TRB&S develops COMSOAL for balancing assembly lines;

              TRB&S develops COMSOAL
Computer Method of Sequencing Operation for Assembly Lines
for balancing Assembly Lines
Dennis E. MulvihilP
ASSEMBLY LINE BALANCING is the term applied to a
common problem in many industries, that of sequencing
continuous manufacturing operations and assigning vari­ous
combinations of these operations to individual work­ers
on the line. A perfectly balanced line results when
manufacturing operations are assigned to men in a se­quence
which minimizes the number of men required,
equalizes the amount of work assigned to each man,
minimizes both idle time and make-ready time,2 but en­sures
sufficient idle time to handle the expected variations
in operation times without slowing the line. To the extent
that the line balance is less than perfect, men and equip­ment
are used inefficiently.
Balancing an assembly line by manual, trial and error
methods is an arduous task. Industrial engineers now
spend up to several weeks developing a few sequences of
operations in order to select one they hope will minimize
the number of men required for a line. Since there are
usually many thousands or even millions of different
sequences which could be developed, it would be most
surprising if the engineer stumbled upon the best se­quence
in half a dozen tries.
In order to solve this problem, the method which we
1 The other former or current members of TRB&S who helped
in the development of this technique are Albert Arcus, now with
the University of California, Gerald Demirjian, now with
Chrysler Corporation, Sanford S. Ackerman and Roger R. Crane.
- Make-ready time covers necessary but nonproductive opera­tions
such as picking up and putting down tools, walking back
to a start point along a moving conveyor and indexing the work
into the proper physical positions.
call COMSOAL, COmputer Method of Sequencing
Operations for Assembly Lines, was developed by TRB&S
personnel in conjunction with personnel from one of our
clients and from one of the major computer manufac­turers.
Although the basic technology underlying COM­SOAL
will soon be widely known, TRB&S presently has
proprietary rights to the only comprehensive working
system, and it would cost a company perhaps $250,000
to develop a similar system on their own. Our system is
available at a fraction of that cost.
The basic COMSOAL system is designed and pro­grammed
for running on an IBM 7090. The computer
programs are sufficiently general for application to the
vast majority of assembly lines, so it is not necessary for
a company to have its own IBM 7090 in order to use
COMSOAL. Time can be rented on a number of these
computers throughout the United States.
Many companies can substantially improve their as­signments
of assembly line labor without resorting to the
computer. In applying COMSOAL, the first step is the
development of a "balloon diagram," illustrated below.
This shows all of the required technological precedence
relationships among operations which have to be per­formed
on an assembly line. In other words, it shows all
of the other operations which must be completed before
starting on any particular operation.
The balloon diagram, although it bears a superficial
resemblance to a PERT network diagram,3 is concerned
3 See "PERT-CPM" by William D. Power, Quarterly, Decem­ber
1962.
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