is well suitable for low-production-run manufacturing and a new sample trial production of complex shapes. Thickness thinning is still an obstacle to the application of incremental forming. In this study, a novel mathematical algorithm based on a non-uniform rational B-spline (NURBS) surface was proposed and implemented which focuses on predicting and calculating the final thickness for arbitrary parts in incremental forming. In order to evaluate the validity of the proposed model, the finite element simulation and forming experiments of three kinds of parts, such as truncated cones, truncated pyramids and ellipsoid parts, were conducted. The thickness of theoretical prediction was compared with that of finite element simulation and experiment, and good agreements were obtained. The results show that the proposed model and the method are effective and robust for predicting the thickness of the formed parts in incremental sheet metal forming.

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A Novel Algorithm for Thickness Prediction in Incremental Sheet Metal Forming

Process capabilities and future scope of Incremental Sheet Forming (ISF)

Incremental sheet forming is a die-less forming method to deform the sheet in a stepwise manner to get the final product. In the current work, the Al 6061 sheet has been deformed using single point incremental sheet forming methodology on 6-axis industrial robot to produce a single wall angle and double wall angle conical shape. The wall angle of 68.2° has been obtained using a multi-stage forming strategy. Two types of tools, namely roller ball tool and fixed ball tool have been deployed to accomplish the process. The deformed sheet has been investigated for sheet thinning and surface finish. The quality of the product in terms of forming depth, greater wall angle, and surface finish is better for multi-stage incremental sheet forming. 

Experimental Investigation of Multi-stage Robot-Assisted Single Point Incremental Sheet Forming of Al 6061 Sheet

Incremental sheet formation (ISF) is extensively used versatile technique for newer manufacturing processes, such as creating skull prostheses, aerospace equipment, automobile, and so on. The current work describes the techniques, history, and classification of ISF-based on the results of few aspects such as force forming, stress triaxiality, force forming, bending stress, and so on. In addition, the influence of different parameters and their effect on building force, formability, spring-back, failure, surface roughness, rupture, and so on, have been analysed. It has been noticed that an investigation of the two degrees of freedom (DF) robot-manipulators with the ISF and its influences on surface coarseness and formability are greatly suggested. 

A brief review on the perspective of a newer incremental sheet forming technique and its usefulness

Incremental sheet forming (ISF) requires no or partial dies for sheet metal fabrication and is widely used for small batch production. In this process, necking is either suppressed or delayed due to the localized nature of tool–sheet contact; hence, more strains than conventional stamping and deep drawing are obtained. In the present study, two variations of ISF, namely cold ISF (CISF) and warm ISF (WISF), are compared. First, FEA modeling is carried out on ABAQUS to reach the forming forces involved in the process. It is found that WISF reduces the forming forces. The temperature for WISF is maintained at 180 °C. Following the simulation analysis, tests are carried out. The forming force in WISF is 55.77% less than that in CISF. The part fabricated by CISF is slightly more substantial than that by WISF; however, more forming depth can be achieved by WISF. There is a more uniform thickness distribution in the case of CISF than in WISF. However, the surface quality of the CISF product is inferior to that of WISF. It is observed that there is reduced forming force, increased formability, and better strain distribution in WISF compared to CISF. However, post-processing heat treatment and surface polishing of the formed parts is required to restore their mechanical properties.

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Ravi Prakash Singh

Papers

Robot assisted incremental sheet forming of Al6061 under static pressure: Preliminary study of thickness distribution within the deformation region