UNIT-III Group Technology and Computer Aided Process Planning Group Technology GT is a manufacturing philosophy to increase production effectively bygrouping a variety of parts having similarities of shape, dimension and/orprocess route https://www.youtube.com/watch?v=48szrhv-DzM Part families Collection of parts which are similar either because of geometric shapeand size (or) because similar processing steps are required in themanufacturing. Design Part Family Grouped the parts similar in their design (shape & geometry) characteristics Manufacturing Part Family Grouped the Parts similar in their manufacturing characteristics ( Mfg. Process) Methods for part family formation
Visual inspection Parts classification and coding system Production flow analysis Visual Inspection It involves looking of parts, photos of parts (or) drawings of parts andarranging them into similar groups Parts Classification and Coding System
Coding is a systematic process of establishing an alphanumeric value forparts based on selected part families Most difficult , most time- consuming , most sophisticated and widelyused methods It will vary from one company to another company Coding System Structure
Hierarchical Code Attribute Code Decision tree codes Hierarchical Code (Monocode)
The interpretation of each successive symbol depends on the value ofthe proceeding symbols. Hierarchical Code Example-Spur gear Merits and Demerits It Provides large amount of information relatively small no. of digits Defining the meanings for each digit in a hierarchical system is difficult Attribute Code (Polycode)
The interpretation of each symbol in the sequence does not depend onthe value of preceding symbols Each digit in this code represents information in its own right and doesnot directly qualify the information provided by the other digits Example-Spur Gear Merits and Demerits Polycodes are compact and easy to use
Its lacks in detail as compared to monocode Decision tree codes (Hybrid Code)
Hybrid code Captures the best features of the hierarchical and polycodestructures It combines both design and manufacturing attributes Decision tree codes (Hybrid Code) Reasons for using a coding scheme
Design retrieval Automated process planning Machine cell design Selection of a Coding System
Objective-of the classification system Robustness- Capability of handling all parts Expandability- Ability to cope up with future demands Automation- for computer use Efficiency- the code efficiency, the no. of digits required to code a typicalpart, should be evaluated. Cost- including initial, modifying, interfacing and operational costs Simplicity ease of use training Coding Systems Opitz Classification systems MICLASS Systems
DCLASS System KK-3 System CODE System CUTPLAN System RNC System Part Analog System Brisch System COFORM Opitz Classification systems Production flow analysis (PFA)
Identifying part families and associated machine groupings that uses theinformation contained on production route sheets rather on part drawings Steps involved in Production flow analysis
Data collection- (part no. o/p sequence) Sorting of process routings- (Group technology- Arranging of ProcessTypes) Preparation of PFA chart-Tabulation of a Process of a machine. Cluster Analysis Steps involved in Production flow analysis Facility Design using Group Technology
Line (or product) Layout Functional (or Process ) Layout, and Group (or combination ) layout Line (or product) Layout
Machines are arranged in the sequence as required by the product Functional (or process) Layout
Keeping similar machines/operations at one location Group (or Combination) Layout
Combination of Product layout and process layout https://www.youtube.com/watch?v=VnOFJHkp_UQ Cellular Manufacturing (CM)
Cellular Manufacturing, production work stations and equipment arearranged in a sequence that supports a smooth flow of materials andcomponents through the production process with minimal transport ordelay. Process Planning The product design for the each product developed in designdepartment. To convert the product design into product , a manufacturing plan isrequired. The activity of developing such a plan is called Process Planning An Act of preparing a detailed processing documentation for themanufacture of a piece part or assembly Document Process Planning
Clear in detail about the particular product in form of route andoperation sheet Approaches of Process Planning
1.Manual Process Planning 2.Computer Aided Process Planning i) Retrieval CAPP System ii) Generative CAPP System Manual Process Planning
Merits: Its very much suited for small scale industries It requires low investment costs Demerits: Its time consuming Required skill process planner It increases paper work Computer Aided Process Planning (CAPP)
CAPP- Use of computers in the process planning, one can reduce theroutine clerical work of manufacturing engineers Benefits: Process rationalization and standardization Productivity improvement Product cost reduction Elimination of human error Reduction in time Reduced clerical effort and paper work Faster respond to engineering changes Computer Aided Process Planning (CAPP) Variant (or) Retrieval CAPP Systems
A process plan for a new part is created by identifying and retrieving anexisting plan for a similar part, followed by the retrieving an existing planfor a similar part, followed by the necessary modifications to necessarymodifications to adapt it to the new part. Variant (or) Retrieval CAPP Systems
Variant approach is commonly implemented with GT coding system. Here,the parts are segmented into groups based on similarity and each grouphas a master plan. Advantages Once a standard plan has been written, a variety of components can be planned. Programming and installation are comparatively simple. It is easy to learn and easy to use. Disadvantages The components to be planned are limited to previously planned similar components. Experienced process planners are still required to modify the standard plan for the specific component. Variant planning cannot be used in an entirely automated manufacturing system, without additional process planning. Generative CAPP System
In a generative approach, a process plan for each component is created from scratch without human intervention. These systems are designed to automatically synthesize process information to develop a process plan for a part. (Computer Automatically generates a unique operation/route sheet whenever the part is ordered) Generative CAPP System
Generative CAPP systems contain the logic to use manufacturing data bases, knowledge bases and suitable part description schemes to generate a process plan for a particular part. Advantages and Disadvantages
Consistent process plans can be generated rapidly. New components can be planned as easily as existing components. It has potential for integrating with an automated manufacturing facility to provide detailed control information. The generative approach is complex and very difficultto develop