WHAT IS GROUP TECHNOLOGY? Group technology (GT) is a philosophy that implies the notion of recognizing and exploiting similarities in three different ways:1. By performing like activities together2. By standardizing similar tasks3. By efficiently storing and retrieving information about recurring problems Large manufacturing system can be decomposed into smaller subsystems of part families based on similarities in 1. design attributes and 2. manufacturing features DESIGN ATTRIBUTES: part configuration (round or prismatic) dimensional envelope (length to diameter ratio) surface integrity (surface roughness, dimensional tolerances) material type raw material state (casting, forging, bar stock, etc.) PART MANUFACTURING FEATURES: operations and operation sequences (turning, milling, etc.) batch sizes machine tools cutting tools work holding devices processing times An essential aspect of the integration of CAD and CAM is the integration of information used by engineering and manufacturing and all the other departments in a firm. Group technology emphasis on part families based on similarities in design attributes and manufacturing, therefore GT contributes to the integration of CAD and CAM

The Basic Key Features for a Successful Group Technology Applications: Group Layout Short Cycle Flow Control A Planned Machine LoadingGROUP LAYOUT:In most of todays factories it is possible to divide all the made components into families and all the machines into groups, in such a way that all the parts in each family can be completely processed in one group only. The tree main types of layout are Line Layout Group Layout Functional LayoutLine Layout:Line Layout is used at present in simple process industries, in continuous assembly, and for mass production of components required in very large quantities

Functional Layout:In Functional Layout, all machines of the same type are laid out together in the same section under the same foreman. Each foreman and his team of workers specialize in one process and work independently.This type of layout is based on process specialization

Group Layout: In Group Layout, each foreman and his team specialize in the production of one list of parts and co-operate in the completion of common task. This type of layouts based on component specialization.

The Difference between group and functional layout:

Families :The word Family is used as a name for any list of similar parts. The families used with group layout are lists of parts which are similar because they are all made on the same group of machines. This type of family is called a Production Family. However, not all parts which are similar in shape will appear in the same family. The other important features that is important choosing the families; Manufacturing tolerances Required quantities Materials Special features, which will require the use of different machinesGroups :A group is a list of machines, selected for layout together in one place, because it contains all necessary facilities to complete the processing of a given family of parts. A family of parts can only be defined by relating it to a particular group of machines, and a group by relating it to a family. Groups vary greatly in type and size, widely in the number of machines and different machines types.As group size is reduced, more types of machine will be needed in more than one group and there is an increased risk that some new machines must be purchased. Another factor in choosing the size of group is the number of people who will be employed in themGroup technology begun by grouping parts into families, based on their attributes.

There are three methods that can be used to form part families: Manuel visual inspection Production flow analysis Classification and coding Manual visual inspection involves arranging a set of parts into groups known as part families by visually inspecting the physical characteristics of the parts.

Manual visual inspection incorrect results human error different judgment by different people inexpensive least sophisticated good for small companies having smaller number of parts Production flow analysis: Parts that go through common operations are grouped into part families. The machines used to perform these common operations may be grouped as a cell, consequently this technique can be used in facility layout (factory layout)

Coding methods: are employed in classifying parts into part families Coding refers to the process of assigning symbols to the parts The symbols represent design attributes of parts or manufacturing features of part families The variations in codes resulting from the way the symbols are assigned can be grouped into three distinct type of codes: Monocode or hierarchical code Polycode or attribute Hybrid or mixed code MONOCODE (HIERARCHICAL CODE) This coding system was originally developed for biological classification in 18th century. The structure of monocode is like a tree in which each symbol amplifies the information provided in the previous digit. The following figure illustrates the structure of a monocode: A monocode (hierarchical code) provides a large amount of information in a relatively small number of digits useful for storage and retrieval of design-related information such as part geometry, material, size, etc. it is difficult to capture information on manufacturing sequences in hierarchical manner, so applicability of this code in manufacturing is rather limited POLYCODE (ATTRIBUTE CODE): The code symbols are independent of each other Each digit in specific location of the code describes a unique property of the workpiece it is easy to learn and useful in manufacturing situations where the manufacturing process have to be described the length of a polycode may become excessive because of its unlimited combinational features

