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  • Writer's pictureAntónio Sousa

One-piece flow and COVID-19

Updated: Nov 28, 2023


The COVID-19 pandemic has been disruptive in our societies and its impact will certainly be felt in the next years. Besides shutdown, other measures to control the spread of coronavirus have been impacting our daily life. Several activities face the need to introduce new tasks and the fundamental process parameters are changing.

If we (as difficult as it seems) put aside, for a brief moment, the health crisis situation and look at these added tasks from the Lean 6 Sigma point of view, we will conclude that they are non-added value tasks, that is, tasks the customer does not value and does not want to pay for. Of course, when we put ourselves back in the pandemic context everyone accepts these tasks and they are fully justified, given the priority to human life protection. But these tasks are still having a negative impact on the process lead time.

All this in a rapidly changing environment and with growing concerns about efficiency and the use of resources. As so we find important to go back to the process flow improvement concepts and to explore the opportunities present in the current context.


One the pillars of Lean, coming from the Toyota Production System, is Just in Time. It can be briefly described as the ability to produce, at the right moment, the exact quantity of a product which meets the customer requirements. Process flow improvement is one of the elements of Just-In time and consists in organizing machines and workstations according to the process sequence, to strongly reduce or to eliminate work in process, waiting, transportation and motion.

Process flow improvement involves process analysis, eliminating non added value activities, layout design (with the introduction of one-piece flow lines or cells), ergonomics improvement, dynamic operation balancing and better operator versatility.

We can say a process works in one-piece flow when the processing lot size is one.

Fluxo unitário
Continuous Flow ("Basic Concept of Toyota Production System, TMC")

This concept breaks the lot production paradigm, in which the goal is to maximize the workstation or machine occupation and to optimize transportation. This leads to bigger size lots with the consequences of increased lead time and work in process.

Processo de montagem antes da melhoria de fluxo
Assembly process before continuous flow

The application of one-piece flow can, frequently, increase productivity by 20-30% and to divide lead-time by 10. Apart from these results, one-piece flow processes have other advantages:

  1. The process effectiveness and productivity are the same for different numbers of operators. As such the line or cell can be operated by 1, 2, 3 or more operators, to the maximum number it was designed for.

  2. This also allows the process to respond to demand variations or to operator availability, without affecting productivity or finished product output.

The operator versatility required also allows to rotate workers through the workstations, which, in turn, makes all of them familiar with the entire process.

O mesmo processo após a melhoria de fluxo
Assembly process - after one piece flow implementation


Following shutdown, several recommendations were issued, and the first COVID-19 preventive measures were defined for businesses and companies to apply.

Several of these measures are applied to all processes and workstations (hand washing, respiratory etiquette, surface cleaning and disinfection, self-monitoring of symptoms, individual protection equipment) other (social distancing) look to go against the one-piece flow principles:

  • The workstation's dimensions are the smallest possible, in a way the assures the ergonomics and the efficiency of the operations and the workstations are as close as possible, to reduce transportation between workstations.

  • The number of workstations is bigger than the number of workers, to allow for dynamic balancing and the correct distribution for different numbers of operators.

  • The dynamic balancing standardizes which workstations are to be shared, to balance the work time of the operators. Each of these workstations can be used by 2 of the operators.

In the current context these characteristics can be put to good use by the organizations, to the benefit of their workers. Taking the health recommendations, we can identify the following advantages of one-piece flow production:

  • Minimize direct contact between workers: side by side work is preferred to face to face work

    1. By nature, work on one-piece flow lines is done side by side or back to back

    2. In U-shaped lines the distribution of work can be made so the workers are most of the time back to back

  • Set up small teams and organize unsynchronized working time and breaks, to limit social interaction:

    1. One-piece flow lines allow for the breaks to be made in different moments by each operator, reducing contact without stopping the process

    2. They also allow to work in 2 shifts with half the workers instead of one shift, maintaining output and reducing contact

    3. Use physical barriers between workers and users/clients/public: One-piece flow lines also allow barriers to be implemented (acrylic ones, for example) at some points without disturbing the flow or the work sequence

Additionally, the standard work necessary to the good operation of one-piece flow lines is a good base to incorporate PPE and disinfection rules:

  • Gloves, masks or face shields use

  • Hand disinfection on each cycle start

The Poke-Yoke concept can also be applied to these conditions, for example, by blocking the process if someone has not sanitized his hands.


One-piece flow production, although known and put to practice for the last 5 decades, is still not used to its full potential. Implementing one-piece flow breaks long established paradigms and needs quite some practice and discipline. If there is not a strong organization commitment and a good support these aspects can make things go back to the old habits as the first difficulties arise.

The current social distancing recommendations can look like a threat to one-piece flow, but they are not. They open new ways to improve the processes without compromising workers health and safety and, most importantly, not letting the guard down regarding the pandemic.


Toyota Motor Corporation: The TPS concept

Toyota Motor Corporation: Basic concept of the Toyota Production System


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