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Machine Tools
Published in David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, 2018
David A. Stephenson, John S. Agapiou
A flexible transfer line (FTL) is a production system designed for high-volume production, which is capable of producing a family of similar parts with unplanned changes or additional machined content. The life cycle of individual parts can vary from a few to several years as long as there is sufficient flexibility to fully utilize the system for 10–15 years. Such systems allow new products of the same family to be introduced quickly without major retooling. The changeover time between different products is usually a few hours, depending on the number of workstations involved and the available flexibility. Flexible transfer machines are well suited to applications in which a few similar parts are required in high volumes (e.g., >50,000/year), as is often the case in automotive powertrain and component production. Flexible transfer lines require a significant initial investment premium compared to conventional transfer machines and still require accurate part planning and market forecasts to operate economically. Currently, flexibility is commonly accomplished by using machining stations with indexable heads (turrets) or shuttle heads, each fitted with a number of different tools. CNC machines have also been used in FTLs, making them similar to the agile production systems described in the next section, although machine layout (serial vs. parallel) is generally different from that in an agile cell. In addition to requiring a significant premium in initial investment, flexible systems increase machine structural and fixture complexity and often required tooling and gaging inventories.
Focused Factories and Group Technology
Published in John Nicholas, Lean Production for Competitive Advantage, 2018
Continuous/repetitive production and product layouts go together. Only one or a few kinds of end items are produced, and they all follow the same routing sequence through the line. Work scheduling in a product layout consists of determining the flow rate or cycle time necessary to satisfy demand, and then designing the line so it produces at that rate. Since material moves continuously from operation to operation and neighboring operations are adjacent, there is little or no inventory waiting between operations. Throughput time per unit is not much more than the processing time in the line. Material handling consists of transferring items from one operation to the next; the transfer can be automated or, for small, light items, manual. On a fully mechanized transfer line, material at each machine is automatically loaded, machined, unloaded, and moved to the next machine.
Discrete Event Control of Manufacturing Systems
Published in Osita D. I. Nwokah, Yildirim Hurmuzlu, The Mechanical Systems Design Handbook, 2017
D.M. Tilbury, P.P. Khargonekar
A transfer line is a manufacturing system used for high-volume machining operations, for example, automotive engine blocks. Generally, a transfer line is composed of 4 to 12 machining stations; the operation of the system is governed by event sequences within the stations as well as dependencies across the stations. In devising control algorithms for such a machining system, it is necessary to consider not only the sequence of each station but also the correlated sequences of the whole system. An example of a transfer line is shown in Figure 3.3. The system has 15 stations, consisting of 4 mills, 3 clamps, a cradle, and a rotating table. Not all stations are used; the extra space is needed to provide access to the machines for maintenance and repair. The engine blocks move through the machine via a transfer bar from station 1 to station 15. At station 6, they are reoriented.
A new approach to the analysis of homogeneous transfer lines with unreliable buffers subject to time-dependent failure
Published in International Journal of Production Research, 2020
Beixin Xia, Chen Wang, Ya Gao, Yunfang Peng, Lei Liu
Transfer lines are widely used in modern manufacturing systems, especially when high production rates are demanded. It is a difficult task to design an efficient transfer line. Some of the many sources of randomness in transfer lines are variations in processing time, time between failures and time to repair. Such randomness can impair line productivity and translate to utilisation loss. A common strategy is to place buffers between machines to absorb such randomness. However, one side effect of this strategy is an increased difficulty in establishing transfer line performance metrics such as production rate, work-in-process (WIP) level or bottlenecks. Although a rich body of research has been devoted to this topic, most existing methods focus on machine behaviour and rely on the assumption that buffers are finite and always reliable. This assumption is questionable because, in practice, buffers can break down and have a significant impact on the process (Li et al. 2009; Hudson, McNamara, and Shaaban 2015).
Scenario-based robust dominance criteria for multi-objective automated flexible transfer line balancing problem under uncertainty
Published in International Journal of Production Research, 2020
Cong He, Zailin Guan, Guangyan Xu, Lei Yue, Saif Ullah
The AFTL (He, Guan, Yue, et al. 2018) consists of several stages performing different set of operations, and each stage is composed of several machining cells, which is shown in Figure 1. Each machining cell is formed by several machines and single robot. The machining cells in the same stage are assigned with the same set of operations with total processing time , and the robots in the cell perform auxiliary processing time . This kind of transfer line has advantages over general production lines with high flexibility, reliability and reconfigurability, due to its special structure. The abbreviations and notations used in the paper are introduced here.