Group Technology: A Manufacturing Philosophy for Enhanced Integration, Lecture notes of Computer Aided Design (CAD)

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UNIT IV

GROUP TECHNOLOGY

Group Technology

• Group technology emphasizes on part families based on similarities therefore in design attributes and manufacturing, GT contributes to the integration of CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing).

Implementing Group Technology(GT)

• There are two major tasks that a company must undertake when it implements Group Technology 1.Identifying the part families. If the plant makes 10 , 000 different parts, reviewing all of the part drawings and grouping the parts into families is a substantial task that consumes a significant amount of time. 2.Rearranging production machines into cells. It is time consuming and costly to plan and accomplish this rearrangement, and the machines are not producing during the changeover.

1.Visual Inspection Method

• The visual inspection method is the least sophisticated and least expensive method.
• It involves the classification of parts into families by looking at either the physical parts or their photographs and arranging them into groups having similar features.

3.Production Flow Analysis

1. This method makes use of the information contained on route sheets rather than on part drawings.
2. Work – parts with identical or similar routings are classified into part families. The procedure of production flow analysis is as follows: I. Data collection : The data such as part number and operation sequence is collected from manufacturing data contained in the route sheets. II. Sorting: The parts are separated and arranged into groups according to similar or identical routings. III. Preparation of chart : a) The chart is a tabulation of the process or machine code numbers for all the parts of a part family. b) In this tabulation , the entries are cross marked (X). c) The cross mark (X) indicates I th part requiring j th machine. d) If X ij = 0 , there is no processing of the ith part on the jth machine.

Production Flow Analysis (PFA)

• Production flow analysis (PFA) is a method for identifying part families and associated machine groupings that uses the information contained on process plans rather than on part drawings.
• Work parts with identical or similar process plans are classified into part families. These families can then be used to form logical machine cells in a group technology layout.
• The procedure in production flow analysis must begin by defining the scope of the study, which means deciding on the population of parts to be analyzed.

4. Parts classification and Coding

• In parts classification and coding, similarities among parts are identified, and these similarities are related in a coding system.
• This classification and coding may be carried on the entire list of parts of a family.
• Two categories of part similarities can be distinguished: 1.Design attributes,which concerned with part characteristics such as geometry, size and material. 2 .Manufacturing attributes, which consider the sequence of processing steps required to make a part.

Types classification and coding

1. Classification of parts refers to grouping of parts on the basis of the essential features of parts
2. Coding is the process of assigning symbols to the parts. this symbols may represent design attributes or manufacturing attributes or both. A) Parts Classification Schemes:

B) Coding Schemes: Coding systems use Number digits. There are 3 basic codes structures used in GT applications. 1.Hierarchical structure. 2.Chain – type structure. 3.Hybrid structure.