Hi Bob,

The problem is definitely 3d printing machine related not file format, all FDM (Fuse Deposition Modelling) machines will always render a layered finish to your models some finer than others, machines with a heated chamber tend to produce a better finish however more expensive and if a smooth finish is required then further hand work is necessary.

The model you'll receive from Shapeways SLS machine will be a much smoother finish, sort of a medium to fine sandblast, however models with shallow curved surface will still end up with steps because it is a layer by layer of a certain thickness process, so again, if a totally smooth surface is required hand work will be necessary.

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