“How to Perform Effective CPM Scheduling” on Smartsheet, June 10, 2023
How to Create a CPM Schedule
Identify the Critical Path
Once you finish the critical path network diagram, your team (or software) will be able to identify the critical path: the set of activities whose timely completion is critical to the project’s schedule. Any delay in any critical path activity will delay the project’s completion.
Alan Zucker, Founding Principal at Project Management Essentials, LLC, says people are often confused about what the critical path means. “A lot of times, people think the critical path is the most important set of activities that are the most complicated,” he says. “(But) it’s really the series of activities that creates the length of the project schedule. And (the activities) can be really stupid, simple things. But they’re on that critical path for getting something complete. For example, getting approval from senior management to do something — you might have it estimated to complete in a day, but it might take a week, just because you can’t get someone to look at your email and say, ‘Yes, it’s approved.’ That activity still is on the project’s critical path because it can’t be completed until the approval happens.”
Update the Critical Path as Needed Throughout the Project
Timelines and other particulars change over the course of a project. It’s important to understand that those changes can alter your project’s critical path. Activities that weren’t previously on the critical path might be placed on it as the duration of other activities change.
“The CPM project schedule should be updated regularly, as the critical path can change while the project unfolds,” Zucker says.
CPM Best Practices
- Sequence, Connect, and Link All Activities: Every task in a project is dependent on the completion of a predecessor task. Each task has at least one other task that depends upon its completion, or a successor. Your team needs to examine all activities, sequence them correctly, and determine how each connects to others.“Make sure every task has a predecessor and successor. I’ve looked at hundreds, or probably thousands, of project schedules across my career, and most of them do not have predecessors and successors appropriately linked,” Zucker shares.A CPM schedule might require a task to be finished by August 30. But your team might not appropriately link that task to the required completion of a separate task — which won’t finish until September 10. “Since you did not make that explicit linkage, the schedule will no longer coincide with the reality of the situation,” Zucker adds. “The schedule needs to make that linkage.”
- Be Open to Rethinking How Activities Relate, and Rearrange: Ensuring linkages between all related activities might show the project taking longer than expected. Analyzing the linkages carefully can also allow your team to shorten the project. When you understand how certain activities might not have to wait on the completion of other activities, your project team can rearrange work or align resources differently.“The ultimate lesson is that, after you put together your initial project schedule, you need to look,” Zucker says. “You need to scrutinize it carefully, and ask yourself: ‘Does it conform to the realities of the situation? Are there things that we can do in terms of adjusting our predecessors and successors? Or are there other things that we can manipulate in order to get to a more reasonable date?’”
- Determine Realistic Timelines for Each Activity, and Don’t Force the Finishing Dates: Even if you can do some rearranging to shorten the project, you can’t simply force your team to finish an activity that needs other tasks to be completed first. If the team estimates an activity will take 10 days, you can’t expect the team with the same resources to finish the work in 4 days.“Don’t force the dates. If you’re forcing the dates, it means you’re not respecting the information that you’re being provided either in terms of the precedence of activities, or the estimated durations,” Zucker says.
- Review the Schedule With the People Who Will Do the Work: Project leaders need to review the schedule and the estimated time each activity will take with the team members who will be doing the work. “Review it with everybody, and ask the people actually doing the work if it’s correct and reasonable,” Zucker says.