Standardized Work
Standardized Work (SW) is one of the tools of the lean philosophy that makes the big difference between Toyota and the others.
At Toyota, SW is treated with the utmost seriousness, and it is through it that the desired stability of the production system is sustained. This stability has a great impact on workplace safety, on the quality with which tasks are performed, which is reflected in product quality, and obviously on productivity. As a consequence, its influence on employee morale becomes a distinctive factor of competitiveness and motivation, because workers who clearly know what, where, when, why, and how tasks are to be performed become well-informed employees and also have in SW a reference for continuous improvement.
Many who implement lean thinking are familiar with this tool, but in practice things leave a lot to be desired.
So what is the difficulty?
The greatest difficulty is the result and consequence of not going deep enough into the core of the lean philosophy. It starts with one of the fundamental elements of the lean philosophy, which is takt time (TT). Without TT, you cannot even think about SW. Besides TT, there are other elements that are equally fundamental: the employee’s Work Sequence (WS) and Standard In-Process Stock (SIPS). And, in addition, the premise that the process must be repetitive.
SW is entirely geared toward making the most of the labor resource – at a normal operating pace, without overloading employees or putting their well-being at risk – rather than machines and equipment.
It is customers who determine takt time; through demand, they set a pace for the activities of the entire chain. This pace is carried into production, and that is where the great transformation takes place in the processes that truly add value, that is, in transforming raw materials into finished products. Here you can feel and understand how important TT is in setting the cadence of activities. And this cadence of activities, once standardized, becomes SW. The WS is considered down to the smallest detail to optimize the whole, and the SIPS to process in continuous flow.
The sequencing and standardization are done by the production team leader together with his or her team members. Obviously they have the support of the technical staff who prepare the work standards. I want to point out here that Work Standards (WStd) are something quite distinct from Standardized Work (SW). WStd are prepared by the technical staff and consist of operating rules and/or procedures and technical specifications for safety, quality, and processes. SW, as we have seen, is prepared by the production team leader and consists of three basic documents: the Process Capacity Sheet (PCS), the Standardized Work Combination Table (SWCT), and the Standardized Work Chart (SWC). Put another way, WStd is the recipe for how to make
a single product, while SW is the arrangement of labor, machine, and equipment resources to make a series of products dictated by TT.
Once SW has been prepared, it becomes the reference for implementing Kaizen. At Toyota, it is commonplace for people to say that without SW there is no Kaizen, and that makes a lot of sense, because without a proper reference, how do you carry out and measure an improvement that has been implemented? And further, how do you assess the need to make an improvement? Improvement is made when the need for it arises.
Making changes to SW requires labor and time resources. It is therefore recommended not to change TT too often, because every change in TT automatically implies a change in SW.
On the shop floor, it is necessary to plan in order to change TT and, consequently, SW. (Hiring and training labor takes time and is expensive – plan for a minimum of three to four months.)
If the increase in demand is for a predictable period, for example three to four months, working more hours (overtime) is recommended.
Toyota rarely runs its plants on three shifts, because that allows no flexibility to work overtime.
The most common practice is to operate two shifts with breaks between shifts; this provides up to 25% flexibility in production. On the other hand, if demand falls, fewer hours are worked. All of this is to keep TT constant (unchanged), which ensures production stability. Do not forget to take into account the suppliers, who are also part of the chain.
Let us look at a practical numerical example from vehicle assembly.
Assembling one vehicle, with all parts and components, equipment, and tools available, would take six hours of one assembler’s time. Considering that demand calls for a TT of 4 minutes per vehicle, this does not mean that the vehicle is assembled in four minutes. It should be understood to mean that a finished car leaves the assembly line every 4 minutes.
So how should the assembly line be sized and structured?
A vehicle assembly line, by the nature of the operation, is labor-intensive. So let us think about and use the OBC (Operator Balance Chart) to distribute labor across the previously established process sequence (the assembly process must be prepared beforehand, based largely on the experience of the team leaders, who determine the work elements of the processes taking into account all the work standards).
Six hours means 360 minutes. TT is 4 minutes. Dividing one assembler’s total assembly time of 360 minutes by TT (4 minutes, which is also the sum of the work elements for each assembler), we get 90. This number represents the number of people needed for this arrangement. The assembly line will then have 90 workstations, with one operator at each station and a workload slightly below 4 minutes (cycle time (CT) equal to 95% of TT). In this way, each assembler has a well-defined task, which becomes standardized after some time of learning and experience, thus constituting SW.
We have seen briefly how labor is calculated and sized. Now you can already imagine that if TT is changed, for example to 3 minutes, SW changes completely
and the whole OBC has to be restructured, and the number of assemblers for the new situation is 120 people. That is why TT cannot be changed from one moment to
the next. It requires detailed planning well in advance. And remember, an automaker usually has more than just the assembly line.
It has other processes such as Stamping, Body Shop, and Paint, which also require restructuring and adjustments to processes and labor. Hiring as well as laying off people is not only expensive but also takes time, and when you add the time to train new employees, the lead time goes beyond three to four months, not to mention the great work of completely revising SW. And SW has everything to do with operational stability.
The next column will be about Kaizen.
