Flexible Manufacturing System
Flexibility entails to produce equitably priced customized products of superior quality that can be rapidly delivered to clienteles. In manufacturing system flexibility refers to the capability of producing different parts without major retooling and it is a measure of how fast the company converts its process from making an old line of products to produce a new product. Flexibility is the ability to change a production schedule, to change a part, or to handle multiple parts. Flexible manufacturing systems are technologies that combine the benefits of both computers and numerical control machine tools. They have been addressed as the solution to challenges that manufacturing industries facing at global scale.
Reviewing the past literature, it is found that notion of flexibility in manufacturing system was extensively studied overtime. The concept of flexible manufacturing systems grew during the 1960’s when robots, programmable controllers, and computerized numerical controls brought an environment to the factory floor in the form of numerically-controlled and direct-numerically-controlled machines. It was initially defined as a manufacturing system’s ability to respond to changes in customer requirements without penalizing, cost, time effort and performance to any great degree (Upton, 1994). Several theorists stated that flexibility is necessary element for coping with internal and external disturbances. It can also be seen as measurement for numerous product variants that manufacturing system can manage. The measurement of flexibility cannot be performed on an absolute scale but must be seen as a relative measure (Mitsuishi, et, al., 2008).
The main objective of a flexible manufacturing system is to offer the speed needed to change with market conditions quickly, but not sacrifice any quality.
Flexibility studies have focused on production environments and inter organizational elements such as mix, volume, and product and production routes. Sharifi and Zhang determined that flexibility was not sufficient to address new market challenges market by intense competitive environment (1999). It also provided the research theoretical model linking flexible manufacturing competencies with volume flexibility, mix flexibility and customer satisfaction (Tullio Tolio, 2008).
Framework proposed by Zhang, et, al. (Source: Tullio Tolio, 2008)
Browne et al., 1984 defines flexibility in manufacturing system as an integrated computer-controlled system with automated material handling devices and CNC machine-tools and which can be used to simultaneously process a medium-sized volume of a variety of parts. Chan et al. (2007) offered a simulation study using Taguchi’s method analysis of physical and operating parameters of the flexible manufacturing system along with flexibility. An approach is developed to study the impact of variations in the physical and operating parameters of flexibility in manufacturing system and to identify the level of these variations. The physical and operating parameters of alternative resources may influence the system’s performance with the changing levels of flexibility and operational control parameters such as scheduling rules. Various results of simulation study demonstrates that predictable benefits may not be present when routing flexibility levels are increased with presence of the variations in physical and operating parameters. The increase in routing flexibility level becomes counterproductive under such environment when variations are above certain limits. It may be useful for decision maker to distinguish the level of flexibility up to which it can be gainfully increased under the presence of variations.
Sarker et al. (1994) have offered a thorough classification for the types of manufacturing related flexibility as follows: Routing flexibility, machine, flexibility, process flexibility, expansion flexibility, job flexibility, design flexibility, material handling flexibility, setup time flexibility, and volume flexibility. Bolwijn and Kumpe (1990) and De Meyer et al. (1989) have recognized flexibility’ as the focus of the next competitive battle.
Other group of theorists also explained the notion of flexibility in their terms. Gupta and Buzacott (1989) elucidated that the flexibility does not come from the abilities of machine alone. Actually flexibility is the consequence of amalgamation of factors like physical characteristics, operating decisions, information integration, and management practice. Flexibility is critical in providing the effectiveness to manufacturing system under different operating conditions. Bennett et al. (1992) recognises the factors crucial to the development of efficient flexible production systems, namely: effective integration of subsystems, development of appropriate controls and performance measures, compatibility between production system design and organization structure, and argues that the flexibility cannot be potentially exploited if its objectives are not defined and considered at design stage. Kumar et al. (2003) used an ant colony optimization approach for scheduling of flexibility in manufacturing system for a given level of flexibility. Wang and Yen (2001) measured the transportation times in automated material handling system for simulation study of dispatching rule performance.
Though there is confusion among theorists about occurrence of flexibility. Gerwin (1993) proposes that the lack of clear understanding of manufacturing flexibility is inhibiting progress towards the utilization of flexibility concepts in industry and hindering manufacturing managers from evaluating and changing the flexibility of their operations. Gunasekaran et al. (1993) and Gerwin (1993) recognised the measurement of flexibility and performance as an important obstacle to realize a full comprehension of flexible manufacturing system behaviour.
Vast amount of theoretical studies have focused on the concept of flexibility in manufacturing system. Flexible manufacturing system is a class of manufacturing system that can be speedily configured to produce various products. Since last few decades, the modelling and the analysis of flexibility in manufacturing system has been closely studied by control theorists and engineers. A flexibility in manufacturing system is a production system where a discrete number of raw parts are processed and assembled by controlled machines, computers and/or robots (Ruiz et al., 2009).
There are three abilities that a manufacturing system must retain in order to be flexible:
- The ability to identify and distinguish among different incoming part or product styles processed by the system.
- Quick changeover of operating instructions.
- Quick changeover of physical setup.
