Knowledge based System for Improving Design and Manufacturing Processes for Electrochemical MachiningIn Computer based Concurrent Engineering

The traditional design of product, the preceding constraints and limitations are considered sequentially. In order to reduce the product development cycle time and cost and increase quality and productivity, concurrent (simultaneous) design of product and process has been introduced. Electrochemical machining (ECM) is used to tackle exotic alloys of intricate shape and produce complex parts in hard metals with high surface quality and integrity. This paper addresses the concept of the knowledge base system (KBS) for optimization of product design and electrochemical machining process in computer integrated manufacturing (CIM) and computer based concurrent engineering environment. The KBS links with design and manufacturing data bases. The design specification is acquired through a feature based approach. The KBS links with material data base which holds attributes of more than 60 materials. It also links with tool data base which hold attributes of 7 tool‟s material and also 3 type of electrolytes. KBS is also links with machine data base which hold attributes of different ECM machines. For each design feature, KBS provides information needed for design and manufacturing optimization. The KBS can be used as an advisory system for designers and manufacturing engineers. It can be used as a teaching program for designers and manufacturing engineers and new ECM operators in computer based concurrent engineering environment..


ELECTROCHEMICAL MACHINING
Electrochemical machining (ECM) uses electrical energy to remove material. An electrolytic cell is created in an electrolyte medium, with the tool as the cathode and the workpiece as the anode. A high-amperage, low-voltage current is used to dissolve the metal and to remove it from the work piece, which must be electrically conductive. ECM is essentially a deplating process that utilizes the principles of electrolysis. The ECM tool is positioned very close to the work piece and a low voltage, high amperage DC current is passed between the two via an electrolyte. Material is removed from the work piece and the flowing electrolyte solution washes the ions away. These ions form metal hydroxides which are removed from the electrolyte solution by centrifugal separation. Both the electrolyte and the metal sludge are then recycled. Unlike traditional cutting methods, work piece hardness is not a factor, making ECM suitable for difficult-to-machine materials. Takes such forms as electrochemical grinding, electrochemical honing and electrochemical turning. Characteristic of ECM machining are:  The components are not subject to either thermal or mechanical stress.
 There is no tool wear during electrochemical machining.
 There is no contact between the tool and work piece.
 Complex shapes can be machined repeatedly and accurately M a r c h 1 7 , 2 0 1 5  Electrochemical machining is a time saving process  During drilling, deep holes can be made or several holes at once.
 ECM deburring can debur difficult to access areas of parts.
 Hard and also brittle material can be machined easily  Surface finishes of 25 µ in. can be achieved In other words, electrochemical machining (ECM) is a non-traditional process used mainly to machining hard or difficult to machining metals, where the application of a more traditional process is not convenient. In traditional processes, the heat generated during the machining materials is dissipated to the tool, chip, work piece and environment, affecting the surface integrity of the work piece, mainly for those hard materials. In ECM there is no contact between tool and work piece. Electrochemical (electrolyses) reactions are responsible for the chip removal mechanism [16]. The difficulties to cut super alloys and other hard-to-machine materials by conventional process have been largely responsible for the development of the ECM process. The main components of ECM system are a low voltage and high current power supply and an electrolyte. The electrolyte is normally solutions of salts, like sodium chloride (NaCl) or sodium nitrate (NaNC3). It is also necessary pumps, filters, heat exchanger and an enclosure where the reactions occur [17] [18][19] [20]. There are basically numbers of parameters that affect the work piece tolerances such as current, electrolyte type, concentration, flow rate etc. [21]. In the electronic industry, electrochemical micro-machining (ECMM) is received much attention for fabrication of micro components: by dry etching material is removed at very precise resolution. In recent years, ECM has received much attention in the fabrication of micro parts [22] [23][24] [25]. An attraction of electrochemical machining is that material removal is unaffected by hardness, and there is no contact between tool and work piece, so that the former can be comparatively softer than the latter, in contrast to conventional processes. Electrolyte is pumped through the electrode gap to remove debris, gas and heat. It has been shown that excessively high or low flow velocities can lead to the formation of vapor bubbles. Hence there will clearly be an optimum flow rate. The flow rate affects the metal removal rate and relative tool wear. Innovative applications of ECM include sawing, grinding, and finishing of thin-walled tubes. Recent advances in pulsed ECM, with dissolution occurring during phases ECM lasting o.1 to 5 ms, the off-time being 5 to 50 ms have enabled much more accurate ECM. Wire or tube-electrode ECM is also growing in popularity, for example in removal of defective parts or welded samples The combination of ECM with electrodischarge machining and the corporation of pulsed voltage has yield higher rates of removal than hitherto achieved by either these processes, and new applications for the new process called electrochemical Spark Machining (ECSM). Production process for ECM is being increasingly suggested. Electrochemical machining (ECM) is used to produce complex parts. An attraction of electrochemical machining is that material removal is unaffected by hardness, and there is no contact between tool and workpiece, so that the former can be comparatively softer than the latter, in contrast to conventional processes. Electrolyte is pumped through the electrode gap to remove debris, gas and heat. It has been shown that excessively high or low flow velocities can lead to the formation of vapour bubbles. Hence there will clearly be an optimum flow rate. The flow rate affects the metal removal rate and relative tool wear. Innovative applications of ECM include sawing, grinding, and finishing of thin-walled tubes. Recent advances in pulsed ECM, with dissolution occurring during phases ECM lasting o.1 to 5 ms, the off-time being 5 to 50 ms have enabled much more accurate ECM. In the electronic industry, electrochemical micro-machining (ECMM) is received much attention for fabrication of micro components: by dry etching material is removed at very precise resolution. Wire or tube-electrode ECM is also growing in popularity, for example in removal of defective parts or welded samples The combination of ECM with electrodischarge machining and the corporation of pulsed voltage has yield higher rates of removal than hitherto achieved by either these processes, and new applications for the new process called electrochemical Spark Machining (ECSM). Production process for ECM is being increasingly suggested. It is nessacerly to explain computer based concurrent engineering environment here.

