of Group Technology (GT) and the use of Group Technology (GT) is a concept to increase production efficiency by grouping various parts and products with similar design and/or manufacturing process. Introduction Group technology (GT) is a manufacturing philosophy that identifies and exploits the underlying sameness of parts and manufacturing processes The principle has been applied in many fields including part design retrieval, process planning, machine cell design, facility layout, scheduling, etc. For a company whose product types are variant and production lot size small or medium, the advantages of implementing GT include enhanced ability to adapt to quick market changes, reduced throughput time, reduced production costs, reduced varieties of product design and process planning, and promoted part and process standardization multi-product and small-lot-sized production system or batch-type manufacturing. But the The implementation of GT concept to This study is focused on the implementation of GT to the aspect numerical control (NC) programming of turning centers. The will be used to develop a NC program for each part family. create the opportunity to generate NC codes and operate CNC machines with greater efficiency Nowadays, because of the development of computer science, the need for computer integration of whole creation process has appeared. Computer aided classification which is closely connected with the This method involves checking the condition part of a rule to determine whether it is true or false. If the condition is true, then the action part of the rule is also true. This procedure continues until solution is found or a dead end is reached [7]. Methodology The main activity of Part family grouping is an important step for successful GT applications. A part family may be grouped with the parts having similar design features such as geometric shape, size, and materials and so on. A part family also may be grouped with respect to production operations: machines, processes, operations, tooling and so on. Grouping is separate part programs are written for individual parts within a part family. Then the programs are loaded to the controller one-by-one. parametric programming, also referred to as macro, in which a part program can be written using variables and parametric expression to represent This programming allows the user to load a single part for a family of parts to the CNC controller. The part program is then called for machining a similar part or similar feature on different parts by entering the Upon loading the main program, the values of the two parameters are entered, and then these values are transferred to parametric subprograms. This method could minimize the number of program changeovers, reduce redundant codes and shorten the length of the program According to the definition, classification is the process of categorizing parts into groups on the basis of the proper set of rules and principles. The classification and codification system assigns code to part. Based on these codes, parts can be grouped into part families. Each part family corresponds to a group of machines. Lot of classification methods has been elaborated. Coding and processing of coded information about classified elements are the main principles of functioning of this method. Different methods of classification used different types of algorithms. The most often used algorithms are among others: hierarchical, in this study parts are divided into some classes as The structure of the coding scheme, which consists of three classes /levels, automation of process planning requires the use of computer systems to perform process planning tasks, such as the selection of the size of raw materials, the machines, the cutting tools, the cutting speed, the feed rate, the depth of cut and the machining sequence. The expert system technique has been implemented in the field of computer aided process planning (CAPP). An expert system is a computer program that simulates human expert(s) in making decisions and solving problems. Expert systems have advantages over the traditional computer systems for the following reasons: (i) Expert systems organize knowledge in rules and control strategy which allow users to modify a program with ease; (ii) Expert systems organize knowledge in a way such that they can reason intelligently, thus, expert systems are able to deal with far more complicated problems; (iii) Expert systems can be designed so that they accumulate knowledge as time passes. Knowledge representation The knowledge must be organized in an easily accessible format that distinguishes between data, knowledge, and control structures. So that, expert systems are organized in three distinct levels: knowledge base, knowledge base consists of problem solving rules, procedures, and intrinsic data relevant to the problem domain. User User interface module Knowledge base Inference Engine Working memory Knowledge acquisition module Expert Working memory refers to task specific data for the problem under consideration. While inference engine is a generic control mechanism that applies the axiomatic knowledge in the knowledge base to the task-specific data to arrive at some solution. Figure 1 represents the expert systems structure. The is satisfied by the conditions, the action specified by the THEN portion is performed. This is called ‘fire’ situation. A rule interpreter compares the IF portion of each rule with the facts and executes the rules whose IF portions match the facts. The inference engine of an expert system is very important because it controls how to reach a conclusion, i.e. the inference engine determines the sequence in which rules are applied. The inference engine controls the process knowledge in the knowledge base to solve the problems of the selection of the process, the selection of the G Code and the selection of the cutting starts with a set of facts or data and to look for those rules in the knowledge base for which the IF portion matches the facts. When such rules are found, one of them is selected based upon an appropriate criterion and After a rule fires, the GT Expert System executes the rule’s actions. Now the knowledge base might make some alteration. Then, the rules will be checked again against the facts and criterion in the knowledge base. This generates new facts in the knowledge base, which in turn causes other rules to fire. The a computer program written with the Visual Basic 6.0 language. component’s design information and store the code in the knowledge base for other modules to generate the process plan. The coding module provides guidance to the