100 THETOYOTAWAYFIELDBOOK
Pull in a Custom Manufacturing Environment
Because of the simple model (see Figure 5-8), which is based upon the produc-
tion of the same three models of parts again and again, many people believe
that pull in a high-variety or custom production environment is not possible.
This is based on the incorrect assumption that when Operation C produces a
specific model, they will send a “pull signal” to the preceding operation (B) to
make a replacement for that same model. Operation C uses a “ 1 ” and Operation
B makes a replacement version of “ 1 .”
What if you have thousands of possible items and some may be used only once
per month? In a high-variety, high-mix, or custom production situation the instruc-
tion on what to produce next (the custom order) would be given to Operation A
rather than C. After completion, Operation A passes the part to Operation B. Then
Operation B would work on this part, complete it, and pass it to Operation C. In
this manner the work “flows through” the subsequent operations. Remember that
flow and pull are not the same thing. The common assumption is that the work
must be pushedto Operation B and Operation C if the instruction to produce is pro-
vided to the beginning of the line (Operation A).
Look back at the distinctions between push and pull. The first element is a
defined agreement between the two parties. Is there a defined agreement between
Operation A and Operation B in a custom production situation? Yes, it is still
one piece of work in process. The second element requires that the location be
defined in accordance with the agreement and then dedicated. The space is ded-
icated just as in the previous example. The third element requires a method to
control the production to satisfy the agreement (the standard). How is the pro-
duction controlled? It is controlled the same way—visually.
What is the difference? The only difference is in the agreement of “what the
customer wants.” In this case, the quantity is the same, but what about the model?
The customer processes (B and C) do not dictate the specific model produced by
their supplier. The agreement is that each operation produces the next product
in the same sequencepresented by the preceding operation. This is referred to as
“sequenced pull” or “sequenced flow.”
Figure 5-9, below, shows sequenced flow production for a high product vari-
ety situation. Operation A receives the schedule, and has previously produced a
Model 2, Model 1, and another Model 2; and the next item on the schedule is
Model 3. Since there is an open space between Operation A and Operation B, A
has permission to produce the next item on the schedule. The rules of pull are
still followed in that Operation A would not produce if the space were full. The
rule states that an operation can complete the part in process if the customer
space is full, but will not pass the part to the space. The part will remain in the