Box-Behnken designs
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You can create blocked or unblocked Box-Behnken designs. The illustration below shows a three-factor Box-Behnken design. Points on the diagram represent the experimental runs that are performed:

You may want to use Box-Behnken designs when performing non-sequential experiments. That is, you are only planning to perform the experiment once. These designs allow efficient estimation of the first- and second-order coefficients. Because Box-Behnken designs have fewer design points, they are less expensive to run than central composite designs with the same number of factors.

Box-Behnken designs can also prove useful if you know the safe operating zone for your process. Central composite designs usually have axial points outside the "cube" (unless you specify an a that is less than or equal to one). These points may not be in the region of interest, or may be impossible to run because they are beyond safe operating limits. Box-Behnken designs do not have axial points, thus, you can be sure that all design points fall within your safe operating zone. Box-Behnken designs also ensure that all factors are never set at their high levels simultaneously.