James R' Holt, Ph'D', PE' Jholtwsu'edu http:www'vancouver'wsu'edufacholt

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James R. Holt, Ph.D., PE.Jholt_at_wsu.eduhttp//www
.vancouver.wsu.edu/fac/holt/
Constraints Management
The Theory of Constraints Physical Process Games
The Assembly Game When Things Must Come All
Together!
Washington State UniversitysEngineering
Management Programhttp//www.cea.wsu.edu/engrmgt/
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Another Issue in Operations that Surfaces
Assembly

• Both Manufacturing and Projects have Assembly
  product Joins. There is a place were several
  things must all be available in order to proceed
• Typically, someone is late delays the product or
  project
• The normal solution is to have a MILESTONE with a
  significant penalty for being late.
• But.
• The Milestone causes people to be overly
  cautious. They estimate longer for the Project
  tasks (to be sure an not be late) or start work
  much sooner than needed (before the details are
  clear.

The result, is a slow process that still often
messed milestones!
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The Assembly Game

• Lets take six people and give each one two
  coins.
• Each person can flip one of his coins each day.
• To be prepared for the Assembly, each person
  needs to flip each coin until the has two heads.
• There are Six Days to get ready for the Assembly.

H
H
H
H
H
H
H
H

• Hum? What are the odds of getting a Head when
  flipping a fair coin?
• 50 on the first try!
• 75 within the first two tries.
• 87.5 within the first three tries.
• Hum? But I need to get two is Six tries. How
  does that work?
• Lets just try!

H
H
H
H
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The Assembly Game How to play (First Round).
Call out the Days, 1 through 6. Each of the six
players flip one coin each day. When a coin
results in a Head, shift to the next coin on the
next day. When two head are flipped, that person
has completed. At the end of Day 6, ask to see if
all the players are ready for the Assembly. If
all players are ready, record 100,000 profit If
all players are not ready, the Assembly cannot
take place. In this case, fire all the workers
and close the plant! Discuss if this is a fair
decision since most people were ready for the
Assembly. Why close the plant for just a few
poor performers?
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The Assembly Game How to play (Second Round).
For this Round, give everyone Seven Days. Count
Days 1 through 7. Repeat the same game. Evaluate
the assembly on Day 7 If all players are ready,
record 50,000 profit (less valuable when
late). If all players are not ready, the Assembly
cannot take place. In this case, Again, fire
all the workers and close the plant!
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The Assembly Game How to play (Third Round).
For this Round, give everyone 8 Days. Count Days
1 through 8. Repeat the same game. Evaluate the
assembly on Day 8 If all players are ready,
record 25,000 profit (less valuable when
late). If all players are not ready, the Assembly
cannot take place. In this case, Again, fire
all the workers and close the plant! Play Round
Three several time (trying to earn the 100,000
they could have if they had promised Six Day
Delivery. Most likely, they will have trouble
guaranteeing 8 days.
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The Assembly Game A CCPM Approach.
CCPM off-sets all but the Critical Chain. To
simulate this start five players on Day 1 and one
player on Day 4. This simulates giving a
Three-Day Feeder Buffer to the five players. The
Constraint also has Six days but starts on Day 4
and ends on Day 9. Assembly occurs on Day
9. This solution works well for CCPM. About 85
of the time, the system will complete by Day 9.
And, with a Project Buffer (protecting the late
Constraint) the system is good enough. Still, if
the system MUST Assemble, on Day 6, we need a
better approach. Lets try two more.
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The Assembly Game The Bench.
For this Round, Start all six players on Day 1
with the Goal to end on Day 6 just like the
first round. However, this time, you have a
Reserve Bench of two players. The Bench is made
up of experts, experts who can flip a coin and
get a head 80 of the time. However, for this
game, we will have just two ordinary players
sitting on the bench. Each has a single coin. On
Days 1, 2 and 3, the six players flip coins
normally. If any of the six players does not
have two heads by then (half way through), the
Bench steps in. On Days 4, 5 (and if necessary
6), one or two from the Bench flip coins along
side those players with the least heads. If the
Bench person or the regular player get a heads,
these heads count toward that regular players
count.
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The Assembly Game The Bench Results.
As a result of having just a little help (the
Bench is typically 20, but for this example,
its 33 extra capacity), the Bench allows the
Assembly to occur on Day 6 better than 90 of the
time. And, the Bench only helps about 30 of the
time. That means that the Experts, can spend 70
of their time thinking about how to make the
system work even better, how to improve the
processes and to mentor the regular players right
at the moment of their need. But if 90 is not
good enough? There is another approach.
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The Assembly Game The Full Bench Press.
The Bench is a good idea. We used only two
regular people as the Reserve Bench with pretty
good success. But, if you need certainty of
Assembly on Day 6 try the Full Bench Press. In
the Full Bench Press, there are the two Reserve
Bench experts who contribute as in the previous
solution. To add to the Bench, if any regular
player flips two heads (their regular work is
done) prior to the Assembly, they join the Bench
and can flip for with other people on the
following days as if they too were Reserve Bench
Experts. The Full Bench Press delivers Assembly
on Day 6 With Certainty. Keep Thinking! Dr Holt