The need for shorter product development time together with the increasing demand for more customer based products have led to the next generation of ICT sytems in manufacturing. Manufacturing industries striving to integrate their business functions and departments with new systems in a company database. . These systems are based on the digital manufacturing concepts according to which production data management systems and simulation technologies are jointly used for optimizing manufacturing parameters before beginning the production and supporting the further phases . These industrial objectives have given room for the extensive use of ICT in manufacturing. The concept of Computer Integrated Manufacturing (CIM) indicates the introduction of ICT in the manufacturing world. This concept was influenced the enhancement of performance, efficiency, operational feasibility, product quality, responsive behavior to market differentiation and time to market This concept was introduced into inventory control and Material Requirement Planning (MRP) respectively.. In digital manufacturing apart from conventional engineering data and drawing information but also a lot of non-geometry information like experience and knowledge should be processed. The discretization and digitization process contains a series of theory problems, like digital model of physical quantities that is heat, sound, force, vibration, speed, error and so on that appear with the geometry quantities like displacement, multi-coordinates, coordinated displacement in the manufacturing process. Next is fusing the digital models of both physical and geometric quantity and their relationships in computer.. In digital manufacturing information is dominant and active factor. The advancement in internet, standardization of software interfaces, the wide acceptance of formal techniques for the software design and development. The maturity of certain software products like RDBMS, CAD has given way for facilitating the integration among different software applications .
analysis, dynamic analysis and full simulation of geometrical properties including texture and mechanical properties of materials. CAD models are considered for the production of the parts, since they can be used for generating the code which can drive the machines for the production of the part. Rapid prototyping is an example of such a technology. With the evolution of computer technology and the combination of computer graphics and mechanical design, the computer-aided design (CAD) system which takes the database as a core, the interactive graphics system as the method and takes the analysis and calculation as the main body, and this system also has widespread application in digital manufacturing . Following the development of the CAD systems, the concept of computer-aided manufacturing (CAM) was born. The great step towards the implementation of CAM systems was the introduction of computer numerical control (CNC).This new technology has brought a revolution in the field of manufacturing by enabling mass production and greater flexibility , it has also enabled the direct link between the three-dimensional (3D) CAD model and its production. Newman and Nassehi  proposed a universal manufacturing platform for CNC machining, where the applications of various computer-aided systems (CAx) applications can seamlessly exchange information. The proposed platform is based on the standard STEP-NC. In addition, standardization of programming languages for these machines lead solution developers to integrate an automatic code generation in their applications.
According to Chang TC, Wysk RA, Wang HP Computer- aided manufacturing (CAM) is the sum of all direct and indirect activities from the blank to the finished product completed in product manufacturing process using computer- aided technology .It transforms programming which includes manufacturing, detecting, assembling, dispatching as well as all related digital information facing product design, manufacture, management, accounting and so on., into data which may be interpreted and understood by computer and shared fully in the manufacturing process, which formed the CAx integration, causing the computer-aided technology to rise to a greater level [13, 14]. Computer-aided engineering (CAE) is an extension of CAD technology, which is used for engineerin analysis, calculation, verification and simulation for part models in the process of manufacturing by using computer system, thus carrying out effective evaluation and giving results for the function, performance and various index of product design.
Rapid prototyping (RP) refers to the fabrication of a physical model from computer-aided design (CAD) data by layer-by-layer deposition without using tools. RP is a relatively new technology that was first commercialized by 3D Systems in 1987. RP systems have been mainly used in manufacturing industries such as automobiles, electric home appliances and aerospace. Generally, RP processes begin with an stereolithography (STL) file that describes a model created by a CAD surface or a solid modeller. The RP models can be used to visualize or verify designs, to check for form fit and function or to produce a tooling (or master) pattern for casting or molding .
There is a great demand for implants or endoprostheses in surgery every year. Implants could be generally divided into two categories: standard and customized implants. One major drawback of the conventional method for designing customized implants is that the design process is prior to surgical interventions so that it is virtually impossible to know the optimum geometry of the implant . The design and manufacturing of custom-made implants is a multistage process. The conventional process begins with image processing to extract geometric contour curves form computed tomography (CT) data and enter them into a CAD system. Then, the Nurbs surfaces geometric model of defected bone is created from the contour curves and an implant is designed to t conform to the created model. Later, implant construction is verified through consultation between the designer and the surgeon. The final stage is the fabrication of the implant on a CNC machine tool [17, 18]. The weak points of this method are long design cycle, difficulty in consultation between the designer and surgeon and experience dependence for designer. Geometric model building based on sectional medical images is the foundation of the design of medical implants, mechanical analysis of bone, computer-aided surgery and so on. Sectional images of CT or magnetic resonance imaging (MRI) are the main processing objects. CT revolutionized medical imaging in 1972. Traditional CT systems assemble a series of cross- sectional images by incrementing the patient across the plane of acquisition a few millimeters between each slice. In this manner, a series of equally spaced two-dimensional images can describe three-dimensional anatomic structures to sub millimeter detail. . The computer-aided implant design is carried out on screen, but a solid RP model is required on hand is for easier collaboration between designer and surgeon. The bone model made by RP technology based on sectional medical images is helpful for researchers to know about configuration, position and anatomic structure of surgical location, to measure geometric parameters of pathological bones, to confer about prostheses design and to simulate assembly before operation. RP operates on the principle of depositing material in layers or slices to build up a model, rather than forming a model from a solid block. The space between the layers is typically 0.05 to 0.10 mm. Stereo lithography apparatus (SLA), laminated object manufacturing (LOM) and fused deposition modeling (FDM) are typical RP systems. .With a RP model in a surgeons hands and a visual model on screen, the design process is straight forward and fast. The surgeon makes cuts in the defected side of the RP model, in this case, and the designer responds with cuts made in the healthy side of the visual model. Surgeon and engineer make cuts in different sides because the cutout part from the healthy side would be used as a design template for the implant to maintain aesthetic facial symmetry after operation.
In todays competitive global market, product enterprises are constantly seeking new ways to shorten lead times for new product developments that meet all customer expectations. Product enterprise has invested in CADCAM, rapid prototyping, and a range of new technologies that provide business benefits. Reverse engineering is now considered one of the technologies that provide business benefits in reducing the product development cycle. Engineering is the process of designing, manufacturing, assembling, and maintaining products and system. There are two types of engineering, forward engineering and reverse engineering. Forward engineering is the traditional process of moving from high-level abstractions and logical designs to the physical implementation of a system. In some situations, there may be a physical part without any technical details, such as drawings, bill-of-materials, or without engineering data. The process of duplicating an existing part, subassembly, or product, without drawings, documentation, or a computer model is known as reverse engineering. Different researchers have given different definition for Reverse engineering based on their specific task. The different definitions are: According to Motavalli & Shamsaasef Reverse engineering is defined as the process of obtaining a geometric CAD model from 3D points acquired by scanning/digitizing existing part. The process of digitally capturing the physical entities of component, referred to as reverse engineering (RE) . Abella et al described RE as, the basic concept of producing a part based on an original or physical model wi