**2.3 Design for manufacturing and assembly**

Among the methods to support the design of products that can help to consider the manufacture and assembly during the conception phase, DFMA is used as a support to improve the product concept, or an existing design. After all, the focus of DFMA is to help generate a design considering the company´s capacity, to facilitate the final product assembly (Estorilio and Simião, 2006).

The DFMA aims the project and production planning to occur, simultaneously, from a set of principles. Already in the DFMA redesign helps bring the product the best characteristics of production and assembly, seeking to improve quality and reduce manufacturing and assembly time (Dufour, 1996).

According to Stephenson and Wallace (1995) and Boothroyd, Dewhurst and Knight (2002), the requirements of the original design should be reviewed to establish the new DFMA quality requirements, always considering the following basic principles of design for manufacturing (DFM) and design for assembly (DFA): simplicity (reducing the parts number, shorter manufacturing sequence etc.); materials and components standardized; tolerances release (avoid too tight tolerances, which imply high costs); use of more processing materials; reduce secondary operations; use of process special features (to take advantage of the special capabilities of manufacturing processes, eliminating costly and unnecessary operations); avoid limitations in the process.

#### **2.4 Rapid prototyping**

Rapid Prototyping (RP) is an innovative technology developed within the last two decades. It aims to produce prototypes relatively quickly to visual inspection, ergonomic evaluation, analysis of shape and dimension and, as a standard for the production of master tools, to help reduce process time for product development (Choi and Chan, 2004).

RP allows designers to quickly create tangible prototypes from their projects, rather than bidimensional figures, providing an excellent visual aid during preliminary discussions of the project with colleagues or clients.

Currently on the market there is available a multitude of existing rapid prototyping technologies: Stereolithography (SLA), Laminated Object Manufacturing (LOM), Fused Deposition Modeling (FDM) and Three-Dimensional Printing (3D Printing) (Chen, 2000).

This research focused on the technology of Fused Deposition Modeling (FDM), because it offers lower equipment cost (Kochan, 2000); and as such, it is within reach of small and medium enterprises and research institutions.

The basis of FDM is the deposition of layers on a platform from heated filament, and softening of the material for the creation of the plastic model; simultaneously, other softened wires are forming a support for the free surfaces of the suspended model, providing the structure upon which the model can be finished.

The wires for the model are normally made from ABS (Acrylonitrile Butadiene Styrene), while the brackets are a mixture of ABS and lime. From the generated prototype, the team can: review the adopted product as a reference; test its specifications; test manufacturing or assembly scenarios; propose dimensional or constructive amendments; and establish possible improvements to be made in the end product to be developed.
