چكيده به لاتين
Incremental sheet forming is a rapid prototyping method. It forms the sheets with no need to punch and die, which are commonly used in the conventional forming process. In this method, a forming tool travels incrementally into the sheet and forms it by moving in a defined path. The motion path is derived as a G-code by using a computer-aided design and computer-aided manufacturing (CAD/CAM) software and can be transferred to a CNC milling machine. Travelling of the defined path by the tool, results in production of the shape on the sheet. Using the CAD/CAM software and CNC milling machine, as critical equipment in the incremental forming, enables the production of complicated shapes by this method and increases its flexibility.In this thesis, the surface quality and forming limit diagram of mild steel sheets, during the manufacturing of a fender is studied. It is a significant issue to reduce the surface roughness (SR) which is a weakness in the manufacturing of the mild steel parts in ISF process. SR has an adverse effect on the esthetic aspects of the mild steel products or their painting appearance. Also, Presence of waviness in the incremental sheet forming (ISF) has a detrimental effect on the surface quality of parts, especially on the appearance of those covered with paint. SR is measured by Ra and waviness is measured by an innovative method. The proposed method is based on the root-mean-square-deviation (RMSD) of the height of the points located on the wavy surface. In this way, some points are selected on the formed wall and their coordinates are measured using a coordinate measuring machine (CMM). The other part is forming limit diagram, which is studied by the M-K model with addition of through thickness shear stress. Feed rate, tool diameter, vertical step and spindle speed are chosen as four input variables in the experimental tests. Taguchi design of experiments (DOE), analysis of variance (ANVOA), grey relational analysis with combination of Taguchi optimization method are used for studying and multi-optimizing the effects of the four process parameters to minimize the waviness, SR, time, thickness and the height of the forming process.
