Surface Roughness Models and Their Experimental Validation in Micro Milling of 6061-T6 Al Alloy by Response Surface Methodology

Table 1

Similarities and differences of CCC, CCI, and CCF.

	CCC	CCI	CCF
Design domain shape	Sphere	Sphere	Cubic
Design level	5	5	3
Complexity	High	High	Low
Factorial points position	±1	±0.7	±1
Axial points position
Recommend the center number	3~5	3~5	1~2
Rotatability	Rotatable	Rotatable	Not rotatable
Uniformity of prediction error	Good	Good	Bad
Model based parameter estimation	Most effective	Worst	Second
Extrapolation of robustness	Second	Best	Second

Where is the number of the variables and is the axial distance.