Various types of lean manufacturing waste include material waste, avoidable down time, and time wasted through unproductive activities. Overproduction is another form of waste. Other types of waste may arise from inaccurate matching of resources to tasks, or performing unnecessary motions in the workplace.
Defects in manufacturing are a common means of causing wastage in materials. Sometimes these defects result from machinery that has not been properly maintained, or is used in an inappropriate manner. Another type of lean manufacturing waste can occur during those stages of manufacturing where the raw material is shaped or cut for a specific purpose. If that process goes awry due to operator error, then often the piece must be discarded as waste.
Either unplanned or planned downtime may result in a waste of both facility use and man-hours. When an assembly line is idled — due to an equipment failure, for example — then underutilization of that resource produces lean manufacturing waste. Typically, unplanned downtime will produce more waste than planned shutdowns. A common reason cited is the lack of time to plan for a controlled cessation of production.
For example, if the assembly line shuts down at a time when full operations were planned, and both materials and people were positioned to engage in productive work, that event will likely create a large amount of wasted time. On the other hand, if the outage is planned, then the production managers will usually arrange for the least number of personnel to be at the facility during the shutdown. Such pre-planning usually reduces payroll costs.
Inaccurate matching of resources to tasks is another type of lean manufacturing waste. Sometimes this may involve tapping the skills of a highly trained person to do a task that a person with less training could do. At other times, it may involve a mismatch between equipment and task. For example, if a worker is attempting to complete a task with a machine that is not specifically suited to that task, it may result in wasted time.
Unproductive activities may also involve the performance of unnecessary tasks, and may occur in a couple of ways. First, the person performing the task may be engaging in extra motions that are not necessary to complete the task, and secondly, the task may not even be a part of the planned manufacturing routine that the manufacturer has put into place. For example, if a worker has to transport a certain quantity of partially completed materials on a regular basis, he or she may choose to engage another employee in a conversation at another work station. Although it may seem an almost insignificant factor in lean manufacturing waste, when that activity is repeated several times per day, or per week, the cost of unproductive time adds up.