Theory of Constraints Handbook - James Cox Iii [67]
Copyright © 2010 Realization Technologies, Inc.
TABLE 4-1 Examples of Critical Chain Results
The purpose of this chapter is to share how successful adopters have put Critical Chain concepts into practice and achieved durable results. It is based on experience from more than 200 enterprise-level3 implementations of Critical Chain. The range of these includes development of high-tech products; R&D and commercialization of pharmaceuticals; IT applications; design and manufacturing of complex equipment; shipbuilding; building, erection, and commissioning of physical infrastructure; and maintenance, repair, and overhaul of aircraft, submarines, and ships, as well as steel plants and oil refineries.
Starting with a quick recap of Critical Chain, this chapter discusses practical challenges in implementing it successfully. Then, a step-by-step process of implementation is described, followed by an overview of lessons learned over the last 12 years. Finally, before the summary, there are answers to the frequently asked questions that have not been covered in the rest of the chapter.
Recap of Critical Chain
Executing projects is like conducting an orchestra. Various inputs, resources, equipment, decisions and corrective actions have to be brought together at the right place and the right time throughout the life of a project.
Unfortunately, uncertainties get in the way. Tasks take longer, vendors don’t deliver on time, technical glitches happen, requirements change and so on. As these uncertainties unfold, even the most carefully prepared plans go awry. Execution priorities become unclear (which tasks to do first) and unsynchronized (every department, every person starts prioritizing their tasks differently). Consequently, a project is mostly waiting for something or the other (see Fig. 4-1). For example:
Waiting for resources because they have been assigned to other tasks.
Waiting for specifications, approvals, materials, etc., because the supporting resources that were supposed to supply or obtain them were busy elsewhere.
Waiting for issues to get resolved because experts are firefighting other issues.
Waiting for decisions because managers have too much on their plates.
Waiting for all feeding legs of the project to come together at integration points.
FIGURE 4-1 Time-traps in projects.
As these wait times accumulate, projects become late, firefighting starts, and resources are pulled in multiple directions at once. Priorities keep changing and people are forced to multitask.4 Managers’ ability to control outcomes is compromised and they often suffer a near-total loss of control. They cannot predict when a project will finish because holdups keep happening; and they don’t know how much capacity is really needed because no matter how many resources they provide, resources are still overloaded while projects continue to run late.
The net impact is that projects take much longer than they should, deliver less scope than originally planned, and are costlier than they need to be. In addition, resources are less productive than they might be.
Critical Chain solves all these problems by synchronizing task priorities within and across projects, and within and across departments. To synchronize, Critical Chain uses three precepts, or Rules:
1. Pipelining: Limit the number of projects in execution at one time.
2. Buffering: Discard local schedules and measurements, and use aggregate buffers5 to protect against uncertainties.
3. Buffer Management: Use buffer consumption to measure Execution, and to drive execution priorities and managerial interventions.
Rule 1 Pipelining: Limit the Number of Projects in Execution at One Time
When too many projects are in execution compared