MANUAL LABOR IN PRODUCTION SYSTEMS
a place for manual labor in the modern production system? The answer is
certainly yes. Even in a highly automated production system, humans are still a
necessary component of the manufacturing enterprise. For the foreseeable
future, people will be required to manage and maintain the plant, even in those
cases where they do not participate directly in its manufacturing operations.
Let us separate our discussion of the labor issue into two parts, corresponding
to our previous distinction between facilities and manufacturing support: (1)
manual labor in factory operations and (2) labor in the manufacturing support
Manual Labor in Factory Operations
no denying that the longterm trend in manufacturing is toward greater use of
automated machines to substitute for manual labor. This has been true
throughout human history, and there is every reason to believe the trend will
continue. It has been made possible by applying advances in technology to
factory operations. In parallel, and sometimes in conflict, with this
technologically driven trend are issues of economics that continue to find
reasons for employing manual labor in manufacturing operations.
one of the current economic realities in the world is that there are countries
whose average hourly wage rates are sufficiently low that most automation
projects are im possible to justify strictly on the basis of cost reduction. At
time of writing, these countries include Mexico, China, and most of the
countries of Southeast Asia. With the recent passage of the North American Free
Trade Agreement (NAFTA), the North American continent has become one large
labor pool. Within this pool, Mexico’s labor rate is an order of magnitude less
than that in the United States. For U.S. corporate executives making decisions
on a factory location or the outsourcing of work, this is an economic reality
that must be reckoned with.
In addition to the labor rate issue, there are other reasons, ultimately
based on economics, that make the use of manual labor a feasible alternative to
automation. Humans possess certain attributes that give them an advantage over
machines in certain situations and certain kinds of tasks. Table 1.1 lists the
relative strengths and attributes of humans and machines. A number of situations
can be listed in which manual labor is usually preferred over automation:
• Task is too technological difficulty to automated. Certain
tasks are very difficult (either technologically or economically) to automate.
Reasons for the difficulty include:
with physical access to the work location, (2) adjustments required in the
task, (3) manual dexterity requirements, and (3) demands on handeye
coordination. Manual labor is used to perform the tasks in these cases.
Examples include automobile final assembly lines where many final trim
operations are accomplished by human workers.
• Short product life cycle. If the
product must be designed and introduced in a short period of time to meet a nearterm window of opportunity in the
marketplace, or if the product is anticipated to be on the market for a
relatively short period, then a manufacturing method designed around manual
labor allows for a much faster product launch than does an automated
method.Tooling for manual production can be fabricated in much less time and at
much lower cost than comparable automation tooling.
• Customized product. If the
customer requires a oneofakind item with unique features, manual labor may have
the advantage as the appropriate production resource because of its versatility
and adaptability. Humans are more flexible than any automated machine.
• To cope with ups and downs in demand. Changes
in demand for a product necessitate changes
in production output levels. Such changes are more easily made when manual
labor is used as the means of production. An automated manufacturing system has
a fixed cost associated with its investment. If output is reduced, that fixed
cost must be spread over fewer units, driving up the unit cost of the product.
On the other hand,
automated system has an ultimate upper limit on its output capacity. It cannot
produce more than its rated capacity. By contrast, manual labor can be added or
reduced as needed to meet demand, and the associated cost of the resource is in
direct proportion to its usage. Manual labor can be used to augment the output
of an existing automated system during those periods when demand exceeds the
capacity of the automated system.
• To reduce risk of product failure. A
company introducing a new product to the market never knows for sure what the
ultimate success of that product will be. Some products will have long life
cycles, while others will be on the market for relatively short lives. The use
of manual labor as the productive resource at the beginning of the product’s
life reduces the company’s risk of losing a significant investment in
automation if the product fails to achieve a long market life. In Section
1.5.3, we discuss an automation migration strategy that is suitable for
introducing a new product.
in Manufacturing Support Systems
manufacturing support functions, many of the routine manual and clerical tasks
can be automated using computer systems. Certain production planning activities
are better accomplished by computer than by clerks. Material requirements
planning (MRP, Section 26.2) is an example: In material requirements planning,
order releases are generated for component parts and raw materials based on the
master production schedule for final products. This requires a massive amount
of data processing that is best suited to computer automation. Many commercial
software packages are available to perform MRP. With few exceptions, companies
that need to accomplish MRP rely on the computer. Humans are still required to
interpret and implement the output of these MRP computations and to otherwise
manage the production planning function.
In modern production systems, the computer is used as an aid in
performing virtually all manufacturing support activities. Computeraided design
systems are used in product design. The human designer is still required to do
the creative work. The CAD system is a tool that assists and amplifies the
designer’s creative talents. Computeraided process planning systems are used by
manufacturing engineers to plan the production methods and routings. In these
examples, humans are integral components in the operation of the manufacturing
support functions, and the computeraided systems are tools to increase
productivity and improve quality. CAD and CAM systems rarely operate completely
in automatic mode.
It is very unlikely that humans will never be needed in manufacturing
support systems, no matter how automated the systems are. People will be needed
to do the decision making, learning, engineering, evaluating, managing, and
other functions for which humans are much better suited than are machines,
according to Table 1.1.
Even if all of the manufacturing systems in the factory are automated,
there will still be a need for the following kinds of work to be performed:
• Equipment maintenance. Skilled
technicians will be required to maintain and repair the automated systems in the factory when these systems break down.To
improve the reliability of the automated systems, preventive maintenance will
have to be carried out.
Programming and computer
operation. There will be a continual demand to upgrade software, install new versions of software packages, and execute
the programs. It is anticipated that much of the routine process planning,
numerical control part pro gramming, and robot programming may be highly
automated using artificial intelligence in the future.
• Engineering project work. The
computerautomated and integrated factory is likely never to be finished. There will be a continual need to upgrade
production machines, design tooling, and undertake continuous improvement
projects. These activities require the skills of engineers working in the
• Plant management. Someone must be responsible for
running the factory. There will be a
limited staff of professional managers and engineers who are responsible for
plant operations. There is likely to be an increased emphasis on managers’
technical skills rather than in traditional factory management positions, where
the emphasis is on personnel skills.