Civil Engineering Reference
In-Depth Information
TABLE 17.3
Human Factors Principles in DHA
Design for ease of manipulation
Design for tactile and auditory feedback
Design for visibility and visual feedback
Design for spatial compatibility
Design to enhance the formation of a mental model
Design for transfer of training
Design for job satisfaction
Visibility and visual feedback play an important role in assembly. Everything that is
used in the manufacturing task should be fully visible. Hidden or invisible parts cannot be
pointed at. They become difficult to think of and are more abstract. When a task has been
completed, there should be visual feedback—in other words, something should look
different. Sometimes in automobile assembly a piece of tape is put on top of a part to
indicate it is finished.
Spatial compatibility has to do with the spatial layout of a workstation and has been
addressed previously (see Figure 6.6). Part bins can be located in sequential order so that
the operator can pick parts from left to right in the same order as used in the assembly.
Part bins can also be arranged so that their location mimics the product design. This
could, for example, be used with components that are inserted in an electronic board. The
best arrangement depends on the product design and the number of parts used. Obviously
product design should consider spatial compatibility. One should also consider the
locations of hand tools and controls. Typically items that belong together in task
execution should be physically close. This is the proximity principle in Gestalt laws.
Workers develop mental models of the task they are performing; that is, they think of
an assembly in a certain way. The concept of mental models has been used extensively in
human-computer interaction. Software programmers have a different mental model than
do users of the same software. Therefore, programmers fail to consider the needs of the
user. Similarly, in manufacturing the product designer fails to consider mental models
other than his or her own. There are, indeed, many different mental models (Baggett and
Ehrenfeucht, 1991). A person assembling a product would have a different mental model
than a person responsible for the quality control of the same product. They look for
different things and they do different things, and the priorities are different. This
observation is contrary to the notion that assembly operators should exercise their own
quality control; it may be difficult to change a person's mindset (Shalin et al., 1994).
Transfer of training applies when a new product has only small modifications
compared with the old product. A worker can then apply his skills to the new product.
However, differences in product design and workstation layout may create confusion, and
assembly times can increase drastically. Product designers have a responsibility here to
make the assembly of new products similar to the assembly of previous products.
Design for job satisfaction is probably the most difficult aspect in planning for
manufacturing. One problem is that people have different needs and are satisfied by
different factors. We may understand better what factors lead to job dissatisfaction, and it
could be easier to design to avoid job dissatisfaction. However, more research is required
to understand the problem in depth.
