Performance comparison of assembly systems with fixed and flexible cycle times

The traditional assembly system consists of a series of balanced workstations operating at the same rate with fixed cycle times. Recent advances in technology allow more flexible assembly systems, in which workstations operate independently and cycle times vary from job to job.This article develops an analytical model for comparing the throughputs (jobs per hour) of assembly systems with fixed and variable cycle times. The throughputs are compared on a common basis by requiring that both systems allow sufficient processing time to ensure product quality and that they have the same total times in system per job.Results indicate that an assembly system with variable cycle times can operate at a significantly higher throughput than one with fixed cycle times, provided there is sufficient buffer storage space between workstations to accommodate queueing. This benefit must be weighed against possible increased capital investment and practical considerations associated with system control.

[1]  David Eugene Smith,et al.  A source book in mathematics , 1930 .

[2]  J. A. Buzacott,et al.  AUTOMATIC TRANSFER LINES WITH BUFFER STOCKS , 1967 .

[3]  K. G. Swift,et al.  Design for assembly , 1983 .

[4]  J. Little.  A Proof for the Queuing Formula: L = λW , 1961 .

[5]  W. Whitt,et al.  The Queueing Network Analyzer , 1983, The Bell System Technical Journal.

[6]  Manjunath Kamath,et al.  Analytical performance models for closed-loop flexible assembly systems , 1988 .

[7]  We-Min Chow,et al.  Buffer capacity analysis for sequential production lines with variable process times , 1987 .

[8]  John A. Buzacott,et al.  Abandoning the moving assembly line: models of human operators and job sequencing , 1990 .

[9]  Carlos F. Daganzo,et al.  IMPACT OF PARALLEL PROCESSING ON JOB SEQUENCES IN FLEXIBLE ASSEMBLY SYSTEMS , 1989 .

[10]  Ilker Baybars,et al.  A survey of exact algorithms for the simple assembly line balancing , 1986 .

[11]  Robert B. Cooper,et al.  Introduction to Queueing Theory , 1973 .

[12]  G. Boothroyd.  Economics of assembly systems , 1982 .

[13]  K. T. Marshall,et al.  Some Inequalities in Queuing , 1968, Oper. Res..

[14]  Carlos F. Daganzo,et al.  Assembly line job sequencing principles , 1987 .

[15]  William L. Maxwell,et al.  The Role of Work-in-Process Inventory in Serial Production Lines , 1988, Oper. Res..

[16]  Rajan Suri,et al.  An overview of evaluative models for flexible manufacturing systems , 1985 .

[17]  Ward Whitt,et al.  The Best Order for Queues in Series , 1985 .

[18]  Norman A. Dudley,et al.  WORK-TIME DISTRIBUTIONS , 1963 .

[19]  Toshikazu Kimura.  A two-moment approximation for the mean waiting time in the GI/G/s queue , 1985 .

[20]  Kathryn E. Stecke,et al.  Design, planning, scheduling, and control problems of flexible manufacturing systems , 1985 .

[21]  J. A. Buzacott,et al.  Flexible manufacturing systems: a review of analytical models , 1986 .

[22]  R. N. Basu,et al.  The interstage buffer storage capacity of non-powered assembly lines A simple mathematical approach , 1977 .

[23]  Fred N. Silverman,et al.  A Cost-Based Methodology for Stochastic Line Balancing with Intermittent Line Stoppages , 1986 .

[24]  E. Muth.  The production rate of a series of work stations with variable service times , 1973 .

[25]  Stanley B. Gershwin,et al.  An Efficient Decomposition Method for the Approximate Evaluation of Tandem Queues with Finite Storage Space and Blocking , 1987, Oper. Res..

[26]  K. Knott.  A Study of Work-Time Distributions on Unpaced Tasks , 1987 .

[27]  J. A. Buzacott,et al.  On the approximations to the single server queue , 1980 .

[28]  D. Kendall.  Some Problems in the Theory of Queues , 1951 .

[29]  C. L. Moodie,et al.  A HEURISTIC METHOD OF ASSEMBLY LINE BALANCING FOR ASSUMPTIONS OF CONSTANTOR VARIABLE WORK ELEMENT TIMES , 1964 .

[30]  A. D. Knott,et al.  THE INEFFICIENCY OF A SERIES OF WORK STATIONS—A SIMPLE FORMULA , 1970 .

[31]  Kathryn E. Stecke,et al.  Formulation and Solution of Nonlinear Integer Production Planning Problems for Flexible Manufacturing Systems , 1983 .