Flexibility in metal forming

Evaluation of surface roughness in incremental forming using image processing based methods

Advanced manufacture technologies, oriented to implants featured with high reliability, low cost and high biocompatibility, are key approaches to advance the rehabilitation efficacy and shorten the recovery period of patients. Considering the shortage of current fabrication processes, the incremental sheet forming (ISF) which is featured as a flexible forming technique is applied to manufacture implants. This review begins with the overview of ISF for different kinds of materials and implants. Then, the forming quality of implants formed by ISF was comprehensively reviewed and discussed in various aspects including the geometric accuracy, surface quality, and the forming limit. Moreover, various micro manufacturing processes and the size effect were summarized for the purpose of surface modification of medical implants. Based on the investigation of micro manufacture techniques, a novel macro-micro hybrid ISF technique was proposed to form the macro-profile and the micro-structures of implants synergistically through a single manufacturing process with different scales. Finally, future scope and potential research directions were addressed.

Incremental sheet forming towards biomedical implants: a review

Lightweight materials, such as titanium alloys, magnesium alloys, and aluminium alloys, are characterised by unusual combinations of high strength, corrosion resistance, and low weight. However, some of the grades of these alloys exhibit poor formability at room temperature, which limits their application in sheet metal-forming processes. Lightweight materials are used extensively in the automobile and aerospace industries, leading to increasing demands for advanced forming technologies. This article presents a brief overview of state-of-the-art methods of incremental sheet forming (ISF) for lightweight materials with a special emphasis on the research published in 2015–2021. First, a review of the incremental forming method is provided. Next, the effect of the process conditions (i.e., forming tool, forming path, forming parameters) on the surface finish of drawpieces, geometric accuracy, and process formability of the sheet metals in conventional ISF and thermally-assisted ISF variants are considered. Special attention is given to a review of the effects of contact conditions between the tool and sheet metal on material deformation. The previous publications related to emerging incremental forming technologies, i.e., laser-assisted ISF, water jet ISF, electrically-assisted ISF and ultrasonic-assisted ISF, are also reviewed. The paper seeks to guide and inspire researchers by identifying the current development trends of the valuable contributions made in the field of SPIF of lightweight metallic materials.

Emerging Trends in Single Point Incremental Sheet Forming of Lightweight Metals

In incremental sheet metal forming (ISF), by maintaining contact between tool and sheet metal can help in uniform thickness distribution and improved surface quality. In the present work the tool path versatility has been explored by transferring some of the tool-sheet relative movements to the work piece by using a two-degree of freedom robotic manipulator with an aim to improve surface finish and achieve greater wall angles. The robotic manipulator has been designed to orient the sheet metal part with respect to the forming tool fixed in the three-axis machine tool to form steeper wall angle parts with better surface finish. The effect of rotational speed, wall angle, tilting angle and tool linear step interval on forming quality in robot assisted incremental forming has been studied and analyzed. Steeper wall angles and better surface finish were found to be obtained with the help of the robotic manipulator than the conventional incremental forming. The results of design of experiments based parametric study on surface finish have been presented.

Investigation of influence of part inclination and rotation on surface quality in robot assisted incremental sheet metal forming (RAISF)

Incremental sheet metal forming (ISF) is an emerging technology where the sheet is deformed incrementally by a stylus tool using a predefined tool path. Higher formability and process flexibility as compared to conventional forming can be achieved by this process. However, forming steeper wall angle parts in single-stage forming has been a challenging task in ISF. In this work, a robotic manipulator has been used to manipulate sheet metal with respect to tool to form steeper wall angle parts in a single stage. Process parameters have been varied to investigate the fracture limit of the sheet at steep wall angle. Effect of part inclination and part rotation using the designed manipulator on the formability of the sheet has been investigated. Analytical investigation of the effect of parameters on forming force and formability has been discussed and later validated by numerical simulation and experiments. The results show that the formability of the sheet changes by varying these process parameters. Formability can be improved by changing the part inclination and part rotation.

Robot-assisted incremental sheet metal forming under the different forming condition

Product quality and production time are critical constraints in sheet metal forming. These are normally measured in terms of surface roughness and forming time, respectively. Incremental sheet metal forming is considered as most suitable for small batch production specifically because it is a die-less manufacturing process and needs only a simple generic fixture. The surface roughness and forming time depend on several process parameters, among which the wall angle, step depth, feed rate, sheet thickness, and spindle speed have a greater impact on forming time and surface roughness. In the present work, the effect of step depth, feed rate and wall angle on the surface roughness and forming time have been investigated for constant 1.2 mm thick Al-1100 sheet and at a constant spindle speed of 1300 rpm. Since the variable effects of these parameters necessitate multi-objective optimization, the Taguchi L9 orthogonal array has been used to plan the experiments and the significance of parameters and their interactions have been determined using analysis of variance (ANOVA) technique. The optimum response has been brought out using response surfaces. Finally, the findings of response surface method have been validated by conducting additional experiments at the intermediate values of the parameters and these results were found to be in agreement with the predictions of Taguchi method and response surface method.

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Influence of process parameters on surface roughness and forming time of Al-1100 sheet in incremental sheet metal forming

Tool Path Planning for manufacturing of Asymmetric parts by incremental sheet metal forming by means of Robotic manipulator

Incremental sheet metal forming is a recently innovated technology of achieving asymmetric sheet metal parts without using a die and through computer numerical control machine tool based path programming by inducing localized plastic deformation with a spherical ended tool. One of the major limitations of the existing method of incremental sheet metal forming is the limiting wall angle, where a wall angle of greater than about 70° is difficult to obtain. The recently proposed solution of multi-stage incremental forming can enable obtaining wall angles close to 90° but it takes longer manufacturing time and may pose problems for materials that severely strain harden. Robot-assisted incremental forming has a potential to offer an alternative solution for steel wall angle limitation but the existing work in the literature on robot-assisted incremental forming mostly focused only on the use of a standalone robotic manipulator instead of the limiting 3-axis CNC vertical machining center or a more expensive 5 or 6-axis vertical machining center. In this paper a review and comparative study of existing multi-stage incremental forming and robot-assisted incremental forming technologies in solving the limiting wall angle problem is presented.

Swagatika Mohanty

Papers

Investigation of influence of part inclination and rotation on surface quality in robot assisted incremental sheet metal forming (RAISF)

Robot-assisted incremental sheet metal forming under the different forming condition

Influence of process parameters on surface roughness and forming time of Al-1100 sheet in incremental sheet metal forming

Tool Path Planning for manufacturing of Asymmetric parts by incremental sheet metal forming by means of Robotic manipulator

Multi-stage and robot assisted incremental sheet metal forming: a review of the state of art and comparison of available technologies