Theory of Constraints Handbook - James Cox Iii [640]
With so many things going on at once, even when the flows are well defined, the system is unwieldy. There must be some order. The second Supply Chain Flow Concept (Goldratt, 2009) is to insert a practical mechanism that tells the operation when not to produce in order to prevent overproduction. Ordering the flows in logical sequence driven by an overall customer demand such as in Fig. 33-12 can reduce the chaos, speed reliable flow, and more effectively use internal resources. Ordering the flows in this manner means choking the release of work in each area in such a way that work begins only when the system is ready for it. This is done by pipelining projects in multi-project critical chain and using the rope mechanism in DBR or S-DBR for day-to-day production flows. In both of these cases (projects and production), buffers are used to manage the flows.
FIGURE 33-10 Buffered processes.
FIGURE 33-11 Multi-project chaos.
FIGURE 33-12 Sequenced process management.
Sequenced process management in Figure 33-12 connects the flow patterns so that everything moves at the fastest capability of the organization but not too fast or too much. There are different flows, such as the development flow, that run parallel to the production flow. These different flows have cross-flow connectors needed for the different groups to support each other. This process flow arrangement also implements the third Supply Chain Flow Concept (Goldratt, 2009): Local efficiencies are abolished. Work is started and processed at the rate of the systemic constraint, not at the rate of local, nonconstraint resources. There will be some protective capacity in most departments, and the overall flow of the organization will be maximized.
A Breakthrough Injection
With this background, we are ready to revisit the breakthrough injection: Everyone in the organization who has a significant impact on Throughput is measured by the same simple measure (that aligns all the actions of the organization with the goals of the organization). With all the interactions of so many different departments and units, each with its own goals, objectives, and measurements, how can we imagine a single injection, let alone call it a breakthrough injection?
The Definition of the Common Simple Measure
Having buffers for production flows and CCPM schedules for ideas projects in each unit provides the basis for measurement. We want to measure the extent to which a unit is not doing what it is supposed to be doing. We could measure the “not done” things several ways. We could count the number of things not done. We could estimate the value to the organization of the things not done. Moreover, we could measure the duration of time until the error was remediated. Each one of these measures is insufficient. If we only count the number of errors, we could reduce many tiny errors and not really deliver value to the organization. Making an error with a large negative impact on the organization is bad. However, if it only lasts a day or so, it is not nearly as bad as a lesser error that lasts months. Reducing the average time to remove an error may be helpful, but that focuses improvement efforts on the minor, easy-to-fix errors and leaves the big errors unresolved. What we really need is a composite measure that considers both of these factors. Here we can benefit from one of the measures used in TOC Supply Chain Management: Throughput Dollar Days (TDD).8 TDD takes into account both the amount of Throughput that is delayed and the length of time it is delayed. TDD is the Throughput Value (the contribution to the organization represented by the final sale less any truly variable costs), which is assigned to product or process flow, times the number of days late added together for all late tasks (lateness is defined as not delivering the required quantity or quality on the mutually agreed upon date). TDD is a measure of reliability. It measures