Differences in information storage capacity between monocode and polycode: Assume that a code consists of a five symbols and that in each of the five code fields the digits 0 to 9 are used. Determine how many mutually exclusive characteristics can potentially be stored in the monocode and the polycode Number of characteristics may be stored in a monocode: 101 + 102 + 103 + 104 + 105 =111110 Number of characteristics may be stored in a polycode: 10 + 10 + 10 + 10 + 10 = 50 MIXED CODE (HYBRID CODE):It is the mixture of both monocode and polycode systems. Mixed code retains the advantages of both systems. Most coding systems use this code structure. MIXED CODE (HYBRID CODE): The first digit for example, might be used to denote the type of part, such as gear. The next five position might be reserved for a short attribute code that would describe the attribute of the gear. The next digit (7th digit) might be used to designate another subgroup, such as material, followed by another attribute code that would describe the attributes. A code created by this manner would be relatively more compact than a pure attribute code while retaining the ability to easily identify parts with specific characteristics. The OPITZ classification system: it is a mixed (hybrid) coding system developed by Opitz, Technical University of Aachen, 1970 it is widely used in industry it provides a basic framework for understanding the classification and coding process it can be applied to machined parts, non-machined parts (both formed and cast) and purchased parts it considers both design and manufacturing information The Opitz coding system consists of three groups of digits: FormSupplementarySecondary codecodecode 123456789ABCDpart geometry and features relevant to part design .information relevant to manufacturing.(polycode) Production processes and production sequences .

PART FAMILY FORMATION: One of the primary uses of coding systems is to develop part families. Example: Consider the family of ferrous parts formed by first three digits of Opitz form code; 131. This implies that the attributes associated with the family members are length/diameter ratio in the range 0.5 to 3.0, all parts stepped to one end and internal shape elements with threads. A number of mathematical approaches have also been developed to form part families using classification and coding system.

SELECTION OF CLASSIFICATION AND CODING SYSTEMS For the purpose of selecting or developing your own code, it is important to understand the attributes of classification and coding systems. SELECTION OF CLASSIFICATION AND CODING SYSTEMS Some of the important classification and coding system attributes include: 1. Flexibility for various applications such as part family formation, process planning, costing, and purchasing 2. Accuracy, to provide correct information on parts 3. Expandability, to accommodate information on more part attributes deemed important later on 4. Ease of learning 5. Ease of retrieval 6. Reliability and availability of software 7. Suitability for specific applicationsSELECTION OF CLASSIFICATION AND CODING SYSTEMS Matching these attributes with the objectives of an organization would be helpful in selecting or developing a coding system to meet organizational needs.BENEFITS OF GROUP TECHNOLOGY Group technology is a management strategy to help eliminate waste caused by duplication of effort. BENEFITS OF GROUP TECHNOLOGYIt affects all areas of a company, including: engineering equipment specification facilities planning process planning production control quality control tool design purchasing service Some of the well-known tangible and intangible benefits of implementing GT : 1. Engineering design Reduction in new parts design Reduction in the number of drawings through standardization Reduction of drafting effort in new shop drawings Reduction of number of similar parts, easy retrieval of similar functional parts, and identification of substitute parts 2. Layout planning Reduction in production floor space required Reduced material-handling effort 3. Specification of equipment, tools, jigs, and fixtures Standardization of equipment Implementation of cellular manufacturing systems Significant reduction in up-front costs incurred in the release of new parts for manufacture 4. Manufacturing: process planning Reduction in setup time and production time Alternative routing leading to improved part routing Reduction in number of machining operations and numerical control (NC) programming time 5. Manufacturing: production control Reduced work-in-process inventory Easy identification of bottlenecks Improved material flow and reduced warehousing costs Faster response to schedule changes Improved usage of jigs, fixtures, pallets, tools, material handling, and manufacturing equipment 6. Manufacturing: quality control Reduction in number of defects leading to reduced inspection effort Reduced scrap generation Better output quality Increased accountability of operators and supervisors responsible for quality production, making it easier to implement total quality control concepts. 7. Purchasing Coding of purchased part leading to standardized rules for purchasing Economies in purchasing possible because of accurate knowledge of raw material requirements Reduced number of part and raw materials Simplified vendor evaluation procedures leading to just-in-time purchasing 8. Customer service Accurate and faster cost estimates Efficient spare parts management, leading to better customer service

