Hình 4-9. Quy trình ổn định sau khi sự thay đổi của thời gian hàn được phân lập được một nền tảng cho việc tạo dòng chảy và thiết lập tiêu chuẩn hóa. Về bản chất, cô lập của các biến đổi này là một ứng dụng cơ bản của heijunka, hoặc san lấp mặt bằng. Bằng cách nhóm các sản phẩm tương tự, | 78 The Toyota Way Fieldbook Figure 4-9. Process stability after variation of welding time is isolated a foundation for creating flow and establishing standardization. In essence this isolation of variation is a basic application of heijunka or leveling. By grouping similar products we were able to level the workload for the majority of the process. The highly variable work is still difficult to standardize but in this case 80 percent of the total is possible. This is an important aspect of creating stability. Some basic applications of leveling can be done in the stability phase and there are advanced applications of heijunka as well that will incrementally tighten the timing and pressure on the system in later phases. We will discuss this in detail in Chapter 7. One common mistake is to attempt to establish flow or standardization too soon. As we will go into in the next chapter creating flow between operations is designed to surface any issues quickly and to make them critical in nature ignoring them would be disastrous . If this step is taken before eliminating major obstacles the result will be too many problems and a consequent retreat to the old way. Likewise an attempt to standardize a chaotic process with a high level of variability will most certainly cause frustration since it is not possible to standardize variation. If we liken the creation of lean processes to building a house we understand that in order to support the roof we will need walls and trusses. Foundations and subfloors in turn support the walls. This is easy to see and understand because a house is a real visible tangible object with common elements they all have roofs of some type . A lean system on the other hand is not so clear. If you focus your effort on developing an understanding of the intent of each phase rather than the application of lean tools this process will be more successful. Understand the what before trying to apply the how. The lean tools are applied to address specific