COMPUTER BASED CONCURRENT ENGINEERING
Researchers described the concurrent engineering method as a relatively new design management system that has had the opportunity to mature in recent years to become a well-defined systems approach towards optimizing engineering design cycles [26]. Because of this, concurrent engineering has been implemented in a number of companies, organizations and universities, most notably in the aerospace industry. In 1990s, CE was also adapted for use in the information and content automation field, providing a basis for organization and management of projects outside the physical product development sector for which it was originally designed. The basic premise for concurrent engineering revolves around two concepts. The first is the idea that all elements of a product"s life-cycle, from functionality, reducibility, assembly, testability, maintenance issues, environmental impact and finally disposal and recycling, should be taken into careful consideration in the early design phases [ 27] . The second concept is that the preceding design activities should all be occurring at the same time, i.e., concurrently. The idea is that the concurrent nature of these processes significantly increases productivity and product quality [28]. This way, errors and redesigns can be discovered early in the design process when the project is still flexible. By locating and fixing these issues early, the design team can avoid what often become costly errors as the project moves to more complicated computational models and eventually into the actual manufacturing of hardware [29]. Concurrent engineering replaces the more traditional sequential design flow, or "Waterfall Model" [30] [31]. In concurrent engineering an iterative or integrated development method is used instead [32]. The difference between these two methods is that the "Waterfall" method moves in a linear fashion by starting with user requirements and sequentially moving forward to design, implementation and additional steps until you have a finished product. In this design system, a design team would not look backwards or forwards from the step it is on to fix possible problems. In the case that something does go wrong, the design usually must be scrapped or heavily altered. On the other M a r c h 1 7 , 2 0 1 5 hand, the iterative design process is more cyclic in that, all aspects of the life cycle of the product are taken into account, allowing for a more evolutionary approach to design [33]. Concurrent design comes with a series of challenges, such as the implementation of early design reviews, the dependency on efficient communication between engineers and teams, software compatibility, and opening up the design process. A concurrent design process usually requires that computer models (computer aided design, finite element analysis) are exchanged efficiently, something that can be difficult in practice. If such issues are not addressed properly, concurrent design may not work effectively [34]. There are several research efforts into computer support for concurrent engineering. The best known of these are the DARPA Initiative in Concurrent Engineering (DICE), Open Systems Architecture for Computer-Integrated Manufacturing (CIM-OSA), and Distributed and Integrated environment for Computer-aided Engineering project is called DICE. At least five areas can be identified in which computer based concurrent engineering systems support them by using the information technology and communication and computer technologies: 1-Sharing information to promote cooperation among the members of multidisciplinary design teams. 2-Collocating people and programs by making the access to programs, people, and data across the network transparent to the user. 3-Define a methodology for enterprise structuring through generic service and protocols (e.g. business services, information services, and communication services) and system life cycle specifications (e.g. requirements definition, design specification, build and release, operation, and maintenance).It is clear that the CIM-OSA has a much wider scope of integration compared with CE. Thus, implementation of computer-based approaches for CE should be within the CIM-OSA guidelines to achieve the maximum openness and integration, especially in intra-system and business integration.

