The lean approach towards construction adopts both physical and non-physical waste production. On the basis of the existing literature, waste in the context of construction can be classified into eight types, namely defects, overproduction, waiting, not-utilizing talent, transportation, inventory excess, motion waste, and excess processing.
The definition of waste as well as its classification has been approached by various researchers. In general, researchers have commonly included defects and excess processing as some of the more common factors considered as waste (Senaratne & Wijesiri, 2008). Additionally, other factors have been mentioned in specific industries to broaden this classification. For instance, researchers have suggested “a broader definition of waste to include not only material waste, but also waste generated in a construction project such as waiting times, transportation times…” (Hosseini, Nikakhtar, Wong, & Zavichi, 2012, p. 415). The lean approach for the elimination of waste, as described by Ohno (1988), is as follows: “All we are doing is looking at the time line, from the moment the customer gives us an order to the point when we collect cash. And we are reducing that time line by removing the non-value-added wastes” (p. 9).
Waiting refers to multiple types of delays such as waiting related to processing relevant to products, waiting related to operators relevant to machines, and waiting related to the arrival of material relevant to machines (Ohno, 1988). The most common waste resulting from waiting is waiting relevant to inventories. There are multiple charactersitcs that are generally associated with the waste caused by waiting. For instance, waiting associated with the resolution of a breakdown, waiting associated with the completion of previous process, quality problems with previous production batch causing machines and operators to wait, waiting associated with the delivery of information, and waiting associated with the requirements of products. Studies suggest that most of the time spent by products is in warehouses. Organizations spend financial resources to produce products. Waiting can be a significant waste as the resources spent by organizations may not account in terms of reward if they are spent in waiting (Mezgebe, Asgedom, & Desta, 2013). Additionally, time wasted due to waiting is often recovered through overtime, which costs organizations more money while not providing additional profit.
Researchers have highlighted various causes for waiting in the production process. The major cause for waiting that results in waste is lack of balance among processes (Jones & Womack, 2014). For instance, if one production process requires more time than the process that directly follows it, then those operating the second process will have to wait or slow down their work, during which they will not be sufficiently productive. In addition to lack of balance, lack of reliability has been identified as another major source of waiting in production (Senaratne & Wijesiri, 2008). For instance, unreliable inventory may result in breakdowns, lack of sufficient information, or issues related to quality in a process, all of which may halt the process that directly follows it.
In addition to its own causes, waiting may be caused due to other types of waste. For instance, inventory and overproduction waste may influence waiting, as production companies move products in a batch from one place to another, and the limited resources available for handling could result in waiting for other processes affected by overproduction and inventory waste (Gupta & Jain, 2013). Waiting is also caused by lack of information, as missing or unclear information with respect to operation may result in waste.
Researchers have suggested various strategies for eliminating or minimizing the waste resulting from waiting in production. The lean principle involves increasing balance in the process of production to minimize the possibility of disruption in individual production processes (Lacerda, Xambre, & Alvelos, 2015). Organizations can adopt planning methods that are visual in nature to decrease the waiting resulting from communication. The waiting caused by insufficient information can also be eliminated by holding regular meetings between process operators (Jimmerson, Weber, & Sobek, 2005). As the waste associated with inventor and overproduction affects waiting in production, minimizing or eliminating them can also automatically improve the waste associated with waiting in the factory as well as during transportation. The waste associated with waiting can have detrimental effect not only on the profit of an organization, but also on the productivity and morale of the workers (Forsberg & Saukkoriipi, 2007). The lean principle involves value stream mapping, which is used to recognize the flow of product in a factory. These tool involves the mapping of inventory levels, set-up times, and processing times through standardized symbols, which provide an overview of the relationship between processing time and waiting. Additionally, ensuring the quality and reliability of tools, either through regular maintenance or through the use of high quality tools, can be beneficial to minimize waiting during production processes.
Author: Henri Suissa
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