Single point incremental forming (SPIF) is an emerging sheet forming method and has been widely accepted by the researchers for fabricating the customized items for the industrial uses and the end users. The measurement of the deforming loads during this viable method would assess the need of specific capacity of the SPIF machines for the given process conditions and materials. Therefore, this work aims at investing the influence of the punch feed rate and the forming angle on the peak values of the deforming loads. The conical frustums of the varied forming angles are produced from the AA2024 aluminum alloy sheets. The CNC milling machine was utilized for this die-less sheet forming. The table type dynamometer was utilized for recording the peak values of the deforming loads during the fabrication of the frustums. Experimental results confirmed that both the input factors were significant to impact the deforming loads. It was also confirmed that the small increment in the forming angle led to the significant rise in the deforming loads for all punch feed rates.
Top1. Introduction
A dramatic development in the obsolescence of manufacturing techniques has been well accepted by the global market for producing user-ready and user-oriented components. The production sector has been attempting several approaches to upgrade its business by hatching the customized products economically (Mittal, 2020). Customized and batch-type production can be executed by employing the emerging techniques of manufacturing of less cycle-time and economical set-up. Incremental Sheet Forming (ISF) can be refrred as an emerging method for manufacturing the customized sheet material parts for various applications (Kumar and Gulati, 2019, Kumar et al., 2018a). The end-user components can be formed by the ISF technique with negligible wastage. Also, the force needed to produce the deformation during the ISF process is quite less in comparison of other sheet forming methods. The requirement of a smaller forming force leads to the employment of the light-weight and small size forming machinery to execute the process (Kumar et al., 2018b; Jeswiet et al., 2005; Bagudanch et al., 2019). Moreover, the cost of the forming machinery and tools involved in the ISF technique becomes lower that leads to producing a smaller number of components to reach the breakeven point of the process. Furthermore, the absence of dedicated and costly experimental set-up, during the ISF process, opens the gates for producing customized parts economically according to the cutting-edge requirements of product users (Gulati and Kumar, 2018; Manju and Kumar, 2020; Centeno et al., 2014).
Moreover, various economic aspects, such as low emissions and energy requirements, can be controlled up to the large extent by ensuring the utilization of the potential techniques and processes that can fabricate the parts of lightweight materials with reduced power and machinery to ensure the saving of resources (Suresh et al., 2015; Kumar et al., 2019a). The principle of ISF includes deforming the sheet material plastically, contour by contour, by governing the punch on the specimen using the CNC machine (Kumar et al., 2020). SPIF is a purely “die-less process” that refuses the requirement of specific dies and is capable of fabricating the intricate and complex shapes successfully (Kumar et al., 2019b; Kumar etal., 2018c). SPIF, also called “negative incremental forming”, is based on deforming the sheet material, contour by contour, by a hemispherical-ended punch that is normally controlled by a predetermined toolpath as illustrated in Figure 1. Furthermore, the lower deforming loads are needed for deforming the material into the designed shape. The need for a smaller amount of required forces, for producing deformation, leads to reducing the power and energy requirements up to a greater extent for accomplishing the process that further reduces the cost of process and machinery. Hence, the peak deforming loads to produce the desired shape, for specific operating conditions and materials, can determine the size and capacity of forming hardware. Moreover, estimation and investigation of the maximum value of deforming loads may assure the secure and effective employment of forming machinery during this die-less process (Kumar et al., 2019c). The measurement of forming force can be accomplished by mounting the force dynamometers either on the forming tool or between the ISF fixture and machine table. Most of the researchers (Kumar et al., 2018c; 2019c, Alsamhan et al., 2019; Honarpisheh et al., 2018; Zhai et al., 2020; Kumar and Gulati, 2018, 2021; Oleksik et al., 2010; Fiorentino et al., 2009) have used a later method (in which a load cell or force dynamometer is fixed between the clamping device and machine table) for recording the deforming loads as represented by Figure 2.
Figure 1. The principle of SPIF technique