Page 324 - The Handbook for Quality Management a Complete Guide to Operational Excellence

310 C o n t i n u o u s I m p r o v e m e n t A n a l y z e S t a g e 311

(in items). Takt is a German word meaning metronome, and is used to
indicate the desired rhythm of the process. The takt time is posted at the
cell, and the resources (machines, personnel) at each step in the process are
balanced so that its cycle time equals the takt time. This level loading
ensures that goods produced at each step are used immediately by the next
step, ensuring a constant flow of items (or service) through the value
stream. If a temporary increase in orders is received, the pace remains the
same, but resources are moved to meet demand. In this way, the process
steps are resourced to accommodate a pull system of management, where
items are only processed when needed by the next operation.
The lean concept of transparency, or visual control, makes everyone aware
of the current status of the process, and has been found to decrease the
reaction time to waste, foster responsibility, and aid in problem solving.
While we can usually design the process and allocate standard
resources for any process to meet its standard takt time, we recognize that
a shift in demand will shift the takt time requirements. One way to accom-
modate the takt time adjustment is to shift resources.
Once personnel and equipment have been reorganized into product
cells, resource allocation to these cells becomes critical. We calculate the takt
time by dividing the number of hours the resource is available by the total
demand. For example, if the product has an average demand of 60 units per
day, and the cell works 15 hours per day (two shifts, minus breaks), then the
takt time is calculated as 15 minutes (i.e., 0.25 hour per unit).
Batches are difficult to match to takt time, as they disrupt the continu-
ous process stream. For example, a lab procedure runs 16 samples at a
time through centrifuge. The first sample to reach this step waits until the
16th sample is received. If you’re the patient waiting for the results of that
first sample, you’re not being efficiently serviced (from your perspective).
The process sits idle awaiting the full 16 samples. Furthermore, the next
step in the process receives all 16 samples at once, creating a large spike in
demand. A better use of resources across the system is to level the load to
a constant flow throughout the process.
The problem with batches is that they are not nearly as efficient, from a
systems point of view and a customer’s perspective, as they appear.
As ironic as it may seem, a major reason our processes contain waste is
because of our historical attempts to make them more efficient. One fal-
lacy we have accepted is that we can make processes more efficient by
creating specialized departments that process work in batches. These
departments become efficient at what they do from a process standpoint,
with economic lot quantities designed to minimize set-up time or material
delivery costs, but they lack efficiency relative to specific product value
streams. Waste is created in waiting for the batch to begin its departmental
processing, and waste is additionally created when particular units of

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