There is no need for additional external scheduling or planning beyond this
one scheduling point. For the build-to-stock items, the needs of the customer
(represented by the supermarket) are visible to everyone. The kanban are used
to represent the inventory position and are effectively used to control the correct
quantities. Kanban can be placed on a board, and visually represent an inverse
relationship of the inventory—each kanban represents a reduced level of inven-
tory. Build-to-order items can also be placed on the board so it’s clear what is being
built to a real customer order, to replenish the supermarket, and to replenish
safety stock. Setting priorities becomes visual and straightforward. When Toyota
says, “Operators can schedule their own work,” this is what they mean. The
operators are not performing traditional planning and scheduling—predicting
what should be produced and when—they are simply using the information
that flows to them from the visual system and a defined process governs the
decision making.
How to Establish a Basic Leveled Schedule
Getting to a true heijunka schedule with a steady pitch multiple times in the day
is what we would consider an advanced lean practice. Some minimum amount
of leveling is needed in the stability phase (see Chapter 4) to even establish a
basis for calculating a takt time and setting up basic flow. During the initial
stages the pitch time is generally larger, often a daily time window, which creates
a basis for stability, but it is not an impossible challenge. Attempting a smaller
pitch prematurely may surface too many problems and create a system that is
impossible to maintain.
In addition to the pitch time increment, the three aspects that will be leveled
are:
- Product volume, whichis simply the quantity of a given product that must
be produced in a specified period of time (the pitch). - Product mix, which is the proportion of the various models that are pro-
duced during the pitch increment, the quantity of A’s, B’s, C’s, and so
forth. - Product sequence, which is the order that the product volume and mix are
produced. It may be model by model, such as A, A, A, B, B, B, C, C, C, or
part by part, such as A, C, A, B, A, C.
These three are listed in order of difficulty. Depending upon your starting
point, you may need to begin by establishing a simple volume and mix leveling
on a larger pitch time such as one shift or one day. We know that everyone is
touting single-piece flow and sequenced heijunka as the epitome of lean, but
that objective may be far off, depending upon the current condition of your
Chapter 7. Leveling: Be More Like the Tortoise Than the Hare 151