Reasons for Modeling:

  1. Highlight problems of interest.
  2. Economical experimentation.
  3. Precision of thought.
  4. Solving operational problems.
  5. Impossible to analyze some systems mentally since some systems are counterintuitive; mental models are usually inexact.
  6. quantifies relationships and identifies gaps in our knowledge (can be used to guide research)
  7. range of variables that can be examined in actual system is often quite small in time and space scale
  8. dynamics of actual system may preclude data collection and observation

Schematic Models

One of the initial steps in a modeling exercise is to organize the elements of the system being studied in some fashion. Schematic models provide a means of visualizing system structure and operation without immediately trying to mathematically represent the system. Such schematic models can reveal redundancies and system weaknesses that can be corrected without extensive formal analysis. Understanding a system well enough to construct a schematic model of its operation may be the most important benefit of an operations engineering study.

There are many types of schematic models that might be used by an operations engineer. The schematic models attempt to organize knowledge in a logical fashion such that time, space and structural relationships can be easily understood. Commonly used techniques include:

  1. Organization charts
  2. Process Charts
  3. Activity Charts
  4. Logic Flow Charts

Organization Charts

Organization Charts - most activities require some form of organization. The usual concept of an organization chart is that of a series of blocks and lines showing the manner in which individuals and functions are related to each other. They depict functional responsibility and chain of command.

Organization charts provide snapshots of a company's structure at one particular point in time. They are essentially a static display of relationships.

An alternative to the functional type of organization is one which is product oriented. In those cases each product line leads to a separate structure. A quick glance at such charts establishes at least formally the complete chain of command.

Unfortunately there is often considerable difference between what many existing organization charts say about corporate responsibility and authority and what actually occurs in daily operations. For that reason, an analyst who is concerned with organizational problems would do well to construct their own diagram depicting how decisions are really made in the informal organization on the basis of personal observation.

In spite of its shortcomings, the organization chart can be a valuable tool for both operations managers and engineers. Specific uses of the organization chart include:

  1. To show lines of direct authority and thereby serve as a quick check on who is responsible for the various functions.
  2. To illuminate organizational weaknesses such as more than one person being assigned the same work or certain work being assigned to no one.
  3. To serve as a training device and guide in planning for expansion.
  4. To alert the public about work relationships within the company.
  5. To remind employees about who supervises them.

Process Charts

Process charts provide a graphical representation of movement through a process. They are most commonly used to chart the movement of material through a manufacturing process but can easily be adapted to chart the activities of a human operator or the flow of information in a system. It is considered good practice to limit each chart to one class of movement, e.g. do not mix materials and people on the same chart. Standard symbols are often used in process charts.