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In this study the mechanical properties of parts 3D printed with virgin polylactic acid (PLA) to those printed with recycled PLA were compared. Using an entry level 3D printer and commercially available PLA, tensile specimens were produced and then tested. The specimens were then ground up and re-extruded into filament, and a second set of specimens were produced and tested using this recycled PLA filament. Mechanical testing showed that 3D printing with recycled PLA is a viable option. However, although the average mechanical properties before and after recycling were similar, there was more variability in the results of the recycled filament. Additionally, when printing with the recycled filament there was some nozzle clogging, while none occurred with the virgin filament. Overall, the mechanical properties of specimens 3D printed from recycled PLA filament were similar to virgin properties, encouraging further development in the area of recycling 3D printed filament.

The paper deals with the problem of tolerance specification and, in particular, proposes a graph-based method and a preliminary software tool: (i) to accomplish the tolerance specification for a mechanical assembly; (ii) to verify the consistency of the specification and, (iii) to allow the tracing of relationships among parts and features of the assembly. The method adopts Minimum Reference Geometric Elements (MRGE), directed graphs (di-graphs) and a set of dedicated algorithms to tackle the problems of consistency that occur during an interactive tolerance specification activity. Finally, an application illustrates the proposed method and its actual implementation.

Nowadays digital substitutes of human beings (digital humans), capable of interacting with digital mock-ups in Virtual Reality, are widely used in many fields of engineering (e.g. ergonomics, product design, maintenance, and training). Nevertheless, the animation process of digital humans is still a time-consuming task, and its accuracy and reliability strongly depend on the experience and the skills of the operator. This paper presents an innovative algorithm capable of significantly speeding up the animation process of digital humans, allowing the operator to focus only on the so-called “task-related control points”. This approach allows also to easily conduct biomechanical analyses. The algorithm has been tested with reference to several application scenarios in Virtual Reality.

The Iterative and Participative Axiomatic Design Process (IPADeP) deals with the early conceptual design stage of complex mechanical assemblies. It provides a systematic approach based on the theory of Axiomatic Product Development Lifecycle and aims to minimize the risks related to the uncertainty and incompleteness of the requirements, considering that the requirements will be refined and completed during the process. IPADeP has an iterative nature and is focused on the experience of the people involved in the design process. The functional requirements and the design parameters are conceived through brainstorming sessions and the concept selection is performed involving several experts through a Multi Criteria Decision Making technique. IPADeP has been adopted as methodology to address the early conceptual design stage of a subsystem of the DEMOnstration fusion power plant: the divertor cassette-to-vacuum vessel locking system. A first iteration was performed, resulting in the selection of a "high level" rough solution. According with IPADeP this paper presents an improvement of this solution, performing a new iteration of the process, since the system is ripe to proceed with the decomposition and zigzagging to the second level and new requirements are coming in from the development of the interfaced systems. © 2015 The Authors. Published by Elsevier B.V.