CELLULAR MANUFACTURINGCellular manufacturing is an application of group technology in manufacturing in which all or a portion of a firms manufacturing system has been converted into cells. CELLULAR MANUFACTURING:A manufacturing cell is a cluster of machines or processes located in close proximity and dedicated to the manufacture of a family of parts. The parts are similar in their processing requirements, such as operations, tolerances, and machine tool capacities The primary objectives in implementing a cellular manufacturing system are to reduce: setup times (by using part family tooling and sequencing) flow times (by reducing setup and move times and wait time for moves and using smaller batch sizes) reduce inventories market response times In addition, cells represent sociological units that have more tendency to teamwork. This means that motivation for process improvements often arises naturally in manufacturing cells. Manufacturing cells are natural candidates for just-in-time (JIT) implementation. Functional and cellular layouts of an electronics plant:

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Introduction to Cellular Manufacturing: Cellular Manufacturing is an application of group technology in which dissimilar machines or processes have be aggregated into cells, each of which is dedicated to the production of a part or product family or a limited group of families.Benefits of Cellular Manufacturing:

Composite Part Concept: A Composite Part for a given family, which includes all of the design and manufacturing attributes of the family. In general, an individual part in the family will have some of the features that characterize the family but not all of them. The composite part possesses all of the features

Machine Cell Design: Design of the machine cell is critical in cellular manufacturing. The cell design determines to a great degree the performance of the cell.Types of machine cells and layouts: GT manufacturing cells can be classified according to the number of machines and the degree to which the material flow is mechanized between machines. Four common GT cell configurations:1. Single machine cell (Type I M)2. Group machine cell with manual material handling (Type II M generally, Type III M less common)3. Group machine cell with semi-integrated handling (Type II M generally, Type III M less common).4. Flexible manufacturing cell or flexible manufacturing system (Type II A generally, Type III A less common)Machine Cell Design: Single machine cell consists of one machine plus supporting fixtures and tooling. This type of cell can be applied to workparts whose attributes allow them to be made on one basis type of process, such as turning or milling.

Machine Cell Design: Group machine cell with manual handling is an arrangement of more than one machine used collectively to produce one or more part families. There is no provision for mechanized parts movement between the machines in the cell. Instead, the human operators who run the cell perform the material handling function. The cell is often organized into a U-shaped layout.

U shaped layout,Machine Cell Design: Group machine cell with semi-integrated handling uses a mechanized handling system, such as a conveyor, to move parts between machines in the cell.

(a)in-line layout(b)loop layout(c)rectangular layoutMachine Cell Design: Flexible manufacturing system combines a fully integrated material handling system with automated processing stations. The FMS is the most highly automated of the Group Technology machine cells.

Machine Cell Design:2- Types of part movements Determining the most appropriate cell layout depends on the routings of parts produced in the cell. Four types of part movement can be distinguished in a mixed model part production system.

1. Repeat Operation, in which a consecutive operation is carried out on the same machine, so that the part does not actually move.2. In-sequence move, in which the part move from the current machine to an immediate neighbor in the forward direction.3. By-passing move, in which the part moves forward from the current machine to another machine that is two or more machines ahead.4. Backtracking move, in which the part moves from the current machine in the backward direction to another machine.