Flexible manufacturing system of organization
The classification of flexibility types established by Browne et al. (1984) who has formed the foundation of most consequent research into measuring manufacturing flexibility
It has been recognised in literature that there are three levels of manufacturing flexibility.
1. Basic flexibilities:
Machine flexibility: It basically refers to the various types of operations that the machine can perform without requiring prohibitive effort in switching from one operation to another (Sethi and Sethi, 1990).
Material handling flexibility: A measure of the ease with which different part types can be transported and properly positioned at the various machine tools in a system.
Operation flexibility: A measure of the ease with which alternative operation sequences can be used for processing a part type. It is the ability to interchange the sequence of manufacturing operations for a given part.
2. System flexibilities:
Volume flexibility: A measure of a system’s capability to be operated profitably at different volumes of the existing part types. It is the ability to operate profitably at different production volume.
Expansion flexibility: The ability to build a system and expand it incrementally. It is the ability to expand the capacity of the system as needed, easily and modularly.
Routing flexibility: A measure of the alternative paths that a part can effectively follow through a system for a given process plan. It is the ability to vary the path a part may take through the manufacturing system.
Process flexibility: A measure of the volume of the set of part types that a system can produce without incurring any setup. It is the ability to change between the productions of different products with minimal delay.
Product flexibility: The volume of the set of part types that can be manufactured in a system with minor setup. It is the ability to change the mix of products in current production, also known as mix-change flexibility (Carter, 1986).
3. Aggregate flexibilities:
Program flexibility: The ability of a system to run for reasonably long periods without external intervention.
Production flexibility: The volume of the set of part types that a system can produce without major investment in capital equipment.
Market flexibility: The ability of a system to efficiently adapt to changing market conditions.
Table: Types of flexibility in manufacturing
|Flexibility Type||Definition||Depends on factors such as|
|Machine Flexibility||Capacity to adapt a given machine (work station) in the system to wide range of production operations and part styles. The greater the range of operations and part styles, the greater the machine flexibility.||Setup or changeover time.
Ease of machine reprogramming (ease with which part program can be downloaded to machne)
|Production Flexibility||The range or universe of part styles that can be produced on the system.||Machine flexibility of individual stations. Range of maching flexibilities of all stations in the system.|
|Mix Flexibility||Ability to change the product mis while maintaining same total production quatity that is producing the same parts only in different proportions.||Similarity of parts in the mix. Relative work content times of parts produced. Machine flexibility.|
|Product Flexibility||Ease with which design changes can be accomodated. Ease with which new products can be introduced.||How closely now part design matches the existing part family.
Offline part program preparation.
|Routing Flexibility||Capcity to produce parts through alternative work station sequences in response to equipment breakdowns, toools failures and other intruptions at individual stations.||Similarity of parts in the mix.Similarity of work stations.
Duplicatoions of work stattions.
Cross training of material workers.
|Volum.e 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 investment.
|Expansion Flexibility||Ease with which the system can be expanded to increase total production quantities.||Expense of adding workstations.
Ease with which layout can be expanded.
Type of part handling sytem can be used.
Ease with which property trained workers can be added.
In order to qualify as being flexible, the automated system should clear four tests:
- Part variety test.
- Schedule change test.
- Error recovery test.
- New part test.
In recent years, the flexibility manufacturing system has arisen as one of the upheavals in the manufacturing industries. It has made it conceivable to produce a variety of parts in less time and cost. The use of FMS in the current market setting can satisfy the increasing demands of variety, quantity and speed at the same time. The components of the flexibility manufacturing system can be categorized in to two parts:
- Hardware: Machine tools, handling systems, guided vehicles, inspection centre, robots, etc.
- Software: Software for FMS can further be classified into extrinsic and intrinsic functions.
Major benefits of a flexible manufacturing system is the change to adapt the operation to fulfil emerging demands for certain products by customers. Flexibility in manufacturing system enable the business to capture a significant market share and increase revenues for as long as the demand for those products remains in place. Another benefit of a flexible manufacturing system is the chance to minimize labour costs during seasonal recessions, and then increase the labour force during busy seasons. This approach can be realised by cross training employees who can take on additional responsibilities during lean seasons, then turn a portion of those responsibilities over to part-time personnel during busy seasons. The end result is well-organized operation that still helps to keep the cost of production for each unit produced under a certain level.
Main drawback of flexible manufacturing system is that this type of arrangement often has a significant up-front cost, since machinery may have to be modified to allow for an easier conversion of goods produced. This process often lead to changing the corporate culture, a process that can take a lot of time and result in some loss of efficiency in the short-term. Technological barriers may also slow the efforts to be more adaptable, requiring additional planning to overcome those obstacles and creating additional expense for the company. Many researches raised concern that this type of system can only handle a relatively-narrow range of part varieties, so it must be used for similar parts that require similar processing. Due to increased intricacy and cost, flexible manufacturing system also requires a longer planning and development period than traditional manufacturing equipment.
It can be said that initiation of focused flexibility may represent an important means to rationalize the way by which flexibility is embedded in manufacturing system. Flexible manufacturing systems are extensively used to improve productivity and quality of the product. It also improves the quality of life for the operator. The new techniques will have a major impact on economic factors.