In this paper we describe a new framework for planning functionally graded and multi-step fabrication processes for use in rapid prototyping applications. This framework is contributing to software tools that will simplify planning multi-material manufacturing processes and thereby make this type of manufacturing more accessible. We introduce the material description itself, low-level operations which can be used to combine one or more geometries together, and algorithms which assist the designer in computing manufacturing-compatible sequences. We then apply these tools to several example scenarios. First, we demonstrate the use of a Gaussian blur to add graded material transitions to a model which can then be produced using a multi-material 3D printing process. Our second example highlights our solution to the problem of inserting a discrete, off-the-shelf part into a 3D printed model during the printing sequence. Finally, we implement this second example and manufacture two example components. The results show that the framework can be used to effectively generate the files needed to produce specific classes of parts.