Improve tool structure for enhancement of product quality in single point incremental forming

Single Point Incremental Forming (SPIF) is a new sheet metal forming method that parts can be formed without using specialized dies. In SPIF process, product quality is highly dependent on hardness and surface roughness of the tool. In the current, at National Key Laboratory of Digital Control and System Engineering (DCSELAB), Ho Chi Minh City University of Technology, there are many studies in order to improve surface quality but no one reached the desired. The highlight of this paper is improvement and fabrication tool for enhancement of surface quality using fractional factorial experimental design. The tool tip made from a ball in ball bearing, which is made from OL100Cr2, with roughness less than 0.125 µm, hardness 61÷65 HRC, welded to the handle which machined by turning. In this paper, a 24–l fractional factorial design (FFD) is used to optimize four factors: tool diameter Dp (mm), spindle rotation speed n (rev/min), size of the incremental step-down Δz (mm) and feed rate Fxy (mm/min). Experiments applied on two type of tool: ball and hemisphere tip and replicated three times. Totally, there are 48 experiments and the regression is generated for each of tip type.