## 1 Introduction  
Additive manufacturing (AM) technologies enable the construction of complex parts, such as high-performance parts or highly customised and specific parts [1; 2]. Production of parts providing features of almost every function and shape becomes feasible [3]. Since part complexity and geometrical features have low impact on product cost and production time, construction of batches of parts different from the other becomes feasible. Moreover, the direct link between a computer aided design (CAD)model and a built part can be currently exploited in order to produce in a fast way both prototypes and end-use parts [4]. Therefore, several technologies have been replaced by AM, even if this replacement requires dedicated redesign of product and process. In the past, other technological changes affected the production of parts and components: as an example, in the 2000s, the metal replacement (or metal-to-plastic replacement) started to be one of the main industrial trends [5; 6], involving all the industrial fields, and it is still an ongoing trend. Similarly, but most recently, we can state that the same role is played by the AM technologies. These trends share the main common goal of making parts lighter and more efficient to be manufactured. Moreover, AM can further benefit from its integration with topology optimisation (TO), leading to complex morphologies and free form models, with an increase in product customisation. Many industrial sectors have been positively influenced by AM, e.g., aerospace and automotive, as well as the medical field, which can mainly benefit from parts produced specifically for individual patient's needs. Biomedical devices account for many applications [7] as well as challenges concerning prosthetics and implants development, surgical and diagnostic aids and even tissue and organ engineering [8; 9], occupational therapy and rehabilitation [10; 11]. A further example is the development of customised assistive devices (ADs), with positive integration of AM and co-design approaches [12]. All these changes open new frontiers as well as new drawbacks. With particular regards to a redesign process based on AM, the following main issues may occur [13]:  
* Selection of redesign variants: The outputs of the TO consist of a great number of variants, which need to be managed and selected. * Optimised designs interpretation: A wide number of topologically optimised design alternatives usually occur due to the redesign loops during the workflow iterations, requiring the designer to evaluate and interpret them into CAD models. * Definition of product and process parameters: The designer is used to evaluate and optimise one parameter at a time or a single parameter category, considering separately functional and production requirements. * File exchange and data management during the workflow iterations: The entire workflow, from the first model to final job creation, involves different software tools that need different file formats (as inputs), requiring multiple conversions of file formats due to iterations during the design and the industrialisation tasks. An STL file is used as interchange file between different software: as a support for CAD modelling parts starting from the results of TO, for finite elements analysis (FEA) simulation, for industrialisation tasks in the AM preparation software, for AM process simulation. These practises, common in the industry, highlight the need for approaches, methods and tools to support the product optimisation and, at the same time, the process optimisation, by identifying the best-developed solution. Therefore, to exploit the benefits offered by the AM implementation, the concurrent development of technology and its specific knowledge is urged. Thus, design for additive manufacturing (DfAM) of proper methods, systematic tools, objective guidelines and approaches, as well as their implementation and application, is fundamental [14; 15; 16].