If you have an image that is filled but you only want to print an outline, you can choose between several options. 

(See this video in youku/ 请观看优酷视频)

Example 1: Snowman - each print has two layers, printed with a 1.5 nozzle: 

Example2 : Donut - each shape has 2 layers, printed with a 1.5 nozzle:

Example 3: Circle - each shape as one layer, printed with a 4.0 nozzle:

Also see concentric setting explained.