INTRODUCTION TO FMS. Type of Automation. 1. Fixed automation 2. Programmable automation 3. Flexible automation Fixed Automation

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1 Type of Automation 1. Fixed automation 2. Programmable automation 3. Flexible automation Fixed Automation INTRODUCTION TO FMS Sequence of processing (or assembly) operations is fixed by the equipment configuration Each of the operation in the sequence is usually simple, involving perhaps a plain linear or rotational motion or an uncomplicated combination of the two High initial investment for custom-engineered equipment High production rates Relatively inflexible in accommodating product variety Eg:- Machining transfer lines and automated assembly lines Programmable Automation Production equipment is designed with the capability to change the sequence of operation to accommodate different product configurations A program controls operation sequence Program is a set of instructions coded so that they can be read and interpreted by the system Suitable for low-and mid-volume production Most suitable for batch production To produce new batch of a different product, tools must be loaded, fixtures must be attached to the machine table, the required machine setting must be entered, and the system must be reprogrammed High investment in general-purpose equipment Lower production rate than fixed automation Eg:- NC machine tools, Industrial Robots and Programmable logic controllers Flexible Automation A flexible automated system is capable of producing a variety of parts (or products) with virtually no time lost for changeovers from one part style to the next Possible when the difference between parts processed by the system are not significant High investment for custom-engineered system Continuous production of variable mixtures of products Medium production rates Flexibility to deal with product design variations Eg:- FMS Introduction to FMS 158 March 2013

2 FLEXIBILITY It is the ability of the system to respond effectively to both internal and external changes Manufacturing system flexibility is depending on the versatility of the equipment and the way equipment is managed The capabilities required for a manufacturing system to be flexible are: Identification of the different units Quick changeover of operating instructions Quick changeover of physical setup Flexibility is an attribute that applies to both manual and automated systems In manual systems, the human workers are often the enablers of the flexibility of the system Internal changes or disturbances: Breakdown of equipment, variability in processing times, worker absenteeism, and quality problems To cope with internal changes requires degree of redundancy in the system External changes: Changes in design, demand, and product mix To cope with, the system should be versatile and capable of producing a wide variety of part types with minimal changeover times and costs to switch from one product to another Flexibility is fundamental to achieve competitiveness as time to process an order and the product variety that can be produced will decide the competitiveness Flexibility in the Context of Various Types of Manufacturing Systems Transfer lines Very inflexible and will not tolerate variations in part design Failure of any of the machines would bring down the entire line No choice in choosing the machine for next operation Job Shop Following points shows the flexible capabilities of a job shop Versatile machine tools and skilled manpower Have similar machines in several numbers Skilled worker can perform design, drafting, process planning, and machining operations However, in a typical job shop lead times are very high Suffer from large manufacturing lead time and high WIP Introduction to FMS 159 March 2013

3 Flexible Manufacturing System (FMS) An FMS can be defined as an integrated computer controlled configuration of NC machine tools, other auxiliary production equipment, and a material handling system designed to simultaneously manufacture low to medium volumes of a wide variety of high quality products at low cost An FMS is capable of processing a variety of different part styles simultaneously at the various workstations, The mix of part styles and quantities of production can be adjusted in response to changing demand patterns FMS is the most automated and technologically sophisticated GT cell No manufacturing system can be completely flexible Limits to the range of parts or products that can be made in an FMS FMS is designed to produce parts (or products) within a defined range of styles, sizes, and processes Situations suitable for FMS applications Presently, the plant either (1) produces parts in batches or (2) uses manned GT cells and management wants to automate It must be possible to group a portion of the parts made in the plant into part families, whose similarities permit them to be processed on the machines in the FMS The parts or products made by the facility are in the mid-volume, mid variety production range The appropriate production volume range is ,000 parts per year Below this range FMS is an expensive alternative Above this range more specialized system may be suitable Four reasonable test of flexibility in an automated manufacturing system Part variety test Scheduled change test Error recovery test New part test Types of Flexibility Machine flexibility The ease with which a machine (workstation) can change over from one part type to another The greater the range of operation and part styles, the greater the machine flexibility The change over time generally involves setup, tool changing, part-program transfer, and transportation times Introduction to FMS 160 March 2013

4 The change over time could be fraction of the processing to the orders of magnitude greater than the processing time Changeover time is a function of the machine centre capabilities as well as effectiveness of its management Also depend upon the skill and versatility of workers in the system Production flexibility The range or universe of part styles that can be produced on the system the machine flexibility of individual stations and range of machine flexibility of all stations in the system Product-mix flexibility Ability to change the product mix while maintaining the same total production quantity Similarity of parts in the mix Relative work content times of parts produced Machine flexibility Product flexibility Ease with which design changes (new design) can be introduced How closely the new part design matches the existing part family Off-line part program preparation Machine flexibility Routing flexibility Ability to produce the given set of part types in required volume in the face of failures and breakdowns Each part could be manufactured via several routes and each operation could be performed on more than one machine Similarity of parts in the mix Similarity of workstations Spare capacity Cross-training of manual workers Operation flexibility Ability to interchange the ordering of several operations for each part type Operation flexibility is part dependent and it increases the number of alternate routes that a part can flow through on the factory floor Introduction to FMS 161 March 2013

5 Generally operation planners do not exploit this flexibility and they fix the ordering of all operations Volume flexibility Ability to economically produce parts in high and low total quantities of production, given the fixed investment in the system Level of manual labour performing production Amount invested in capital Expansion flexibility Ease with which system can be expanded to increase total production quantities Expense of adding workstations Ease with which layout can be expanded Type of part handling system used Ease with which properly trained workers can be added Types of FMS Based on Kind of Operation Processing operation Rotational parts Nonrotational parts Flexible machining systems with multiple stations that process rotational parts are much less common than system that process nonrotational parts Assembly operation Based on Number of Machines Single machine cells Flexible manufacturing cell Flexible manufacturing system Single machine cell Consists of one CNC machining centre combined with a parts storage system for unattended operation Cell can be designed to operate in either a batch mode or a flexible mode or in combinations of the two Flexible manufacturing cell Consists of two or three processing workstations plus a part handling system connected to a load/unload station Introduction to FMS 162 March 2013

6 Flexible manufacturing system Four or more processing workstations connected by a part handling system and electronically by a distributed computer system Generally includes nonprocessing stations such as part/pallet washing stations, coordinate measuring stations Based on Level of Flexibility Dedicated FMS Random-order FMS Dedicated FMS (Special manufacturing system) Limited variety of part styles and the complete universe of parts to be made on the system are known in advance Part family is likely to be based on product commonality rather than geometric similarity Certain amount of process specialization can be incorporated to make the operation more efficient Machines can be designed for special processes Sequence may be identical or nearly identical for all parts processed So a transfer line may be appropriate with workstations that have flexibility to process the different parts in the mix flexible transfer line Random-order FMS Appropriate when The part family is large Substantial variations in part configurations Frequently new part designs are introduced Engineering changes are frequent Production schedule changes from day-to-day Required more sophisticated computer control system QUESTIONS: 1. Distinguish between programmable automation and flexible automation 2. Distinguish between programmable automation and fixed automation 3. What are the manufacturing situations suitable for FMS implementation? 4. What capabilities are the enablers of flexibility in manufacturing system? Introduction to FMS 163 March 2013

7 5. What is production flexibility? What is the level of machine flexibility required to obtain good production flexibility? 6. What is product-mix flexibility? 7. What is fixed automation? Give a note on degree of flexibility and production rate of this type of automation. 8. What is flexibility? Compare the transfer lines and job shops based on flexibility. Introduction to FMS 164 March 2013