The Design of Graphical Symbols for Shape Transformations of 4D Printed Parts

Abstract

The term “4D Printing” (4DP) is defined as the ability for a part produced using an additive manufacture process to change its shape when activated by or exposed to one or more stimuli over time. This emerging technology offers unique advantages over conventional Additive Manufacturing (AM) by extending the three dimensions of space into the fourth dimension of time. 4DP parts can be programmed to actuate passively without the need for an external power source such as an electromechanical or other active system, thereby reducing the probability of failure and the complexity of components. This work attempts to address some of the challenges faced by the design engineer in a project team when producing technical documentation to specify the desired shape transformation of a 4DP part with a structured graphical representation at an appropriate level of abstraction. In this paper the requirements for a shape transforming 4DP part are represented as the allowable variation in dimensional size and tolerance in geometric form of the functionally critical features on the part for each function that the transformed shape serves. In this paper, the authors describe how the proposed standard to specify the desired shape transformations of a 4DP part could use graphical symbols in a structured specification by means of a Transformation Control Frame (TCF) to define the rules of transforming between shapes and a Bill of Transformations (BoT) to enumerate all the Transformation Control Frames (TCF) necessary to describe the intended sequence of shape transformations. To illustrate how the graphical symbols could be applied, a SMA actuated gripper is presented as a use-case.