KNOWLEDGE BASED SYSTEM FOR ECM
At present most procedures for estimation of machining time and cost and penetration rate and manufacturability evaluation are based on personal knowledge and judgment. The complexity of the process and interrelationship between its process variables means that designer and process planners have limited knowledge of ECM. In planning they have to turn to the literature or experts. The information required by the former is often difficult to obtain. Moreover, the training of both designers and process planners in CIM technology is time-consuming and expensive. Consequently if the knowledge is not available from a reliable source, the ECM product development cycle time and cost increases, and both quality and productivity is likely to decrease. Knowledge-based system KBS provide a route to overcoming these problems. In this paper a knowledge-based system (KBS) is developed to integrate design and manufacturing in computer based concurrent engineering environment for electrochemical machining. The knowledge-based is expressed in computer codes in the form of if-then rules and can generate a series of questions. A mechanism is employed for using these rules to solve problems is called an inference engine. The KBS can communicate with CAD data base and other computer software packages. The latest version of an expert system shell (NEXPERT) based on object oriented techniques is used. The output of the KBS can be used by designers and manufacturing engineers, a typical example of suggestion and estimation of machining time and cost and retrieval all necessary information from working memory for different design feature for Cast Iron work piece material by electrochemical machining is demonstrated at the end of this paper. In this paper a knowledge based system for electrochemical machining has been developed in computer based concurrent engineering environment. The developed program is based on object oriented technique (OOT). The latest model Hewlett Packard (HP) workstation was used in development of the expert systems. The system links with feature based design database. For each design feature, the system evaluates its manufacturability, machining cycle time and cost, and gives useful advice to designer for improving design in term of manufacturability and machining time and cost, penetration rate and etc. The system also gives some advice to manufacturing engineers for selection of optimum machining parameters. The system also works as a teaching system for new manufacturing operators to train them how to work with ECM machine. The KBS contains expertise gathered from both experiment and general knowledge about ECM machine that can be provided to product designers and manufacturing engineers. In general each design feature can be manufactured by alternative processes in concurrent engineering environment. For future work, we need intelligent knowledge base system that for each design feature, generate all alternative manufacturing processes, and estimate machining time and cost and penetration rate and manufacturability evaluation and select the optimum process for manufacturing design future. This is demonstrated in figure 1. In figure1. Integration of all KBS, in a computer based CE environment is shown. M a r c h 1 7 , 2 0 1 5

EXPERIMENTAL VERIFICATION
A schematic diagram of ECM machine is presented in Fig. 2 and electrochemical machine apparatus is shown in Figure.3.
The work piece was fixed between two metal plates to minimize the over-cut at both sides of the machined hole. During the process, the electrode (tool) makes the penetration movement while the work piece is stationary. According to design features, four types of geometrical tools with cupper material were manufactured including: Circular hole with 10mm,rectangular hole with 10mm width and 12 mm length, fraction disk with internal diameter of 10mm and external diameter of 20mm, and star tool with cross sectional area of 10mm 2 . The tools were coated with an electrical insulating made of nylon with thickness 0.1 mm, bonded with adhesive. Feature based approach is used to capture design features. Typical design feature are used in this research are shown in figure 4.  Table 1.  The sample workpiece material was cast iron, and prepared in the shape of a blank with 50mm wide and 120 mm length, and 20 mm thickness. four types of geometrical tools with cupper material were manufactured including:Circular hole with 10mm, rectangular hole with 10mm width and 12 mm length, fraction disk with internal diameter of 10mm and external diameter of 20mm, and star tool with cross sectional area of 10mm 2 . The operation was an electrochemical drilling. Electrolytic solutions of sodium chloride (NaNO 3 at concentration of 100 g/l) is used. ECM process conditions are as follows: Voltage 15V, Current 175A, Gap between electrodes 0.3mm. The KBS described above was compared with experimental ECM hole drilling. The results for four types of Tool shapes are presented in table2.