Page 134 - How To Implement Lean Manufacturing

How to Do Lean—The Four Strategies to Becoming Lean 113

allow the production process to stay at takt and remain as stable as possible.
(Chap. 3 has an example set of inventory calculations.)
• Leveling of Model Mixes or Products is used when more than one product is
made on a given production line. The goal of leveling is to avoid making a
batch of model A and then a batch of model B, and instead make both products,
simultaneously, one at a time at the demand rate of the customer. We are trying
to synchronize externally to the demand rate of the customer. To level production
in amount and by model mix, we will frequently use a heijunka box. If leveling
is not achieved, cycle, safety and buffer stocks must be much larger and, of
course, we want the inventory to be a minimum.

Wastes Reduced

Overproduction Overproduction is the waste targeted here. However, when over-
production is reduced, all other wastes are reduced as well; especially the waste of
inventory. In addition, this strategy to synchronize externally is the key to on-time
delivery. It will allow smooth production line operations so the line can produce at a
constant rate, using the safety and buffer stocks to take up the supply and demand
variations. In addition, it will allow the supply to be both more flexible and more
responsive.

Summary of Synchronize Externally
To establish the production rate at takt is absolutely crucial. This, coupled with the
establishment of Lean inventories will allow you to maintain supply to your cus-
tomer and run the process at a level and stable rate. This is always the first, and the
most important, step. It is often difficult to redesign the work stations for leveling of
the model mix since it often requires changeovers, and so on. If that is the case for
you, then do the model mix leveling later, but make sure you are producing at takt
and also have inventories set up to protect your supply to the customer. A word of
caution is in order. If you found that your production rate was unstable while doing
the systemwide evaluations, carry extra inventory. Seek advice from your sensei as to
how much. This inventory then becomes the protection that will allow you to both
assure supply to the customer as well as reduce the variations on your line from your
planning systems.
Frequently, you will want to install a heijunka board and a production kanban system
right away. You may have kanban training scheduled for later. However, implement
kanban here anyway, if at all possible. Have your sensei make the calculations and do a
short training for just those involved in this system. This type of JIT training will often
be necessary and it is not unusual to improvise from time to time like this.

Strategy 2: Synchronize Production, Internally

Conceptual Discussion
To synchronize production internally is to divide the necessary work in processing
steps such that each processing step takes the same time. The ideal is that all processing
steps perform at a cycle time equal to takt. The following Lean tools are used: