A common question during and following pull planning sessions is “why can’t we just plan from the beginning of the work like we usually do?”
It’s an important question, and one that may not get answered well. Even when people accept that this process of reverse planning generates a richer discussion regarding the conditions of satisfaction needed to release work some believe that the same resulting plan would be realized if tasks were planned from the beginning of the phase, or in other words the team used push planning.
What the pull planning process does is help the team better understand how to best design the flow of work based on their shared understanding of available professionals, material supply chains, equipment logistics, and all the other factors informing work. It does this by framing the planning discussion in terms of satisfying team member needs instead of executing work because it is available. The need based approach forces a level of negotiation, small batch design and work balancing that push planning does not achieve.
Here’s where some teams fail to take full advantage of the pull planning process. It is very easy to simply “build the schedule backwards” without a healthy conversation about conditions of satisfaction, batch design or work balancing. A brief discussion of each of these pull planning concerns may be helpful.
Conditions of satisfaction: It is important that each of us are clear, not only to others but also to ourselves, about what we need before we begin and finish a task. In a pull planning session each person is explicit about the work completed, information needed and resources available for each of their tasks to be completed. This clarity minimizes incorrect assumptions and makes more visible possibilities for organizing work more efficiently. The pull planning process facilitates this discussion whereas a push planning process allows people to skip this important conversation.
Batch design: The clarity gained through the conditions of satisfaction conversation helps people on the team better see opportunities for organizing work flow in distinct and ideally small batches. A batch is a physical portion of the building in which a task will be completed before the crew performing that task moves to the next area. Some teams call these areas blocks or zones. For the structural phase a batch might be a steel sequence. In the envelope phase a batch may be a section of the building elevation. Batches in rough in and finish phases are usually sections of a floor. By designing the work to flow in batches teams can create the expectation that set of operations (concurrent by agreement) will have exclusive access to an area of the building. One important point regarding batch design – smaller batch sizes result in shorter project durations without an increase in manpower.
Work balancing: This addresses one of the most commonly missed benefits of the pull planning process. With batches designed, teams now need to look at each set of operations passing through the batches and adjust crew size and composition so that each set of operations requires the same amount of time in each batch. Accomplishing balanced flow results in the same set of professionals being fully engaged in the project at all times. Productivity is lost when people need to shift from one project to the next. Maintaining a consistent, reliable flow of work across all operations results in tremendous productivity gains, and ought to be one of the primary goals of a pull planning session.
Traditional first planner CPM scheduling, whether performed by a superintendent or scheduling guru in the office, not only relies on push planning but also pretends that the best project schedule can be determined by an expert seeking the truth about how to best organize the work. The Lean approach recognizes that the best project plan, structured to maximize flow, is achieved by the project team constructing knowledge about how to best organize the work. This constructing of knowledge is facilitated by a pull process that includes conversations about conditions of satisfaction, batch design and work balancing.