Page 105 - How To Implement Lean Manufacturing

84 Cha pte r F i v e

Reducing Production Time
Reducing production time is a combination of:

• Eliminating unnecessary processing steps
• Reducing production defects
• Changing the current conditions so those processing steps which are currently
necessary, but not valued added, can be eliminated

Reducing Piece Wait Time
Piece wait time is reduced by balancing, so the flow is synchronized.
Reducing Lot Wait Time
Lot wait time is the time that a piece, within a lot, is waiting to be processed. To reduce
lot wait times, shrink lot sizes and level the model mix. The goal of minimum lot sizes
is one-piece. When lot wait time is reduced, first piece wait time is also reduced. This
time is often overlooked but is incredibly important. There will always be quality and
production issues and these issues must be uncovered quickly so they can be solved.
First piece lead time is often the key to being responsive to quality problems.

Reducing Process Delays
Process delay is the time an entire lot is waiting to be processed. Often it is called queue
time. To eliminate this, we must level production quantities and processing capacity
and synchronize the flow in the entire plant. The most common causes of these delays
are mismatched capacities and batch production. This can also be caused by lack of
synchronization and by transportation delays.
Managing the Process to Absorb Deviations and Solve Problems
Many sources of deviation increase production lead times, such as machinery break-
downs and stoppages for quality problems, to name just a few. All these deviations
cause inventories to rise, and inventories are the nemesis in Lean manufacturing—we
want to reach zero inventory if we can. Where we have variation in the system, do not
add inventory. Instead, attack the variation. One of the key tools to manage the process
is the concept of transparency. If the condition of the process is transparent, then Rapid
Response PDCA (Plan, Do, Check, Act) can be performed.

Reducing Transportation Delays
One piece flow, synchronization, and product leveling all place emphasis on transpor-
tation, which (if you recall) is a waste. To reduce this waste, several strategies can be
employed. Kanban is the first thing most people think of, but kanban has inventory and
creates a second delay, the delay of information transfer, so it is a double waste in itself.
Thus, try to avoid kanban systems by instead using close coupled operations, such as
those used in a cell, or use conveyors.

Reducing Changeover Times
Whenever a machine has multiple uses, we must changeover between production runs.
To maintain production before and after the machine, we install inventory buffers that,