[LKUK13] I Broke the WIP Limit Twice, and I'm Still on the Team

@ZsoltFabok
http://zsoltfabok.com/
#lkuk13
http://lkuk.leankanban.com/
by
Zsolt Fabok
2013.11.01
Broke the WIP limit TWICE
Still on the team

lead time
(minutes)
moving
(minutes)
waiting
(minutes)
ﬂow
efﬁciency
46 40 6 87%
44 40 4 91%
35 31 4 89%
38 26 12 68%
The time I need to get to work by bicycle

Where is the Kanban Method in all this?

It is in the deltas between the steps; the
desire to improve continuously.

Small incremental
evolutionary changes
(continuous improvement)

If you understand the purpose of small
incremental evolutionary changes and the
pull system, you’ll do ﬁne with the Kanban
Method, because you can easily deduce
the rest.

It is hard to improve the invisible, so
we have to see what we have at our
hands.

Value Stream Mapping
Start with what you do now
(possibly end to end)

Design
Implementation
Delivery
Test information
work item

Design
Implementation
Delivery
Test

Ready Design Implementation Test Delivery Live

This board was a “traditional” board,
how about a less “traditional” one?

We decided that we are going to discover
our value stream (ﬂow) on the go.

Flow (Stream)
The ﬂow ([value] stream) starts at the left side,
and ends at the right side of the board.

The Flow is different in a typical
enterprise and start-up environment.

Typical enterprise ﬂow
Flow (Stream)

Typical start-up ﬂow
Flow
Flow
Flow

Now we can see the previously unseen,
but we need to start pulling work items
otherwise they won’t get delivered.

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~ ~
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~ ~
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~ ~
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~ ~
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~ ~

The pull system itself does not guarantee
that work items get to be delivered.

That’s when the Work In Progress (WIP)
limit comes into the picture.

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~ ~
1 2 1 3
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~ ~
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~ ~
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~ ~

How to set the WIP limit
at the beginning?

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work done
staff liquidity + internal queue

Too low WIP limit creates unnecessary
bottleneck, too high WIP limit encourages
multitasking and/or longer lead time.

Yes, the WIP limit can
change over time.

# ~
~ ~
work done
week 1 week 2 week 3 week 4

Car manufacturing
vs
software engineering
“The inventory”

“Too many workers, equipment, and product only increase the
cost and cause secondary waste. For example, with too many
workers, unnecessary work is invented which, in turn, increases
power and materials usage. This is secondary waste. The
greatest waste of all is excess inventory. If there is too much
inventory for the plant to store, we must build a warehouse,
hire workers to carry the goods to this warehouse, and
probably buy a carrying cart for each worker.”
“In the warehouse, people would be needed for rust prevention
and inventory management. Even then, some stored goods still
rust and suffer damage. Because of this, additional workers will
be needed to repair the goods before removal from the
warehouse for use. Once stored in the warehouse, the goods
must be inventoried regularly. This requires additional workers.
When the situation reaches a certain level, some people
consider buying computers for inventory control.”

“Too many workers, equipment, and product only increase the
cost and cause secondary waste. For example, with too many
workers, unnecessary work is invented which, in turn, increases
power and materials usage. This is secondary waste. The
greatest waste of all is excess inventory. If there is too much
inventory for the plant to store, we must build a warehouse,
hire workers to carry the goods to this warehouse, and
probably buy a carrying cart for each worker.”
“In the warehouse, people would be needed for rust prevention
and inventory management. Even then, some stored goods still
rust and suffer damage. Because of this, additional workers will
be needed to repair the goods before removal from the
warehouse for use. Once stored in the warehouse, the goods
must be inventoried regularly. This requires additional workers.
When the situation reaches a certain level, some people
consider buying computers for inventory control.”
“...The greatest waste of all is excess inventory. If
there is too much inventory for the plant to store,
we must build a warehouse...”

Car manufacturing
vs
“The inventory”
(AtToyota the inventory is ﬁnite, however in
software engineering it is inﬁnite, therefore we
cannot approach it with the same attitude)

There is another kind of queue: the
inﬁnite queue.

2
1
Visible
Invisible
2 3
Inﬁnite queues

Now the work items are getting delivered,
it is time to improve the system.
Improvement requires measurement.

The lead time
1 2 1 3
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~ ~
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commitment

Distribution of lead times
days
count
0
3
5
8
10
13
15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 22 28 33 56
average
median*
*Calculation of medians is a popular technique in summary statistics and
summarizing statistical data, since it is simple to understand and easy to calculate,
while also giving a measure that is more robust in the presence of outlier values
Courtesy of Digital Natives

Car manufacturing
vs
“The takt time”
(In software engineering the demand is not
quantitive, therefore it doesn’t matter how
much time we spend between two features)

Car manufacturing
vs
“The throughput”
(In software engineering we don’t have to deliver 10
features, we have to deliverTHE feature, therefore
the number of delivered feature doesn’t help us, but
it is a good “secondary” measure to see how we react
to changes, or how good we are at forecasting)

0
2
4
5
7
week 1 week 2 week 3 week 4
incoming
outgoing
The throughput

The throughput (output) is helpful, if
and only if it is compared to the
demand (input).

1 2 1 3
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0
2
4
5
7
w 1 w 2 w 3 w 4
6

The goal is to have a stable system
(ﬁrst target) because improvement on
a stable system will have a long term
effect (second target).

1 2 1 3
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0
2
4
5
7
w 1 w 2 w 3 w 4
7
It is Monday on Week 5...
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Aging item

The aging items mess up your forecasting.

0
2
4
5
7
w 1 w 2 w 3 w 4
throughput
“We get N items a week”
“We deliver N items a week”
“Therefore we can deliver an
item in a week”
*This argument is so weak that a decent philosopher stops thinking about
philosophy and looks for another profession every time one reads it up
“We deliver an item in a week”
Therefore our lead time is the
length of the week which is 5
days)”*

days
count
0
3
5
8
10
13
15
1 2 3 4 5 6 7 8 9
But in reality you are actually here:
5 != [6,9]

Protect the bottleneck and don’t punish the
phase before the bottleneck.
(with Theory of Constraints)

3 3 4 2
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Bottleneck

3 3 4 2
# ~
~ ~
It hurts here...
...because the work items queue up here.
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3 3 4
2
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2
Now the bottleneck is better protected...
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...and the phase before the bottleneck doesn’t suffer.

If you understand the purpose of small
incremental evolutionary changes and the
pull system, you’ll do ﬁne in Kanban land,
because you can easily deduce the rest.
And be skeptical about the practices that come from the
manufacturing world (context matters).

Thank you very much for your attention!
@ZsoltFabokhttp://zsoltfabok.com/

[LKUK13] I Broke the WIP Limit Twice, and I'm Still on the Team

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