Page 103 - The Handbook for Quality Management a Complete Guide to Operational Excellence

90 I n t e g r a t e d P l a n n i n g S t r a t e g i c P l a n n i n g 91

Assumptions:
1. The fast supplier is more expensive than other supplier
2. Buying from the fast supplier is always more costly
3. Purchase costs are significant
4. All cost savings are important

R1
Keep material P1
Don’t buy from
costs as low as the fast supplier
possible
Injection #1: Establish an
“emergency” stock level; Injection #2:
re-order from fast Emergency stock
O supplier when penetrated. is set to a level at
High due-date which it’s not
performance at likely to be (Conflict)
low cost Injection #3: Accept raw exhausted within
material cost increases as the fast
long as ∆T remains supplier’s QLT.
positive.

R2 P2
Ensure material Buy from the
availability fast supplier

Assumptions:
5. The regular supplier is unreliable
6. The regular supplier takes too long to deliver
7. We never know about peak demands in time to order
from the regular supplier
8. Purchase cost is less important than the cost
of a missed delivery
Figure 5.4 “Evaporating Cloud”—unreliable supplier (adapted from
Schragenheim and Dettmer, 2000).

“Drum-Buffer-Rope” Production Scheduling
Probably the best-known of the constraint management tools developed
by Goldratt is called “Drum-Buffer-Rope” (DBR). The origin of this name
dates back to the analogy Goldratt and Cox used in The Goal (Goldratt,
1986) to describe a system with dependencies and statistical fluctuations.
The analogy was a description of a Boy Scout hike. The drum was the pace
of the slowest Boy Scout, which dictated the pace for the others. The buffer
and rope were additional means to ensure all the Boy Scouts walked at
approximately the pace of the slowest boy.
Goldratt and Fox, in The Race (Goldratt and Fox, 1986), describe in
detail the manufacturing procedure that stems from the concepts of a
drum, buffer, and rope originally introduced through the Boy Scout hike.
The DBR method provides the means for synchronizing an entire manu-
facturing process with “weakest link” in the production chain. Figure 5.9
illustrates the DBR con cept.

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