Section H. Individual Steps Meet Takt, Global Process Does Not


H. Individual Steps Meet Takt, Global Process Does Not

Overview

If a process as a whole fails to meet the level of downstream demand, its Process Cycle Time is greater than Takt Time. For more detail see "TimeTakt Time" and "TimeGlobal Process Cycle Time" in Chapter 7, "Tools." It is entirely possible that the steps that make up the process are all cycling fast enough, but something falls down between the steps, thus causing the process as a whole to fail.

Examples

Virtually any process in any industry could exhibit this category of problem.

Measuring Performance

The measure of the process meeting Takt is the comparison of the Process Cycle Time against Takt. Process Cycle Time is calculated as

  • The average time between entities as they leave the process

  • Or equivalently the rate of processing entities

Tool Approach

First we must get an understanding of the current performance with respect to Process Cycle Time:

Focus should just be on measuring validitya sound operational definition and consistent measure of Process Cycle Time versus a detailed investigation of Gage R&R. For more detail see "MSAValidity" in Chapter 7.

The data is typically captured over a period of one week to one month (depending on process drumbeat) to get a reasonable estimate of Capability. For more detail see "CapabilityContinuous" in Chapter 7. Historical data will more than likely be sufficient for the purpose.

Use SIPOC at a 50,000-ft. level to understand supply stream linkage issues with external processes. If there are linkage issues, look to investigating supplier alignment (this could be a whole new project).


In order to enter this particular section, some work must have been done to identify the process steps and the relationship of their respective Cycles Times with Takt. More than likely, this was a Value Stream Map and Multi-Cycle Analysis. If those tools have already been applied, there is no need to repeat them.

Value Stream Map the process with a focus on the Primary Entity and particularly the delays it meets. Be sure to consider the whole process from customer-request trigger to customer acceptance. Identify actions to eliminate NVA steps and thus accelerate the Primary Entity.

Handoffs throughout the process can be the cause of significant delay. After the Value Stream Map is created, it should be relatively straightforward to add swim lanes to it to identify changes in responsibility and handoff problems.

Physical layout within the process can cause significant delays and sap capacity. Use the Spaghetti Map to identify excess travel distances or NVA flow issues.

Use the Handoff Map if there are apparent multiple revisits to one or more functions. This will identify excess load on a specific function(s) and thus show where effort should be focused.

At the very least, this map is a great visual tool to explain the issues to the process stakeholders.

If from the Swimlane Map and Handoff Map the process has obvious handoff problems, treat handoff "misses" as a process defect and seek out the key Xs that are driving them. In effect, this is a quality problem using the Y=f(X1, X2,..., Xn) roadmap as described in Section C in this chapter. Use accuracy of handoff as the Y in this case. Return to this point after the handoff issues are eliminated.


After handoffs issues are resolved, the process needs to be properly balanced as follows:

Apply a Multi-Cycle Analysis to the Swimlane Map to determine where the time is being spent in the process, along with an indication of variation in times. Usually it is the variability in step times that causes the problems.

A Load Chart for the process will show Takt Time versus Cycle Time. For more detail see "TimeTakt Time" and "TimeIndividual Step Cycle Time" in Chapter 7. All steps should be meeting the pace of demand (or otherwise we wouldn't have come to this particular section), but there might be opportunity to redistribute the workload and combine tasks to use fewer operators and hence have fewer handoffs.


At this point, the process should be performing to Takt and thus the Team can move to the Control tools described in Chapter 5.

If the Process Cycle Time is still considered to be too long, there are still a few options available to us:

  • Look to accelerating the pace of the individual value-added steps (go to "2: The Pace for a Single Process Step Is Too Slow" in Chapter 4).

  • Add additional resources to the process at the appropriate places (the load chart will help with this).

  • Hold inventory buffers at key locations throughout the process so entities don't have to traverse the whole process to be delivered (only works if the entities aren't unique).

  • Seek to anticipate demand from the Customer. (Is there an earlier trigger available to start the entity through the process?)

  • Examine options to keep the entity "vanilla" longer (not customized to a particular Customer). Is it possible to pre-prepare any parts of the entity so less work is required from the point of request?

  • If worse comes worst, it might be a case of considering a different process technology.





Lean Sigma(c) A Practitionaer's Guide
Lean Sigma: A Practitioners Guide
ISBN: 0132390787
EAN: 2147483647
Year: 2006
Pages: 138

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