Direct digital manufacturing of three-dimensional functionally graded material objects

Among the different types of direct digital manufacturing (DDM) technologies, some of them can be used for making functionally graded material (FGM) objects. Apart from specific characteristics of the DDM process being employed, one problem in FGM object fabrication is the generation of the corresponding information complete format so that the functionally graded material information can be realized. In this paper, this issue is addressed and the three-dimensional printing (3DP) process is considered as the DDM technology employed for making a FGM prototype. The property of printing a 3D prototype in color is adopted and a methodology is proposed for representing the mechanical properties of an FGM object by color information. In this methodology, an object is considered as "functionally graded" if its mechanical strength is gradually changed within the object and the mechanical strength arisen from gluing powdered material by binders in 3DP is assumed to be proportional to the concentrations of the binders applied in it. If the concentration of each primary color binder is different and a pixel of color is printed in the appropriate proportion, the resultant pixel would have a corresponding binder concentration value. To determine the binder concentration requirements, a computer-aided engineering (CAE) analysis is first carried out and the concentration requirements in different parts of the object are inferred from the CAE analysis result. These requirements are then converted to color information by applying the proposed methodology. As the binder concentrations of different colors are different, a colorful prototype would also be an FGM one.